Histopathological study of rabbit intestinal mucosa infected with a hybrid strain of Shigella dysenteriae 1 carrying LPS biosynthesis genes of Salmonella enterica serovar typhimurium

Abstract

The rfb gene cluster and the rfc gene of Salmonella enterica were introduced earlier into an invasive Shigella dysenteriae 1 strain by triparental cross. Antiserum was raised in rabbit against lipopolysaccharide isolated from the hybrid strain. Both the hybrid and the invasive S. dysenteriae 1 strain were found to have a titer of 1:2560 while for S. enterica, it was 1:640. Ligated ileal loops were prepared in rabbit, which were inoculated with 10 8 CFU ml 31 each of the hybrid strain, and invasive S. dysenteriae 1 strain used as positive control. Escherichia coli K12 was also used as a negative control. After 18 h, the fluid accumulation ratios were 0.2 and 1.6 for hybrid and invasive strains of S. dysenteriae 1, respectively. Rabbit intestinal mucosa infected with hybrid S. dysenteriae 1 strain showed the presence of intact villus tips and unruptured intestinal mucosa whereas total necrosis of intestinal mucosa and villi was observed in the S. dysenteriae 1-infected region. ß

The efficacy and immunogenicity of a live transconjugant hybrid strain of Shigella dysenteriae type 1 in two animal models

“…In our present experimental study, there was no reactogenicity to the animal model and significant efficacy was observed in rabbit model which was reconfirmed in mice pulmonary model. Our earlier studies (Biswas et al 1999;Hens et al 2003) documented that cell surface antigens like LPS, OMPs express antibacterial immunity. It has been reported that bacillary dysentery infection reacts with a strong Oantigen and the Ipa of the outer membrane represents the major immune stimulating moieties on the surface of Shigella (Chowers et al 2007;Shim et al 2007).…”

“…For more than 50 years, scientists have been trying to come up with suitable candidate vaccines such as inactivated Shigella vaccines (Osorio et al 2007), live attenuated vaccines (Venkatesan and Ranallo 2006;Ranallo et al 2007;McKenzie et al 2008;Sadorge et al 2008), ribosomal-based vaccines (Shim et al 2007) and conjugate vaccines (Cohen et al 1997;Chowers et al 2007) against shigellosis. In our previous two publications (Biswas et al 1999;Hens et al 2003), we have shown that Shigella dysenteriae type 1 (LTSH) strain carrying lipopolysaccharide (LPS) biosynthesis gene of Salmonella enterica serover typhimurium was unable to invade the HeLa cell and rabbit intestinal mucosa, and it was Sereny negative. Our present study is to determine the protective efficacy of LTSH strain after oral and intranasal immunization in two conventional animal models.…”