Immunogenicity of culture filtrated proteins and whole-cell killed formalin of Listeria monocytogenes to induced cellular immune response in vivo.

BACKGROUND

Listeria monocytogenes (LM) is a life-threatening bacterium affecting many individuals worldwide, including elderly people, pregnant women, and immune-deficient patients.

AIM: Whole-cell killed formalin of LM antigens (WKLMAgs) and Listeria culture filtrated proteins (LCFPs) against challenge-attenuated LM after two booster doses (0 and 14 days) of immunization act as an antigen activating a high level of IgG3, IgM, CXCL2, and IL-1 beta.

METHODS

Forty male rats were randomly assigned to four groups. The first group served as a control negative, while the second positive (+) control was inoculation orally 1 ml with virulent (1 × 107 colony forming unit CFU/ml) of LM on day 28, whereas the other two groups were injected with 1-ml WKLMAgs and 1-ml LCFPs in two subcutaneously doses with day 14 intervals, with at day 28 a challenged effective dose (1 × 107 CFU/ml) of virulent LM. Serum blood parameters were measured. During the 35 days, the euthanized animal histopathology studies were performed on the spleen, liver, small intestine, and brain.

RESULTS

The current study indicated a significant difference between WKLMAgs and LCFPs for serological tests Immunoglobulin (Ig) M, chemokine (C-X-C motif) ligand 2, Ig G3, and interleukin-1 beta compared to both negative and positive controls at P < 0.001. Additionally, the WKLMAgs and LCFPs led to a decrease in the histopathological changes of organs such as (brain, spleen, liver, and intestine) compared to the positive control, which affected the organs with microgranuloma, with a pathological difference between the WKLMAgs and LCFPs compared to the negative control group.

CONCLUSION

Both WKLMAgs and LCFPs are capable to be as a vaccine candidate antigen for the induction of protective immunity against L. monocytogenes.