Abstract
Feline infectious peritonitis (FIP) results from mutations in the viral genome during a common feline enteric coronavirus (FECV) infection. Since many virological and immunological data on FECV infections are lacking, the present study investigated these missing links during experimental infection of three SPF cats with FECV strain UCD. Two cats showed mild clinical signs, faecal shedding of infectious virus from 4 dpi, a cell-associated viraemia at inconsistent time points from 5 dpi, a highly neutralising antibody response from 9 dpi, and no major abnormalities in leukocyte numbers. Faecal shedding lasted for 28–56 days, but virus shed during this stage was less infectious in enterocyte cultures and affected by mutations. Remarkably, in the other cat neither clinical signs nor acute shedding were seen, but virus was detected in blood cells from 3 dpi, and shedding of non-enterotropic, mutated viruses suddenly occurred from 14 dpi onwards. Neutralising antibodies arose from 21 dpi. Leukocyte numbers were not different compared to the other cats, except for the CD8+ regulatory T cells. These data indicate that FECV can infect immune cells even in the absence of intestinal replication and raise the hypothesis that the gradual adaptation to these cells can allow non-enterotropic mutants to arise.
Highlights
Correlation with RT-qPCR results) of faeces, and on the generation of neutralising antibodies during Feline enteric coronavirus (FECV) infections
Whereas immune responses during feline infectious peritonitis (FIP) development have been extensively studied[13,16,17,22], hardly any information is available on the dynamics of several leukocyte subsets during FECV infections
Mutations play a key role in the Feline coronaviruses (FCoVs) pathogenesis, too little is known about the viral genome evolution during FECV infections and the impact of these mutations on the infectivity of the faecally shed viruses
Summary
Correlation with RT-qPCR results) of faeces, and on the generation of neutralising antibodies during FECV infections. Feline enterocyte cultures sustaining the replication of FECVs have previously been developed[21], allowing the quantification of enterotropic viruses and neutralising antibodies in in vivo experiments. Whereas immune responses during FIP development have been extensively studied[13,16,17,22], hardly any information is available on the dynamics of several leukocyte subsets during FECV infections. This study aimed at further broadening our knowledge on the FECV pathogenesis, by monitoring various clinical, virological (genome evolution, virus infectivity in enterocyte cultures, and onset and duration of viraemia), and immunological (presence of neutralising antibodies and the dynamics of several leukocyte subsets) parameters in the 3 months following inoculation of three specific pathogen free (SPF) cats with FECV strain UCD
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