Human gamma delta T-cell recognition of Yersinia enterocolitica

The cellular immune response after an experimental oral infection with Yersinia enterocolitica (serotype 0:3, biotype 4, harbouring the virulence plasmid-p YV) was studied in pigs. A maximal stimulation of the T cell population in the thymus, spleen and peripheral blood was stated on the 15th day post infection (p.i.) by the rosette forming cell (RFC) test. The hemolysins (produced by B cells and detected by the plaque forming cell test-PFC) were significantly increased on the 15th day p.i. among the thymus and spleen lymphocytes and on the 25th day p.i. among the blood lymphocytes. Blood and thymus lymphocytes were activated faster by the infectious agent in comparison to the spleen cells. The electronmicroscopic studies revealed an intracellular presence of the bacteria in alveolar macrophages (aMa) and peritoneal macrophages (pMa) as well as in Peyer's patches and tonsils as early as on the 4th day p.i. Extracellularly located bacteria were observed, too. The results have shown that inspite of the activation of T and B cell immune response, this infectious agent persisted in the porcine organism.     

Atopic sensitization during the first year of life in relation to long chain polyunsaturated fatty acid levels in human milk

The influence of low (0.39-1.1%), medium (4.25%) and high (7.1-32.5%) fat levels in fish on radiation inactivation of four food-borne pathogens was investigated. Cells of Listeria monocytogenes 036, Yersinia enterocolitica F5692, Bacillus cereus and Salmonella typhimurium at logarithmic phase were inoculated in 10% fish homogenates and subjected to gamma irradiation at ice temperature (0-1 degree C) with doses ranging from 0.05 to 0.8 kGy. The radiation survival curves of L. monocytogenes and B. cereus were characterized by shoulders, while a tailing effect was depicted by cells of Y. enterocolitica and B. cereus. The D10 values in kGy calculated on the exponential part of the curve ranged from 0.2 to 0.3, 0.15 to 0.25, 0.1 to 0.15 and 0.09 to 0.1 for L. monocytogenes 036, B. cereus, Salm. typhimurium and Y. enterocolitica F5692, respectively. This order (D10) of radiation resistance of each organism was not affected by the fat content of the fish. Inoculated pack studies carried out separately with each pathogen in fatty (Indian sardine, 7.1%) and lean (Golden anchovy, 0.39%) fish showed no difference in their survival after exposure to 1 kGy and 3 kGy doses, which corroborated the above observation. The practical significance of these results in the application of the technology is discussed.     

High prevalence of pancreatic disease in chronic renal failure

Lymphocytes from the cervical lymph nodes of guinea pigs were incubated in medium 199 in the presence of cortizol in a concentration of 20 and 100 microng% for 24 hours. A determination was made of the lymphocyte survival and cortizol metabolism by them, and also (cytophotometrically) the nucleic acid content. In the intact and the sesitized guinea pigs progesterone in a concentration of 10-5 inhibited both the lytic action of coritizol and its metabolism There was observed a marked reduction of cortizol meta bolism by the lymphocytes from the 6th day after the sensitization, which was restored only by the 90th day. The cortizol-resistant lymphocyte population increased on the 17th--30th day. In a concentration of 100 microng% cortizol reduced the nucleic acid content in the lymphocytes of both the intact guinea pigs and sensitized ones on the 17th--30th day, when the cortizol-resistant population increased.     

Intranasal immunization with Yersinia enterocolitica O:8 cellular extract protects against local challenge infection

Yersinia enterocolitica is enteropathogenic for humans and rodents. Immune protection from oral and respiratory pathogens may be most effectively elicited following intranasal (i.n.) vaccination. An experimental murine intranasal challenge model was used to evaluate the immunogenicity of a Y. enterocolitica O:8 cellular extract (CE) in mucosa. This antigenic preparation has demonstrated to induce protection by subcutaneous immunization. Mice were immunized intranasally with two doses of CE. Immunized and nonimmunized animals were challenged with 5 x 10(6) colony-forming units (CFU) by nasal infection. Antibodies in serum and bronchoalveolar lavage (b.a.l.) fluid were assessed before and 48 hr after challenge. The CFU were determined by analysis of lung homogenate samples. The CE immunization induced significant b.a.l.-specific IgA and IgG, and serum-specific IgG, IgA and IgM. Histopathological studies 24 and 48 hr postchallenge demonstrated that immunization protected against progressive lesions resulting from Y. enterocolitica invasion of the pulmonary mucosa. The CFU in the lungs showed that CE immunization led to significant clearance as compared to the bacterial level in nonimmunized controls. From the results obtained, it can be concluded that CE can induce local and systemic immunity and protect against nasal infection.     

Protein deficiency induces alterations in the distribution of T-cell subsets in experimental pulmonary tuberculosis

Previous research has suggested that dietary protein deficiency alters resistance to experimental pulmonary tuberculosis, in part, by affecting the distribution and trafficking of antigen-reactive T cells. In this study, guinea pigs were maintained on either a protein-deficient (10% ovalbumin) or control (30% ovalbumin) diet and infected 4 to 6 weeks later with a low dose of virulent Mycobacterium tuberculosis H37Rv by the respiratory route. Monoclonal antibodies directed against the CD4 or CD8 markers on guinea pig lymphocytes were used in a flow cytofluorometric assay to determine the proportion of each subset in the peripheral circulation, spleen, and bronchotracheal lymph nodes at 4 weeks after infection. In uninfected guinea pigs, only the spleen exhibited an effect of diet on T-cell distribution, with small but consistent reductions in the proportions of both CD4 and CD8 T lymphocytes. However, following infection, protein deficiency exerted a profound effect on T-cell distribution. Malnourished, tuberculous guinea pigs harbored only 20 and 60% of the T cells (as a proportion of total lymphoid cells) found in the spleen and blood, respectively, of their well-nourished counterparts. Normal relative proportions of CD4 and CD8 cells were observed, however. In striking contrast, the bronchotracheal lymph nodes of protein-deprived guinea pigs with tuberculosis contained more than twice the numbers of T cells of control guinea pigs, and the normal CD4-to-CD8 ratio was reversed. Peripheral T-cell function, as measured by the delayed hypersensitivity skin test to tuberculin, and antigen-induced lymphoproliferation in vitro were markedly suppressed in protein-malnourished animals. Conversely, purified protein derivative-induced (but not concanavalin A-induced) proliferation was significantly enhanced in cultures of lymph node cells from protein-deprived tuberculous animals. Taken together, these results suggest that immunological abnormalities and loss of antimycobacterial resistance in the lungs of protein-deficient guinea pigs may be explained, in part, by sequestration of antigen-reactive T cells in the lymph nodes draining the site of infection.     

Estimation of the mutagenic potential of the trematode Opisthorchis felineus in experimentally infected guinea pigs

We studied the mutagenic potential of the trematode Opisthorchis felineus in experimentally infected guinea pigs by chromosome analysis. The investigation was conducted on 30 treated (experimentally infected) and 20 normal (uninfected) guinea pigs (Cavia porcellus). A sample of living metacercariae of O. felineus was obtained from the muscle of naturally infected crucian carp captured in the Tom River, and 1 ml suspension containing approximately 50 metacercariae in 0.9% NaCl solution was individually given p.o. to guinea pigs that were used as treated specimens, whereas normal guinea pigs from the same stock were given 1 ml 0.9% NaCl solution per individual to serve as controls. The treated and control animals were killed by CO2 asphyxiation and decapitation at 7, 15, 30, 45, and 120 days after contamination. The smears of bone marrow cells for chromosome analysis were prepared by a standard method. Statistical analysis of the data was done using Student's t-test. We found that experimental infection of guinea pigs with O. felineus induced significantly high frequencies of hypoploid cells and, at the 120th day p.i., led to a considerable incidence of chromatid breaks and polyploidy in bone marrow cells.     

Comparison of amikacin dosing regimens in neutropenic guinea pigs with Escherichia coli infection

OBJECTIVE: To derive pharmacokinetic data for 3 amikacin dosing regimens in guinea pigs and to determine whether the antibacterial activity of 15 mg/kg of body weight given twice daily is equivalent to administering the drug more frequently. ANIMALS: 10 guinea pigs in pharmacokinetic trials, and 10 guinea pigs in pretreatment, control, and amikacin treatment groups. PROCEDURE: Amikacin pharmacokinetic data were determined in guinea pigs after single i.m. administration of 3.75, 7.5 and 15 mg/kg. Guinea pigs had been made neutropenic by treatment with cyclophosphamide. All guinea pigs were inoculated with 2.8 x 10(8) colony-forming units (CFU) of Escherichia coli in the thigh muscle, then were allotted to 5 groups: pretreatment (euthanized 4 hours after inoculation), control, and 3 amikacin treatment groups (3.75 mg/kg, q 3 h; 7.5 mg/kg, q 6 h; and 15 mg/kg, q 12 h). Amikacin administration was begun 4 hours after E coli inoculation and was continued for 72 hours. Numbers of E coli CFU in infected thigh muscle were determined for each guinea pig. RESULTS: Difference in survival between control and the amikacin-treated groups was significant. The E coli infection concentration (log10 CFU) increased significantly in the control, compared with the pretreatment, group. Infection concentration decreased significantly in all treatment groups, compared with the pretreatment group. There was no significant difference in bacterial killing among the 3 treatment groups. CONCLUSION: Amikacin had a significant effect on survival of neutropenic guinea pigs with E coli infection. Antibacterial activity did not differ among 3 doses of amikacin administered at different intervals. CLINICAL RELEVANCE: Aminoglycoside dosing regimen with high peak concentration and long drug-free interval is as efficacious as divided dose regimens.     

Lymphocyte apoptosis during classical swine fever: implication of activation-induced cell death

Infection of pigs with classical swine fever virus (CSFV), a member of the Flaviviridae family, causes a severe leukopenia, particularly notable with the lymphocytes. The goal of this study was to analyze mechanisms behind this CSFV-induced lymphopenia. To this end, the kinetics of leukocyte depletion, the appearance of apoptotic cells, and virus infection of leukocytes after infection of pigs with the virulent CSFV strain Brescia were analyzed. Depletion of B and T lymphocytes was noted as early as 1 day postinfection (p.i.). Circulating viable lymphocytes with reduced mitochondrial transmembrane potential--a particular early marker for apoptosis--were also detectable as early as 1 day p.i. When isolated peripheral blood mononuclear cells were cultured for 6 h, significantly more sub-G1 cells with reduced DNA content were detected among the lymphocytes from CSFV-infected animals, again as early as 1 to 3 days p.i. The first time virus was first found in the plasma, as well as infection of leukocytes, was 3 days p.i. However, throughout the observation time of 1 week, <3% of the circulating leukocytes and no lymphocytes contained virus or viral antigen. Further analysis of the T lymphocytes from infected animals demonstrated an increase in CD49d, major histocompatibility complex class II, and Fas expression. An increased susceptibility to apoptosis in vitro was also observed, particularly after addition of concanavalin A as well as apoptosis-inducing anti-Fas antibody to the cultures. Taken together, these results imply that activation-induced programmed cell death was the mechanism behind lymphopenia during classical swine fever.     

Correlation between production of listeriolysin O by variants of Listeria monocytogenes and their virulence for rabbits

L. monocytogenes serovar 1/2a NCTC 7973 was passaged through rabbits and the severity of infection at each passage was determined by counting viable bacteria from infested organs and recording the time of death. A comparative evaluation of the levels of hemolysin produced in vitro by the original and six variant cultures (V1-V6) was done by determination of hemolytic units (CHU). While virulence of the cultures enhanced at each passage (2.2 x 10(9) CFU/g of the spleen for V6 as compared to 5.0 x 10(6) CFU/g spleen for the parent culture), the CHU decreased considerably, 3 CHU for the V6 as compared to 40 CHU for the parent strain. The results suggest that the level of in vitro production of listeriolysin may not parallel the pathogenicity of L. monocytogenes for rabbits.     

Mycobacterium avium complex infection in mice: lack of exacerbation after LP-BM5 murine leukemia virus infection

The murine leukemia virus LP-BM5 has been used to reproduce the model of murine AIDS in order to evaluate the course of infection with the MO-1 strain of Mycobacterium avium complex (MAC). LP-BM5 was inoculated in C57BL/6 mice by intravenous (i.v.) injection either 8 weeks before an i.v. challenge with 10(3) or 10(6) CFU of MAC (coinfection 1) or 10 days after an i.v. challenge with 10(3) CFU of MAC (coinfection 2). During coinfection 2 experiments, the phenotypic alterations in blood lymphocyte subsets were analyzed. During coinfection 1, LP-BM5 infection tended to decrease the mycobacterial growth, with the difference reaching statistical significance for the lower inoculum (10(3) CFU of MAC) (P<0.001). During coinfection 2, LP-BM5 did not exacerbate MAC infection except in the spleen, at day 90 after LP-BM5 challenge (P<0.001). LP-BM5 infection and the LP-BM5-MAC coinfection increased the numbers of activated CD4+ lymphocytes (CD4+ Ly6AE+) (P<0.001), activated CD8+ lymphocytes (CD8+ Ly6AE+) (P<0.001), and activated B lymphocytes (Ly5+ Ly6AE+) (P<0.001). This activation of T lymphocytes could explain the lack of exacerbation of MAC infection and even the trend to a lower level of MAC infection. Thus, this model of retroviral infection of mice does not seem to be a reliable model of immunodepression for the study of MAC infection and its treatments.     

Isolation and biological characterization of Legionella pneumophila mutants resistant to aminoglycoside antibotics and their protective action]

Preliminary estimation of virulence in some antibiotic resistant mutants of Legionella pneumophila, Philadelphia 1 in various models of infection revealed its decrease in the mutants resistant to azlocillin, cefotaxime, fluoroquinolone LIB-80, neamine and streptomycin. Detailed investigation of the neamine resistant mutants showed that in relation to streptomycin susceptibility such mutants could be divided into 3 classes: susceptible to streptomycin, resistant to high concentrations of streptomycin and resistant to moderate concentrations of streptomycin. Part of mutants Nea(r)Strr and Nea(r)Strr500 and all mutants Nea(r)Strr100 proved to be less virulent with respect to guinea pigs and chick embryos. The study of the spectinomycin resistant mutants of Legionella spp. did not reveal any changes in the virulence which made it possible to suggest that the influence of the mutations in the ribosomal protein genes determining resistance to streptomycin and neamine on virulence of L. pneumophila was based on the interdependence of the mutant effect on the suppression and the influence on the virulence detected by us in S. flexneri, Y. pseudotuberculosis, L. monocytogenes and F. tularensis. The Legionella mutants Nea(r)Strr100 were characterized by significant protective activity and protected immunized guinea pigs when tested in a model of their aerogenic infection.     

Incidence and coincidence of Listeria spp., motile aeromonads and Yersinia enterocolitica on ready-to-eat fleshfoods

A survey for the presence of Listeria spp., Yersinia enterocolitica and motile aeromonads in 203 samples of ready-to-eat fleshfoods purchased from retail outlets was conducted. Overall, 39.4%, 3.4% and 23.2% of samples were positive for the presence of Listeria spp., Y. enterocolitica and motile aeromonads respectively. Two factors have been identified as contributing to contamination of fleshfoods by these cold-tolerant bacteria. These are (i) the method of sale; delicatessen-bought foods were notably more contaminated than similar products bought pre-packaged, and (ii) the method of preservation. For motile aeromonads fermented foods were the least contaminated, whereas smoked and cooked products had similar incidence rates. For L. monocytogenes, significantly more (41.9%) smoked products were contaminated than fleshfoods preserved by other methods. For Y. enterocolitica, only cooked products were contaminated. In the case of cooked fleshfoods it must be assumed that most contamination occurs post-cooking and that contamination rates are increased by poor food handling procedures. Of the three possible pairwise combinations of these organisms, the coincidence of Y. enterocolitica and motile aeromonads was the only one that differed significantly from a random distribution (P less than 0.001), indicating that fleshfoods contaminated with Y. enterocolitica are probably also contaminated by motile aeromonads.     

Lymphocyte function in experimental african trypanosomiasis: mitogenic effects of trypanosome extracts in vitro

Extracts of Trypanosoma brucei and Trypanosoma congolense were incubated in vitro with nonimmune lymphocytes of mice, rats, guinea pigs, and rabbits in order to test for mitogenic effects or for other characteristics of polyclonal B lymphocyte activators. Trypanosome extracts (TE) were not mitogenic for spleen cells of mice, rats, and guinea pigs in vitro, nor did the parasite extracts alter the mitogenic responses of lymphocytes from these animals to known B- and T-cell mitogens. TE also failed to induce polyclonal antibody synthesis in mouse spleen cell cultures in an in vitro antibody response system, in contrast to the effects of bacterial lipopolysaccharide, a known polyclonal B cell activator. Rabbit spleen cell and peripheral blood lymphocyte cultures, however, were stimulated by TE to undergo blastogenesis in vitro. Incubation of rabbit lymphocytes with phytohemagglutinin (PHA) and TE or anti-rabbit immunoglobulin serum and TE revealed an additive effect only in terms of the TE-plus-PHA culture responses; these findings suggest that a non-PHA responsive lymphocyte population, possibly B lymphocytes, is stimulated by TE in rabbits. The relationship of trypanosome-induced lymphocyte mitogenic stimulation to other immunological dysfunctions occurring in chronic African trypanosomiasis is discussed.     

Immunoblot studies in the differential diagnosis of porcine brucellosis: an immunodominant 62 kDa protein is related to the mycobacterial 65 kDa heat shock protein (HSP-65)

Smooth Brucella spp. share certain lipopolysaccharide antigens with other bacteria, resulting in serological cross-reactions which can prevent the definitive diagnosis of brucellosis. To identify other antigens with serodiagnostic potential, immunoblot studies following sodium dodecyl sulphate-polyacrylamide gel electrophoresis were carried out. Sera from pigs experimentally infected with Brucella suis and naturally infected feral pigs, sera from pigs from a farm with a known history of Yersinia enterocolitica 0:9 infection, Brucella Complement Fixation Test (CFT) reactor pigs (aetiology unknown) and pigs from consistently Brucella CFT negative farms were examined. Although B. suis infected pigs recognized a total of nine B. melitensis antigens, individual pigs rarely recognized more than three antigens in the range. A 62 kDa antigen was recognized by the majority (73%) of the Brucella infected pigs, but only by 10 to 23% of pigs from the other groups. This antigen was shown to be the Brucella homologue of the ubiquitous 65 kDa heat shock protein (HSP-65) family by immunoblot studies with 14 monoclonal antibodies to the Mycobacterium leprae HSP-65. Only four of these monoclones (Y1.2, ML-30, D7C and IIIC8) identified the B. melitensis 62 kDa protein suggesting that unshared, potentially Brucella specific, regions exist. Sera from Y. enterocolitica 0:9 infected pigs, CFT reactor pigs (aetiology unknown), CFT negative pigs and hyperimmune pig serum raised to Y. enterocolitica 0:9 also recognized B. melitensis antigens, most notably a 17 kDa protein. This antigen appears to be a common cross-reactive protein.     

Flow cytometric analysis of T4:T8 splenic cell during dengue virus infection of mice

The present study was undertaken to investigate the effect of dengue type 2 virus (DV) and DV-induced cytokines (CF and CF2) on T lymphocyte subpopulations of spleen by flow cytometry. Following DV-ic inoculation in mice the percent number of CD4+ and CD8+ lymphocytes in the spleen was reduced, the peak reduction in both was observed on the 6th day post-inoculation (p.i.). Intravenous inoculation of CF or CF2 in mice also decreased the percent number of CD4+ as well as CD8+ T lymphocytes subpopulation in the spleen, the maximum reduction being observed at 1 and 2 hr, respectively. The reduction in T lymphocyte subpopulation by CF and CF2 was found to be dose dependent. Thus, the alterations of T lymphocyte subpopulations during DV infection are mediated via cytokines.     

Temperature effects on Legionella pneumophila killing by and multiplication in phagocytes of guinea pigs

We examined the effects of temperature on the interaction between Legionella pneumophila and phagocytes of guinea pigs. The body temperatures of guinea pigs infected with a sublethal dose (1.2 x 10(4) CFU) or a lethal dose (1.0 x 10(5) CFU) of L. pneumophila elevated from 38.4 +/- 0.15 C to 40.2 +/- 0.42 C or 40.3 +/- 0.62 C, respectively. The intracellular bacterial killing by and bacterial proliferation in the phagocytes were examined at 33, 37, 40, and 42 C, using in vitro culture systems of peritoneal macrophages or polymorphonuclear leukocytes (PMN) of guinea pigs. In all the macrophages incubated at different temperatures, significant intracellular bacterial killings were observed at 4 hr after in vitro phagocytosis. After 24 hr of incubation, there was about a 100-fold increase of CFU and the number reached a maximum after 48 hr of incubation in the macrophages incubated at 42 C as well as 37 and 40 C, suggesting that macrophages support the intracellular bacterial growth in hyperthermia. In the PMN, L. pneumophila CFU 4 hr or 12 hr after the infection were significantly lower at 42 C than those at 37 C (P < 0.05), indicating that the bactericidal capacity of PMN was enhanced at 42 C compared to 37 C. However, in all the PMN incubated at different temperatures, there were about 10-fold increases of CFU 24 hr after the infection, suggesting that PMN as well as macrophages support intracellular bacterial growth in hyperthermia. The extracellular bacterial growth was examined at 33, 37, 40, and 42 C in buffered yeast extract (BYE) broth or RPMI 1640 medium containing 50% guinea pig serum as a permissive or non-permissive liquid medium for the bacterial growth, respectively. Inhibition of bacterial growth in BYE broth at 42 C, and a decrease of CFU in RPMI 1640 medium containing 50% guinea pig serum at 42 C were observed. In conclusion, hyperthermia may be beneficial by restricting extracellular bacterial survival, but it exerts no beneficial effect on the restriction of intracellular bacterial growth in phagocytes, though PMN showed enhanced initial killing at 42 C. These results suggest that fever, or hyperthermia itself, may not largely contribute as a nonspecific host defense early in the course of legionellosis.     

Penetration of M cells and destruction of Peyer's patches by Yersinia enterocolitica: an ultrastructural and histological study

Yersinia enterocolitica is enteropathogenic for man and rodents. Previous studies provided evidence that Y. enterocolitica invades the lymphoid follicles of the Peyer's patches (PP) of the small intestine. In this study Y. enterocolitica-induced tissue alterations of the follicle-associated epithelium (FAE) and the underlying PP tissue were analysed by scanning (SEM) and transmission electron microscopy (TEM) as well as by conventional histological examination. For this purpose, an experimental mouse infection model including orogastric infections as well as ileal loop experiments were used. A rapid and selective colonisation of the FAE after orogastric yersinia infection was observed by SEM. TEM studies confirmed that Y. enterocolitica adhered closely to the FAE including M cells and enterocytes. Histological studies and TEM revealed that Y. enterocolitica selectively invaded the PP via M cells but not via other cells of the FAE. One day after Y. enterocolitica infection the FAE was altered and small micro-abscesses comprising yersiniae expressing the major outer-membrane protein YadA were observed immediately beneath the FAE. Adjacent villi were dilated from lymphangiectasis and transmigrating polymorphonuclear leucocytes (PMNL) were found within the epithelium. At 5-7 days after infection the FAE and parts of PP were destroyed. Profound alterations of the cyto-architecture of the PP were due to the enormous recruitment of PMNL. By day 5 after infection, abscesses were found in the mesenteric lymph nodes. However, TEM studies revealed evidence that Y. enterocolitica may disseminate from the PP not only via the lymphatics but also by invasion of blood vessels. Taken together, the results of this study demonstrate that the FAE is the primary site of host-pathogen interaction in Y. enterocolitica infection and that this pathogen penetrates M cells and subsequently induces destruction of the PP.     

Experimental infection of axenic mice by "Yersinia enterocolitica" (author's transl)

Although most of Yersinia enterocolitica strains isolated from man have no pathogenicity for laboratory animals, it has been demonstrated that some strains are pathogenic for conventional mice and that most of the strains are probably pathogenic for Nude mice. The authors report the results of the infection of germ-free mice with a strain of Y. enterocolitica which is non pathogenic for holoxenic mice. It appears that C3H/He mice are sensitive to the infection by gavage or aerogenic and peritoneal routes. They all die within 8 to 12 days after injection of an inoculum of 5.10(5) viable cells. Germ-free NCS mice were also sensitive to the oral and aerogenic infection but not to the peritoneal infection; the difference between C3H/He and NCS sensitivity to this way of infection could be explained by a higher bactericidal activity of the peritoneal phagocytes of the latter. The C3H/He and NCS holoxenic control mice infected with the same inoculum of the same strain, did not show any symptoms and all attempts to isolate Y. enterocolitica failed three months after the challenge. Germ-free mice killed by the infection showed histopathological findings, i.e. abscesses involving intestinal wall. liver and spleen; they were similar to those described in experiments with pathogenic strains for conventional mice (holoxenic) and to those observed in infection of athymic Nude mice with strains non pathogenic for conventional mice. This infectious disease model is discussed in regards to the natural human infection.     

A nonamer peptide derived from Listeria monocytogenes metalloprotease is presented to cytolytic T lymphocytes

Listeria monocytogenes is an intracellular bacterium that secretes proteins into the cytosol of infected macrophages. Major histocompatibility complex (MHC) class I molecules bind peptides that are generated by the degradation of bacterial proteins and present them to cytolytic T lymphocytes (CTL). In this study we have investigated CTL responses in L. monocytogenes-immunized mice to peptides that (i) derive from the L. monocytogenes proteins phosphatidylinositol-specific phospholipase C, lecithinase (most active on phosphatidylcholine), metalloprotease (Mpl), PrfA, and the ORF-A product and (ii) conform to the binding motif of the H2-Kd MHC class I molecule. We identified a nonamer peptide, Mpl 84-92, that is presented to L. monocytogenes-specific CTL by H2-Kd MHC class I molecules. Unlike other motif-conforming peptides derived from the secreted Mpl of L. monocytogenes, Mpl 84-92 is bound with high affinity by H2-Kd. Mpl 84-92 is the fourth L. monocytogenes-derived peptide found to be presented to CTL by the H2-Kd molecule during infection and demonstrates the importance of high-affinity interactions between antigenic peptides and MHC class I molecules for CTL priming.     

Impaired sensorineural function after allergen-induced mediator release

We tested the hypothesis that allergen-induced mediator release augments the magnitude of isocapnic dry gas hyperpnea-induced bronchoconstriction in sensitized guinea pigs. Male Hartley guinea pigs were sensitized by spontaneous inhalation of ovalbumin (OA) aerosol on days 0 and 7 of the study. On day 14, sensitized animals again breathed OA aerosol and were prospectively divided into a group that exhibited labored breathing (LB), presumably reflecting OA-induced inflammatory mediator release, and a group that did not exhibit LB at this time. Control guinea pigs breathed saline aerosol on days 0, 7, and 14. Bronchoalveolar lavage on day 17 disclosed relative eosinophilia in OA+LB, but not in OA-LB, animals. On day 17, the bronchoconstrictor responses to increasing intravenous (i.v.) doses of acetylcholine (ACh), substance P (SP), neurokinin A (NKA), and capsaicin, as well as dry gas hyperpnea, were measured in vivo in animals from each group. Control and OA-LB guinea pigs exhibited similar responses, but OA+LB animals demonstrated augmented bronchoconstriction induced by i.v. administration of ACh, SP, or NKA. However, despite their augmented responsiveness to these exogenous constrictor agonists, OA+LB animals displayed no greater bronchoconstriction after dry gas hyperpnea or i.v. capsaicin administration. It is known that both dry gas hyperpnea and i.v. capsaicin cause bronchoconstriction in guinea pigs by releasing endogenous tachykinins from airway sensory C-fibers. Thus, our results suggest that allergen-induced mediator release impairs endogenous tachykinin release from airway sensory C-fibers in guinea pigs.