143 HIV Transmission: The Role of Neutralizing AntibodiesOverbaugh, J; Blish, C; Lynch, J; Provine, N; Team, the Seattle/Kenya ResearchJAIDS Journal of Acquired Immune Deficiency Syndromes: April 2011 - Volume 56 - Issue - p 58 doi: 10.1097/01.qai.0000397329.72363.9c Abstracts Free Author InformationAuthors Article MetricsMetrics Division of Human Biology, Fred Hutchinson Cancer Research Center, Seattle, WA; and University of Nairobi and Coast Provincial General Hospital, Kenya At present, it is unknown whether the presence of HIV-specific neutralizing antibodies (NAbs) provides any protection from infection in individuals naturally exposed to HIV. Although here is evidence that select NAbs can protect in the SHIV/macaque model, these studies were limited to analysis of a few select neutralization sensitive challenge strains that are not representative of circulating HIV. We have examined whether NAbs, when present at the levels found in natural HIV-infection, can reduce the risk of HIV acquisition using two cohorts: 1) HIV positive high-risk women who continue to be exposed to new source partners and 2) breastfeeding infants of HIV positive mothers, who may have HIV NAbs through passive transfer. Both of these settings provide a situation in which the individual has pre-existing HIV-specific antibodies at the time of exposure to HIV. Among high-risk women, those who became superinfected by a second partner did not show evidence of notably weak or narrow NAb responses at the time of superinfection compared to women who did not become superinfected. In infants, the presence of broad potent neutralizing antibodies did not impact of their risk of HIV acquisition after birth. Together, these studies suggest that neutralizing antibodies that are elicited by a natural HIV infection are not of sufficient breadth or potency to protect against diverse circulating strains of HIV-1.Copyright © 2011 Wolters Kluwer Health, Inc. All rights reserved.