Genetic variability among group A and B respiratory syncytial viruses in Mozambique: identification of a new cluster of group B isolates.

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 (8.6%) 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.