Differences in intravenous drug users may affect their response to an HIV vaccine
by Jeannie Wraight
Prevention strategies such as Treatment as Prevention, PrEP, syringe exchange, and public awareness have helped to reduce the global number of new HIV infections over the past fifteen years by thirty-five percent. Despite these advances, the rate of new HIV infections in 2015 was an alarming 2.1 million and continues to rise among certain high-risk groups. As such, an effective, universal preventative vaccine (that can also be used as a therapeutic vaccine) is likely the only course in permanently stopping the spread of HIV worldwide and fulfilling the elusive dream of an “HIV-free generation.”
However, new research may indicate that the current course of vaccine research may lead to a preventative vaccine that is ineffective for an entire high risk population, thus delaying efforts to eradicate HIV.
Research conducted by Dr. James Kobie and his team at the University of Rochester, found that intravenous drug users (IVDUs) have severe differences in their immune system that could potentially limit their development of the same protection conferred by a potential HIV preventative vaccine as the general population. Dr. Kobie compared the blood of nineteen HIV-negative, active intravenous drug user volunteers to nineteen HIV-negative, non-drug using individuals. Over 100 different aspects of the participants’ B cells and antibodies were measured.
Dr. Kobie and his team found that B cells of the IVDU participants differed substantially from the non-IVDU participants. The IVDU groups’ B cells showed signs of over-activity, suggesting more frequent stimulation of immune responses. The exact cause of this stimulation is yet unknown. However, researchers also discovered high levels of endotoxins in the blood of some of the IVDU participants. An endotoxin is a toxin that sits in the outer wall of some bacteria and its release into the body can elicit a B-cell response. In addition, large numbers of cytokines that can cause inflammation were also found.
Intravenous drug users often experience a larger number of infections, sometimes generating from injection sites, as well as reactions to impurities contained in the injected drug. These may also cause a degree of immune activation.
Highly effective vaccines most often depend on successful B-cell and antibody responses and these responses can be compromised if an individual’s immune system is already overtaxed. Does this mean that an HIV vaccine may not prove to have the same efficacy in IDVUs as it might in other populations? The answer remains to be determined. However, it has been previously shown that IVDUs have a reduced response to hepatitis A and hepatitis B vaccines, meaning that a reduced response to an HIV vaccine is conceivable.
“If we fail to appreciate differences in the immune response of injection heroin users, we may develop an HIV vaccine that fails to protect against a growing vulnerable population,” stated Dr. Kobie.
Although this is one small study and follow-up studies are needed to confirm the results, Dr. Kobie’s research is a reminder of the importance of continued funding for HIV research that is inclusive of all populations, such as IVDUs, especially as we know that the rate of opiate addiction in the United States is skyrocketing. According to the World Drug Report 2016 released by the UN Office on Drugs and Crime, the use of heroin in the U.S. is at its highest point in the past twenty years, with an estimated 1 million heroin users in 2014. Rates of heroin addiction have drastically increased particularly among whites aged eighteen to forty-four and people living on lower incomes.
Unlike most other populations, with the exception of men of color who sleep with men, HIV infection in IVDUs in the U.S. and Central and Western Europe is growing. In the U.S. 9.1 percent of HIV- positive people are injection drug users. It’s estimated that 1.6 million of the 12 million people (one in seven) worldwide who inject drugs are HIV-positive.
If further research confirms that IVDUs are unable to mount the same immune response with vaccination as other populations, then incorporating modes of infection in vaccine development is even more vital. Ultimately, it may be imperative that HIV vaccine research accounts for and develops strategies to overcome potential differences in the immune response of the most vulnerable populations, such as IVDUs. These preliminary findings also reiterate the importance of the need for all people categorized by race/ethnicity and risk factor to participate in research in order to meet the needs of the entire population.
“When we were performing the Microgenesys gp160 vaccine trials in the early 1990s, we were ecstatic that one of the earliest imunotherapeutic vaccine candidates was ‘highly immunogenic’ in most subjects. However, this never translated into clinical efficacy,” stated Dr. Gary Blick MD, Founder, Chief Medical Officer, Health Care Advocates International, LLC. “Now, as we continue to elucidate the complexity of the human immune system, we are once again humbled in our quest to develop any effective immunoprophylactic or immunotherapeutic HIV vaccine. Dr. Kobie’s work in IVDUs continues to expand our knowledge base while, once again, reminding us of the insurmountable and near-improbable task of developing a one-size-fits-all vaccine for prevention or treatment. Nevertheless, we must keep forging ahead undeterred if we are to end the global health threat of HIV.”
Jeannie Wraight is the former editor-in-chief and co-founder of HIV and HCV Haven (www.hivhaven.com) and a blogger and writer for TheBody.com. She is a member of the Board of Directors of Health People, a community-based organization in the South Bronx and an advisor to TRW (Teach me to Read and Write), a community-based organization in Kampala, Uganda. She lives with her husband in New York City.