CD4+ T cells target epitopes residing within the RNA-binding domain of the U1-70-kDa small nuclear ribonucleoprotein autoantigen and have restricted TCR diversity in an HLA-DR4-transgenic murine model of mixed connective tissue disease.

Mixed connective tissue disease (MCTD) is a systemic autoimmune disease with significant morbidity and premature mortality of unknown pathogenesis. In the present study, we characterized U1-70-kDa small nuclear ribonucleoprotein (70-kDa) autoantigen-specific T cells in a new murine model of MCTD. These studies defined 70-kDa-reactive T cell Ag fine specificities and TCR gene usage in this model. Similar to patients with MCTD, CD4(+) T cells can be readily identified from 70-kDa/U1-RNA-immunized HLA-DR4-transgenic mice. Using both freshly isolated CD4(+) T cells from spleen and lung, and T cell lines, we found that the majority of these T cells were directed against antigenic peptides residing within the RNA-binding domain of 70 kDa. We also found that TCR-beta (TRB) V usage was highly restricted among 70-kDa-reactive T cells, which selectively used TRBV subgroups 1, 2, 6, 8.1, 8.2, and 8.3, and that the TRB CDR3 had conserved sequence motifs which were shared across different TRBV subgroups. Finally, we found that the TRBV and CDR3 regions used by both murine and human 70-kDa-specific CD4(+) T cells were homologous. Thus, T cell recognition of the 70-kDa autoantigen by HLA-DR4-transgenic mice is focused on a limited number of T cell epitopes residing primarily within the RBD of the molecule, using a restricted number of TRBV and CDR3 motifs that are homologous to T cells isolated from MCTD patients.

Direct enumeration of Borrelia-reactive CD4 T cells ex vivo by using MHC class II tetramers.

We characterized antigen-specific CD4(+) T cells in six patients with treatment-resistant Lyme arthritis, using an HLA-DRB1*0401 major histocompatibility complex (MHC) class II tetramer covalently loaded with OspA(164-175), an immunodominant epitope of Borrelia burgdorferi. Direct analysis of OspA-tetramer binding CD4(+) cells in patients expressing the HLA-DRB1*0401 allele revealed frequencies of between <0.005 and 0.1% in peripheral blood (n = 6), and between <0.005 and 3.1% in synovial fluid (n = 3). OspA-tetramer(+)CD4(+) cells were directly cloned at 1 cell per well and expanded by mitogen and IL-2 on allogeneic feeder cells. As measured by [(3)H]thymidine incorporation, 95% of 168 T cell clones from synovial fluid binding the OspA-tetramer were antigen-reactive. Clones generated from peripheral blood revealed a different pattern of responsiveness when compared with clones generated from synovial fluid, as measured by proliferation, IFN-gamma, and IL-13 secretion. These clones, selected on the basis of their peptide binding, also responded to whole protein, but with a different cytokine profile. Our studies demonstrate that MHC class II tetramers can be used in humans to directly identify, isolate, and characterize antigen-reactive T cells from an inflammatory compartment.

Macaques immunized with HLA-DR are protected from challenge with simian immunodeficiency virus.

Macaques immunized with uninfected human cells have been shown to be protected from challenge with simian immunodeficiency virus (SIV) propagated in human cells. To identify the potential antigens involved in this protection, macaques were immunized with uninfected human cells, sucrose density gradient-purified culture fluid from uninfected human cells (mock virus), beta-2 microglobulin (beta 2M), immunoaffinity-purified HLA class I and class II proteins from these human cells, and adjuvant. Although all macaques immunized with beta 2M and HLA class I developed high antibody titers to beta 2M, these animals were not protected from a subsequent challenge with infectious SIV grown in human cells. In contrast, the macaques immunized with class II protein (HLA-DR) and mock virus developed antibodies to class II protein and were protected from the intravenous infectious virus challenge. The class II protein- and mock virus-immunized animals which were protected from challenge were given boosters of the appropriate antigen and challenged with the same SIV propagated in macaque cells. All animals became infected, indicating that the protection seen with human class II protein did not extend to protection from infection with SIV containing macaque class II proteins. Since the virus released from SIV-infected macaque cells would contain macaque class II proteins, our results suggest that the initial SIV infected was completely prevented. In addition, the lack of protection from challenge with SIV propagated in macaque cells provided strong evidence that the protection was due to an immune response to the cellular proteins and not to epitopes cross-reactive between class II proteins and the viral proteins, since the identical virus proteins were present in both challenge stocks. These results are the first demonstration that immunization with a purified cellular protein can protect from virus infection.

The role of macrophages in the pathogenesis of HSV-1 induced chorioretinitis in BALB/c mice.

PURPOSE: To examine the effects of modification of immune effector cells, including macrophages, in the pathogenesis of herpes simplex virus retinitis in BALB/c mice. METHODS: Two intravitreal injections (2 microliters each) of anti-CD11b monoclonal antibody (mAb) [13 micrograms/microliters] were administered to the contralateral eyes of 10 BALB/c mice on days 6 and 8 after HSV inoculation into the right anterior chamber (AC) with HSV-1. A control group consisted of mice injected with anti-HLA-DR mAb in the same fashion. Specific macrophage depletion was performed in an additional group of 12 BALB/c mice by intravenous (i.v.) injection of dichloromethylene diphosphonate (Cl2MDP)-liposomes 7 days before AC HSV-1 inoculation into the eye. Control group consisted of mice receiving i.v. PBS-liposomes. Mice were clinically observed for 14 days postinfection, and the incidence of chorioretinal disease was confirmed by histopathologic studies. RESULTS: Intravitreal injections of anti-CD11b mAb produced a dramatic suppression of the contralateral retinal necrosis (2 of 10 mice) compared to 9 of 10 controls receiving an irrelevant antibody therapy (P < 0.05). Mice treated with i.v. Cl2MDP-liposomes also showed a significant inhibition of the development of contralateral chorioretinitis, with only 3 of 12 mice developing retinal disease compared to 9 of 12 mice from the control group (P < 0.05). FACS analysis performed on peripheral blood and spleen cells showed a significant depletion of Mac-1+ cells of Cl2MDP-liposome-treated but not of PBS-liposome-treated mice (controls). CONCLUSION: Intravitreal anti-CD11b mAb therapy, a broadly directed depletion strategy against many effector cells (macrophages, granulocytes, natural killer cells, and even cytotoxic T-cells) was most efficient in suppressing the HSV-1 induced contralateral disease. A more specific technique (i.v. Cl2MDP-liposome therapy) to deplete macrophages also produced a significant inhibition of HSV-1 induced contralateral chorioretinitis. These findings suggest that macrophages are important participants in the effector phase of the destructive inflammatory immune response induced by HSV-1 in the eye.

Immunochemically purified DR antigens in liposomes stimulate xenogeneic cytolytic T cells in secondary in vitro cultures.

A monoclonal antibody directed against the human class II major histocompatibility antigen DR was generated. Use of this antibody, LB3.1, allowed isolation of large amounts of highly purified DR by immunoaffinity chromatography. The DR was reconstituted into liposomes and shown to stimulate secondary xenogeneic cytolytic T lymphocytes (CTL) specific for targets expressing DR antigens. DR digested with neuraminidase was equally as effective as native DR at stimulating CTL, while denatured DR and other purified membrane proteins were much less effective. The DR liposome-induced CTL lysed only target cells expressing class II antigens. Cytolysis of targets bearing class II antigens was blocked by DR-specific antisera.