Understanding bNAbs: The Immune System's Rare Advantage
HIV is notorious for evading the immune system by constantly mutating the surface proteins that antibodies typically recognize. Yet, a small subset of people living with HIV develop a special type of antibody called broadly neutralising antibodies (bNAbs). These antibodies attach to conserved regions of the virus—parts that change very little—making them more effective at neutralising diverse HIV strains.
According to AVAC, a US-based NGO focused on HIV prevention tools, about 20 percent of people living with HIV naturally develop bNAbs after many years of infection. Researchers first identified bNAbs in a person living with HIV in the 1990s, and since then, they have learned to replicate and produce these antibodies in the lab, opening doors for therapeutic and preventive applications.
What the Latest Trials Show
At the 2026 International AIDS Conference in Rio de Janeiro, Brazil, in July, 21 abstracts related to bNAbs were presented, reflecting growing scientific interest. Several key trials have yielded nuanced results.
The AMP trials evaluated VRC01, a bNAb given as an infusion, to prevent HIV acquisition in men and transgender people who have sex with men, as well as in cis-gender women. The trials found that VRC01 did not prevent HIV infection overall, but it did show that bNAbs could neutralise certain HIV strains under specific conditions.
Building on this, the Combo-AMP trial, planned by HVTN and HPTN, will test whether providing a combination of different bNAbs can prevent HIV. Similarly, the CAPRISA 012C trial tested a combination of two bNAbs in young women in Southern Africa; while the combination did not prevent HIV infection overall, CAPRISA reported a trend towards protection when the viruses were sensitive to one or both of the antibodies, compared to when they were resistant.
Promise in Treatment: Post-Treatment Control
bNAbs also show potential as a treatment strategy. Results from analytical treatment interruption (ATI) studies, including the RIO and FRESH trials, demonstrated that bNAb infusions allowed some participants to remain off antiretroviral treatment for more than a year without the virus rebounding.
Michel Nussenzweig, senior physician at Rockefeller University, noted that research indicates bNAb therapy is more likely to achieve post-treatment control in individuals with a less diverse HIV reservoir, pre-existing autologous antibodies, and pre-existing stem cell-like CD8+ T cells.
In children, the Tatelo study reported in 2022 that 44% of children who received a combination of two bNAbs maintained viral control for 24 weeks after stopping HIV treatment. The ongoing Tatelo Plus study in Botswana is evaluating whether a combination of three bNAbs can sustain HIV suppression in young children after antiretrovirals are stopped.
The Road to a Vaccine
While antiretroviral medicines remain the only effective form of HIV treatment and are also extremely effective for prevention, scientists are pursuing bNAb-based approaches to broaden the toolbox. Since June, the government has been rolling out the six-monthly lenacapavir HIV prevention injection to around 10% of clinics, an important step in prevention.
For vaccines, scientists do not expect a single vaccination to trigger our bodies to produce mature bNAbs capable of combating HIV. Instead, they anticipate that a vaccine protocol involving a series of vaccines will be needed. To this end, the International AIDS Vaccine Initiative (IAVI) and partners launched a Phase 1 safety and dosing trial in South Africa at the end of 2025.
Challenges and Future Directions
Despite the promise, significant hurdles remain. bNAbs are difficult to elicit, and their effectiveness depends on the specific strains of the virus. The mixed results from prevention trials highlight the need for combination approaches and careful selection of antibodies. Nevertheless, the scientific leads are certainly there, and hope remains that bNAbs could become a gamechanger in the fight against HIV.