Protection in a mouse peritonitis model mediated by iron-regulated outer-membrane protein of Salmonella typhi coupled to its Vi antigen

Abstract

Vi polysaccharide and iron-regulated outer-membrane proteins (IROMPs) were extracted and purified from the standard strain of Salmonella typhi, Ty2. These were then conjugated by chemical coupling using the carbodimide method. Vi-IROMP conjugate was tested for its ability to protect against colonization by S. typhi in different organs. Mice immunized with 2 . 5 ìg Vi-IROMP conjugate showed the most protection, as the least bacterial colonization of spleen, liver and Peyer's patches was observed. Peritoneal macrophages obtained from conjugate-treated mice phagocytosed bacteria efficiently. Circulating antibodies and the delayed type hypersensitivity response elucidated by mouse foot-pad swelling was significantly higher in conjugate-treated animals. These results clearly demonstrate that an IROMP and polysaccharide conjugate of S. typhi prepared from the same strain has the potential to protect animals against challenge.

Salmonella typhi iron-regulated outer-membrane proteins cause oedema and hyperalgesia during inflammation induced in a rat model

“…The expression of three distinct bands in the molecular mass range from 66 to 97 kDa is in agreement with an earlier study (Fernandez-Beros et al, 1989) of IROMPs from the same strain (S. typhi Ty2). However, it differs from the profile shown recently by Chibber & Bhardwaj (2004) using the same strain. The dipyridyl used in that study may not have been efficient in causing the chelation of iron present in the medium.…”

“…While evaluating any antigen for its vaccine potential, it is desirable to determine the minimum concentration of the antigen that gives a protective effect. It has been shown by Chibber & Bhardwaj (2004) that 50 ìg of IROMPs and 2 . 5 ìg of Vi-IROMPs conjugate of S. typhi gives protection in a mouse peritonitis model.…”

Immunological evaluation of Vi capsular polysaccharide of Salmonella enterica subsp. Typhi vaccine by serum bactericidal assay

“…It has been shown that the S. Typhi Vi capsular polysaccharide (Vi-CPS) subunit vaccine can prevent typhoid fever. A single intramuscular injection of this vaccine conferred about 65 and 72 % protection in South Africa and Nepal, respectively (Acharya et al, 1987;Klugman et al, 1987;Szu et al, 1994;Tang et al, 2003;Chibber & Bhardwaj, 2004). The Vi-CPS vaccine has now been licensed in .93 countries worldwide, although it is not commonly used as part of vaccination programmes in developing countries.…”

Protective efficacy and immunogenicity of Escherichia coli K13 diphtheria toxoid conjugate against experimental ascending pyelonephritis

“…Since anticapsular antibodies have been shown to be present and protective in clinical and experimental studies [26][27][28], surface-exposed capsular polysaccharide (CPS) of E. coli is therefore considered an important virulence determinant [4,29,30]. Since CPS alone is a T independent antigen, for better immunogenicity there is a need to couple it with carrier proteins to make it T dependent [31][32][33][34]. Over the years, different carrier proteins have been used for coupling by different workers [35].…”