Malignant Lymphoma with Severe Infiltrative Growth into Skeletal Muscles in WBN/Kob Rats

Detection of high antibodies titers against rat leukemia virus in an outbreak of reproductive disorders and lymphomas in Wistar rats

Young female Wistar rats from a specific pathogen free breeding colony presented an outbreak of infertility along with neurological symptoms and malignant lymphomas. We evaluated the presence and the potential role of the rat leukemia virus (RaLV) in the disease because these clinical signs could be compatible with a retrovirus. RaLV is a mammalian type C endogenous retrovirus initially isolated from in vitro Sprague-Dawley rat embryo cultures. There are no reports of clinical disease in rats associated with this virus, and little is known about its interaction with the host. Using reverse transcription polymerase chain reaction and enzyme-linked immunosorbent assay, we studied the synthesis of the viral particles and the development of an immune response against the virus in this rat colony. The results showed that healthy and diseased Wistar rats synthetized viral RNA but only diseased animals developed a detectable immune response against RaLV envelop protein. Furthermore, rats with lymphomas tended to have higher titers of antibodies against RaLV epitopes than those with infertility or neurological symptoms. The results suggest that increases in the RaLV infectious particle loads could be involved in the development of lymphomas in young rats. The potential causes of RaLV reactivation are discussed.