No abstract

Natural and experimental feline coronavirus (FCoV) infection leads to systemic viral spread via monocyte-associated viraemia and induces systemic proliferation of monocytes/macrophages. In the majority of naturally infected animals, FCoV infection remains subclinical and is associated with generalised B and T cell hyperplasia, but no other pathological findings. A minority of cats, however, develop feline infectious peritonitis (FIP), a fatal systemic granulomatous disease. This is generally accompanied by B and T cell depletion. The obvious functional differences of lymphatic tissues in FCoV-infected cats with and without FIP suggest that they contribute to the outcome of FCoV infection. This study attempted to evaluate the functional changes in haemolymphatic tissues after natural FCoV infection, with special emphasis on the magnitude, phenotype and function of the monocyte/macrophage population. The spleen, mesenteric lymph nodes and bone marrow from naturally FCoV-infected cats with and without FIP and specific pathogen-free (SPF) control cats were examined for the quantity and activation state of monocytes/macrophages both by immunohistology and by quantitative real time PCR for the transcription of interleukin (IL)-1beta, IL-6, IL-10, IL-12 p40, tumour necrosis factor (TNF), granulocyte colony stimulating factor (G-CSF), macrophage-CSF (M-CSF) and GM-CSF. Compared to cats with FIP, FCoV-infected cats without FIP exhibited significantly higher IL-10 levels in the spleen and significantly lower levels of IL-6, G- and M-CSF in mesenteric lymph nodes. In cats with FIP, however, IL-12 p40 levels were significantly lower in lymphatic tissues in comparison to both SPF cats and FCoV-infected cats without FIP. In comparison to SPF cats, FIP cats had significantly higher IL-1beta levels and lower TNF levels in mesenteric lymph nodes and lower M-CSF levels in the spleen. Findings indicate that FCoV-infected cats which do not develop FIP are able to mount an effective FCoV-specific immune response and can avoid excessive macrophage activation and FIP, possibly by upregulation of IL-10 production. Development of FIP, however, might be due to a lack of IL-12 which inhibits an effective cellular immune response and allows for monocyte/macrophage activation and the development of FIP.

No abstract

A novel diagnostic test for feline leukemia virus (FeLV) RNA in saliva from naturally infected cats is described in this study. We evaluated different diagnostic tests and compared them with the widely used enzyme-linked immunosorbent assay (ELISA) for the detection of p27 in the diagnosis of FeLV. Blood samples from 445 cats were tested for the presence of provirus by real-time PCR and plasma and saliva specimens from those cats were tested for the presence of viral RNA by real-time reverse transcription (RT)-PCR and for the presence of p27 by ELISA. In comparison to conventional ELISA, the diagnostic sensitivity and specificity of the detection of salivary FeLV RNA by real-time RT-PCR were found to be 98.1 and 99.2%, respectively. Detection of viral RNA in saliva had a positive predictive value of 94.6% and a negative predictive value of 99.7%. The kappa value was 0.96, demonstrating an almost perfect agreement between both tests. Furthermore, we confirmed previous results showing that a number of cats which tested negative for the presence of p27 in plasma were in fact positive for the presence of DNA provirus in blood specimens (5.4%). However, 96.4% of these latently infected cats did not shed viral RNA in saliva; therefore, we assume that these cats are of relatively low clinical importance at the time of testing. This study shows considerable diagnostic value of the detection of saliva FeLV RNA in naturally infected cats. This new diagnostic method has advantages over the conventional ELISA, such as less invasive sample collection and no requirement for trained personnel.

No abstract