HOMOTYPIC AND HETEROTYPIC NEUTRALIZATION DETERMINANTS OF BLUETONGUE VIRUS SEROTYPE-17

Homotypic and heterotypic neutralization determinants of bluetongue vi rus serotype 17 (BTV-17) were investigated with a panel of five neutra lizing monoclonal antibodies (MAbs). One MAb (MAb 034) was originally raised to BTV serotype 10 (BTV-10) but also neutralizes BTV-17 (P. V. Rossitto, and N. J. MacLachlan, 1992, J. Gen. Virol. 73, 1947-1952). C ompetitive binding studies indicate that the MAbs recognize at least t wo epitopes on the neutralizing outer capsid protein VP2 of BTV-17. Th e MAbs were used to select neutralization-resistant variant [escape mu tant (EM)] viruses and to determine the phenotypic characteristics of these EM viruses by immunoprecipitation and neutralization assays. Seq uencing of the L2 gene, which encodes VP2, identified mutations respon sible for the altered phenotypic properties exhibited by each EM virus . Four amino acids in three regions of VP2 are critical to the express ion of the epitopes recognized by the panel of neutralizing MAbs. Amin o acid 199 affects the binding of MAbs 17.82, 17.83, and 17.813; amino acid 213 affects the binding of MAb 17.85; and amino acids 327 and 58 2 synergistically affect the binding of MAb 034. Similarly, amino acid s 327 and 402 synergistically affect the binding of MAb 034 to BTV-10 (C. D. DeMaula, H. W. Heidner, P. V. Rossitto, C. M. Pierce, and N. J. MacLachlan, 1993, Virology 195, 292-296), suggesting that the neutral izing epitope common to BTV-10 and BTV-17 has a similar location in VP 2 of these two antigenically distinct viruses. (C) 1995 Academic Press , Inc.