RESUMO
HLA transgenic mice are instrumental for evaluation of human-specific immune responses to viral infection. Mice do not develop COVID-19 upon infection with SARS-CoV-2 due to the strict tropism of the virus to the human ACE2 receptor. The aim of the current study was the implementation of an adenovirus-mediated infection protocol for human ACE2 expression in HLA transgenic mice. Transient pulmonary expression of the human ACE2 receptor in these mice results in their sensitisation to SARS-CoV-2 infection, consequently providing a valuable animal model for COVID-19. Infection results in a transient loss in body weight starting 3 days post-infection, reaching 20-30% loss of weight at day 7 and full recovery at days 11-13 post-infection. The evolution of the disease revealed high reproducibility and very low variability among individual mice. The method was implemented in two different strains of HLA immunized mice. Infected animals developed strong protective humoral and cellular immune responses specific to the viral spike-protein, strictly depending on the adenovirus-mediated human ACE2 expression. Convalescent animals were protected against a subsequent re-infection with SARS-CoV-2, demonstrating that the model may be applied for assessment of efficacy of anti-viral immune responses.
RESUMO
Mice are normally unaffected by SARS coronavirus 2 (SARS-CoV-2) infection since the virus does not bind effectively to the murine version of the angiotensin-converting enzyme 2 (ACE2) receptor molecule. Here, we report that induced mild pulmonary morbidities rendered SARS-CoV-2-refractive CD-1 mice susceptible to this virus. Specifically, SARS-CoV-2 infection after application of low doses of the acute lung injury stimulants bleomycin or ricin caused severe disease in CD-1 mice, manifested by sustained body weight loss and mortality rates greater than 50%. Further studies revealed markedly higher levels of viral RNA in the lungs, heart, and serum of low-dose ricin-pretreated mice compared with non-pretreated mice. Furthermore, lung extracts prepared 2-3 days after viral infection contained subgenomic mRNA and virus particles capable of replication only when derived from the pretreated mice. The deleterious effects of SARS-CoV-2 infection were effectively alleviated by passive transfer of polyclonal or monoclonal antibodies generated against the SARS-CoV-2 receptor binding domain (RBD). Thus, viral cell entry in the sensitized mice seems to depend on viral RBD binding, albeit by a mechanism other than the canonical ACE2-mediated uptake route. This unique mode of viral entry, observed over a mildly injured tissue background, may contribute to the exacerbation of coronavirus disease 2019 (COVID-19) pathologies in patients with preexisting morbidities.
Assuntos
Bleomicina/toxicidade , COVID-19/patologia , Lesão Pulmonar , Ricina/toxicidade , Animais , Chlorocebus aethiops , Comorbidade , Modelos Animais de Doenças , Feminino , Lesão Pulmonar/induzido quimicamente , Lesão Pulmonar/virologia , Camundongos , Células Vero , Ligação Viral , Internalização do Vírus/efeitos dos fármacosRESUMO
Emerging evidence suggests that immunological mechanisms underlie metabolic control of adipose tissue. Here, we have shown the regulatory impact of a rare subpopulation of dendritic cells, rich in perforin-containing granules (perf-DCs). Using bone marrow transplantation to generate animals selectively lacking perf-DCs, we found that these chimeras progressively gained weight and exhibited features of metabolic syndrome. This phenotype was associated with an altered repertoire of T cells residing in adipose tissue and could be completely prevented by T cell depletion in vivo. A similar impact of perf-DCs on inflammatory T cells was also found in a well-defined model of multiple sclerosis, experimental autoimmune encephlalomyelitis (EAE). Thus, perf-DCs probably represent a regulatory cell subpopulation critical for protection from metabolic syndrome and autoimmunity.
Assuntos
Autoimunidade/imunologia , Linfócitos T CD8-Positivos/imunologia , Células Dendríticas/imunologia , Inflamação/imunologia , Síndrome Metabólica/imunologia , Proteínas Citotóxicas Formadoras de Poros/análise , Tecido Adiposo/imunologia , Tecido Adiposo/metabolismo , Tecido Adiposo/patologia , Transferência Adotiva , Animais , Antígenos de Diferenciação/análise , Antígeno CD11c/análise , Linfócitos T CD8-Positivos/patologia , Linfócitos T CD8-Positivos/transplante , Células Clonais/imunologia , Grânulos Citoplasmáticos/química , Células Dendríticas/classificação , Células Dendríticas/ultraestrutura , Dieta Hiperlipídica/efeitos adversos , Encefalomielite Autoimune Experimental/imunologia , Encefalomielite Autoimune Experimental/patologia , Feminino , Inflamação/patologia , Depleção Linfocítica , Masculino , Síndrome Metabólica/etiologia , Síndrome Metabólica/patologia , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Obesidade/imunologia , Obesidade/patologia , Fenótipo , Proteínas Citotóxicas Formadoras de Poros/deficiência , Proteínas Citotóxicas Formadoras de Poros/genética , Quimera por Radiação , Tolerância a Antígenos Próprios/imunologiaRESUMO
Inflammatory bowel diseases (IBDs) including Crohn's disease and ulcerative colitis represent a major challenge to clinicians and immunologists trying to understand why in certain individuals the peaceful coexistence of the commensal microflora and its host breaks down and results in chronic inflammation. Here we summarize the recent progress in our understanding of the organization of the intestinal mononuclear phagocytes with dendritic cells and macrophages of distinct phenotype, origin and function. Finally, we discuss potential strategies to translate the recent findings into the management of chronic inflammation in animal models of IBD.
Assuntos
Células Dendríticas/imunologia , Doenças Inflamatórias Intestinais/imunologia , Doenças Inflamatórias Intestinais/terapia , Intestinos/citologia , Intestinos/imunologia , Macrófagos/imunologia , Animais , Humanos , Baço/imunologiaRESUMO
Classical DC (cDC) are required for efficient protective T-cell immunity. Moreover, recent data indicate that cDC also play a critical role in mediating homeostatic proliferation and maintenance of peripheral Treg. Here, we corroborate these findings by defining CD80/CD86 costimulation as an essential molecular component required for the cDC-Treg interactions. In contrast to earlier reports, the reduced Treg compartment of mice lacking cDC or selective CD80/86 expression on cDC, as such, did not render the respective animals prone to systemic lymphocyte hyperactivation or autoimmunity. Rather, we provide evidence that elevated immunoglobulin titers, as well as changes in T-cell subset prevalence and activation status are strictly associated with the nonmalignant myeloproliferative disorder triggered by the absence of cDC.
Assuntos
Antígeno B7-1/metabolismo , Antígeno B7-2/metabolismo , Células Dendríticas/citologia , Células Dendríticas/imunologia , Ativação Linfocitária/imunologia , Linfócitos T Reguladores/citologia , Linfócitos T Reguladores/imunologia , Animais , Anticorpos/sangue , Autoimunidade/imunologia , Antígeno B7-1/genética , Antígeno B7-2/genética , Transplante de Medula Óssea , Linfócitos T CD4-Positivos/imunologia , Linfócitos T CD4-Positivos/metabolismo , Contagem de Células , Quimera/imunologia , Células Dendríticas/metabolismo , Fatores de Transcrição Forkhead/metabolismo , Tolerância Imunológica/imunologia , Subunidade alfa de Receptor de Interleucina-2/metabolismo , Melanoma Experimental/metabolismo , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Camundongos Transgênicos , Transtornos Mieloproliferativos/etiologia , Transtornos Mieloproliferativos/imunologia , Subpopulações de Linfócitos T/imunologia , Subpopulações de Linfócitos T/metabolismo , Linfócitos T Reguladores/metabolismo , Tirosina Quinase 3 Semelhante a fms/metabolismoRESUMO
Dendritic cells are critically involved in the promotion and regulation of T cell responses. Here, we report a mouse strain that lacks conventional CD11c(hi) dendritic cells (cDCs) because of constitutive cell-type specific expression of a suicide gene. As expected, cDC-less mice failed to mount effective T cell responses resulting in impaired viral clearance. In contrast, neither thymic negative selection nor T regulatory cell generation or T cell homeostasis were markedly affected. Unexpectedly, cDC-less mice developed a progressive myeloproliferative disorder characterized by prominent extramedullary hematopoiesis and increased serum amounts of the cytokine Flt3 ligand. Our data identify a critical role of cDCs in the control of steady-state hematopoiesis, revealing a feedback loop that links peripheral cDCs to myelogenesis through soluble growth factors, such as Flt3 ligand.