CROI 2015 Program and Abstracts

Abstract Listing

Poster Abstracts

TUESDAY, FEBRUARY 24, 2015 Session P-B2 Poster Session

Poster Hall

2:30 pm– 4:00 pm Defining Epidemiologically Linked Transmission 238 Large Phylogenetically Linked HIV Cluster in King County, Washington, 2008 to 2014 Susan E. Buskin 1 ; JoshuaT. Herbeck 2 ; Katelynne M. GardnerToren 1 ; Michelle R. Perry 1 ; Amy Bennett 1 ; Matthew R. Golden 2 1 Public Health—Seattle & King County, Seattle, WA, US; 2 University of Washington, Seattle, WA, US

Background: Core transmission is a basic tenant of sexually transmitted infection (STI) epidemiology—that a few individuals are responsible for a large proportion of STI transmissions. However, relatively little data exist on core transmission for HIV. We present phylogenetic analyses supporting the role of a core transmitter of HIV infection. Methods: Public Health – Seattle & King County (PH) field services staff identified an individual (index case) diagnosed with HIV infection in 2008 and who was named as a potential transmitting sex partner by 11 different men between 2008 and 2014. We used PH HIV-1 pol nucleotide sequences collected by Molecular HIV Surveillance for HIV cases diagnosed 1/08 to 9/14 to assess the phylogenetic relatedness of people naming the index case as a sex partner, and to define the size of the associated transmission cluster. Results: Phylogenetic data were available for 10 of 12 men identified through field services investigations. Seven of the 10 epidemiologically-linked cases were phylogenetically linked in a cluster of 66 cases; this was the largest subtype B cluster identified in the area, comprising 5%of 1430 sequences analyzed over the period of observation. Of the 66 cluster cases, 7 including the index case were diagnosed in 2008, 5 in 2013, and 3 (to-date) in 2014; the modal year was 2012 with 17 diagnoses. All but 1 case was male, and 94% reported sex with men. All 66 cluster cases had primary high-level non-nucleoside reverse transcriptase (NNRTI) resistance; these 66 are 36%of all NNRTI resistant cases in the time period. Sequences from the 66 cluster cases were collected 0 to 485 days fromHIV diagnosis (median 16 days); none had achieved viral suppression prior to specimen collection. Amost recent viral load was suppressed (< 200 copies per ml) for 54 individuals (82%). Of the remaining 12 individuals, 5 had > 1 log reduction in viral load (range 1.6 to 3.8), one individual relocated, and the remaining 6 are under investigation but are not known to be virologically suppressed. The index case was not previously virally suppressed, but was successfully relinked to care by PH. Conclusions: This large cluster of epidemiologically and molecularly-related cases supports the role of core transmission in HIV infection. The ability of field services staff to identify an untreated man who we believe played a central role in this transmission network demonstrates the utility of routine partner services investigations. 239 Reconciling Named Partner and Genetic Partner HIV-1 Transmission Networks in New York City Joel O. Wertheim 1 ; Sergei L. Kosakovsky Pond 1 ; Konrad Scheffler 1 ; Davey M. Smith 1 ; Sanjay Mehta 1 ; Sharmila Shah 2 ; Lisa Forgione 2 ; LuciaV.Torian 2 1 University of California San Diego, San Diego, CA, US; 2 New York City Department of Health and Mental Hygiene, New York, NY, US Background: The New York City Department of Health and Mental Hygiene (DOH) interviews persons with newly diagnosed HIV infection (index cases) and elicits partners, who are notified of exposure and offered HIV testing. When resistance testing is ordered by a physician with whom the case or positive partner has initiated care, the viral nucleotide sequence is reported to surveillance. Methods: Between 2006 and 2012, DOH interviewed 770 index cases with genotypes; these cases named 810 HIV+ partners with genotypes, for a total of 1,369 cases linked to named partners (211 index cases were also named by other index cases). Using pol sequences, we identified index and named partners who were closest relatives in a maximum likelihood phylogeny. We then estimated the Tamura-Nei 93 (TN93) genetic distance between each pair of index cases and named partners. We designated viral sequence pairs that fell below a validated distance cutoff of 1.75% as genetic links. Our data made it possible to construct two networks: the network of cases and their named partners (the named partner network; N=1,369) and the network of clusters of persons genetically linked by their TN93 distance (the genetic partner network; N=862 [63% of the 1369 cases]). We examined the degree of overlap between the two networks. We used logistic regression to assess the variables associated with the index case successfully naming at least one genetically linked partner. Results: 451 of 770 (59%) index cases named partners who were also genetically linked (Table). Heterosexual female index cases were more likely to be genetically linked to a named partner (77%) than men who have sex with men (42%, OR=0.21, 95% CI 0.14, 0.31) and male injecting drug users (38%, OR=0.18, 95% CI 0.08, 0.38). Black index cases were less likely than whites and Hispanics to name a genetically linked partner (53%, OR=0.46, 95% CI 0.25, 0.87). In the named partner network, 747 out of 1,369 (55%) cases were genetically linked to a named partner, whereas in the genetic network, 720 out of 862 (84%) persons were genetically linked to a named partner.

Poster Abstracts

Conclusions: Construction of genetic transmission networks can supplement partner naming by identifying previously unknown parts of a potential transmission network, i.e., unnamed partners. If real-time genotyping coupled with network analysis can be implemented, it can be used to interdict ongoing transmission and to improve epidemic control.

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CROI 2015