Effect of active vitamin D3 on the expression of antimicrobial peptide genes in experimental calf pneumonia

The outbreak of calf pneumonia in herds occurs due to different pathogens. Vitamin D3 displays a regulatory effect on different cells, especially its pro-differential biological function and stimulates antimicrobial peptides. In the present study, the effects of vitamin D3 on the expression of antimicrobial peptides in experimental pasteurellosis in calves were assessed. Ten Holstein calves (2-4 months old) were randomly divided into two groups. Prepared Pasteurella multocida (3×109 CFU/mL) was inoculated in the trachea of all calves and Vitamin D3 was injected only in the treatment group following confirmation of pneumonia. Blood samples and broncho-alveolar lavage fluids were obtained from both groups at different time intervals and the peripheral blood mononuclear cells were isolated to evaluate the antimicrobial peptides gene expression. The expression of CD4, Cathelicidin, and Defensins genes was measured in vitro conditions following the addition of 10-6, 10-7 and 10-8 molar of vitamin D3. Defensins and CD4 gene expressions revealed a significant difference in the two groups, at the 48, 72, 96, and 120 hours after the challenge time, while the Cathelicidin gene was not expressed in both experimental groups. Surprisingly, increased expression of Cathelicidin, Defensins, and CD4 was observed at a concentration of 10-6 M of vitamin D3. According to the results of this study, vitamin D3 had positive effects on the immune system which was observed as significant improvement in the clinical symptoms of treated calves. The expression of lung-related Defensins and CD4 in vivo and in vitro approved the immunomodulatory effects of vitamin D3 but the gene expression of Cathelicidin is probably related to prescribing higher doses of vitamin D3.