Tag Archives: AIDS

Study highlights two strategies used by Salmonella to escape the human body’s defenses

Like thieves that constantly look for ways to evade capture, Salmonella enterica, a disease-causing bacterium, uses various tactics to escape the human body’s defense mechanisms. In a new study, researchers from the Department of Microbiology and Cell Biology (MCB), IISc, highlight two such strategies that the bacterium uses to protect itself, both driven by the same protein.

When Salmonella enters the human body, each bacterial cell resides within a bubble-like structure known as Salmonella-containing vacuole (SCV). In response to the bacterial infection, the immune cells in our body produce reactive oxygen species (ROS) and reactive nitrogen species (RNS), along with pathways triggered to break down these SCVs and fuse them with cellular bodies called lysosomes or autophagosomes, which destroy the bacteria. However, these bacteria have developed robust mechanisms to maintain vacuolar integrity, which is crucial for their survival. For example, when a bacterial cell divides, the vacuole surrounding it also divides, enabling every new bacterial cell to be ensconced in a vacuole. This also ensures that more vacuoles are present than the number of lysosomes which can digest them.

In the study published in Microbes and Infection, the IISc team deduced that a critical protein produced by Salmonella, known as SopB, prevents both the fusion of SCV with lysosomes as well as the production of lysosomes, in a two-pronged approach to protect the bacterium. “[This] gives the upper hand to bacteria to survive inside macrophages or other host cells,” explains Ritika Chatterjee, former PhD student in MCB and first author of the study. The experiments were carried out on immune cell lines and immune cells extracted from mice models.

SopB acts as a phosphatase – it aids in removing phosphate groups from phosphoinositide, a type of membrane lipid. SopB helps Salmonella change the dynamics of the vacuole – specifically it alters the type of inositol phosphates in the vacuole membrane – which prevents the vacuole’s fusion with lysosomes.

A previous study from the same team had reported that the number of lysosomes produced by the host cells decreases upon infection with Salmonella. The researchers also found that mutant bacteria that were unable to produce SopB were also unable to reduce host lysosome numbers. Therefore, they decided to look more closely at the role that SopB was playing in the production of lysosomes, using advanced imaging techniques.

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What they found was that SopB prevents the translocation of a critical molecule called Transcription Factor EB (TFEB) from the cytoplasm of the host cell into the nucleus. This translocation is vital because TFEB acts as a master regulator of lysosome production.

This is the first time we deciphered that SopB can work in a dual manner – it changes the phosphoinositide dynamics of SCV and affects TFEB’s translocation into the nucleus. While other groups have already reported the function of SopB in mediating invasion in epithelial cells, the novelty of our study lies in identification of the function of SopB in inhibiting the vacuolar fusion with existing autophagosomes/lysosomes, and the second mechanism, which provides Salmonella with a survival advantage by increasing the ratio of SCV to lysosomes.”

Dipshikha Chakravortty, Professor at MCB and corresponding author of the study

The researchers suggest that using small molecule inhibitors against SopB or activators of TFEB can help counter Salmonella infection.

In subsequent studies, the team plans to explore the role of another host protein called Syntaxin-17 whose levels also reduce during Salmonella infection. “How do the SCVs reduce the levels of Syntaxin-17? Do they exchange it with some other molecules, or do the bacteria degrade it? We [plan to] look into it next,” says Chakravortty.

Source:
Journal reference:

Chatterjee, R., et al. (2023) Deceiving The Big Eaters: Salmonella Typhimurium SopB subverts host cell Xenophagy in macrophages via dual mechanisms. Microbes and Infection. doi.org/10.1016/j.micinf.2023.105128.

First-in-human nanoparticle HIV vaccine induces broad and publicly targeted helper T cell responses

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Researchers from Fred Hutchinson Cancer Center in Seattle, Scripps Research in La Jolla, California, IAVI and other collaborating institutions have characterized robust T-cell responses in volunteers participating in the IAVI G001 Phase 1 clinical trial to test the safety and immune response of a self-assembling nanoparticle HIV vaccine.

Their work, published in Science Translational Medicine, signals a major step toward development of a vaccine approach to end the HIV/AIDS epidemic worldwide. The antigen used in this study was jointly developed by IAVI and Scripps Research and has been shown in previous analyses to stimulate VRC01-class B cells, an immune response considered promising enough for boosting in further studies.

We were quite impressed that this vaccine candidate produced such a vigorous T-cell response in almost all trial participants who received the vaccine. These results highlight the potential of this HIV-1 nanoparticle vaccine approach to induce the critical T-cell help needed for maturing antibodies toward the pathway of broadly neutralizing against HIV.”

Julie McElrath, MD, PhD, senior vice president and director of Fred Hutch’s Vaccine and Infectious Disease Division and co-senior author of the study

However, she added, this is the first step, and heterologous booster vaccines will still be needed to eventually produce VRC01-class broadly neutralizing antibodies, which in previous studies have demonstrated the ability to neutralize approximately 90% of HIV strains.

“We showed previously that this vaccine induced the desired B-cell responses from HIV broadly neutralizing antibody precursors. Here we demonstrated strong CD4 T-cell responses, and we went beyond what is normally done by drilling down to identify the T cell epitopes and found several broadly immunogenic epitopes that might be useful for developing boosters and for other vaccines,” William Schief, PhD, executive director of vaccine design for IAVI’s Neutralizing Antibody Center at Scripps Research and professor, Department of Immunology and Microbiology, at Scripps Research, who is co-senior author of the study.

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The trial is a phase 1, randomized, double-blind and placebo-controlled study to evaluate the safety and effectiveness of a nanoparticle HIV vaccine in healthy adult volunteers without HIV. It was comprised of two groups with 18 vaccine and six placebo recipients per group, with 48 total enrollees. Participants were given two doses of the vaccine or placebo eight weeks apart.

McElrath acknowledged the groundbreaking work of her lab team, the biostatistical team and Fred Hutch’s Vaccine Trials Unit for their invaluable contributions to the study. The Vaccine Trials Unit conducts multiple vaccine trials and was one of only two sites for this study.

Findings from the study include:

  • Vaccine-specific CD4 T cells were induced in almost all vaccine recipients.
  • Lymph node GC T follicular helper cells increased after vaccination compared to placebo.
  • Lumazine synthase protein, needed for self-assembly of the particle, also induced T-cell responses that can provide additional help to ultimately enhance efficacy in a sequential vaccine strategy.
  • Vaccine-specific CD4 T cells were polyfunctional and had diverse phenotypes.
  • LumSyn-specific CD8 T cells were highly polyfunctional and had a predominantly effector memory phenotype.
  • CD4 T-cell responses were driven by immunodominant epitopes with diverse and promiscuous HLA restriction.
  • CD8 T-cell responses to LumSyn were driven by HLA-A*02-restricted immunodominant epitopes B- and T-cell responses correlated within but not between LN and peripheral blood compartments.

This study was funded by the Bill & Melinda Gates Foundation Collaboration for AIDS Vaccine Discovery; IAVI Neutralizing Antibody Center; National Institute of Allergy and Infectious Diseases; and Ragon Institute of MGH, MIT and Harvard.

Study authors WRS and SM are inventors on a patent filed by Scripps and IAVI on the eOD-GT8 monomer and 60-mer immunogens (patent number 11248027, “Engineered outer domain (eOD) of HIV gp 120 and mutants thereof”). WRS, KWC and MJM are inventors on patents filed by Scripps, IAVI and Fred Hutch on immunodominant peptides from LumSyn (Title: Immunogenic compositions; filing no. 63127975).

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Source:
Journal reference:

Cohen, K. W., et al. (2023) A first-in-human germline-targeting HIV nanoparticle vaccine induced broad and publicly targeted helper T cell responses. Science Translational Medicine. doi.org/10.1126/scitranslmed.adf3309.

Novel gene-editing strategy harnesses an unusual protective ability to eliminate HIV-1 infection

Genetic alterations that give rise to a rare, fatal disorder known as MOGS-CDG paradoxically also protect cells against infection by viruses. Now, scientists at the Lewis Katz School of Medicine at Temple University have harnessed this unusual protective ability in a novel gene-editing strategy aimed at eliminating HIV-1 infection with no adverse effects on cell mortality.

The new approach, described online April 28 in the journal Molecular Therapy – Nucleic Acids, is based on a combination of two gene-editing constructs, one that targets HIV-1 DNA and one that targets a gene called MOGS – defects in which cause MOGS-CDG. In cells from persons infected with HIV-1, the Temple researchers show that disrupting the virus’s DNA while also deliberately altering MOGS blocks the production of infectious HIV-1 particles. The discovery opens up new avenues in the development of a cure for HIV/AIDS.

Proper MOGS function is essential for glycosylation, a process by which some cellular proteins synthesized in the body are modified to make them stable and functional. Glycosylation, however, is leveraged by certain kinds of infectious viruses. In particular, viruses like HIV, influenza, SARS-CoV-2, and hepatitis C, which are surrounded by a viral envelope, rely on glycosylated proteins to enter host cells.

In the new study, lead investigators Kamel Khalili, PhD, Laura H. Carnell Professor and Chair of the Department of Microbiology, Immunology, and Inflammation, Director of the Center for Neurovirology and Gene Editing, and Director of the Comprehensive NeuroAIDS Center at the Lewis Katz School of Medicine, and Rafal Kaminski, PhD, Assistant Professor at the Center for Neurovirology and Gene Editing at the Lewis Katz School of Medicine designed a genetic approach to exclusively turn on CRISPR to impede MOGS gene expression through DNA editing within immune cells that harbor replication competent, HIV-1. Their novel approach is expected to avoid any impact on the health of uninfected cells that retain normal MOGS gene function. Stimulation of the apparatus in HIV-1 infected cells disrupted the glycan structure of the HIV-1 envelope protein, culminating in the production of non-infectious virus particles.

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“This approach is conceptually very interesting,” said Dr. Khalili, who is also senior investigator on the new study. “By mitigating the ability of the virus to enter cells, which requires glycosylation, MOGS may offer another target, in addition to the integrated viral DNA for developing the next generation of CRISPR gene-editing technology for HIV elimination.”

Dr. Kaminski, Dr. Khalili, and Tricia H. Burdo, PhD, Professor and Vice Chair in the Department of Microbiology, Immunology, and Inflammation and the Center for Neurovirology and Gene Editing at Temple and an expert in the use of non-human primate models for HIV-1, have been working together to further assess the efficacy and safety of CRISPR-MOGS strategy in preclinical studies. In previous work, the team demonstrated that CRISPR-based technology can successfully remove viral DNA from the cells of infected non-human primates.

Other researchers who contributed to the study include Hong Liu, Chen Chen, Shuren Liao, and Shohreh Amini, Department of Microbiology, Immunology, and Inflammation, Center for Neurovirology and Gene Editing, Lewis Katz School of Medicine at Temple University; Danielle K. Sohaii, Conrad R.Y. Cruz, and Catherine M. Bollard, Center for Cancer and Immunology Research, Children’s National Health System, The George Washington University; Thomas J. Cradick and Jennifer Gordon, Excision Biotherapeutics, San Francisco, CA; Anand Mehta, Stephane Grauzam, and James Dressman, Department of Cell and Molecular Pharmacology, Medical University of South Carolina; and Carlos Barrero and Magda Florez, Department of Pharmaceutical Sciences, School of Pharmacy, Temple University.

The research was supported in part by grants from the National Institutes of Health and the W.W. Smith Charitable Trust.

Source:
Journal reference:

Liu, H., et al. (2023) Strategic Self-Limiting Production of Infectious HIV Particles by CRISPR in Permissive Cells. Molecular Therapy — Nucleic Acids. doi.org/10.1016/j.omtn.2023.04.027.

Swiss researchers identify plastic-degrading microbial strains in the Alps and Arctic region

Finding, cultivating, and bioengineering organisms that can digest plastic not only aids in the removal of pollution, but is now also big business. Several microorganisms that can do this have already been found, but when their enzymes that make this possible are applied at an industrial scale, they typically only work at temperatures above 30 °C. The heating required means that industrial applications remain costly to date, and aren’t carbon-neutral. But there is a possible solution to this problem: finding specialist cold-adapted microbes whose enzymes work at lower temperatures.

Scientists from the Swiss Federal Institute WSL knew where to look for such micro-organisms: at high altitudes in the Alps of their country, or in the polar regions. Their findings are published in Frontiers in Microbiology.

“Here we show that novel microbial taxa obtained from the ‘plastisphere’ of alpine and arctic soils were able to break down biodegradable plastics at 15 °C,” said first author Dr Joel Rüthi, currently a guest scientist at WSL. “These organisms could help to reduce the costs and environmental burden of an enzymatic recycling process for plastic.”

Rüthi and colleagues sampled 19 strains of bacteria and 15 of fungi growing on free-lying or intentionally buried plastic (kept in the ground for one year) in Greenland, Svalbard, and Switzerland. Most of the plastic litter from Svalbard had been collected during the Swiss Arctic Project 2018, where students did fieldwork to witness the effects of climate change at first hand. The soil from Switzerland had been collected on the summit of the Muot da Barba Peider (2,979 m) and in the valley Val Lavirun, both in the canton Graubünden.

The scientists let the isolated microbes grow as single-strain cultures in the laboratory in darkness and at 15 °C and used molecular techniques to identify them. The results showed that the bacterial strains belonged to 13 genera in the phyla Actinobacteria and Proteobacteria, and the fungi to 10 genera in the phyla Ascomycota and Mucoromycota.

Surprising results

They then used a suite of assays to screen each strain for its ability to digest sterile samples of non-biodegradable polyethylene (PE) and the biodegradable polyester-polyurethane (PUR) as well as two commercially available biodegradable mixtures of polybutylene adipate terephthalate (PBAT) and polylactic acid (PLA).

None of the strains were able to digest PE, even after 126 days of incubation on these plastics. But 19 (56%) of strains, including 11 fungi and eight bacteria, were able to digest PUR at 15 °C, while 14 fungi and three bacteria were able to digest the plastic mixtures of PBAT and PLA. Nuclear Magnetic Resonance (NMR) and a fluorescence-based assay confirmed that these strains were able to chop up the PBAT and PLA polymers into smaller molecules.

“It was very surprising to us that we found that a large fraction of the tested strains was able to degrade at least one of the tested plastics,” said Rüthi.

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The best performers were two uncharacterized fungal species in the genera Neodevriesia and Lachnellula: these were able to digest all of the tested plastics except PE. The results also showed that the ability to digest plastic depended on the culture medium for most strains, with each strain reacting differently to each of four media tested.

Side-effect of ability to digest plant polymers

How did the ability to digest plastic evolve? Since plastics have only been around since the 1950s, the ability to degrade plastic almost certainly wasn’t a trait originally targeted by natural selection.

Microbes have been shown to produce a wide variety of polymer-degrading enzymes involved in the break-down of plant cell walls. In particular, plant-pathogenic fungi are often reported to biodegrade polyesters, because of their ability to produce cutinases which target plastic polymers due their resemblance to the plant polymer cutin.”

Dr Beat Frey, Last Author, Senior Scientist and Group Leader, WSL

Challenges remain

Since Rüthi et al. only tested for digestion at 15 °C, they don’t yet know the optimum temperature at which the enzymes of the successful strains work.

“But we know that most of the tested strains can grow well between 4 °C and 20 °C with an optimum at around 15 °C,” said Frey.

“The next big challenge will be to identify the plastic-degrading enzymes produced by the microbial strains and to optimize the process to obtain large amounts of proteins. In addition, further modification of the enzymes might be needed to optimize properties such as protein stability”.

Source:
Journal reference:

de Freitas, A. S. et al. (2023). Amazonian dark earths enhance the establishment of tree species in forest ecological restoration. Frontiers in Soil Science. doi.org/10.3389/fsoil.2023.1161627.

Challenging the FDA’s authority isn’t new – the agency’s history shows what’s at stake when drug regulation is in limbo

Political pressure is nothing new for the U.S. Food and Drug Administration. The agency has frequently come under fire for its drug approval decisions, but attacks on its decision-making process and science itself have increased during the COVID-19 pandemic.

Recent challenges to the FDA’s authority have emerged in the context of reproductive rights.

On Nov. 18, 2022, a group of anti-abortion doctors and medical groups filed a lawsuit against the FDA, challenging its approval from more than 20 years ago of mifepristone, a drug taken in combination with another medication, misoprostol, to treat miscarriages and used to induce more than 50% of abortions in early-stage pregnancies in the U.S.

It is widely believed that the plaintiffs filed the lawsuit in the Northern District of Texas so District Judge Matthew J. Kacsmaryk, a well-known abortion opponent, could oversee the litigation. While Kacsmaryk did issue a preliminary injunction ruling that the FDA lacked the authority to approve mifepristone, an appeal partially reversed the decision and the Supreme Court stayed Kacsmaryk’s order. The case now sits at the 5th U.S. Circuit Court of Appeals and will likely return to the Supreme Court.

The FDA is the government’s oldest consumer protection agency. The effects of this lawsuit could reach far beyond mifepristone – undermining the agency’s authority could threaten its entire drug approval process and change access to commonly used drugs, ranging from amoxycillin and Ambien to prednisone and Paxlovid.

I am a legal scholar whose research focuses in part on the law and ethics of the FDA’s drug approval process. Examining the FDA’s history reveals the unprecedented nature of the current challenges to the agency’s authority.

In its early years, the FDA focused primarily on balancing the competing goals of consumer safety with access to experimental treatments. The priority was strengthening consumer protection to prevent tragedy from recurring.

For instance, at the turn of the 20th century, Congress passed the Biologics Control Act of 1902, providing the federal government the authority to regulate vaccines. This law was introduced after 13 children died from inadvertently contaminated diphtheria antitoxin, which was made from the blood of a horse infected with tetanus.

A few years later, after investigative journalists publicized the unsanitary conditions and food-handling practices in meatpacking plants, Congress passed the Pure Food and Drug Act of 1906, which prohibited the marketing and sale of misbranded and contaminated foods, drinks and drugs.

Similarly, in 1937, approximately 71 adults and 34 children died from ingesting S.E. Massengill’s antibacterial elixir, which contained a poisonous raspberry flavoring added to sweeten the taste. In response, Congress passed the Federal Food, Drug and Cosmetic Act of 1938, requiring manufacturers to show that drugs are safe before they go on the market. This act marked the beginning of modern drug regulations and the birth of the FDA as a regulatory agency.

Then, in 1962, Dr. Frances Oldham Kelsey, a pharmacologist, physician and medical officer working at the FDA, refused to approve thalidomide, a drug marketed in Europe, Canada, Japan and other countries to alleviate morning sickness in pregnant women but later found to cause severe birth defects. Shocking revelations of children born without limbs or suffering from other debilitating conditions motivated Congress to pass the Kefauver-Harris Drug Amendments of 1962, which ushered in a more cautious approach to the drug approval process.

During the 1970s, questions about the limits of safety versus an individual’s right to access arose when cancer patients who wanted access to an unapproved drug derived from apricots, Laetrile, sued the FDA. The agency had blocked the drug’s shipment and sale because it was not approved for use in the U.S. At that time, the Supreme Court upheld the FDA’s protective authority, holding that an unproven therapy is unsafe for all patients, including the terminally ill.

The 1980s, however, marks the FDA’s shift toward increasing access following reports of an emerging disease – AIDS – which primarily affected gay men. In the first nine years of the AIDS epidemic, over 100,000 Americans died. AIDS patients and their advocates became vocal critics of the FDA, arguing that the agency was too paternalistic and restrictive following events like the thalidomide scare.

After massive protests, Dr. Anthony Fauci, then director of the National Institute of Allergy and Infectious Diseases, proposed a parallel track program allowing eligible patients access to unapproved experimental treatments. This, along with other existing FDA mechanisms, helped lay the path for other alternative approval pathways, such as Emergency Use Authorization, which played a large role in permitting use of vaccines and medications pending full FDA approval during the COVID-19 pandemic.

Despite the FDA’s shift toward increased access, the political right has in recent years argued that the agency remains too bureaucratic and paternalistic and should be deregulated – an argument seemingly contrary to the reasoning underlying Kacsmaryk’s recent order that the FDA did not sufficiently evaluate the safety of mifepristone in its approval.

Mifepristone, which has overwhelming data supporting its safety, could remain available to some people in some states regardless of the outcome of this lawsuit. While the FDA approves drugs for consumer use, it does not regulate the general practice of medicine. Doctors can prescribe FDA-approved drugs off-label, meaning they could prescribe a drug with a different dose, in a different way or for a different use than what the FDA has approved it for.

The mifepristone case has broad implications for the FDA’s future and could have devastating effects on health in the U.S. Due in part to FDA involvement, public health interventions have led to a 62% increase in life expectancy in the 20th century. These include vaccines and medications for childhood illnesses and infectious diseases such as HIV, increased regulation of tobacco, and over-the-counter Narcan to combat the opioid crisis, among others.

The FDA needs to be able to use its scientific expertise to make data-driven decisions that balance safety and access, without the ability of a single judge to potentially gut the system. The agency’s history is an important reminder of the need for strong administrative agencies and ongoing vigilance to protect everyone’s health.


Christine Coughlin

The Conversation

New approach targets norovirus, world’s leading cause of foodborne infection

Every year, norovirus causes hundreds of millions of cases of food poisoning — and the deaths of at least 50,000 children — yet there exists no real way to control it. The virus has proven exceptionally difficult to study in the lab, and scientists have struggled to develop effective vaccines and drugs.

A new study at Washington University School of Medicine in St. Louis describes a creative way to make a vaccine against norovirus by piggybacking on the highly effective vaccines for rotavirus, an unrelated virus that also causes diarrhea.

The researchers created an experimental rotavirus-norovirus combo vaccine by adding a key protein from norovirus to a harmless strain of rotavirus. Mice that received the experimental vaccine produced neutralizing antibodies against both rotavirus and norovirus. The study, available online in Proceedings of the National Academy of Sciences, outlines an innovative approach to preventing one of the most common and intractable viral infections.

“Pretty much everyone has had norovirus at some point,” said senior author Siyuan Ding, PhD, an assistant professor of molecular microbiology. “You go out to eat, and the next thing you know you’re vomiting and having diarrhea. You will recover, but it’s going to be a rough three days or so. For kids in the developing world who don’t have access to clean water, though, it can be deadly. The rotavirus vaccines work really well, and there are already global distribution systems set up for them, so based on that, we saw an opportunity to finally make some headway against norovirus.”

Before the first rotavirus vaccines were rolled out in 2006, half a million children around the world died every year of diarrhea caused by rotavirus infection. Now, the number is estimated to be about 200,000 — still high but a huge improvement. Four rotavirus vaccines are in use around the world. All are live-virus vaccines, meaning they are based on weakened forms of rotavirus capable of triggering an immune response but not of making people sick.

Human norovirus, on the other hand, has stymied scientific investigation for decades. It doesn’t infect mice or rats or any other ordinary lab animals, so the kinds of experiments that led to the development of rotavirus vaccines have been impossible to replicate with norovirus.

Ding and colleagues — including first author Takahiro Kawagishi, PhD, a staff scientist in Ding’s lab, and co-corresponding author Harry B. Greenberg, MD, a professor emeritus of medicine at Stanford University — came up with the idea of using rotavirus to bypass the technical difficulties of working with norovirus. They worked with a laboratory strain of rotavirus as a stand-in for one of the approved rotavirus vaccines, which are proprietary.

The researchers inserted the gene for the protein that forms the outer surface of human norovirus into the genome of the rotavirus lab strain. Then, they administered the modified rotavirus to immunocompromised infant mice by mouth, the same way rotavirus vaccines are given to children. They took blood and fecal samples four, six and eight weeks later. Nine weeks after the initial immunization, the researchers gave the mice a booster by injection and took samples again a week later.

A strong antibody response was evident in the blood of nine of 11 mice tested, and in the intestines of all 11 mice. Even better, some of the antibodies from the blood and the intestines were able to neutralize both viruses in human “mini-gut” cultures in a dish. Such cultures, also known as organoids, are grown from human stem cells and replicate the surface of the human gut.

“Traditionally, vaccine studies have focused on the antibody response in the blood, because we understand that part of the immune response the best,” Ding said. “But norovirus and rotavirus are gut viruses, so antibodies in the blood are less important than the ones in the intestines in terms of fighting off these viruses. The fact that we saw a strong antibody response in the intestines is a good sign.”

The next step is to show that animals immunized with the experimental vaccine are less likely to get sick or die from norovirus. Ding has such experiments underway.

The power of this study is that it outlines a novel approach that could accelerate vaccine development for a variety of troublesome organisms that cause diarrhea, especially in resource-limited countries where many of these infections occur.

“There are a lot of intestinal pathogens out there for which we don’t have good treatments or vaccines,” Ding said. “In principle, we could put a gene from any organism that infects the intestinal tract into the rotavirus vaccine to create a bivalent vaccine. We’d have to find the right targets to produce a good immune response, of course, but the principle is simple.

“As basic scientists, we rarely get the chance to actually move something forward into the clinic,” Ding continued. “We study what the virus does and how the host responds at a basic level. This is a rare opportunity for our work to affect human health directly and make people’s lives better.”

  • Takahiro Kawagishi, Liliana Sánchez-Tacuba, Ningguo Feng and Harry B. Greenberg et al. Mucosal and systemic neutralizing antibodies to norovirus induced in infant mice orally inoculated with recombinant rotaviruses. PNAS, 2023 DOI: 10.1073/pnas.22144211
  • Washington University School of Medicine

    Monocytes may be a stable reservoir of HIV in patients taking antiretroviral therapy

    To develop treatments that may one day entirely rid the body of HIV infection, scientists have long sought to identify all of the places that the virus can hide its genetic code. Now, in a study using blood samples from men and women with HIV on long-term suppressive therapy, a team led by Johns Hopkins Medicine scientists reports new evidence that one such stable reservoir of HIV genomes can be found in circulating white blood cells called monocytes.

    Monocytes are short-lived circulating immune cells that are a precursor to macrophages, immune cells able to engulf and destroy viruses, bacteria and other cells foreign to the host.

    In the current research, published March 27 in Nature Microbiology, the scientists found evidence that blood samples from people with HIV undergoing long term, standard antiretroviral therapy contained monocytes that harbor stable HIV DNA capable of infecting neighboring cells.

    The scientists say the findings may provide a new direction for efforts to improve therapies and eventually cure HIV, which affects more than 34 million people worldwide, according to the World Health Organization. Current antiretroviral drugs can successfully suppress HIV to nearly undetectable levels, but have not resulted in total eradication of the virus.

    We don’t know how critical these monocytes and macrophages are to eradication of HIV, but our results suggest we should continue research efforts to understand their role in this disease.”

    Janice Clements, Ph.D., professor of molecular and comparative pathobiology, Johns Hopkins University School of Medicine

    Scientists have long known that HIV stashes its genome most often in a type of immune cell called a CD4+ T-cell. These hiding places are known as reservoirs.

    “To eradicate HIV, the goal is to find biomarkers for cells that harbor the HIV genome and eliminate those cells,” says Rebecca Veenhuis, Ph.D., assistant professor of molecular and comparative pathobiology at the Johns Hopkins University School of Medicine.

    To further study the role of monocytes and macrophages in circulating blood as HIV reservoirs, the Johns Hopkins-led team of scientists obtained blood samples between 2018 and 2022 from 10 men with HIV, all of them taking long-term, standard antiretroviral medications.

    The researchers extracted blood cells from the samples and grew the cells in the laboratory. Typically, monocytes transform very quickly -; within about three days -; into macrophages, producing monocyte-derived macrophages.

    All 10 men had detectable HIV DNA in their monocytes-turned-macrophages, but at levels 10 times lower than those found in the men’s CD4+ T cells, the well-established HIV reservoir.

    For the next phase of the research, to determine if HIV genomes were present in monocytes prior to macrophage differentiation, the team used an experimental assay to detect intact HIV genomes in monocytes. The assay was based on one that fellow Johns Hopkins scientist Robert Siliciano, M.D., Ph.D., developed in 2019 to detect the HIV genome in CD4+ T cells.

    The scientists, including research associate Celina Abreu, Ph.D., used the assay on blood samples taken from another group of 30 people (eight men from the first group and 22 female participants) with HIV, also treated with standard antiretroviral therapy. The researchers found HIV DNA in the CD4+ T cells and in monocytes of all 30 participants.

    The scientists were also able to isolate HIV produced by infected monocytes from half of the research participants. The virus extracted from these cells was able to infect CD4+ T cells.

    Three of the participants had their blood examined several times over the four-year study period, and each time, the scientists found HIV DNA and infectious virus produced by their monocyte-derived macrophages. “These results suggest that monocytes may be a stable reservoir of HIV,” says Clements.

    In further research, the Johns Hopkins research team plans to pinpoint the subset of monocytes found to harbor HIV DNA and the source of these infected cells.

    Source:
    Journal reference:

    Veenhuis, R. T., et al. (2023). Monocyte-derived macrophages contain persistent latent HIV reservoirs. Nature Microbiology. doi.org/10.1038/s41564-023-01349-3.

    Low-cost, universal oral COVID-19 vaccine prevents severe respiratory illness in hamsters

    A UCLA-led team has developed an inexpensive, universal oral COVID-19 vaccine that prevented severe respiratory illness and weight loss when tested in hamsters, which are naturally susceptible to SARS-CoV-2. It proved as effective as vaccines administered by injection or intranasally in the research.

    If ultimately approved for human use, it could be a weapon against all COVID-19 variants and boost uptake, particularly in low- and middle-income countries, and among those with an aversion to needles.

    The study is published in the peer-reviewed journal Microbiology Spectrum.

    The oral vaccine is based primarily on the nucleocapsid protein, which is the most abundantly expressed of the virus’s four major structural proteins and evolves at a much slower rate than the frequently mutating spike protein. The vaccine utilizes a highly weakened bacterium to produce the nucleocapsid protein in infected cells as well as the membrane protein, which is another highly abundant viral structural protein.

    Being a universal vaccine based primarily upon the nucleocapsid protein, the vaccine is resistant to the incessant mutations of the SARS-CoV-2 spike protein upon which virtually all current vaccines are based. As a result, current vaccines rapidly become obsolete, requiring that they repeatedly be re-engineered. Hence, our vaccine should protect against new and emerging variants of SARS-CoV-2.”

    Dr. Marcus Horwitz, senior author, distinguished professor of medicine in the Division of Infectious Diseases and of microbiology, immunology and molecular genetics at the David Geffen School of Medicine at UCLA

    Oral delivery also makes it easier to distribute the vaccine in resource poor areas of the world by eliminating the need for needles, syringes, and trained personnel to deliver injectable vaccines, he added. “An oral vaccine may also be attractive to many people with vaccine hesitancy on account of fear of needles.”

    The researchers noted that while it worked exceptionally well in preventing severe respiratory illness, it did not provide full protection against high viral loads in the hamsters. Also, they did not test it against the Omicron strain, which contains a nearly identical nucleocapsid protein, because of this strain’s low virulence in the golden Syrian hamsters they used.

    But the vaccine, they write, “is efficacious when administered via the oral route against COVID-19-like disease in a highly demanding animal model. This conveniently administered, easily manufactured, inexpensive, and readily stored and transported vaccine could play a major role in ending the COVID-19 pandemic by protecting immunized individuals from serious disease from current and future strains of SARS-CoV-2.”

    The next step in the process will be to manufacture the vaccine for oral administration via an acid-resistant enteric capsule that will allow the vaccine to be safely released in the small intestine, Horwitz said. It will then be tested for safety, immunogenicity, and efficacy in humans.

    “We also plan to expand the vaccine to protect against infections caused by other types of potentially pandemic coronaviruses such as the virus that causes Middle Eastern Respiratory Syndrome (MERS),” he added.

    Additional authors are Qingmei Jia and Saša Masleša-Galić of UCLA; Helle Bielefeldt-Ohmann of the University of Queensland, Australia; and Rachel Maison, Airn Hartwig, and Richard Bowen of Colorado State University.

    This study was supported by a Corona Virus Seed grant from the UCLA AIDS Institute and Charity Treks and by the National Institutes of Health (AI141390).

    Source:
    Journal reference:

    Jia, Q., et al. (2023). Oral Administration of Universal Bacterium-Vectored Nucleocapsid-Expressing COVID-19 Vaccine is Efficacious in Hamsters. Microbiology Spectrum. doi.org/10.1128/spectrum.05035-22.

    Antibiotics can destroy many types of bacteria, but increasingly, bacterial pathogens are gaining resistance to many commonly used …

    Antibiotics can destroy many types of bacteria, but increasingly, bacterial pathogens are gaining resistance to many commonly used types. As the threat of antibiotic resistance looms large, researchers have sought to find new antibiotics and other ways to destroy dangerous bacteria. But new antibiotics can be extremely difficult to identify and test. Bacteriophages, which are viruses that only infect bacterial cells, might offer an alternative. Bacteriophages (phages) were studied many years ago, before the development of antibiotic drugs, and they could help us once again.

    Image credit: Pixabay

    If we are going to use bacteriophages in the clinic to treat humans, we should understand how they work, and how bacteria can also become resistant to them. Microbes are in an arms race with each other, so while phages can infect bacteria, some bacterial cells have found ways to thwart the effects of those phages. New research reported in Nature Microbiology has shown that when certain bacteria carry a specific genetic mutation, phages don’t work against them anymore.

    In this study, the researchers used a new technique so they could actually see a phage attacking bacteria. Mycobacteriophages infect Mycobacterial species, including the pathogens Mycobacterium tuberculosis and Mycobacterium abscessus, as well as the harmless Mycobacterium smegmatis, which was used in this research.

    The scientists determined that Mycobacterial gene called lsr2 is essential for many mycobacteriophages to successfully infect Mycobacteria. Mycobacteria that carry a mutation that renders the Lsr2 protein non-functional are resistant to these phages.

    Normally, Lsr2 aids in DNA replication in bacterial cells. Bacteriophages can harness this protein, however, and use it to reproduce the phage’s DNA. Thus, when Lsr2 stops working, the phage cannot replicate and it cannot manipulate bacterial cells.

    In the video above, by first study author Charles Dulberger, a genetically engineered mutant phage infects Mycobacterium smegmatis. First, one phage particle (red dot at 0.42 seconds) binds to a bacterium. The phage DNA (green fluorescence) is injected into the bacterial cell (2-second mark). The bright green dots at the cells’ ends are not relevant. For a few seconds, the DNA forms a zone of phage replication, and fills the cell. Finally, the cell explodes at 6:25 seconds. (About three hours have been compressed to make this video.)

    The approach used in this study can also be used to investigate other links between bacteriophages and the bacteria they infect.

    “This paper focuses on just one bacterial protein,” noted co-corresponding study author Graham Hatfull, a Professor at the University of Pittsburgh. But there are many more opportunities to use this technique. “There are lots of different phages and lots of other proteins.”

    Sources: University of Pittsburgh, Nature Microbiology


    Carmen Leitch

    Analysis of rebound virus suggests two separate reservoirs of latent HIV in patients

    When people living with HIV take antiviral therapy (ART), their viral loads are driven so low that a standard blood test cannot detect the virus. However, once ART is stopped, detectable HIV re-emerges with new cells getting infected. This is called “rebound” virus, and the cells that release the virus to re-ignite the infection come from a small population of HIV-infected CD4+ T cells that had remained dormant in blood and lymph tissue while individuals were on ART.

    It’s a problem called latency, and overcoming it remains a major goal for researchers trying to create curative therapies for HIV-;the special focus of the UNC HIV Cure Center.

    Now, scientists led by virologist Ron Swanstrom, PhD, Director of the UNC Center for AIDS Research and the Charles P. Postelle, Jr. Distinguished Professor of Biochemistry & Biophysics at the UNC School of Medicine, describe another layer to the challenge of HIV latency and published their work in Nature Microbiology.

    Swanstrom and colleagues, with collaborators at UCSF, Yale, the University of Gothenburg in Sweden, and others, provide indirect evidence for the existence of a distinct latent reservoir of CD4+ T cells in the central nervous system (CNS). They accomplished this by analyzing rebound virus in the cerebral spinal fluid (CSF) during the period when people had just stopped taking ART.

    Our analysis of rebound virus suggests latently infected T cells in the CNS are separate from the latent reservoir in the blood. Our analysis allows us to infer the presence of a distinct pool of latently infected cells in the CNS waiting to reinitiate infection once ART is interrupted.”

    Dr. Ron Swanstrom, senior author of the study

    The researchers compared the genetic sequences of rebound virus particles when ART was discontinued in 11 human participants. This approach allowed the scientists to assess the similarities between viral populations in the blood and CSF to determine whether they were part of a common latent reservoir. In many cases, the viral populations were not the same, which suggested they can represent different populations of latently infected cells.

    The researchers also studied details of viral replication to determine if rebound virus had been selected for replication in CD4+ T cells – the primary home of the virus – or had evolved to replicate in central nervous system myeloid cells, such as macrophages and microglia. All rebound viruses tested were adapted to growth in T cells. For several participants, the researchers also compared viral populations in blood and CSF before ART initiation and after ART was stopped.

    These experiments provide further evidence that HIV-infected CD4+ T cells can cross over from blood into the CNS, but also that some latently infected cells may be resident in the CNS during therapy. Any curative therapy would need to activate this dormant reservoir, as well as the latent reservoir in the blood and lymph tissue.

    Source:
    Journal reference:

    Swanstrom, R., et al. (2022) Rebound virus in the cerebrospinal fluid reveals a possible HIV-1 reservoir. Nature Microbiology. doi.org/10.1038/s41564-022-01309-3.