Prevalence of antibodies against herpes simplex virus types 1 and 2 in children and young people in an urban region in Tanzania

Abstract

Herpes simplex virus type 1 (HSV-1) is transmitted by close contact, both sexual and nonsexual, and infections are acquired during childhood and adolescence. Herpes simplex virus type 2 (HSV-2), however, is thought to be transmitted mainly by sexual contact. Most HSV-2 infections are consequently expected to occur after the onset of sexual activity. Recent reports indicate an increasing prevalence of HSV-2 on the African continent, but most studies have been performed on adult cohorts. In the present study, we collected sera from Tanzanian children and young persons from 1 to 20 years old, with at least 100 individuals in each age group. Antibodies against HSV-1 and HSV-2 were detected by an in-house Western blot method which was shown to perform well in comparison with a commercial Western blot assay. Type-specific antibodies were also analyzed by two noncommercial enzyme-linked immunosorbent assay methods based upon the antigenicities of branched synthetic oligopeptides corresponding to epitopes in glycoprotein G of HSV-1 or HSV-2. The prevalence of HSV-1 antibodies increased gradually from 73% for the age group of 1 to 4 years to 92% for the age group of 17 to 20 years. The prevalence of HSV-2 antibodies was unexpectedly high, as 15% of the children were infected by the age of 8 years, with the incidence increasing gradually to 40% in the age group of 17 to 20 years. The reason for this unexpectedly high frequency is not clear but could suggest that nonsexual transmission of HSV-2 is more common than previously thought. There was no statistically significant association between seropositivities for HSV-2 and human immunodeficiency virus.

FIG. 1.

Performance of WB-UB method. Proteins from cells infected with HSV-1 or HSV-2, as indicated, were separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and blotted onto nitrocellulose membranes which were subsequently cut into strips. Strip 1 in the left panel was incubated with an HSV-1-negative serum, while strip 1 in the right panel was incubated with an HSV-2-negative serum. Strips 2 were incubated with monoclonal antibodies LP10 (left panel) and AP1 (right panel), directed against gG-1 and gG-2, respectively, while strips 3 were incubated with human sera. The positions of gG-1 and gG-2 are indicated by arrows.

FIG. 2.

Analysis of sera for antibodies against HSV-1 and/or HSV-2. An analysis of sera by WB-UB for antibodies against HSV-1 and/or HSV-2, as related to age groups, is shown in panel B. Statistical methods were used to investigate whether the differences in prevalence between the age groups were significant. For HSV-1 antibodies, the results were as follows: χ² = 15.68, df = 4, and P = 0.003. For HSV-2 antibodies, the results were as follows: χ² = 27.72, df = 4, and P < 0.001. The horizontal bars for the 1- to 4-year-old age group indicate the prevalence of HSV-1 and HSV-2 antibodies, respectively, in the subgroup of 2- to 4-year-olds. In panel A, the 1- to 4-year-old age group is split into two subgroups, <2 years and 2 to 4 years. Statistical methods were used to analyze the differences between the age groups. For HSV-1 antibodies, the results were as follows: P = 0.80 and OR (95% CI) = 1.14 (0.43 to 3.01). For HSV-2 antibodies, the results were as follows: P < 0.001 and OR (95% CI) = 0.12 (0.04 to 0.36). Panel C shows the percentages of uninfected and single- and double-infected individuals in each age group.