Gut Dysbiosis during Influenza Contributes to Pulmonary Pneumococcal Superinfection through Altered Short-Chain Fatty Acid Production

Secondary bacterial infections often complicate viral respiratory infections. We hypothesize that perturbation of the gut microbiota during influenza A virus (IAV) infection might favor respiratory bacterial superinfection. Sublethal infection with influenza transiently alters the composition and fermentative activity of the gut microbiota in mice. These changes are attributed in part to reduced food consumption. Fecal transfer experiments demonstrate that the IAV-conditioned microbiota compromises lung defenses against pneumococcal infection. In mechanistic terms, reduced production of the predominant short-chain fatty acid (SCFA) acetate affects the bactericidal activity of alveolar macrophages. Following treatment with acetate, mice colonized with the IAV-conditioned microbiota display reduced bacterial loads. In the context of influenza infection, acetate supplementation reduces, in a free fatty acid receptor 2 (FFAR2)-dependent manner, local and systemic bacterial loads. This translates into reduced lung pathology and improved survival rates of double-infected mice. Lastly, pharmacological activation of the SCFA receptor FFAR2 during influenza reduces bacterial superinfection.

Role of the parasite-derived prostaglandin D2 in the inhibition of epidermal Langerhans cell migration during schistosomiasis infection

Epidermal Langerhans cells (LCs) play a key role in immune defense mechanisms and in numerous immunological disorders. In this report, we show that percutaneous infection of C57BL/6 mice with the helminth parasite Schistosoma mansoni leads to the activation of LCs but, surprisingly, to their retention in the epidermis. Moreover, using an experimental model of LC migration induced by tumor necrosis factor (TNF)-α, we show that parasites transiently impair the departure of LCs from the epidermis and their subsequent accumulation as dendritic cells in the draining lymph nodes. The inhibitory effect is mediated by soluble lipophilic factors released by the parasites and not by host-derived antiinflammatory cytokines, such as interleukin-10. We find that prostaglandin (PG)D₂, but not the other major eicosanoids produced by the parasites, specifically impedes the TNF-α–triggered migration of LCs through the adenylate cyclase–coupled PGD₂ receptor (DP receptor). Moreover, the potent DP receptor antagonist BW A868C restores LC migration in infected mice. Finally, in a model of contact allergen-induced LC migration, we show that activation of the DP receptor not only inhibits LC emigration but also dramatically reduces the contact hypersensitivity responses after challenge. Taken together, we propose that the inhibition of LC migration could represent an additional stratagem for the schistosomes to escape the host immune system and that PGD₂ may play a key role in the control of cutaneous immune responses.

Beneficial metabolic effects of selected probiotics on diet-induced obesity and insulin resistance in mice are associated with improvement of dysbiotic gut microbiota

Alterations in gut microbiota composition and diversity were suggested to play a role in the development of obesity, a chronic subclinical inflammatory condition. We here evaluated the impact of oral consumption of a monostrain or multi-strain probiotic preparation in high-fat diet-induced obese mice. We observed a strain-specific effect and reported dissociation between the capacity of probiotics to dampen adipose tissue inflammation and to limit body weight gain. A multi-strain mixture was able to improve adiposity, insulin resistance and dyslipidemia through adipose tissue immune cell-remodelling, mainly affecting macrophages. At the gut level, the mixture modified the uptake of fatty acids and restored the expression level of the short-chain fatty acid receptor GPR43. These beneficial effects were associated with changes in the microbiota composition, such as the restoration of the abundance of Akkermansia muciniphila and Rikenellaceae and the decrease of other taxa like Lactobacillaceae. Using an in vitro gut model, we further showed that the probiotic mixture favours the production of butyrate and propionate. Our findings provide crucial clues for the design and use of more efficient probiotic preparations in obesity management and may bring new insights into the mechanisms by which host-microbe interactions govern such protective effects.

Immunization of mice and baboons with the recombinant Sm28GST affects both worm viability and fecundity after experimental infection with Schistosoma mansoni

A member of the glutathione S-transferase family, Sm28GST has previously demonstrated a good ability to protect rodents against experimental infection with Schistosoma mansoni. In order to evaluate its efficacy in a model closer to man, two different protocols of immunization with recombinant Sm28GST were tested on baboons in a large-scale trial. Three injections in the presence of aluminium hydroxide as adjuvant resulted in a significant 38% reduction in the adult worm burden together with a trend for a lower percentage of inflammatory tissue in the liver. Individual levels of protection, ranging from 0 to 80%, underlined the heterogeneity of the immune response to this purified molecule in outbred primates. On the other hand, two injections of Sm28GST in the presence of aluminium hydroxide and Bordetella pertussis reduced female schistosome fecundity by 33%, with a more pronounced effect (66%) on faecal egg output; there was also a trend, in this protocol, for decrease of the mean granuloma surface in the liver. Individual anti-Sm28GST IgG antibodies were apparently unrelated to levels of immunity, but there was partial evidence that cytophilic IgE might play a role in the immune mechanisms affecting worm viability, but not fecundity. In the mouse model, Sm28GST vaccination resulted in a lower hatching ability of tissue eggs recovered from immunized mice whereas passive transfer of specific anti-Sm28GST T-lymphocytes, one day before infection, significantly reduced the number of eggs in the liver of mice. We propose that different protocols of immunization with a recombinant molecule can impede Schistosoma mansoni worm viability and fecundity, but can also affect miracidium physiology, with important consequences for disease transmission and granuloma-derived pathology.

Impairment of dendritic cell functionality and steady-state number in obese mice

There is a finely tuned interplay between immune and neuroendocrine systems. Metabolic disturbances like obesity will have serious consequences on immunity both at the cellular and at the cytokine expression levels. Our in vivo results confirm the immune deficiency of ob/ob mice, leptin deficient and massively obese, characterized by a reduced Ag-specific T cell proliferation after keyhole limpet hemocyanin immunization. In this report, we show that dendritic cells (DCs), major APCs involved in T lymphocyte priming, are affected in obese mice. Both their function and their steady-state number are disturbed. We demonstrate that DCs from ob/ob mice are less potent in stimulation of allogenic T cells in vitro. This impaired functionality is not associated with altered expression of phenotypic markers but with the secretion of immunosuppressive cytokines such as TGF-beta. Moreover, we show increased in vivo steady-state number of epidermal DCs in ob/ob mice, which is not due to a migratory defect. The ob/ob mice are characterized by the absence of functional leptin, a key adipokine linking nutrition, metabolism, and immune functions. Interestingly, intradermal injection of leptin is able to restore epidermal DC number in obese mice. Thus, DCs might be directly sensitive to metabolic disturbances, providing a partial explanation of the immunodeficiency associated with obesity.

Therapeutic immunization against Helicobacter pylori infection in the absence of antibodies

Helicobacter pylori is an important human pathogen. Prophylactic immunization with bacterial antigen plus an adjuvant protects mice against challenge with live H. pylori. Surprisingly, it was found that immunizations of mice already infected with Helicobacter also influenced bacterial colonization. This concept of therapeutic immunization is a novel phenomenon. Because H. pylori lives in the lumen of the stomach, it was initially hypothesized that the protective mechanism would involve induction of secretory IgA. However, work with knockout mice has demonstrated that prophylactic immunization is equally effective in mice deficient in IgA and even in microMT mice lacking B lymphocytes. Currently nothing is known about therapeutic vaccination and the effect of immunizing a host with an ongoing ineffective immune response. To address this, we infected B-cell deficient, microMT mice with H. pylori and therapeutically immunized them four times in 3 weeks with bacterial sonicate and cholera toxin adjuvant. These immunizations significantly reduced colonization by H. pylori. The antibody- negative status of the microMT mice was confirmed by ELISA. Thus, therapeutic immunization stimulates an immune response, which reduces H. pylori infection via a mechanism that is antibody independent. How this is achieved remains to be determined, but may well involve a novel immune mechanism.

Tryptophan metabolism activation by indoleamine 2,3-dioxygenase in adipose tissue of obese women: an attempt to maintain immune homeostasis and vascular tone

Human obesity is characterized by chronic low-grade inflammation in white adipose tissue and is often associated with hypertension. The potential induction of indoleamine 2,3-dioxygenase-1 (IDO1), the rate-limiting enzyme in tryptophan/kynurenine degradation pathway, by proinflammatory cytokines, could be associated with these disorders but has remained unexplored in obesity. Using immunohistochemistry, we detected IDO1 expression in white adipose tissue of obese patients, and we focused on its contribution in the regulation of vascular tone and on its immunoregulatory effects. Concentrations of tryptophan and kynurenine were measured in sera of 36 obese and 15 lean women. The expression of IDO1 in corresponding omental and subcutaneous adipose tissues and liver was evaluated. Proinflammatory markers and T-cell subsets were analyzed in adipose tissue via the expression of CD14, IL-18, CD68, TNFα, CD3ε, FOXP3 [a regulatory T-cell (Treg) marker] and RORC (a Th17 marker). In obese subjects, the ratio of kynurenine to tryptophan, which reflects IDO1 activation, is higher than in lean subjects. Furthermore, IDO1 expression in both adipose tissues and liver is increased and is inversely correlated with arterial blood pressure. Inflammation is associated with a T-cell infiltration in obese adipose tissue, with predominance of Th17 in the omental compartment and of Treg in the subcutaneous depot. The Th17/Treg balance is decreased in subcutaneous fat and correlates with IDO1 activation. In contrast, in the omental compartment, despite IDO1 activation, the Th17/Treg balance control is impaired. Taken together, our results suggest that IDO1 activation represents a local compensatory mechanism to limit obesity-induced inflammation and hypertension.

Alteration of the gut microbiota following SARS-CoV-2 infection correlates with disease severity in hamsters

Mounting evidence suggests that the gut-to-lung axis is critical during respiratory viral infections. We herein hypothesized that disruption of gut homeostasis during severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection may associate with early disease outcomes. To address this question, we took advantage of the Syrian hamster model. Our data confirmed that this model recapitulates some hallmark features of the human disease in the lungs. We further showed that SARS-CoV-2 infection associated with mild intestinal inflammation, relative alteration in intestinal barrier property and liver inflammation and altered lipid metabolism. These changes occurred concomitantly with an alteration of the gut microbiota composition over the course of infection, notably characterized by a higher relative abundance of deleterious bacterial taxa such as Enterobacteriaceae and Desulfovibrionaceae. Conversely, several members of the Ruminococcaceae and Lachnospiraceae families, including bacteria known to produce the fermentative products short-chain fatty acids (SCFAs), had a reduced relative proportion compared to non-infected controls. Accordingly, infection led to a transient decrease in systemic SCFA amounts. SCFA supplementation during infection had no effect on clinical and inflammatory parameters. Lastly, a strong correlation between some gut microbiota taxa and clinical and inflammation indices of SARS-CoV-2 infection severity was evidenced. Collectively, alteration of the gut microbiota correlates with disease severity in hamsters making this experimental model valuable for the design of interventional, gut microbiota-targeted, approaches for the control of COVID-19.Abbreviations: SARS-CoV-2, severe acute respiratory syndrome coronavirus 2; COVID-19, coronavirus disease 2019; SCFAs, short-chain fatty acids; dpi, day post-infection; RT-PCR, reverse transcription polymerase chain reaction; IL, interleukin. ACE2, angiotensin converting enzyme 2; TMPRSS2, transmembrane serine protease 2.

Prenatal stress has pro-inflammatory consequences on the immune system in adult rats

The in utero environment is critical for initiating the ontogeny of several physiological systems, including the immune surveillance. Yet, little is known about adverse early experiences on the offspring's immunity and vulnerability to disease. The present work aimed at investigating the impact of restraint prenatal stress (PS) on the development and responsiveness of in vitro and in vivo cellular and humoral immunity of male progeny aged 7 weeks and 6 months. In adult 6-month-old rats, we detected increased circulating CD8(+)-expressing and NK cells in PS rats as compared to controls, associated with higher mRNA expression of IFN-gamma. In addition, in vitro stimulation with phytohemagglutinin-A induced an increase in both the proliferation of T lymphocytes and the secretion of IFN-gamma in PS rats. Interestingly, these alterations were undetectable in younger PS rats (7-week old), except for a slight increase in the mRNA expression of several pro-inflammatory cytokines in peripheral blood mononuclear cells. Moreover, in vivo neutralization of IFN-gamma in young rats had no effects in PS group. In conclusion, we report for the first time long-lasting pro-inflammatory consequences of PS in rats.

Beneficial metabolic effects of rapamycin are associated with enhanced regulatory cells in diet-induced obese mice

The “mechanistic target of rapamycin” (mTOR) is a central controller of growth, proliferation and/or motility of various cell-types ranging from adipocytes to immune cells, thereby linking metabolism and immunity. mTOR signaling is overactivated in obesity, promoting inflammation and insulin resistance. Therefore, great interest exists in the development of mTOR inhibitors as therapeutic drugs for obesity or diabetes. However, despite a plethora of studies characterizing the metabolic consequences of mTOR inhibition in rodent models, its impact on immune changes associated with the obese condition has never been questioned so far. To address this, we used a mouse model of high-fat diet (HFD)-fed mice with and without pharmacologic mTOR inhibition by rapamycin. Rapamycin was weekly administrated to HFD-fed C57BL/6 mice for 22 weeks. Metabolic effects were determined by glucose and insulin tolerance tests and by indirect calorimetry measures of energy expenditure. Inflammatory response and immune cell populations were characterized in blood, adipose tissue and liver. In parallel, the activities of both mTOR complexes (e. g. mTORC1 and mTORC2) were determined in adipose tissue, muscle and liver. We show that rapamycin-treated mice are leaner, have enhanced energy expenditure and are protected against insulin resistance. These beneficial metabolic effects of rapamycin were associated to significant changes of the inflammatory profiles of both adipose tissue and liver. Importantly, immune cells with regulatory functions such as regulatory T-cells (Tregs) and myeloid-derived suppressor cells (MDSCs) were increased in adipose tissue. These rapamycin-triggered metabolic and immune effects resulted from mTORC1 inhibition whilst mTORC2 activity was intact. Taken together, our results reinforce the notion that controlling immune regulatory cells in metabolic tissues is crucial to maintain a proper metabolic status and, more generally, comfort the need to search for novel pharmacological inhibitors of the mTOR signaling pathway to prevent and/or treat metabolic diseases.

Infection of mice lacking interleukin-7 (IL-7) reveals an unexpected role for IL-7 in the development of the parasite Schistosoma mansoni

A single intradermal administration of recombinant interleukin-7 (IL-7) has been shown to aggravate the course of murine schistosomiasis, to favor the development of Th2-associated antibodies specific for the parasite, and to alter migration kinetics and/or migratory route of the parasite within its vertebrate host. Here we show that after infection of IL-7-deficient mice with Schistosoma mansoni, the predominant parasite-specific humoral response follows a Th1 pattern, and the development of the parasite is greatly impaired. In IL-7-deficient mice, increased numbers of larvae reach the lungs and fewer larvae reach the liver, compared to control mice. In the absence of IL-7, female worms show an altered fecundity, leading to decreased numbers of eggs trapped in the tissues and to an amelioration of the pathology of the infected host. The most striking observation is the blockade of parasite growth in an IL-7-defective environment, leading to dwarf male and female worms. The results of this study have important implications for the role of IL-7 in the host-parasite relationship and show how parasites can disable or evade the host immune response.

Antibody response of Schistosoma mansoni-infected human subjects to the recombinant P28 glutathione-S-transferase and to synthetic peptides

The 28-kilodalton antigen of Schistosoma mansoni has been previously described as having importance as the basis for a potential vaccine. The P28 recombinant molecule and three peptides derived from its primary sequence, namely the 24-43, 115-131, and 140-153 peptides, have been tested to evaluate the humoral responses of Kenyan school children previously classified as susceptible or resistant to reinfection after chemotherapy. We report here that the P28 molecule and two of the peptides studied (peptides 115-131 and 140-153) can be used for detecting specific immunoglobulin G (IgG), IgE, and IgA antibodies. Moreover, the IgG4 response of the susceptible population was significantly greater than that of the resistant group, whereas no differences between the two populations were noticed in total IgG anti-P28 antibodies. This suggested that IgG4 could play a role in the lack of immunity of susceptible patients. A strong IgG3 response restricted to the 140-153 peptide was observed but did not discriminate between the resistant and susceptible populations. In contrast, a marked increase in the IgA response to the 140-153 peptide epitope(s) in sera of the resistant population was noticed. Taken together, these results suggest that the P28 antigen and two of the three peptides selected could give predictive information about the development of the disease or the efficiency of vaccination with P28 as the immunogen.

Infection of B-cell-deficient mice by the parasite Schistosoma mansoni: demonstration of the participation of B cells in granuloma modulation

The contribution of B lymphocytes to immunity towards the parasite Schistosoma mansoni has been investigated in a mouse strain rendered genetically B-cell deficient (the muMT mouse). These studies demonstrated that T cells primed in vivo in B-cell-deficient mice proliferate less efficiently in vitro in response to parasite antigenic extracts except at 10 weeks of infection. In addition, analysis of the cytokine profiles (IL-2, IL-4, IL-5 and IFN-gamma), investigated using RT-PCR, showed that spleens of muMT animals displayed a predominant Th1-like profile compared to control, B-cell-intact infected mice. This showed that B cells, either per se or through their secretions, are involved in the in vivo generation and/or maximal expansion of Th2-type T lymphocytes during the course of murine S. mansoni infection. Interestingly, the data showed that B-cell-deficient mice display an increased hepatic fibrosis at 10 weeks postinfection (p.i.), whereas they behaved like infected controls, with regard to the other assessed parasitological parameters (e.g. worm burden estimation). This demonstrated that even if B lymphocytes are not essential for the development of the general immune response towards S. mansoni in the mouse, they may nevertheless be involved in the correct immunoregulation of the granulomatous reaction around the eggs.

Ineffective cellular immune response associated with T-cell apoptosis in susceptible Mycobacterium bovis BCG-infected mice

It has previously been reported that inhibition of delayed-type hypersensitivity-mediating functions of T cells during mycobacterial infection in mice is haplotype dependent. In the present study, we show that Mycobacterium bovis BCG infection induced, in susceptible C57BL/6 and BALB/c mice but not in resistant C3H/HeJ and DBA/2 mice, an important splenomegaly. An in vitro defect in T-cell proliferation in response to T-cell receptor (TCR) stimulation with mitogens or anti-CD3 antibodies was associated with enhanced levels of CD4(+) and CD8(+) T-cell apoptosis in susceptible but not in resistant mice 2 weeks after infection. Further investigations of C57BL/6 and C3H/HeJ mice revealed that in vivo splenomegaly was associated with destruction of the lymphoid tissue architecture, liver cellular infiltrates, and increased numbers of apoptotic cells in both spleen and liver tissue sections. Infection of C57BL/6 mice but not of C3H/HeJ mice induced massive production of tumor necrosis factor alpha (TNF-alpha) in serum, as well as an increase in Fas and Fas ligand (FasL) expression in T cells. In vitro addition of neutralizing anti-TNF-alpha antibodies led to a significant reduction in CD3-induced T-cell apoptosis of both CD4(+) and CD8(+) T cells of C57BL/6 mice, while the blockade of Fas-FasL interactions reduced apoptosis only in CD4(+) but not in CD8(+) T cells. Together, these results suggest that TNF-alpha and Fas-FasL interactions play a role in the activation-induced cell death (AICD) process associated with a defect in T-cell proliferation of the susceptible C57BL/6 mice. T-cell death by apoptosis may represent one of the important components of the ineffective immune response against mycobacterium-induced immunopathology in susceptible hosts.

Mycobacterium bovis BCG producing interleukin-18 increases antigen-specific gamma interferon production in mice

Interleukin-18 (IL-18) and IL-12 play a critical role in the expression of cell-mediated immunity involved in host defense against intracellular pathogens. Both cytokines are produced by macrophages and act in synergy to induce gamma interferon (IFN-gamma) production by T, B, and natural killer cells. In the present study, we analyzed both cellular and humoral responses upon infection with IL-18-secreting BCG of BALB/c and C3H/HeJ mice, two strains known to differ in their ability to support the growth of BCG. The cDNA encoding mature IL-18 was fused in frame with the alpha-antigen signal peptide-coding sequence, cloned downstream of the mycobacterial hsp60 promoter and expressed in BCG. IL-18 produced by the recombinant BCG strain was functional, as judged by NF-kappaB-mediated luciferase induction in a tissue culture assay. When susceptible mice were infected with IL-18-producing BCG, their splenocytes were found to produce higher amounts of Th1 cytokines after stimulation with mycobacterial antigens than the splenocytes of mice infected with the nonrecombinant BCG. This was most prominent for IFN-gamma, although the mycobacterial antigen-specific secretion of granulocyte-macrophage colony-stimulating factor and IL-10 was also augmented after infection with the recombinant BCG compared to infection with nonrecombinant BCG. In contrast, the immunoglobulin G levels in serum against mycobacterial antigens were lower when the mice were infected with IL-18-producing BCG compared to infection with nonrecombinant BCG. The IL-18 effect was delayed in BALB/c compared to C3H/HeJ mice. These results indicate that the production of IL-18 by recombinant BCG may enhance the immunomodulatory properties of BCG further toward a Th1 profile. This may be particularly useful for immunotherapeutic or prophylactic interventions in which a Th1 response is most desirable.

Early variations of host thyroxine and interleukin-7 favor Schistosoma mansoni development

Schistosoma mansoni induces, in the vertebrate host, cutaneous production of interleukin-7 (IL-7), which is beneficial for parasite establishment and development. Infection of mice deficient in IL-7 expression leads to parasite dwarfism. Because similar findings were previously described in hypothyroid mice, this study aimed to elucidate the potential link between IL-7 and thyroid hormones (THs), using several models including hypo- and hyperthyroid mice, modified either transiently or constitutively. Mice treated with thyroxine led to increased worm numbers and development of giant worms, whereas an iodine-deficient diet reduced parasite maturation, egg laying, and liver pathology. Conversely, mice genetically deficient for either of the nuclear TH receptors displayed normal worm development despite modifications in hormone levels, suggesting that thyroxine action is mediated through host receptors. In addition, no modification of antibody titers has been evidenced in thyroxine-treated mice, whereas antibody levels were altered in transgenic animals. These observations suggest that the immune system is not likely to be involved in the modifications of parasite development reported in this study. Interestingly, concomitant treatment with IL-7 and thyroxine had a synergistic effect, leading to recovery of very large worms, thus raising questions about the complexity of interactions between IL-7 and metabolic hormones.

Influence of high-fat feeding on both naive and antigen-experienced T-cell immune response in DO10.11 mice

Obesity is becoming one of the most serious public health problems in industrialized societies, due to the profound changes in lifestyle, and notably in nutrition. Beside diabetes, cardiovascular diseases or hypertension, increased susceptibility to infection is one of the pathological consequences of being overweight. In this paper, we have assessed the influence of a high-fat diet (HFD) rich in saturated fatty acids on the immune system of DO11.10 mice, which are transgenic for a T-cell receptor specifically recognizing a peptide of ovalbumin. We showed that the specific T-cell immune response was impaired by high-fat feeding, and that the expression of this defect is different depending on whether T cells are naive or Ag experienced. Indeed, on in vitro ovalbumin stimulation, spleen T cells from naive HFD-fed transgenic mice showed proliferation similar to that of cells from standard diet (SD)-fed mice, but exhibited a strong inflammatory profile as shown by the markedly increased IFN-gamma/IL-4 ratio. Inversely, spleen T cells from ovalbumin-immunized HFD mice were impaired in their Ag-dependent proliferation compared to cells from SD mice. By co-culture experiments, we showed that both T cells and antigen-presenting cells were involved in this impairment. Moreover, in ovalbumin-immunized HFD animals, a trend towards Th2 response was noted, compared to immunized SD mice. This data implies that naive T cells could participate actively in the low-grade systemic inflammation observed in overweight patients. Moreover, the impaired activity of Ag-experienced T cells could have major consequences both in defence against infection and/or in vaccination protocols.

Immunostimulatory effect of IL-18-encoding plasmid in DNA vaccination against murine Schistosoma mansoni infection

In vivo delivery of DNA encoding antigens is a simple tool to induce immune responses against pathogens. This approach to vaccination also offers the possibility to codeliver plasmids encoding immunomodulatory molecules in order to drive immune responses towards optimal protective effects. In the murine model of Schistosoma mansoni infection, vaccination inducing a Th1 profile has been shown to be protective. In this study, we used a plasmid encoding the Th1-promoting cytokine IL-18, since we observed that percutaneous infection of Balb/c mice strongly induced the production of IL-18 mRNA in the skin. Intradermal injection of the IL-18-encoding plasmid prior to infection did not interfere with parasite migration through the skin although it led to a local and transient cellular infiltration. When the IL-18-encoding plasmid was codelivered with a S. mansoni glutathione S-transferase (Sm28GST)-encoding plasmid, a 30-fold increase of antigen-specific IFN-gamma secretion by spleen cells was observed in comparison to spleen cells from mice that had received only the Sm28GST-encoding plasmid. This immunostimulatory effect was related to a significant protective effect (28% reduction in egg laying and 23% reduction in worm burden) which was attributed to a cooperative effect between both plasmids. Therefore, this study shows that codelivery of an IL-18-encoding plasmid with an antigen-encoding plasmid can stimulate specific cellular responses and induce protective effects against S. mansoni infection.

Analysis of antigenicity and immunogenicity of five different chemically defined constructs of a peptide

The aim of this study was to compare the antigenicity and the immunogenicity of five constructs of a peptide, including the peptide in single copy, a tandem repeat containing three copies, a copolymer with glutaraldehyde and two constructs based on the MAP (Multiple Antigenic Peptide) model, one containing two copies (MAP-2) and the other, eight copies of the peptide (MAP-8). The peptide used in this test was the 115-131 sequence derived from the rSm28-GST antigen of Schistosoma mansoni. All constructs were recognized by rSm28-GST specific antibodies in solid phase immunoassays. However, the binding was higher when the MAP-8 was used as antigen at least partly because of its better coating on the microtiter plates. In vitro lymphoproliferative assays showed that polymer was mitogenic, repeat and MAP-2 did not stimulate rSm28-GST specific T cells while MAP-8 induced a slight response. The injection of MAP-8 to rats led to important antibody and T cell responses higher than those obtained with the other constructs. The IgG2a (cytotoxic antibody in schistosomiasis)/IgG2c (blocking antibody) ratio was independent of the immunogen. Taken together these results demonstrate that both the antigenicity and the immunogenicity of a peptide containing T and B cell epitope(s) are strongly related to the molecular form whereby it is presented and that the MAP-8 construct can be useful in serodiagnosis or in vaccination trials using synthetic peptides.

Protective effect of rSm28GST-specific T cells in schistosomiasis: role of gamma interferon

Immunization with a single dose of 50 micrograms of recombinant Schistosoma mansoni 28-kDa glutathione-S-transferase (rSm28GST) was able to induce a reduction in the worm burden, the number of eggs, and the degree of hepatic fibrosis as quantified by the measurement of collagen content in the liver of S. mansoni-infected mice. No relationship was found between anti-Sm28GST immunoglobulin G and immunoglobulin A titers and the levels of protection obtained. Adoptive transfers of Sm28GST-specific total, CD4+, or CD8+ T cells reproduced the protective effect obtained with the recombinant molecule. Moreover, experiments studying in vivo T-cell depletion demonstrated that anti-CD4- or anti-CD8-treated mice showed a significant decrease in the protective effect conferred, suggesting a role of the two T-cell subpopulations in the expression of Sm28GST-mediated protection against hepatic damage. Sm28GST-specific cells produced little interleukin-4 and high levels of gamma interferon. Treatment of immunized mice with anti-gamma interferon antibody totally suppressed the Sm28GST-induced protective effect and led to the rapid death of infected animals, suggesting a role for this cytokine in the expression of the protective immunity obtained after immunization with rSm28GST.

Interleukin-7 in the skin of Schistosoma mansoni-infected mice is associated with a decrease in interferon-gamma production and leads to an aggravation of the disease

The effect of recombinant interleukin-7 (rIL-7) on the course of murine schistosomiasis and the development of the accompanying immune response were investigated. We demonstrated that IL-7 expression could be detected in the skin of infected mice from 1 to 21 days following infection. We here report that intradermal injection of exogenous human IL-7, prior to the penetration of the parasite into the skin, leads to a more severe liver pathology and an increased number of surviving adult parasites. In addition, injection of rIL-7 alters parasite migration (estimation of burdens of young larvae in lungs and liver). Administration of rIL-7 led to a decrease of IL-12 and interferon-gamma-(IFN-gamma) specific messengers RNA in skin and, more markedly, in skin-draining lymph nodes. The number of B220 expressing cells was increased, and T-cell number was reduced, in IL-7-treated infected mice. In addition, levels of IFN-gamma and IL-4 in sera were significantly reduced, whereas there was a shift from a Th1 to a Th2 type associated humoral response towards the egg antigens. Our experimental observation illustrate that the exogenous administration of rIL-7 affects both the development of the host's immune response and the behaviour of the parasite within the infected host. The early and specific production of IL-7 in the host skin, following infection with Schistosoma mansoni, raises fascinating questions concerning the relationships between the parasite and its host at the very beginning of their interaction.

Removal of senescent cells reduces the viral load and attenuates pulmonary and systemic inflammation in SARS-CoV-2-infected, aged hamsters

Older age is one of the strongest risk factors for severe COVID-19. In this study, we determined whether age-associated cellular senescence contributes to the severity of experimental COVID-19. Aged golden hamsters accumulate senescent cells in the lungs, and the senolytic drug ABT-263, a BCL-2 inhibitor, depletes these cells at baseline and during SARS-CoV-2 infection. Relative to young hamsters, aged hamsters had a greater viral load during the acute phase of infection and displayed higher levels of sequelae during the post-acute phase. Early treatment with ABT-263 lowered pulmonary viral load in aged (but not young) animals, an effect associated with lower expression of ACE2, the receptor for SARS-CoV-2. ABT-263 treatment also led to lower pulmonary and systemic levels of senescence-associated secretory phenotype factors and to amelioration of early and late lung disease. These data demonstrate the causative role of age-associated pre-existing senescent cells on COVID-19 severity and have clear clinical relevance.

Cellular immune responses of a Senegalese community recently exposed to Schistosoma mansoni: correlations of infection level with age and inflammatory cytokine production by soluble egg antigen-specific cells

A recently reported epidemic of Schistosoma mansoni infection in Senegal provided an opportunity to study the dynamics of the development of immunity to human schistosomiasis. We report here on the cell-mediated immune response in a population of 99 females and 95 males, with particular emphasis on the relationship between intensity of infection and age. We found that the intensity of infection correlated negatively with age in females but not in males. In men and women, both Th1- and Th2-type cytokines were detected upon in vitro stimulation of PBMCs with soluble egg antigen (SEA) or soluble adult worm antigens (SWAP). In the female group, SEA-induced PBMC proliferation was associated with the production of IFN-gamma, IL-2 and IL-5, all of which correlated negatively with intensity of infection. Most cytokine production correlated positively with age. Spontaneous production of TNF-alpha, IL-6 and IL-10 was higher in the infected population than in an uninfected control group. Our results suggest that immunity to infection could be more pronounced in the female population and associated with a Th0/1 + 2 pattern of cytokine secretion mediated by soluble egg antigen (SEA).

Multiple Selection Criteria for Probiotic Strains with High Potential for Obesity Management

Since alterations of the gut microbiota have been shown to play a major role in obesity, probiotics have attracted attention. Our aim was to identify probiotic candidates for the management of obesity using a combination of in vitro and in vivo approaches. We evaluated in vitro the ability of 23 strains to limit lipid accumulation in adipocytes and to enhance the secretion of satiety-promoting gut peptide in enteroendocrine cells. Following the in vitro screening, selected strains were further investigated in vivo, single, or as mixtures, using a murine model of diet-induced obesity. Strain Bifidobacterium longum PI10 administrated alone and the mixture of B. animalis subsp. lactis LA804 and Lactobacillus gasseri LA806 limited body weight gain and reduced obesity-associated metabolic dysfunction and inflammation. These protective effects were associated with changes in the hypothalamic gene expression of leptin and leptin receptor as well as with changes in the composition of gut microbiota and the profile of bile acids. This study provides crucial clues to identify new potential probiotics as effective therapeutic approaches in the management of obesity, while also providing some insights into their mechanisms of action.