Session 60Poster Presentations Primary HIV/SIV Infection Session Day and Time: Tuesday 1:30 - 3:30 pm Room: Hall A
505 The Relative Transmissibility of Drug Resistant HIV-1 among Couples R. M. Grant*1,2, R. Atchison1, K .Franses2, A .Rollins2, M .Warmerdam1, J. O. Kahn2, F. M. Hecht2 1Gladstone Inst of Virology and Immunology, San Francisco, CA and 2Univ of California at San Francisco
Background: Case series indicate that drug resistant HIV-1 can be transmitted, although the relative transmissibility is unknown. Partner studies directly assess the transmission of drug resistant viral mutants after well-characterized exposure.
Methods: The Options project evaluated persons who were recently exposed to HIV-1 and their infected sexual partners. Recently exposed persons were determined to have acute or early HIV-1 infection based on evolving serology. Transmitting and spread partners were distinguished based on medical history and duration of infection. Non-transmitting partners were identified if at least one partner remained uninfected after unprotected intercourse. Resistance was assessed in genotypic and phenotypic assays. Virological linkage of source and spread cases was defined using bootstrap analysis of phylogenetic trees of pro, pol, gag or env sequences.
Results: Viral phylogenetic linkage was established in 35 partnerships, thereby identifying 33 transmitting partners. In addition, 41 non-transmitting partners of seronegative persons were identified. Among partners with viral load > 1000 cpm, PI resistance was evident in 3/33 (9%) of the transmitting partners and 6/26 (23%) of the non-transmitting partners (p = 0.09). Resistance associated with nRTIs and nnRTIs was comparable in transmitting (17% and 20%) and non-transmitting partners (15% and 15%). Among the transmitting source partners with evidence of drug resistance in blood plasma, some of the resistant mutants were transmitted in all 9/9 transmission events, and all of the drug resistant mutants were transmitted in 7/9 (78%). One source partner did not transmit a RT K65R mutant and another did not transmit a RT K103N mutant. An additional source partner transmitted an nRTI resistant virus to one partner and, after stopping therapy, transmitted a drug susceptible virus to another partner.
Conclusions: There was no evidence of transmission of drug susceptible HIV-1 from sources with drug resistant viremia in these couples. The prevalence of PI resistance tended to be lower in transmitting partnerships, compared with non-transmitting partnerships, suggesting that certain types of drug resistance may decrease infectiousness.
