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Co-operation between strain-specific and broadly neutralizing responses limited viral escape, and prolonged exposure of the broadly neutralizing epitope.

Co-operation between strain-specific and broadly neutralizing responses limited viral escape, and prolonged exposure of the broadly neutralizing epitope.
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Anthony C, York T, Bekker V, Matten D, Selhorst P, Ferreria RC, Garrett NJ, Abdool Karim SS, Morris L, Wood NT, Moore PL, Williamson C,


Anthony C, York T, Bekker V, Matten D, Selhorst P, Ferreria RC, Garrett NJ, Abdool Karim SS, Morris L, Wood NT, Moore PL, Williamson C, (click to view)

Anthony C, York T, Bekker V, Matten D, Selhorst P, Ferreria RC, Garrett NJ, Abdool Karim SS, Morris L, Wood NT, Moore PL, Williamson C,

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Journal of virology 2017 07 05() pii 10.1128/JVI.00828-17

Abstract

V3-glycan targeting broadly neutralizing antibodies (bNAbs) are a focus of HIV-1 vaccine development. Understanding the viral dynamics that stimulate the development of these antibodies can provide insights for immunogen design. We used a deep sequencing approach, together with neutralization phenotyping, to investigate the rate and complexity of escape from V3-glycan directed bNAbs, compared to overlapping early strain-specific neutralizing antibody (ssNAb) responses to the V3/C3 region in donor CAP177. Escape from the ssNAb response occurred rapidly, via a N334 to N332 glycan switch, which took just 7.5 weeks to reach >50 % frequency. In contrast, escape from the bNAbs was mediated via multiple pathways and took longer, with escape first occurring through an increase in V1 loop length, which took 46 weeks to reach 50% frequency; followed by an N332 to N334 reversion which took 66 weeks. Importantly, bNAb escape was incomplete, with contemporaneous neutralization observed up to three years post infection. Both the ssNAb response and the bNAb response were modulated by the presence/absence of the N332 glycan, indicating an overlap between the two epitopes. Thus, selective pressure by ssNAbs to maintain the N332 glycan may have constrained the bNAb escape pathway. This slower and incomplete viral escape resulted in prolonged exposure of the bNAb epitope, which may in turn have aided the maturation of the bNAb lineage.IMPORTANCE: The development of an HIV-1 vaccine is of paramount importance, and broadly neutralizing antibodies are likely to be a key component of a protective vaccine. The V3-glycan targeting bNAb responses are among the most promising vaccine targets as they are commonly elicited during infection. Understanding the interplay between viral evolution and the development of these antibodies provides insights that may guide immunogen design. Our work contrasted the dynamics of the early strain-specific antibodies and the later broadly neutralizing responses, to a common Env target (V3C3), showing slower and more complex escape from bNAbs. Constrained bNAb escape, together with evidence of contemporaneous autologous virus neutralization, supports the proposal that prolonged exposure of the bNAb epitope enabled the maturation of the bNAb lineage.

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