Tissue tropism and target cells of bluetongue virus in the chicken embryo.

In situ cytohybridization was used to determine the tissue tropism and target cells for replication of bluetongue virus (BTV) in the developing chicken embryo. Hybridization with a biotinylated probe specific for segment 3 of BTV serotype 17 detected viral replication in embryos inoculated with U.S. serotypes 2, 10, 11, 13, and 17 or sheep blood containing a BTV field strain. At the final stages of infection, when the embryos were hemorrhagic, viral infection could consistently be detected in the brain, kidney, spinal cord, heart, lung, and liver, with the brain and kidney most severely affected. Other tissues, such as the retina, skin, tongue, and intestinal villi, also supported viral replication in some embryos. Greater concentrations of virus tended to be localized within epithelial cells, such as those lining the kidney tubules and tertiary bronchi of the lungs. Kinetics studies with BTV serotypes 11 and 17 and a field strain indicated that within 24 h after inoculation, viral replication occurred initially in the brain and kidney. By 48 h, viral replication was also detected in the lungs, heart, and spinal cord, with the liver being severely infected by 72 h. Low levels of hybridization could be detected in embryos infected with epizootic hemorrhagic disease virus, which is antigenically related to BTV.