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Previous studies comparing interleukin 4 receptor α (IL-4Rα)(-/-) and interleukin 4 (IL-4)(-/-) BALB/c mice have indicated that interleukin 13 (IL-13), whose receptor shares the IL-4Rα subunit with IL-4, plays a protective role during visceral leishmaniasis. We demonstrate that IL-13(-/-) BALB/c mice were less able to control hepatic growth of Leishmania donovani compared with wild-type mice. This correlated with significantly retarded granuloma maturation in IL-13(-/-) mice, defective interferon γ (IFN-γ) production, and elevated IL-4 and interleukin 10 (IL-10) levels. L. donovani-infected IL-13(-/-) mice also responded poorly to sodium stibogluconate-mediated chemotherapy compared with wild-type BALB/c mice. Because murine lymphocytes do not have IL-13 receptors, we examined the ability of macrophage/neutrophil-specific IL-4Rα(-/-) mice to control primary infection with L. donovani and to respond to chemotherapy. Macrophage/neutrophil-specific IL-4Rα(-/-) mice were as resistant to leishmaniasis as wild-type mice, and chemotherapy retained its efficacy. Consequently, in L. donovani infected BALB/c mice, IL-13 promotes hepatic granuloma formation and controls parasite burdens independently of direct effects on macrophages/neutrophils. [ABSTRACT FROM AUTHOR]

Interleukin (IL)-4 and IL-13 are key factors in the pathogenesis of bronchopulmonary mycosis induced in mice by infection with Cryptococcus neoformans. Both cytokines use the IL-4 receptor alpha-chain (IL-4Ralpha). In this study, we investigated the role played by IL-4Ralpha expression in susceptibility to pulmonary C. neoformans infection. IL-4Ralpha-/- mice were extremely resistant. To characterize the effect of IL-4Ralpha expression level on disease outcome, we generated IL-4Ralpha+/- first-generation (F1) mice. IL-4Ralpha+/- mice showed intermediate levels of IL-4Ralpha expression, in contrast to higher levels in wild-type mice and no expression in IL-4Ralpha-/- mice, indicating biallelic expression of the gene for IL-4Ralpha (Il4ra). Concomitant with intermediate IL-4Ralpha expression, F1 mice showed intermediate susceptibility associated with altered Th2/Th17 cytokine production, decreased immunoglobulin E levels, and reduced allergic inflammation. This indicates a gene-dosage effect of IL-4Ralpha expression on susceptibility to bronchopulmonary mycosis. These data provide the basis for novel therapies antagonizing IL-4Ralpha in Th2-related pulmonary infection and possibly also in asthma. Copyright © 2008 Infectious Diseases Society of America [ABSTRACT FROM AUTHOR]

African trypanosomiasis encompasses diseases caused by pathogenic trypanosomes, infecting both humans and animals. In the present article, we dissected the possible role of members of the interleukin (IL)-12 family during infection with Trypanosoma brucei brucei and Trypanosoma evansi in mice. IL-12p35(-/-), IL-12p40(-/-), and IL-12p35(-/-)/p40(-/-) mice were susceptible to both pathogens, as was demonstrated by the increased mortality among these mice, compared with wild-type C57BL/6 mice. The different IL-12p70(-/-) mouse strains showed similar mortality kinetics, suggesting that IL-12p70--but not the IL-12p80 homodimer or IL-23--plays a crucial role in survival. Although there were similar plasma levels of immunoglobulin (Ig) M and IgG2a in IL-12-deficient mice and wild-type mice, interferon (IFN)- gamma production, especially during early infection, was severely impaired in all IL-12p70(-/-) mouse strains, demonstrating an IL-12p70-dependent mechanism for IFN- gamma production. Because IFN- gamma receptor-deficient mice (IFN- gamma R(-/-)) were also highly susceptible to both Trypanosoma species, IL-12p70-dependent IFN- gamma production seems to be the important mechanism involved in resistance against both pathogens. Copyright © 2007 Infectious Diseases Society of America [ABSTRACT FROM AUTHOR]

Background: Interleukin 4 (IL-4i1)-induced gene 1 encodes L-phenylalanine oxidase that catabolizes phenylalanine into phenylpyruvate. IL-4i1 is mainly expressed by antigen-presenting cells (APCs), inhibits T-cell proliferation, regulates B-cell activation, modulates T cell responses, and drives macrophage polarization, but its role in bacterial infections is understudied., Methods: We evaluated IL-4i1 deletion in macrophages and mice on infection with virulent H37Rv and W-Beijing lineage hypervirulent HN878 Mycobacterium tuberculosis (Mtb) strains. The bacterial growth and proinflammatory responses were measured in vitro and in vivo. Histopathological analysis, lung immune cell recruitment, and macrophage activation were assessed at the early and chronic stages of Mtb infection., Results: IL-4i1-deficient (IL-4i1-/-) mice displayed increased protection against acute H37Rv, HN878 and chronic HN878 Mt infections, with reduced lung bacterial burdens and altered APC responses compared with wild-type mice. Moreover, "M1-like" interstitial macrophage numbers, and nitrite and Interferon-γ production were significantly increased in IL-4i1-/- mice compared with wild-type mice during acute Mtb HN878 infection., Conclusions: Together, these data suggest that IL-4i1 regulates APC-mediated inflammatory responses during acute and chronic Mtb infection. Hence, IL-4i1 targeting has potential as an immunomodulatory target for host-directed therapy., (© The Author(s) 2021. Published by Oxford University Press for the Infectious Diseases Society of America.)

Background: Statins are cholesterol-lowering drugs, targeting HMG-CoA reductase, thereby reducing the risk of coronary disorders and hypercholesterolemia. However, they also can influence immunologic responses., Methods: Peripheral blood mononuclear cells (PBMCs) and monocyte-derived macrophages (MDMs) were isolated from patients with familial hypercholesterolemia (FH) during statin therapy. After infection of cells with Mycobacterium tuberculosis, bacterial burden was determined. In vivo, mice were treated with statins before aerosol-based infection with M. tuberculosis and were monitored for disease progression., Results: PBMCs and MDMs from patients with FH receiving statin therapy were more resistant to M. tuberculosis infection, with reduced bacterial burdens, compared with those of healthy donors. Moreover, statin treatment in experimental murine M. tuberculosis infection studies increased host protection, with reduced lung burdens and improved histopathologic findings. Mechanistically, metabolic rescue experiments demonstrated that statins reduce membrane cholesterol levels, particularly by the mevalonate-isoprenoid arm of the sterol pathway. This promoted phagosomal maturation (EEA-1/Lamp-3) and autophagy (LC3-II), as shown by confocal microscopy and Western blot in macrophages. In addition, inhibitors of phagosome and autophagosome maturation reversed the beneficial effect of statins on bacterial growth., Conclusion: These results suggest that statin-mediated reduction in cholesterol levels within phagosomal membranes counteract M. tuberculosis-induced inhibition of phagosomal maturation and promote host-induced autophagy, thereby augmenting host protection against tuberculosis.

To determine the immunological role played by interleukin (IL)-12 family members in Trypanosoma congolense infection, IL-12p35(-/-), IL-12p40(-/-), and IL-12p35(-/-)/p40(-/-) mice were used. While the latter 2 strains lack all IL-12 homologues, IL-12p35(-/-) mice still produce IL-12p80 homodimers and IL-23. Compared with wild-type mice, all infected IL-12-deficient mouse strains showed prolonged survival, whereas parasitemia levels were unaltered. Interferon (IFN)-gamma production in IL-12-deficient mice was strikingly reduced during the acute and chronic stages of infection, coinciding with significantly reduced chronic-stage hepatocellular damage, as demonstrated by histological analysis and plasma aspartate transaminase measurements. In contrast, IL-10 production was not affected by the absence of IL-12. Taken together, these results show that, during T. congolense infection, the absence of IL-12, but not the IL-12p80 homodimer or IL-23, leads to a reduction in IFN-gamma production, which reduces hepatic pathology and improves host survival in conjunction with IL-10 without negatively affecting parasitemia control.

African trypanosomiasis encompasses diseases caused by pathogenic trypanosomes, infecting both humans and animals. In the present article, we dissected the possible role of members of the interleukin (IL)-12 family during infection with Trypanosoma brucei brucei and Trypanosoma evansi in mice. IL-12p35(-/-), IL-12p40(-/-), and IL-12p35(-/-)/p40(-/-) mice were susceptible to both pathogens, as was demonstrated by the increased mortality among these mice, compared with wild-type C57BL/6 mice. The different IL-12p70(-/-) mouse strains showed similar mortality kinetics, suggesting that IL-12p70--but not the IL-12p80 homodimer or IL-23--plays a crucial role in survival. Although there were similar plasma levels of immunoglobulin (Ig) M and IgG2a in IL-12-deficient mice and wild-type mice, interferon (IFN)- gamma production, especially during early infection, was severely impaired in all IL-12p70(-/-) mouse strains, demonstrating an IL-12p70-dependent mechanism for IFN- gamma production. Because IFN- gamma receptor-deficient mice (IFN- gamma R(-/-)) were also highly susceptible to both Trypanosoma species, IL-12p70-dependent IFN- gamma production seems to be the important mechanism involved in resistance against both pathogens.

Control of Trypanosoma congolense infections requires an early cell-mediated immune response. To unravel the role of tumor necrosis factor (TNF) in this process, 6 different T. congolense strains were used in 6 different gene-deficient mouse models that included TNF(-/-), TNF receptor-1 (TNFp55)(-/-), and TNF receptor-2 (TNFp75)(-/-) mice, 2 cell type-specific TNF(-/-) mice, as well as TNF-knock-in mice that expressed only membrane-bound TNF. Our results indicate that soluble TNF produced by macrophages/neutrophils and TNFp55 signaling are essential and sufficient to control parasitemia. The downstream mechanism in the control of T. congolense infection depends on inducible nitric oxide synthase activation in the liver. Such a role for nitric oxide is corroborated ex vivo, because the inhibitor N(G)-monomethyl-l-arginine blocks the trypanolytic activity of the adherent liver cell population, whereas exogenous interferon- gamma that stimulates nitric oxide production enhances parasite killing. In conclusion, the control of T. congolense infection depends on macrophage/neutrophil-derived soluble TNF and intact TNFp55 signaling, which induces trypanolytic nitric oxide.

Very recent reports have documented that Trypanosoma evansi, the etiological agent of the livestock disease "surra," can cause human trypanosomiasis. In contrast to trypanosomes causing human African trypanosomiasis, T. evansi has a wide geographic distribution and host range, yet information about the immunobiological aspects of T. evansi trypanosomiasis is limited. Here, we show that, although T. evansi causes the induction of tumor necrosis factor (TNF), interferon-gamma, and nitric oxide during the early stage of infection, none of these molecules are crucial for parasitemia control and survival of the infected animal. However, TNF and TNF receptor 2 affect the induction of late-stage anemia. Using B cell- and immunoglobulin M (IgM)-deficient mice, we identified IgM as being crucial for parasitemia control and host survival. Collectively, our results show that, compared with other trypanosomes, T. evansi displays a distinct host-parasite interaction profile, give that, despite an infection-associated induction of proinflammatory molecules, only IgM antibodies contribute significantly to parasite control.

The control of chronic Trypanosoma congolense trypanosomiasis was analyzed using several gene-deficient mouse strains. First, interferon (IFN)-gamma receptor (IFN-gamma-R)-deficient mice were used to show that IFN- gamma -mediated immune activation is crucial for parasitemia control. Second, infections in major histocompatibility complex (MHC) class II-deficient mice indicate that this molecule is needed for initiation of IFN- gamma and subsequent tumor necrosis factor (TNF) production. Downstream of IFN-gamma-R signaling, inducible NO synthase (iNOS)-dependent trypanosome killing occurs, as is shown by the hypersusceptible phenotype of iNOS-deficient mice. Besides proinflammatory responses, B cells and, more specifically, immunoglobulin (Ig) G antibodies are crucial for parasite killing. Hence, parasitemia control is abolished in B cell-deficient mice, whereas IgM-deficient mice control the infection as efficiently as do wild-type mice. In addition, splenectomized mice that have a normal IgM response but an impaired IgG2a/3 response fail to control T. congolense infection. Collectively, these results suggest that host protective immunity against T. congolense is critically dependent on the combined action of the proinflammatory mediators/effectors IFN- gamma , TNF, and NO and antiparasite IgGs.

Immunity to Cryptosporidium parvum infection involves a T helper (Th) 1 response with interferon (IFN)- gamma and interleukin (IL)-12 activity, but the role of Th2 cytokines, such as IL-4, is unclear. Around the peak of infection, production of oocysts in IL-4-deficient and IL-4 receptor alpha -deficient neonatal BALB/c mice was greater than that in wild-type (wt) mice. Susceptibility to infection was increased or decreased, respectively, in wt mice treated with anti-IL-4 neutralizing antibodies or recombinant IL-4. Excretion of oocysts by IFN- gamma -deficient mice was unaffected by treatment with anti-IL-4, indicating that IL-4 stimulated IFN- gamma activity. Early during infection, wt mice had increased intestinal expression of IFN- gamma and IL-12 mRNA, compared with IL-4-deficient mice. Intestinal IL-4 was detected by Western blotting in wt mice 24 h after infection but not in uninfected control mice. These findings suggest that, early during C. parvum infection of BALB/c mice, there is production of IL-4 that promotes Th1-mediated immunity.

In experimental murine trypanosomiasis, resistance is often scored as the capacity to control peak parasitemia levels, which results in prolonged survival. Infection-induced pathology has not systematically been used as a resistance criterion. Because this parameter could be the most relevant for comparative analysis of natural and experimental infections, as well as for understanding of pathology-associated immune alterations, we analyzed Trypanosoma brucei infections in 4 different established conventional mouse models, as well as in tumor necrosis factor (TNF)-deficient and TNF-receptor-deficient mice. Results indicate the following: (1) there is no correlation between peak parasitemia control or survival and the induction of infection-associated anemia, loss of body weight, liver pathology, reduced locomotor activity, and general morbidity; (2) serum levels of TNF, interferon- gamma, and interleukin-10, which are known to affect survival, do not correlate with induction of pathology; and (3) infection-induced occurrence of lipopolysaccharide hypersensitivity does not correlate with survival. However, one parameter that was found to correlate with the inhibition of trypanosomiasis-associated pathology in all models was the shedding of soluble p75 TNF-receptor during peak parasitemia stages. These results are important for future cytokine and trypanosomiasis pathology studies, because the interplay between TNF and the soluble receptors it sheds has not been considered in either human clinical sleeping sickness studies or in veterinary trypanosomiasis research.