CROI 2015 Program and Abstracts

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Poster Abstracts

Results: Of 658 HIV1+ specimens, Geenius classified 654 (99.4%) as HIV1+, 1 as HIV-, 1 as HIV-1 indeterminate (HIV-1 IND), and 2 as HIV-positive “untypeable.” (Both these specimens were initially positive for both HIV-1 and HIV-2 with MS, but classified as HIV-1 after dilution). Thirteen additional HIV1+ specimens that were positive for both HIV-1 and HIV-2 by MS before dilution were positive for HIV-1 only by Geenius. One of 8 acute HIV specimens was HIV-2 IND by Geenius and HIV- by MS; all others were HIV- with both tests. Of the 181 HIV- specimens with a reactive non-MS screening test result, 165 (91.2%) were classified as HIV- by Geenius; one of the remaining 16 was classified as HIV1+. Of 31 HIV- specimens with a reactive MS screening result, 24 were classified as HIV- by Geenius; none were concordantly reactive with MS and HIV-1 positive by Geenius. The majority of the non-negative Geenius results were HIV-2 IND (Table). All HIV- specimens categorized as HIV-2 IND were attributable to reactivity at the gp140 HIV-2 peptide line only. Comparison of Geenius and Multispot HIV-1/HIV-2 differentiation assay results for 207* specimens classified as HIV-negative by the CDC algorithm for laboratory diagnosis of HIV infection but reactive by one or more HIV screening tests

*207 specimens with false-reactive results on one or more HIV screening tests were obtained from a previous study of 4500 HIV-negative specimens. ** Multispot supplemental test interpretation: reactivity at both HIV-1 spots required for positive; reactivity at only one of two HIV-1 spots is considered indeterminate; reactivity at both HIV-1 and HIV-2 spots is considered HIV-1/HIV-2 undifferentiated. ***Multispot screening test interpretation: any reactivity at any spot is considered reactive; the 31 include 5 with reactivity to another HIV-1/HIV-2 screening assay Conclusions: The ability of the Geenius to detect established and early HIV infection is similar to the MS currently used in the CDC algorithm, but more IND results, particularly HIV-2 IND results, occur with Geenius. 622 The Effect of HIV-1 Subtype A, C and D on Cross-Sectional Incidence Assay Performance Andrew F. Longosz 2 ; Mary Grabowski 2 ; Charles S. Morrison 3 ; Ronald H. Gray 2 ; Connie Celum 4 ; Quarraisha Abdool Karim 5 ; Hilmarie Brand 6 ;Thomas C. Quinn 1 ; Susan H. Eshleman 2 ; Oliver B. Laeyendecker 1 1 National Institute of Allergy and Infectious Diseases, Baltimore, MD, US; 2 Johns Hopkins University, Baltimore, MD, US; 3 FHI 360, Durham, NC, US; 4 University of Washington, Seattle, WA, US; 5 CAPRISA, University of KwaZulu-Natal, Congella, South Africa; 6 SACEMA, Stellenbosch University, Stellenbosch, South Africa Background: We examined the impact of HIV subtype A, C and D on the performance of serologic cross-sectional HIV incidence assays. Methods: Three assays were evaluated: the limiting antigen avidity enzyme immunoassay (LAg-Avidity assay), the BED capture enzyme immunoassay (BED-CEIA), and an avidity assay based on the Genetic Systems 1/2 + O ELISA (BioRad-Avidity assay). We evaluated 4,821 plasma and serum samples from individuals known to be infected with HIV-1 subtypes A, C and D from 6 different cohort studies in Zimbabwe, Uganda, South Africa, Kenya, Zambia and Botswana. This study included 2,045 subtype A samples (212 samples from the 2008-2009 Rakai Community Cohort Study (RCCS) and 1,833 samples from the Ugandan Genital Shedding (GS) Study. 1,697 subtype C samples (329 samples from the Ugandan and Zimbabwean GS Studies, 85 samples from HPTN 039, 727 samples from the Partners in Prevention Study and 556 samples from the CAPRISA 004 Trial Group) were analyzed. 1,079 subtype D samples (781 samples from the Ugandan Genital Shedding (GS) Study and 298 samples from the 2008-2009 RCCS) were tested. Date of HIV seroconversion was defined as either the midpoint between the last negative and first positive HIV antibody test, or fifteen days after acute infection was documented (defined as HIV RNA positive / HIV antibody negative). Viral load and HIV-1 subtype data were determined previously in parent studies. Mean duration of recent infection (MDRI) was calculated for subtypes A, C and D using a time window of two years post-seroconversion. To define recent infection, assay cutoffs of 1.5 normalized optical density (OD-n), 0.8 OD-n and 40% avidity index (AI), were used for the LAg-Avidity assay, BED-CEIA, and Bio-Rad-Avidity assay respectively. The false recent rate (FRR), the fraction of samples misclassified as recent, was calculated for all samples and those with detectable viral loads (>400 cps/ml). Results: There were significant differences for MDRI and FRR estimates by subtype for all three assays (see Table). The largest differences in MDRI were seen for the LAg-Avidity and BED-CEIA assays between subtypes A and D. FRR results were significantly higher for subtype D for all three assays.

Poster Abstracts

392

CROI 2015