CROI 2018 Abstract eBook

Abstract eBook

Poster Abstracts

deficient viruses was rescued by delivery of Vpr in trans. Importantly, expression from uDNA is stably maintained over time in macrophages in a Vpr-dependent manner. Mutations in Vpr that ablate its association with the Cul4A-DCAF-DDB1 ubiquitin ligase (Q65R and H71R) or prevent Vpr-induced DNA damage response (R90K) reduced viral gene expression from uDNA. Furthermore, the ability of Vpr to enhance transcription from uDNA was conserved amongst Vpr alleles from SIVsmm/SIVmac/HIV-2 lentiviral lineage. Conclusion: Together, our data suggests an evolutionarily conserved role for Vpr in enhancing expression from uDNA which may contribute to persistence of virus reservoir in vivo, even in the continued presence of HIV integrase inhibitors. 191LB A NOVEL MODE OF RNA BINDING ASSISTS APOBEC3H IN THE MOLECULAR ARMS RACE AGAINST HIV Jennifer Bohn 1 , Keyur Thummar 2 , Ashley York 2 , Alice Raymond 2 , William C. Brown 1 , Paul Bieniasz 2 , Theodora Hatziioannou 2 , Janet L. Smith 1 1 University of Michigan, Ann Arbor, MI, USA, 2 The Rockefeller University, New York, NY, USA Background: Several members of the APOBEC3 family of cytidine deaminases cause lethal hypermutation of retroviruses and retroelements via deamination of newly reverse-transcribed single stranded DNA (ssDNA). Their ability to bind RNA is essential for virion infiltration and antiviral activity, yet the mechanisms of viral RNA recognition are unknown. Methods: By screening naturally occurring, polymorphic, non-human primate APOBEC3H (A3H) variants for biological and crystallization properties, we obtained a 2.24-Å crystal structure of pig-tailed macaque A3H bound to RNA. Results: We found that A3H forms a dimer around a short, A-form RNA duplex both in vitro and in virions, a property that allows for A3H to identify and bind to sequences in the viral genome for efficient virion incorporation. Despite the bound RNA, A3H has both potent cytidine deaminase activity and high affinity for the ssDNA target, suggesting that both DNA and RNA may bind to A3H simultaneously. Conclusion: In addition to facilitating virion incorporation, we propose a mechanism by which A3H may selectively bind to A-form duplexes, such as an RNA-DNA heteroduplex, to facilitate delivery of short-lived ssDNA to the deaminase active site immediately following reverse transcription. 192 INFANT T/F HIV-1 FROM PERIPARTUM TRANSMISSION ARE RESISTANT TO MATERNAL PLASMA Amit Kumar 1 , Claire E. Smith 2 , Elena E. Giorgi 3 , Joshua A. Eudailey 1 , David R. Martinez 1 , Karina Yusim 3 , Ayooluwa O. Douglas 1 , Lisa Stamper 1 , Genevieve Fouda 1 , Erin McGuire 1 , Celia C. Lebranche 2 , David C. Montefiori 2 , Feng Gao 2 , Sallie Permar 1 1 Duke Human Vaccine Institute, Durham, NC, USA, 2 Duke University, Durham, NC, USA, 3 Los Alamos National Laboratory, Los Alamos, NM, USA Background: Mother to child transmission of HIV-1 involves selective transmission of 1 or a few viral variants. These infant transmitted/founder viruses are of particular interest, as a maternal or infant vaccine must block this group of viruses. Yet, the role of maternal autologous virus-neutralizing antibodies in selecting for infant T/F viruses is not well understood. Methods: Sixteen peripartum transmitting HIV-1 mothers and paired infant plasma samples were selected from the Women and Infants Transmission Study, an ART naïve cohort. Single genome amplification method was used to obtain HIV Env genes frommother and infant samples. Maternal and infant SGAs were sequenced and analyzed using phylogenetic tree and highlighter plots. Infant T/F viruses were identified in all 16 peripartum infected infants and were cloned and generated as pseudoviruses. Pseudoviruses for non-transmitted maternal variants were also generated by overlap PCR method. The neutralization sensitivity of maternal and infant T/F viruses was assessed against maternal and infant plasma, and a panel of broadly neutralizing antibodies (bNAbs). Signature sequence analysis was performed to identify amino acid motifs predictive of autologous virus neutralization sensitivity. Results: 62% of infants were infected with 1 T/F, virus while 38%were infected with 2 or more T/F viruses. 85% of infant T/F viruses tested were neutralization resistant to paired maternal plasma but were at least partially sensitive to HIV-1 bNAbs such as VRC-01, whereas 14-70% of circulating maternal non-transmitted viruses were neutralization sensitive to autologous plasma neutralizing antibodies. Infant T/F were more resistant to paired maternal samples than non-transmitted maternal variants (p = 0.012). In contrast, tiered heterologous

neutralization sensitivity phenotyping of infant T/F viruses demonstrated a range from tier 1a to tier 3, indicating that heterologous plasma neutralization sensitivity does not predict paired maternal plasma neutralization sensitivity of infant T/F viruses. Conclusion: Majority (86%) of infant T/F viruses were neutralization resistant to paired maternal plasma, while non-transmitted maternal viruses were variably resistant to autologous plasma, suggesting that infant T/F viruses are overall more neutralization sensitivity than non-transmitted maternal variants. Therefore, enhancing maternal autologous virus neutralizing antibodies during pregnancy could be a viable strategy to further reduce vertical HIV-1 transmission. 193 ZIKA VIRUS AND HIV-1 INTERPLAY IN HUMAN IMMUNE CELLS Joel Provost , Corinne Barat, Michel J. Tremblay Laval University, Quebec City, QC, Canada Background: Zika virus (ZKV) is an emerging pathogen that can lead to fetal abnormalities and death in utero. As cellular targets of ZKV in the blood are presently unknown, this project aims to gather information on this issue. Furthermore, as ZKV infections occur in regions endemic for HIV-1, the potential consequences of ZKV/HIV-1 coinfections must be explored. Methods: Subpopulations of blood leukocytes were separated from blood of healthy donors using commercial kits and macrophages were differentiated frommonocytes. ZKV was titrated using a standard plaque assay on VERO cells. HIV-1 infection was performed using a molecular clone expressing a GPI- anchored reporter (NL4-3 BALenv IRES HSA) allowing detection of infected cells by flow cytometry. Viral production was determined by a p24-specific ELISA. Percentage of ZKV-infected cells were determined by immunofluorescence. The role of autophagy on ZKV replication was evaluated by treating cells with a specific and potent inhibitor of autophagy (SPAUTIN-1). Target-specific siRNAs were used to identify potential cell surface receptors of ZKV attachment/entry. Results: No replication of ZKV was observed in NK cells, CD4+ T lymphocytes, monocytes, and neutrophils. However, replication of ZKV could be observed following infection of MDMs with PL_Cal strain, which peaked at 7-9 days post- infection. Different strains of ZKV displayed different kinetics of replication. Coinfection between HIV-1 and ZKV in MDMs show that while HIV-1 replication is unaffected by coinfection with ZKV, ZKV replication is strongly inhibited by prior exposure of MDMs to HIV-1. Finally, results show that ZKV is highly sensitive to type I IFN released by MDMs exposed to HIV-1. Conclusion: Among the primary human cells studied, only MDMs were susceptible to infection by ZKV. In our experimental model, production of ZKV by MDMs could be sustained over an extended period. This deserve more attention as infectious ZKV can be recovered from semen for as long as 6 months following infection. MDMs could thus harbor ZKV in peripheral tissues and allow its transmission long after acute infection is cleared. A better comprehension of the cellular targets of ZKV and its potential interactions with other pathogens will provide a stronger rational basis for the design of new drugs and therapies for ZKV-infected individuals and the relative importance of coinfections for the treatment of each condition.

Poster Abstracts

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CROI 2018