HIV-2 infection in Guinea-Bissau, West Africa, with special reference to clinical, immunological and epidemiological aspects

Abstract: We have followed a cohort of police officers in Guinea-Bissau between 1990 and 1997 for the study of clinical, immunological and epidemiological aspects of HIV-2 infection. Initially the prevalence of HIV-2 was high (11.6 %) and HIV-1 infection was rare (0.4 %), but over the study period the prevalence of HIV-1 increased significantly whereas the incidence of HIV-1 was relatively stable. For HIV-2, there was a significant decline of the prevalence as well as the incidence. No protective effect of HIV-2 against subsequent HIV-1 infection was observed. In a sentinel surveillance study of pregnant women in Bissau between 1987 and 1997, a similar pattern of increasing prevalence rates of HIV-1 and declining prevalence rates of HIV-2 was found. HIV-2 infection was associated with generalized lymphadenopathy, weight loss > 10 % and prolonged fever or diarrhoea, and the mortality in HIV-2 infected individuals was 6 times higher than in uninfected individuals. CD4 cell counts were significantly lower among HIV-2 positive subjects compared with HIV negative individuals. In HIV-2 infected individuals, there was a gradual decline of CD4 cells in more advanced clinical stages (according to the WHO clinical staging system), reflecting the increasing level of immunosuppression in each stage. Conversely, proviral DNA load was significantly higher in HIV-2 infected AIDS patients compared with asymptomatic carriers. All HIV-2 positive subjects investigated with phylogenetic analyses carried subtype A, regardless of clinical status. In a hospital-based study we found a significant association between severe bacterial pneumonia, sepsis or pyomyositis and HIV-2 infection. CD4 counts were markedly suppressed in the HIV-2 positive patients with any of these three bacterial infections, and the mortality was significantly higher in sepsis and pyomyositis among HIV-2 positive patients than in HIV negative patients. In contrast, the clinical outcome in patients with pneumonia was good, regardless of HIV status.