Neutralizing antibodies generated during natural HIV-1 infection: good news for an HIV-1 vaccine?

Most existing viral vaccines generate antibodies that either block initial infection or help eradicate the virus before it can cause disease. For HIV-1, obstacles to eliciting protective neutralizing antibodies (NAbs) have often seemed insurmountable. The target of HIV-specific NAbs, the viral envelope glycoprotein (Env), is highly variable in amino acid sequence and glycosylation pattern. Conserved elements of HIV-1 Env seem to be poorly immunogenic, and previous attempts to generate broadly reactive NAbs by vaccination have proven ineffective. However, recent studies show that antibodies in the sera of some HIV-1–infected individuals can neutralize diverse HIV-1 isolates. Detailed analyses of these sera provide new insights into the viral epitopes targeted by broadly reactive NAbs. The findings discussed here suggest that the natural NAb response to HIV-1 can inform future vaccine design. A concerted effort of structure-based vaccine design will help guide the development of improved antibody-based vaccines for HIV-1.