Potential for HIV vaccine
AN HIV vaccine regimen tested in an early-phase clinical trial has elicited robust immune responses, appearing stronger than those observed in a landmark 2009 study, showing that a vaccine can protect people from HIV infection.
These are the findings from the ongoing Phase I/II HVTN 100 study of a vaccine regimen designed to improve upon the one used in 2009 – the US Military HIV Research Programme-led RV144 trial in Thailand, the only study to date to show protection, albeit modest, in humans.
Building on the Thailand findings, the National Institute of Allergy and Infectious Diseases (Niaid) of the National Institutes of Health and the Niaid-funded HIV Vaccines Trials Network (HVTN) joined with other organisations to form the Pox Protein Public Private Partnership (P5), a public/private collaboration, to improve on the potency, breadth and duration of protection seen in RV144.
Early results from HVTN 100 show stronger immune responses than some of those recorded in RV144, suggesting the potential for higher levels of protection from the modified vaccine regimen.
The trial was chaired by two South African researchers, Professor Linda-Gail Bekker and Dr Fatima Laher. They collaborated with six South African trial centres to enrol HIV-negative adult volunteers starting in February 2015. Of the 252 people enrolled in the study, 210 received the vaccine regimen and 42 received a placebo.
The researchers followed the volunteers over the years to better understand the immune response to the vaccine. The vaccine regimen administered in the HVTN 100 trial is based on the RV144 regimen, but designed to elicit immune responses to the HIV subtype common in sub-Saharan Africa.
In addition, the adjuvant (immunological agent) was changed in an effort to improve the immune response to the regimen. Also, an additional vaccination was included at one year in the HVTN 100 trial to prolong the early protective effect observed in RV144.
Results from HVTN 100 showed that all volunteers who completed the first four vaccinations developed antibody responses two weeks after the fourth vaccination. Similarly, cellular immune responses were strong.
“There was a pre-specified set of immune response criteria to signal whether the regimen should move forward into advanced phase testing or not.
“Those criteria were met, which is why we are currently conducting HVTN 702, an advanced-phase large-scale trial that seeks to understand if the vaccines can prevent HIV infection in human beings,” Bekker said.