Abstract
Mucosal immunization of influenza vaccine is potentially an effective approach for the prevention and control of influenza. The objective of the present study was to evaluate the ability of oral immunization with a non-recombinant Lactococcus lactis displaying HA1/L/AcmA recombinant protein, LL-HA1/L/AcmA, to induce mucosal immune responses and to accord protection against influenza virus infection in mice. The LL-HA1/L/AcmA was orally administered into mice and the immune response was evaluated. Mice immunized with LL-HA1/L/AcmA developed detectable specific sIgA in faecal extract, small intestine wash, BAL fluid and nasal fluid. The results obtained demonstrated that oral immunization of mice with LL-HA1/L/AcmA elicited mucosal immunity in both the gastrointestinal tract and the respiratory tract. The protective efficacy of LL-HA1/L/AcmA in immunized mice against a lethal dose challenge with influenza virus was also assessed. Upon challenge, the non-immunized group of mice showed high susceptibility to influenza virus infection. In contrast, 7/8 of mice orally immunized with LL-HA1/L/AcmA survived. In conclusion, oral administration of LL-HA1/L/AcmA in mice induced mucosal immunity and most importantly, provided protection against lethal influenza virus challenge. These results highlight the potential application of L. lactis as a platform for delivery of influenza virus vaccine.
Highlights
Influenza virus infection results in respiratory illnesses and contributes to a high rate of morbidity and mortality in humans, children, the elderly and immunocompromised individuals
Other factors that may influence the binding of recombinant protein onto L. lactis, including pH and temperature were not examined as these factors may affect the integrity of the cell membrane and other biological processes of L. lactis, which may affect the binding of recombinant proteins on the bacterial cell wall
The results suggested that the optimum amount of HA1/L/AcmA recombinant protein to be incubated with 1–3×109 CFU of L. lactis cells for surface display was 20 μg
Summary
Influenza virus infection results in respiratory illnesses and contributes to a high rate of morbidity and mortality in humans, children, the elderly and immunocompromised individuals. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript
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