Associations of feline paramyxoviruses with pathological lesions in cat kidneys

Paramyxoviruses in cats composing of feline paramyxovirus (FPaV), feline morbillivirus genotype 1 (FeMV-1), and feline morbillivirus genotype 2 (FeMV-2). These viruses had been recently suggested to be associated with kidney disease in cats. However, pathological consequence of infection is remained restricted. This study aimed to investigate the association of paramyxovirus infection and pathological consequence in cats’ kidney. Renal fresh tissues were collected from routine necropsy in Department of Pathology, Faculty of Veterinary Science, Chulalongkorn University. Then, tissues were histopathologically categorized into normal group and pathologic group. To screen paramyxovirus infection, reverse-transcription polymerase chain reaction (RT-PCR) assays using Res-Mor-Hen pan-primer set and specific primer set for each virus were carried out. Then, RT-PCR positive cases were employed for special staining determination using Periodic acid-Schiff (PAS) and Masson Trichrome (MT), followed by immunohistochemistry (IHC) and in situ hybridization (ISH). Furthermore, apoptotic activity assay was employed to detect the expression of cleaved caspase 3. Semiquantitative scorings were carried out for positive cases according to histopathological parameters such as degree of interstitial inflammation, tubular detachment, fibrosis, and apoptotic activity. The statistic data was evaluated using Spearman correlation coefficient with two-tailed test and p<0.05. The result of molecular detection revealed that nine samples were positive only for FeMV-1 infection. All FeMV-1 positive cases belonged to renal pathologic group. In each case, lymphoplasmacytic interstitial inflammation was observed. Immunostaining signal was observed on seven cases. However, ISH signal was exhibited by all cases. Interestingly, both IHC and ISH signals were expressed in both nucleus and cytoplasm of tubular epithelial cells. Association between FeMV-1 infection and histopathological parameters suggested that FeMV-1 infection would likely increase the apoptotic activity in infected kidneys. The presence of lymphoplasmacytic inflammation might be evidence that FeMV using signaling lymphocyte activation molecules (SLAM; CD150) that expressed on lymphoplasmacytic inflammatory cell as a viral receptor. Furthermore, viral localization would likely suggest that FeMV-1 did not only undergo replication and virion assembly in cytoplasm, but also in nucleus of tubular epithelial cells. Moreover, the apoptotic activity assay would likely to suggest that FeMV ruling caspase-dependent apoptotic activity.