Developmental pathway for potent V1V2-directed HIV-neutralizing antibodies

Area of Science:

• Immunology
• Virology
• Vaccine Development

Background:

• Neutralizing antibodies targeting HIV-1 envelope variable regions 1 and 2 (V1V2) are crucial for viral control.
• The precise mechanism by which these potent antibodies develop has remained largely undefined.

Purpose of the Study:

• To elucidate the developmental pathway of HIV-1 V1V2-directed neutralizing antibodies.
• To understand the molecular characteristics required for antibody-mediated neutralization of HIV-1.

Main Methods:

• Isolation and characterization of twelve somatically related neutralizing antibodies (CAP256-VRC26.01-12) from an HIV-1 infected donor (CAP256).
• Analysis of the antibody's antigen-binding loop (complementarity-determining region (CDR) H3) and its developmental timeline.
• Correlation of antibody maturation with viral population diversity and neutralization potency.

Main Results:

• Identified a characteristic protruding tyrosine-sulphated, anionic antigen-binding loop (CDR H3) in all isolated neutralizing antibodies.
• The unmutated ancestor antibody, with a 35-residue CDR H3, emerged between 30-38 weeks post-infection and neutralized a superinfecting virus.
• Enhanced neutralization breadth and potency were observed by week 59, following modest affinity maturation and significant viral diversification.

Conclusions:

• HIV-1 V1V2-directed neutralizing antibodies can develop relatively rapidly.
• Initial selection of B cells possessing a long CDR H3 is a key step in antibody development.
• Limited subsequent somatic hypermutation contributes to the maturation of these neutralizing antibodies, providing critical insights for HIV-1 vaccine strategies.