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Protein S (PS), the critical plasma cofactor for the anticoagulants tissue factor (TF) pathway inhibitor (TFPI) and activated protein C (APC), circulates in two functionally distinct pools: free (anticoagulant) or bound to complement component 4b-binding protein (C4BP) (anti-inflammatory). Acquired free PS deficiency is detected in several viral infections, but its cause is unclear. Here, we identified a shear-dependent interaction between PS and von Willebrand Factor (VWF) by mass spectrometry. Consistently, plasma PS and VWF comigrated in both native and agarose gel electrophoresis. The PS/VWF interaction was blocked by TFPI but not APC, suggesting an interaction with the C-terminal sex hormone binding globulin (SHBG) region of PS. Microfluidic systems, mimicking arterial laminar flow or disrupted turbulent flow, demonstrated that PS stably binds VWF as VWF unfolds under turbulent flow. PS/VWF complexes also localized to platelet thrombi under laminar arterial flow. In thrombin generation-based assays, shearing plasma decreased PS activity, an effect not seen in the absence of VWF. Finally, free PS deficiency in COVID-19 patients, measured using an antibody that binds near the C4BP binding site in SHBG, correlated with changes in VWF, but not C4BP, and with thrombin generation. Our data suggest that PS binds to a shear-exposed site on VWF, thus sequestering free PS and decreasing its anticoagulant activity, which would account for the increased thrombin generation potential. As many viral infections present with free PS deficiency, elevated circulating VWF, and increased vascular shear, we propose that the PS/VWF interaction reported here is a likely contributor to virus-associated thrombotic risk.
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BACKGROUND: HIV-1 infection is associated with multiple procoagulant changes and increased thrombotic risk. Possible mechanisms for this risk include heigthened expression of procoagulant tissue factor (TF) on circulating monocytes, extracellular vesicles, and viral particles and/or acquired deficiency of protein S (PS), a critical cofactor for the anticoagulant protein C (PC). PS deficiency occurs in up to 76% of people living with HIV-1 (PLWH). As increased ex vivo plasma thrombin generation is a strong predictor of mortality, we investigated whether PS and plasma TF are associated with plasma thrombin generation. METHODS: We analyzed plasma samples from 9 healthy controls, 17 PLWH on first diagnosis (naive), and 13 PLWH on antiretroviral therapy (ART). Plasma thrombin generation, total and free PS, PC, C4b-binding protein, and TF activity were measured. RESULTS: We determined that the plasma thrombin generation assay is insensitive to PS, because of a lack of PC activation, and developed a modified PS-sensitive assay. Total plasma PS was reduced in 58% of the naive and 38% of the ART-treated PLWH samples and correlated with increased thrombin generation in the modified assay. Conversely, plasma TF was not increased in our patient population, suggesting that it does not significantly contribute to ex vivo plasma thrombin generation. CONCLUSION: These data suggest that reduced total plasma PS contributes to the thrombotic risk associated with HIV-1 infection and can serve as a prothrombotic biomarker. In addition, our refined thrombin generation assay offers a more sensitive tool to assess the functional consequences of acquired PS deficiency in PLWH.
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Infecções por HIV , Proteína S , Biomarcadores , Infecções por HIV/complicações , Infecções por HIV/tratamento farmacológico , Humanos , Trombina/metabolismo , TromboplastinaRESUMO
Introduction: Long COVID is the overarching name for a wide variety of disorders that may follow the diagnosis of acute SARS-COVID-19 infection and persist for weeks to many months. Nearly every organ system may be affected. Methods: We report nine patients suffering with Long COVID for 101 to 547 days. All exhibited significant perturbations of their immune systems, but only one was known to be immunodeficient prior to the studies directed at evaluating them for possible treatment. Neurological and cardiac symptoms were most common. Based on this data and other evidence suggesting autoimmune reactivity, we planned to treat them for 3 months with long-term high-dose immunoglobulin therapy. If there was evidence of benefit at 3 months, the regimen was continued. Results: The patients' ages ranged from 34 to 79 years-with five male and four female patients, respectively. All nine patients exhibited significant immune perturbations prior to treatment. One patient declined this treatment, and insurance support was not approved for two others. The other six have been treated, and all have had a significant to remarkable clinical benefit. Conclusion: Long-term high-dose immunoglobulin therapy is an effective therapeutic option for treating patients with Long COVID.
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COVID-19 , Humanos , Masculino , Feminino , Adulto , Pessoa de Meia-Idade , Idoso , COVID-19/etiologia , Síndrome de COVID-19 Pós-Aguda , Pulmão , Imunoglobulinas , Imunização Passiva/efeitos adversosRESUMO
Newborn mice are unable to clear Pneumocystis (PC) infection with the same efficiency as adults due, in part, to their inability to develop a robust immune response to infection until three weeks of age. It is known that infants tend develop a Th2 skewed response to antigen so we sought to determine whether a biased cytokine response altered the clearance of PC infection in neonatal mice. P. murina infection in neonatal mice resulted in increased IL-4 expression by CD4 T cells and myeloid cells, augmented IL-13 secretion within the airways and increased arginase activity in the airways, indicative of Th2-type responses. P. murina-infected IL-4Rα-/- neonates had a shift towards Th1 cytokine production and increased numbers of CD4 and CD8 T cells within the lung as well as elevated levels of P. murina-specific IgG. IFNγ-/- and IL-23 p19-/- mice had altered CD4-T cell-dependent cytokine and cell responses. Though we could alter the T helper cell environment in neonatal knockout mice, there was no loss in the ability of these pups to clear infection. It is possible that the Th2 phenotype normally seen in neonatal mice protects the developing lung from pro-inflammatory immune responses without compromising host defense against P. murina.
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Regulatory properties of macrophages associated with alternative activation serve to limit the exaggerated inflammatory response during pneumonia caused by Pseudomonas aeruginosa infection. Arginase-1 is an important effector of these macrophages believed to play an essential role in decreasing injury and promoting repair. We investigated the role of arginase-1 in the control of inflammatory immune responses to P. aeruginosa pneumonia in mice that exhibit different immunologic phenotypes. C57BL/6 mice with conditional knockout of the arginase-1 (Arg1) gene from myeloid cells (Arg1ΔM) or BALB/c mice treated with small molecule inhibitors of arginase were infected intratracheally with P. aeruginosa. Weight loss, mortality, bacterial clearance, and lung injury were assessed and compared, as were the characterization of immune cell populations over time post-infection. Myeloid arginase-1 deletion resulted in greater morbidity along with more severe inflammatory responses compared to littermate control mice. Arg1ΔM mice had greater numbers of neutrophils, macrophages, and lymphocytes in their airways and lymph nodes compared to littermate controls. Additionally, Arg1ΔM mice recovered from inflammatory lung injury at a significantly slower rate. Conversely, treatment of BALB/c mice with the arginase inhibitor S-(2-boronoethyl)-l-cysteine hydrochloride (BEC) did not change morbidity as defined by weight loss, but mice at day 10 post-infection treated with BEC had gained significantly more weight back than controls. Neutrophil and macrophage infiltration were similar between groups in the lung parenchyma, and neutrophil migration into the airways was reduced by BEC treatment. Differences seem to lie in the impact on T cell subset disposition. Arg1ΔM mice had increased total CD4+ T cell expansion in the lymph nodes, and increased T cell activation, IFNγ production, and IL-17 production in the lymph nodes, lung interstitium, and airways, while treatment with BEC had no impact on T cell activation or IL-17 production, but reduced the number of T cells producing IFNγ in the lungs. Lung injury scores were increased in the Arg1ΔM mice, but no differences were observed in the mice treated with pharmacologic arginase inhibitors. Overall, myeloid arginase production was demonstrated to be essential for control of damaging inflammatory responses associated with P. aeruginosa pneumonia in C57BL/6 mice, in contrast to a protective effect in the Th2-dominant BALB/c mice when arginase activity is globally inhibited.
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Arginase/metabolismo , Linfócitos T CD4-Positivos/imunologia , Inflamação/imunologia , Pulmão/metabolismo , Neutrófilos/imunologia , Pneumonia Bacteriana/imunologia , Infecções por Pseudomonas/imunologia , Pseudomonas aeruginosa/fisiologia , Subpopulações de Linfócitos T/imunologia , Animais , Arginase/antagonistas & inibidores , Arginase/genética , Ácidos Borônicos/farmacologia , Citocinas/metabolismo , Feminino , Patrimônio Genético , Predisposição Genética para Doença , Humanos , Imunomodulação , Pulmão/patologia , Ativação Linfocitária , Ativação de Macrófagos , Masculino , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Endogâmicos C57BL , Camundongos Knockout , Equilíbrio Th1-Th2RESUMO
OBJECTIVE: Thrombocytopenia is associated with many viral infections suggesting virions interact with and affect platelets. Consistently, viral particles are seen inside platelets, and platelet activation markers are detected in viremic patients. In this article, we sought mechanistic insights into these virion/platelet interactions by examining how platelets endocytose, traffic, and are activated by a model virion. Approach and Results: Using fluorescently tagged HIV-1 pseudovirions, 3-dimensional structured illumination microscopy, and transgenic mouse models, we probed the interactions between platelets and virions. Mouse platelets used known endocytic machinery, that is, dynamin, VAMP (vesicle-associated membrane protein)-3, and Arf6 (ADP-ribosylation factor 6), to take up and traffic HIV-1 pseudovirions. Endocytosed HIV-1 pseudovirions trafficked through early (Rab4+) and late endosomes (Rab7+), and then to an LC3+ (microtubule-associated protein 1A/1B-light chain 3) compartment. Incubation with virions induced IRAK4 (interleukin 1 receptor-associated kinase 4), Akt (protein kinase B), and IKK (IκB kinase) activation, granule secretion, and platelet-leukocyte aggregate formation. This activation required TLRs (Toll-like receptors) and MyD88 (myeloid differentiation primary response protein 88) but was less extensive and slower than activation with thrombin. In vivo, HIV-1 pseudovirions injection led to virion uptake and platelet activation, as measured by IKK activation, platelet-leukocyte aggregate formation, and mild thrombocytopenia. All were decreased in VAMP-3-/- and, megakaryocyte/platelet-specific, Arf6-/- mice. Similar platelet activation profiles (increased platelet-leukocyte aggregates, plasma platelet factor 4, and phospho-IκBα) were detected in newly diagnosed and antiretroviral therapy-controlled HIV-1+ patients. CONCLUSIONS: Collectively, our data provide mechanistic insights into the cell biology of how platelets endocytose and process virions. We propose a mechanism by which platelets sample the circulation and respond to potential pathogens that they take up.
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Plaquetas/metabolismo , Endocitose , Infecções por HIV/sangue , HIV-1/patogenicidade , Ativação Plaquetária , Trombocitopenia/sangue , Receptores Toll-Like/sangue , Vírion , Fator 6 de Ribosilação do ADP , Fatores de Ribosilação do ADP/sangue , Fatores de Ribosilação do ADP/genética , Animais , Antirretrovirais/uso terapêutico , Plaquetas/virologia , Agregação Celular , Células Cultivadas , Infecções por HIV/diagnóstico , Infecções por HIV/tratamento farmacológico , Infecções por HIV/virologia , Humanos , Quinase I-kappa B/sangue , Quinase I-kappa B/genética , Leucócitos/metabolismo , Leucócitos/virologia , Camundongos Endogâmicos C57BL , Camundongos Knockout , Fator 88 de Diferenciação Mieloide/sangue , Fator 88 de Diferenciação Mieloide/genética , Fator Plaquetário 4/sangue , Fator Plaquetário 4/genética , Trombocitopenia/diagnóstico , Trombocitopenia/virologia , Receptores Toll-Like/deficiência , Receptores Toll-Like/genética , Proteína 3 Associada à Membrana da Vesícula/sangue , Proteína 3 Associada à Membrana da Vesícula/genéticaRESUMO
BACKGROUND: We previously reported increased unstimulated blood levels of interferon-gamma in persons with latent tuberculosis infection (LTBI) in the United States, suggesting enhanced immune activation in LTBI. To investigate this further in a TB-endemic setting, we assessed interferon-gamma levels in persons with and without LTBI in Peru. METHODS: We analyzed data from patients with and without a recent type 1 (spontaneous) acute myocardial infarction (AMI) who were enrolled from two public hospital networks in Lima, Peru, and underwent LTBI testing using the QuantiFERON® TB Gold In-tube (QFT) assay. Participants with a positive QFT test were defined as having LTBI, whereas participants with a negative QFT test were defined as non-LTBI. Unstimulated interferon-gamma was quantified via enzyme-linked immunosorbent assay in the QFT nil-tube, which does not contain antigens. We compared unstimulated interferon-gamma levels between LTBI and non-LTBI groups using the Wilcoxon rank sum test. We used proportional odds modeling for multivariable analysis. RESULTS: Data from 214 participants were included in this analysis. Of those, 120 (56%) had LTBI. There were no significant differences in age, sex and comorbidities between LTBI and non-LTBI participants, except for recent AMI that was more frequent in LTBI. LTBI participants had higher unstimulated interferon-gamma levels compared to non-LTBI participants (median, interquartile range; 14 pg/mL, 6.5-52.8 vs. 6.5 pg/mL, 4.5-15; P<0.01). LTBI remained associated with higher unstimulated interferon-gamma levels after controlling for age, sex, recent AMI, history of hypertension, diabetes mellitus, dyslipidemia, end stage renal disease, malignancy, obesity, and tobacco use (adjusted odds ratio, 2.93; 95% confidence interval, 1.8-4.9). In a sensitivity analysis that excluded participants with AMI, the association between unstimulated interferon-gamma and LTBI remained present (adjusted odds ratio; 3.93; 95% confidence interval, 1.9-8.2). CONCLUSIONS: LTBI was associated with higher unstimulated interferon-gamma levels. These data suggest ongoing immune activation in LTBI.
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Interferon gama/sangue , Tuberculose Latente/sangue , Fatores Etários , Idoso , Feminino , Humanos , Tuberculose Latente/epidemiologia , Masculino , Pessoa de Meia-Idade , Peru/epidemiologia , Fatores de RiscoRESUMO
Background: Tuberculosis has been associated with an increased risk of cardiovascular disease (CVD), including acute myocardial infarction (AMI). We investigated whether latent tuberculosis infection (LTBI) is associated with AMI. Methods: We conducted a case-control study in 2 large national public hospital networks in Lima, Peru, between July 2015 and March 2017. Case patients were patients with a first time diagnosis of type 1 (spontaneous) AMI. Controls were patients without a history of AMI. We excluded patients with known human immunodeficiency virus infection, tuberculosis disease, or prior LTBI treatment. We used the QuantiFERON-TB Gold In-Tube assay to identify LTBI. We used logistic regression modeling to estimate the odds ratio (OR) of LTBI in AMI case patients versus non-AMI controls. Results: We enrolled 105 AMI case patients and 110 non-AMI controls during the study period. Overall, the median age was 62 years (interquartile range, 56-70 years); 69% of patients were male; 64% had hypertension, 40% dyslipidemia, and 39% diabetes mellitus; 30% used tobacco; and 24% were obese. AMI case patients were more likely than controls to be male (80% vs 59%; P < .01) and tobacco users (41% vs 20%; P < .01). LTBI was more frequent in AMI case patients than in controls (64% vs 49% [P = .03]; OR, 1.86; 95% confidence interval [CI], 1.08-3.22). After adjustment for age, sex, hypertension, dyslipidemia, diabetes mellitus, tobacco use, obesity, and family history of coronary artery disease, LTBI remained independently associated with AMI (adjusted OR, 1.90; 95% CI, 1.05-3.45). Conclusions: LTBI was independently associated with AMI. Our results suggest a potentially important role of LTBI in CVD.
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Tuberculose Latente/complicações , Infarto do Miocárdio/complicações , Idoso , Estudos de Casos e Controles , Feminino , Humanos , Tuberculose Latente/diagnóstico , Modelos Logísticos , Masculino , Pessoa de Meia-Idade , Peru , Fatores de RiscoRESUMO
Pneumocystis species are fungal pathogens that cause pneumonia in immunocompromised hosts. Lung damage during Pneumocystis pneumonia is predominately due to the inflammatory immune response. Pneumocystis species have a biphasic life cycle. Optimal innate immune responses to Pneumocystis species are dependent on stimulation with the cyst life cycle stage. Conversely, the trophic life cycle stage broadly suppresses proinflammatory responses to multiple pathogen-associated molecular patterns (PAMPs), including ß-1,3-glucan. Little is known about the contribution of these life cycle stages to the development of protective adaptive responses to Pneumocystis infection. Here we report that CD4+ T cells primed in the presence of trophic forms are sufficient to mediate clearance of trophic forms and cysts. In addition, primary infection with trophic forms is sufficient to prime B-cell memory responses capable of clearing a secondary infection with Pneumocystis following CD4+ T cell depletion. While trophic forms are sufficient for initiation of adaptive immune responses in immunocompetent mice, infection of immunocompromised recombination-activating gene 2 knockout (RAG2-/-) mice with trophic forms in the absence of cysts does not lead to the severe weight loss and infiltration of innate immune cells associated with the development of Pneumocystis pneumonia.
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Imunidade Adaptativa , Imunidade Inata , Infecções por Pneumocystis/imunologia , Pneumocystis/imunologia , Animais , Linfócitos B/imunologia , Linfócitos T CD4-Positivos/imunologia , Proteínas de Ligação a DNA/deficiência , Hospedeiro Imunocomprometido , Memória Imunológica , Camundongos Endogâmicos BALB C , Camundongos KnockoutRESUMO
The life cycle of the opportunistic fungal pathogen Pneumocystis murina consists of a trophic stage and an ascus-like cystic stage. Infection with the cyst stage induces proinflammatory immune responses, while trophic forms suppress the cytokine response to multiple pathogen-associated molecular patterns (PAMPs), including ß-glucan. A targeted gene expression assay was used to evaluate the dendritic cell response following stimulation with trophic forms alone, with a normal mixture of trophic forms and cysts, or with ß-glucan. We demonstrate that stimulation with trophic forms downregulated the expression of multiple genes normally associated with the response to infection, including genes encoding transcription factors. Trophic forms also suppressed the expression of genes related to antigen processing and presentation, including the gene encoding the major histocompatibility complex (MHC) class II transactivator, CIITA. Stimulation of dendritic cells with trophic forms, but not a mixture of trophic forms and cysts, reduced the expression of MHC class II and the costimulatory molecule CD40 on the surface of the cells. These defects in the expression of MHC class II and costimulatory molecules corresponded with a reduced capacity for trophic form-loaded dendritic cells to stimulate CD4+ T cell proliferation and polarization. These data are consistent with the delayed innate and adaptive responses previously observed in immunocompetent mice inoculated with trophic forms compared to responses in mice inoculated with a mixture of trophic forms and cysts. We propose that trophic forms broadly inhibit the ability of dendritic cells to fulfill their role as antigen-presenting cells.
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Linfócitos T CD4-Positivos/imunologia , Células Dendríticas/imunologia , Células Dendríticas/microbiologia , Pneumocystis/crescimento & desenvolvimento , Pneumocystis/imunologia , Animais , Apresentação de Antígeno , Células Dendríticas/metabolismo , Células Dendríticas/patologia , Regulação da Expressão Gênica , Antígenos de Histocompatibilidade Classe II/genética , Antígenos de Histocompatibilidade Classe II/imunologia , Ativação Linfocitária , Camundongos , Moléculas com Motivos Associados a Patógenos/imunologia , Pneumonia por Pneumocystis/imunologia , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismo , beta-Glucanas/imunologia , beta-Glucanas/metabolismoRESUMO
Development of Pneumocystis pneumonia (PCP) is a common problem among immunosuppressed individuals. There are windows of opportunity in which vaccination would be beneficial, but to date, no vaccines have made it to clinical trials. Significant hurdles to vaccine development include host range specificity, making it difficult to translate from animal models to humans. Discovery of cross-reactive epitopes is critical to moving vaccine candidates from preclinical animal studies to clinical trials.
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Vacinas Fúngicas/imunologia , Pneumocystis carinii/imunologia , Pneumonia por Pneumocystis/prevenção & controle , Animais , HumanosRESUMO
Recent studies show a substantial incidence of Pneumocystis jirovecii colonization and infection in patients with chronic inflammatory lung conditions. However, little is known about the impact of Pneumocystis upon the regulation of pulmonary immunity. We demonstrate here that Pneumocystis polarizes macrophages towards an alternatively activated macrophage-like phenotype. Genetically engineered mice that lack the ability to signal through IL-4 and IL-13 were used to show that Pneumocystis alternative macrophage activation is dependent upon signaling through these cytokines. To determine whether Pneumocystis-induced macrophage polarization would impact subsequent immune responses, we infected mice with Pneumocystis and then challenged them with Pseudomonas aeruginosa 14 days later. In co-infected animals, a higher proportion of macrophages in the alveolar and interstitial spaces expressed both classical and alternatively activated markers and produced the regulatory cytokines TGFß and IL-10, as well as higher arginase levels than in mice infected with P. aeruginosa alone. Our results suggest that Pneumocystis reprograms the overall macrophage repertoire in the lung to that of a more alternatively-activated setpoint, thereby altering subsequent immune responses. These data may help to explain the association between Pneumocystis infection and decline in pulmonary function.
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Macrófagos Alveolares/imunologia , Macrófagos Alveolares/metabolismo , Infecções por Pneumocystis/imunologia , Infecções por Pneumocystis/metabolismo , Animais , Biomarcadores , Citocinas/metabolismo , Modelos Animais de Doenças , Imunofenotipagem , Ativação de Macrófagos/imunologia , Camundongos , Camundongos Knockout , Fenótipo , Infecções por Pneumocystis/genética , Infecções por Pneumocystis/microbiologia , Pneumocystis carinii/imunologia , Pneumonia Bacteriana/genética , Pneumonia Bacteriana/imunologia , Pneumonia Bacteriana/metabolismo , Pneumonia Bacteriana/microbiologia , Receptores de Superfície Celular/deficiência , Receptores de Superfície Celular/genéticaRESUMO
The cyst cell wall ß-glucans of Pneumocystis have been shown to stimulate immune responses in lung epithelial cells, dendritic cells, and alveolar macrophages. Little is known about how the trophic life forms, which do not have a fungal cell wall, interact with these innate immune cells. Here, we report differences in the responses of both neonatal and adult mice to the trophic and cystic life cycle stages of Pneumocystis murina The adult and neonatal immune responses to infection with Pneumocystis murina trophic forms were less robust than the response to infection with a physiologically normal mixture of cysts and trophic forms. Cysts promoted the recruitment of nonresident innate immune cells and T and B cells into the lungs. Cysts, but not trophic forms, stimulated increased IFN-γ cytokine concentrations in the alveolar spaces, and an increase in IFN-γ-producing CD4+ T cells. In vitro, bone marrow-derived dendritic cells (BMDCs) stimulated with cysts produced the proinflammatory cytokines IL-1ß and IL-6. In contrast, trophic forms suppressed ß-glucan-, LTA-, and LPS-induced IL-1ß, IL-6, and TNFα production by BMDCs and antigen presentation to CD4+ T cells. The negative effects of trophic forms were not due to ligation of mannose receptor. Our results indicate that optimal innate and adaptive immune responses to Pneumocystis species are dependent on stimulation with the cyst life cycle stage. Conversely, trophic forms suppress ß-glucan-induced proinflammatory responses in vitro, suggesting that the trophic forms dampen cyst-induced inflammation in vivo.
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We previously reported that neonatal mice infected with influenza A virus (IAV) develop interstitial pneumonia characterized by reduced lung cytokine and chemokine responses. The failure of T cells to infiltrate the airways of neonates correlated with delayed clearance of sublethal IAV infections compared to adults. We hypothesized that negative regulators in the neonatal lungs such as cytokines or T regulatory (Treg) cells are responsible for these differences. Neonates either deficient in interleukin-10 (IL-10) or with T cells unresponsive to transforming growth factor-ß signaling due to absence of SMAD family member 4 (Smad4) had similar IAV clearance kinetics to wild-type pups and no difference in T-cell responses. In contrast, functional depletion of Treg cells with anti-CD25 monoclonal antibody resulted in increased proportions of activated CD4(+) T cells in the lungs, but failure to clear IAV. Similarly, scurfy pups (mutation in forkhead box P3 [Foxp3] rendering them deficient in Treg cells) had increased proportions of activated T cells in the lungs compared to littermate controls. Scurfy pups also had increased proportions of IL-13-producing CD4(+) T cells. Interestingly, like anti-CD25-treated pups, scurfy pups had significantly elevated viral loads compared to controls. Based on these data, we conclude that Tregs are critical for clearance of IAV in neonatal mice.
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Vírus da Influenza A/imunologia , Infecções por Orthomyxoviridae/imunologia , Linfócitos T Reguladores/imunologia , Animais , Animais Recém-Nascidos , Feminino , Humanos , Pulmão/patologia , Pulmão/virologia , Masculino , Camundongos Endogâmicos C57BL , Carga ViralRESUMO
B cells play a critical role in the clearance of Pneumocystis. In addition to production of Pneumocystis-specific Abs, B cells are required during the priming phase for CD4(+) T cells to expand normally and generate memory. Clearance of Pneumocystis was found to be dependent on Ag specific B cells and on the ability of B cells to secrete Pneumocystis-specific Ab, as mice with B cells defective in these functions or with a restricted BCR were unable to control Pneumocystis infection. Because Pneumocystis-specific antiserum was only able to partially protect B cell-deficient mice from infection, we hypothesized that optimal T cell priming requires fully functional B cells. Using adoptive transfer and B cell depletion strategies, we determined that optimal priming of CD4(+) T cells requires B cells during the first 2-3 d of infection and that this was independent of the production of Ab. T cells that were removed from Pneumocystis-infected mice during the priming phase were fully functional and able to clear Pneumocystis infection upon adoptive transfer into Rag1(-/-) hosts, but this effect was ablated in mice that lacked fully functional B cells. Our results indicate that T cell priming requires a complete environment of Ag presentation and activation signals to become fully functional in this model of Pneumocystis infection.
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Anticorpos Antifúngicos/biossíntese , Linfócitos B/imunologia , Linfócitos T CD4-Positivos/imunologia , Linfócitos T CD8-Positivos/imunologia , Memória Imunológica , Pneumocystis/imunologia , Pneumonia por Pneumocystis/imunologia , Transferência Adotiva , Animais , Linfócitos B/microbiologia , Linfócitos T CD4-Positivos/microbiologia , Linfócitos T CD4-Positivos/transplante , Linfócitos T CD8-Positivos/microbiologia , Proliferação de Células , Deleção de Genes , Expressão Gênica , Proteínas de Homeodomínio/genética , Proteínas de Homeodomínio/imunologia , Imunidade Humoral , Ativação Linfocitária , Depleção Linfocítica , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Endogâmicos C57BL , Camundongos Knockout , Pneumonia por Pneumocystis/microbiologia , Pneumonia por Pneumocystis/patologia , Pneumonia por Pneumocystis/terapiaRESUMO
The burden of tuberculosis and cardiovascular disease (CVD) is enormous worldwide. CVD rates are rapidly increasing in low- and middle-income countries. Public health programs have been challenged with the overlapping tuberculosis and CVD epidemics. Monocyte/macrophages, lymphocytes and cytokines involved in cellular mediated immune responses against Mycobacterium tuberculosis are also main drivers of atherogenesis, suggesting a potential pathogenic role of tuberculosis in CVD via mechanisms that have been described for other pathogens that establish chronic infection and latency. Studies have shown a pro-atherogenic effect of antibody-mediated responses against mycobacterial heat shock protein-65 through cross reaction with self-antigens in human vessels. Furthermore, subsets of mycobacteria actively replicate during latent tuberculosis infection (LTBI), and recent studies suggest that LTBI is associated with persistent chronic inflammation that may lead to CVD. Recent epidemiologic work has shown that the risk of CVD in persons who develop tuberculosis is higher than in persons without a history of tuberculosis, even several years after recovery from tuberculosis. Together, these data suggest that tuberculosis may play a role in the pathogenesis of CVD. Further research to investigate a potential link between tuberculosis and CVD is warranted.
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Pneumocystis species are opportunistic fungal pathogens that induce tumor necrosis factor (TNF) production by alveolar macrophages. Here we report that B cells from the draining lymph nodes as well as lung CD4(+) T cells are important producers of TNF upon Pneumocystis murina infection. To determine the importance of B cell-derived TNF in the primary response to P. murina, we generated bone marrow chimeras whose B cells were unable to produce TNF. The lung P. murina burden at 10 days postinfection in TNF knockout (TNFKO) chimeras was significantly higher than that in wild-type (WT) chimeras, which corresponded to reduced numbers of activated CD4(+) T cells in the lungs at this early time point. Furthermore, CD4(+) T cells isolated from P. murina-infected TNFKO chimeras were unable to stimulate clearance of P. murina upon adoptive transfer to recombinase-deficient (RAG1KO) hosts. Together, these data indicate that B cell-derived TNF plays an important function in promoting CD4(+) T cell expansion and production of TNF and facilitating protection against P. murina infection.
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Linfócitos B/imunologia , Pneumocystis/imunologia , Pneumonia por Pneumocystis/imunologia , Fator de Necrose Tumoral alfa/metabolismo , Animais , Linfócitos T CD4-Positivos/imunologia , Contagem de Colônia Microbiana , Modelos Animais de Doenças , Técnicas de Inativação de Genes , Pulmão/microbiologia , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Endogâmicos C57BL , Camundongos Knockout , Fator de Necrose Tumoral alfa/genéticaRESUMO
Influenza infection predisposes patients to secondary bacterial pneumonia that contributes significantly to morbidity and mortality. Although this association is well documented, the mechanisms that govern this synergism are poorly understood. A window of hyporesponsiveness following influenza infection has been associated with a substantial increase in local and systemic IFN-γ concentrations. Recent data suggest that the oxazolidinone antibiotic linezolid decreases IFN-γ and TNF-α production in vitro from stimulated PBMCs. We therefore sought to determine whether linezolid would reverse immune hyporesponsiveness after influenza infection in mice through its effects on IFN-γ. In vivo dose-response studies demonstrated that oral linezolid administration sufficiently decreased bronchoalveolar lavage fluid levels of IFN-γ at day 7 postinfluenza infection in a dose-dependent manner. The drug also decreased morbidity as measured by weight loss compared with vehicle-treated controls. When mice were challenged intranasally with Streptococcus pneumoniae 7 d postinfection with influenza, linezolid pretreatment led to decreased IFN-γ and TNF-α production, decreased weight loss, and lower bacterial burdens at 24 h postbacterial infection in comparison with vehicle-treated controls. To determine whether these effects were due to suppression of IFN-γ, linezolid-treated animals were given intranasal instillations of rIFN-γ before challenge with S. pneumoniae. This partially reversed the protective effects observed in the linezolid-treated mice, suggesting that the modulatory effects of linezolid are mediated partially by its ability to blunt IFN-γ production. These results suggest that IFN-γ, and potentially TNF-α, may be useful drug targets for prophylaxis against secondary bacterial pneumonia following influenza infection.
Assuntos
Acetamidas/uso terapêutico , Antibacterianos/uso terapêutico , Coinfecção/prevenção & controle , Interferon gama/fisiologia , Infecções por Orthomyxoviridae/complicações , Oxazolidinonas/uso terapêutico , Pneumonia Pneumocócica/prevenção & controle , Acetamidas/administração & dosagem , Acetamidas/farmacologia , Animais , Antibacterianos/administração & dosagem , Antibacterianos/farmacologia , Carga Bacteriana , Líquido da Lavagem Broncoalveolar/química , Contagem de Linfócito CD4 , Suscetibilidade a Doenças , Relação Dose-Resposta a Droga , Avaliação Pré-Clínica de Medicamentos , Feminino , Vírus da Influenza A/isolamento & purificação , Vírus da Influenza A/fisiologia , Interferon gama/análise , Interferon gama/biossíntese , Interferon gama/genética , Interferon gama/uso terapêutico , Linezolida , Pulmão/microbiologia , Pulmão/virologia , Camundongos , Camundongos Endogâmicos C57BL , Oxazolidinonas/administração & dosagem , Oxazolidinonas/farmacologia , Pneumonia Pneumocócica/etiologia , Proteínas Recombinantes/uso terapêutico , Fator de Necrose Tumoral alfa/biossíntese , Fator de Necrose Tumoral alfa/genética , Carga Viral , Replicação Viral/efeitos dos fármacosRESUMO
Pneumocystis pneumonia was first diagnosed in malnourished children and has more recently been found in children with upper respiratory symptoms. We previously reported that there is a significant delay in the immune response in newborn mice infected with Pneumocystis compared to adults (Garvy BA, Harmsen AG, Infect. Immun. 64:3987-3992, 1996, and Garvy BA, Qureshi M, J. Immunol. 165:6480-6486, 2000). This delay is characterized by the failure of neonatal lungs to upregulate proinflammatory cytokines and attract T cells into the alveoli. Here, we report that regardless of the age at which we infected the mice, they failed to mount an inflammatory response in the alveolar spaces until they were 21 days of age or older. Anti-inflammatory cytokines had some role in dampening inflammation, since interleukin-10 (IL-10)-deficient pups cleared Pneumocystis faster than wild-type pups and the neutralization of transforming growth factor beta (TGF-ß) with specific antibody enhanced T cell migration into the lungs at later time points. However, the clearance kinetics were similar to those of control pups, suggesting that there is an intrinsic deficiency in the ability of innate immunity to control Pneumocystis. We found, using an adoptive transfer strategy, that the lung environment contributes to association of Pneumocystis organisms with alveolar macrophages, implying no intrinsic deficiency in the binding of Pneumocystis by neonatal macrophages. Using both in vivo and in vitro assays, we found that Pneumocystis organisms were less able to stimulate translocation of NF-κB to the nucleus of alveolar macrophages from neonatal mice. These data indicate that there is an early unresponsiveness of neonatal alveolar macrophages to Pneumocystis infection that is both intrinsic and related to the immunosuppressive environment found in neonatal lungs.
Assuntos
Imunidade Inata/fisiologia , Macrófagos Alveolares/microbiologia , Infecções por Pneumocystis/microbiologia , Pneumocystis/classificação , Animais , Animais Recém-Nascidos , Líquido da Lavagem Broncoalveolar/química , Regulação da Expressão Gênica/imunologia , Imunoglobulina G/análise , Imunoglobulina G/metabolismo , Interleucina-10/genética , Interleucina-10/metabolismo , Linfonodos , Camundongos , Camundongos Endogâmicos , Infecções por Pneumocystis/imunologia , Alvéolos Pulmonares/microbiologia , Linfócitos T/fisiologia , Fatores de Tempo , Fator de Crescimento Transformador beta/genética , Fator de Crescimento Transformador beta/metabolismoRESUMO
Age-associated defects in both B-lymphocytes and macrophages in elderly result in a reduction in the efficacy of vaccines to many Gram positive bacteria like Streptococcus pneumoniae. Splenic macrophages from aged mice have been shown to have a defect in production of pro-inflammatory cytokines (IL-6, IL-12, IL-1ß, TNF-α) but exhibit increased production of IL-10 upon TLR-4 ligation. Here we showed that aged macrophages demonstrate similar cytokine dysregulation phenotype upon stimulation with TLR-2 ligands, or killed S. pneumoniae. We hypothesized that an age-associated increase in activity of phosphatidyl inositol 3-kinase (PI3K)-Akt signaling pathway may be playing a causal role in the age-associated cytokine dysregulation. We found that gene expression of both the regulatory (p85ß) and the catalytic (p110δ) subunits of Class IA PI3K is higher in aged than in young splenic macrophages. The age-associated increase in the activity of PI3K was also demonstrated by an upregulation of P-Akt and its downstream target, glycogen synthase kinase-3 (GSK-3). Inhibition of PI3K enhanced induction of pro-inflammatory cytokines, by TLR-2/TLR-1, TLR-2/TLR-6 and TLR-4 ligands as well as heat killed S. pneumoniae (HKSP). Therefore, targeting PI3-Kinase could rescue cytokine dysregulation in aged macrophages and enhance the relevant pro-inflammatory cytokines needed to support B-cell activation and differentiation.