Comparison of human respiratory syncytial virus A2 and 8/60 fusion glycoprotein gene sequences and mapping of sub-group specific antibody epitopes

The fusion glycoprotein, F, of human respiratory syncytial virus is a princ ipal target of neutralising antibodies and an important protective immunoge n. Among sub-group A strains of the virus the F gene is highly conserved. A comparison of F gene sequences of two sub-group B strains, 8/60 and 18537, indicates that the gene also is conserved within this sub-group. However, both limited sequence variability and antigenic variation occurs between F genes from different virus sub-groups. Such variability may be important in the failure of natural- and vaccine-induced immunity and it is thus import ant to identify the variable epitopes. Three anti-F MAbs exhibiting sub-gro up specific neutralisation and binding to recombinant F glycoprotein were s tudied. Comparison of A2 and 8/60 F gene sequences revealed 64 predicted va rient amino acids. In order to map the variant amino acids responsible for subgroup specific binding, three sets of chimaeric genes, in which differen t domains of A2 and 8/60 F were exchanged, were created and expressed. Sub- group specificity mapped to the N-terminal region of F1 for two MAbs (RS2B8 and RS348) and to the C-terminal region for the third. By using site-direc ted mutagenesis, sub-group specific binding of MAbs RS2B8 and RS348 was att ributed to a predicted loop region between residues 200 and 216. This loop carried four residues variant between the sub-groups. Change of at least tw o was necessary to abrogate MAb binding. (C) 2001 Wiley-Liss, Inc.