Feline herpesvirus-1 (FHV-1) is responsible for approximately 50% of diagnosed viral upper respiratory tract disease in cats. The virus infects and replicates in the epithelial cells located in upper respiratory tract. Commercial vaccines do not protect cats from the infection itself or development of latency. Previously, our lab developed a cell culture model using primary feline respiratory epithelial cells (pFRECs) to study respiratory innate immunity to FHV-1 and FHV-1 deletion mutants. However, the numbers of pFRECs that can be obtained per cat is limited. To improve the usage of respiratory epithelial 3D cultures in FHV-1 research, the present study immortalized feline respiratory epithelial cells (iFRECs) and characterized them morphologically and immunologically and evaluated the response to FHV-1 infection. Immortalization was achieved by transduction with Lenti-SV40T and Lenti-HPV E6/E7. Immortalized FRECs could be successfully subcultured for >20 passages, with positive gene expression of SV40T and HPV E6/E7. Immortalized FRECs expressed similar innate immunity-associated genes compared to pFRECs, including genes of Toll-like receptors (TLR1-9), interferon induced genes (OAS1, OAS3, IFI44, IFITM1, IFIT1), chemokines (CCL2, CCL3, CXCL8), pro-inflammatory and regulatory cytokines (IL-6, IL-4, IL-5, IL-12, and IL-18), and antimicrobials (DEFβ10, DEFβ4B). Finally, FHV-1 inoculation resulted in characteristic cytopathic effects starting at 24 hpi, with more than 80% cells detached and lysed by 72 hpi. Overall FHV-1 growth kinetics in iFRECs resembled the kinetics observed in pFRECs. In conclusion, we demonstrated that iFRECs are a useful tool to study feline respiratory disease including but not limited to FHV-1.

Mast cells are important immune modulators of stress-related gastrointestinal (GI) disorders. Our previous studies investigating early life stress in piglets showed that histamine, a major mast cell granule mediator is released within minutes of early weaning stress and is followed by increased intestinal mucosal expression of histamine receptor subtypes. The precise contribution of histamine to stress-induced GI immune responses is unknown. The objective of this study was to test the hypothesis that stress-induced intestinal immune response is mediated through the histamine 1 receptor (H1R). Fifteen-day-old female Yorkshire piglets were administered either saline vehicle or the H1R antagonist, desloratadine (2 mg/kg; intramuscular), 30 minutes prior to early weaning stress. At weaning, piglets were weaned from their dams and housed in nursery pens with ad libitum access to water. At 24 hours post-weaning, mid-jejunum and mesenteric lymph nodes (MLN) were collected for subsequent qPCR gene expression as well as IHC localization and protein expression analyses. Unweaned control piglets remained with the sow and were collected immediately at weaning. Gene expression for H1R was not influenced by weaning; however, immunohistochemical analysis of H1R revealed increased expression and localization in lamina propria cells and myofibroblasts in jejunal villi and expression in the longitudinal and circular muscle layers in early weaned piglets. In the MLN, weaning increased the expression of TNFα, TGFβ, and β-Integrin. This response was reduced in the group treated with the H1R antagonist. Together, these data demonstrate that histamine via H1R plays an important role in early weaning stress-induced intestinal immune responses.