Respiratory syncytial virus (RSV) is the major cause of acute lower respiratory tract infection in children and vulnerable adults, but little is known regarding RSV infection in Africa. In this report, a recent RSV outbreak in Mozambique was studied and results showed that 275 of 3192 (8n6%) nasopharyngeal aspirates tested were RSV-positive by ELISA. RSV presents two antigenic groups (A and B) with a high genetic and antigenic variability between and within them. Analysis by a new RFLP assay of RT-PCR amplified N protein gene products showed a higher prevalence of group B RSV than that of group A (85 % versus 15 %). However, genetic variability of the G protein gene was higher among group A RSV strains. The frequency and pattern of glycosylation sites were also quite different between both groups. In addition, two different phylogenetic clusters of Mozambican viruses were found within each group, but only sequences from cluster B-I were relatively distinct from previously described isolates. The implications of such differences in the antigenic and immunogenic characteristics of each group are discussed.

A case control study was carried out in Manhiça (Mozambique). Serum samples were collected from infants < 1 year of age in hospital to assess the effect of serum antibodies on the incidence of respiratory syncytial virus (RSV) infection. Sera were collected from a total of 31 cases of RSV infection and paired uninfected controls matched for age and sex. Anti-RSV antibodies were assessed by a membrane fluorescent antibody test (MFAT) for immunoglobulin G (IgG) antibodies and by a neutralizing antibody test. IgG RSV antibodies were of higher prevalence and at higher levels in the control group when compared to the infected case group (P < 0.001), indicating an important role for IgG antibodies in protection. To assess infection before recruitment, IgA RSV antibodies were also measured by MFAT. IgA RSV antibody prevalence was very low in patients and controls (0/31 and 4/31 respectively), suggesting that most of the detected IgG RSV antibody in both groups was of maternal origin. Re-analysis of data from the subset of 27 matched, IgA RSV antibody negative infant pairs mirrored the full analysis indicating that maternal antibody has an important role in RSV protection. Similar results were obtained when neutralizing antibodies were measured and when the measurement was done against subgroup A virus strain A2, subgroup B virus strain 8/60 and a contemporary subgroup A isolate, Moz00. No significant differences in the reactivity of maternal antibodies with the three virus strains were observed. The data described below represent the first analysis of the role of maternal antibodies in reducing the risk of pediatric infection in developing countries. The results reinforce the concept of maternal vaccination for the control of RSV in very young children in whom the risk and severity of infection are the highest.