Download MendeleyStructural Definition of an Antibody-Dependent Cellular Cytotoxicity Response Implicated in Reduced Risk for HIV-1 Infection.
Acharya, P., Tolbert, W.D., Gohain, N., Wu, X., Yu, L., Liu, T., Huang, W., Huang, C.C., Kwon, Y.D., Louder, R.K., Luongo, T.S., McLellan, J.S., Pancera, M., Yang, Y., Zhang, B., Flinko, R., Foulke, J.S., Sajadi, M.M., Kamin-Lewis, R., Robinson, J.E., Martin, L., Kwong, P.D., Guan, Y., DeVico, A.L., Lewis, G.K., Pazgier, M.(2014) J Virol 88: 12895-12906
- PubMed: 25165110
- DOI: https://doi.org/10.1128/JVI.02194-14
- Primary Citation of Related Structures:
4H8W, 4R4B, 4R4F, 4R4H, 4R4N - PubMed Abstract:
The RV144 vaccine trial implicated epitopes in the C1 region of gp120 (A32-like epitopes) as targets of potentially protective antibody-dependent cellular cytotoxicity (ADCC) responses. A32-like epitopes are highly immunogenic, as infected or vaccinated individuals frequently produce antibodies specific for these determinants. Antibody titers, as measured by enzyme-linked immunosorbent assay (ELISA) against these epitopes, however, do not consistently correlate with protection. Here, we report crystal structures of CD4-stabilized gp120 cores complexed with the Fab fragments of two nonneutralizing, A32-like monoclonal antibodies (MAbs), N5-i5 and 2.2c, that compete for antigen binding and have similar antigen-binding affinities yet exhibit a 75-fold difference in ADCC potency. We find that these MAbs recognize overlapping epitopes formed by mobile layers 1 and 2 of the gp120 inner domain, including the C1 and C2 regions, but bind gp120 at different angles via juxtaposed VH and VL contact surfaces. A comparison of structural and immunological data further showed that antibody orientation on bound antigen and the capacity to form multivalent antigen-antibody complexes on target cells were key determinants of ADCC potency, with the latter process having the greater impact. These studies provide atomic-level definition of A32-like epitopes implicated as targets of protective antibodies in RV144. Moreover, these studies establish that epitope structure and mode of antibody binding can dramatically affect the potency of Fc-mediated effector function against HIV-1. These results provide key insights for understanding, refining, and improving the outcome of HIV vaccine trials, in which relevant immune responses are facilitated by A32-like elicited responses.
Organizational Affiliation:
Vaccine Research Center, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, USA.
