title: Simplest identification, O-specific polysaccharide purification and antigenic evaluation of Salmonella enterica serovar Typhi Vi negative isolate.
abstract: Currently licensed typhoid vaccines are based on Vi capsular polysaccharides. Recent molecular reports from typhoid endemic countries state that Salmonella enterica serovar Typhi (S. Typhi) Vi negative strains occur naturally and cause typhoid fever which is indistinguishable from disease caused by Vi positive strains. Vaccine based on Vi polysaccharide may not protect patients if the invading S. Typhi are negative for Vi. The lipopolysaccharide (LPS) is an essential component of S. Typhi outer membrane in which O-specific polysaccharide (OSP) is a protective antigen and universal candidate for vaccine development. In this study, S. Typhi Vi negative isolates were discriminated from Vi positive isolates through a duplex PCR using primers of fliC-d (599bp) and tviA (495bp) genes. The LPS of S. Typhi Vi negative isolates was extracted by hot phenol method and OSP was purified by core hydrolysis. The yield of extracted LPS was 91 mg/L and that of purified OSP was 49.14 mg/L of culture broth. LPS showed ladder like appearance by zinc imidazole staining following SDS-PAGE. Whole cell challenged mice sera were used for in vitro antigenicity evaluation of the purified LPS and OSP. The antigenicity was found adequate by immunodiffusion assay. To our knowledge, this is the first report of purification and antigenic evaluation of LPS of a Vi negative S. Typhi isolate. The purified OSP from S. Typhi Vi negative isolate may be coupled with a carrier protein to produce universal low cost conjugate vaccine candidates for use in typhoid endemic regions.
authors.affiliation: Health Biotechnology Division, National Institute for Biotechnology and Genetic Engineering (NIBGE), Faisalabad, Pakistan affiliated with Pakistan Institute of Engineering and Applied Sciences (PIEAS), Islamabad, Pakistan ; Department of Biotechnology, Abdul Wali Khan University, Mardan.
authors.forename: Muhammad
authors.initials: M
authors.lastname: Salman
authors.affiliation: Health Biotechnology Division, National Institute for Biotechnology and Genetic Engineering (NIBGE), Faisalabad, Pakistan affiliated with Pakistan Institute of Engineering and Applied Sciences (PIEAS), Islamabad, Pakistan.
authors.forename: Aamir
authors.initials: A
authors.lastname: Ali
authors.affiliation: Department of Biotechnology, Mirpur University of Science & Technology (MUST), Mirpur, AJK, Pakistan.
authors.forename: Abdul
authors.initials: A
authors.lastname: Jabbar
authors.affiliation: Health Biotechnology Division, National Institute for Biotechnology and Genetic Engineering (NIBGE), Faisalabad, Pakistan affiliated with Pakistan Institute of Engineering and Applied Sciences (PIEAS), Islamabad, Pakistan.
authors.forename: Yasra
authors.initials: Y
authors.lastname: Sarwar
authors.affiliation: Health Biotechnology Division, National Institute for Biotechnology and Genetic Engineering (NIBGE), Faisalabad, Pakistan affiliated with Pakistan Institute of Engineering and Applied Sciences (PIEAS), Islamabad, Pakistan.
authors.forename: Moazur
authors.initials: M
authors.lastname: Rahman
authors.affiliation: Health Biotechnology Division, National Institute for Biotechnology and Genetic Engineering (NIBGE), Faisalabad, Pakistan affiliated with Pakistan Institute of Engineering and Applied Sciences (PIEAS), Islamabad, Pakistan.
authors.forename: Mazhar
authors.initials: M
authors.lastname: Iqbal
authors.affiliation: Department of Pathology, The University of Faisalabad, Faisalabad.
authors.forename: Abdul
authors.initials: A
authors.lastname: Haque
keywords: O-Specific polysaccharides; Salmonella Typhi Vi negative; typhoid vaccine