Determination of the cell tropism of serotype 1 feline infectious peritonitis virus using the spike affinity histochemistry in paraffin‐embedded tissues

Abstract

Unlike for serotype II feline coronaviruses (FCoV II), the cellular receptor for serotype I FCoV (FCoV I), the most prevalent FCoV serotype, is unknown. To provide a platform for assessing the pattern by which FCoV I attaches to its host receptor(s), HEK293 cell lines that stably express the ectodomains of the spike (S) proteins derived from a FCoV I feline enteric coronavirus strain UU7 (FECV UU7) and a feline infectious peritonitis virus strain UU4 (FIPV UU4) were established. Using the recombinant S proteins as probes to perform S protein affinity histochemistry in paraffin-embedded tissues, although no tissue or enteric binding of FECV UU7 S protein was detected, it was found that by immunohistochemistry that the tissue distribution of FIPV UU4 S protein-bound cells correlated with that of FIPV antigen-positive cells and lesions associated with FIP and that the affinity binding of FIPV UU4 S protein on macrophages was not affected by enzymatic removal of host cell-surface sialic acid with neuraminidase. These findings suggest that a factor(s) other than sialic acid contribute(s) to the macrophage tropism of FIPV strain UU4. This approach allowed obtaining more information about both virus-host cell interactions and the biological characteristics of the unidentified cellular receptor for FCoV I.

Characterizing replication kinetics and plaque production of type I feline infectious peritonitis virus in three feline cell lines

“…The increased virus infection of Fcwf-4 CU cells could be due to any number of cellular factors; however, it is tempting to speculate that the reduced IFN-responsiveness of the Fcwf-4 CU cells relative to the Fcwf-4 ATCC cells may significantly enhance infection in the former. Further, these Fcwf-4 CU cells may express a higher density of the yet unknown type I virus receptor (Cham et al, 2017; Dye et al, 2007) and therefore may be critical in identifying the receptor or other cellular characteristics that allow for enhanced type I virus replication.…”

“…It is critical that we investigate type I FIPV in laboratory cell culture in order to understand the basic virology of natural infection, characterize type I clinical isolates, test novel therapeutics, and develop effective feline vaccines with broader coverage. However, this has been challenging because type I FCoVs cannot be easily adapted to laboratory cell culture; furthermore, the receptor for type I is not known (Cham et al, 2017; Dye et al, 2007; Hohdatsu et al, 1998), making the identification of highly permissive cell types difficult. Select type I isolates, such as the FIPV Black strain used in this study, have been adapted to growth in tissue culture at the cost of reduced in vivo virulence (Black, 1980; Pedersen, 2009; Tekes et al, 2007; Thiel et al, 2014).…”

Feline coronavirus: Insights into viral pathogenesis based on the spike protein structure and function

“…FCoV replication starts with the attachment of the virion to the host cell membrane (Fig. 2) (Cham et al, 2017). The interaction between the virus and the cell is first accomplished by binding the viral S protein to the receptor in the cellular membrane.…”

“…The interaction between the virus and the cell is first accomplished by binding the viral S protein to the receptor in the cellular membrane. This interaction is key to the determination of viral tropism and host range (Balint et al, 2012;Cham et al, 2017;Lai, 1990). Receptor usage by CoVs has been studied for several years and protein and glycan cellular receptors have been reported for different CoVs (Table 2).…”

Serotype I and II Feline Coronavirus Replication and Gene Expression Patterns of Feline Cells—Building a Better Understanding of Serotype I FIPV Biology

“…However, the in vitro propagation of FIPV I isolates in tissue culture systems has proven to be problematic, impeding forward progress in tissue-culture-based virology and pathogenesis investigations. While the primary cellular receptor utilized for cell entry by FIPV II has been identified as feline aminopeptidase N (feAPN/CD13), the primary cellular receptor utilized by FIPV I remains to be determined [ 16 , 17 , 18 , 19 ]. There are conflicting results regarding the possibility of feAPN serving as a primary cell receptor for FIPV I. Tresnan et al (1996) found that non-permissive mouse or hamster cells, transduced to stably express feAPN, became permissive to both FIPV I and II replication [ 16 ].…”