Lactobacillus casei strain Shirota was selected as a bacterial carrier for the development of live mucosal vaccines against coronavirus. A 75 kDa fragment of transmissible gastroenteritis coronavirus (TGEV) spike glycoprotein S was used as the model coronavirus antigen. The S glycoprotein was cloned into a Lactobacillus/E. coli shuttle vector (pLP500) where expression and secretion of the glycoprotein S from the recombinant lactobacilli was detected via immunoblotting. Oral immunization of BALB/c mice with recombinant LcS that constitutively expresses the 75 kDa fragment of the glycoprotein S, induced both local mucosal and systemic immune responses against TGEV. Maximum titers of IgG (8.38 ± 0.19 ng/ml of serum) and IgA (64.82 ± 2.9 ng/ml of intestinal water) were attained 32 days post oral inturbation. The induced antibodies demonstrated neutralizing effects on TGEV infection.
Intragastric administration of Lactobacillus casei expressing transmissible gastroentritis coronavirus spike glycoprotein induced specific antibody production