Editors' ChoiceHIV Transmission

Dangerous Liaison

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Science Translational Medicine  11 Nov 2009:
Vol. 1, Issue 6, pp. 6ec22
DOI: 10.1126/scitranslmed.3000561

With nearly 33 million people living with HIV, and new infections occurring at a rate of 3 million per year, anything that we can learn about modes of transmission may illuminate strategies for rational pharmacological intervention. We still do not know how to obtain complete immunity and protect against HIV infection. Semen is the major transmission vector for human immunodeficiency virus-1 (HIV-1) as it houses the key sources of infectious virus: free virions, spermatozoa-associated virions, and infected leukocytes. However, since a bona fide receptor for HIV-1 on sperm has yet to be identified, the precise contribution of these factors to the attachment of HIV-1 to sperm, and thereby to the infection of critical immune cell targets, remains a mystery. Now, in an article reported in the Journal of Experimental Medicine, Geffner and colleagues show that sperm capture HIV-1, probably through heparan sulfate, and that direct cell-to-cell contacts between HIV-1–infected sperm and immature dendritic cells (DCs) enhance viral transmission. They found that heparan sulfate was present on sperm membranes and nearly half of the HIV-1 sperm found to interact with DCs were internalized, promoting the phenotypic maturation of the DC. Furthermore, using whole semen, the authors show that acidic pH, similar to the pH found in the vagina after sex, exacerbated HIV-1 binding to sperm and increased the transmission of HIV-1 from sperm to DCs by nearly four times. These results are in contrast to the view that the acidity of the vagina protects against sexual transmission of HIV-1 and suggest that sperm might reach DCs by passing through microabrasions in the vaginal or anal lining that often form during intercourse.

A. Ceballos et al., Spermatozoa capture HIV-1 through heparan sulfate and efficiently transmit the virus to dendritic cells. J. Exp. Med. 2 November 2009 (10.1084/jem.20091579) [Abstract]

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