RESUMO
Ageing of the immune system is characterized by decreased lymphopoiesis and adaptive immunity, and increased inflammation and myeloid pathologies1,2. Age-related changes in populations of self-renewing haematopoietic stem cells (HSCs) are thought to underlie these phenomena3. During youth, HSCs with balanced output of lymphoid and myeloid cells (bal-HSCs) predominate over HSCs with myeloid-biased output (my-HSCs), thereby promoting the lymphopoiesis required for initiating adaptive immune responses, while limiting the production of myeloid cells, which can be pro-inflammatory4. Ageing is associated with increased proportions of my-HSCs, resulting in decreased lymphopoiesis and increased myelopoiesis3,5,6. Transfer of bal-HSCs results in abundant lymphoid and myeloid cells, a stable phenotype that is retained after secondary transfer; my-HSCs also retain their patterns of production after secondary transfer5. The origin and potential interconversion of these two subsets is still unclear. If they are separate subsets postnatally, it might be possible to reverse the ageing phenotype by eliminating my-HSCs in aged mice. Here we demonstrate that antibody-mediated depletion of my-HSCs in aged mice restores characteristic features of a more youthful immune system, including increasing common lymphocyte progenitors, naive T cells and B cells, while decreasing age-related markers of immune decline. Depletion of my-HSCs in aged mice improves primary and secondary adaptive immune responses to viral infection. These findings may have relevance to the understanding and intervention of diseases exacerbated or caused by dominance of the haematopoietic system by my-HSCs.
Assuntos
Imunidade Adaptativa , Envelhecimento , Linhagem da Célula , Células-Tronco Hematopoéticas , Linfócitos , Células Mieloides , Rejuvenescimento , Animais , Feminino , Masculino , Camundongos , Imunidade Adaptativa/imunologia , Envelhecimento/imunologia , Linfócitos B/citologia , Linfócitos B/imunologia , Células-Tronco Hematopoéticas/citologia , Células-Tronco Hematopoéticas/imunologia , Inflamação/imunologia , Inflamação/patologia , Linfócitos/citologia , Linfócitos/imunologia , Linfopoese , Células Mieloides/citologia , Células Mieloides/imunologia , Mielopoese , Fenótipo , Linfócitos T/citologia , Linfócitos T/imunologia , Vírus/imunologiaRESUMO
The most recent Sudan virus (SUDV) outbreak in Uganda was first detected in September 2022 and resulted in 164 laboratory-confirmed cases and 77 deaths. There are no approved vaccines against SUDV. Here, we investigated the protective efficacy of ChAdOx1-biEBOV in cynomolgus macaques using a prime or a prime-boost regimen. ChAdOx1-biEBOV is a replication-deficient simian adenovirus vector encoding SUDV and Ebola virus (EBOV) glycoproteins (GPs). Intramuscular vaccination induced SUDV and EBOV GP-specific IgG responses and neutralizing antibodies. Upon challenge with SUDV, vaccinated animals showed signs of disease like those observed in control animals, and no difference in survival outcomes were measured among all three groups. Viral load in blood samples and in tissue samples obtained after necropsy were not significantly different between groups. Overall, this study highlights the importance of evaluating vaccines in multiple animal models and demonstrates the importance of understanding protective efficacy in both animal models and human hosts.
RESUMO
CD47 is an important innate immune checkpoint through its interaction with its inhibitory receptor on macrophages, signal-regulatory protein α (SIRPα). Therapeutic blockade of CD47-SIRPα interactions is a promising immuno-oncology treatment that promotes clearance of cancer cells. However, CD47-SIRPα interactions also maintain homeostatic lymphocyte levels. In this study, we report that the mouse splenic marginal zone B cell population is dependent on intact CD47-SIRPα interactions and blockade of CD47 leads to the loss of these cells. This depletion is accompanied by elevated levels of monocyte-recruiting chemokines CCL2 and CCL7 and infiltration of CCR2+Ly6Chi monocytes into the mouse spleen. In the absence of CCR2 signaling, there is no infiltration and reduced marginal zone B cell depletion. These data suggest that CD47 blockade leads to clearance of splenic marginal zone B cells.
Assuntos
Antígeno CD47 , Monócitos , Animais , Antígenos de Diferenciação , Quimiocinas , Camundongos , Monócitos/metabolismo , Fagocitose , Receptores ImunológicosRESUMO
The recent association between Zika virus (ZIKV) and neurologic complications, including Guillain-Barré syndrome in adults and CNS abnormalities in fetuses, highlights the importance in understanding the immunological mechanisms controlling this emerging infection. Studies have indicated that ZIKV evades the human type I IFN response, suggesting a role for the adaptive immune response in resolving infection. However, the inability of ZIKV to antagonize the mouse IFN response renders the virus highly susceptible to circulating IFN in murine models. Thus, as we show in this article, although wild-type C57BL/6 mice mount cell-mediated and humoral adaptive immune responses to ZIKV, these responses were not required to prevent disease. However, when the type I IFN response of mice was suppressed, then the adaptive immune responses became critical. For example, when type I IFN signaling was blocked by Abs in Rag1-/- mice, the mice showed dramatic weight loss and ZIKV infection in the brain and testes. This phenotype was not observed in Ig-treated Rag1-/- mice or wild-type mice treated with anti-type I IFNR alone. Furthermore, we found that the CD8+ T cell responses of pregnant mice to ZIKV infection were diminished compared with nonpregnant mice. It is possible that diminished cell-mediated immunity during pregnancy could increase virus spread to the fetus. These results demonstrate an important role for the adaptive immune response in the control of ZIKV infection and imply that vaccination may prevent ZIKV-related disease, particularly when the type I IFN response is suppressed as it is in humans.
Assuntos
Imunidade Adaptativa , Encéfalo/virologia , Linfócitos T CD8-Positivos/virologia , Complicações Infecciosas na Gravidez/imunologia , Testículo/virologia , Infecção por Zika virus/imunologia , Zika virus/imunologia , Animais , Anticorpos Bloqueadores/administração & dosagem , Encéfalo/imunologia , Linfócitos T CD8-Positivos/imunologia , Modelos Animais de Doenças , Feminino , Proteínas de Homeodomínio/genética , Humanos , Evasão da Resposta Imune , Interferon Tipo I/imunologia , Interferon Tipo I/metabolismo , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Gravidez/imunologia , Testículo/imunologia , Infecção por Zika virus/epidemiologiaRESUMO
BACKGROUND: La Crosse Virus (LACV) is a primary cause of pediatric viral encephalitis in the USA and can result in severe clinical outcomes. Almost all cases of LACV encephalitis occur in children 16 years or younger, indicating an age-related susceptibility. This susceptibility is recapitulated in a mouse model where weanling (3 weeks old or younger) mice are susceptible to LACV-induced disease, and adults (greater than 6 weeks) are resistant. Disease in mice and humans is associated with infiltrating leukocytes to the CNS. However, what cell types are infiltrating into the brain during virus infection and how these cells influence pathogenesis remain unknown. METHODS: In the current study, we analyzed lymphocytes recruited to the CNS during LACV-infection in clinical mice, using flow cytometry. We analyzed the contribution of these lymphocytes to LACV pathogenesis in weanling mice using knockout mice or antibody depletion. Additionally, we studied at the potential role of these lymphocytes in preventing LACV neurological disease in resistant adult mice. RESULTS: In susceptible weanling mice, disease was associated with infiltrating lymphocytes in the CNS, including NK cells, CD4 T cells, and CD8 T cells. Surprisingly, depletion of these cells did not impact neurological disease, suggesting these cells do not contribute to virus-mediated damage. In contrast, in disease-resistant adult animals, depletion of both CD4 T cells and CD8 T cells or depletion of B cells increased neurological disease, with higher levels of virus in the brain. CONCLUSIONS: Our current results indicate that lymphocytes do not influence neurological disease in young mice, but they have a critical role protecting adult animals from LACV pathogenesis. Although LACV is an acute virus infection, these studies indicate that the innate immune response in adults is not sufficient for protection and that components of the adaptive immune response are necessary to prevent virus from invading the CNS.
Assuntos
Encefalite da Califórnia/imunologia , Linfócitos/imunologia , Animais , Modelos Animais de Doenças , Vírus La Crosse , Camundongos , Camundongos Endogâmicos C57BL , Camundongos KnockoutRESUMO
Vß5(+) regulatory T cells (Tregs), which are specific for a mouse endogenous retroviral superantigen, become activated and proliferate in response to Friend virus (FV) infection. We previously reported that FV-induced expansion of this Treg subset was dependent on CD8(+) T cells and TNF-α, but independent of IL-2. We now show that the inflammatory milieu associated with FV infection is not necessary for induction of Vß5(+) Treg expansion. Rather, it is the presence of activated CD8(+) T cells that is critical for their expansion. The data indicate that the mechanism involves signaling between the membrane-bound form of TNF-α on activated CD8(+) T cells and TNFR2 on Tregs. CD8(+) T cells expressing membrane-bound TNF-α but no soluble TNF-α remained competent to induce strong Vß5(+) Treg expansion in vivo. In addition, Vß5(+) Tregs expressing only TNFR2 but no TNFR1 were still responsive to expansion. Finally, treatment of naive mice with soluble TNF-α did not induce Vß5(+) Treg expansion, but treatment with a TNFR2-specific agonist did. These results reveal a new mechanism of intercellular communication between activated CD8(+) T cell effectors and Tregs that results in the activation and expansion of a Treg subset that subsequently suppresses CD8(+) T cell functions.
Assuntos
Linfócitos T CD8-Positivos/imunologia , Ativação Linfocitária/imunologia , Receptores de Antígenos de Linfócitos T alfa-beta/biossíntese , Receptores Tipo II do Fator de Necrose Tumoral/imunologia , Fator de Necrose Tumoral alfa/biossíntese , Animais , Proteínas de Transporte/genética , Feminino , Vírus da Leucemia Murina de Friend/imunologia , Leucemia Experimental/imunologia , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Receptores Tipo I de Fatores de Necrose Tumoral , Receptores Tipo II do Fator de Necrose Tumoral/agonistas , Infecções por Retroviridae/imunologia , Transdução de Sinais/imunologia , Linfócitos T Reguladores/imunologia , Infecções Tumorais por Vírus/imunologiaRESUMO
Friend virus infection of mice induces the expansion and activation of regulatory T cells (Tregs) that dampen acute immune responses and promote the establishment and maintenance of chronic infection. Adoptive transfer experiments and the expression of neuropilin-1 indicate that these cells are predominantly natural Tregs rather than virus-specific conventional CD4(+) T cells that converted into induced Tregs. Analysis of Treg TCR Vß chain usage revealed a broadly distributed polyclonal response with a high proportionate expansion of the Vß5(+) Treg subset, which is known to be responsive to endogenous retrovirus-encoded superantigens. In contrast to the major population of Tregs, the Vß5(+) subset expressed markers of terminally differentiated effector cells, and their expansion was associated with the level of the antiviral CD8(+) T cell response rather than the level of Friend virus infection. Surprisingly, the expansion and accumulation of the Vß5(+) Tregs was IL-2 independent but dependent on TNF-α. These experiments reveal a subset-specific Treg induction by a new pathway.
Assuntos
Vírus da Leucemia Murina de Friend/imunologia , Interleucina-2/imunologia , Receptores de Antígenos de Linfócitos T alfa-beta/metabolismo , Infecções por Retroviridae/imunologia , Linfócitos T Reguladores/citologia , Linfócitos T Reguladores/imunologia , Fator de Necrose Tumoral alfa/imunologia , Animais , Linfócitos B/imunologia , Linfócitos B/metabolismo , Linfócitos T CD8-Positivos/imunologia , Linfócitos T CD8-Positivos/metabolismo , Células Dendríticas/imunologia , Células Dendríticas/metabolismo , Feminino , Imunofenotipagem , Interleucina-2/metabolismo , Camundongos , Fenótipo , Linfócitos T Reguladores/metabolismo , Fator de Necrose Tumoral alfa/metabolismo , Infecções Tumorais por Vírus/imunologiaRESUMO
The immune system is tasked with defending against a myriad of microbial infections, and its response to a given infectious microbe may be strongly influenced by coinfection with another microbe. It was shown that infection of mice with lactate dehydrogenase-elevating virus (LDV) impairs early adaptive immune responses to Friend virus (FV) coinfection. To investigate the mechanism of this impairment, we examined LDV-induced innate immune responses and found LDV-specific induction of IFN-α and IFN-γ. LDV-induced IFN-α had little effect on FV infection or immune responses, but unexpectedly, LDV-induced IFN-γ production dampened Th1 adaptive immune responses and enhanced FV infection. Two distinct effects were identified. First, LDV-induced IFN-γ signaling indirectly modulated FV-specific CD8+ T cell responses. Second, intrinsic IFN-γ signaling in B cells promoted polyclonal B cell activation and enhanced early FV infection, despite promotion of germinal center formation and neutralizing Ab production. Results from this model reveal that IFN-γ production can have detrimental effects on early adaptive immune responses and virus control.
Assuntos
Imunidade Adaptativa , Regulação para Baixo/imunologia , Interferon gama/fisiologia , Vírus da Leucemia Murina/imunologia , Infecções por Retroviridae/imunologia , Imunidade Adaptativa/genética , Animais , Modelos Animais de Doenças , Regulação para Baixo/genética , Feminino , Vírus da Leucemia Murina de Friend/imunologia , Vírus da Leucemia Murina de Friend/patogenicidade , Interferon gama/deficiência , Interferon gama/genética , Vírus Elevador do Lactato Desidrogenase/imunologia , Vírus Elevador do Lactato Desidrogenase/patogenicidade , Vírus da Leucemia Murina/patogenicidade , Leucemia Experimental/genética , Leucemia Experimental/imunologia , Leucemia Experimental/virologia , Camundongos , Camundongos Congênicos , Camundongos Endogâmicos A , Camundongos Endogâmicos C57BL , Camundongos Knockout , Camundongos Mutantes , Infecções por Retroviridae/genética , Infecções por Retroviridae/patologia , Vírus Formadores de Foco no Baço/imunologia , Vírus Formadores de Foco no Baço/patogenicidade , Infecções Tumorais por Vírus/genética , Infecções Tumorais por Vírus/imunologia , Infecções Tumorais por Vírus/virologiaRESUMO
Although chronic infections with viruses such as HIV and hepatitis C virus have been associated with regulatory T cell (Treg)-mediated suppression of virus-specific CD8(+) T-cell activity, no causal relationship between Tregs and chronic viral set points has been established. Using transgenic mice in which Tregs can be selectively ablated, we now show that transient depletion of Tregs during a chronic retroviral infection allows exhausted CD8(+) T cells to regain antiviral functions, including secretion of cytokines, production of cytotoxic molecules, and virus-specific cytolytic activity. Furthermore, short-term Treg ablation resulted in long-term reductions in chronic virus loads. These results demonstrate that Treg-mediated immunosuppression can be a significant factor in the maintenance of chronic viral infections and that Treg-targeted immunotherapy could be a valuable component in therapeutic strategies to treat chronic infectious diseases.
Assuntos
Linfócitos T CD8-Positivos/imunologia , Depleção Linfocítica , Infecções por Retroviridae/imunologia , Linfócitos T Reguladores , Animais , Doença Crônica , Citocinas/imunologia , Camundongos , Camundongos TransgênicosRESUMO
The 2022 mpox virus (MPXV) outbreak was sustained by human-to-human transmission; however, it is currently unclear which factors lead to sustained transmission of MPXV. Here we present Mastomys natalensis as a model for MPXV transmission after intraperitoneal, rectal, vaginal, aerosol and transdermal inoculation with an early 2022 human outbreak isolate (Clade IIb). Virus shedding and tissue replication were route dependent and occurred in the presence of self-resolving localized skin, lung, reproductive tract or rectal lesions. Mucosal inoculation via the rectal, vaginal and aerosol routes led to increased shedding, replication and a pro-inflammatory T cell profile compared with skin inoculation. Contact transmission was higher from rectally inoculated animals. This suggests that transmission might be sustained by increased susceptibility of the anal and genital mucosae for infection and subsequent virus release.
Assuntos
Mpox , Mucosa , Eliminação de Partículas Virais , Animais , Feminino , Masculino , Modelos Animais de Doenças , Surtos de Doenças , Mucosa/virologia , Roedores/virologia , Vagina/virologia , Replicação Viral , Mpox/transmissão , Mpox/veterinária , Mpox/virologiaRESUMO
It was recently reported that inhibitory molecules such as programmed death-1 (PD-1) were upregulated on CD8(+) T cells during acute Friend retrovirus infection and that the cells were prematurely exhausted and dysfunctional in vitro. The current study confirms that most activated CD8(+) T cells upregulated expression of PD-1 during acute infection and revealed a dichotomy of function between PD-1(hi) and PD-1(lo) subsets. More PD-1(lo) cells produced antiviral cytokines such as IFN-γ and TNF-α, whereas more PD-1(hi) cells displayed characteristics of cytotoxic effectors such as production of granzymes and surface expression of CD107a. Importantly, CD8(+) T cells mediated rapid in vivo cytotoxicity and were critical for control of acute Friend virus replication. Thus, direct ex vivo analyses and in vivo experiments revealed high CD8(+) T cell functionality and indicate that PD-1 expression during acute infection is not a marker of T cell exhaustion.
Assuntos
Linfócitos T CD8-Positivos/imunologia , Leucemia Experimental/imunologia , Receptor de Morte Celular Programada 1/biossíntese , Infecções por Retroviridae/imunologia , Infecções Tumorais por Vírus/imunologia , Animais , Linfócitos T CD8-Positivos/metabolismo , Separação Celular , Citometria de Fluxo , Vírus da Leucemia Murina de Friend/imunologia , Leucemia Experimental/metabolismo , Ativação Linfocitária/imunologia , Camundongos , Camundongos Endogâmicos C57BL , Receptor de Morte Celular Programada 1/imunologia , Infecções por Retroviridae/metabolismo , Infecções Tumorais por Vírus/metabolismo , Regulação para CimaRESUMO
Infection of mice with Friend virus induces the activation of CD4(+) regulatory T cells (Tregs) that suppress virus-specific CD8(+) T cells. This suppression leads to incomplete virus clearance and the establishment of virus persistence. We now show that Treg-mediated suppression of CD8(+) T cells is tissue specific, occurring in the spleen but not the liver. Regardless of infection status, there was a 5-fold lower proportion of Tregs in the liver than in the spleen, much lower absolute cell numbers, and the relatively few Tregs present expressed less CD25. Results indicated that reduced expression of CD25 on liver Tregs was due to microenvironmental factors including low levels of IL-2 production by CD4(+) Th cells in that tissue. Low CD25 expression on liver Tregs did not impair their ability to suppress CD8(+) T cells in vitro. Correlating with the decreased proportion of Tregs in the liver was a significantly increased proportion of virus-specific CD8(+) T cells compared with the spleen. The virus-specific CD8(+) T cells from the liver did not appear suppressed given that they produced both IFN-gamma and granzyme B, and they also showed evidence of recent cytolytic activity (CD107a(+)). The functional phenotype of the virus-specific CD8(+) T cells correlated with a 10-fold reduction of chronic Friend virus levels in the liver compared with the spleen. Thus, suppression of CD8(+) T cells by virus-induced Tregs occurs in a tissue-specific manner and correlates with profound effects on localized levels of chronic infection.
Assuntos
Linfócitos T CD8-Positivos/imunologia , Infecções por Retroviridae/imunologia , Baço/imunologia , Linfócitos T Reguladores/imunologia , Animais , Doença Crônica , Vírus da Leucemia Murina de Friend , Leucemia Experimental , Camundongos , Especificidade de Órgãos , Baço/virologia , Infecções Tumorais por Vírus , Carga ViralRESUMO
Severe coronavirus disease 2019 (COVID-19) has been associated with T cell lymphopenia, but no causal effect of T cell deficiency on disease severity has been established. To investigate the specific role of T cells in recovery from severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections, we studied rhesus macaques that were depleted of either CD4+, CD8+, or both T cell subsets prior to infection. Peak virus loads were similar in all groups, but the resolution of virus in the T cell-depleted animals was slightly delayed compared to that in controls. The T cell-depleted groups developed virus-neutralizing antibody responses and class switched to IgG. When reinfected 6 weeks later, the T cell-depleted animals showed anamnestic immune responses characterized by rapid induction of high-titer virus-neutralizing antibodies, faster control of virus loads, and reduced clinical signs. These results indicate that while T cells play a role in the recovery of rhesus macaques from acute SARS-CoV-2 infections, their depletion does not induce severe disease, and T cells do not account for the natural resistance of rhesus macaques to severe COVID-19. Neither primed CD4+ nor CD8+ T cells appeared critical for immunoglobulin class switching, the development of immunological memory, or protection from a second infection. IMPORTANCE Patients with severe COVID-19 often have decreased numbers of T cells, a cell type important in fighting most viral infections. However, it is not known whether the loss of T cells contributes to severe COVID-19 or is a consequence of it. We studied rhesus macaques, which develop only mild COVID-19, similar to most humans. Experimental depletion of T cells slightly prolonged their clearance of virus, but there was no increase in disease severity. Furthermore, they were able to develop protection from a second infection and produced antibodies capable of neutralizing the virus. They also developed immunological memory, which allows a much stronger and more rapid response upon a second infection. These results suggest that T cells are not critical for recovery from acute SARS-CoV-2 infections in this model and point toward B cell responses and antibodies as the essential mediators of protection from re-exposure.
Assuntos
Anticorpos Neutralizantes/imunologia , Anticorpos Antivirais/imunologia , COVID-19/patologia , Memória Imunológica/imunologia , Linfopenia/imunologia , SARS-CoV-2/imunologia , Animais , Linfócitos T CD4-Positivos/citologia , Linfócitos T CD4-Positivos/imunologia , Linfócitos T CD8-Positivos/citologia , Linfócitos T CD8-Positivos/imunologia , COVID-19/imunologia , Feminino , Depleção Linfocítica/métodos , Macaca mulatta/imunologia , MasculinoRESUMO
Severe COVID-19 has been associated with T cell lymphopenia 1,2, but no causal effect of T cell deficiency on disease severity has been established. To investigate the specific role of T cells in recovery from SARS-CoV-2 infections we studied rhesus macaques that were depleted of either CD4+, CD8+ or both T cell subsets prior to infection. Peak virus loads were similar in all groups, but the resolution of virus in the T cell-depleted animals was slightly delayed compared to controls. The T cell-depleted groups developed virus-neutralizing antibody responses and also class-switched to IgG. When re-infected six weeks later, the T cell-depleted animals showed anamnestic immune responses characterized by rapid induction of high-titer virus-neutralizing antibodies, faster control of virus loads and reduced clinical signs. These results indicate that while T cells play a role in the recovery of rhesus macaques from acute SARS-CoV-2 infections, their depletion does not induce severe disease, and T cells do not account for the natural resistance of rhesus macaques to severe COVID-19. Neither primed CD4+ or CD8+ T cells appeared critical for immunoglobulin class switching, the development of immunological memory or protection from a second infection.
RESUMO
Paradoxically, early host responses to infection include the upregulation of the antiphagocytic molecule, CD47. This suggests that CD47 blockade could enhance antigen presentation and subsequent immune responses. Indeed, mice treated with anti-CD47 monoclonal antibody following lymphocytic choriomeningitis virus infections show increased activation of both macrophages and dendritic cells (DCs), enhancement of the kinetics and potency of CD8+ T cell responses, and significantly improved virus control. Treatment efficacy is critically dependent on both APCs and CD8+ T cells. In preliminary results from one of two cohorts of humanized mice infected with HIV-1 for 6 weeks, CD47 blockade reduces plasma p24 levels and restores CD4+ T cell counts. The results indicate that CD47 blockade not only enhances the function of innate immune cells but also links to adaptive immune responses through improved APC function. As such, immunotherapy by CD47 blockade may have broad applicability to treat a wide range of infectious diseases.
Assuntos
Antígeno CD47/imunologia , Antígeno CD47/metabolismo , Viroses/imunologia , Imunidade Adaptativa/imunologia , Animais , Linfócitos T CD8-Positivos/imunologia , Linhagem Celular , Feminino , Células HEK293 , Humanos , Imunidade Inata/imunologia , Imunoterapia/métodos , Coriomeningite Linfocítica/imunologia , Vírus da Coriomeningite Linfocítica/imunologia , Macrófagos/imunologia , Camundongos Endogâmicos C57BL , Camundongos Knockout , Transdução de SinaisRESUMO
It is well understood that the adaptive immune response to infectious agents includes a modulating suppressive component as well as an activating component. We now show that the very early innate response also has an immunosuppressive component. Infected cells upregulate the CD47 "don't eat me" signal, which slows the phagocytic uptake of dying and viable cells as well as downstream antigen-presenting cell (APC) functions. A CD47 mimic that acts as an essential virulence factor is encoded by all poxviruses, but CD47 expression on infected cells was found to be upregulated even by pathogens, including severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), that encode no mimic. CD47 upregulation was revealed to be a host response induced by the stimulation of both endosomal and cytosolic pathogen recognition receptors (PRRs). Furthermore, proinflammatory cytokines, including those found in the plasma of hepatitis C patients, upregulated CD47 on uninfected dendritic cells, thereby linking innate modulation with downstream adaptive immune responses. Indeed, results from antibody-mediated CD47 blockade experiments as well as CD47 knockout mice revealed an immunosuppressive role for CD47 during infections with lymphocytic choriomeningitis virus and Mycobacterium tuberculosis Since CD47 blockade operates at the level of pattern recognition receptors rather than at a pathogen or antigen-specific level, these findings identify CD47 as a novel potential immunotherapeutic target for the enhancement of immune responses to a broad range of infectious agents.IMPORTANCE Immune responses to infectious agents are initiated when a pathogen or its components bind to pattern recognition receptors (PRRs). PRR binding sets off a cascade of events that activates immune responses. We now show that, in addition to activating immune responses, PRR signaling also initiates an immunosuppressive response, probably to limit inflammation. The importance of the current findings is that blockade of immunomodulatory signaling, which is mediated by the upregulation of the CD47 molecule, can lead to enhanced immune responses to any pathogen that triggers PRR signaling. Since most or all pathogens trigger PRRs, CD47 blockade could be used to speed up and strengthen both innate and adaptive immune responses when medically indicated. Such immunotherapy could be done without a requirement for knowing the HLA type of the individual, the specific antigens of the pathogen, or, in the case of bacterial infections, the antimicrobial resistance profile.
Assuntos
Betacoronavirus/imunologia , Antígeno CD47/metabolismo , Imunomodulação/imunologia , Receptores de Reconhecimento de Padrão/imunologia , Células A549 , Imunidade Adaptativa/imunologia , Animais , Antígeno CD47/genética , Linhagem Celular Tumoral , Citocinas/imunologia , Feminino , Humanos , Imunidade Inata/imunologia , Vírus da Coriomeningite Linfocítica/imunologia , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Mycobacterium tuberculosis/imunologia , SARS-CoV-2 , Regulação para Cima/imunologiaRESUMO
Friend virus (FV) is a murine retrovirus that causes acute disease leading to lethal erythroleukemia in most strains of mice. Strains of mice that mount strong and rapid immune responses can recover from acute infection, but nevertheless develop life-long chronic infections. The study of this infection has revealed the types of immune responses required for both recovery from the acute phase and the control of the chronic phase of infection. This knowledge has led to vaccines and therapeutics to prevent and treat infections and associated disease states. The FV model has provided insights into immunological mechanisms found to be relevant to human infections with retroviruses such as HIV-1 and HTLV-1.
Assuntos
Vírus da Leucemia Murina de Friend/imunologia , Leucemia Experimental/imunologia , Infecções por Retroviridae/imunologia , Linfócitos T Reguladores/imunologia , Infecções Tumorais por Vírus/imunologia , Animais , Linfócitos T CD8-Positivos/imunologia , Linfócitos T CD8-Positivos/virologia , Modelos Animais de Doenças , Imunoterapia , Leucemia Experimental/virologia , Camundongos , Infecções por Retroviridae/virologia , Linfócitos T Reguladores/virologia , Infecções Tumorais por Vírus/virologia , Vacinas Virais/imunologiaRESUMO
Friend virus (FV) and lactate dehydrogenase-elevating virus (LDV) are endemic mouse viruses that can cause long-term chronic infections in mice. We found that numerous mouse-passaged FV isolates also contained LDV and that coinfection with LDV delayed FV-specific CD8(+) T-cell responses during acute infection. While LDV did not alter the type of acute pathology induced by FV, which was severe splenomegaly caused by erythroproliferation, the immunosuppression mediated by LDV increased both the severity and the duration of FV infection. Compared to mice infected with FV alone, those coinfected with both FV and LDV had delayed CD8(+) T-cell responses, as measured by FV-specific tetramers. This delayed response accounted for the prolonged and exacerbated acute phase of FV infection. Suppression of FV-specific CD8(+) T-cell responses occurred not only in mice infected concomitantly with LDV but also in mice chronically infected with LDV 8 weeks prior to infection with FV. The LDV-induced suppression was not mediated by T regulatory cells, and no inhibition of the CD4(+) T-cell or antibody responses was observed. Considering that most human adults are carriers of chronically infectious viruses at the time of new virus insults and that coinfections with viruses such as human immunodeficiency virus and hepatitis C virus are currently epidemic, it is of great interest to determine how infection with one virus may impact host responses to a second infection. Coinfection of mice with LDV and FV provides a well-defined, natural host model for such studies.
Assuntos
Linfócitos T CD8-Positivos/imunologia , Vírus da Leucemia Murina de Friend/imunologia , Tolerância Imunológica , Vírus Elevador do Lactato Desidrogenase/imunologia , Animais , Anticorpos Antivirais/imunologia , Linfócitos T CD4-Positivos/imunologia , Feminino , Leucemia Eritroblástica Aguda/virologia , Leucemia Experimental/virologia , Camundongos , Camundongos Endogâmicos C57BL , Infecções por Retroviridae/imunologia , Infecções por Retroviridae/patologia , Esplenomegalia/virologia , Linfócitos T Reguladores/imunologia , Infecções Tumorais por Vírus/imunologia , Infecções Tumorais por Vírus/patologiaRESUMO
Prolonged exposure of CD8+ T cells to antigenic stimulation, as in chronic viral infections, leads to a state of diminished function termed exhaustion. We now demonstrate that even during exhaustion there is a subset of functional CD8+ T cells defined by surface expression of SIRPα, a protein not previously reported on lymphocytes. On SIRPα+ CD8+ T cells, expression of co-inhibitory receptors is counterbalanced by expression of co-stimulatory receptors and it is only SIRPα+ cells that actively proliferate, transcribe IFNγ and show cytolytic activity. Furthermore, target cells that express the ligand for SIRPα, CD47, are more susceptible to CD8+ T cell-killing in vivo. SIRPα+ CD8+ T cells are evident in mice infected with Friend retrovirus, LCMV Clone 13, and in patients with chronic HCV infections. Furthermore, therapeutic blockade of PD-L1 to reinvigorate CD8+ T cells during chronic infection expands the cytotoxic subset of SIRPα+ CD8+ T cells.
Assuntos
Infecções por Arenaviridae/imunologia , Linfócitos T CD8-Positivos/imunologia , Coriomeningite Linfocítica/imunologia , Vírus da Coriomeningite Linfocítica/imunologia , Receptores Imunológicos/imunologia , Animais , Infecções por Arenaviridae/genética , Infecções por Arenaviridae/virologia , Linfócitos T CD8-Positivos/metabolismo , Linfócitos T CD8-Positivos/virologia , Feminino , Expressão Gênica/imunologia , Perfilação da Expressão Gênica , Interações Hospedeiro-Patógeno/imunologia , Humanos , Ativação Linfocitária/genética , Ativação Linfocitária/imunologia , Coriomeningite Linfocítica/genética , Coriomeningite Linfocítica/virologia , Vírus da Coriomeningite Linfocítica/fisiologia , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Receptores Imunológicos/genética , Receptores Imunológicos/metabolismo , Linfócitos T Citotóxicos/imunologia , Linfócitos T Citotóxicos/metabolismo , Linfócitos T Citotóxicos/virologiaRESUMO
Published data show that murine bone marrow-derived macrophages (BMDM) restrict growth of avirulent phase II, but not virulent phase I, Coxiella burnetii. Growth restriction of phase II bacteria is thought to result from potentiated recognition of pathogen-associated molecular patterns, which leads to production of inhibitory effector molecules. Past studies have used conditioned medium from L-929 murine fibroblasts as a source of macrophage-colony stimulating factor (M-CSF) to promote differentiation of bone marrow-derived myeloid precursors into macrophages. However, uncharacterized components of conditioned medium, such as variable amounts of type I interferons, can affect macrophage activation status and their permissiveness for infection. In the current study, we show that the C. burnetii Nine Mile phase II (NMII) strain grows robustly in primary macrophages from C57BL/6J mice when bone marrow cells are differentiated with recombinant murine M-CSF (rmM-CSF). Bacteria were readily internalized by BMDM, and replicated within degradative, LAMP1-positive vacuoles to achieve roughly 3 logs of growth over 6 days. Uninfected BMDM did not appreciably express CD38 or Egr2, markers of classically (M1) and alternatively (M2) activated macrophages, respectively, nor did infection change the lack of polarization. In accordance with an M0 phenotype, infected BMDM produced moderate amounts of TNF and nitric oxide. Similar NMII growth results were obtained using C57BL/6J myeloid progenitors immortalized with an estrogen-regulated Hoxb8 (ER-Hoxb8) oncogene. To demonstrate the utility of the ER-Hoxb8 system, myeloid progenitors from natural resistance-associated macrophage protein 1 (Nramp1) C57BL/6J knock-in mice were transduced with ER-Hoxb8, and macrophages were derived from immortalized progenitors using rmM-CSF and infected with NMII. No difference in growth was observed when compared to macrophages from wild type mice, indicating depletion of metal ions by the Nramp1 transporter does not negatively impact NMII growth. Results with NMII were recapitulated in primary macrophages where C57BL/6J Nramp1+ BMDM efficiently killed Salmonella enterica serovar Typhimurium. M-CSF differentiated murine macrophages from bone marrow and conditional ER-Hoxb8 myeloid progenitors will be useful ex vivo models for studying Coxiella-macrophage interactions.