Detection of cmv-related gastrointestinal tract infections in a series of 49 xenotransplanted primates

Background: Generalized CMV infections have been observed in immunosuppressed cynomolgus monkeys. Therefore, in this study we have investigated, using different approaches, the presence of CMV infection in a series of 49 primate recipients of porcine renal xenografts. Methods: Fifty-two Macaca fascicularis were used: 49 were recipients of kidney xenografts and 3 were part of a pharmacokinetic trial. All primates were housed in the same facility and treated with immunosuppressive drugs. As a high level of homology between Rhesus and Macaca fascicularis CMV has previously been reported, primates were tested serologically by ELISA for rhCMV upon arrival at the facility and, in some cases, also at the time of transplantation. Three-hundred and twenty formalin-fixed paraffin-embedded sections of gastrointestinal (GI) tract were analysed by light microscopy. All sections were also studied by immunohistochemistry (IHC) for expression of RhCMV IE1 antigen. A consensus-PCR with specificity for the herpesviral DNA-directed DNA polymerase gene (DPOL) was performed on a cryopreserved lung tissue of an IHC strongly positive primate. Results: Upon arrival at the facility, 22 primates were serologically positive for CMV, 20 were negative and 10 were equivocal. The serological test repeated on the negative and doubtful animals at the time of transplantation showed that all primates had serum-converted. GI-tract sections of 5 of the 52 primates analysed showed lesions associated with CMV infection. However, 8 primates were IHC positive for CMV although 3 did not show any histological evidences of CMV infection. Antigen IE1 was detected in epithelial cells in 6 out of 8 primates. The molecular analysis by PCR revealed a 99% identity of the DPOL gene between Rhesus and Macaca fascicularis CMV (100% identity at amino acid level). Conclusions: IHC is more sensitive and specific in the detection of CMV infection in immunosuppressed, xenotransplanted primates than classical histology. Our data suggest that all the animals serum-converted for CMV whilst waiting for xenotransplantation. In the light of the frequent observation of CMV-related lesions in xenotransplanted animals, an effective anti-CMV prophylaxis appears to be indispensable in such model.