Enhanced phagocytosis and complement-mediated killing of serotype 1 following in-frame CMP-sialic acid synthetase () gene deletion.

The Gram-negative coccobacillus is a natural inhabitant of the upper respiratory tract in ruminants and the most common bacterial agent involved in bovine respiratory disease complex development. Key virulence factors harbored by are leukotoxin, lipopolysaccharide, capsule, adhesins, and neuraminidase which are involved in evading innate and adaptive immune responses. In this study, we have shown that CMP-sialic acid synthetase () is necessary for the incorporation of sialic acid onto the membrane, and inactivation of results in increased phagocytosis and complement-mediated killing of thus demonstrating that sialylation contributes to the virulence of .