Visionary immunologist Charlie Janeway was known for calling adjuvants – vaccine additives that enhance the immune response – a “dirty little secret.”
Charlie Janeway, MD, in a hat he wore often
Janeway’s point was that foreign antigens, by themselves, were unable to stimulate the components of the adaptive immune system (T and B cells) without signals from the innate immune system. Adjuvants facilitate that help.
By now, adjuvants are hardly a secret, looking at some of the research that has been coming out of Emory Vaccine Center. This week, an analysis by Ali Ellebedy, now at Washington University St Louis, and colleagues showed that in healthy volunteers, the AS03 adjuvant boosted otherwise poor immune responses to a limited dose of the exotic avian flu H5N1, recruiting both memory and naïve B cells. More on that here.
The Moderna SARS-CoV-2 vaccine, which has shown some activity in a small clinical trial here at Emory, has its own kind of adjuvant, since it’s made of both innate-immune-stimulating mRNA and clothed in lipid nanoparticles. Extra adjuvants may come into play later, either with this vaccine or others.
A question we’ve seen many people asking, and discussed on Twitter etc is this: how long does the immunity induced by a SARS-CoV-2 vaccine last? How can we make the immune cells induced by a vaccine stick around for a long time? Read more
Police procedural television shows, such as Law + Order, have introduced many to the Internal Affairs Bureau: police officers that investigate other police officers. This group of unloved cops comes to mind in connection with the HIV/AIDS research published this week by Rama Amara’s lab at Yerkes National Primate Research Center and Emory Vaccine Center.
“Killer” antiviral T cells (red spots) can be found in germinal centers. The green areas are B cell follicles, which HIV researchers have identified as major reservoirs for the virus. Image courtesy of Rama Amara.
HIV infection is hard to get rid of for many reasons, but one is that the virus infects the cells in the immune system that act like police officers. The “helper” CD4 T cells that usually support immune responses become infected themselves. For the immune system to fight HIV effectively, the “killer” CD8 antiviral T cells would need to take on their own CD4 colleagues.
When someone is HIV-positive and is taking antiretroviral drugs, the virus is mostly suppressed but sticks around in a reservoir of inactive infected cells. Those cells hide out in germinal centers, specialized areas of lymph nodes, which most killer antiviral T cells don’t have access to. A 2015 Nature Medicine paper describes B cell follicles, which are part of germinal centers, as “sanctuaries” for persistent viral replication. (Imagine some elite police unit that has become corrupt, and uniformed cops can’t get into the places where the elite ones hang out. The analogy may be imperfect, but might help us visualize these cells.)
Amara’s lab has identified a group of antiviral T cells that do have the access code to germinal centers, a molecule called CXCR5. Knowing how to induce antiviral T cells displaying CXCR5 will be important for designing better therapeutic vaccines, as well as efforts to suppress HIV long-term, Amara says. The paper was published in PNAS this week. Read more
HIV researchers are becoming increasingly bold about using the “cure” word in reference to HIV/AIDS, even though nobody has been cured besides the “Berlin patient,” Timothy Brown, who had a fortuitous combination of hematopoetic stem cell transplant from a genetically HIV-resistant donor. Sometimes researchers use the term “functional cure,” meaning under control without drugs, to be distinct from “sterilizing cure” or “eradication,” meaning the virus is gone from the body. A substantial obstacle is that HIV integrates into the DNA of some white blood cells.
HIV cure research is part of the $35.6 million, five-year grant recently awarded by the National Institutes of Health to Yerkes/Emory Vaccine Center/Emory Center for AIDS Research. Using the “shock and kill” approach during antiviral drug therapy, researchers will force HIV (or its stand-in in non-human primate research, SIV) to come out of hiding from its reservoirs in the body. The team plans to test novel “latency reversing agents” and then combine the best one with immunotherapeutic drugs, such as PD-1 blockers, and therapeutic vaccines.
The NIH also recently announced a cluster of six HIV cure-oriented grants, named for activist Martin Delaney, to teams led from George Washington University, University of California, San Francisco, Fred Hutchinson Cancer Research Center, Wistar Institute, Philadelphia, Beth Israel Deaconess Medical Center and University of North Carolina. Skimming through the other teams’ research plans, it’s interesting to see the varying degrees of emphasis on “shock and kill”/HIV latency, enhancing the immune response, hematopoetic stem cell transplant/adoptive transfer and gene editing weaponry vs HIV itself.
This week, researchers from Yerkes and Emory Vaccine Center led by Cindy Derdeyn published a paper that I first thought was disturbing. It describes how monkeys vaccinated against HIV’s relative SIV (simian immunodeficiency virus) still become infected when challenged with the virus. Moreover, it’s not clear whetherÂ the vaccine-induced antibodies are exerting any selective pressure on the virus that gets through.
But then I realized that this might beÂ an example of “burying the lead,” since we haven’t made a big hoopla about the underlying vaccineÂ studies, conducted by Rama Amara. Some of these studiesÂ showed that a majority of monkeys can beÂ protected from repeated viral challenge.Â TheÂ more effective vaccine regimens include adjuvants such asÂ the immune-stimulating molecules GM-CSF or CD40LÂ (links are the papers on the protective effects). Read more
Two presentations on Emory research at last week’s AIDS Vaccine 2010 conference concerned adjuvants. These are substances that act as amplifiers, stimulating the immune system while keeping its focus on the specific components of a vaccine.
Charlie Janeway (1943-2003)
Immunologist Charlie Janeway once described adjuvants as immunology’s “dirty little secret,” because for a long time scientists did not know how they worked. Some adjuvants can sound irritating and nasty, such as alum and oil emulsion. Alum is the only vaccine adjuvant now licensed for human clinical use in the US. Over the last few years, scientists have learned that adjuvants rev up what is now known as the “innate immune system,” so that the body knows that the vaccine is something foreign and dangerous.
Rama Rao Amara, a vaccine researcher at Emory Vaccine Center and Yerkes National Primate Research Center, and Harriet Robinson, former head of microbiology and immunology at Yerkes and now chief scientific officer at the firm GeoVax, both described extra ingredients for the DNA/MVA vaccine that Robinson designed while at Yerkes in collaboration with NIH researchers.