Protective Enterotoxigenic Escherichia coli Antigens in a Murine Intranasal Challenge Model

Abstract

Enterotoxigenic Escherichia coli (ETEC) is an endemic health threat in underdeveloped nations. Despite the significant effort extended to vaccine trials using ETEC colonization factors, these approaches have generally not been especially effective in mediating cross-protective immunity. We used quantitative proteomics to identify 24 proteins that differed in abundance in membrane protein preparations derived from wild-type vs. a type II secretion system mutant of ETEC. We expressed and purified a subset of these proteins and identified nine antigens that generated significant immune responses in mice. Sera from mice immunized with either the MltA-interacting protein MipA, the periplasmic chaperone seventeen kilodalton protein, Skp, or a long-chain fatty acid outer membrane transporter, ETEC_2479, reduced the adherence of multiple ETEC strains differing in colonization factor expression to human intestinal epithelial cells. In intranasal challenge assays of mice, immunization with ETEC_2479 protected 88% of mice from an otherwise lethal challenge with ETEC H10407. Immunization with either Skp or MipA provided an intermediate degree of protection, 68 and 64%, respectively. Protection was significantly correlated with the induction of a secretory immunoglobulin A response. This study has identified several proteins that are conserved among heterologous ETEC strains and may thus potentially improve cross-protective efficacy if incorporated into future vaccine designs.

Immunization with the MipA, Skp, or ETEC_2479 Antigens Confers Protection against Enterotoxigenic E. coli Strains Expressing Different Colonization Factors in a Mouse Pulmonary Challenge Model

“…We found previously that immunizing mice with MipA, Skp, and ETEC_2479 was protective against homologous challenge with ETEC H1407 (Kumar et al, 2015). Furthermore, despite the conservation of these antigens among Gram-negative bacteria, mouse health was not negatively impacted nor were significant alterations to the mouse intestinal microbiota observed as a function of vaccination (Hays et al, 2016).…”

“…We have been interested in identifying and characterizing ETEC proteins that might serve as potential vaccine targets (Kumar et al, 2015; Hays et al, 2016). Many previous vaccine strategies have focused on heterogeneous surface structures known as colonization factors (CFs; Fleckenstein et al, 2014).…”

“…We have been characterizing the potential protective efficacy of the ETEC MipA, Skp, and ETEC_2479 proteins in a pulmonary challenge model (Kumar et al, 2015). We focused on these antigens after performing proteomic studies of ETEC H10407 (Kumar et al, 2015).…”

“…We focused on these antigens after performing proteomic studies of ETEC H10407 (Kumar et al, 2015). MipA belongs to a family of proteins involved in remodeling peptidoglycan.…”

“…ETEC_2479 is predicted to function as an outer membrane porin (Kumar et al, 2015). While the potential role of these proteins in ETEC virulence is not apparent, it is known that these proteins are conserved among pathogenic and non-pathogenic E. coli (Kumar et al, 2015; Hays et al, 2016). It is also known that MipA can be detected in immunoblots using sera from mice and humans (Roy et al, 2010).…”