Expeditious recruitment of circulating memory CD8 T cells to the liver facilitates control of malaria

Circulating memory CD8 T cell trafficking and protective capacity during liver-stage malaria infection remains undefined. We find that effector memory CD8 T cells (Tem) infiltrate the liver within 6 hours after malarial or bacterial infections and mediate pathogen clearance. Tem recruitment coincides with rapid transcriptional upregulation of inflammatory genes in Plasmodium-infected livers. Recruitment requires CD8 T cell-intrinsic LFA-1 expression and the presence of liver phagocytes. Rapid Tem liver infiltration is distinct from recruitment to other non-lymphoid tissues in that it occurs both in the absence of liver tissue resident memory "sensing-and-alarm" function and ∼42 hours earlier than in lung infection by influenza virus. These data demonstrate relevance for Tem in protection against malaria and provide generalizable mechanistic insights germane to control of liver infections.

Characteristics and Outcomes of Neonates With Blood Stream Infection Due to Listeria monocytogenes

BACKGROUND

Infection due to Listeria monocytogenes (LM) is rare in neonates; thus, its clinical presentation and outcomes are not commonly reported, especially in low- and middle-income countries. In 2017, South Africa had an outbreak due to LM.

OBJECTIVE

To determine demographic characteristics, clinical and laboratory findings and outcomes of all neonates infected with LM during the outbreak period.

METHODS

This is a retrospective analytic study. Clinical and laboratory records of neonates admitted at Chris Hani Baragwanath Academic Hospital from January 2017 to May 2018 with positive blood and cerebrospinal fluid culture with LM were reviewed for demographic characteristics, clinical presentation, ancillary laboratory test results and outcomes at hospital discharge.

RESULTS

There were 42 neonates with positive cultures due to LM. Thirty-four (81%) were born preterm. Mode of delivery was vaginal in 78.6% and 31.0% were HIV exposed. All patients presented within the first 6 days of life as an early-onset disease. Common clinical presentation was respiratory depression (52.4%) and respiratory distress (38.1%) with 69% requiring invasive or noninvasive respiratory support. Common abnormal laboratory findings were high C-reactive protein (77.1%) followed by leukopenia (23.8%). Fourteen patients (40%) had features of meningitis based on blood and cerebrospinal fluid findings (4 culture proven). There were 11 deaths at hospital discharge, giving a mortality rate of 26.2%.

CONCLUSIONS

The majority of neonates infected with LM were born preterm, raising the possibility that LM itself may have been responsible for preterm labor. All presented in the first 6 days of life and most presented with respiratory distress or depression. A high proportion had meningitis, and there was a high-mortality overall.

Intrinsic role of FoxO3a in the development of CD8+ T cell memory

CD8(+) T cells undergo rapid expansion during infection with intracellular pathogens, which is followed by swift and massive culling of primed CD8(+) T cells. The mechanisms that govern the massive contraction and maintenance of primed CD8(+) T cells are not clear. We show in this study that the transcription factor, FoxO3a, does not influence Ag presentation and the consequent expansion of CD8(+) T cell response during Listeria monocytogenes infection, but plays a key role in the maintenance of memory CD8(+) T cells. The effector function of primed CD8(+) T cells as revealed by cytokine secretion and CD107a degranulation was not influenced by inactivation of FoxO3a. Interestingly, FoxO3a-deficient CD8(+) T cells displayed reduced expression of proapoptotic molecules BIM and PUMA during the various phases of response, and underwent reduced apoptosis in comparison with wild-type cells. A higher number of memory precursor effector cells and memory subsets was detectable in FoxO3a-deficient mice compared with wild-type mice. Furthermore, FoxO3a-deficient memory CD8(+) T cells upon transfer into normal or RAG1-deficient mice displayed enhanced survival. These results suggest that FoxO3a acts in a cell-intrinsic manner to regulate the survival of primed CD8(+) T cells.

Interplay between CD8α+ dendritic cells and monocytes in response to Listeria monocytogenes infection attenuates T cell responses

During the course of a microbial infection, different antigen presenting cells (APCs) are exposed and contribute to the ensuing immune response. CD8α(+) dendritic cells (DCs) are an important coordinator of early immune responses to the intracellular bacteria Listeria monocytogenes (Lm) and are crucial for CD8(+) T cell immunity. In this study, we examine the contribution of different primary APCs to inducing immune responses against Lm. We find that CD8α(+) DCs are the most susceptible to infection while plasmacytoid DCs are not infected. Moreover, CD8α(+) DCs are the only DC subset capable of priming an immune response to Lm in vitro and are also the only APC studied that do so when transferred into β2 microglobulin deficient mice which lack endogenous cross-presentation. Upon infection, CD11b(+) DCs primarily secrete low levels of TNFα while CD8α(+) DCs secrete IL-12 p70. Infected monocytes secrete high levels of TNFα and IL-12p70, cytokines associated with activated inflammatory macrophages. Furthermore, co-culture of infected CD8α(+) DCs and CD11b+ DCs with monocytes enhances production of IL-12 p70 and TNFα. However, the presence of monocytes in DC/T cell co-cultures attenuates T cell priming against Lm-derived antigens in vitro and in vivo. This suppressive activity of spleen-derived monocytes is mediated in part by both TNFα and inducible nitric oxide synthase (iNOS). Thus these monocytes enhance IL-12 production to Lm infection, but concurrently abrogate DC-mediated T cell priming.

[Listeria monocytogenes in human infections]

The Listeria genus is distinguished into six species from which just one--Listeria monocytogenes is pathogenic for humans. The main route of acquisition of Listeria is through the ingestion of contaminated food products. An important element of the L. monocytogenes pathogenesis infection is affiliation with high-risk group of immunocompromised patients, infants or pregnant women, who infected by this microorganism can lead to miscarriage. Listeriosis can appear in the form of sepsis, infection of the nervous system or local abscesses. Another form of listeriosis is gastrointestinal tract infection--noticed in case of food poisoning outbreak.

[Investigation of Listeria monocytogenes serotype O antibodies in maternal and cord sera and the evaluation of risk factors for listeriosis in pregnant women]

Listeria monocytogenes may lead to intrauterine infections which can be treated if diagnosed promptly. However, there is not a rapid routine screening test with high specificity and sensitivity for the diagnosis of listeriosis during pregnancy. We investigated the presence of different L. monocytogenes O antibodies for diagnosis of listeriosis in 275 paired maternal-cord sera using the agglutination test, and aimed to evaluate the correlation between poor pregnancy outcomes, level of L. monocytogenes serotype O antibodies and risk factors for listeriosis. Maternal-cord bloods were collected from a total of 275 pregnant women (age range 16-38 years) between April-August 2002 from a State Hospital in Ankara. A total of 550 sera were tested against antigens with the O formulation of serotypes 1/2c, 3b, 4ab, 4c, 4d by tube agglutination method and titers > or = 1/320 were considered as positive. Sixtynine patients with the history of poor pregnancy outcomes were in group I, while 206 patients with no obstetric pathology in previous pregnancies were in group II. L. monocytogenes antibodies to one or more serotypes were detected in 21.5% (59/275) of the patients, the rate being 20.3% in group I and 21.8% in group II. No statistically significant difference was detected between the two study groups (p > 0.05), indicating that this test was not an appropriate marker for the diagnosis of listeriosis during pregnancy. The total rate of positive results in cord sera was 0.7% (2/275) and the positive two sera were from samples in group II. The follow-up of the newborns, including the two cord blood positive ones, revealed no fetomaternal infection. The most frequently detected serotypes were 4ab (40%) and 1/2c (37%). Risk factors such as non-specific febrile illness during pregnancy (p < 0.001), consumption of ready-made food (p = 0.008), consumption of raw milk and milk products (p < 0.001) were found to be related to the presence of > or = 1/320 titers of L. monocytogenes antibodies. The major limiting factor in this study was the inability to obtain second serum samples from the mothers and newborns following delivery, to confirm the diagnosis by seroconversion. These results emphasize the need for the development of rapid, simple and reliable tests, alternative to culture methods, for the early and proper diagnosis of Listeria infections during pregnancy.

The aryl hydrocarbon receptor is required for optimal resistance to Listeria monocytogenes infection in mice

The aryl hydrocarbon receptor (AhR) is part of a powerful signaling system that is triggered by xenobiotic agents such as polychlorinated hydrocarbons and polycyclic aromatic hydrocarbons. Although activation of the AhR by 2,3,7,8-tetrachlorodibenzo-p-dioxin or certain polycyclic aromatic hydrocarbons can lead to immunosuppression, there is also increasing evidence that the AhR regulates certain normal developmental processes. In this study, we asked whether the AhR plays a role in host resistance using murine listeriosis as an experimental system. Our data clearly demonstrate that AhR null C57BL/6J mice (AhR(-/-)) are more susceptible to listeriosis than AhR heterozygous (AhR(+/-)) littermates when inoculated i.v. with log-phase Listeria monocytogenes. AhR(-/-) mice exhibited greater numbers of CFU of L. monocytogenes in the spleen and liver, and greater histopathological changes in the liver than AhR(+/-) mice. Serum levels of IL-6, MCP-1, IFN-gamma, and TNF-alpha were comparable between L. monocytogenes-infected AhR(-/-) and AhR(+/-) mice. Increased levels of IL-12 and IL-10 were observed in L. monocytogenes-infected AhR(-/-) mice. No significant difference was found between AhR(+/-) and AhR(-/-) macrophages ex vivo with regard to their ability to ingest and inhibit intracellular growth of L. monocytogenes. Intracellular cytokine staining of CD4(+) and CD8(+) splenocytes for IFN-gamma and TNF-alpha revealed comparable T cell-mediated responses in AhR(-/-) and AhR(+/-) mice. Previously infected AhR(-/-) and AhR(+/-) mice both exhibited enhanced resistance to reinfection with L. monocytogenes. These data provide the first evidence that AhR is required for optimal resistance but is not essential for adaptive immune response to L. monocytogenes infection.

Sepsis and meningitis due to Listeria monocytogenes

PURPOSE

This study focused on the effect of immuno-compromising conditions on the clinical presentation of severe listerial infection.

PATIENTS AND METHODS

Nine human listeriosis cases seen from 1991-2002 were reviewed. All adult patients, from whose blood, peritoneal fluid or cerebrospinal fluid (CSF) the L. monocytogenes was isolated, were included in this retrospective study.

RESULTS

Listeriosis presented as primary sepsis with positive blood cultures in 5 cases and meningitis with positive CSF cultures in 4 cases. All of these patients had at least one underlying disease, most commonly, hematologic malignancy, diabetes mellitus, amyloidosis and hepatic cirrhosis; 55.6% had received immunosuppressive or corticosteroid therapy within a week before the onset of listeriosis. The patients were adults with a mean age of 60 years. Fever, night sweats, chills and lethargy were the most common symptoms; high temperature (> 38 degrees C), tachycardia, meningeal signs and poor conditions in general were the most common findings on admission. The mortality rate was 33.3% and was strictly associated with the severity of the underlying disease. Mortality differences were significant between sepsis (20%) and meningitis (50%) patients.

CONCLUSION

Listeriosis as an uncommon infection in our region and that immuno- suppressive therapy is an important pre-disposing factor of listeriosis. Sepsis and meningitis were more common in this group of patients and had the highest case-fatality rate for food-borne illnesses.

Neonatal Listeriosis

In Western developed countries, Listeria monocytogenesis not an uncommon pathogen in neonates. However, neonatal listeriosis has rarely been reported in Taiwan. We describe two cases collected from a single medical institute between 1990 and 2005. Case 1 was a male premature baby weighing 1558 g with a gestational age of 31 weeks whose mother had fever with chills 3 days prior to delivery. Generalized maculopapular rash was found after delivery and subtle seizure developed. Both blood and cerebrospinal fluid culture collected on the 1st day yielded L. monocytogenes. In addition, he had ventriculitis complicated with hydrocephalus. Neurologic development was normal over 1 year of follow-up after ventriculoperitoneal shunt operation. Case 2 was a 28-weeks' gestation male premature baby weighing 1180 g. Endotracheal intubation and ventilator support were provided after delivery due to respiratory distress. Blood culture yielded L. monocytogenes. Cerebrospinal fluid showed pleocytosis but the culture was negative. Brain ultrasonography showed ventriculitis. Sudden deterioration with cyanosis and bradycardia developed on the 8th day and he died on the same day. Neonatal listeriosis is uncommon in Taiwan, but has significant mortality and morbidity. Early diagnosis of perinatal infection relies on high index of suspicion in perinatal health care professionals.

A combination of diagnostic tools for rapid screening of ovine listeriosis

A combined serological and PCR method for the detection of Listeria monocytogenes infection in symptomatic and asymptomatic ovine flocks was evaluated. Seventy-eight milk samples and 157 serum samples were analysed using a L. monocytogenes PCR detection kit and an anti-listeriolysin O IgG immunoassay kit. The combined use of these commercial kits allowed a rapid and effective detection of L. monocytogenes infection in both the early stage, before seroconversion, and in a later phase, even after antibiotic therapy.

Listeria monocytogenes in platelets: a case report

BACKGROUND

Efforts to reduce bacterial contamination in platelets (PLTs) have led to implementation of tests for bacterial detection before product release. Although relatively rare as a human pathogen, Listeria monocytogenes often causes serious illness and has a case-fatality rate of 20 percent.

CASE REPORT

PLTs from an asymptomatic 58- year-old Hispanic male with a long history of PLT donation were culture-positive for the presence of L. monocytogenes. The pulsed-field gel electrophoresis (PFGE) pattern of the isolate matched two other L. monocytogenes isolates in the CDC National PulseNet database. Public health investigation found no evidence that the other two isolates were epidemiologically related to the PLT donor, who remained asymptomatic.

CONCLUSION

A cluster of listeriosis cases was detected by PFGE but the significance is unknown. Organisms of public health significance should be reported to health departments. Better surveillance and reporting are needed in the efforts to improve blood product safety.

Assessment of interleukin-12, gamma interferon, and tumor necrosis factor alpha secretion in sera from mice fed with dietary lipids during different stages of Listeria monocytogenes infection

Recent experimental observations have determined that long-chain n-3 polyunsaturated fatty acids suppress immune functions and are involved in the reduction of infectious disease resistance. BALB/c mice were fed for 4 weeks with one of four diets containing either olive oil (OO), fish oil (FO), hydrogenated coconut oil, or a low fat level. Interleukin-12p70 (IL-12p70), gamma interferon (IFN-gamma), and tumor necrosis factor alpha (TNF-alpha) production in the sera of mice fed these diets and challenged with Listeria monocytogenes were determined by enzyme-linked immunosorbent assay. In addition, bacterial counts from spleens of mice were carried out at 24, 72, or 96 h of infection. Here, we quantified an initial diminution of production of both IL-12p70 and IFN-gamma, which appear to play an important role in the reduction of host resistance to L. monocytogenes infection. In addition, an efficient elimination of L. monocytogenes was observed in spleens of mice fed a diet containing OO at 96 h of infection, despite reductions in IL-12p70 and TNF-alpha production, suggesting an improvement of immune resistance. Overall, our results indicate that the initial reduction of both IL-12 and IFN-gamma production before L. monocytogenes infection represents the most relevant event that corroborates the impairment of immune resistance by n-3 polyunsaturated fatty acids during the different stages of infection. However, we speculate that the modulation of other cytokines must be also involved in this response, because the alteration of cytokine production in mice fed an FO diet in a late phase of L. monocytogenes infection was similar to that in mice fed OO, whereas the ability to eliminate this bacterium from the spleen was improved in the latter group.

Gene expression profiling of mouse host response to Listeria monocytogenes infection

The purpose of this study was to evaluate gene expression profiles in the liver and blood for prediction of infection severity from Listeria monocytogenes (LM). Mice were injected with medium broth (control) or a nonlethal or lethal dose of LM and sacrificed 6 h later. Gene expression changes were determined using Affymetrix MGU74Av2 GeneChips and confirmed by real-time polymerase chain reaction analysis. We identified discernable genes whose gene expression profiles can be used in pattern recognition to predict and classify samples in differently treated groups, with >or=90% accuracy in liver samples and 80% accuracy in blood at prediction; however, different genes were predictive in each tissue. Our results suggest that gene expression profiling in response to LM in mice may be able to distinguish samples in groups with varying severity of infection and provide information in finding molecular mechanisms and early biomarkers for subsequent conventional clinical endpoints.

Ability of Orally Administered IFN-α-Containing Transgenic Potato Extracts to InhibitListeria monocytogenesInfection

Type I interferons (IFN-alpha/beta) were originally thought to be antiviral cytokines, but it has recently been reported that they also play an important role in potentiating innate and adaptive immune responses. Moreover, several studies have shown that the oral administration of type I IFN ameliorates various biologic activities. Here, we studied the ability of orally administered IFN-alpha to protect mice from systemic Listeria monocytogenes infection. Daily oral administration of purified natural IFN-alpha at a concentration of 1000 international units (IU)/20 microl reduced the bacterial burden in infected organs. We also examined the protective effect of IFN-alpha expressed in transgenic potato plants. A much lower concentration of IFN-alpha (20 IU/ 20 microl) in the plant extracts was almost as protective as much higher concentrations of purified natural IFN-alpha. Our observations indicate that transgenic cytokine-expressing plants can be used prophylactically as edible pharmaceuticals to enhance systemic defense responses in humans and animals.

Infection-stimulated fibrin deposition controls hemorrhage and limits hepatic bacterial growth during listeriosis

Bacterial infections are major causes of human mortality. The activation of coagulation pathways leading to the deposition of insoluble fibrin frequently accompanies bacterial infection, and much attention has focused upon the pathological attributes of infection-stimulated fibrin deposition. Nevertheless, here we present conclusive evidence that infection-stimulated fibrin deposition can perform critical protective functions during bacterial infection. Specifically, we demonstrate that coagulation-impaired fibrin(ogen)-deficient mice, in comparison with genetically matched control mice, display increased mortality upon peritoneal infection with the gram-positive facultative intracellular bacterium Listeria monocytogenes. To distinguish effects of fibrinogen from those of fibrin, we treat wild-type mice with warfarin, an anticoagulant that suppresses fibrin formation without impacting fibrinogen levels. Warfarin treatment exacerbates listeriosis, suggesting that fibrin is the key mediator of protection. With regard to the underlying protective mechanisms, we demonstrate that fibrin(ogen) suppresses anemia, reduces hemorrhagic pathology, and limits bacterial growth during listeriosis. Despite confirming a prior report that fibrin(ogen) promotes the peritoneal clearance of the extracellular bacterium Staphylococcal aureus, we demonstrate that fibrin(ogen) plays little role in controlling peritoneal numbers of L. monocytogenes bacteria or the dissemination of L. monocytogenes bacteria from the peritoneal cavity. Rather, fibrin(ogen) primarily limits the growth of these intracellular bacteria within hepatic tissue. While the pathological potential of excessive infection-stimulated fibrin deposition is well appreciated, our findings reveal that fibrin can function protectively, via multiple mechanisms, during bacterial infection.

Uncaria tomentosa extract increases the number of myeloid progenitor cells in the bone marrow of mice infected with Listeria monocytogenes

In this study, we demonstrated that Uncaria tomentosa extract (UTE) protects mice from a lethal dose of Listeria monocytogenes when administered prophylactically at 50, 100, 150 and 200 mg/kg for 7 days, with survival rates up to 35%. These doses also prevented the myelosuppression and the splenomegaly caused by a sublethal infection with L. monocytogenes, due to increased numbers of granulocyte-macrophage progenitors (CFU-GM) in the bone marrow. Non-infected mice treated with 100 mg/kg UTE also presented higher numbers of CFU-GM in the bone marrow than the controls. Investigation of the production of colony-stimulating factors revealed increased colony-stimulating activity (CSA) in the serum of normal and infected mice pre-treated with UTE. Moreover, stimulation of myelopoiesis and CSA occurred in a dose-dependent manner, a plateaux being reached with the dose of 100 mg/kg. Further studies to investigate the levels of factors such as IL-1 and IL-6 were undertaken. We observed increases in the levels of IL-1 and IL-6 in mice infected with L. monocytogenes and treated with 100 mg/kg of UTE. White blood cells (WBC) and differential counting were also performed, and our results demonstrated no significant changes in these data, when infected mice were pre-treated with 100 mg/kg of UTE. All together, our results suggest that UTE indirectly modulates immune activity and probably disengages Listeria-induced supression of these responses by inducing a higher reserve of myeloid progenitors in the bone marrow in consequence of biologically active cytokine release (CSFs, IL-1 and IL-6).

Isolation of pathogenic Listeria monocytogenes and detection of antibodies against phosphatidylinositol-specific phospholipase C in buffaloes

The isolation of pathogenic Listeria spp. in bacteriological samples, and anti-phosphatidylinositol-specific phospholipase C (anti-PIPLC) antibodies in sera of buffaloes were studied. Isolation of the pathogen was attempted from the samples by selective enrichment in University of Vermont Medium and plating onto Dominguez-Rodriguez isolation agar. Pathogenicity of the isolates was tested by Christie, Atkins, Munch Petersen test and mice incoulation test. Listeria spp. and L. monocytogenes were isolated from 8.8 and 2.4%, and 4.8 and 1.6% of 125 each meat and blood samples, respectively. Out of the 125 samples each of feacal, nasal and vaginal swabs from buffaloes 8 and 4%, 13.6 and 2.4%, and 6.4 and 2.4% were positive for Listeria spp. and L. monocytogenes, respectively. L. ivanovii was confirmed from 0.8% vaginal sample. A total of 125 serum samples were tested by phosphatidylinositol-specific phospholipase C (PIPLC) based indirect ELISA of which 4.0% turned out to be seropositive.

Use of listeriolysin O and internalin A in a seroepidemiological study of listeriosis in Swiss dairy cows

Recombinant listeriolysin O and internalin A were used as antigens in an enzyme-linked immunosorbent assay (ELISA) for the specific detection of anti-Listeria monocytogenes antibodies in cattle. The results showed sensitivities and specificities of 82 and 92%, respectively, for the listeriolysin O ELISA, and 100 and 90%, respectively, for the internalin A ELISA, respectively. The test may be useful for the confirmation of listeria-related abortions and mastitis but does not seem to be indicated for use in the diagnosis of listeria-related encephalitis in cattle. A representative sample of 1,652 serum samples from the healthy dairy cattle population in Switzerland was tested by both ELISAs. The results showed that 11% of the healthy dairy cows in Switzerland simultaneously presented antibodies toward listeriolysin O and internalin A, and 48% of the farms had one or several animals simultaneously positive by assays with both antigens. Multivariable analysis at the farm level confirmed that feeding of silage represents a significant risk factor for a positive listeria serology. Detailed analysis identified corn silage but not grass silage as the major factor in this association. Cattle breed and hygiene on the farm were also identified as significant factors associated with the serological status of farms. In conclusion, the results of the study show that internalin A is a promising new antigen for use in listeria serology and that specific anti-L. monocytogenes antibodies are found in a significant proportion of healthy dairy cows in Switzerland.

Neutrophil-Kupffer cell interaction: a critical component of host defenses to systemic bacterial infections

Most bacteria that enter the bloodstream are taken up and eliminated within the liver. The specific mechanisms that underlie the role of the liver in the resolution of systemic bacterial infections remain to be determined. The vast majority of studies undertaken to date have focused on the function of resident tissue macrophages (Kupffer cells) that line the liver sinusoids. Indeed, it is often reported that Kupffer cells ingest and kill the bulk of organisms taken up by the liver. Recent studies indicate, however, that phagocytosis by Kupffer cells is not the principal mechanism by which organisms are eliminated. Rather, elimination depends on the complex interaction of Kupffer cells and bactericidal neutrophils that immigrate rapidly to the liver in response to infection. We discuss the critical role of neutrophil-Kupffer cell interaction in innate host defenses and, conceivably, the development and expression of adaptive immunity in the liver.

Organ-specific regulation of the CD8 T cell response to Listeria monocytogenes infection

The intestinal mucosal CD8 T cell response to infection with Listeria monocytogenes was measured using MHC class I tetramers and was compared with the response in peripheral blood, secondary lymphoid tissue, and liver. To assess the vaccination potential of Listeria and to analyze responses in C57BL/6 mouse strains, a recombinant Listeria expressing OVA (rLM-ova) was generated. The response peaked at 9 days postinfection with a much larger fraction of the intestinal mucosa and liver CD8 T cell pool OVA specific, as compared with the spleen. However, these differences were not linked to bacterial titers in each site. The higher responses in lamina propria and liver resulted in a larger CD8 memory population in these tissues. Furthermore, the level of memory induced was dependent on infectious dose and inversely correlated with the magnitude of the recall response after oral challenge. Recall responses in the tissues were most robust in the lamina propria and liver, and reactivated Ag-specific T cells produced IFN-gamma. Infection of CD40- or MHC class II-deficient mice induced poor CD8 T cell responses in the intestinal mucosa, but only partially reduced responses in the spleen and liver. Overall, the results point to novel pathways of tissue-specific regulation of primary and memory antimicrobial CD8 T cell responses.

Relationships between IFNgamma, IL-6, corticosterone, and Listeria monocytogenes pathogenesis in BALB/c mice

The relationships between Listeria monocytogenes (LM) pathogenesis, based on bacterial load, and serum levels of IL-6, IFNgamma, and corticosterone (CORT) were quantified. Serum IFNgamma levels increased along with the LM burden; however, with LM burdens > or =3 x 10(6) CFU per spleen, the serum IFNgamma level decreased along with a decrease in splenic weight. Serum IL-6 levels exponentially increased with increases of LM, and the CORT level positively correlated with the increase in IL-6 and LM. The serum level of IFNgamma appeared to be a good biomarker of the host's ability to combat the infection only when the LM burden did not exceed a critical level (>3 x 10(6) CFU per spleen). Interestingly, the LM load at which the IFNgamma level began to decline was near the dose at which the IL-6 concentration exponentially increased, suggesting a transition point shift from stress (assessed as CORT level) being immunoenhancing to becoming immunosuppressive. The IL-6:IFNgamma ratio may be a good indicator of disease severity and/or the ability to cope with an infection.

Consumption of eicosapentaenoic acid and docosahexaenoic acid impair murine interleukin-12 and interferon-gamma production in vivo

In mice, individual dietary omega-3 polyunsaturated fatty acids n-3 (PUFA) were found to be sufficient to effect the changes in circulating interleukin (IL)-12 and interferon (IFN)-gamma levels that were previously seen in fish oil-fed mice. Weanling female C3H mice were fed one of five experimental diets. All five diets met all known nutritional requirements for mice and differed only in the fat source. After 4 weeks, mice were challenged with live Listeria monocytogenes or sterile PBS. Twenty-four hours after infection, n-3 PUFA-fed mice had significantly lower circulating IL-12 p70 and IFN-gamma than mice fed the control diet (P<.01). In addition, splenic cytokine mRNA for IL-12 p40, tumor necrosis factor-alpha, and IL-1beta were lower in infected mice fed n-3 PUFA-containing diets than in mice fed the olive oil ethyl esters control diet. The reduction of IL-12 and IFN-gamma production by n-3 PUFA may have important implications for host infectious disease resistance.

Protective effect of a traditional Japanese medicine, Bu-zhong-yi-qi-tang (Japanese name: Hochu-ekki-to), on the restraint stress-induced susceptibility against Listeria monocytogenes

In this study, the effect of traditional Japanese (Chinese) medicine, Bu-zhong-yi-qi-tang (Japanese name: Hochu-ekki-to, HOT), on the restraint stress treatment (RST)-induced susceptibility against Listeria monocytogenes (L. monocytogenes) was examined. When RST was performed every day for 10 h from the day of infection, the bacterial numbers were increased at 3 and 5 days after the infection. Oral pretreatment with HOT for 7 days prevented such increases. Pretreatment with HOT prevented the suppression of antigen-specific IFN-gamma production by RST. HOT also prevented suppression of macrophage accumulation, including MHC-class II positives, in the peritoneal cavity and their bactericidal activity by RST. HOT suppressed the serum corticosterone level elevated by RST in infected mice. Taken together, the suppression of corticosterone using HOT participates in the prevention of suppressions of the bactericidal activity of macrophages, migration of macrophages and antigen-specific IFN-gamma production of Th1 cells by RST. Our findings suggest that HOT is a useful drug for patients suffering from stress disease to reduce the susceptibility to bacterial infection.

Plasma cytokine response in mice with bacterial infection

BACKGROUND

Exposure to microorganisms elicts the production of cytokines. These soluble factors enhance several innate immune functions and regulate the ensuing specific immune response aimed at limiting the spread of infection.

AIM

This study was undertaken to quantify the plasma levels of pro-inflammatory cytokines during the course of primary Listeria monocytogenes and Campylobacter jejuni infection. Using an in vivo infection the relationship between endogenous cytokines and the bacterial number in the liver of infected animals was examined.

METHODS

C57BL/6 mice were infected by the intraperitoneal route. At different time points we determined the number of colony-forming units of bacteria in the liver of infected animals and paralled these with the plasma levels of interferon-gamma (IFN-gamma), tumor necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6) measured by enzyme immunoassays.

RESULTS

L. monocytogenes infection lasted 10-11 days. IFN-gamma production occurred in the early phase but was more pronounced after day 4, following the appearance of specific immunity. The duration of experimental campylobacteriosis was 15 days. Early IFN-gamma production was not significant but a progressive rise of this cytokine in plasma was seen during the second week post infection. Mice produced measurable amounts of plasma TNF-alpha immediately after being given viable L. monocytogenes, peaking on day 2-3 when the greatest number of bacteria was present in the examined organs. During C. jejuni infection plasma TNF-alpha was produced in a similar manner, but the highest concentrations were found a few days later than in listeriosis, in correlation with the different course of campylobacteriosis. The quantity of IL-6 increased and decreased in concordance with clearance of L monocytogenes and the clinical status of the animals. C. jejuni did not promote the induction of this cytokine. This is to some extent an unusual finding. With respect to the role of IL-6 in Th2 responses and antibody production, the appearance of this cytokine in campylobacteriosis was more expected.

DISCUSSION

During systemic bacterial infection, a network of pro-inflammatory cytokines is activated and blood levels of these cytokines are elevated, albeit inconsistently, with large individual variations and depending on microbial characteristics and structure.

Pregnancy-associated glycoprotein levels in pregnant goats inoculated with Toxoplasma gondii or Listeria monocytogenes: a retrospective study

The pregnancy-associated glycoprotein (PAG) concentration profiles of goats that had been experimentally inoculated with either Toxoplasma gondii or Listeria monocytogenes are described. All goats were examined regularly by ultrasonography. In T. gondii-infected females (n = 5), a slow decrease of PAG was observed throughout a period of 55 to 74 d after inoculation. Afterwards, the goats either aborted (n = 4) or kidded 1 dead and 1 weak fetus (n = 1). In L. monocytogenes-infected females (n = 8), a marked decrease of PAG was observed from the day of inoculation. Abortion occurred within 9 to 11 d post inoculation (n = 7). Only 1 goat kidded a healthy fetus.

Effects of Chlorella vulgaris on bone marrow progenitor cells of mice infected with Listeria monocytogenes

In this study we investigated the effects of the treatment with Chlorella vulgaris extract (CVE) on the hematopoietic response of granulocyte-macrophage colony-forming unit (CFU-GM) of mice infected with a sublethal dose of Listeria monocytogenes (1 x 10(4) organisms/animal). CVE was given orally as 50 mg/kg/day for 5 days. In the CVE treated/infected groups L. monocytogenes was administered at the end of CVE treatment. The colony stimulating activity of the serum (CSA) was also studied in all groups. Although no effects on CFU-GM, as compared to controls, were observed in the groups receiving CVE alone, the extract produced an increase in CSA levels as compared to controls. On the other hand, the presence of the infection led to a significant reduction in the numbers of CFU-GM as observed at 48 and 72 h after the infection, in spite of the significant increase in serum CSA activity. CVE treatment of infected animals restored the numbers of CFU-GM to control levels. In the treated/ infected group the increased serum CSA was significantly higher than that observed in the only infected group. The CVE treatment (50 and 500 mg/kg) of mice infected with a dose of 3 x 10(5) bacteria/animal, which was lethal for all the non-treated controls, produced a dose-response protection which led to a 20 and 52% survival, respectively. These results demonstrated that CVE produces a significant increase in the resistance of the animals infected with L. monocytogenes, and that this protection is due, at least in part, to increased CFU-GM in the bone marrow of infected animals.

The origin and function of soluble CD14 in experimental bacterial meningitis

Murine experimental meningitis models induced by either Escherichia coli LPS, live Streptococcus pneumoniae, or Listeria monocytogenes were used to study the origin and potential function of soluble CD14 (sCD14) in the brain during bacterial meningitis. Whereas intracerebral infection caused only a minor and/or transient increase of sCD14 levels in the serum, dramatically elevated concentrations of sCD14 were detected in the cerebrospinal fluid. Reverse-transcriptase PCR and FACS analysis of the leukocytes invading the subarachnoid compartment revealed an active amplification of CD14 transcription and concomitant surface expression. These findings were confirmed by in situ hybridization and immunohistochemical analysis. In contrast, parenchymal astrocytes and microglial cells were shown not to significantly contribute to the elevated levels of sCD14. Simultaneous intracerebral inoculation of rsCD14 and S. pneumoniae resulted in a markedly increased local cytokine response. Taken together, these data provide the first evidence that sCD14 can act as an inflammatory co-ligand in vivo. Thus, during bacterial meningitis, sCD14 is massively released by intrathecal leukocytes, and the sCD14 found in the cerebrospinal fluid can play an important role in the pathogenesis of this disease.

Interleukin-12 promotes enhanced resistance to Listeria monocytogenes infection of lead-exposed mice

The heavy metal lead (Pb) has been shown to downregulate various parameters of cell-mediated immune (CMI) responses. This inhibition of CMI responses by Pb is exemplified by a higher mortality rate upon infections with sublethal doses of a variety of pathogens. Unlike Pb, which lowers host resistance, interleukin-12 (IL-12) exerts a substantial stimulatory influence on the host response to intracellular bacteria such as Listeria monocytogenes. To explore the influence of IL-12 in mice rendered susceptible to Listerial infection by oral exposure to Pb, we determined bacterial burdens and production of interferon gamma (IFN-gamma). As expected, Pb-exposed mice had increased morbidity due to higher Listerial titers as compared to control mice. However, administration of exogenous IL-12 reversed the Pb-induced inhibition of host defense and boosted the resistance of the non-Pb-treated mice. The enhanced CMI responses observed in both IL-12-treated groups were accompanied with elevations of IFN-gamma in the sera and spleens. Significant reduction in the number of viable Listeria in Pb-exposed mice upon IL-12 administration suggests that the processes downstream of IL-12 production were intact in the Pb-exposed mice and that the inhibition by Pb was due to the lack of functional IL-12. Alternatively, the exogenous IL-12 may have overcome a downstream effect by enhancing an secondary pathway. Support for the former hypothesis is based on the observation that Pb induced elevated levels of p40 splenic messenger RNA since increased p40 expression would result from lack of IL-12 formation. Contrary to the IFN-gamma levels, significantly higher levels of IL-6 and corticosterone were observed in the sera and spleens of Pb-exposed mice upon infection, suggesting heightened stress in the absence of IL-12. Overall, the results suggest that an environmental pollutant such as Pb can enhance the stress response, which naturally occurs during an infection, and can further compromise health by lowering host resistance by altering cytokine levels.

[The effect of Listeria monocytogenes on the blood system]

The influence of L. monocytogenes on the hemopoietic system was studied in mouse experiments. All elements of hemopoiesis were damaged. The most pronounced changes developed in erythropoiesis. This was testified by a decrease in erythrocyte count and hemoglobin content in peripheral blood, by the hypoplasia of the hemopoietic erythroid germ in the marrow, as well as by the decrease of yield in culture CFU-E. These changes in the hemopoietic tissue supposedly caused by the direct action of L. monocytogenes and its toxins.

A nested PCR method to detect Listeria monocytogenes in artificially contaminated blood specimens

A nested PCR-based test was developed for the detection of Listeria monocytogenes in blood specimens from patients with listeriosis. Two pairs of oligonucleotide primers were designed to amplify a 1395-bp and a 453-bp fragment of the iap gene of L. monocytogenes. Amplified products were analysed with gel electrophoresis and stained with ethidium bromide. The PCR method described could be routinely used to diagnose listeriosis.

A case of congenital Listeria septicemia associated with high levels of inflammatory cytokines

A case of congenital Listeria septicemia is reported. A 2256 g male infant suffering from respiratory and circulatory failure with shock-like symptoms and high levels of inflammatory cytokines (tumor necrosis factor-alpha, interleukin-1 beta, -6, and -8), was admitted to the Morioka Red Cross Hospital. Listeria monocytogenes was cultured from cord blood, contents from the external ear canal, rectum and stomach. The infant was treated with surfactant replacement as well as conventional therapy. The high levels of interleukin-1 beta decreased with the improvement of the circulatory function, which might have been the major cause of the poor clinical state.

Cell wall-deficient forms (L-forms) of Listeria monocytogenes in experimentally infected rats

Experimental infections were induced with different bacterial forms of Listeria monocytogenes: parental (S-forms), protoplastic (L-forms) and combined inoculum of both forms by i.p. injection of rats. The parental bacterial forms (S-forms) were isolated up to 7 days after challenge from the peritoneal cavity and the liver, while the L-forms were isolated up to 60 days from the peritoneal cavity. Continuous adhesion of L-forms on the peritoneal macrophage surface was found by scanning-electron microscopy. Erythrocyte and leucocyte count as well as some clinical chemistry parameters were measured during infections. They showed different dynamics in the three experimental groups. Histomorphological changes in the liver (microabscesses and mononuclear cellular granulomas) of infected animals were observed. They were less intensive and appeared later in rats infected with L-forms. The experiments demonstrated that infections caused by parental bacterial forms and by combined inoculum took an acute course, while the infection caused by L-forms could be distinguished as a prolonged and persistent one.

Listeriosis after fludarabine treatment for chronic lymphocytic leukemia

The authors report a case of Listeria monocytogenes septicemia in a patient with advanced CLL after a single course of fludarabine, without any other immunosuppressive therapy e.g. corticosteroids. The immunosuppressive action of fludarabine in patients who are already severely immunosuppressed must be considered from a diagnostic and therapeutic point of view. Listeriosis and other opportunistic infections, like pneumocystis carinii pneumonia, have been reported during and after treatment with purine analogues. Prophylaxis with cotrimoxazole must therefore be discussed in patients with CLL treated with fludarabine.

A role for macrophage scavenger receptors in atherosclerosis and susceptibility to infection

Macrophage type-I and type-II class-A scavenger receptors (MSR-A) are implicated in the pathological deposition of cholesterol during atherogenesis as a result of receptor-mediated uptake of modified low-density lipoproteins (mLDL). MSR-A can bind an extraordinarily wide range of ligands, including bacterial pathogens, and also mediates cation-independent macrophage adhesion in vitro. Here we show that targeted disruption of the MSR-A gene in mice results in a reduction in the size of atherosclerotic lesions in an animal deficient in apolipoprotein E. Macrophages from MSR-A-deficient mice show a marked decrease in mLDL uptake in vitro, whereas mLDL clearance from plasma occurs at a normal rate, indicating that there may be alternative mechanisms for removing mLDL from the circulation. In addition, MSR-A-knockout mice show an increased susceptibility to infection with Listeria monocytogenes or herpes simplex virus type-1, indicating that MSR-A may play a part in host defence against pathogens.

Acute-phase proteins in perinatal human plasma

Plasma from eight newborns (4 pre-term and 4 full-term) with early-onset (< 72 h) sepsis and six apparently healthy controls was analyzed. The presence of spots identified as haptoglobin and serum amyloid A protein was the electrophoretic result most consistently associated with disease. Time course monitoring showed rises, peaks and declines of spot intensity as expected for acute-phase proteins induced by transient stimuli. Haptoglobin beta chains appear to be undersialated in pre-term newborns, whereas post-translational modifications of alpha chains and serum amyloid A protein are similar to those observed in adults. The undersialation of beta chain and occurrence of alpha chain phenotypes different from those found in maternal serum indicate that perinatal haptoglobin originates from neonatal synthesis.

Detection of anti-listeriolysin O in dairy cattle experimentally infected with Listeria monocytogenes

A dot-blot assay and an enzyme-linked immunosorbent assay (ELISA) to detect listeriosis in dairy cattle were developed that detected anti-listeriolysin O antibodies in the serum of cows experimentally infected with Listeria monocytogenes. The tests utilized purified listeriolysin O (LLO) as the detection antigen and streptolysin O (SLO) to absorb cross-reacting antibodies. The two tests were compared with an agglutination test that used formalin-killed whole L. monocytogenes cells. Blood samples were collected periodically from 17 cows after intramammary gland infection, and the development of anti-LLO antibodies was followed by an agglutination test, the dot-blot test, and the ELISA. In general, an agglutination titer of > 640 was needed for a positive dot-blot anti-LLO test for nonpregnant cows. However, 1 pregnant cow with an agglutination titer of 20 was positive in the dot-blot test. The ELISA was as sensitive as the dot-blot assay but gave a quantitative measurement to distinguish serum samples of positive reactors from cross-reactors. The specificity of the LLO-based tests was further evaluated using serum from cows that had been experimentally infected with Staphylococcus aureus, 17 of which had agglutination titers for L. monocytogenes > 640. These elevated agglutination titers were probably due to cross-reacting bacterial antigens because serum from 9 of 17 of these animals did not react to the purified LLO antigen. A positive response to the LLO-based dot-blot and ELISA assays is indicative of previous or current infection with L. monocytogenes.

Reactive nitrogen intermediates suppress the primary immunologic response to Listeria

Reactive nitrogen intermediates (RNI), e.g., nitric oxide derived from a terminal guanido nitrogen atom of L-arginine, exhibit potent antimicrobial activity in vitro. The function of these intermediates in host defenses in vivo, however, is presently unclear. Experiments were undertaken to determine the role of RNI in the resolution of primary listerial infections of the liver. Serum RNI levels were elevated significantly in mice infected with Listeria monocytogenes. Moreover, a marked increase in RNI production was found in cultures of the parenchymal, as well as the nonparenchymal, liver cells obtained from Listeria-infected mice. RNI did not kill Listeria treated directly, however, nor were they a factor in the listericidal activity exhibited by hepatic cells. Rather, the elevated production of RNI during primary infection appeared to promote the replication of Listeria in vivo. Mice administered NG-monomethyl-L-arginine, a competitive inhibitor of RNI production, exhibited a 10- and a 100-fold reduction in the number of Listeria in their lives on days 3 and 7 postinfection, respectively. In vitro, NG-monomethyl-L-arginine stimulated the Ag-specific proliferation of T lymphocytes derived from Listeria-infected mice at concentrations that inhibited RNI production. These latter findings suggest that the elevated production of RNI during primary listerial infections suppresses host defenses by diminishing the proliferation and, consequently, the biologic response of immune cell populations.

Listeria brainstem encephalitis: two own cases and literature review

We analysed two of our own and 21 patients described in the literature with listeria brainstem encephalitis. The disease was characterised by a prodromal state with fever, nausea and headache followed by severe brainstem dysfunction with multiple cranial nerve palsies, ataxia, respiratory insufficiency and coma. The diagnosis was established by isolation of Listeria monocytogenes from CSF and/or serum. Serological tests are without diagnostic evidence. Cerebrospinal fluid examination may not initially point to a bacterial infection. Computed tomography and magnetic resonance imaging technique might supply evidence of brainstem involvement and contribute to an early diagnosis. There is a high percentage of lethal outcome without early antibiotic therapy.

Western blot analysis of the antibody response in patients with Listeria monocytogenes meningitis and septicemia

The antibody response in patients with Listeria monocytogenes septicemia and/or meningitis was investigated using Western blot analysis (WBA). Protein antigen preparations were produced from two strains of Listeria monocytogenes, representing serogroup 1 and 4, by sonication and differential centrifugation. IgG antibodies from 8 (50%) of 16 patients with culture verified septicemia and/or meningitis due to Listeria monocytogenes reacted with a 93 kDa antigen from serogroup 1, in contrast to IgG antibodies from only 1 (2%) of 51 controls; these controls represented 21 patients with infections caused by other bacteria and 30 apparently healthy blood donors. Furthermore, IgM antibodies from 3 (19%) of the patients with listeric infections bound to a 106 kDa protein antigen in contrast to none of the controls. In 3 (33%) of 9 patients from whom acute and convalescence serum were available, the patients responded by producing antibodies against new protein antigens. Current methods used in routine serological investigations, i.e. complement fixation and O-agglutination tests, were positive in only 4 (24%) of the 16 patients with listeriosis. The results point to the possibility of designing new immunoassays for detection of septicemia and meningitis caused by Listeria monocytogenes.

Human listeriosis in Scotland 1967-1988

In order to study the epidemiology of listeriosis from 1967-1988 in Scotland, various sources of data were examined. These included reports by laboratories, reference laboratory records, hospital death and discharge records, death certificates and hospital laboratory records. Cases were reported from 13 of Scotland's 15 Health Boards. Case ascertainment via laboratory reports to the Communicable Diseases (Scotland) Unit was validated in two Health Boards. A total of 198 cases was identified with an overall attack rate which increased from 0.5 per million in 1967-1971 to 7.0 per million in 1987-1988. Feto-maternal cases were the commonest (64%). Of all cases, 33% were neonates; 53% presented with bacteraemia and 41% with meningitis. The predominant serovar of Listeria monocytogenes was 4b.

Human rTNF alpha augments anti-bacterial resistance in mice: potentiation of its effects by recombinant human rIL-1 alpha

Treatment with human recombinant tumour necrosis factor-alpha (rTNF alpha) significantly enhanced resistance to Listeria monocytogenes infection in mice. The level of protection (which was dose-dependent and maximal at approximately 1.0 microgram per mouse) was similar to that previously reported for the monokine rIL-1 alpha, although somewhat greater amounts of rTNF alpha than rIL-1 alpha were required. Combined administration of suboptimal concentrations of rTNF alpha and rIL-1 alpha resulted in significant enhancement of resistance beyond that obtained with either monokine alone, whereas further increases in anti-listeria resistance were not observed at doses of rTNF alpha or IL-1 alpha that were themselves capable of inducing substantial protection. Combined administration of rTNF alpha and rIL-1 alpha was associated with a delay in onset and lessening in severity of the lymphopenia that accompanied L. monocytogenes infection. The reduced bacterial burden in the spleens and livers of mice treated with rTNF alpha and rIL-1 alpha was associated with a more rapid decline in serum colony-stimulating activity. Peritoneal macrophages from rTNF alpha- and rIL-1 alpha-treated listeria-infected mice did not demonstrate enhanced anti-listeria activity in vitro. These results provide further evidence for the potential benefits of rTNF alpha and other cytokines in promoting anti-bacterial resistance. They further suggest that use of combinations of cytokines is a strategy worthy of further consideration.

Are tumor necrosis factor (TNF) or cortisol of value for the diagnosis of acute septicemia?

Early diagnosis is of great importance to improve the prognosis of septicemia. Traditional laboratory tests are either delayed like blood cultures, or unspecific like WBC count or ESR. In this retrospective pilot study we have assayed plasma cortisol, blood sugar and serum tumor necrosis factor (TNF) from patients with verified septicemia. With the approach used in this study none of the tests were able to differentiate between septicemia and other infectious febrile illnesses, or to predict if the causing organism was gram-positive or gram-negative.

Tumour necrosis factor in neonatal listeriosis: a case report

A newborn with fatal neonatal listeriosis developed septic shock, neutropenia, thrombocytopenia and profound hypoxaemia due to severe pulmonary hypertension. Tumour necrosis factor alpha, interleukin-1-beta and interferon-gamma serum concentrations were markedly elevated, suggesting the participation of these cytokines in the aetiopathogenesis of shock induced by Listeria monocytogenes in the neonate.

Multiple forms of IFN-beta 2/IL-6 in serum and body fluids during acute bacterial infection

Many of the major alterations in plasma proteins characteristic of the hepatic acute phase response are regulated by IFN-beta 2/IL-6. Using a specific bioassay for IFN-beta 2/IL-6, which relies on the induction of the hepatic acute phase plasma protein alpha 1-antichymotrypsin in the human hepatoma cell line Hep3B clone 2 and its inhibition by anti-rIFN-beta 2/IL-6 antiserum, we have detected high levels of IFN-beta 2/IL-6 in the body fluids of patients with acute bacterial infections. Cerebrospinal fluid from four patients with acute bacterial meningitis (Streptococcus pneumoniae, Staphylococcus aureus, two cases of Listeria monocytogenes) all had high levels of IFN-beta 2/IL-6 (up to 500 ng/ml). Two of these patients with concomitant bacteremia had lower concentrations of IFN-beta 2/IL-6 in the serum (5 to 70 ng/ml). Three additional patients with Escherichia coli, Pseudomonas aeruginosa, and Neisseria meningitidis bacteremia had high levels of serum IFN-beta 2/IL-6, as did the ankle fluid of a patient with Streptococcus canis arthritis. Normal cerebrospinal fluid and serum had little detectable IFN-beta 2/IL-6. A combination of immunoaffinity chromatography and immunoblotting procedures were used to characterize the IFN-beta 2/IL-6 species present in a representative sampling of serum and cerebrospinal fluids. Multiple immunoreactive species of IFN-beta 2/IL-6 in the size range 23 to 30 kDa as well as immunoreactive complexes in the range 60 to 70 kDa were detected in human body fluids. This is the first demonstration that previous descriptions of heterogeneity in human IFN-beta 2/IL-6 species produced in cell culture correspond to observations in the infected host.

Separate and combined effects of recombinant interleukin-1 alpha and gamma interferon on antibacterial resistance

Our laboratory has previously reported that administration of murine recombinant interleukin 1 alpha (rIL-1 alpha) substantially enhanced the resistance of mice to Listeria monocytogenes infection. Other investigators have reported that gamma interferon (IFN-gamma) plays a pivotal role in antilisteria resistance. In the present study, we have defined doses of human rIL-1 alpha that enhanced the antilisteria resistance of mice. We then addressed the possibility that combined immunotherapy with rIL-1 alpha and recombinant IFN-gamma (rIFN-gamma) might result in an additive or synergistic enhancement of antibacterial resistance. Simultaneous administration of rIL-1 alpha and rIFN-gamma enhanced antilisteria resistance (at 3 days after infection) to a greater extent than did either cytokine alone, although the results did not imply a synergistic action between the two cytokines. Experiments which examined the effects of the timing of cytokine administration indicated that maximal protection was observed when rIL-1 alpha and rIFN-gamma were administered together concomitantly with the L. monocytogenes challenge. When we compared the separate and combined protective effects of rIL-1 alpha and rIFN-gamma throughout the course of a primary L. monocytogenes infection, we observed an additive effect of the two cytokines only at 3 days after challenge, the time at which the peak bacterial burden occurs in the spleens and livers of infected mice. Histopathological comparisons of livers and spleens from cytokine-treated and control listeria-infected mice verified that cytokine treatment reduced the severity of tissue damage in cytokine-treated listeria-infected mice. In an attempt to provide a potential mechanism for the protective effects of rIL-1 alpha and rIFN-gamma administration, we compared levels of colony-stimulating activity in sera from cytokine-treated and control listeria-infected mice. The highest levels of colony-stimulating activity were detected in sera from control listeria-infected mice; somewhat lower levels were found in sera from listeria-infected mice that received rIL-1 alpha and rIFN-gamma either alone or in combination.

Early influx of Listeria-reactive T lymphocytes in liver of mice genetically resistant to listeriosis

Murine listeriosis is a classical model for investigating mechanisms of cellular immunity, which involves interaction of macrophages and T lymphocytes. The early course of this experimental infection is under control of a limited number of genes in the murine host. In the present study, we asked whether the early efficient control of bacterial growth in the liver of resistant mice is related to the expression of a more rapid specific immune response in this organ than in susceptible mice. Therefore, we compared the frequencies of Listeria monocytogenes-reactive T cells in blood, spleen, and liver of resistant C57BL/6 and susceptible C3H/He Past mice after i.v. injection of a high dose of Listeria (9 x 10(5) CFU). T cells were titrated through their ability to locally transfer a delayed-type hypersensitivity reaction to viable L. monocytogenes, an effector function potentially relevant to the early step of protective mechanisms. We observed (1) a 9- and 4-fold increase by day 1 in the frequency of Listeria-reactive transfer units in the blood of C57BL/6 and C3H mice, respectively, (2) no increase in the number of Listeria-reactive transfer units in the spleen of 2-day infected mice of both strains, and (3) a 90-fold increase, at day 2, in the number of Listeria-reactive transfer units in the liver of resistant C57BL/6 compared with only a 9-fold increase in the liver of susceptible C3H/He. These results suggest that the ability of C57BL/6 mice to control the early bacterial growth (0 to 48 h) in their liver, may be related to a rapid influx of L. monocytogenes-reactive T lymphocytes.