Antiviral immune responses in the absence of organized lymphoid T cell zones in plt/plt mice

The paucity of lymph node (LN) T cells (plt) mutation in mice results in strongly reduced T cell numbers in LNs and homing defects of both dendritic cells (DCs) and naive T cells. In this study, we investigated the functional significance of the plt phenotype for the generation of antiviral immune responses against cytopathic and noncytopathic viruses. We found that DC-CD8(+) T cell contacts and the initial priming of virus-specific T cells in plt/plt mice occurred mainly in the marginal zone of the spleen and in the superficial cortex of LNs. The magnitude of the initial response and the maintenance of protective memory responses in plt/plt mice was only slightly reduced compared with plt/+ controls. Furthermore, plt/plt mice mounted rapid neutralizing antiviral B cell responses and displayed normal Ig class switch. Our data indicate that the defective homing of DCs and naive T cells resulting from the plt/plt mutation results in a small, but not significant, effect on the induction of protective antiviral T and B cell immunity. Overall, we conclude that the spatial organization of secondary lymphoid T cell zones via the CCR7-CC chemokine ligand 19/CC chemokine ligand 21 pathway is not an absolute requirement for the initial priming and the maintenance of protective antiviral T and B cell responses.     

Diagnostic criteria for diabetes revisited: making use of combined criteria

Background  

Existing cut-offs for fasting plasma glucose (FPG) and post-load glucose (2hPG) criteria are not equivalent in the diagnosis of diabetes and glucose intolerance. Adjusting cut-offs of single measurements have not helped so we undertook this project to see if they could be complementary.     

Targeted inactivation of the tetraspanin CD37 impairs T-cell-dependent B-cell response under suboptimal costimulatory conditions

CD37 is a membrane protein of the tetraspanin superfamily, which includes CD9, CD53, CD63, CD81, and CD82. Many of these molecules are expressed on leukocytes and have been implicated in signal transduction, cell-cell interactions, and cellular activation and development. We generated and analyzed mice deficient for CD37. Despite the high expression of CD37 on cells of the immune system, no changes in development and cellular composition of lymphoid organs were observed in mice lacking CD37. Analyses of humoral immune responses revealed a reduced level of immunoglobulin G1 (IgG1) in the sera of nonimmunized mice and an alteration of responses to T-cell-dependent antigens. Antibody responses to model antigen administered in the absence of adjuvant and to viral infections were generally poor in CD37-deficient mice. These poor antibody responses could be overcome by the immunization of antigen together with adjuvant. These results suggest a role for CD37 in T-cell-B-cell interactions which manifests itself under suboptimal costimulatory conditions.     

IL-4 and IL-10 antagonize IL-12-mediated protection against acute vaccinia virus infection with a limited role of IFN-gamma and nitric oxide synthetase 2

Resistance or susceptibility to most infectious diseases is strongly determined by the balance of type 1 vs type 2 cytokines produced during infection. However, for viruses, this scheme may be applicable only to infections with some cytopathic viruses, where IFN-gamma is considered as mandatory for host defense with little if any participation of type 2 responses. We studied the role of signature Th1 (IL-12, IFN-gamma) and Th2 (IL-4, IL-10) cytokines for immune responses against vaccinia virus (VV). IL-12-/- mice were far more susceptible than IFN-gamma-/- mice, and primary CTL responses against VV were absent in IL-12-/- mice but remained intact in IFN-gamma-/- mice. Both CD4+ and CD8+ T cells from IL-12-/- mice were unimpaired in IFN-gamma production, although CD4+ T cells showed elevated Th2 cytokine responses. Virus replication was impaired in IL-4-/- mice and, even more strikingly, in IL-10-/- mice, which both produced elevated levels of the proinflammatory cytokines IL-1alpha and IL-6. Thus, IL-4 produced by Th2 cells and IL-10 produced by Th2 cells and probably also by macrophages counteract efficient anti-viral host defense. Surprisingly, NO production, which is considered as a major type 1 effector pathway inhibited by type 2 cytokines, appears to play a limited role against VV, because NO sythetase 2-deficient mice did not show increased viral replication. Thus, our results identify a new role for IL-12 in defense beyond the induction of IFN-gamma and show that IL-4 and IL-10 modulate host protective responses to VV.     

Enhanced Virus Clearance by Early Inducible Lymphocytic Choriomeningitis Virus-Neutralizing Antibodies in Immunoglobulin-Transgenic Mice

Following infection of mice with lymphocytic choriomeningitis virus (LCMV), virus-neutralizing antibodies appear late, after 30 to 60 days. Such neutralizing antibodies play an important role in protection against reinfection. To analyze whether a neutralizing antibody response which developed earlier could contribute to LCMV clearance during the acute phase of infection, we generated transgenic mice expressing LCMV-neutralizing antibodies. Transgenic mice expressing the immunoglobulin μ heavy chain of the LCMV-neutralizing monoclonal antibody KL25 (H25 transgenic mice) mounted LCMV-neutralizing immunoglobulin M (IgM) serum titers within 8 days after infection. This early inducible LCMV-neutralizing antibody response significantly improved the host’s capacity to clear the infection and did not cause an enhancement of disease after intracerebral (i.c.) LCMV infection. In contrast, mice which had been passively administered LCMV-neutralizing antibodies and transgenic mice exhibiting spontaneous LCMV-neutralizing IgM serum titers (HL25 transgenic mice expressing the immunoglobulin μ heavy and the κ light chain) showed an enhancement of disease after i.c. LCMV infection. Thus, early-inducible LCMV-neutralizing antibodies can contribute to viral clearance in the acute phase of the infection and do not cause antibody-dependent enhancement of disease.Against many cytopathic viruses such as poliovirus, influenza virus, rabies virus, and vesicular stomatitis virus, protective virus-neutralizing antibodies are generated early, within 1 week after infection (3, 31, 36, 44, 49). In contrast, several noncytopathic viruses (e.g., human immunodeficiency virus and hepatitis viruses B and C in humans or lymphocytic choriomeningitis virus [LCMV] in mice) elicit poor and delayed virus-neutralizing antibody responses (1, 7, 20, 24, 27, 35, 45, 48).In the mouse, the natural host of LCMV, the acute LCMV infection is predominantly controlled by cytotoxic T lymphocytes (CTLs) in an obligatory perforin-dependent manner (13, 18, 28, 50). In addition to the CTL response, LCMV-specific antibodies are generated. Early after infection (by day 8), a strong antibody response specific for the internal viral nucleoprotein (NP) is mounted (7, 19, 23, 28). These early LCMV NP-specific antibodies exhibit no virus-neutralizing capacity (7, 10). Results from studies of B-cell-depleted mice and B-cell-deficient mice implied that the early LCMV NP-specific antibodies are not involved in the clearance of LCMV (8, 11, 12, 40). Late after infection (between days 30 and day 60), LCMV-neutralizing antibodies develop (7, 19, 22, 28, 33); these antibodies are directed against the surface glycoprotein (GP) of LCMV (9, 10). LCMV-neutralizing antibodies have an important function in protection against reinfection (4, 6, 38, 41, 47).In some viral infections, subprotective virus-neutralizing antibody titers can enhance disease rather than promote host recovery (i.e., exhibit antibody-dependent enhancement of disease [ADE] [14, 15, 21, 46]). For example, neutralizing antibodies are involved in the resolution of a primary dengue virus infection and in the protection against reinfection. However, if subprotective neutralizing antibody titers are present at the time of reinfection, a severe form of the disease (dengue hemorrhagic fever/dengue shock syndrome [15, 21]), which might be caused by Fc receptor-mediated uptake of virus-antibody complexes leading to an enhanced infection of monocytes (15, 16, 25, 39), can develop. Similarly, an enhancement of disease after intracerebral (i.c.) LCMV infection was observed in mice which had been treated with virus-neutralizing antibodies before the virus challenge (6). ADE in LCMV-infected mice was either due to an enhanced infection of monocytes by Fc receptor-mediated uptake of antibody-virus complexes or due to CTL-mediated immunopathology caused by an imbalanced virus spread and CTL response.To analyze whether LCMV-neutralizing antibodies generated early after infection improve the host’s capacity to clear the virus or enhance immunopathological disease, immunoglobulin (Ig)-transgenic mice expressing LCMV-neutralizing IgM antibodies were generated. After LCMV infection of transgenic mice expressing the Ig heavy chain (H25 transgenic mice), LCMV-neutralizing serum antibodies were mounted within 8 days, which significantly improved the host’s capacity to eliminate LCMV. H25 transgenic mice did not show any signs of ADE after i.c. LCMV infection.Transgenic mice expressing the Ig heavy and light chains (HL25 transgenic mice) exhibited spontaneous LCMV-neutralizing serum antibodies and confirmed the protective role of preexisting LCMV-neutralizing antibodies, even though the neutralizing serum antibodies were of the IgM isotype. Similar to mice which had been treated with LCMV-neutralizing antibodies, HL25 transgenic mice developed an enhanced disease after i.c. LCMV infection, which indicated that ADE was due to an imbalance between virus spread and CTL response. Thus, the early-inducible LCMV-neutralizing antibody response significantly enhanced clearance of the acute infection without any risk of causing ADE.     

Isolation and characterization of highly pathogenic avian influenza virus subtype H5N1 from donkeys

Background  

The highly pathogenic H5N1 is a major avian pathogen that crosses species barriers and seriously affects humans as well as some mammals. It mutates in an intensified manner and is considered a potential candidate for the possible next pandemic with all the catastrophic consequences.     

<Emphasis Type="Italic">TRAF1/C5</Emphasis>polymorphism is not associated with increased mortality in rheumatoid arthritis: two large longitudinal studies

Introduction  

Recently an association between a genetic variation in TRAF1/C5 and mortality from sepsis or cancer was found in rheumatoid arthritis (RA). The most prevalent cause of death, cardiovascular disease, may have been missed in that study, since patients were enrolled at an advanced disease stage. Therefore, we used an inception cohort of RA patients to investigate the association between TRAF1/C5 and cardiovascular mortality, and replicate the findings on all-cause mortality. As TRAF1/C5 associated mortality may not be restricted to RA, we also studied a large cohort of non-RA patients.     

CXCR5-dependent seeding of follicular niches by B and Th cells augments antiviral B cell responses

The chemokine receptor CXCR5 and its ligand CXCL13 define the structure of B cell follicles within secondary lymphoid organs. Here, we examined the impact of CXCR5 on antiviral B cell responses in vivo. CXCR5-/- mice showed a normal production of IgM and IgG acutely after infection with vesicular stomatitis virus (VSV) and developed VSV-specific germinal centers. However, impaired Ig class switch and Ab production were observed under conditions of limited availability of Ag (i.e., after immunization with nonreplicating viral particles or soluble Ag). Adoptive transfer of CXCR5-deficient, VSV-specific B and Th cells demonstrated that CXCR5 expression on both B and Th cells is required for an efficient Ig class switch. These experiments revealed that CXCR5 is critical for the coordinated interaction of antiviral T and B cells through its impact on initial B cell expansion and the recruitment of Ag-specific B and Th cells to germinal centers.     

The accuracy of several multiple sequence alignment programs for proteins

Background  

There have been many algorithms and software programs implemented for the inference of multiple sequence alignments of protein and DNA sequences. The "true" alignment is usually unknown due to the incomplete knowledge of the evolutionary history of the sequences, making it difficult to gauge the relative accuracy of the programs.     

On single and multiple models of protein families for the detection of remote sequence relationships

Background  

The detection of relationships between a protein sequence of unknown function and a sequence whose function has been characterised enables the transfer of functional annotation. However in many cases these relationships can not be identified easily from direct comparison of the two sequences. Methods which compare sequence profiles have been shown to improve the detection of these remote sequence relationships. However, the best method for building a profile of a known set of sequences has not been established. Here we examine how the type of profile built affects its performance, both in detecting remote homologs and in the resulting alignment accuracy. In particular, we consider whether it is better to model a protein superfamily using a single structure-based alignment that is representative of all known cases of the superfamily, or to use multiple sequence-based profiles each representing an individual member of the superfamily.