ARS | Publication request: Characteristics of Cell-mediated, Anti-listerial Immunity Induced by A Naturally Avirulent Listeria monocytogenes Serotype 4a Strain HCC23

Submitted to: Archives Of Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 27, 2007
Publication Date: September 1, 2007
Citation: Liu, D., Lawrence, M.L., Pinchuk, L.M., Ainsworth, A.J., Austin, F.W. 2007. Characteristics of Cell-mediated, Anti-listerial Immunity Induced by A Naturally Avirulent Listeria monocytogenes Serotype 4a Strain HCC23. Archives Of Microbiology. 188(3):251-6.

Interpretive Summary: The foodborne pathogen, L. monocytogenes, can cause the disease listeriosis in humans and controlling L. monocytogenes is an important food safety issue. However, not all strains of L. monocytogenes are virulent. In order to better understand factors affecting virulence of L. monocytogenes we compared immume responses in mice to a virulent L. monocytogenes strain (EGD) and two avirulent strains (HCC23 and ATCC 15313). The virulent strain (EGD) induced increased production of interferon and natural killers cells in mice compared to the avirulent strains. The virulent strain (EGD) and the avirulent strain (HCC23) were similar in that they both grew readily in macrophages and produced short and long term protection against experimental infection with virulent L. monocytogenes. The other avirulent strain (ATCC 15313) did not appear to induce significant immune system response and did not protect against listeriosis. The information provides a better understanding of factors influencing virulence of L and the host immune response.

Technical Abstract: The characteristics of cell-mediated, anti-listerial immune response initiated by an avirulent Listeria monocytogenes serotype 4a strain HCC23 was assessed. Similar to virulent strain EGD, avirulent strain HCC23 grew readily within macrophage-like J774 cells, but nonhemolytic strain ATCC 15313 did not. Compared with EGD, HCC23 induced a relatively low level of gamma interferon (IFN-gamma) in mice, and ATCC 15313 stimulated no detectable IFN-gamma. The percentages of gated CD4 T cells from mice immunized with EGD and HCC23 showed a notable drop (to 30%) at 21 days post exposure in comparison with that (about 50%) from ATCC 15313-injected or untreated mice; and the percentage of gated NK cells from EGD-immunized group was markedly higher than those from other treatment groups. Mice immunized with HCC23 and EGD developed an equally strong protective immunity against listeriosis that was effective in both short and long terms, but those injected with ATCC 15313 or saline succumbed to listeriosis within 6 days of challenge.