Evaluation of Japanese quail as a model system for avian transgenesis using avian leukosis viruses.

Vertical transmission of avian leukosis viruses (ALV) can occur genetically through the germline for both male and female chickens but only nongenetically or congenitally through the female. We had previously shown that tolerantly ALV-infected males, from ALV injection into fertile chicken eggs at day of set, can transmit proviral DNA to their progeny through the germline. An attempt was made to repeat this successful retroviral germline insertion technique of chickens in Japanese quail. After an initial difficulty of infecting quail chicks in ovo at day of set with high titer nonpathogenic recombinant and pathogenic ALV, adequate numbers of tolerantly ALV-infected quail were produced by injecting ALV-infected chicken embryo fibroblasts (CEF) at day of set. Tolerantly ALV-infected male and female quail were then mated to nonviremic quail and vertical transmission of ALV to progeny chicks was determined by analyzing blood for viral antigens and proviral DNA using standard techniques. Vertical transmission of ALV was only detected in the progeny of viremic females. Thus, little or no germline transmission of ALV to progeny occurred from viremic males. Tolerantly ALV-infected males and females from congenital ALV infection, which should infect the embryo and presumably the primordial germ cells (PGC) earlier than egg injection, were mated to nonviremic quails. Vertical transmission of ALV to progeny chicks was analyzed as before. Again, vertical transmission of ALV was only detected in the progeny of viremic females. We conclude that Japanese quail will not be useful in avian transgenic studies involving ALV retroviral vectors.