Protective efficacy of a recombinant adenovirus expressing novel dual F and HN proteins of bovine parainfluenza virus type 3

Bovine parainfluenza virus type 3 (BPIV3) is a viral respiratory pathogen in cattle that cause significant economic losses. We generated a recombinant adenovirus expressing both the fusion (F) and hemagglutinin-neuraminidase (HN) glycoprotein of BPIV3 based on human adenovirus serotype 5 (rHAd5), named rHAd5-F + HN. Immunization with rHAd5-F + HN induced a notable humoral immune response specific to BPIV3 in both mice and calves. Serum antibodies responses were evaluated by ELISA, hemagglutination inhibition (HI), and neutralizing antibodies (Nab). After boosting immunity with rHAd5-F + HN, mice were able to produce higher levels of antibodies against the BPIV3 genotype A and genotype C strains, significantly exceeding those in the rHAd5-F and rHAd5-HN. The mice splenic CD3 ⁺ /CD8 ⁺ T lymphocytes and IL-4 ⁺ cytokine percentages were more significant in the rHAd5-F + HN group. The protective efficacy of rHAd5-F + HN was evaluated using a mouse model challenged with BPIV3. Mice immunized with rHAd5-F + HN exhibited significantly lower viral loads in the lungs and tracheas compared to the control group. Furthermore, no significant histopathological changes were observed in the lungs of mice vaccinated with rHAd5-F + HN. Also, the rHAd5-F + HN elicited a humoral immune response in calves, following the booster intramuscular injection with the rHAd5-F + HN, the serum antibodies levels against BPIV3 genotype C strain were 1:20,452, 1:1,024 and 1:426 in calves, as detected by ELISA, HI and Nab, respectively. The HI antibodies and Nab levels against BPIV3 genotype A strain were 1:213 and 1:85 in calves, respectively. These results indicated that rHAd5-F + HN effectively induced robust immunity against BPIV3 infection.