INTRODUCTION Differentiating between HIV-1 and HIV-2 infection is the first step to understanding HIV transmission, epidemiology and pathogenesis in geographical areas where both viruses circulate. In Cuba, positive results in mixed HIV-1/2 screening assays are confirmed by HIV-1 Western blot. Indeterminate results constitute the main limitation of this test and HIV-2 infection is among their possible causes; hence the importance of second-stage screening and confirmatory tests for HIV-2 infection.

OBJECTIVE Investigate the contribution of HIV-2 antibodies to negative or indeterminate HIV-1 Western blot results in serum samples from 2005 through 2008 in Cuba.

METHODS HIV-2 reactivity was studied using the ELISA DAVIH–VIH-2 diagnostic kit (Cuba) in 1723 serum samples with negative or indeterminate results for HIV-1 Western blot from January 2005 through December 2008. Duplicate sera reactive by ELISA were confirmed by HIV-2 Western blot, results interpreted according to WHO criteria. The epidemiological interview established by Cuba’s National Program for Prevention and Control Sexually-Transmitted Diseases and HIV/AIDS was applied to HIV-2 Western blot-positive patients.
RESULTS Among all sera studied, HIV-2 ELISA identified 12 reactive serum samples (0.70%) and 1711 non-reactive (99.30%). Western blot analysis of the 12 ELISA-reactive samples confirmed two positive samples (16.67%), 4 negative (33.33%) and 6 indeterminate (50%). Positive samples reacted against the p16, p26, gp36, p53, p56, p68 and gp105 proteins. All 12 ELISA-reactive samples belonged to the HIV-1 Western blot indeterminate group. The two HIV-2–positive samples showed well defined reactivity to gp160, p53, p55 and p34 of HIV-1. HIV-1 seroconversion was observed in all 10 remaining samples during serological followup.

CONCLUSIONS Two new HIV-2 seropositive cases were diagnosed using DAVIH–VIH-2 and HIV-2 Western blot in indeterminate HIV-1 Western blot samples. Results support the recommendation that HIV-2 Western blot be included in the diagnostic algorithm for HIV-1/2 to followup negative or indeterminate HIV-1 Western blot results.

KEYWORDS Diagnosis, laboratory techniques and procedures, antibodies, HIV-2, Western blot, enzyme-linked immunosorbent assay, algorithm, Cuba

Timely and accurate detection of HIV infection is critical due to the seriousness of AIDS and its impact on individuals and families, the long symptom-free incubation period, the benefits of enrolling patients as early as possible in therapy and follow-up, and as a pillar of population-based prevention strategies aimed at curbing the epidemic. Thus, an essential component of Cuba’s

National HIV/AIDS Program (full title, National Program for Prevention and Control of Sexually-Transmitted Diseases and HIV/AIDS) is laboratory diagnosis,[1,2] based on an extensive laboratory network, effective confirmatory algorithms and quality control with external evaluation.