CROI 2016 Abstract eBook

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Poster Abstracts

Methods: Real-time screening of 141,233 samples, using nucleic acid testing and sequential EIA, identified 330 acute HIV-1 infections, of whom 93%were MSM. Demographic and risk-factor data were collected at baseline by interview and questionnaire. Date of infection was estimated from self-reported sexual exposure. Protease and reverse transcriptase gene sequences from 273 (268 Thai) subjects were retrieved from plasma. Maximum likelihood trees and pairwise genetic distances were generated. A distance of ≤ 1.5% and visual inspections of signature nucleotides were used to identify linked transmission clusters. Results: CRF01_AE was predominant at 86% (234) (N), followed by 8% (21) subtype B and 6% (15) CRF01/B. A West African CRF02_AG, a South African C and a B/C strain were also identified. 13/21 B strains clustered with Thai B’. The 5 non-Thai participants had 3 CRF01_AE, 1 subtype B and 1 CRF01/B. Thirty-three subjects (31 CRF01_AE and 2 B) formed 14 clusters: 11 of 2 , 2 of 3, and 1 of 5 individuals. All clusters represent only Thai MSM and CRF01_AE, but for one cluster of 2 B. Only 2 clusters of 2 are known to be linked. 30/33 clustering subjects live in the Bangkok area. Subjects who clustered were not significantly different from non-clustering participants in terms of age, Fiebig stage, plasma HIV-RNA level, days since exposure, reported drug use at exposure, and number of sexual partners preceding enrolment. Median (range) time between infections was 590 (0-1211) days for the clusters of 2, 158 (84-277) days for the clusters of 3, and 144 (43-194) for the cluster of 5 subjects. Conclusions: The predominance of CRF01_AE sequence clusters suggests local MSM transmission networks. The majority of Bangkok MSM with acute HIV infection in our cohort do not cluster, suggesting that numerous sexual transmission networks contribute to the ongoing epidemic of HIV among MSM in the city. The presence of HIV-1 strains from other regions indicates global transmission networks. 220 Increasing Role of Young MSM to HIV Epidemic Spread and Renewal Oliver Ratmann 1 ; Daniela Bezemer 2 ; Ard van Sighem 2 ; A. M. Pettersson 3 ; Martin Schutten 4 ;Woulter F. Bierman 5 ; Peter Reiss 6 ; Christophe Fraser 1 ; for the ATHENA HIV Observational Cohort 1 Imperial Coll London, London, UK; 2 Stichting HIV Monitoring, Amsterdam, Netherlands; 3 VU Univ Med Cntr, Amsterdam, Netherlands; 4 Erasmus Univ Med Cntr, Rotterdam, Netherlands; 5 Univ Med Cntr Groningen, Univ of Groningen, Groningen, Netherlands; 6 Amsterdam Inst for Global Hlth and Develop, Amsterdam, Netherlands Background: In the Netherlands, the age at diagnosis amongst men having sex with men (MSM) has been continually increasing from 37 years in 1996 to 41 years in 2013. This challenges the perception that young, high-risk MSM are the predominant source of infection in high-income countries. Using in depth records from the Netherlands’ ATHENA HIV observational cohort, we previously identified and characterized 617 transmission events to MSM with evidence for recent infection (12 months) at time of diagnosis. Here, we use this cohort to evaluate the sources of the ongoing MSM epidemic in the Netherlands by age, date of birth, and diagnosis status. Methods: 903 probable transmitters to 617 recipients with date of diagnosis between 1996 and 2010 were identified through phylogenetic analysis. Demographic and clinical data from the ATHENA cohort were used to characterize these transmission events in detail. Statistical modelling adjusted for sampling and censoring biases. The proportion of transmissions attributable to age/birth groups was calculated by averaging individual-level viral phylogenetic transmission probabilities across recipients. Limited sequence coverage required us to restrict this multivariate analysis to 509 transmission events between 2004 and 2010. Results: Figure 1A shows the estimated proportion of transmissions by age of the recipient and their probable transmitters. Overall, transmissions were not concentrated within age groups. Further, the age structure of the transmission events in the cohort shifted substantially over calendar time. After 2008, men aged < 28 years continued to be infected from older men, and transmitted increasingly amongst peers as well as to older men. After 2008, an estimated 28% of all transmissions originated frommen aged < 28 years, compared to 14% between 2004-2008. This led to a rapid shift to transmissions from younger generations (figure 1B). The proportion of transmissions from undiagnosed transmitters remains high across generations (figure 1B). Conclusions: We evaluated 509 phylogenetically reconstructed transmission events amongst MSM in the Netherlands. The increasing age at diagnosis is a consequence of complex, changing transmission dynamics by age. Young men are increasingly linked within the epidemic and infect relatively more older men than previously. Prevention of new infections to and from young MSM is especially difficult, but must be urgently improved.

Poster Abstracts

221 Differences in Outbreak Size for HIV-1 Non-B Subtypes Amongst MSM in the Netherlands Daniela Bezemer 1 ; Anne Cori 2 ; Oliver Ratmann 2 ; Ard van Sighem 1 ; Peter Reiss 3 ; Christophe Fraser 2 1 Stichting HIV Monitoring, Amsterdam, Netherlands; 2 Imperial Coll London, London, UK; 3 Amsterdam Inst for Global Hlth and Develop, Amsterdam, Netherlands Background: The HIV-1 epidemic amongst men having sex with men (MSM) in the Netherlands is mainly driven by subtype B. Non-B subtypes are found mostly amongst heterosexuals immigrants from Sub-Saharan Africa. Therefore considering a phylogenetic tree of non-B polymerase sequences allows identifying the introductions into the MSM

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CROI 2016