CROI 2020 Abstract eBook

Abstract eBook

Poster Abstracts

914 USING MOLECULAR EPIDEMIOLOGY TO CHARACTERIZE HIV TRANSMISSION NETWORKS OF TW AND MSM

915 PHYLOGENETIC EVIDENCE OF HIV-1 MIXING BETWEEN KEY RISK GROUPS IN COASTAL KENYA NDUVA M. GEORGE 1 , Amin S. Hassan 2 , Susan M. Graham 3 , Joakim Esbjörnsson 4 , Eduard Sanders 2 1 KEMRI Wellcome Trust Rsr Prog, Kilifi, Kenya, 2 KEMRI–Wellcome Trust Research Programme, Kilifi, Kenya, 3 University of Washington, Seattle, WA, USA, 4 Lund University, Lund, Sweden Background: HIV-1 transmission patterns within and between populations at high-risk of HIV-1 acquisition in Kenya are not well understood. We investigated HIV-1 subtype distribution and transmission dynamics in men who have sex with men (MSM), injecting drug users (IDU), female sex workers (FSW) and heterosexuals (HET) in coastal Kenya. Methods: We used maximum-likelihood and Bayesian phylogenetics to analyse new (N=163) and previously published (N=495) HIV-1 pol sequences collected 2005-2019 from treatment naïve individuals. To perform a subtype- specific cluster analysis of the coastal Kenyan sequences, we obtained reference sequences (N=1079) from GenBank based on similarity. Transmission networks were classified based on the number of sequences per cluster into dyads (2 sequences), networks (3-14 sequences) and large clusters (>14 sequences). Temporal and phylodynamic analyses were performed using a Bayesian Markov Chain Monte Carlo approach. Results: Of 658 sequences, 131 (20%) were MSM, 58 (9%) IDU, 109 (17%) FSW, and 360 (55%) HET. The majority (66%) of the sequences were sub-subtype A1, with lower fractions of subtypes D (10%), C (7%), G (<1%), and recombinant forms (17%). Overall, 206 (31%) sequences formed 39 dyads, 21 networks, and one large cluster. Most clusters (85%) consisted of sequences from the same transmission group, indicating frequent within-group transmission. However, 15% of the clusters were mixed between MSM, FSW and HET sequences. One large IDU cluster was found, suggesting that HIV-1 was introduced from a single source followed by fast spread within the IDU population, distinguishing IDU transmission relative to other risk groups. Phylodynamic analysis of the sub- epidemic among IDU indicated a steady increase in HIV-1 infections from the origin of the cluster in 1987. Conclusion: Our work suggests that in addition to frequent transmission within-risk-groups, HIV-1 transmission between MSM, FSW and HET is also common in coastal Kenya. Targeting HIV-1 prevention programmes to FSW, MSM and IDU will be necessary to reduce HIV-1 transmission in coastal Kenya.

Jessica E. Long 1 , Joshua T. Herbeck 1 , Hugo Sanchez 2 , Sari Reisner 3 , Kenneth H. Mayer 4 , James Mullins 1 , Javier R. Lama 5 , Ann Duerr 6 1 University of Washington, Seattle, WA, USA, 2 Epicentro, Lima, Peru, 3 Harvard T.H. Chan School of Public Health, Boston, MA, USA, 4 The Fenway Institute, Boston, MA, USA, 5 Asociacion Civil Impacta Salud y Educacion, Lima, Peru, 6 Fred Hutchinson Cancer Research Center, Seattle, WA, USA Background: Transgender women (TW) are highly vulnerable to HIV, yet little is known about their sexual networks. TW are often conflated with men who have sex with men (MSM), with the implicit assumption that the sexual networks of MSM and TW overlap, resulting in HIV transmission between the populations. However, sex partners of TW (PTW) are largely cisgender men who have sex with cis- and transgender women, suggesting that the sexual networks of MSM and TW/PTWmay be separate. We examined the genetic similarity of HIV sequences from TW, male PTW, and MSM from research cohorts in Lima, Peru to determine whether the imputed transmission network, and therefore the sexual network, of TW/PTW overlaps with that of MSM. Methods: We used HIV-1 pol sequences and epidemiologic data collected through 3 research studies conducted among primarily high-risk MSM, TW, and PTW in Lima from 2013–2017. A transmission network and phylogenetic tree were constructed using all study sequences (n=303 MSM, n=139 TW, n=25 PTW) as well as all South American sequences from the Los Alamos HIV Database (n=552). Molecular clusters were identified within the transmission network, with cluster membership defined as ≥2 sequences linked to each other based on a TN93 pairwise genetic distance threshold of 0.015 substitutions/site, and patterns in clustering were assessed with chi squared tests. Results: 200 participants (43%) were found in 62 clusters (Fig 1), with no difference in probability of clustering by group. Both MSM and TWwere more likely to cluster with members of their own group than would be expected based on chance alone. While only 28% of the sample were TW, 77% of TW found in a cluster were clustered with TW (p<0.001). Similarly, while 67% of the sample were MSM, 91% of clustered MSM were found in clusters with MSM (p<0.001). TWwere less likely to be found in clusters with MSM than would be expected (57% observed vs 67% expected, p=0.086), but frequency of co-clustering of TW and MSM did suggest transmission occurring between the two populations. No characteristics were predictive of men clustering with TW, including reporting a TW sex partner. Conclusion: Co-clustering of TW/MSM was less common than expected but still signified sizable overlap in transmission networks. This contrasts with reported sexual behavior among TW and their sex partners, and may indicate that a subset of high-risk men who have sex with both TW and men drive HIV transmission between these two populations.

Poster Abstracts

916 PHYLODYNAMIC EVIDENCE OF HIV TRANSMISSION BETWEEN AGE- DISCREPANT MSM IN KING COUNTY Diana M. Tordoff 1 , Roxanne P. Kerani 1 , Matthew R. Golden 1 , Richard Lechtenberg 2 , Susan E. Buskin 2 , Joshua T. Herbeck 1 1 University of Washington, Seattle, WA, USA, 2 Public Health–Seattle & King County, Seattle, WA, USA Background: Sexual mixing is typically age-assortative. Mathematical modeling studies conducted in the 1990s suggested an important role for age-disassortative mixing in HIV transmission dynamics among men who have sex with men (MSM), suggesting that young MSM (YMSM) may acquire HIV from older partners. We compared molecular epidemiology methods with phylodynamic methods to examine the frequency of HIV transmission between age discrepant MSM.

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