RESUMO
The CD8(+) T cell diaspora has been analyzed after secondary challenge with an influenza A virus that replicates only in the respiratory tract. Numbers of D(b)NP(366)- and D(b)PA(224)-specific CD8(+) T cells were measured by tetramer staining at the end of the recall response, then followed sequentially in the lung, lymph nodes, spleen, blood, and other organs. The extent of clonal expansion did not reflect the sizes of the preexisting memory T cell pools. Although the high-frequency CD8(+) tetramer(+) populations in the pneumonic lung and mediastinal lymph nodes fell rapidly from peak values, the "whole mouse" virus-specific CD8(+) T cell counts decreased only 2-fold over the 4 weeks after infection, then subsided at a fairly steady rate to reach a plateau at about 2 months. The largest numbers were found throughout in the spleen, then the bone marrow. The CD8(+)D(b)NP(366)+ and CD8(+)D(b)PA(224)+ sets remained significantly enlarged for at least 4 months, declining at equivalent rates while retaining the nucleoprotein > acid polymerase immunodominance hierarchy characteristic of the earlier antigen-driven phase. Lowest levels of the CD69 "activation marker" were detected consistently on virus-specific CD8(+) T cells in the blood, then the spleen. Those in the bone marrow and liver were intermediate, and CD69(hi) T cells were very prominent in the regional lymph nodes and the nasal-associated lymphoid tissue. Any population of "resting" CD8(+) memory T cells is thus phenotypically heterogeneous, widely dispersed, and subject to broad homeostatic and local environmental effects irrespective of epitope specificity or magnitude.
Assuntos
Antígenos Virais/imunologia , Linfócitos T CD8-Positivos/imunologia , RNA Polimerases Dirigidas por DNA/imunologia , Vírus da Influenza A/imunologia , Fragmentos de Peptídeos/imunologia , RNA Polimerase Dependente de RNA , Proteínas do Core Viral/imunologia , Proteínas Virais/imunologia , Animais , Antígenos CD , Antígenos de Diferenciação de Linfócitos T , Feminino , Antígenos H-2/imunologia , Antígeno de Histocompatibilidade H-2D , Humanos , Memória Imunológica/imunologia , Cinética , Lectinas Tipo C , Tecido Linfoide/imunologia , Camundongos , Camundongos Endogâmicos C57BL , Peptídeos/imunologia , Mucosa Respiratória/imunologia , Distribuição TecidualRESUMO
The murine gamma-herpesvirus 68 (MHV-68) provides a unique experimental model for dissecting immunity to large DNA viruses that persist in B lymphocytes. The analysis is greatly facilitated by the availability of genetically disrupted (-/-) mice that lack key host-response elements, and by the fact that MHV-68 is a lytic virus that can readily be manipulated for mutational analysis. The mutant virus strategy is being used, for example, to characterize the part played in vivo by an MHV-68-encoded chemokine-binding protein that may ultimately find an application in human therapeutics. Experiments with various -/- mice and monoclonal antibody depletion protocols have shown very clearly that type I interferons (IFNs) are essential for the early control of MHV-68 replication, while CD4+ T cells producing IFN-gamma function to limit the consequences of viral persistence. Virus-specific CD8+ effectors acting in the absence of the CD4+ subset seem initially to control the lytic phase in the lung following respiratory challenge, but are then unable to prevent the reactivation of replicative infection in epithelia and the eventual death of CD4+ T-cell-deficient mice. This could reflect the fact that the interaction between the CD8+ T cells and the virus-infected targets is partially compromised by the MHV-68 K3 protein, which inhibits antigen presentation by MHC class I glycoproteins. Immunization strategies focusing on the CD8+ T-cell response to epitopes expressed during the lytic phase of MHV-68 infection can limit virus replication, but are unable to prevent the establishment of latency. Other experiments with mutant viruses also suggest that there is a disconnection between lytic MHV-68 infection and latency. The massive nonspecific immunoglobulin response and the dramatic expansion of Vbeta4+ CD8+ T cells, which is apparently MHC independent, could represent some sort of 'smoke screen' used by MHV-68 to subvert immunity. Although MHV-68 is neither Epstein-Barr virus nor human herpesvirus-8, the results generated from this system suggest possibilities that may usefully be addressed with these human pathogens. Perhaps the main lesson learned to date is that all the components of immunity are likely to be important for the control of these complex viruses.
Assuntos
Gammaherpesvirinae/imunologia , Infecções por Herpesviridae/imunologia , Infecções Tumorais por Vírus/imunologia , Animais , Linfócitos B/imunologia , Linfócitos T CD4-Positivos/imunologia , Linfócitos T CD8-Positivos/imunologia , Quimiocinas/imunologia , Citocinas/imunologia , Infecções por Herpesviridae/patologia , Infecções por Herpesviridae/prevenção & controle , Infecções por Herpesviridae/virologia , Humanos , Imunização , Infecções Tumorais por Vírus/patologia , Infecções Tumorais por Vírus/prevenção & controle , Infecções Tumorais por Vírus/virologiaRESUMO
Many receptors activate phospholipase Cgamma1 or -gamma2. To assess the role of PLCgamma2, we derived enzyme-deficient mice. The mice are viable but have decreased mature B cells, a block in pro-B cell differentiation, and B1 B cell deficiency. IgM receptor-induced Ca2+ flux and proliferation to B cell mitogens are absent. IgM, IgG2a, and IgG3 levels are reduced, and T cell-independent antibody production is absent. The similarity to Btk- or Blnk-deficient mice demonstrates that PLCgamma2 is downstream in Btk/Blnk signaling. FcRgamma signaling is also defective, resulting in a loss of collagen-induced platelet aggregation, mast cell FcepsilonR function, and NK cell FcgammaRIII and 2B4 function. The results define a signal transduction pathway broadly utilized by immunoglobulin superfamily receptors.
Assuntos
Linfócitos B/fisiologia , Isoenzimas/fisiologia , Receptores de IgG/fisiologia , Fosfolipases Tipo C/fisiologia , Proteínas Adaptadoras de Transdução de Sinal , Tirosina Quinase da Agamaglobulinemia , Animais , Linfócitos B/metabolismo , Plaquetas/fisiologia , Proteínas de Transporte/metabolismo , Hematopoese/fisiologia , Isoenzimas/genética , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Fosfolipase C gama , Fosfoproteínas/metabolismo , Proteínas Tirosina Quinases/metabolismo , Receptores de Antígenos de Linfócitos B/metabolismo , Receptores de IgG/metabolismo , Fosfolipases Tipo C/genéticaRESUMO
Respiratory challenge of mice with murine gammaherpesvirus 68 (gammaHV68) results in acute replication in respiratory epithelial cells and persistent, latent infection of B cells and macrophages. gammaHV68 elicits virus-specific Ab, and also nonspecifically activates B cells to Ab production through a CD4+ T cell-dependent process. The current analysis characterizes virus-specific and nonspecific Ab production at the single cell level and investigates the requirements and nature of the nonspecific response. Virus-specific Ab-forming cell (AFC) numbers were dwarfed by the increase in total AFC in all sites examined, indicating substantial nonspecific Ab production. Clear increases and decreases in specific and total AFC numbers occurred in the lymph nodes draining the respiratory tract and the spleen, but AFC numbers in the bone marrow (BM) increased to a plateau and remained constant. The longevity of the BM response was reflected in a sustained increase in virus-specific and total serum Ab levels. Generally, the IgG2a and IgG2b isotypes predominated. Analysis of cytokine-deficient mice, CD40 ligand-deficient mice, and radiation BM chimeras lacking MHC class II expression specifically on B cells indicated that nonspecific Ab production is independent of IL-6 or IFN-gamma, and dependent on cognate CD4+ T cell help. Several observations were consistent with polyclonal B cell activation by gammaHV68, including the induction of durable serum levels of IgG reactive with mammalian dsDNA and murine type II collagen. Our findings indicate new directions for studies of this valuable model of gamma-herpesvirus pathogenesis.
Assuntos
Especificidade de Anticorpos , Linfócitos B/imunologia , Linfócitos B/virologia , Gammaherpesvirinae/imunologia , Infecções por Herpesviridae/imunologia , Animais , Anticorpos Antivirais/biossíntese , Anticorpos Antivirais/sangue , Células Produtoras de Anticorpos/metabolismo , Autoanticorpos/biossíntese , Linfócitos B/metabolismo , Células da Medula Óssea/imunologia , Células da Medula Óssea/metabolismo , Células Clonais , Citocinas/deficiência , Citocinas/genética , Infecções por Herpesviridae/sangue , Cinética , Linfonodos/imunologia , Linfonodos/metabolismo , Ativação Linfocitária , Cooperação Linfocítica , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Baço/imunologia , Baço/metabolismo , Linfócitos T/imunologiaRESUMO
A single genetic locus, flavivirus resistance (Flv), controls virus titres and severity of flavivirus infection in mouse brain. It has been mapped to mouse chromosome 5 and shown to include different allelic forms. While the majority of laboratory mouse strains are susceptible to flaviviruses and carry the Flv(s) allele, wild mice and laboratory mouse strains recently derived from them are resistant and carry flavivirus-resistance alleles including Flv(r)-like and Flv(mr) alleles. Although there is a mouse model of flavivirus resistance conferred by the Flv(r) allele, other resistance alleles have not been adequately studied due to a lack of appropriate animal models. In this paper we describe the development of new flavivirus-resistant mouse strains, C3H.M.domesticus-Flv(r) and C3H.MOLD-Flv(mr), which carry the novel resistance alleles Flv(r)-like and Flv(mr) on the genetic background of flavivirus susceptible C3H/HeJ mice. The new strains were created by 10 to 11 generations of backcrossing followed by brother-sister matings resulting in a generation of homozygous founder stocks. Genome analysis of the newly developed mouse strains has revealed chromosomal regions of approximately 9 and 11 cM, respectively, encompassing Flv on chromosome 5, which are derived from resistant donor mice. These segments are much smaller than the segment of approximately 31 cM described in the congenic resistant mouse strain C3H.PRI-Flv(r) (also known as C3H/RV). The new congenic mouse strains, which were created to carry the Flv(r)-like and Flv(mr) alleles on the standardized genetic background of susceptible mice, represent new animal models of flavivirus resistance conferred by these novel resistance alleles.
Assuntos
Alelos , Mapeamento Cromossômico , Infecções por Flavivirus/genética , Animais , Predisposição Genética para Doença , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Endogâmicos C3H , Polimorfismo Genético , Especificidade da Espécie , Replicação ViralRESUMO
Many cytokines activate two highly homologous Stat proteins, 5a and 5b. Mice deficient in both genes lack all growth hormone and prolactin functions but retain functions associated with cytokines such as erythropoietin. Here, we demonstrate that, while lymphoid development is normal, Stat5a/b mutant peripheral T cells are profoundly deficient in proliferation and fail to undergo cell cycle progression or to express genes controlling cell cycle progression. In addition, the mice lack NK cells, develop splenomegaly, and have T cells with an activated phenotype, phenotypes seen in IL-2 receptor beta chain-deficient mice. These phenotypes are not seen in mice lacking Stat5a or Stat5b alone. The results demonstrate that the Stat5 proteins, redundantly, are essential mediators of IL-2 signaling in T cells.
Assuntos
Ciclo Celular/fisiologia , Proteínas de Ligação a DNA/fisiologia , Interleucina-2/fisiologia , Proteínas do Leite , Linfócitos T/citologia , Transativadores/fisiologia , Animais , Divisão Celular , Células Cultivadas , Citometria de Fluxo , Camundongos , Camundongos Mutantes , Fator de Transcrição STAT5 , Timo/citologia , Timo/metabolismoRESUMO
Inherited deficiency of the CD40 ligand (X-linked hyper-IgM syndrome) is characterized by failure of immunoglobulin isotype switching and severe defects of cell-mediated immunity. To test the potential for gene transfer therapy to correct this disorder, we transduced murine bone marrow or thymic cells with a retroviral vector containing the cDNA for the murine CD40 ligand (CD40L) and injected them into CD40L-/- mice. Even low-level, constitutive expression of the transgene stimulated humoral and cellular immune functions in these mice. With extended follow-up, however, 12 of 19 treated mice developed T-lymphoproliferative disorders, ranging from polyclonal increases of lymphoblasts to overt monoclonal T-lymphoblastic lymphomas that involved multiple organs. Our findings show that constitutive (rather than tightly regulated), low-level expression of CD40L can produce abnormal proliferative responses in developing T lymphocytes, apparently through aberrant interaction between CD40L+ and TCRalphabeta+CD40+ thymocytes. Current methods of gene therapy may prove inappropriate for disorders involving highly regulated genes in essential positions in proliferative cascades.
Assuntos
Terapia Genética , Transtornos Linfoproliferativos/genética , Transtornos Linfoproliferativos/terapia , Glicoproteínas de Membrana/fisiologia , Linfócitos T/imunologia , Animais , Células da Medula Óssea/citologia , Células da Medula Óssea/imunologia , Ligante de CD40 , Técnicas de Transferência de Genes , Imunidade Celular/genética , Linfoma/imunologia , Transtornos Linfoproliferativos/imunologia , Glicoproteínas de Membrana/deficiência , Glicoproteínas de Membrana/genética , Camundongos , Camundongos Knockout , Reação em Cadeia da Polimerase , Retroviridae/genética , Retroviridae/fisiologia , Timo/imunologia , Neoplasias do Timo/imunologia , Transdução Genética , Replicação Viral , Cromossomo XRESUMO
Flaviviruses are small, enveloped RNA viruses which are generally transmitted by arthropods to animals and man. Although flaviviruses cause important diseases in domestic animals and man, flaviviral infection of animals which constitute the normal vertebrate reservoir may be mild or sub-clinical, which suggests that some adaptation between virus and host may have occurred. While this possibility is difficult to study in wild animals, extensive studies using laboratory mice have demonstrated the existence of innate, flavivirus-specific resistance. Resistance is heritable and is attributable to the gene Flvr, which is located on chromosome 5 in this species. The mechanism of resistance is at present unknown, but acts early and limits the replication of flaviviruses in cells. While some evidence supports a role for Flvr in enhancing the production of defective interfering virus, thereby restricting the production of infectious virus, other reports suggest that Flvr interferes with either virus RNA replication or RNA packaging. Recent research suggests that cytoplasmic proteins bind to the viral replication complex and that allelic forms of these proteins in resistant mice may restrict the production of infectious progeny. Apparent resistance to flaviviruses has been described in other vertebrates, although it remains to be seen if this is attributable to a homologue of Flvr. Nonetheless, knowledge gained of the characteristics and function of Flvr in mice should be applicable to other host species, and improvement of resistance to flaviviral infection in domestic animals by selective breeding or gene technology may ultimately be possible.
Assuntos
Animais Domésticos , Animais Selvagens , Vetores Artrópodes/virologia , Infecções por Flavivirus/veterinária , Flavivirus/fisiologia , Animais , Infecções por Flavivirus/genética , Infecções por Flavivirus/imunologia , Humanos , Imunidade Inata/genética , Replicação ViralRESUMO
Inherited resistance to flaviviruses in laboratory mice is a rare trait conferred by an autosomal dominant gene (Flvr). To provide information on genetic resistance to flaviviruses in wild mice, we analysed (i) wild M. m. domesticus trapped in Australia, and (ii) mice representing other species and subspecies in the genus Mus. Mice were screened for resistance relative to C3H/HeJ mice by intracerebral challenge with Murray Valley encephalitis virus or yellow fever virus, and breeding studies were undertaken to identify inherited resistance factors. Widespread flavivirus resistance was demonstrated in Australian M. m. domesticus. A single, autosomal dominant Flvr-like gene appeared to be primarily responsible, but there was some evidence for additional inherited resistance factors. Flavivirus resistance was also identified in other taxonomic groups, and a genetic basis for this resistance was demonstrated in M. m. musculus (Skive), M. spretus, and M. spicilegus. Interestingly, M. m. musculus (CZI-O) were more susceptible than C3H/HeJ mice. Our findings show that genetic resistance to flaviviruses is common in divergent taxonomic groups in the genus Mus, suggesting that the trait has an ancient evolutionary origin, but whether flavivirus resistance genes have an anti-viral role or serve some other function is unknown.
Assuntos
Vírus da Encefalite do Vale de Murray , Encefalite por Arbovirus/veterinária , Muridae , Febre Amarela/veterinária , Animais , Animais Selvagens , Austrália , Cruzamentos Genéticos , Encefalite por Arbovirus/genética , Encefalite por Arbovirus/imunologia , Feminino , Imunidade Inata/genética , Masculino , Camundongos , Camundongos Endogâmicos C3H , Especificidade da Espécie , Replicação Viral , Febre Amarela/genética , Febre Amarela/imunologiaRESUMO
Janus kinase-3 (JAK3) deficiency has recently been identified as a cause of severe combined immunodeficiency (SCID) in humans. We used a mouse model of Jak3-deficient SCID to test a gene therapy approach for treatment of this disease. Transfer of a Jak3 retroviral vector to repopulating hematopoietic stem cells resulted in increased numbers of T and B lymphocytes, reversal of hypogammaglobulinemia, restoration of T-cell activation upon stimulation with mitogens, and development of an antigen-specific immune response after immunization. Analysis for vector copy number in lymphoid and myeloid populations showed a large in vivo selective advantage for Jak3-expressing lymphoid cells. These results show that gene replacement is a feasible treatment strategy for this disease and that naturally occurring in vivo selection of corrected cells is an important advantage of this approach.
Assuntos
Linfócitos B/imunologia , Terapia Genética/métodos , Proteínas Tirosina Quinases/deficiência , Proteínas Tirosina Quinases/genética , Imunodeficiência Combinada Severa/imunologia , Imunodeficiência Combinada Severa/terapia , Linfócitos T/imunologia , Agamaglobulinemia/etiologia , Agamaglobulinemia/terapia , Animais , Formação de Anticorpos , Células da Medula Óssea/citologia , Transplante de Medula Óssea/métodos , Técnicas de Transferência de Genes , Vetores Genéticos , Humanos , Imunoglobulina A/sangue , Imunoglobulina G/sangue , Imunoglobulina M/sangue , Janus Quinase 3 , Ativação Linfocitária , Camundongos , Camundongos Endogâmicos C57BL , Camundongos SCID , Reação em Cadeia da Polimerase , Proteínas Tirosina Quinases/biossíntese , Retroviridae , Imunodeficiência Combinada Severa/enzimologia , Baço/imunologiaRESUMO
Reverse genetics was used to modify the influenza virus genome by inserting the p46-63 sequence of hen egg lysozyme (HEL) into the neuraminidase stalk of the virus. The resulting virus, HEL-Flu, contained the epitopes recognized by CD4+ T cells from 3A9-TCR transgenic mice (C3HTg). Here, we show that HEL-Flu was infectious in the respiratory tract of both C3H and C3HTg mice, the latter animals showing an early, transient morbidity. Splenic dendritic cells and certain cloned populations of splenic macrophages and brain microglia constitutively presented infectious and inactivated HEL-Flu to the T cells in an Ag-specific and MHC class II-restricted manner. These results demonstrate the utility of HEL-Flu in assessing the APC activity for naive T cells; they also extend the previous studies showing that discrete populations of macrophages and microglia constitutively process and present Ag to naive T cells.
Assuntos
Apresentação de Antígeno , Linfócitos T CD4-Positivos/imunologia , Muramidase/imunologia , Orthomyxoviridae/imunologia , Receptores de Antígenos de Linfócitos T alfa-beta/imunologia , Animais , Antígenos Virais/genética , Antígenos Virais/imunologia , Antígenos CD4/imunologia , Embrião de Galinha , Camundongos , Camundongos Transgênicos , Muramidase/genética , Orthomyxoviridae/genética , Receptores de Antígenos de Linfócitos T alfa-beta/genéticaRESUMO
Intranasal deposition of Sendai virus (SV) in C57BL/6 mice provokes an Ab-forming cell (AFC) reaction in mediastinal (MLN) and cervical lymph nodes (CLN), which drain the lungs and upper respiratory tract, respectively. While the majority of AFC elicited by infectious SV at both sites produced IgG, the CLN response to SV rendered inactive in replication was restricted almost entirely to IgA, although isotype switching in mediastinal continued to be skewed heavily to IgG. However, in vitro restimulation of the accompanying virus-specific T cell populations from the two sites did not reveal any significant difference in lymphokine output, and isotype expression was not altered substantially in mice lacking IL-4 or IL-6 genes. To dissociate the response to specific Ags from the inflammatory reaction to viral infection, we examined the response to inactivated SV in the face of infection with influenza virus A/HKx31. The magnitude and IgA dominance of the anti-SV AFC population in the CLN were unaffected by a simultaneous, vigorous, IgG-dominated CLN anti-influenza reaction. Evidently, the characteristics of this antiviral response are determined primarily by cognate interactions. Moreover, the IgA bias of the CLN AFC response to inactivated SV was observed only when the virus was delivered intranasally: injection under the epidermis of the cheek, a site that has a lymphatic drainage into the CLN, resulted in an IgG-dominated CLN AFC reaction, lacking IgA. The site of deposition of a vaccine can thus have more influence on the pattern of isotypes induced than the site at which the immune response is initiated.
Assuntos
Anticorpos Antivirais/análise , Isotipos de Imunoglobulinas/análise , Linfonodos/imunologia , Infecções por Respirovirus/imunologia , Replicação Viral , Animais , Citocinas/biossíntese , Feminino , Interleucina-4/fisiologia , Interleucina-6/fisiologia , Camundongos , Camundongos Endogâmicos C57BL , Linfócitos T/imunologiaRESUMO
Human parainfluenza virus-type I (hPIV-1) infections are a common cause of "group" and hospitalizations among young children. Here we address the possibility of using the xenotropic Sendai virus [a mouse parainfluenza virus (PIV)] as a vaccine for hPIV-1. Sendai virus was administered to six African green monkeys (Cercopithecus aethiops) by the intranasal (i.n.) route. A long lasting virus-specific antibody response was elicited, both in the serum and nasal cavity. Sendai virus caused no apparent clinical symptoms in the primates, but live virus was detected in the nasal cavity for several days after inoculation. No virus was detected after a second dose of Sendai virus was administered on day 126 after the initial priming. Animals were challenged with hPIV-1 i.n. on day 154. All six vaccinated animals were fully protected from infection while six of six control animals were infected with hPIV-1. The antibody responses induced by Sendai virus immunizations proved to be greater than those induced by hPIV-1. These results demonstrate that unmanipulated Sendai virus is an effective vaccine against hPIV-1 in a primate model and may constitute a practical vaccine for human use.
Assuntos
Vírus da Parainfluenza 1 Humana , Infecções por Respirovirus/prevenção & controle , Respirovirus/imunologia , Vacinas Virais , Administração Intranasal , Animais , Anticorpos Antivirais/biossíntese , Especificidade de Anticorpos , Chlorocebus aethiops , Humanos , Imunoglobulina A/imunologiaRESUMO
Homozygous disruption (-/-) of the interleukin-4 (IL-4) gene did not obviously modify the severity of Sendai virus infection in the highly susceptible 129/J mouse strain. The virus was cleared from the respiratory tract, and potent cytotoxic T lymphocyte (CTL) effectors were present in the cell population recovered by bronchoalveolar lavage. However, the prevalence of virus-specific CTL precursors (p) was consistently diminished in the spleen and regional lymph nodes of the IL-4 -/- mice at day 7 after infection. Also, virus-specific serum immunoglobulin G1 (IgG1) levels were greatly reduced and few IgG1-producing cells were detected in the lymphoid tissue. The effect on IgG1 class switching was to be expected, but the decrease in CTLp numbers has not been observed previously for a virus-specific immune response.
Assuntos
Anticorpos Antivirais/imunologia , Interleucina-4/genética , Infecções por Respirovirus/imunologia , Respirovirus/imunologia , Linfócitos T Citotóxicos/imunologia , Animais , Anticorpos Antivirais/sangue , Homozigoto , Imunoglobulina G/sangue , Imunoglobulina G/imunologia , Camundongos , Camundongos Endogâmicos C57BLRESUMO
Sendai virus is eliminated from the respiratory tract of gamma interferon (IFN-gamma) -/- BALB/c mice with normal kinetics. The level of virus-specific cytotoxic T-lymphocyte (CTL) activity in the cell population recovered by bronchoalveolar lavage is unimpaired, the prevalence of interleukin-4 (IL-4)-producing cells is increased, and the titers of virus-specific immunoglobulins IgG1 and IgG2b are higher in the IFN-gamma -/- mice. The emergence of this T-helper 2 response profile in both lymphoid tissue and the pneumonic lung has no obvious deleterious consequences. Virus clearance is slightly delayed following depletion of the CD4+ subset, with the effect being similar in magnitude for IFN-gamma -/- and +/+ mice. However, the generation of CTL precursors (CTLp) is diminished in the IFN-gamma -/- (but not +/+) mice in the absence of concurrent CD4+ T help. Apparently the clonal expansion of the CTLp population can be promoted either by a cytokine (perhaps IL-2) produced by the IFN-gamma -/- CD4+ T cells or by IFN-gamma made by other cell types in the +/+ mice.
Assuntos
Interferon gama/imunologia , Pneumonia Viral/imunologia , Infecções por Respirovirus/imunologia , Respirovirus/imunologia , Linfócitos T Citotóxicos/imunologia , Animais , Anticorpos Antivirais/sangue , Imunoglobulina G/sangue , Interferon gama/genética , Interleucina-4/análise , Interleucina-5/análise , Camundongos , Camundongos Endogâmicos BALB C , Pneumonia Viral/sangue , Pneumonia Viral/virologia , Respirovirus/isolamento & purificação , Infecções por Respirovirus/sangue , Infecções por Respirovirus/virologiaRESUMO
Signal transducers and activators of transcription (STATs) are activated by tyrosine phosphorylation in response to cytokines and mediate many of their functional responses. Stat4 was initially cloned as a result of its homology with Stat1 (refs 4, 5) and is widely expressed, although it is only tyrosine-phosphorylated after stimulation of T cells with interleukin (IL)-12 (refs 6,7). IL-12 is required for the T-cell-independent induction of the cytokine interferon (IFN)-gamma, a key step in the initial suppression of bacterial and parasitic infections. IL-12 is also important for the development of a Th1 response, which is critical for effective host defence against intracellular pathogens. To determine the function of Stat4 and its role in IL-12 signalling, we have produced mice that lack Stat4 by gene targeting. The mice were viable and fertile, with no detectable defects in haematopoiesis. However, all IL-12 functions tested were disrupted, including the induction of IFN-gamma, mitogenesis, enhancement of natural killer cytolytic function and Th1 differentiation.
Assuntos
Proteínas de Ligação a DNA/fisiologia , Interleucina-12/fisiologia , Células Matadoras Naturais/imunologia , Linfócitos T/imunologia , Transativadores/fisiologia , Animais , Diferenciação Celular , Linhagem Celular , Células Cultivadas , Clonagem Molecular , Citotoxicidade Imunológica , Proteínas de Ligação a DNA/genética , Marcação de Genes , Interferon gama/biossíntese , Ativação Linfocitária/fisiologia , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Fator de Transcrição STAT4 , Transdução de Sinais , Espermatogênese/fisiologia , Baço/citologia , Linfócitos T/citologia , Transativadores/genéticaRESUMO
The lack of an effective animal model has been a major obstacle in attempts to define the role of humoral and cellular immune responses in protection against flavivirus infection. We have used F1 hybrid mice (BALB/c x C3H/RV) that are heterozygous for the flavivirus resistance allele F1vr and show reduced virus replication in the brain after intracerebral inoculation. F1 hybrid mice challenged by intracerebral inoculation with Murray Valley encephalitis (MVE) virus developed encephalitis 2-3 days later than a genetically susceptible strain (BALB/c) but showed a similar mortality rate. This delay in the onset of disease provided more opportunity for virus clearance by primed immune responses. Using F1 hybrid mice we were able to demonstrate protective immunity induced by structural and non-structural proteins of MVE virus by immunization with pure NS1 protein or recombinant vaccinia viruses that expressed various regions of the MVE genome. These constructs included VV-STR (C-prM-E-NS1-NS2A), VV-delta C (prM-E-Ns1-NS2A) and VV-NS1 (NS1-NS2A). VV-delta C vaccinated mice were completely protected (100% survival)from challenge with 1000 infectious units of MVE virus, while mice inoculated with VV-STR, VV-NS1 or pure NS1 were partially protected (40%, 47% and 85% respectively). Analysis of prechallenge sera and in vivo depletion studies revealed that the solid protection induced by VV-delta C was mediated by neutralizing antibody to the E protein and did not require a CD8+ T cell response. The partial protection provided by VV-STR, VV-NS1 and pure NS1 occurred after induction of antibody to NS1. However, depletion of CD8+ cells prior to virus challenge ablated the protection provided by VV-NS1 indicating some requirement for class I restricted cytotoxic T cells.
Assuntos
Vírus da Encefalite do Vale de Murray/imunologia , Encefalite por Arbovirus/imunologia , Flavivirus/imunologia , Vacinas Sintéticas , Proteínas do Envelope Viral/imunologia , Proteínas não Estruturais Virais/imunologia , Vacinas Virais , Replicação Viral , Animais , Anticorpos Antivirais/biossíntese , Anticorpos Antivirais/sangue , Formação de Anticorpos , Encéfalo/virologia , Linfócitos T CD8-Positivos/imunologia , Chlorocebus aethiops , Cruzamentos Genéticos , Primers do DNA , Encefalite por Arbovirus/prevenção & controle , Ensaio de Imunoadsorção Enzimática , Flavivirus/isolamento & purificação , Flavivirus/fisiologia , Imunidade Celular , Imunidade Inata , Imunoterapia Adotiva , Depleção Linfocítica , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Endogâmicos C3H , Dados de Sequência Molecular , Reação em Cadeia da Polimerase , Especificidade da Espécie , Vacinas Sintéticas/biossíntese , Vaccinia virus/imunologia , Células Vero , Proteínas do Envelope Viral/biossíntese , Proteínas não Estruturais Virais/biossínteseRESUMO
Signal transducers and activators of transcription (Stats) are activated by tyrosine phosphorylation in response to cytokines, and are thought to mediate many of their functional responses. Stat6 is activated in response to interleukin (IL)-4 and may contribute to various functions including mitogenesis, T-helper cell differentiation and immunoglobulin isotype switching. To evaluate the role of Stat6, we generated Stat6-null mice (Stat6 -/-) by gene disruption in embryonic stem cells. The mice were viable, indicating the lack of a non-redundant function in normal development. Although naive lymphoid cell development was normal, Stat6 -/- mice were deficient in IL-4-mediated functions including Th2 helper T-cell differentiation, expression of cell surface markers, and immunoglobulin class switching to IgE. In contrast, IL-4-mediated proliferation was only partly affected.
Assuntos
Switching de Imunoglobulina , Imunoglobulina E/imunologia , Interleucina-4/imunologia , Células Th2/citologia , Transativadores/fisiologia , Animais , Sequência de Bases , Diferenciação Celular/genética , Diferenciação Celular/fisiologia , Linhagem Celular , Células Cultivadas , Sondas de DNA , Marcação de Genes , Imunidade/genética , Imunidade/fisiologia , Tecido Linfoide/imunologia , Camundongos , Dados de Sequência Molecular , Fator de Transcrição STAT6 , Células Th2/imunologia , Transativadores/genéticaRESUMO
The experiments described establish that CD4+ T-cell-dependent effector mechanisms can eliminate an H3N2 influenza A virus from lung cells that are unable to express class II major histocompatibility complex (MHC) glycoproteins. Radiation chimeras were made by using CD4+ T cells and bone marrow from CD8-depleted, MHC class II +/+ mice and irradiated (950 rads) MHC class II -/- recipients. The influenza virus-specific CD4+ T-cell responses in these +/+-->-/- mice were not obviously different from those in the +/+-->+/+ controls: the cytokine profiles, the spectra of plasma cells producing the various immunoglobulin isotypes, and the frequencies of virus-specific CD4+ T cells were similar for the two groups. Expression of class II MHC glycoproteins on stimulator cells, B lymphocytes, and monocytes/macrophages is apparently sufficient for CD4+ T cells to terminate influenza virus infection of MHC class II -/- respiratory epithelium. A possible explanation is that the local spread of this lytic virus in the lung is limited by cytokines and/or antibody.
Assuntos
Linfócitos T CD4-Positivos/imunologia , Antígenos de Histocompatibilidade Classe II/imunologia , Vírus da Influenza A/imunologia , Pulmão/imunologia , Animais , Linfócitos T CD4-Positivos/metabolismo , Antígenos de Histocompatibilidade Classe I/imunologia , Humanos , Pulmão/virologia , Camundongos , Camundongos Endogâmicos C57BLRESUMO
Genetically determined resistance to flaviviruses in mice is a dominant trait conferred by alleles at a single autosomal locus designated Flv, but no gene products have been associated with this locus and the mechanism of resistance is not well understood. To further characterize this model of genetic resistance, we conducted mapping studies to determine the chromosomal location of Flv. Because of evidence suggesting that the Flv locus is on chromosome 5, three-point backcross linkage analyses were used to define the location of Flv relative to previously assigned chromosome 5 markers. The results confirm the chromosome 5 location of Flv and indicate a map position between the anchor loci rd and Gus-s. The chromosomal localization of Flv is the first step in the production of a detailed linkage map of the Flv region, which may open approaches to positional cloning of the resistance gene.