Media Kedokteran Hewan Vol. 22, No. 2, Mei 2006 68 Neutralization of Avian Reovirus 1091 in Chick Kidney and Vero cell Cultures by Monoclonal Antibodies against B/BC and C Proteins Netralisasi Avian Reovirus 1091 pada Kutur Sel Ginjal Anak Ayam dan Vero oleh Antibodi Monoklonal terhadap Protein B/BC DAN C Nyoman Mantik Astawa Depatement of Virology, Faculty of Veterinary Medicine, Udayana University, Jl. P.B. Sudirman, Denpasar, Bali, Indonesia Email: nyomanmantikastawa@yahoo.com Abstract A study on the neutralization of avian reovirus 1091 by mon oclonal antibodies (MAbs) against B/BC and C proteins was carried out in primary chick kidney (CK) and seconadary Vero (African green monkey kidney) cell cultures. MAbs against individual proteins of avian reovirus 1091 were produced by fusion of spleenocytes derived from mice immune to avian reovirus 1091, with immortal mouse myeloma cells. The neutralization of the virus infectivity by MAbs in primary chick kidney (CK) and Vero (African green monkey kidney) cell cultures was determined by plaque reduct ion neutralization test (PRNT). Four MAbs against B/BC protein and 5 MAbs C protein of avian reovirus 1091 were produced in this study. Four MAbs against against B/BC were designated as 4D1, 4E2, 5F5 and 5A6. Five MAbs against C portein were designated as 1A2, 4D3, 5A12, 5B11 and 5C6. PRNT showed that one MAb (5A6) against B/BC neutralized the virus infectivity in CK and Vero cell cultures. Three Mabs against C (5A12, 5B11 and 5C6) neutralized the virus in primary CK cell culture but only two MA bs (5A12 and 5C6) against C protein neutralized the virus infectivity in Vero cell culture. Two MAbs (1A2 and 4D3) against C and 3 MAbs (4D1, 4E2, 5F5) against B/BC showed no neutralizing activities both in CK and Vero cell cultures. The neutralization of avian reovirus 1901 by MAbs against B/BC and C proteins indicated that the protein play important roles in infection processes and my be potential candidates for the preparation of a good vaccine. Keywords: neutralization, avian reovirus 1091, mon oclonal antibodies, B/BC protein, C protein Introduction Avian reoviruses have been widely associated with runting/stunting syndrome or malabsorption syndrome (MAS). The association MAS with avian reovirus infection has been proven both field surveys and in controlled experiments (Pass et al, 1982 , Goodwin et al, 1993; Songserm et al, 2000; Songserm et at, 2002). Commonly, the susceptible age of MAS is the first two weeks of age and is mainly characterized by gastrointestinal lesions directly resulting in weight gain depression. The gastrointestinal lesions generally include proventriculitis and enteritis with cellular infiltration, cystic crypts of Lieberkuhn, villus atrophy and villus fusion (Reece et al, 1990). MAS is an economic problem in poultry industry worldwide. One of avian reovirus strain frequently isolated from chickens with MAS is avian reovirus 1091 (Pass et al, 1982). Avian reovirus particles consist of ten segments of dsRNA genomes each of which codes fo r a single individual protein. The genomes are designated as L1, L2, L3, M1, M2, M3, S1, S2, S3, and S4 (Robertson and Wilcox 1986). At least 10 individual proteins encoded by the genes have been identified and they are designated as A,B,C, A/AC, NS, A, B, NS, C (Schnitzer et al, 1982). Each protein plays impor - tant role in the infection processes and therefore studies on the function of each individual protein is important in understanding the pathogenesis of avian reovirus infection as well as in finding the effort of controlling the disease. Two surface proteins sugges- ted to play important role in the infection processes are B/BC and C proteins. Miu B/BC was initially designated as A/AC (Shnitzer et al, 1982) but further studies showe d that the correct designation of this protein is B/BC