BALB/c小鼠作为单纯疱疹病毒1型感染模型的免疫学分析

在单纯疱疹病毒1型(herpes simplex virus type 1,HSV-1)小鼠感染及其相关研究中,临床病理和免疫学指标对其分析具有重要技术意义。本研究观察了HSV-1在不同条件下感染BALB/c小鼠后的多个免疫学指标,包括外周血单核细胞(peripheral blood mononuclear cell,PBMC)群体中树突细胞比例及功能、血清中和抗体水平、PBMC中HSV-1抗原特异性T细胞水平,以及潜伏感染期小鼠神经组织中CD8^＋ T细胞浸润情况。结果显示,HSV-1毒株Mckrae、17＋以角膜及滴鼻途径感染3周龄及6周龄BALB/c小鼠后,小鼠PBMC中树突细胞数量增加,并显示出刺激病毒抗原特异性T细胞增殖的能力。病毒感染后35 d,小鼠PBMC中未检测到白细胞介素4(interleukin 4,IL-4)^＋抗原特异性T细胞,但能检测到低水平的γ干扰素(interferon γ,IFN-γ)^＋抗原特异性T细胞;小鼠血清中未检测到或仅能检测到低水平的中和抗体。HSV-1以皮下及足垫注射途径感染BALB/c小鼠90 d后,足垫感染途径较皮下感染诱导出更高水平的血清中和抗体,PBMC中可检测到IL-4^＋及IFN-γ^＋抗原特异性T细胞,但不同毒株及小鼠周龄之间出现T细胞反应程度差异。组织病理学结果表明,各组小鼠三叉神经组织中均有CD8^＋ T细胞浸润。这些结果提示,不同HSV-1毒株以不同途径感染不同周龄BALB/c小鼠后,均可刺激树突细胞成熟及呈递病毒抗原,但血清中和抗体及PBMC中病毒抗原特异性T细胞水平在不同毒株、感染途径及小鼠周龄之间有差异。     

Identification of novel immunodominant CD4+ Th1-type T-cell peptide epitopes from herpes simplex virus glycoprotein D that confer protective immunity

The molecular characterization of the epitope repertoire on herpes simplex virus (HSV) antigens would greatly expand our knowledge of HSV immunity and improve immune interventions against herpesvirus infections. HSV glycoprotein D (gD) is an immunodominant viral coat protein and is considered an excellent vaccine candidate antigen. By using the TEPITOPE prediction algorithm, we have identified and characterized a total of 12 regions within the HSV type 1 (HSV-1) gD bearing potential CD4(+) T-cell epitopes, each 27 to 34 amino acids in length. Immunogenicity studies of the corresponding medium-sized peptides confirmed all previously known gD epitopes and additionally revealed four new immunodominant regions (gD(49-82), gD(146-179), gD(228-257), and gD(332-358)), each containing naturally processed epitopes. These epitopes elicited potent T-cell responses in mice of diverse major histocompatibility complex backgrounds. Each of the four new immunodominant peptide epitopes generated strong CD4(+) Th1 T cells that were biologically active against HSV-1-infected bone marrow-derived dendritic cells. Importantly, immunization of H-2(d) mice with the four newly identified CD4(+) Th1 peptide epitopes but not with four CD4(+) Th2 peptide epitopes induced a robust protective immunity against lethal ocular HSV-1 challenge. These peptide epitopes may prove to be important components of an effective immunoprophylactic strategy against herpes.     

Development of a glycoprotein D-expressing dominant-negative and replication-defective herpes simplex virus 2 (HSV-2) recombinant viral vaccine against HSV-2 infection in mice

Using the T-REx (Invitrogen, California) gene switch technology and a dominant-negative mutant polypeptide of herpes simplex virus 1 (HSV-1)-origin binding protein UL9, we previously constructed a glycoprotein D-expressing replication-defective and dominant-negative HSV-1 recombinant viral vaccine, CJ9-gD, for protection against HSV infection and disease. It was demonstrated that CJ9-gD is avirulent following intracerebral inoculation in mice, cannot establish detectable latent infection following different routes of infection, and offers highly effective protective immunity against primary HSV-1 and HSV-2 infection and disease in mouse and guinea pig models of HSV infections. Given these favorable safety and immunological profiles of CJ9-gD, aiming to maximize levels of HSV-2 glycoprotein D (gD2) expression, we have constructed an ICP0 null mutant-based dominant-negative and replication-defective HSV-2 recombinant, CJ2-gD2, that contains 2 copies of the gD2 gene driven by the tetracycline operator (tetO)-bearing HSV-1 major immediate-early ICP4 promoter. CJ2-gD2 expresses gD2 as efficiently as wild-type HSV-2 infection and can lead to a 150-fold reduction in wild-type HSV-2 viral replication in cells coinfected with CJ2-gD2 and wild-type HSV-2 at the same multiplicity of infection. CJ2-gD2 is avirulent following intracerebral injection and cannot establish a detectable latent infection following subcutaneous (s.c.) immunization. CJ2-gD2 is a more effective vaccine than HSV-1 CJ9-gD and a non-gD2-expressing dominant-negative and replication-defective HSV-2 recombinant in protection against wild-type HSV-2 genital disease. Using recall response, we showed that immunization with CJ2-gD2 elicited strong HSV-2-specific memory CD4(+) and CD8(+) T-cell responses. Collectively, given the demonstrated preclinical immunogenicity and its unique safety profiles, CJ2-gD2 represents a new class of HSV-2 replication-defective recombinant viral vaccines in protection against HSV-2 genital infection and disease.     

Comparison of adjuvant efficacy of herpes simplex virus type 1 recombinant viruses expressing TH1 and TH2 cytokine genes

The adjuvant effects of cytokines in humoral and cell-mediated immunity to herpes simplex virus type 1 (HSV-1) have been examined in mice using HSV-1 recombinant viruses expressing murine interleukin-2 (IL-2), IL-4, or gamma interferon (IFN-gamma) gene. Groups of naive BALB/c mice were immunized intraperitoneally with one or three doses of the HSV-1 recombinant viruses expressing IL-2, IL-4, or IFN-gamma or with parental control virus. Despite similar replication kinetics, these three recombinant viruses elicited different immune responses to HSV-1 on immunization. Immunization with the recombinant virus expressing IL-4 elicited a humoral response of greater magnitude than immunization with the recombinant viruses expressing IL-2 or IFN-gamma or with parental virus. In contrast, immunization with recombinant virus expressing IL-2 elicited a higher cytotoxic T-cell response than immunization with viruses expressing IL-4 or IFN-gamma. Stimulation in vitro of splenocytes obtained from the mice immunized with UV-inactivated HSV-1 McKrae resulted in a T(H)1 pattern of cytokine expression irrespective of the recombinant virus used in the immunization. As observed for the parental virus, both CD4(+) and CD8(+) T cells contributed equally to the production of IL-2 by the splenocytes of mice immunized with any of the three recombinant viruses. However, the pattern of IFN-gamma production by CD4(+) and CD8(+) T cells differed according to the recombinant virus used. After lethal ocular challenge, all immunized mice were protected completely against death and manifestations of eye disease caused by HSV-1, which are typical responses in unimmunized mice. Mice immunized with IL-4-expressing virus cleared the virus from their eyes more rapidly than mice immunized with IL-2- or IFN-gamma-expressing virus. Taken together, our results suggest that, in contrast to IFN-gamma which did not exhibit an adjuvant effect, both IL-4 and IL-2 act as adjuvants in immunization with HSV, with IL-4 showing greater efficacy.     

Dual role of B cells in mediating innate and acquired immunity to herpes simplex virus infections

mu-immunoglobulin chain gene targeted B-cell-deficient mice of susceptible BALB/c strain and resistant C57B1/6 strain are up to 100- to 1000-fold more susceptible to cutaneous infection by herpes simplex virus (HSV) than the respective control wild type mice. The effect of the lack of B cells on immunity to HSV infections was analyzed and B cells were found to play a dual role in affecting both innate and acquired immune responses. Natural antibodies (IgM isotype), reactive with HSV have an anti-viral effect in the innate control of primary cutaneous HSV infection. B cells can also function as antigen-presenting cells for the stimulation of HSV-specific CD4+ T-cell responses. Consequently, CD4+ T cells and interferon-gamma responses were found to be significantly impaired in HSV-infected B-cell-deficient mice compared to that seen in control mice. No significant differences were found in natural-killer-cell- or HSV-specific CD8+ T-cell activity between control and B-cell-deficient mice. Our results imply a role for B cell in mediating innate and CD4+ T-cell-specific immunity in determining susceptibility to primary HSV infections.     

Monophosphoryl lipid A and QS21 increase CD8 T lymphocyte cytotoxicity to herpes simplex virus-2 infected cell proteins 4 and 27 through IFN-gamma and IL-12 production

We have shown previously that IFN-gamma pretreatment of human epidermal cells (ECs) cultured in vitro partially reverses down-regulation of surface MHC class I by HSV infection, allowing recognition by CD8 CTLs, and that HSV immediate early (IE)/early (E) proteins are the predominant targets for CD8 CTLs. In this study of 25 subjects, CD8 CTLs recognized the HSV-2 IE infected cell protein 27 (ICP27) (expressed in autologous IFN-gamma-pretreated, Vaccinia virus recombinant-infected ECs) in all subjects studied, ICP4 in 89%, and ICP0 in 11%. The main hierarchy of recognition was ICP27 > ICP4. ICP27 was the dominant target in 89% of subjects but showed great individual variability in the degree of cytotoxicity. CD8 cytotoxicity specific for HSV-2 IE proteins was enhanced by 48-67% when CD8 CTLs were coincubated with the combination of monophosphoryl lipid A and QS21 adjuvants at the time of Ag presentation. These adjuvants also significantly enhanced IL-12 and IFN-gamma production from nonadherent mononuclear cells stimulated by HSV-2-infected ECs. Addition of IL-12 and IFN-gamma at the time of initial Ag presentation enhanced CD8 cytotoxicity to levels comparable with those stimulated by the adjuvants. Addition of neutralizing Abs to IL-12 or IFN-gamma inhibited CD8 T cell cytotoxicity up to 95% when a combination of the Abs were added at the time of initial Ag presentation. Therefore, the mechanism for the enhancement of CD8 T cell cytotoxicity by adjuvants in this system appears to be via increased levels of IL-12 and IFN-gamma.     

Multiple specificities in the murine CD4+ and CD8+ T-cell response to dengue virus.

The target epitopes, serotype specificity, and cytolytic function of dengue virus-specific T cells may influence their theoretical roles in protection against secondary infection as well as the immunopathogenesis of dengue hemorrhagic fever. To study these factors in an experimental system, we isolated dengue virus-specific CD4+ and CD8+ T-cell clones from dengue-2 virus-immunized BALB/c mice. The T-cell response to dengue virus in this mouse strain was heterogeneous; we identified at least five different CD4+ phenotypes and six different CD8+ phenotypes. Individual T-cell clones recognized epitopes on the dengue virus pre-M, E, NSl/NS2A, and NS3 proteins and were restricted by the I-Ad, I-Ed, Ld, and Kd antigens. Both serotype-specific and serotype-cross-reactive clones were isolated in the CD4+ and CD8+ subsets; among CD8+ clones, those that recognized the dengue virus structural proteins were serotype specific whereas those that recognized the nonstructural proteins were serotype cross-reactive. All of the CD8+ and one of five CD4+ clones lysed dengue virus-infected target cells. Using synthetic peptides, we identified an Ld-restricted epitope on the E protein (residues 331 to 339, SPCKIPFEI) and a Kd-restricted epitope on the NS3 protein (residues 296 to 310, ARGYISTRVEM GEAA). These data parallel previous findings of studies using human dengue virus-specific T-cell clones. This experimental mouse system may be useful for studying the role of the virus serotype and HLA haplotype on T-cell responses after primary dengue virus infection.     

LFA-3 plasmid DNA enhances Ag-specific humoral- and cellular-mediated protective immunity against herpes simplex virus-2 in vivo: involvement of CD4+ T cells in protection

Adhesion molecules are important for cell trafficking and delivery of secondary signals for stimulation of T cells and antigen-presenting cells (APCs) in a variety of immune and inflammatory responses. Adhesion molecules lymphocyte function-associated antigen (LFA)-1 and CD2 on T cells recognize intercellular adhesion molecule (ICAM)-1 and LFA-3 on APCs, respectively. Recent studies have suggested that these molecules might play a regulatory role in antigen-specific immune responses. To investigate specific roles of adhesion molecules in immune induction we coimmunized LFA-3 and ICAM-1 cDNAs with a gD plasmid vaccine and then analyzed immune modulatory effects and protection against lethal herpes simplex virus (HSV)-2 challenge. We observed that gD-specific IgG production was enhanced by LFA-3 coinjection. However, little change in IgG production was observed by ICAM-1 coinjection. Furthermore, both Th1 and Th2 IgG isotype production was driven by LFA-3. LFA-3 also enhanced Th cell proliferative responses and production of interleukin (IL)-2, interferon-gamma, IL-4, and IL-10 from splenocytes. In contrast, ICAM-1 showed slightly increasing effects on T-cell proliferation responses and cytokine production. beta-Chemokine production (RANTES, MIP-1alpha, and MCP-1) was also influenced by LFA-3 or ICAM-1. When animals were challenged with a lethal dose of HSV-2, LFA-3-coimmunized animals exhibited an enhanced survival rate, as compared to animals given ICAM-1 or gD DNA vaccine alone. This enhanced protection appears to be mediated by CD4+ T cells, as determined by in vitro and in vivo T-cell subset deletion. These studies demonstrate that adhesion molecule LFA-3 can play an important role in generating protective antigen-specific immunity in the HSV model system through increased induction of CD4+ Th1 T-cell subset.     

Multifunctional TH1 cells define a correlate of vaccine-mediated protection against Leishmania major

CD4+ T cells have a crucial role in mediating protection against a variety of pathogens through production of specific cytokines. However, substantial heterogeneity in CD4+ T-cell cytokine responses has limited the ability to define an immune correlate of protection after vaccination. Here, using multiparameter flow cytometry to assess the immune responses after immunization, we show that the degree of protection against Leishmania major infection in mice is predicted by the frequency of CD4+ T cells simultaneously producing interferon-gamma, interleukin-2 and tumor necrosis factor. Notably, multifunctional effector cells generated by all vaccines tested are unique in their capacity to produce high amounts of interferon-gamma. These data show that the quality of a CD4+ T-cell cytokine response can be a crucial determinant in whether a vaccine is protective, and may provide a new and useful prospective immune correlate of protection for vaccines based on T-helper type 1 (TH1) cells.     

A DNA vaccine encoding multiple HIV CD4 epitopes elicits vigorous polyfunctional, long-lived CD4+ and CD8+ T cell responses

T-cell based vaccines against HIV have the goal of limiting both transmission and disease progression by inducing broad and functionally relevant T cell responses. Moreover, polyfunctional and long-lived specific memory T cells have been associated to vaccine-induced protection. CD4(+) T cells are important for the generation and maintenance of functional CD8(+) cytotoxic T cells. We have recently developed a DNA vaccine encoding 18 conserved multiple HLA-DR-binding HIV-1 CD4 epitopes (HIVBr18), capable of eliciting broad CD4(+) T cell responses in multiple HLA class II transgenic mice. Here, we evaluated the breadth and functional profile of HIVBr18-induced immune responses in BALB/c mice. Immunized mice displayed high-magnitude, broad CD4(+)/CD8(+) T cell responses, and 8/18 vaccine-encoded peptides were recognized. In addition, HIVBr18 immunization was able to induce polyfunctional CD4(+) and CD8(+) T cells that proliferate and produce any two cytokines (IFNγ/TNFα, IFNγ/IL-2 or TNFα/IL-2) simultaneously in response to HIV-1 peptides. For CD4(+) T cells exclusively, we also detected cells that proliferate and produce all three tested cytokines simultaneously (IFNγ/TNFα/IL-2). The vaccine also generated long-lived central and effector memory CD4(+) T cells, a desirable feature for T-cell based vaccines. By virtue of inducing broad, polyfunctional and long-lived T cell responses against conserved CD4(+) T cell epitopes, combined administration of this vaccine concept may provide sustained help for CD8(+) T cells and antibody responses- elicited by other HIV immunogens.     

Helper activity in antigen-specific antibody production mediated by CD4+ human cytotoxic T cell clones directed against herpes simplex virus

Three HSV type 1 (HSV-1) and HSV type 2 (HSV-2) common ("HSV-type common") and three HSV-1 specific CTL clones, which were CD3+, CD4+, CD8-, 4B4+, and 2H4-, were established. These clones proliferated in response to stimulation with HSV in the presence of autologous APC. The HSV type specificity of the proliferative response was identical with that of the cytotoxic activity of the clones. The cytotoxic activity and the proliferative response were both inhibited by addition of anti-HLA-DR mAb to the culture. After culture of these CTL clones with autologous B cells and macrophages followed by HSV Ag stimulation, anti-HSV antibody was detected in the culture supernatant. The HSV type specificity of the helper function for antibody production was identical with that of the cytotoxicity, i.e., HSV-type common clones, upon stimulation with either HSV-1, or HSV-2, and HSV-1-specific clones, upon stimulation with HSV-1 but not with HSV-2, showed helper activity for anti-HSV antibody production by autologous B cells. Moreover, it was found that these clones produced humoral factors which help autologous B cells to produce antibody. The helper factors were produced by T cell clones in an HSV-type-specific manner. These data suggest that some CD4+ T cells can simultaneously manifest both specific cytotoxicity and helper activity for Ag-specific antibody production by B cells, and that these multifunctional T cells might play an important role in protection against viral infection.     

Characterization of homologous and heterologous rotavirus-specific T-cell responses in infant and adult mice

During primary rotavirus (RV) infection, CD8+ T cells play an important role in viral clearance as well as providing partial protection against reinfection. CD4+ T cells are essential for maximal development of RV-specific intestinal immunoglobulin A. In this study, we took advantage of the cytokine flow cytometry technique to obtain a detailed map of H-2b- and H-2d-restricted CD8+ and CD4+ T-cell epitopes from the RV proteins VP6 and VP7. Three new CD8+ T-cell epitopes (H-2d and H-2b restricted) and one new CD4+ T-cell epitope (H-2d and H-2b restricted) were identified. Using these newly identified targets, we characterized the development and specificity of cellular immune responses in C57BL/6 and BALB/c mice during acute infection of infants and adults. We found that both the CD4+ and CD8+ responses peaked on days 5 to 7 after infection and then declined rapidly. Interestingly, both the response kinetics and tissue distributions were different when epitopes on VP6 and VP7 were compared. VP6 elicited a response which predominated in the intestine, while the response to VP7 was more systemic. Additionally, the T-cell responses elicited after homologous versus heterologous infection differed substantially. We found that during homologous infection, there was a greater response toward VP6 than that toward VP7, especially in the intestine, while after heterologous infection, this was not the case. Finally, in suckling mice, we found two peaks in the CD8 response on days 7 and 14 postinfection, which differed from the single peak found in adults and likely mimics the biphasic pattern of rotavirus shedding in infant mice.     

Immune response and cytokine production following immunization with experimental herpes simplex virus 1 (HSV-1) vaccines

Balb/c mice were immunized with the recombinant fusion protein gD1/313 (FpgD1/313 representing the ectodomain of HSV-1 gD), with the non-pathogenic ANGpath gE-del virus, with the plasmid pcDNA3.1-gD expressing full-length gD1 and with the recombinant immediate early (IE) HSV-1 protein ICP27. Specific antibodies against these antigens (as detected by ELISA) reached high titers with the exception of the DNA vaccine. High-grade protection against challenge with the virulent strain SC16 was found following immunization with the pcDNA3.1-gD plasmid and with the gE-del virus. Medium grade, but satisfactory protection developed after immunization with the FpgD1/313 and minimum grade protection was seen upon immunization with the IE/ICP27 polypeptide. A considerable response of peripheral blood cells (PBL) and splenocytes in the lymphocyte transformation test (LTT) was found in mice immunized with FpgD1/313, with the pcDNA3.1-gD plasmid and with the live ANGpathgE-del virus. For lymphocyte stimulation in vitro, the FpgD1/313 antigen was less effective than the purified gD1/313 polypeptide (cleaved off from the fusion protein); both proteins elicited higher proliferation at the 5 mug per 0.1 mL dose than at the 1 mug per 0.1 mL dose. The secretion of Th type 1 (TNF, IFN-gamma and IL-2) and Th type 2 (IL-4 and IL-6) cytokines was tested in the medium fluid of purified PBL and splenocyte cultures; their absolute values were expressed in relative indexes. The PBL from FpgD1/313 immunized mice showed increased secretion of both T(H)1 (TNF) as well as T(H)2 (IL-4) cytokines (7-10-fold, respectively). Splenocytes from FpgD1/313 immunized mice showed a significant (23-fold) increase in IL-4 production.     

B7 costimulation molecules expressed from the herpes simplex virus 2 genome rescue immune induction in B7-deficient mice

The interaction between B7 costimulation molecules on antigen-presenting cells and CD28 on antigen-responsive T cells is essential for T-cell activation and maturation of immune responses to herpes simplex virus (HSV) infection. Vaccine-induced immune responses also depend upon adequate upregulation of B7 costimulation molecules, but this signal may be limiting for replication-defective virus vaccines. We investigated whether expression of B7 costimulation molecules by a prototypical replication-defective antiviral vaccine could enhance immune responses to the vaccine and whether B7-1 and B7-2 would be similarly effective. We altered an ICP8(-) replication-defective strain of HSV type 2 (HSV-2), 5BlacZ, to encode either murine B7-1 or B7-2. B7 molecule expression was detected on the surface of cells infected in vitro and at the RNA level in tissue of immunized mice. Immunization of B7-1/B7-2 knockout mice with B7-encoding virus modestly expanded the number of gamma interferon-producing T cells and significantly augmented class-switched HSV-specific antibody responses compared with the parental virus. Mice immunized with either B7-expressing virus showed less replication of challenge virus in the genital mucosa than mice immunized with 5BlacZ, markedly fewer signs of genital and neurological disease, and little weight loss. Virtually all mice immunized with B7-encoding virus survived challenge with a large dose of HSV-2, whereas most 5BlacZ-immunized mice succumbed to infection. These results indicate that protective immune responses can be enhanced by the inclusion of host B7 costimulation molecules in a prototypical replication-defective HSV vaccine against HSV-2 genital infection and that B7-1 and B7-2 induce immune responses with similar capacities to fight HSV-2 infection.     

Comparison of the significance of CD4+ and CD8+ T lymphocytes in the protection of mice against Encephalitozoon cuniculi infection

The role of T lymphocyte subpopulations in the protection against intraperitoneal (i.p.) and peroral Encephalitozoon cuniculi infections was compared in adoptive-transfer experiments using severe combined immunodeficient mice. Whereas CD8+ T cell-depleted, but not CD4+ T cell-depleted, BALB/c splenocytes failed to protect the mice against i.p. infection, only SCID mice reconstituted with both CD4+ T lymphocyte- and CD8+ T lymphocyte-depleted splenocytes succumbed to peroral infection. The results indicate that whereas CD8+ T cells are critical for the protection against an i.p. E. cuniculi infection, both CD4+ and CD8+ T lymphocyte subpopulations play a substantive protective role in a peroral infection, i.e., natural route of infection.     

Human CD4+ CD25 high cells suppress proliferative memory lymphocyte responses to herpes simplex virus type 2

Lymphocytes with the regulatory CD4+ CD25+ phenotype frequently suppress memory T-cell responses. Murine herpes simplex virus type 1 (HSV-1) models have shown that CD4+ CD25+ cells can limit immunity-mediated corneal damage but slow viral clearance. We investigated the effect of CD4+ CD25+ cells from healthy HSV-2-infected humans on recall proliferative (CD4) responses to HSV-2. Depletion and reconstitution experiments were consistent with a suppressive effect of autologous blood-derived CD4+ CD25+ cells for whole HSV-2 antigen. Regulatory T cells may modulate human CD4 memory responses to HSV-2 and influence their antiviral and inflammatory functions.     

Deletion of IL-4Ralpha on CD4 T cells renders BALB/c mice resistant to Leishmania major infection

Effector responses induced by polarized CD4+ T helper 2 (Th2) cells drive nonhealing responses in BALB/c mice infected with Leishmania major. Th2 cytokines IL-4 and IL-13 are known susceptibility factors for L. major infection in BALB/c mice and induce their biological functions through a common receptor, the IL-4 receptor alpha chain (IL-4Ralpha). IL-4Ralpha-deficient BALB/c mice, however, remain susceptible to L. major infection, indicating that IL-4/IL-13 may induce protective responses. Therefore, the roles of polarized Th2 CD4+ T cells and IL-4/IL-13 responsiveness of non-CD4+ T cells in inducing non-healer or healer responses have yet to be elucidated. CD4+ T cell-specific IL-4Ralpha (Lck(cre)IL-4Ralpha(-/lox)) deficient BALB/c mice were generated and characterized to elucidate the importance of IL-4Ralpha signaling during cutaneous leishmaniasis in the absence of IL-4-responsive CD4+ T cells. Efficient deletion was confirmed by loss of IL-4Ralpha expression on CD4+ T cells and impaired IL-4-induced CD4+ T cell proliferation and Th2 differentiation. CD8+, gammadelta+, and NK-T cells expressed residual IL-4Ralpha, and representative non-T cell populations maintained IL-4/IL-13 responsiveness. In contrast to IL-4Ralpha(-/lox) BALB/c mice, which developed ulcerating lesions following infection with L. major, Lck(cre)IL-4Ralpha(-/lox) mice were resistant and showed protection to rechallenge, similar to healer C57BL/6 mice. Resistance to L. major in Lck(cre)IL-4Ralpha(-/lox) mice correlated with reduced numbers of IL-10-secreting cells and early IL-12p35 mRNA induction, leading to increased delayed type hypersensitivity responses, interferon-gamma production, and elevated ratios of inducible nitric oxide synthase mRNA/parasite, similar to C57BL/6 mice. These data demonstrate that abrogation of IL-4 signaling in CD4+ T cells is required to transform non-healer BALB/c mice to a healer phenotype. Furthermore, a beneficial role for IL-4Ralpha signaling in L. major infection is revealed in which IL-4/IL-13-responsive non-CD4+ T cells induce protective responses.     

CD8+ T lymphocytes protect SCID mice against Encephalitozoon cuniculi infection

Microsporidia are obligate intracellular parasites that cause opportunistic infections in immunocompromised patients. The role of two main T cell subsets in anti-microsporidial immunity has been studied using an Encephalitozoon cuniculi-severe combined immunodeficient (SCID) mouse model. Whereas SCID mice reconstituted with CD4+ T lymphocyte-depleted naive BALB/c splenocytes resolved the infection, adoptive transfer of CD8+ T cell-depleted splenocytes failed to protect the animals against a lethal E. cuniculi infection. Splenocytes from E. cuniculi-immune mice specifically killed syngeneic infected macrophages in a short-term 51Cr-release assay. These results suggest the crucial role of cytotoxic T lymphocytes in the protection against E. cuniculi infection.