Immunohistological identification/localization of immunomodulating neuropeptides [vasoactive intestinal polypeptide (VIP) and substance P (SP)] and enzyme nitric oxide synthase (NOS) as well as histomorphometric analyses of kinetics of their release and development of respective nerve fibers density during postnatal ontogenesis of porcine intestinal mucosal immune system (IMIS), were performed in order to assess the role of these molecules involved in maturation of the IMIS. The kinetcs of reactions to VIP, SP and NOS were demonstrated in the samples of jejunum and ileum from conventionally reared pigs. The samples were obtained at 0, 7, 14, 21, 28, 35, 42 and 49 days of age and processed for immunohistological staining. The VIP+ reaction was prevalently visible in the epithelial layer, lamina propria and Lieberkühn crypts (Lc) but also in the submucosa and lamina muscularis along blood and lymphatic vessels. The SP+ fibers were regularly distributed along enteric neurons in the muscular layer. The reaction to NOS was demonstrated in both mucosa and submucosa of ileum and jejunum and in the ileal Peyer's patches (PP). Intensity of the reaction was more pronounced in the epithelial layer and numerous NOS+ cells were observed around the Lc and inside the follicles of the PP. Also, we have noticed NOS+ blood vessels, particular neurons and nerve fibers in the submucosa and muscular layer of the small intestine. By analyzing quantitative patterns of SP+, VIP+ fibers and release of NOS we have concluded that intensity of their reactions gradually increases with age, except a short period of stagnation after weaning (at age of 28 days), reaching the highest values in the pigs aged between 42 and 49 days. The values obtained by Sperman rank order correlation test (rs) between days of age of pigs and intensity of the reactions in their jejunum/ileum to VIP (rs=0.97/0.95), SP (rs=0.97/0.97) and NOS (rs=0.98/0.95), respectively, showed positive correlations (P<0.05) according to Roemer Orphal scale. Current study showed that post-natal development of porcine IMIS was accompanied by a substantial increase in the secretion of neuropeptides/enzyme tested and that these molecules may participate in the functional maturation of immunoregulatory/bactericidal mechanisms of the local (intestinal) immune defense in young pigs.

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The presented experiments were aimed to cultivate and multiplicate HVT FC-126 in the PLA (Adult pig kidney) and GL-4 (Gerbil kidney) cell lines. Two different HVT FC-126 vaccine strains were used: Marikal SPF (Veterina d.o.o., Croatia) and Lyomarex (Merial, USA). They were adapted to the PLA and GL-4 cell lines. After adaptation, they were titrated on PLA (TCID50 24.23) and GL-4 (TCID50 24.96). On both cell lines they show similar CPE (cytophatic effect). The difference between them was detected using Real Time PCR, which was also positive by agarose gel analysis for the virus contained in Lyomarex, but not in the Marikal SPF. It can be concluded that both cell lines are sensitive to HVT FC-126 and the virus can be multiplied in high titers though much lower than in the calf intestinal epithelial cell line (CIEB) cells (TCID50 27.93)