BackgroundAccurate and reliable laboratory methods are needed for estimation of HIV-1 incidence to identify the high-risk populations and target and monitor prevention efforts. We previously described a single-well limiting-antigen avidity enzyme immunoassay (LAg-Avidity EIA) to detect recent HIV-1 infection.MethodsWe describe here further optimization and characterization of LAg-Avidity EIA, comparing it to the BED assay and a two-well avidity-index (AI) EIA. Specimen sets included longitudinal sera (n = 393), collected from 89 seroconverting individuals from 4 cohorts representing 4 HIV-1 subtypes, and sera from AIDS patients (n = 488) with or without TB co-infections from 3 different cohorts. Ninety seven HIV-1 positive specimens were purchased commercially. The BED assay, LAg-Avidity EIA, AI-EIA and HIV serology were performed, as needed.ResultsMonitoring quality control specimens indicated high reproducibility of the LAg-Avidity EIA with coefficient of variation of <10% in the dynamic range. The LAg-Avidity EIA has an overall mean duration of recency (ω) of 141 days (95% CI 119–160) at normalized optical density (ODn) cutoff of 1.0, with similar ω in different HIV-1 subtypes and populations (132 to 143 days). Antibody avidity kinetics were similar among individuals and subtypes by both the LAg-Avidity EIA and AI-EIA compared to the HIV-IgG levels measured by the BED assay. The false recent rate among individuals with AIDS was 0.2% with the LAg-Avidity EIA, compared to 2.9% with the BED assay. Western blot profiles of specimens with increasing avidity confirm accurate detection of recent HIV-1 infections.ConclusionsThese data demonstrate that the LAg-Avidity EIA is a promising assay with consistent ω in different populations and subtypes. The assay should be very useful for 1) estimating HIV-1 incidence in cross-sectional specimens as part of HIV surveillance, 2) identifying risk factors for recent infections, 3) measuring impact of prevention programs, and 4) studying avidity maturation during vaccine trials.

The phenotypic markers of colorectal carcinomas with microsatellite instability have been widely studied and include mucinous or poor differentiation, prominent host response, a circumscribed growth pattern, histologic heterogeneity, and right-sided location. As part of a population-based case-control study of colorectal cancer in northern Israel, we reviewed the pathology and microsatellite status of 528 consecutively diagnosed colorectal cancers. Phenotypic analysis was performed by one pathologist (J.K.G.) and included assessment of grade, mucinous histology (>50%, or focal), histologic heterogeneity, growth pattern, necrosis, and host response. Microsatellite status was determined on microdissected portions of formalin-fixed, paraffin-embedded tissue using a panel of 5 NCI consensus primers. Fifty-two of 528 colorectal carcinomas were microsatellite unstable (9.85%). Multivariate analysis found that >2 tumor infiltrating lymphocytes per high power field (p <0.0001), the lack of dirty necrosis (p = 0.0054), a Crohn's-like host response (p = 0.0064), right-sided location (p = 0.032), well or poor differentiation (p = 0.037), and any mucinous differentiation (p = 0.039) were independent predictors of microsatellite instability. Tumor infiltrating lymphocytes were the single best histologic predictor of microsatellite instability. The absence of dirty necrosis and the presence of well-differentiated tumors and tumors with only focal mucinous differentiation were also important markers for microsatellite instability that have not been emphasized previously. The combination of >2 tumor infiltrating lymphocytes per high power field and/or any mucinous differentiation and/or the absence of dirty necrosis identified all MSI-H tumors in this study.