Replication of herpesvirus of turkeys in chick fibroblasts

An ultrastructural study of chick embryo fibroblasts infected with herpesvirus of turkeys (HVT) revealed that infection produced degenerative effects in the cells ranging from alteration of cellular structures to complete lysis of the cells. Infection was indicated by margination of the nuclear chromatin, the presence of nuclear and cytoplasmic virions, destruction of mitochondria, loss of rough and smooth endoplasmic reticulum, and polykaryocytosis. Viruses entered the cell by penetrating the cytoplasmic membrane, and replication took place within the nucleus. Small nuclear particles observed as aggregates in the presence of few herpesvirions appeared to be a part of the replication of the virus. Viruses were released from the cell nucleus either naked or enveloped. Where karyolysis occurred, naked viruses were released as the karyoplasm diffused into the cytoplasm. Enveloped viruses were not observed leaving the nucleus, but it appeared that departure could have occurred by the budding of the viruses through the nuclear membrane. Where complete lysis of the cells occurred, the naked viruses were released into the extracellular fluid. Enveloped viruses were observed only in intact cells. Viruses which were observed extracellularly were naked viruses, and those that were observed entering the cell by penetrating the cytoplasmic membrane were also naked. This evidence suggests that in vitro HVT does not require the envelope to be infective.