New HIV vaccine strategy targets body’s mucosal sites
- Some 80 per cent of HIV transmissions take place via vaginal or rectal mucosa
- New vaccine strategy aims to elicit mucosal as well as systemic immunity
- Efficacy is yet to be proven in humans and this may be years away
Results from a mouse model trial may help develop effective mucosal HIV-1 vaccines in the future. Unlike previous vaccine trials, the new approach offers protection at mucosal sites — vaginal or rectal — that are most likely to encounter the virus first.
“Our vaccine approach aims at making the antibodies inhibit the HIV Tat (Transactivator of HIV gene expression) effect, thereby preventing the HIV virus from replicating.”
Eric Gowans, University of Adelaide
Eric Gowans, who is leading the research team at the University of Adelaide’s Basil Hetzel Institute for Translational Health Research, says, “Our vaccine approach aims at making the antibodies inhibit the HIV Tat (Transactivator of HIV gene expression) effect, thereby preventing the HIV virus from replicating. We believe that our strategy may be more effective than other studies for three reasons: Our vaccine will elicit mucosal immunity to Gag (The capsid proteins or group specific antigens) and Tat; systemic immunity to Tat; and cell-mediated immunity to Gag and Tat.”
Approximately 80 per cent of HIV infections are the result of mucosal transmission. “Consequently, a strategy to elicit mucosal immunity is likely to be more effective. Our vaccine strategy is designed to elicit a combination of mucosal immunity (humoral and cell mediated) with systemic cell-mediated responses to Gag and Tat proteins that will result in migration of immune cells to sites of HIV infection. This approach may provide a novel strategy to prevent HIV infection,” Gowans tells SciDev.Net.
A recent study from Switzerland suggested that although broadly neutralising antibodies to Env (envelope proteins) developed in a small number of patients, these were dependent on a high viral antigen load for many years and viral diversity criteria that cannot be achieved with current vaccine strategies.
“Most HIV vaccines are designed to elicit systemic immunity to the Env, which can mutate rapidly. The Gag and Tat proteins are more highly conserved. As noted in an Italian study, anti-Tat antibodies have the potential to prevent disease progression, and our vaccine generates anti-Tat antibodies which neutralise the transactivation activity of the Tat protein,” Gowan added. The Adelaide laboratory studies, published in Nature on 17 November, received funding from The Hospital Research Foundation and the National Health and Medical Research Council.
According to WHO, an estimated 2.1 million people were newly infected with HIV in 2015. Bridget Haire, president of the Australian Federation of AIDS Organisations (AFAO), says, “AFAO welcomes this new development towards an HIV vaccine, while noting that it will be many years before we know if it will have any efficacy in humans.”
This piece was produced by SciDev.Net’s South-East Asia & Pacific desk.