Lack of antigenic relationship between French and recent North American non-A/non-B turkey rhinotracheitis viruses

Twelve turkey rhinotracheitis viruses (TRTVs) including the Colorado isolat e and two French non-A/non-B viruses were serologically compared. Six enzym e-linked immunosorbent assay (ELISA) antigens derived from subgroup A, subg roup B, a French non-A/non-B, and the Colorado TRTVs were used. Virus neutr alization (VN) tests were performed with four Ma-104-adapted viruses derive d from subgroup A, subgroup B, a French non-A/non-B, and the Colorado virus es. French strains isolated since 1995 were assigned to subgroup B in both ELISA and VN, whereas those isolated in 1985 and 1986 appeared more diverse : two strains belonged to subgroup B, one to subgroup A, and two others app eared antigenically different from both the A and B subgroups and are class ified as non-A/non-B. The Colorado strain appeared different from these thr ee groups of TRTVs. Assignment to subgroup A or B was confirmed by reverse transcription-polymerase chain reaction, but neither the French non-A/non-B strains nor the Colorado virus could be classified with the subgroup-speci fic G-based primers. These results suggest chat at least three antigenicall y different viruses were present in France in 1985-86 and that the Colorado strain is different from all European TRTVs. Further serologic and phyloge nic studies will be necessary to evaluate their actual prevalences and rela tionships.