HIV Vaccine Targets Subtype Circulating in Southern Africa

The emergence of infectious diseases, such as Zika and Ebola, over the past few decades has caused quite a stir worldwide. Nonetheless, infection with one particular virus, HIV, remains one of the greatest threats in the world today.

HIV is not always the actual cause of death in individuals living with the virus. Opportunistic infections that would be less-dangerous in individuals who do not have weakened immune systems (a prognosis of HIV), can be life threatening. As a result, research on a cure for HIV remains paramount. Recently, there have been several breakthroughs in the fight against HIV, including trials that test an HIV vaccine that targets a specific subtype of the virus, and several prevention methods that decrease the risk of infection transmission.

New HIV Vaccine Trial

A new clinical trial, HVTN 100, will examine a vaccine regimen specifically designed for virus subtype C, which is currently circulating the southern countries of Africa. This trial will build on the findings of the RV144 trial, led by a United States military program in Thailand, which found the vaccine to be 31.2% effective for 3.5 years after initial vaccination.

Two vaccines will be used together in the regimen to be examined in the HVTN 100 trial: ALVAC-HIV, a canarypox-based vaccine produced by Sanofi Pasteur; and a protein vaccine using an adjuvant to boost immune response, produced by Novartis Vaccines. According to the press release, the Phase I/II trial will enroll 252 HIV-uninfected heterosexual adults between the ages of 18 and 40 years, who will receive eight vaccine injections over one year, after which they will receive booster shots.

HVTN 100, is sponsored by Pox-Protein Public-Private Partnership (P5)—which includes public as well as private organizations, such as the National Institute of Allergy and Infectious Diseases (NIAID)—and is part of a larger study which aims to not only create a vaccine, but also understand the body’s immune response that can prevent HIV infection.

The HVTN 100 trial results will be available within 2 years.

Preventing HIV Transmission

As a sexually transmitted disease, the use of condoms has long been touted as the number one way to prevent HIV transmission. A new study recently published in JAMA, however, is shedding new light on the effectiveness of antiretroviral therapy (ART) in preventing HIV transmission. According to the study, although there was no use of condoms, there was no transmission of HIV infection between approximately 900 couples where one partner was HIV-positive and the other HIV-negative. The trial tested transmission in men who have sex with men (MSM) as well as heterosexual couples.

The trial followed adults with HIV-1 RNA with viral loads less than 200 copies/ml, using ART for a median of 1.3 years. There were 1,166 inital couples enrolled in the study, and of those, 888 couple participants provided approximately 1,200 eligible couple-years of follow up. Prior to enrollment, couples reported having engaged in sexual intercourse without condoms for a period of 2 years. A total count of about 22,000 condomless sex acts were reported in MSM couples, while 36,000 condomless sex acts were reported among heterosexual couples. By the end of the study, only 11 of the participants who were initially HIV-negative had become HIV-positive: 10 MSM and 1 heterosexual individual. However, “no phylogenetically (molecular characteristics that indicate whether a virus is similar or different from another) linked transmissions occurred over eligible couple-years of follow-up, giving a rate of within-couple HIV transmission of zero.” These individuals may have contracted HIV from non-study participants, as 129 of the enrolled HIV-negative patients reported engaging in condomless sex with other partners.

For those living with HIV, ART has many benefits. In addition to preventing sexual transmission between partners, a study, funded by NIAID and the Eunice Kennedy Shriver National Institute of Child Health and Development (NICHD), has found that if HIV-positive women take a three-drug regimen during breastfeeding, they can “virtually eliminate HIV transmission” through breastmilk. Further studies focus on eliminating HIV transmission to HIV-uninfected women.

With the production of an HIV vaccine, and a research focus on preventing HIV transmission, eradicating HIV infection may be in the forseeable future.