CROI 2015 Program and Abstracts

Abstract Listing

Poster Abstracts

Figure 1 - The mean branch lengths of clusters in a simulated growing epidemic (blue) and simulated shrinking epidemic (pink). The clusters in the shrinking epidemic had a highly significant increase in overall branch length (p < 2x10e-16). Conclusions: We have generated simulated data sets of viral sequences corresponding to samples from hypothetical, generalized HIV-1 epidemic scenarios in sub-Saharan Africa. Initial results show the power of phylogenetic tools to detect changes in incidence and prevalence in the context of generalized HIV epidemics. Further development will focus on using the simulations to test the sample density required by different methodologies to reveal underlying changes in epidemic dynamics.

TUESDAY, FEBRUARY 24, 2015 Session P-B4 Poster Session 2:30 pm– 4:00 pm Transmission Networks: MSM 250 HIV Transmission Among Seattle Adolescents

Poster Hall

Joshua Herbeck 1 ; ElizabethWolf 1 ; Stephen van Rompaey 2 ; Mari M. Kitahata 2 ; Lisa Frenkel 1 1 University of Washington, Seattle, WA, US; 2 Center for AIDS Research, Seattle, WA, US Background: Phylogenetic analyses of HIV gene sequences can be used to infer putative transmission clusters, with associated individual characteristics used to identify risk factors for HIV transmission. We hypothesized that HIV-infected adolescents would be linked to clusters of infected adults. Methods: Data from time of first HIV genotyping for drug-resistance, including demographics (age, sex, race), HIV transmission risk (men who have sex with men (MSM), MSM & intravenous drug use (IDU), IDU, heterosexual), and homelessness were obtained from the University of Washington (UW) HIV Information System and retrospective chart review. HIV pol sequences were obtained from the UW Clinical Virology Laboratory. Phylogenetic clusters were defined as sequences with a shared ancestral node, support values >95% and pairwise genetic distances ≤ 0.015 nucleotide substitutions per site. The characteristics of all individuals found in clusters were compared to those of non-clustering individuals using multivariable logistic regression. This process was repeated for clusters with ≥ 1 adolescents (defined at age 13-24 year at first genotyping). Results: There were 3116 total HIV-1 pol sequences from 1960 individuals, including 115 adolescents, genotyped between February 1, 2000 and March 1, 2013. Fifty-four phylogenetic clusters (containing 169 individuals) were identified. In unadjusted analyses, significant associations existed between cluster membership and adolescent age, MSM, and MSM&IDU. In adjusted analyses including transmission risk group, sex, homelessness, and age class at sequencing (adolescent or adult), adolescent age, MSM and MSM&IDU remained significantly associated with cluster membership. Fifteen clusters were identified that included ≥ 1 adolescent; adolescents were 75%male, 57%MSM, 7% IDU, and 12%MSM&IDU. Considering those individuals in these clusters that were not adolescents (i.e. individuals that were adults), there was a non-significant positive association between MSM risk group (adults) and cluster membership. Conclusions: This study suggests that MSM and MSM&IDU adolescents are at particularly high risk of HIV infection and may require specialized HIV prevention services. 251 Characterization of Large Cluster Viral Networks Sustaining the Montreal MSM Epidemic Background: This study combined phylogenetic, molecular recency, virological and behavioral data to identify key determinants favoring the ongoing genesis of large viral lineages sustaining the Montreal Men having Sex with Men (MSM) epidemic despite widespread antiretroviral therapy coverage and population declines in viral load. Methods: Phylogenetic analysis ascertained the genetic interrelatedness of MSM viral sequences (2002-2013), first genotyped in primary HIV infection (PHI, 0-6 months, n= 1304) or chronic-untreated (CUN) stage infection (>6 months, n= 1809). Molecular recency assays based on sequence nucleotide ambiguity was nused to estimate recency of infection. Patterns of viral spread were stratified into four distinct groups based on cluster size (1, 2-4, 5-9, 10-91 infections/cluster). PHI cohort participant data ascertained partnership risk behaviour and viremia in four cluster groups. The SPOT rapid testing site cohort determined testing propensity and partnership risk among MSM. Results: Over the last decade, MSM infections included 1168 solitude transmissions (37%), 244 small clusters (2-4 infections, n=573, 18%), 65 large clusters (5-9 infections, n= 403, 13%), and 45 large cluster (10-91, median 25 infections, n=969, 31%) network. The episodic genesis and spread of clusters was related to primary infection (27%, 46%, 50% and 54%, odds-ratio 1, 2.33, 2.81, 3.33, respectively). Viral lineages associated with unique, small, large (5-9) and (10-91) cluster groups showed significant differences in weighted sequence ambiguity (0.40%, 0.27%, 0.20%, 0.13%, respectively). PHI cohort data revealed extended viremia over 24 months in lineages associated with large cluster networks. The MSM epidemic is growing in younger populations, with 14%, 18%, 27%, and 32% of unique, small, large (5-9) and large (10+) below 30 years of age, respectively. PHI cohort data Bluma Brenner 2 ; Ruxandra-Ilinca Ibanescu 2 ; Daniela Moisi 2 ; Isabelle Hardy 3 ; Jean-Pierre Routy 1 ; Joanne Otis 4 ; MarkWainberg 2 ; Michel Roger 3 1 McGill University, Montréal, Canada; 2 Lady Davis Institute, Montreal, Canada; 3 Université de Montréal, Montreal, Canada; 4 UQAM, Montreal, Canada

Poster Abstracts

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CROI 2015