CROI 2017 Abstract e-Book

Abstract eBook

Poster and Themed Discussion Abstracts

Methods: To ascertain the nature of the replication defects, we passaged replication-defective Alix-binding site mutant viruses and selected for viral isolates containing second- site mutations with near-wild-type replication kinetics. Results: Sequencing of the viral revertants revealed loss-of-function mutations in Vpu and novel mutations in Env. Several second-site mutations conferred full rescue of the original replication-defective Gag mutants in Jurkat T-cells; interestingly, however, these mutants were highly defective for cell-free, single-cycle infectivity. We demonstrate that the Env compensatory mutants alone replicate with wild-type or faster kinetics in Jurkat T-cells; however, they exhibit severe defects in cell-free, single-cycle infectivity. We show that the Env compensatory mutations do not affect Env expression, incorporation, or virus release efficiency. The mutations can rescue a non-budding related replication defect, suggesting that they provide a global rescue of viral fitness in the context of cell-cell transmission. This effect was cell-type dependent, as replication kinetics of the Env compensatory mutants in another T-cell line, CEM 12D7, correlate with the defects in single-cycle infectivity. Additionally, replication kinetics and infectivity of the Env mutants in PBMCs exhibit the same phenotype as in Jurkat T-cells, suggesting a physiological relevance for the mechanism of rescue observed with these Env mutants. Conclusion: While the Env mutations under study here are defective for cell-free transmission, our data suggest that they rescue the replication-defective mutants by enhancing cell-to-cell viral transmission. Cell-to-cell HIV-1 transmission occurs more efficiently and rapidly than infection by cell-free viruses, supporting the relevance of this mode of viral dissemination. These results provide insights into the role of Env in mediating HIV-1 cell-cell transfer. 181LB RESISTANCE TO TYPE I INTERFERONS IS A MAJOR DETERMINANT OF HIV-1 TRANSMISSION FITNESS Shilpa S. Iyer 1 , Frederic Bibollet-Ruche 1 , Scott Sherill-Mix 1 , Gerald H. Learn 1 , Lindsey J. Plenderleith 2 , Andrew G. Smith 1 , Ronnie M. Russell 1 , Paul M. Sharp 2 , Persephone Borrow 3 , Beatrice H. Hahn 1 1 Univ of Pennsylvania, Philadelphia, PA, USA, 2 Univ of Edinburgh, Edinburgh, UK, 3 Univ of Oxford, Oxford, UK Background: Sexual transmission of HIV-1 is an inefficient process, with only one or few variants of the donor quasispecies establishing the new infection. A critical, and as yet unresolved, question is whether the mucosal bottleneck selects for viruses with increased transmission fitness. Here, we characterized 300 limiting dilution-derived virus isolates from the plasma, and in some instances genital secretions, of eight HIV-1 donor and recipient pairs. Methods: Plasma from chronically infected donors and acute recipients were endpoint diluted and incubated with activated CD4+T-cells both in the presence or absence of IFNα2 and IFNβ. For each virus isolate, particle Env content, infectivity, replicative capacity, IFNα2 and IFNβ IC50, residual replication at the maximal IFN dose (Vres) and particle release were determined. Results: 300 limiting dilution-derived virus isolates were phenotypically characterized. Although there were no differences in the amount of virion-associated envelope glycoprotein, recipient isolates were on average 3-fold more infectious (P=0.0001), replicated to 1.4-fold higher titers (P=0.004), were released from infected cells 4.2-fold more efficiently (P<0.00001), and were significantly more resistant to type I interferons (IFNs) than the corresponding donor isolates. Remarkably, transmitted viruses exhibited 7.8-fold higher IFNα2 (P<0.00001) and 39-fold higher IFNβ (P<0.00001) half-maximal inhibitory concentrations (IC50) than did donor isolates, and their odds of replicating in CD4+ T cells at the highest IFNα2 and IFNβ doses were 35-fold (P<0.00001) and 250-fold (P<0.00001) greater, respectively. Interestingly, pretreatment of CD4+ T cells with IFNβ, but not IFNα2, selected donor plasma isolates that exhibited a transmitted virus-like phenotype, and such viruses were also detected in the donor genital tract. Conclusions. These data indicate that transmitted viruses are phenotypically distinct, and selected for their ability to replicate and spread efficiently in the face of a potent innate immune response.In particular, they are distinguished by increased IFN resistance, particularly to IFNβ. 182 IDENTIFICATION OF MAJOR ROUTES OF HIV TRANSMISSION THROUGHOUT MESOAMERICA Antoine Chaillon 1 , Joel O. Wertheim 1 , Santiago Avila-Rios 2 , Ann M. Dennis 3 , Claudia García-Morales 2 , Carlos Mejía-Villatoro 4 , Elsa Y. Palou 5 , Gustavo Reyes-Terán 6 , Sanjay R. Mehta 1 , for the Mesoamerican Project Group 1 Univ of California, San Diego, San Diego, CA, USA, 2 Natl Inst of Respiratory Diseases, Mexico City, Mexico, 3 Univ of North Carolina at Chapel Hill, Chapel Hill, NC, USA, 4 Roosevelt Hosp, Guatemala City, Guatemala, 5 Hosp Escuela Univ, Tegucigalpa, Honduras, 6 Rsr Cntr in Infectious Diseases, Mexico City, Mexico Background: Central America has some of the highest HIV infection rates in the hemisphere. The association between transportation corridors, trade, migration and HIV

Poster and Themed Discussion Abstracts

transmission has been well-documented in other settings. Here, using molecular epidemiologic techniques, we inferred putative clustering of HIV infected individuals sampled from across Mesoamerica, and estimated patterns of viral migration. Methods: 6,092 HIV-1 subtype B partial pol sequences sampled from unique individuals fromMexico (40.7%), Guatemala (24.4%), Honduras (19%), Panama (8.2%), Nicaragua (5.5%), Belize (1.4%) and El Salvador (0.7%) between 2011-2016 were included. Phylogenetic and genetic network analyses were performed to infer putative relationships between HIV sequences. The demographic and geographic associations with clustering were analyzed and plotted using ArcGIS v.10.1 (ESRI, Redlands, CA). Viral migration patterns were inferred using the Slatkin-Maddison approach on 100 iterations of random subsets of equal number of sequences per location. Time to the most common recent ancestor (tMRCA) of the largest clusters were inferred with a Bayesian approach using the BEAST software package. Results: A total of 1,959/6,092 (22.2%) of sequences demonstrated putative linkage with at least one other sequence, forming 682 transmission clusters, [range: 2-89 individuals]. Clustering individuals were significantly more likely to be younger (median age 30 vs 33 years, p<0.01) and men who have sex with men (38.7% vs 30.4%, p<0.01). Sequences from Guatemala (p<0.01) and Nicaragua (p=0.02) were significantly more likely to cluster. Of the 682 clusters, 34 (5%) included sequences frommultiple countries with commonly observed linkages between Mexican and Honduran sequences (Fig.1). Eight of the 682 clusters included more than 10 individuals. These included two clusters with individuals exclusively from Guatemala, comprised of 52 and 89 individuals with a tMRCA of 1993 and 2004 respectively. Viral migration analyses showed that the Central and Southern regions of Mexico and Belize were the major source of HIV throughout the region (p<0.01). We also found evidence of significant major routes of viral migration between regions within Mexico. Conclusion: International clusters were infrequent, suggesting moderate intermix between HIV epidemics of the different Mesoamerican countries. Nevertheless, we observed important sources of transnational HIV spread in the region, including Southern and Central Mexico, and Belize.

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CROI 2017