Intestinal infection of BALB/c mice with Yersinia enterocolitica O9 causes major modifications in phenotype and functions of spleen cells

Abstract

INTRODUCTIONYersinia enterocolitica is a common cause of intestinal infections in humans (Cover & Aber, 1989 ;Bottone, 1997). Extraintestinal and systemic infections are most often caused by strains belonging to so-called highvirulence serotypes, such as serotype O8 (Heesemann et al., 1993), although low-virulence serotypes, such as O3 and O9, may occasionally cause bactaeremia in patients with iron overload or other underlying diseases (Rabson et al., 1975 ;Bouza et al., 1980). The presence of a 70 kb plasmid (pYV) that carries a number of virulence genes is required for Y. enterocolitica strains to become virulent (Cornelis et al., 1998).Non-septic sequelae of human yersiniosis include reactive arthritis, erythema nodosum, Reiter's syndrome, autoimmune thyroiditis and other immunopathological complications (Winblad, 1973 ;Bech et al., 1974 ;Toivanen et al., 1985). Alterations in the immune networks following infection with a number of microorganisms are likely to play a role in the genesis of immunopathological diseases (Schwartz, 1993). The effects of experimental yersiniosis on immunity parameters, such as the size of spleen cell subsets or the production of immune cytokines, have been documented in mice infected with serotype O8 strains (Autenrieth et al., 1994 ; Bohn et al., 1998). In comparison, lowvirulence serotypes have received little attention, although they possess immunomodulatory properties (Ruiz-Bravo et al., 1985. In humans, enteric colonization with low-virulence serotypes may persist for periods of up to 14 weeks without symptoms (Morris et al., 1991) ; however, there is no information available about the possible effects of the intestinal carriage of these strains on the immune condition of the hosts. In this study, we used a murine intestinal infection model (Ruiz-Bravo et al., 1999) A. RUIZ-BRAVO, E. MORENO and M. JIME; NEZ-VALERA of mice infected with a low-virulence serotype of Y. enterocolitica. METHODSMice. Six-to eight-week-old female BALB\c mice were provided by the Unit of Animal Experimentation, University of Granada (Granada, Spain). They were maintained under pathogen-free conditions. Experimental infection with Y. enterocolitica. Strain IP383 of Y. enterocolitica was used in all experiments. It is a serotype O9 strain that carries the virulence plasmid pYV (Mazigh et al., 1983). Bacteria were grown on Tryptic soy agar (Difco) at 25 mC for 24 h, harvested, washed and resuspended in sterile water to obtain 10* bacteria ml − ". Mice were infected via the oral route, as described previously (Ruiz-Bravo et al., 1999). Phenotypic analysis of spleen cells. Spleens were homogenized in PBS containing 1 % (w\v) BSA (Sigma). Splenocytes were sedimented by centrifugation, resuspended in red blood cell lysing buffer (Sigma) for 10 min, washed and resuspended in PBS containing BSA. Cell suspensions from individual mice were adjusted to 10( viable cells ml − ". Aliquots (100 µl) were incubated with 5 µl fluorescein-isothiocyanate-conjugated monoclonal antibodies. The monoclonal antibodies use...

Insight from Molecular, Pathological, and Immunohistochemical Studies on Cellular and Humoral Mechanisms Responsible for Vaccine-Induced Protection of Rainbow Trout against Yersinia ruckeri

“…It is believed that in murine yersiniosis, protective-cell-associated defense mechanisms comprise macrophages/NK cells, which become activated via T helper cells (CD4) producing significant amounts of IFN-␥ (40,41). In rainbow trout lymphoid organs, we found high expression of both IFN-␥ and TNF-␣ genes in nonimmunized Y. ruckeri-infected fish and moderate regulation in vaccinated fish, especially on day 3 p.i.…”

Immunomodulation byYersinia enterocolitica: comparison of live and heat-killed bacteria

“…Infection with IP383 is able to induce macrophage activation linked to an inhibition of the capacity of splenocytes to proliferate in response to both B‐cell and T‐cell mitogens [9]. To assess if live Y. enterocolitica were necessary for the observed suppression of ex vivo lymphoproliferation, the responses of spleen cells from 10‐day‐infected mice, HKY‐treated mice and untreated controls were compared.…”

“…We have previously demonstrated that low‐virulence Y. enterocolitica strains possess immunomodulatory properties [7–9]. Interestingly, experimental infection with IP383, a pYV‐bearing strain belonging to the low‐virulence serotype O9, confers on BALB/c mice significant resistance levels against transplantation of the syngeneic lymphoma LSTRA or challenge with a lethal dose of the intracellular pathogen Listeria monocytogenes [8,9].…”

“…However, the bacterial fractions responsible for the immunomodulating effects are unknown. Observations regarding immunomodulation by low‐virulence serotypes have been always performed with experimentally infected mice [7–9], and it is not known whether killed yersiniae retain the capacity to cause non‐specific modifications on the immunity mechanisms. In the present work, we compared the ability of live and heat‐killed organisms from strain IP383 to modify the proliferation of mouse lymphocytes in response to B‐cell and T‐cell mitogens.…”

The Functions of Effector Proteins in Yersinia Virulence

“…Mesenteric lymph nodes become amplified and the focal area of necrosis exhibits leukocytes infiltration Bliska, 2005, Ruckdeschel et al, 1996). Studies of the intestine of Y. enterocolitica O9 infected BALB/c mice indicates that the infected mice exhibit splenomegaly, and development of CD3 + total T cells, CD4 + Th cells, CD8 + Tc cells, and CD11b + phagocytic cells (Ruiz-Bravo et al, 2001). The infection also causes the impaired response and proliferation of normal splenocytes against the mitogens, which in turn promotes the inhibition of lymphocyte responding to mitogens.…”