Use of a Whole Genome Approach To Identify Vaccine Molecules Affording Protection against Streptococcus pneumoniae Infection

Abstract

Microbial targets for protective humoral immunity are typically surface-localized proteins and contain common sequence motifs related to their secretion or surface binding. Exploiting the whole genome sequence of the human bacterial pathogen Streptococcus pneumoniae, we identified 130 open reading frames encoding proteins with secretion motifs or similarity to predicted virulence factors. Mice were immunized with 108 of these proteins, and 6 conferred protection against disseminated S. pneumoniae infection. Flow cytometry confirmed the surface localization of several of these targets. Each of the six protective antigens showed broad strain distribution and immunogenicity during human infection. Our results validate the use of a genomic approach for the identification of novel microbial targets that elicit a protective immune response. These new antigens may play a role in the development of improved vaccines against S. pneumoniae.Streptococcus pneumoniae (the pneumococcus) is the leading cause of bacterial sepsis, pneumonia, meningitis, and otitis media in young children in the United States. Annually, 7,000,000 middle-ear infections are ascribed to this organism (4). The vaccines in current use are formulations of capsular carbohydrate from the 23 serotypes responsible for 85 to 90% of infections in the United States, but these vaccines are poorly efficacious in infants and the elderly, the populations that are most at risk (1). A heptavalent-capsular-carbohydrate vaccine conjugated to the protein carrier CRM197 has been shown to be well tolerated and efficacious against invasive disease caused by the seven vaccine serotype strains (3) and has recently been approved for use in young children. However, this type of vaccine has several potential limitations, including serotype replacement by strains that are not represented (14).The advent of whole-genome sequencing of microbes, including microbial pathogens, has revolutionized the methods by which these organisms are studied and has heightened expectations regarding the ability to predict potential targets for antimicrobial agents and vaccines (2,12,20). We combined sequence scanning for prediction of surface-localized proteins with an animal model which allowed us to directly screen proteins for vaccine efficacy to identify novel vaccine candidates from the genome sequence of S. pneumoniae. Here we describe the use of a clinically relevant animal model for the evaluation of the vaccine efficacy of proteins identified from the genome sequence of pneumococcus. This approach was validated by the discovery of five previously unidentified genes whose products induced immune responses that protected mice from pneumococcal infection. Similar sequence scanning methods were recently used to identify potential vaccine candidates from the genomic sequence of the gram-negative pathogen Neisseria meningitidis (21) predicted by in vitro correlates of vaccine effectiveness. Here we expand upon the use of genomics to directly demonstrate vaccine efficacy in an animal model for...

Mining the Moraxella catarrhalis Genome: Identification of Potential Vaccine Antigens Expressed during Human Infection

“…This approach successfully identified ORFs corresponding to 10 previously identified OMPs of M. catarrhalis. The proportion of ORFs predicted to be on the surface (348 of 1,849) matched well with the results of similar analyses of other bacteria (23,50,51).…”

The pathogenic equine streptococci

“…However, capsular polysaccharaide is often poorly immunogenic. Protein antigens including PspA, pneumolysin, PsaA, autolysin, the neuraminidases, NanA and B, and at least six other surface proteins reactive with human convalescent serum and mouse protective [53] may have potential as vaccine components.…”

Transcriptional regulation, occurrence and putative role of the Pht family of Streptococcus pneumoniae

“…PhtE is a longer protein, the only one with six repeats of the histidine triad motif. In mouse immunization studies, all members of the Pht family have been shown to afford a high level of protection to subsequent pneumococcal challenge with a number of different strains/serotypes Godfroid et al, 2011;Hamel et al, 2004;Ogunniyi et al, 2007;Wizemann et al, 2001;Zhang et al, 2001).…”