Expression of a recombinant gag protein from endogenous avian virus and its use in screening for antibody reactivity in recipients of chick-derived vaccines

Virions incorporating endogenous avian virus (EAV) RNA have been identified in chick-derived biological products, including the vaccines used to protect against measles, mumps, and yellow fever. The presence of EAV in these vaccines raises safety concerns regarding transmission to vaccine recipients. Development of a serologic assay to detect antibodies to EAV required the discovery of a diagnostic EAV antigen and reactive antiserum. For this purpose, we have identified and expressed an EAV capsid sequence that was found to have a 66.9% amino acid identity to avian myeloblastosis virus (AMV) p27 capsid. An AMV capsid antiserum that cross-reacted to the EAV protein in both Western blot (WB) and ELISA-based testing was selected as a positive control reagent. Using our assay, we evaluated sera from 200 measles–mumps–rubella (MMRII) and 43 yellow fever (YFFIOCRUZ) vaccine recipients and found none of the samples were reactive to EAV capsid. The results support a lack of EAV infection in the vaccine recipients. [Copyright &y& Elsevier]