[Analysis of new HIV-1 infection in MSM with seroconversion determined by limiting antigen avidity enzyme immunoassay].

ABSTRACT

Objective: To evaluate the applicability of limiting antigen avidity enzyme immunoassay (LAg-Avidity EIA, LAg for short) in determining the new HIV-1 infection status of MSM population with seroconversion and make correlation analysis of other biological indicators. Methods: The 15 cases with HIV seroconversion were found in a MSM observation cohort for calculating the HIV prevalence in Zhejiang.The subjects were conducted epidemiological investigation and sampled.The interval of infection time was estimated according to the exposure history and the time of HIV-positive confirmation.LAg, immunoblotting, CD4 cell counting and viral load test were applied in the testing of the related blood samples. McNermar test was conducted for consistency of the two methods. Results: Of 15 cases, the average age was (31.5±8.0) years old, ranging from 24 to 57 years old. The interval of infection time ranged from 40 days to 366 days, and the median was 134 days, with inter-quartile range from 89 to 180 days. A total of 7 cases were classified as new HIV-1 infection by LAg, and 8 cases were classified as chronic infection.The consistent rate was high to 86.67%, and kappa value was 0.73.The samples lacking at least two bands in p31, p51, p66 and gp120 by immunoblotting were determined as recent infection, of which the new infection proportion was significantly higher than that of other samples (P=0.029).There was no statistical difference in the distribution of CD4 counts (P=0.533) and viral loads (P=0.467) between the new infection and chronic infection groups that divided by LAg. Conclusion: By combining with exposure history, the limiting antigen avidity enzyme immunoassay can be used to estimate the new HIV-1 infection.The other biological indicators such as immunoblotting bands, CD4 cell counts and viral loads, can be used as accessory indicators in evaluating the status of new HIV-1 infection.