Structural Differences between Subtype A and B Strains of Respiratory Syncytial Virus

Abstract

SUMMARYDifferences in the properties of homologous intracellular structural components of eight strains of subtype A and eight strains of subtype B of human respiratory syncytial (RS) virus were examined. The size of the fusion (F) protein cleavage products and the phosphoprotein (P) showed systematic differences between virus strains representing the two subtypes. The apparent mol. wt. in SDS-polyacrylamide gels under reducing conditions was 48000 (48K) and 46K to 47K for the cleavage product FI in subtype A and B strains, respectively. The size of the F2 protein was 18K to 20K. The subtype B strains showed a slightly higher tool. wt. of this protein compared to the subtype A strains. The size of the P protein was 36K in subtype A strains, but only 34K in subtype B strains. Variations also occurred in the size of the glycoprotein (G) and the 22K to 24K structural protein. These variations did not correlate with the virus subtypes, but were strain-specific. The size of non-glycosylated forms of the F protein cleavage products was determined by use of material from tunicamycin-treated cells. A 44K to 45K non-glycosylated form of the F 1 protein was detected with subtype A virus strains, but the corresponding protein of subtype B strains was not reproducibly identified, presumably due to instability in the absence of glycosylation or altered antigenicity. Monoclonal antibody immunosorbent-bound viral glycoproteins were partially digested with proteases. The pattern of breakdown products of the F1 protein was distinctly different between subtype A and B strains, but it was similar among strains of the same subtype. No subtype-specific pattern was seen in proteolytic digests of monoclonal antibody-bound G protein. INTRODUCTIONFor the 3 decades since its discovery human respiratory syncytial (RS) virus has been considered to represent a single homogeneous serotype. Although cross-neutralization tests with animal hyperimmune sera demonstrated differences between isolates of the virus (Coates et al., 1963; Wulffet al., 1964;Doggett & Taylor-Robinson, 1964) no corresponding differences were observed with infant sera and they were therefore not considered to be of any relevance. With the advent of monoclonal antibodies (MAbs) the antigenic stability of RS virus could be assessed again. Studies with such reagents revealed that isolates of RS virus exhibited variations in epitope occurrence (Gimenez et al., 1984) but that these variations were more extensive than could be explained by incidental mutational changes (Anderson et al., 1985;Mufson et al., 1985). The isolates could be separated into two categories based on their characteristic reaction pattern with different MAbs. The two groups were named RS virus subtype A and B (Mufson et al., 1985). These subtypes showed different properties in at least four different structural proteins emphasizing that they had become ecologically adjusted after a period of separate evolution. Characterization of the epidemiological occurrence of the two RS virus subtypes

Genetic and antigenic analysis of the G attachment protein of bovine respiratory syncytial virus strains.

“…Reaction patterns with specific monoclonal antibodies (MAbs) revealed that the main differences between these two subgroups were located in the G protein (Mufson et al, 1985). Additional differences were also detected in the F, N, M and M2 proteins (Norrby et al, 1986). Variability in the amino acid sequences of the G protein has been demonstrated between isolates of both subgroup A (Cane et al, 1991) and subgroup B (Sullender et al, 1991) of HRSV.…”

Comparison of Antigenic Sites of Subtype-specific Respiratory Syncytial Virus Attachment Proteins

“…Both antigenic and structural differences between subtypes have been described for several RSV proteins, including G and F (Ward et al, 1984;Norrby et al, 1986;Walsh et al, 1987b;Morgan et al, 1987). The most significant antigenic difference between A and B subtypes, however, resides on the G protein where amino acid homology is only 53 % and antigenic relatedness is 5% Johnson et al, 1987a).…”

Preparation and Characterization of Monoclonal Antibodies Directed against Five Structural Components of Human Respiratory Syncytial Virus Subgroup B

“…Within each subgroup no antigenic variation was detected. In a subsequent study, differences in the properties of homologous structural components of eight strains of subgroup A and eight strains of subgroup B were investigated (Norrby et al, 1986). Subgroups A and B differed in the sizes of the cleavage product F~ protein and the P protein.…”