Abstract
Salmonella enterica infections remain a challenging health issue, causing significant morbidity and mortality worldwide. Current vaccines against typhoid fever display moderate efficacy whilst no licensed vaccines are available for paratyphoid fever or invasive non-typhoidal salmonellosis. Therefore, there is an urgent need to develop high efficacy broad-spectrum vaccines that can protect against typhoidal and non-typhoidal Salmonella. The Salmonella outer membrane porins OmpC and OmpF, have been shown to be highly immunogenic antigens, efficiently eliciting protective antibody, and cellular immunity. Furthermore, enterobacterial porins, particularly the OmpC, have a high degree of homology in terms of sequence and structure, thus making them a suitable vaccine candidate. However, the degree of the amino acid conservation of OmpC among typhoidal and non-typhoidal Salmonella serovars is currently unknown. Here we used a bioinformatical analysis to classify the typhoidal and non-typhoidal Salmonella OmpC amino acid sequences into different clades independently of their serological classification. Further, our analysis determined that the porin OmpC contains various amino acid sequences that are highly conserved among both typhoidal and non-typhoidal Salmonella serovars. Critically, some of these highly conserved sequences were located in the transmembrane β-sheet within the porin β-barrel and have immunogenic potential for binding to MHC-II molecules, making them suitable candidates for a broad-spectrum Salmonella vaccine. Collectively, these findings suggest that these highly conserved sequences may be used for the rational design of an effective broad-spectrum vaccine against Salmonella.
Highlights
Salmonella enterica infections remain a significant worldwide health problem, accounting for more than 120 million cases and approximately 1 million deaths annually [1, 2]
Clades A, B, C, D, F, and H consisted of a majority of non-typhoidal serovars, while clades E and G were comprised of mostly typhoidal serovars, with clades analyzed (clade E) containing only sequences from Paratyphi A and B
It has been reported that the porin OmpC has a high degree of homology in sequence and structure among Enterobacteriaceae porins, most of these works have focused on defining the differences among amino acid sequences between the OmpC of Salmonella serovars and other Enterobacteria, but have not shown the degree of conservation of OmpC among serovars [11, 13, 15, 23, 24]
Summary
Salmonella enterica infections remain a significant worldwide health problem, accounting for more than 120 million cases and approximately 1 million deaths annually [1, 2]. These high morbidity and mortality rates are caused mainly by enteric fevers (typhoid and paratyphoid) and by non-typhoidal Salmonella (NTS) gastroenteritis [1,2,3]. Cross-reactivity through vaccination with the Ty21a vaccine can be induced against Paratyphi A, B, and Enteritidis serovars [8, 9], cross-protection has been reported only against Paratyphi B [10]. There is an urgent need for the development of novel broad-spectrum vaccines against Salmonella, which must be based on shared key structural components that induce protective immune responses against typhoidal and NTS serovars
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