Oral Immunization with YncE-Encapsulated Chitosan Nanoparticles Confers Protective Immunity against Enterotoxigenic Escherichia coli (ETEC) in a BALB/c Murine Model.

Abstract

Background: Every year, a large number of people worldwide suffer from gastrointestinal diseases such as diarrhea. Among this population, children under five are particularly vulnerable and are at increased risk of death or malnutrition. Enterotoxigenic Escherichia coli (ETEC) is a major cause of this severe diarrhea. The bacteria first adhere to intestinal cells using colonization factors (CFs), then produce heat-stable (ST) and heat-labile (LT) toxins, which together are responsible for causing the severe diarrheal illness. Objective: to investigate the potential of the recombinant surface protein YncE, encapsulated within chitosan nanoparticles, as a novel vaccine candidate, and to evaluate its immunogenicity. Methods: The recombinant YncE gene, encoding the surface protein YncE, was cloned, expressed, purified. Successful expression and purification were confirmed via Western blot analysis. The purified recombinant protein was subsequently encapsulated within chitosan nanoparticles, and the particle size was measured. BALB/c mice were divided into five groups: recombinant protein injection, nanoparticle injection, oral nanoparticle administration, combined oral-injection nanoparticle regimen, and control. Immunogenicity was evaluated by measuring antibody titers using an enzyme-linked immunosorbent assay (ELISA). Finally, a bacterial challenge assay was conducted on all immunized groups to evaluate protective efficacy. Results: Following expression and purification, the size of the YncE-containing nanoparticles was measured. These nanoparticles successfully induced both humoral and mucosal immune responses. Furthermore, immunized mice challenged with the YncE-containing chitosan nanovaccine demonstrated protective immunity against ETEC. Conclusion: Taken together, our results show that the YncE protein-when packaged in chitosan nanoparticles-protects mice against ETEC infection. This makes YncE a strong candidate for future vaccine development.