title: Identification of in vivo-induced bacterial proteins during human infection with Salmonella enterica serotype Paratyphi A.
abstract: Salmonella enterica serotype Paratyphi A is a human-restricted pathogen and the cause of paratyphoid A fever. Using a high-throughput immunoscreening technique, in vivo-induced antigen technology (IVIAT), we identified 20 immunogenic bacterial proteins expressed in humans who were bacteremic with S. Paratyphi A but not those expressed in S. Paratyphi A grown under standard laboratory conditions. The majority of these proteins have known or potential roles in the pathogenesis of S. enterica. These include proteins implicated in cell adhesion, fimbrial structure, adaptation to atypical conditions, oxidoreductase activity, proteolysis, antimicrobial resistance, and ion transport. Of particular interest among these in vivo-expressed proteins were S. Paratyphi A (SPA)2397, SPA2612, and SPA1604. SPA2397 and SPA2612 are prophage related, and SPA1604 is in Salmonella pathogenicity island 11 (SPI-11). Using real-time quantitative PCR (RT-qPCR), we confirmed increased levels of mRNA expressed by genes identified by IVIAT in a comparison of mRNA levels in organisms in the blood of bacteremic patients to those in in vitro cultures. Comparing convalescent- to acute-phase samples, we also detected a significant increase in the reaction of convalescent-phase antibodies with two proteins identified by IVIAT: SPA2397 and SPA0489. SPA2397 is a phage-related lysozyme, Gp19, and SPA0489 encodes a protein containing NlpC/P60 and cysteine, histidine-dependent amidohydrolase/peptidase (CHAP) domains. In a previous study utilizing a different approach, we found that transcripts for 11 and 7 of the genes identified by IVIAT were detectable in organisms in the blood of humans in Bangladesh who were bacteremic with S. Paratyphi A and Salmonella enterica serovar Typhi, respectively. S. Paratyphi A antigens identified by IVIAT warrant further evaluation for their contributions to pathogenesis and might have diagnostic, therapeutic, or preventive relevance.
authors.affiliation: International Centre for Diarrhoeal Disease Research, Bangladesh, Dhaka, Bangladesh.
authors.forename: Mohammad Murshid
authors.initials: MM
authors.lastname: Alam
authors.forename: Lillian L
authors.initials: LL
authors.lastname: Tsai
authors.forename: Sean M
authors.initials: SM
authors.lastname: Rollins
authors.forename: Alaullah
authors.initials: A
authors.lastname: Sheikh
authors.forename: Farhana
authors.initials: F
authors.lastname: Khanam
authors.forename: Meagan Kelly
authors.initials: MK
authors.lastname: Bufano
authors.forename: Yanan
authors.initials: Y
authors.lastname: Yu
authors.forename: Ying
authors.initials: Y
authors.lastname: Wu-Freeman
authors.forename: Anuj
authors.initials: A
authors.lastname: Kalsy
authors.forename: Tania
authors.initials: T
authors.lastname: Sultana
authors.forename: M Abu
authors.initials: MA
authors.lastname: Sayeed
authors.forename: Nusrat
authors.initials: N
authors.lastname: Jahan
authors.forename: Regina C
authors.initials: RC
authors.lastname: LaRocque
authors.forename: Jason B
authors.initials: JB
authors.lastname: Harris
authors.forename: Daniel T
authors.initials: DT
authors.lastname: Leung
authors.forename: W Abdullah
authors.initials: WA
authors.lastname: Brooks
authors.forename: Stephen B
authors.initials: SB
authors.lastname: Calderwood
authors.forename: Richelle C
authors.initials: RC
authors.lastname: Charles
authors.forename: Firdausi
authors.initials: F
authors.lastname: Qadri
authors.forename: Edward T
authors.initials: ET
authors.lastname: Ryan
mesh_terms: D000942:Antigens, Bacterial / Q000096:biosynthesis / Q000097:blood* / Q000276:immunology; D016470:Bacteremia / Q000276:immunology / Q000382:microbiology*; D001426:Bacterial Proteins / Q000096:biosynthesis / Q000097:blood* / Q000276:immunology* / Q000302:isolation & purification; D006801:Humans; D010284:Paratyphoid Fever / Q000175:diagnosis / Q000276:immunology / Q000382:microbiology*; D039002:Prophages; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012482:Salmonella paratyphi A / Q000235:genetics / Q000276:immunology* / Q000821:virology
chemical_list: D000942:Antigens, Bacterial; D001426:Bacterial Proteins; D012333:RNA, Messenger