**Development of Feline Ileum- and Colon-Derived Organoids and Their Potential Use to Support Feline Coronavirus Infection**

### **Gergely Tekes 1,\*,**†**, Rosina Ehmann 2, Steeve Boulant 3,4 and Megan L. Stanifer 5,\***


Received: 14 August 2020; Accepted: 10 September 2020; Published: 12 September 2020

**Abstract:** Feline coronaviruses (FCoVs) infect both wild and domestic cat populations world-wide. FCoVs present as two main biotypes: the mild feline enteric coronavirus (FECV) and the fatal feline infectious peritonitis virus (FIPV). FIPV develops through mutations from FECV during a persistence infection. So far, the molecular mechanism of FECV-persistence and contributing factors for FIPV development may not be studied, since field FECV isolates do not grow in available cell culture models. In this work, we aimed at establishing feline ileum and colon organoids that allow the propagation of field FECVs. We have determined the best methods to isolate, culture and passage feline ileum and colon organoids. Importantly, we have demonstrated using GFP-expressing recombinant field FECV that colon organoids are able to support infection of FECV, which were unable to infect traditional feline cell culture models. These organoids in combination with recombinant FECVs can now open the door to unravel the molecular mechanisms by which FECV can persist in the gu<sup>t</sup> for a longer period of time and how transition to FIPV is achieved.

**Keywords:** feline coronavirus; feline enteric coronavirus; FECV; feline infectious peritonitis virus; FIPV; feline intestinal organoids
