Type-specific immune response to human T cell lymphotropic virus (HTLV) type I and type II infections in Nigeria.

Abstract Type-specific antibody responses to human T cell lymphotropic virus type I (HTLV-I) and type II (HTLV-II) were studied in blood samples collected from 25 different locations in Nigeria between 1985 and 1991 and stored at the University College Hospital in Ibadan. A total of 4,153 sera were collected from participants in the National Immunity Survey of Viral Infections (n = 1,640), patients with tuberculosis (TB) (n = 140), patients with sexually transmitted diseases (STDs) (n = 876), patients with other medical conditions (n = 1,285), female prostitutes (n = 60), and health care workers (n = 152). The overall seroprevalence of HTLV was 5.6%, with similar rates among males and females. Using enzyme immunoassays that differentiated between antibodies to the two viruses, the seroprevalence rates were 2.5% for HTLV-I and 1.9% for HTLV-II, with an additional 1.2% of the samples dually reactive for both HTLV-I and HTLV-II. The seroprevalence rates for HTLV were low among children (0.8%) and adolescents (1.7%), with substantially higher rates among adults (range 5.0–7.4%). Age-specific patterns among adults appears to differ for HTLV-I and HTLV-II, with HTLV-I rates peaking above age 50 and HTLV-II rates peaking below age 50. The highest overall HTLV prevalence rates were observed for STD patients (16.3%), followed by female prostitutes (8.3%), TB patients (6.4%), health care workers (3.3%), patients with other medical conditions (3.2%), and immunity survey participants (1.8%). The similarity of prevalence rates of males and females, as well as the high rates among STD patients and prostitutes, suggest a primary role for heterosexual transmission of these viruses. Prevalence rates of these two viruses do not appear to have increased during the seven-year study period in Nigeria.