Bluetongue Virus Genome Remains Stable throughout Prolonged Infection of Cattle

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Abstract
Summary Infection of three calves with a highly plaque-purified strain of bluetongue virus (BTV) resulted in prolonged infections, during which virus and neutralizing antibodies co-circulated in peripheral blood. Oligonucleotide fingerprint analyses of the original challenge virus and of the final virus isolate obtained from each calf demonstrated the BTV genome to remain stable throughout prolonged infection as no differences in fingerprint patterns were detected. Six neutralizing monoclonal antibodies (MAbs), and a polyclonal rabbit antiserum, were produced against the challenge virus. This panel of MAbs recognized at least two distinct neutralizing epitopes as demonstrated by immune precipitation. Neutralizing epitopes remained stable through the prolonged infections, as all MAbs and the polyclonal rabbit antiserum neutralized the challenge virus and the final calf isolates to equivalent titres. These results suggest that antigenic drift is not the mechanism by which BTV is able to persist in cattle in spite of a strong humoral immune response.