Scientists say the results of an HIV vaccine trial in South Africa could break the notion that each region of the world needs a separate type of HIV vaccine based upon their circulating strains. Photo: African News Agency (ANA) Scientists say the results of an HIV vaccine trial in South Africa could break the notion that each region of the world needs a separate type of HIV vaccine based upon their circulating strains. Photo: African News Agency (ANA)
Cape Town – The results of an HIV vaccine trial in South Africa has seen even better results than those recorded in Thailand, where the vaccine was first tested.
Scientists say this could break through the notion that each region of the world needs a separate type of HIV vaccine based upon their circulating strains.
The results of the study, “HVTN 097: Immune correlates of the Thai RV144 vaccine regimen in South Africa”, led by HIV Vaccine Trials Network (HVTN) co-principal investigator and SA Medical Research Council (SAMRC) president Dr Glenda Gray, were published in the journal Science Translational Medicine yesterday.
This study was conducted in South Africa using the same HIV vaccine regimen that showed modest protection in an efficacy study conducted in Thailand, where clades B and E were prominent, a subtype within HIV-1 infections.
HIV-1 and HIV-2 are two distinct viruses. Worldwide, the predominant virus is HIV-1.
Although clade C is the dominant circulating strain of HIV in South Africa, the RV144/Thai vaccine regimen mounted significant cellular and antibody responses in study participants enrolled in South Africa.
Despite major breakthroughs in HIV prevention and treatment, an estimated 1.8 million people were newly infected with HIV in 2018, with an estimated 5000 new HIV infections around the world every day.
Gray and her team evaluated whether the vaccine-induced immune responses would be similar in a South African cohort if immunised with the same RV144 HIV vaccine regimen used in Thailand.
The US Army-led RV144 was the first vaccine clinical trial to ever demonstrate any efficacy in preventing HIV that tested a heterologous “prime-boost” combination of two vaccines: Alvac-HIV and Aidsvax B/E vaccine based on clades B and E, which demonstrated moderate protection against HIV with a 31.2% efficacy.
“Vaccine-induced immune responses elicited from this clade B/E based vaccine regimen induced cross-clade responses in South Africans and, at peak immunogenicity, the South African vaccines exhibited significantly higher cellular and antibody immune responses than the Thai vaccines,” said Gray.
The HVTN 097 study is part of a larger HIV vaccine research endeavour led by the Pox-Protein Public-Private Partnership, or P5 - a group of public and private organisations committed to building on the success of the RV144 trial.
The P5 members include the National Institute of Allergy and Infectious Diseases, part of the National Institutes of Health, Bill and Melinda Gates Foundation, SAMRC, the US Military HIV Research Program (MHRP) at the Walter Reed Army Institute of Research, among others.
“Since 2009, the HIV vaccine field has been building on findings from RV144 to understand and develop improvements in vaccine breadth and duration in order to protect more people for longer periods of time,” MHRP principal deputy director Julie Ake said.
The RV144 vaccine regimen in HVTN 097 vaccines induced a significantly higher CD4+ T cell response rate than seen in the Thai vaccine recipients, irrespective of age and sex.
South African and Thai participants also generated cross-clade antibody responses against HIV clades AE, B, and C, which, in a panel of clade C antigens, were also higher and more prevalent in South Africans.
In general, cross-clade immune responses were stronger than expected in South Africa. HVTN 097 is a precursor to studies that adapted the RV144/Thai vaccine regimen to be clade C-specific, now under way in South Africa (HVTN 702).
“This breaks open the thought pattern that each region of the world needs a separate type of HIV vaccine based upon their circulating strains,” HVTN principal investigator Larry Corey said.