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ABSTRACT. Monoclonal antibodies (mAbs) were prepared against the 8597/CV94 strain of turkey rhinotracheitis virus (TRTV). These mAbs were used to investigate antigenic relationships among three strains (8597/CV94, 1162/92 and CVL14/1 strain) of TRTV, together with polyclonal chicken and rabbit antisera to 8597/CV94 strain, and guinea pig antisera to each of the three strains. Thirty mAbs to the glycoprotein (G:3 clones), fusion (F1:6 clones), phosphorylated (P:6 clones), nucleocapsid (N:12 clones), and matrix (M:3 clones) proteins of viral antigen were obtained by cell fusion. Among these, two mAbs to F1 protein showed virus neutralizing activity. The results of ELISA test indicated that some mAbs only reacted to the 8597/CV94 strain, some reacted to 8597/CV94 and 1162/92 strains, and others reacted to all three viral strains. In neutralization tests with the three virus strains, polyclonal chicken and rabbit antisera against the 8597/ CV94 strain showed the same antibody titers. Results with four neutralizing mAbs including two previously reported mAbs [Ref. 21] indicated the titers of two mAbs (Pn2-2E and Pn3-2F) to 8597/CV94 were much higher than those to the other two viral strains. No differences were observed in the titers of the other two mAbs (Pn01-8E and Pn06-4D) against any viral strains. In cross-neutralization tests with polyclonal guinea pig antisera, there was some variations among viral strains. This work demonstrated that the Japanese isolate 8597/CV94 of TRTV is somewhat different in antigenicity from two British isolates from chickens and turkeys. strains isolated in the UK from chickens and turkeys by enzyme-linked immunosorbent assay (ELISA) and virus neutralization tests with the newly produced mAbs and polyclonal antisera. MATERIALS AND METHODS Viruses:The virus used in this study was 8597/CV94 strain isolated from chickens with SHS. British strains, 1162/92 isolated from chickens [10] and CVL14/1 isolated from turkeys [24], were supplied by Dr. R. E. Gough (Central Veterinary Laboratory, UK). The viruses were propagated in Vero cells, and purified from infected culture fluid by differential ultracentrifugation and by sedimentation through a 20-60% discontinuous sucrose gradient at 100,000 ×g for 90 min. The virus band was collected and used as purified virus for immunization and the ELISA antigens.Antisera: Guinea pigs were immunized with the three strains of TRTV. Specific pathogen free chickens and rabbits were immunized with the 8597/CV94 strain. The virus suspensions containing 1.0 × 10 6.0 TCID 50 /ml emulsified with an equal amount of Freund's complete or incomplete adjuvant were employed as immunogens. Rabbits and guinea pigs were injected intramuscularly and then subcutaneously at two-week intervals with 1 or 0.5 ml of the virus. Chickens were given 0.1 ml of the virus suspension without adjuvant intraocularly twice at two-week intervals. The animals were bled two weeks after the last injection, and the sera were stored at 20°C until use.

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