Research Finds New Vaccine Strategy Could Improve, Sustain Protection Against HIV

Researchers have discovered a new type of vaccination that could improve and sustain protection against HIV.¹

The vaccine—which has been tested on monkeys by a team of investigators from the Stanford School of Medicine and other institutions—is distinctive because it boosts cellular immunity rather than just stimulating serum immunity by increasing antibodies in the body.¹

“All licensed vaccines to date work by inducing antibodies that neutralize a virus. But inducing and maintaining a high enough level of neutralizing antibodies against HIV is a demanding task,” Bali Pulendran, PhD, professor of pathology and of microbiology and immunology at Stanford said in a release from the university.² “We’ve shown that by stimulating the cellular arm of the immune system, you can get stronger protection against HIV even with much lower levels of neutralizing antibodies.”

In the new study, which was recently published in Nature Medicine, the research team used a 2-prong approach to try to stimulate both serum and cellular immunity in the test group of rhesus macaques by dividing the subjects into distinct groups.¹

The first group received sequential inoculations of Env, a protein on the virus’s outer surface that is known to stimulate antibody production, according to the release. The group also received an adjuvant often used to strengthen the immune response.¹

The second group received a similar inoculation to the first group, but also received injections of 3 different infectious—but not dangerous—viruses that had an added viral protection gene known as Gag aimed at stimulating the cellular immunity in participants. The third group served as the control group of the study and researchers gave the subjects only the adjuvant.¹

The researchers found that when exposed to SHIV, a simian version of HIV, that both of treatment arms demonstrated significant initial protection from viral infection.

According to the results of the study, after 10 vaginal challenges with the autologous virus, protection was observed in the first group at 53.3%, whereas that rate was even higher—at 66.7%—for the second group that received the added viral protection gene Gag.¹

“Notably, though several Env-plus-Gag animals—but none of the Env animals—remained uninfected even though they lacked robust levels of neutralizing antibodies,” the release stated.²

The group who received the Env-plus-Gag combination also demonstrated an increased duration of protection effect. After a 20-week break, researchers reported that 6 monkeys from the Env group and 6 from the Env-plus-Gag group were exposed once again to SHIV.¹

Four of the monkeys in the Env-plus-Gag group remained uninfected, whereas just 1 in the Env group remained uninfected, researchers said.¹

Pulendran attributed the results to a likely production of tissue-resident memory T cells—which can help fight off hostile viruses—seen in the Env-plus-Gag treatment arm.²

“These results suggest that future vaccination efforts should focus on strategies that elicit both cellular and neutralizing-antibody response, which might provide superior protection against not only HIV but other pathogens such as tuberculosis, malaria, the hepatitis C virus, influenza and the pandemic coronavirus strain as well,” Pulendran said.²

It is estimated that approximately 1.1 million people in the United States have HIV today, according to HIV.gov. An estimated 14% are unaware they have the disease.³

References

1. Pulendran B, Arunachalam PS, Charles TP. T cell-inducing vaccine durably prevents mucosal SHIV infection even with lower neutralizing antibody titers. Nature Medicine. 2020. https://doi.org/10.1038/s41591-020-0858-8

2. New HIV vaccine strategy strengthens, lengthens immunity in primates. News Release. Stanford Medicine; May 11, 2020. Accessed June 23, 2020. http://med.stanford.edu/news/all-news/2020/05/hiv-vaccine-strategy-strengthens-lengthens-immunity-in-primates.html

3. HIV.gov. US Statistics. Last updated January 16, 2020. Accessed June 23, 2020. https://www.hiv.gov/hiv-basics/overview/data-and-trends/statistics#:~:text=Fast%20Facts,and%20gay%20and%20bisexual%20men.