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Volume 6 Supplement 3

AIDS Vaccine 2009

0A06-01. Multiplicity of infection by HIV-1 in injection drug users, men who have sex with men and heterosexuals


We have recently shown that transmitted/founder virus(es) can be identified unambiguously using single genome amplification (SGA) (Keele, PNAS, 2008; Salazar, JEM, 2009) and that in heterosexual transmissions approximately 80% of patients are infected by a single virus or infected cell (Keele, PNAS, 2008; Haaland, PLoS Pathogens, 2009; Abrahams, JVirol, 2009). Here we explore the characteristics of virus transmission in men who have sex with men (MSM) and injection drug users (IDU).


Full-length env sequences were derived by SGA from plasma vRNA from 30 acutely infected MSM and 11 IDU from North America. Modes of infection were determined by self-report. Uncloned amplicons were sequenced, aligned, and analyzed by neighbor-joining phylogenies and the Highlighter tool.


Maximum within-patient diversity ranged from 0.08–7.12%. In the MSM group, 19 of 30 (63%) acutely infected subjects had evidence of a single transmitted/founder (t/f) virus and 11 of the 30 had evidence of transmission by a minimum of 2–10 viruses. In the IDU group, 4 of the 11(36%) had evidence of a single t/f virus, while the remaining 7 demonstrated transmission by a minimum of 3–19 variants. In the subjects with multiple transmissions, the median number of t/f variants was 3 for MSM and 5 for IDU. Differences in single versus multiple virus transmissions among HSX, MSM and IDU were statistically significant (p < 0.006).


The HIV-1 transmission event is different in HSX, MSM and IDU. We see single variant transmission in approximately 80% of HSX, 60% of MSM and 40% of IDU. When multiple transmissions occur, they tend to have a higher number of variants in IDU than in MSM or HSX. These findings indicate that risk of HIV-1 acquisition correlates with numbers of transmitted viruses. This, along with the phenotypic properties of these viruses (especially Env), may be important in vaccine design and assessment.

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Open Access This article is published under license to BioMed Central Ltd. This is an Open Access article is distributed under the terms of the Creative Commons Attribution 2.0 International License (, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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Bar, K., Li, H., Keele, B. et al. 0A06-01. Multiplicity of infection by HIV-1 in injection drug users, men who have sex with men and heterosexuals. Retrovirology 6 (Suppl 3), O37 (2009).

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