Immunity in listeriosis

In this review modern concepts on the formation of specific immunity to listeriosis are presented. Numerous data indicate that in Listeria monocytogenes virulence and the capacity for inducing specific protection is ensured by the protein listeriolysin O. The importance of gamma-interferon, tumor necrosis factor alpha, interleukin 12 and other mediators in ensuring the differentiation of (CD4(+) T-cells into Th1-helpers and cytotoxic T-lymphocytes in animals infected with L. monocytogenes is described in detail. The safety and effective preparations for specific prophylaxis of listeriosis were not developed. Hopeful results have been obtained in experiments on the immunization of mice with killed bacteria with listeriolysin O or interleukin 12. Works describing the use of modified L. monocytogenes strains as vectors for the creation of vaccines against different infections seem to show good prospects.     

Type I IL-1 receptor blockade exacerbates murine listeriosis.

It was found that IL-1 is produced in livers and spleens of mice shortly after the i.v. injection of a sublethal or lethal Listeria monocytogenes inoculum. In sublethally infected mice, IL-1 was present in infected livers and spleens by the end of the first day of infection. Thereafter, the amounts of IL-1 in these organs increased and decreased in concordance with bacterial numbers. IL-1 was not present in the peripheral circulation of mice during sublethal listeriosis, but was present in the blood late in lethal infection. Evidence showing that IL-1 plays a role in antibacterial resistance early in listeriosis was obtained through the use of 35F5 mAb that binds to the murine type I IL-1R and functions to block IL-1 alpha and IL-1 beta actions. Blockade of the type I IL-1R by the 35F5 mAb results in greatly enhanced bacterial growth in the livers and spleens of mice that had received a sublethal Listeria inoculum. Consistent with the exacerbation of listeriosis caused by 35F5 mAb, but in contrast to the effect of 35F5 mAb in other murine models, 35F5 mAb-treated mice exhibit markedly elevated levels of IL-6 in their circulation and infected organs.     

History and epidemiology of listeriosis

Listeriae are used as a tool by different specialities in biomedical research. There are now at least four major fields of interest in LISTERIA: (1). the role in medical microbiology: Listeria monocytogenes causes severe diseases of men and animals and is difficult to treat; (2). the role in food microbiology: Listeria is a food-borne pathogen and is found in various food items; (3). the role in cell biology: L. monocytogenes is a facultative intracellular parasite having an intense cross-talk and interactions with the host cell; (4). the role in immunology: basic knowledge on cell-mediated immunity has been acquired through the model of listeriosis. This paper presents information on the past and the actual situation in research on Listeria and listeriosis.     

The epidemiology of human listeriosis

Listeriosis is a serious invasive disease that primarily afflicts pregnant women, neonates and immunocompromised adults. The causative organism, Listeria monocytogenes, is primarily transmitted to humans through contaminated foods. Outbreaks of listeriosis have been reported in North America, Europe and Japan. Soft cheeses made from raw milk and ready-to-eat meats are high risk foods for susceptible individuals. Efforts by food processors and food regulatory agencies to aggressively control L. monocytogenes in the high risk foods have resulted in significant decreases in the incidence of sporadic listeriosis.