Groups Of Infected Mice Research Articles

IL-33 mediates the expressions of IL-5 and IL-13 in Angiostrongylus cantonensis-infected mice

Angiostrongylus cantonensis is the major cause of human eosinophilic meningoencephalitis. C57BL/6 mice were experimentally infected with 35 infectious larvae. Two groups of infected mice received intraperitoneal injections of mouse IL-33 (1μg) or anti-IL-33 monoclonal antibody (mAb) (10μg) 3days post infection (dpi) and subsequent booster shots of the same dose at 5day intervals. Blood samples from each group were collected weekly for assays. IgE levels were significantly increased in all infected mice. The eosinophil percentage and levels of IL-5 and IL-13 significantly increased in the IL-33-treated group relative to infected but non-treated animals. The level of IL-5 decreased in the mAb-treated group. The severity of eosinophilic meningitis was exacerbated in the IL-33 injected group. Taken together, these results suggest that IL-33 mediates the expressions of IL-5 and IL-13, and plays a crucial role in the pathogenesis of angiostrongylosis.

TLR2 and Nod2 Mediate Resistance or Susceptibility to Fatal Intracellular Ehrlichia Infection in Murine Models of Ehrlichiosis

Our murine models of human monocytic ehrlichiosis (HME) have shown that severe and fatal ehrlichiosis is due to generation of pathogenic T cell responses causing immunopathology and multi-organ failure. However, the early events in the liver, the main site of infection, are not well understood. In this study, we examined the liver transcriptome during the course of lethal and nonlethal infections caused by Ixodes ovatus Ehrlichia and Ehrlichia muris, respectively. On day 3 post-infection (p.i.), although most host genes were down regulated in the two groups of infected mice compared to naïve counterparts, lethal infection induced significantly higher expression of caspase 1, caspase 4, nucleotide binding oligomerization domain-containing proteins (Nod1), tumor necrosis factor-alpha, interleukin 10, and CCL7 compared to nonlethal infection. On day 7 p.i., lethal infection induced highly significant upregulation of type-1 interferon, several inflammatory cytokines and chemokines, which was associated with increased expression levels of Toll-like receptor-2 (TLR2), Nod2, MyD88, nuclear factor-kappa B (NF-kB), Caspase 4, NLRP1, NLRP12, Pycard, and IL-1β, suggesting enhanced TLR signals and inflammasomes activation. We next evaluated the participation of TLR2 and Nod2 in the host response during lethal Ehrlichia infection. Although lack of TLR2 impaired bacterial elimination and increased tissue necrosis, Nod2 deficiency attenuated pathology and enhanced bacterial clearance, which correlated with increased interferon-γ and interleukin-10 levels and a decreased frequency of pathogenic CD8+ T cells in response to lethal infection. Thus, these data indicate that Nod2, but not TLR2, contributes to susceptibility to severe Ehrlichia-induced shock. Together, our studies provide, for the first time, insight into the diversity of host factors and novel molecular pathogenic mechanisms that may contribute to severe HME.

Detection of circulating antigen in serum of mice infected with Trichinella spiralis by an IgY–IgM mAb sandwich ELISA

In this study, a sandwich ELISA based on IgY (egg yolk immunoglobulin) and IgM monoclonal antibody (mAb) against excretory-secretory (ES) antigens of Trichinella spiralis muscle larvae was developed for detection of circulating antigens (CAg) in serum from mice infected with T. spiralis. The IgY-IgM sandwich ELISA involved the use of chicken antibody IgY as a capture antibody and mouse IgM mAb 5A7G4 as a detecting antibody. This assay was able to detect as little as 1 ng/ml of ES antigens added to normal mouse serum. Two groups of BALB/c mice infected with T. spiralis larvae were used: heavily infected mice (20 mice infected with 300 larvae) and lightly infected mice (20 mice infected with 100 larvae) and 10 normal mice as control. The CAg was detectable as early as 4 days post infection (dpi) in the sera from both groups of infected mice, then increased rapidly, reached a peak with detection rate of 100% in heavily infected mice at 10 dpi and 80% in lightly infected mice at 22 dpi, respectively. The anti-Trichinella IgM antibodies was first detected in 40% of heavily infected mice and 20% of lightly infected mice at 8 dpi, and reached a peak positive rate of 100% in heavily infected mice at 16 dpi and in lightly infected mice at 26 dpi, respectively. The novel assay appears to be sensitive for detection of antigens of T. spiralis and valuable to the early diagnosis of trichinellosis.

Previous exposure to a low infectious dose of Leishmania major exacerbates infection with Leishmania infantum in the susceptible BALB/c mouse

The geographic distribution of Leishmania major overlaps with several other species of Leishmania. This study seeks to examine what effect previous exposure to L. major has on the outcome of infection with Leishmania infantum, the agent of virulent visceral leishmaniasis. The L. major immune response is well characterized by a strong Th1 response leading to resolution and protection against subsequent re-infection. A contrasting Th2 immune response leads to disseminated disease, while the role Th17 cytokines may play in Leishmania infection is still being explored. The cytokine profile, antibody titer, and parasite burden were evaluated in the susceptible BALB/c mouse after L. infantum infection in either naïve mice or those previously infected with a low/self-healing dose of L. major. Only IL-4 expression in mice previously exposed to L. major was found to be significantly increased over controls, a cytokine with an ambiguous role in L. infantum infection. However, disease exacerbation, with a notably higher parasite burden, was observed in the L. major exposed mice compared to the L. infantum only. Cross-reactive antibodies were seen in both groups of infected mice regardless of their immune history. Studies have shown a role for opsonizing antibodies leading to increased disease in visceral leishmaniasis. We speculate that cross-reactive antibodies may be playing a role in augmenting visceral disease in mice with immunological memory to L. major.

Evaluación de la técnica PCR anidada para el diagnóstico de la esporotricosis experimental

BackgroundSporotrichosis caused by the dimorphic fungus Sporothrix schenckii can presents in a variety of clinical forms. Routine diagnosis is made by mycology and serology studies. Few investigations have been focused on the evaluation of the molecular diagnosis. AimTo determine the value of the nested PCR technique for the diagnosis of experimental sporotrichosis in organs of mice, and to compare the results with the established laboratory diagnostic procedures. MethodsBALB/c mice were inoculated with growing concentrations of the 2 morphological phases of the fungus. The infected animals were sacrificed one month later and specimens from liver, spleen, lung and testicle were obtained to perform wet mount, culture and molecular diagnosis by the nested PCR technique. Blood samples were obtained for determination of specific antibodies against S. schenckii by the double immunodiffusion procedure. ResultsThe pathogenicity observed with the different concentrations of the fungus inoculated and its isolation by culture, showed scarce differences in the study of specimens from organs infected with the 2 morphological phases of S. schenckii. Specimens from organs of mice inoculated with the mycelial phase when studied by wet mount and culture, showed a higher positivity (100 and 37.5%) than those from mice inoculated with the yeast phase (73 and 2%). However, diagnosis by the nested PCR molecular technique applied to the latter specimens showed a higher percentage of positivity (75%) and 43% of positive results coming from animals infected with the mycelial phase. Specific antibody detection was positive in 100% all groups of infected mice. ConclusionsIn the study of experimental sporotrichosis in mice, the culture, as well as the antibody detection, was an effective diagnostic procedure, while the nested PCR and microscopic studies had a lower diagnostic value.

Leishmania major: Activity of tamoxifen against experimental cutaneous leishmaniasis

Leishmaniasis is a family of diseases caused by protozoan parasites of the genus Leishmania. Various Leishmania species can cause human infection, producing a spectrum of clinical manifestations. The current treatments are unsatisfactory, and in absence of a vaccine, there is an urgent need for effective drugs to replace/supplement those currently in use. Recent studies have shown that the antineoplastic drug, tamoxifen, had direct leishmanicidal effect on several Leishmania species in vitro. Moreover, in vivo testing was carried out on some of the species and showed promising results. The authors have carried out the present work to complement previous published studies by investigating in vivo activity of tamoxifen in an experimental model of cutaneous leishmaniasis (CL) caused by Leishmania major. Groups of infected mice were given tamoxifen, orally, at a dose of 20mg/kg/day for 15days. Efficacy was assessed clinically, parasitologically, histopathologically by light and transmission electron microscope (TEM). Results showed that untreated infected mice suffered from autoamputation of the inoculated foot pad. However, those which received tamoxifen showed marked improvement of the cutaneous lesions and reduction of parasite burden. TEM of the cutaneous lesions from infected mice revealed the fine structure of normal Leishmania amastigotes, whereas those from infected mice treated with tamoxifen showed considerable changes. All male mice that received tamoxifen showed scrotal swelling with evident histopathological changes in the testes that could seriously compromise fertility of male mice. In conclusion, although tamoxifen causes significant side effects to the male reproductive system in the mouse model, it could provide an alternative to current agents. Results of this study demonstrated in vivo activity of tamoxifen against Leishmania major, thus, suggesting that tamoxifen is a suitable lead for the synthesis of more effective and less toxic antileishmanial derivatives.

Effect of 1918 PB1-F2 Expression on Influenza A Virus Infection Kinetics

Relatively little is known about the viral factors contributing to the lethality of the 1918 pandemic, although its unparalleled virulence was likely due in part to the newly discovered PB1-F2 protein. This protein, while unnecessary for replication, increases apoptosis in monocytes, alters viral polymerase activity in vitro, enhances inflammation and increases secondary pneumonia in vivo. However, the effects the PB1-F2 protein have in vivo remain unclear. To address the mechanisms involved, we intranasally infected groups of mice with either influenza A virus PR8 or a genetically engineered virus that expresses the 1918 PB1-F2 protein on a PR8 background, PR8-PB1-F2(1918). Mice inoculated with PR8 had viral concentrations peaking at 72 hours, while those infected with PR8-PB1-F2(1918) reached peak concentrations earlier, 48 hours. Mice given PR8-PB1-F2(1918) also showed a faster decline in viral loads. We fit a mathematical model to these data to estimate parameter values. The model supports a higher viral production rate per cell and a higher infected cell death rate with the PR8-PB1-F2(1918) virus. We discuss the implications these mechanisms have during an infection with a virus expressing a virulent PB1-F2 on the possibility of a pandemic and on the importance of antiviral treatments.

Evaluation of the in vivo activity of different concentrations of <i>Clerodendrum umbellatum</i> poir against <i>Schistosoma mansoni</i> infection in mice

Clerodendrum umbellatum Poir (Verbenaceae) is traditionally used in Cameroon for the treatment of many diseases including intestinal helminthiasis. This study was undertaken to assess the in vivo antischistosomal activity of its leaves aqueous extract on a Schistosoma mansoni mice model and to determine the most effective dose of this extract. Mice showing a patent infection of S. mansoni were daily treated with C. umbellatum leaves aqueous extract at the doses of 40, 80 or 160 mg/kg body weight for 14 days. Seven days after administration of the extract, schistosomicidal activity was evaluated on the liver and spleen weights, faecal eggs releasing, liver egg count and worm burden. Treatment using C. umbellatum leaves aqueous extract resulted in an important reduction in faecal egg output by 75.49% and 85.14% for 80 mg/kg and 160 mg/kg of the extract respectively. These reduction rates did not differ significantly from the 100% obtained in the group of infected mice treated with 100 mg/kg of praziquantel. C. umbellatum leaves aqueous extract was lethal to S. mansoni worm. A 100% reduction rate was recorded in the group of infected mice treated with 160 mg/kg of the extract, as well as in praziquantel-treated mice. An amelioration of the hepatosplenomegaly was noticed in both the extract-treated mice and the praziquantel-treated mice. From these results, we can conclude that C. umbellatum leaves aqueous extract demonstrated schistosomicidal properties in S. mansoni model at doses of at least 80 mg/kg body weight.

Long-Lasting Protective Antiviral Immunity Induced by Passive Immunotherapies Requires both Neutralizing and Effector Functions of the Administered Monoclonal Antibody

Using FrCas(E) retrovirus-infected newborn mice as a model system, we have shown recently that a long-lasting antiviral immune response essential for healthy survival emerges after a short treatment with a neutralizing (667) IgG2a isotype monoclonal antibody (MAb). This suggested that the mobilization of adaptive immunity by administered MAbs is key for the success in the long term for the MAb-based passive immunotherapy of chronic viral infections. We have addressed here whether the anti-FrCas(E) protective endogenous immunity is the mere consequence of viral propagation blunting, which would simply give time to the immune system to react, and/or to actual immunomodulation by the MAb during the treatment. To this aim, we have compared viral replication, disease progression, and antiviral immune responses between different groups of infected mice: (i) mice treated with either the 667 MAb, its F(ab')(2) fragment, or an IgM (672) with epitopic specificity similar to that of 667 but displaying different effector functions, and (ii) mice receiving no treatment but infected with a low viral inoculum reproducing the initial viral expansion observed in their infected/667 MAb-treated counterparts. Our data show that the reduction of FrCas(E) propagation is insufficient on its own to induce protective immunity and support a direct immunomodulatory action of the 667 MAb. Interestingly, they also point to sequential actions of the administered MAb. In a first step, viral propagation is exclusively controlled by 667 neutralizing activity, and in a second one, this action is complemented by FcgammaR-binding-dependent mechanisms, which most likely combine infected cell cytolysis and the modulation of the antiviral endogenous immune response. Such complementary effects of administered MAbs must be taken into consideration for the improvement of future antiviral MAb-based immunotherapies.

A Proposed Mouse Model to Study Male Infertility Provoked by Genital Serovar E, Chlamydia trachomatis

Chlamydia trachomatis is a common sexually transmitted pathogen. The impact of chlamydial infection on male infertility is controversial. The aim of this study was to assess the role of C trachomatis human genital serovar E on sperm function, induction of apoptosis in spermatozoa, and reproductive performance, using the Swiss male mice model. Fertile mice were inoculated in the meatus urethra with 10(6) C trachomatis inclusion-forming units at day 0. The studied parameters were evaluated 7, 15, 21, and 30 days postinoculation (pi) in infected and sham-infected controls. Semen parameters of the infected mice groups were significantly lower than those of the control groups at the different days pi. DNA fragmentation study indicated that the mean percentages of apoptotic spermatozoa in the infected mice groups were significantly higher than those in the control groups 7 and 15 days pi, whereas the mean percentages of necrotic spermatozoa in the infected mice groups were significantly higher than those in the control group on the 30th day pi. A decrease in reproductive performance was observed at different days pi in infected male mice groups when compared to the control groups. Furthermore, a statistically significant decrease in the mean number of infant mice was observed at 21 and 30 days pi. In conclusion, our data showed that inoculation of fertile male Swiss mice in the meatus urethra with C trachomatis could lead to alteration of semen parameters, induction of apoptosis in spermatozoa, and decrease of the reproductive performance of male mice.

Quorum sensing is necessary for the virulence of Pseudomonas aeruginosa during urinary tract infection

Quorum sensing is a signaling pathway used by bacteria to monitor their population density by detecting small diffusible molecules. To understand the role of quorum sensing in pathogenesis of urinary tract infections, wild type Pseudomonas aeruginosa, having both functional las and rhl quorum sensing systems, and its isogenic single and double mutants were used in a mouse model of ascending urinary tract infection. Mice were evaluated on the basis of bacteriological and histopathological examinations, detection of acyl homoserine lactone, and the pathologic index factors of renal and bladder tissue. Single as well as double mutant strains were able to reach renal tissue, but they were not able to multiply and cause tissue damage. Reduced rates of infection, mild histopathologic lesions, and decreased production of pathologic index factors like myeloperoxidase, malondialdehyde, and reactive nitrogen intermediates were found in these groups of mice as compared to mice infected with a standard strain (PAO1) possessing both functional sensing systems. Loss of any one of the quorum-sensing components significantly reduced the in vivo virulence of P. aeruginosa in this mouse model of ascending urinary tract infection. Our results suggests that quorum-sensing signals may act as virulence factors and are essential for P. aeruginosa multiplication and virulence during the course of urinary tract infection.

Gamma scintigraphy imaging of murine invasive pulmonary aspergillosis with a 111In-labeled cyclic peptide

Invasive pulmonary aspergillosis (IPA) is a leading cause of infection-associated death in immunosuppressed patients. Early detection and early administration of antifungal therapy are critical factors in improving outcome for patients with IPA. Here, we evaluated the imaging properties of a (111)In-labeled cyclic peptide targeted to Aspergillus fumigatus in an immunosuppressed murine model of IPA. A cyclic peptide c(CGGRLGPFC)-NH(2) was labeled with (111)In by means of diethylenetriaminepentaacetic acid (DTPA). Two days after intranasal inoculation of 17.5x10(6) conidia of A. fumigatus, mice were injected (111)In-DTPA-c(CGGRLGPFC)-NH(2) intravenously. Biodistribution data were obtained at 2 h, and gamma-images were acquired at 10 min and 2 h after radiotracer injection. Healthy mice were used as controls. In addition, a group of infected mice were co-injected with the radiotracer and unlabeled c(CGGRLGPFC)-NH(2) to evaluate the inhibition of radiotracer's binding to infected lungs. Autoradiographs of lungs from infected and healthy mice were compared with corresponding photographs of transaxial sections of the lung tissues stained for A. fumigatus hyphae. The labeling efficiency was >98%, with specific radioactivity of up to 74 MBq/nmol peptide. Significantly higher uptake of (111)In-DTPA-c(CGGRLGPFC)-NH(2) was observed in the lungs of mice infected with A. fumigatus than in those of healthy mice (0.37+/-0.06 %ID/g vs. 0.14+/-0.02 %ID/g, P=.00044). Simultaneous injection with unlabeled peptide reduced radioactivity in the infected lungs by 41% (P=.0037). Increased radioactivity in the lungs of infected mice was visible in gamma images at both 10 min and 2 h after radiotracer injection. Moreover, autoradiography confirmed radiotracer uptake in infected lungs, but not in the lungs of healthy mice or infected mice co-injected with unlabeled peptide. Gamma-imaging with (111)In-DTPA-c(CGGRLGPFC)-NH(2) clearly delineated experimental IPA in mice. Peptides directly targeting fungi therefore may be valuable agents for noninvasive detection of opportunistic mycoses.

Local and Systemic Responses in Matrix Metalloproteinase 8-Deficient Mice duringPorphyromonas gingivalis-Induced Periodontitis

Periodontitis is a bacterium-induced chronic inflammation that destroys tissues that attach teeth to jaw bone. Pathologically excessive matrix metalloproteinase 8 (MMP-8) is among the key players in periodontal destruction by initiating type I collagen degradation. We studied MMP-8 in Porphyromonas gingivalis-induced periodontitis by using MMP-8-deficient (MMP8(-/-)) and wild-type (WT) mice. Alveolar bone loss, inflammatory mediator expression, serum immunoglobulin, and lipoprotein responses were investigated to clarify the role of MMP-8 in periodontitis and systemic inflammatory responses. P. gingivalis infection induced accelerated site-specific alveolar bone loss in both MMP8(-/-) and WT mice relative to uninfected mice. The most extensive bone degradation took place in the P. gingivalis-infected MMP8(-/-) group. Surprisingly, MMP-8 significantly attenuated (P < 0.05) P. gingivalis-induced site-specific alveolar bone loss. Increased alveolar bone loss in P. gingivalis-infected MMP8(-/-) and WT mice was associated with increase in gingival neutrophil elastase production. Serum lipoprotein analysis demonstrated changes in the distribution of high-density lipoprotein (HDL) and very-low-density lipoprotein (VLDL) particles; unlike the WT mice, the MMP8(-/-) mice underwent a shift toward a smaller HDL/VLDL particle sizes. P. gingivalis infection increased the HDL/VLDL particle size in the MMP8(-/-) mice, which is an indicator of lipoprotein responses during systemic inflammation. Serum total lipopolysaccharide activity and the immunoglobulin G-class antibody level in response to P. gingivalis were significantly elevated in both infected mice groups. Thus, MMP-8 appears to act in a protective manner inhibiting the development of bacterium-induced periodontal tissue destruction, possibly through the processing anti-inflammatory cytokines and chemokines. Bacterium-induced periodontitis, especially in MMP8(-/-) mice, is associated with systemic inflammatory and lipoprotein changes that are likely involved in early atherosclerosis.

Schistosomacidal activity of &lt;i&gt;Maytenus senegalensis&lt;/i&gt; (Lam.) Excell. (Celastraceae) extracts on Schistosoma mansoni in mice

A study was conducted to investigate the schistosomacidal effect of Maytenus senegalensis (Lam.) Excell. on Schistosoma mansoni in mice. Three different concentrations (6.0, 3.0 and 1.5) mg/ml of the aqueous and ethanolic extracts of the plant roots was given orally to different groups of infected mice. Praziquantel was used as standard drug. Parameters investigated include the spleen weight, liver weight, liver score, worm burden, haemoglobin (Hb) and packed cell volume (pcv). Results showed schitosomacidal effects as evidenced by decreases in spleen and liver weights, reduction in worm burden as well as increases in Hb and PCV values of treated mice compared to those of the untreated group. Activity of plant is also shown to be directly proportional to the concentration in both aqueous and ethanolic extracts. Statistical analysis shows that there is a significant difference (p

Fas Ligand-Dependent Inflammatory Regulation in Acute Myocarditis Induced by Trypanosoma cruzi Infection

Fas/Fas ligand (Fas-L) engagement, a potent inducer of apoptosis, is also important for cellular activation, regulation of effector and chemotactic activity, and secretion of chemokines and cytokines. We evaluated the relevance of Fas/Fas-L in the regulation of myocarditis induced by Trypanosoma cruzi infection and observed that in Fas-L(-/-) mice (gld/gld), cardiac infiltration was significantly reduced, accordingly showing less cardiomyocyte destruction. Fluorescence-activated cell sorting analysis of cardiac inflammatory cells showed higher numbers of CD8(+) T cells in BALB/c compared with gld/gld mice but similar levels of lymphocyte function-associated antigen-1, intercellular adhesion molecule, CD2, and CD69 expression; MAC-1(+) myeloid cells and mast cells were increased in BALB/c mice, whereas gld/gld mice exhibited an enrichment of CD4(+/low) T cells. Intracellular labeling of cytokines revealed no clear cardiac skewing of Th1 or Th2 responses, but we found a higher number of interleukin-10(+) cells in gld/gld mice and a deficient expression of vascular cell adhesion molecule-1 on cardiac endothelial cells in gld/gld mice. Finally, we found a population of CD3(+) but CD4/CD8 double negative cardiac T cells in both groups of infected mice, but down-regulation of some adhesion molecules and surface receptors was only observed in gld/gld mice, indicating a targeted T-cell population mostly affected by the lack of Fas-L engagement. These results point to a role for myocarditis regulation by Fas/Fas-L beyond its possible direct relevance in cellular death.

Murine Malaria Infection Induces Fetal Loss Associated with Accumulation ofPlasmodium chabaudiAS-Infected Erythrocytes in the Placenta

Malarial infection in nonimmune women is a risk factor for pregnancy loss, but the role that maternal antimalarial immune responses play in fetal compromise is not clear. We conducted longitudinal and serial sacrifice studies to examine the pathogenesis of malaria during pregnancy using the Plasmodium chabaudi AS/C57BL/6 mouse model. Peak parasitemia following inoculation with 1,000 parasite-infected murine erythrocytes and survival were similar in infected pregnant and nonpregnant mice, although development of parasitemia and anemia was slightly accelerated in pregnant mice. Importantly, pregnant mice failed to maintain viable pregnancies, most aborting before day 12 of gestation. At abortion, maternal placental blood parasitemia was statistically significantly higher than peripheral parasitemia. Infected mice had similar increases in spleen size and cellularity which were statistically significantly higher than in uninfected mice. In contrast, splenocyte proliferation in response to mitogenic stimulation around peak parasitemia was statistically significantly reduced in both groups of infected mice compared to uninfected, nonpregnant mice, suggesting that lymphoproliferation is not a good indicator of the antimalarial immune responses in pregnant or nonpregnant animals. This study suggests that while pregnant and nonpregnant C57BL/6 mice are equally capable of mounting an effective immune response to and surviving P. chabaudi AS infection, pregnant mice cannot produce viable pups. Fetal loss appears to be associated with placental accumulation of infected erythrocytes. Further study is required to determine to what extent maternal antimalarial immune responses, anemia, and placental accumulation of parasites contribute to compromised pregnancy in this model.

Independent Protective Effects for Tumor Necrosis Factor and Lymphotoxin Alpha in the Host Response toListeria monocytogenesInfection

Although the essential role of tumor necrosis factor (TNF) in resistance to Listeria monocytogenes infection is well established, the roles of the related cytokines lymphotoxin alpha (LTalpha) and lymphotoxin beta (LTbeta) are unknown. Using C57BL/6 mice in which the genes for these cytokines were disrupted, we examined the contributions of TNF, LTalpha, and LTbeta in the host response to Listeria. To overcome the lack of peripheral lymph nodes in LTalpha(-/-) and LTbeta(-/-) mice, bone marrow chimeras were constructed. TNF(-/-) and LTalpha(-/-) chimeras that lacked both secreted LTalpha(3) and membrane-bound LTalpha(1)beta(2) and LTalpha(2)beta(1) were highly susceptible and succumbed 4.5 and 6 days, respectively, after a low-dose infection (200 CFU). LTbeta(-/-) chimeras, which lacked only membrane-bound LT, controlled the infection in a manner comparable to wild-type (WT) chimeras. The Listeria-specific proliferative and gamma interferon T-cell responses were equivalent in all five groups of infected mice (LTalpha(-/-) and LTbeta(-/-) chimeras, WT chimeras, and TNF(-/-) and WT mice). TNF(-/-) mice and LTalpha(-/-) chimeras, however, failed to generate the discrete foci of lymphocytes and macrophages that are essential for bacterial elimination. Rather, aberrant necrotic lesions comprised predominantly of neutrophils with relatively few lymphocytes and macrophages were observed in the livers and spleens of TNF(-/-) and LTalpha(-/-) chimeras. Therefore, in addition to TNF, soluble LTalpha(3) plays a separate essential role in control of listerial infection through control of leukocyte accumulation and organization in infected organs.

Reinfection with Anaplasma phagocytophilum in BALB/c mice and cross-protection between two sympatric isolates.

Infection with Anaplasma phagocytophilum in white-footed mice results in partial protection against reinfection with the same agent. However, humans and domestic animals may be sequentially exposed to different isolates of the agent circulating in the same or adjacent foci. We investigated whether immune response to a tick-borne infection with A. phagocytophilum provides protection against homologous and heterologous challenges. BALB/c mice were infected with one of the two sympatric isolates of A. phagocytophilum via tick bite and challenged 16 weeks later by Ixodes scapularis nymphs infected with either the same or the alternative isolate. As controls, groups of infected mice were challenged by uninfected ticks to confirm an absence of reactivation of the original infection or groups of naive mice were fed upon by ticks from cohorts used for an infectious challenge. Xenodiagnostic I. scapularis larvae were fed upon each mouse at 14 and 21 days postchallenge (PCH) and tested for the presence of A. phagocytophilum as freshly molted nymphs. Blood samples for quantitative PCR were collected at 7, 14, 21, and 70 days PCH. Serum samples were collected weekly to monitor development of immune response. The proportion of infected animals, levels of bacteremia, and the prevalence of infection in xenodiagnostic ticks were higher in groups of control mice exposed to A. phagocytophilum for the first time than in mice reinfected with either homologous or heterologous isolates. The presence of antibodies against A. phagocytophilum did not protect mice from a challenge with either homologous or heterologous isolates, however the ensuing reinfection was significantly milder and of a shorter duration than the first infection with either isolate.

Matrix metalloproteinase-2 and -9 expression increases in Mycoplasma-infected airways but is not required for microvascular remodeling.

Murine Mycoplasma pulmonis infection induces chronic lung and airway inflammation accompanied by profound and persistent microvascular remodeling in tracheobronchial mucosa. Because matrix metalloproteinase (MMP)-2 and -9 are important for angiogenesis associated with placental and long bone development and skin cancer, we hypothesized that they contribute to microvascular remodeling in airways infected with M. pulmonis. To test this hypothesis, we compared microvascular changes in airways after M. pulmonis infection of wild-type FVB/N mice with those of MMP-9(-/-) and MMP-2(-/-)/MMP-9(-/-) double-null mice and mice treated with the broad-spectrum MMP inhibitor AG3340 (Prinomastat). Using zymography and immunohistochemistry, we find that MMP-2 and MMP-9 rise strikingly in lungs and airways of infected wild-type FVB/N and C57BL/6 mice, with no zymographic activity or immunoreactivity in MMP-2(-/-)/MMP-9(-/-) animals. However, microvascular remodeling as assessed by Lycopersicon esculentum lectin staining of whole-mounted tracheae is as severe in infected MMP-9(-/-), MMP-2(-/-)/MMP-9(-/-) and AG3340-treated mice as in wild-type mice. Furthermore, all groups of infected mice develop similar inflammatory infiltrates and exhibit similar overall disease severity as indicated by decrease in body weight and increase in lung weight. Uninfected wild-type tracheae show negligible MMP-2 immunoreactivity, with scant MMP-9 immunoreactivity in and around growing cartilage. By contrast, MMP-2 appears in epithelial cells of infected, wild-type tracheae, and MMP-9 localizes to a large population of infiltrating leukocytes. We conclude that despite major increases in expression, MMP-2 and MMP-9 are not essential for microvascular remodeling in M. pulmonis-induced chronic airway inflammation.

On the increase of portal pressure during the acute and chronic phases of murine schistosomiasis mansoni and its reversibility after treatment with oxamniquine

The purpose of the present study was to evaluate the effect of treatment with oxamniquine on the portal pressure of mice infected with Schistosoma mansoni. The animals were infected with 30 cercariae and portal pressure was measured with a polygraph at 70 (acute phase) and 160 (chronic phase) days after infection. On days 70 and 160 two other groups of infected mice were treated with 400 mg/kg of oxamniquine and portal pressure was measured 90 days later (160 and 250 days after infection). A group of uninfected mice was used as control. The measured portal pressures, in mmHg, were: matched uninfected control mice 8.7±2.1 and acute phase group, measured at day 70, 13.4±3.5. Matched uninfected control 7.5±0.6 and chronic phase group, measured at day 160 post-infection, 11.6±1.5. Matched uninfected mice 6.9±0.9 and chronic phase group, measured at day 250, 10.4±1.8. Oxamniquine-treated at day 70 and measured at day 160 7.9±0.4; oxamniquine-treated at day 160 and measured at day 250, 7.6±1.7. The infection of mice with 30 cercariae of S. mansoni induced portal hypertension, both during the acute and chronic phases and treatment with oxamniquine caused portal pressure to return to normal levels.