SHOTS HEARD ROUND THE WORLD: HIV VACCINE

SHOTS HEARD ROUND THE WORLD

HOW THE COVID-19 PANDEMIC IS HELPING DEVELOP AN HIV VACCINE By Marissa McCollum Areeha Khalid

While HIV has been a constant threat for over three decades, COVID-19 has surpassed its estimated death toll—700,000 people in the U.S.—in under two years. This does not mean, however, that COVID-19 will likewise go untreated. There are multiple vaccines already authorized by the FDA, and the efficacy of both Pfizer and Moderna vaccines is consistently rated above 88% against the alpha strain. With 66% of the U.S. population at least partially vaccinated, COVID-19 appears to have a much shorter historical period of unchecked infection than HIV. Even more optimistically, some new research is working toward a preventative immunization against HIV using the same mRNA technology responsible for the success of some of the COVID-19 vaccines.

First clinically identified in 1982, AIDS is one of the most well-known epidemics of the modern age. AIDS, or acquired immunodeficiency syndrome, strips the body’s natural immune system, leaving patients susceptible to illness or death from even minor infections. The pathogen behind this disease, HIV (human immunodeficiency virus) has infected over 1.1 million people in the United States as of 2019. Despite the prolific nature of the disease, the CDC estimates that around 15% of those infected are unaware and therefore liable to unknowingly spread HIV to others. AIDS has no cure, only treatments to mitigate symptoms and reduce communicability.

Current trials are not the first attempts to curb HIV transmission. The first treatments used for HIV were direct acting dideoxynucleoside reverse transcriptase inhibitors (NRTIs), a class of drugs that prevent the virus from inserting its own genome into host cells, the means by which HIV reproduces within an infected body. HIV is comparatively difficult to completely eliminate after infection has set in, as it produces latent “reservoirs” which allow the virus to persist through attempts to eradicate the active infection. However, current antiretroviral therapy has lowered the mortality of HIV to close to zero when treated quickly and adequately. Preventative measures also exist, such as preexposure prophylaxis (PrEP), a daily medication for high-risk populations, such as men and transgender women who have sex with men, or injection drug users. Despite these improvements, a single-dose prevention remains elusive.

Even a vaccine efficacy as low as 50% sustained for two years would lower infection rates significantly

in high-incidence areas, according to Dr. Paul Stoffels, an HIV researcher and chief scientific officer for Johnson & Johnson. One promising vaccine trial, performed in Thailand in 2009, showed 60.5% efficacy one year after vaccination with RV144, but this protection decreased after three years to only 31.2%. Still, the Thai trial offers hope in the face of numerous failed trials since.

A study completed in the U.S. from 2009 to 2013 used DNA prime–recombinant adenovirus type 5 boost (DNA/rAd5), a method similar to the mRNA system used in the COVID-19 vaccination. In this method, DNA for antigens, proteins that exist on the surface of a given virus, are injected, causing the host body to replicate solely those proteins used for recognition. This prompts the body to produce antibodies against the pathogen, which increases efficiency when dealing with a legitimate infection. Unfortunately, despite the success of COVID19 mRNA immunizations, the DNA HIV vaccine did not offer any substantial protection. As Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases (NIAID) remarked after a failed HIV vaccine trial, “The development of a safe and effective vaccine to prevent HIV infection has proven to be a formidable scientific challenge.”

Nearly all viruses, including HIV and COVID-19, mutate as they are passed from one host to another. In order to limit such effects of mutations on vaccine efficacy, later HIV trials used “mosaic” molecules that include aspects of multiple variants’ antigens. A study that ran from 2017 to 2019 in sub-Saharan Africa saw 25.2% efficacy by using such a mosaic, a far cry from the 50% needed to effect lower rates of infection, but another promising foundation for future studies.

Hopes could rest on one such clinical study in progress, which uses the same mRNA platform as the Moderna COVID-19 immunization. Known as mRNA-1644, the vaccine is sponsored by the Bill and Melinda Gates Foundation and the International AIDS Vaccine Initiative. The study will likely start recruiting adults without HIV before the end of the year, and is set to finish in May 2023. If successful, or even if only partially effective, the results of the present studies will inform HIV treatment and prevention far into the future. Science is inching ever closer to a permanent solution for the HIV/ AIDS epidemic.

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