Both immunisation with a formalin-inactivated respiratory syncytial virus (RSV) vaccine and a mock antigen vaccine induce severe lung pathology and a Th2 cytokine profile in RSV-challenged mice.

Respiratory syncytial virus (RSV) is the most important cause of bronchiolitis and pneumonia in infants and young children. Immunopathology may play a role in RSV-induced disease and a severe RSV infection may also be associated with an increased risk of developing asthma. Vaccination with formalin-inactivated RSV (FI-RSV) prior to infection resulted both in human and in the mouse model in extensive lung pathology. In the mouse model, it has been shown that this aggravation of disease was associated with a shift in the balance between Th1 and Th2 cytokines towards a Th2-type response. The aim of the present study was to characterise the immunological and inflammatory responses in BALB/c mice upon RSV infection with or without prior vaccination with aluminium-adjuvanted FI-RSV or control antigens (FI-Mock). As previously reported by others, we also observed that a primary RSV infection in BALB/c mice resulted in a predominant Th1-type cytokine response, which was associated with slight bronchiolitis and alveolitis. FI-RSV vaccination prior to RSV challenge prevented virus replication and was associated with an aggravation of pulmonary histopathology and a shift towards a Th2-type response. Vaccination with FI-Mock did not prevent RSV replication in the lung but resulted in an even more pronounced Th2 response after infection while these mice were not sensitised to specific viral antigens. Thus, viral replication in a Th2 responding animal (induced by aluminium-adjuvanted mock vaccine) appears to boost the Th2 response upon RSV infection.

Toxocara-induced eosinophilic inflammation. Airway function and effect of anti-IL-5.

The immunoinflammatory response to parasitic nematode infections and allergic diseases have some similarities, the most profound being the increases in eosinophils and serum total IgE concentration. Whether parasitic infections stimulate or inhibit allergic asthma is a matter of debate. We investigated the effect of Toxocara canis (T. canis) infection on airway function in BALB/c mice at various days post-infection. Within 24 h after infection, the trachea responded hyperreactive to carbachol stimulation. Eosinophils, and to a lesser degree lymphocytes, infiltrated the airways causing interstitial and alveolar inflammation (7 d post-infection). Concurrently with cell infiltration, the trachea became hyporesponsive to carbachol whereas the pulmonary resistance was increased and the dynamic compliance decreased. The hyporeactive response could be simulated in vitro by incubating normal tracheae with eosinophil-enriched bronchoalveolar lavage cells obtained from infected mice. The response depended on the number of cells added to the medium, a lower number causing a hyper- and a higher number a hyporeactive response. Anti-interleukin-5 (anti-IL-5) producing hybridoma cells given simultaneously with T. canis infection inhibited eosinophil infiltration in the airways but not that of lymphocytes. Anti-IL-5 treatment prevented tracheal hyporeactivity but not perivascular and peribronchial edema, increased pulmonary resistance, or decreased dynamic compliance. Treatment with isotype control antibody did not affect eosinophil number nor the observed changes in airway functions. It was concluded that T. canis-induced airway inflammation coincided with increased pulmonary resistance, decreased dynamic compliance, and perivascular/peribronchial edema. These phenomena were independent on the presence of eosinophils, whereas tracheal hyporeactivity was clearly associated with airway eosinophilia.

Toxocara canis-induced murine pulmonary inflammation: analysis of cells and proteins in lung tissue and bronchoalveolar lavage fluid.

The pulmonary immuno-inflammatory reaction and its effect on microvascular integrity was studied in Toxocara canis infected BALB/c mice. The investigation aimed to compare changes in lung histology and composition of bronchoalveolar lavage fluid (BALF) caused by T. canis infection with those described to occur in allergic asthma. Groups of (non)-infected mice (1000 ova) were investigated until 90 days post infection (p.i.). Migration of the larvae through the lungs was followed by a rapidly progressing multifocal interstitial and alveolar inflammation. Eosinophils and lymphocytes formed perivascular and partially peribronchial mixed cellular infiltrates. Lymphocytes with plasma cell morphology staining intracellularly for either alpha, epsilon or gamma immunoglobulins were demonstrated. BALF, collected from mice infected with either 250, 500 or 1000 ova was analysed at 14 and 28 days p.i. A dose-related increase in cell numbers and in albumin and IgA concentration was observed. IgE increase was independent of the infective dose. Peak values were measured at 14 days p.i. Albumin increase in lung homogenate was highest at 28 days p.i. 30% of the lymphocytes consisted of T cells carrying Thy-1,2 and L3T4 surface antigens. It is concluded that T. canis-induced pulmonary inflammation affects the permeability of the microvasculature. This is expressed by interstitial oedema and plasma exudation in the airway lumen. Both phenomena occur also in allergic asthma. It is suggested that increased permeability of the microvasculature is mediated by T cells and eosinophils.

Specificity and frequency of primary anti-HLA cytotoxic T lymphocytes in normal and HLA-B27.2-, HLA-B27.5-, and HLA-Cw3-transgenic mice. A transgenic model for MHC xenoantigen recognition.

Previous studies have shown that the lymphocytes of naive mice produce a strong primary CTL responses in vitro to human MHC class I Ag presented by HLA-transgenic mouse (TGM) cells. A limiting dilution (LD) assay was used to analyze this xenoreactive CTL repertoire in mice. Frequencies of HLA class I-specific CTL precursors (CTLp) were estimated in naive normal and HLA-B27.2-, -B27.5- and HLA-Cw3-double TGM (i.e., mice expressing HLA and human beta 2-microglobulin (hu beta 2m]. The xenoreactive CTLp frequencies were compared to frequencies of CTLp to H-2 alloantigens estimated in naive normal mice. The results showed that the frequencies of HLA class I-specific CTLp are comparable with those of alloreactive CTLp. This overlap in CTLp frequencies suggests that HLA class I xenoantigens are recognized by primary mouse CTL as allelic variants of H-2K and H-2D. This was confirmed in split well analysis by the observation that the xenoreactive response was not restricted by self-MHC of the responding mouse. Thus, primary HLA class I-specific mouse CTL clones recognized their target Ag regardless of whether they were expressed on H-2-mismatched mouse cells or on human cells. The frequencies of HLA class I-specific CTLp in HLA-TGM were comparable to those in normal mice. We propose that MHC allo- and xenoreactive CTL responses are not caused by the activation of CTLp specific for self-MHC plus peptide but to the activation of CTLp recognizing MHC allo- and xenoantigens directly or as peptides presented by their native MHC molecules.

Abnormal anti-viral immune response in mice is corrected in HLA-B27.2-transgenic mice.

In contrast to the strong Sendai virus-specific cytotoxic T-lymphocyte (CTL) responses in C57BL/6 mice. H-2Kb mutant bm1 mice are nonresponders to Sendai virus. By appropriate crossings between HLA-B27 double-transgenic mice and Kb mutant bm1 mice, and after subsequent selection, H-2bm1 homozygous mice were produced expressing the human HLA-B27.2 and beta 2-microglobulin genes. Here we show that the introduction of a human HLA class I gene into the genome of the H-2bm1 Sendai virus-nonresponder mutant mice resulted in good responsiveness to Sendai virus, and in normal levels of Sendai virus-specific CTL precursors. The CTL response in the HLA-B27.2 double-transgenic H-2bm1 mice against Sendai virus was restricted by the HLA-B27.2 molecule. These results show the direct involvement of HLA class I molecules in regulation of the anti-viral CTL repertoire and represent for the first time a correction of abnormal anti-viral immunity in mice by incorporation of a human MHC class I (HLA-B27.2) gene.

HLA expression and function in single and double HLA-B27-transgenic mice.

The expression and function of HLA antigens in mice single transgenic for HLA-B27.2 (sTGM-B27.2) or double transgenic (dTGM) for HLA-B27.2 and human beta 2-microglobulin (h beta 2m) were compared. B27.2 could be well detected on the cell membrane of lymphocytes of sTGM. However, the expression in sTGM was much lower than in dTGM mice. Nevertheless, also in sTGM mice, the B27-transgene product possessed all functional properties of a class I HLA molecule. This was shown by the recognition and induction of antibodies and cytotoxic T cells, by the induction of "allo"-immunity, including skin graft rejection, and by the ability to present viral antigens. In dTGM, the expression of B27 on peripheral blood lymphocytes, spleen and lymphnode cells was comparable to H-2. However, on thymocytes, a relatively lower expression of HLA than H-2 was observed. This low expression of B27 on thymocytes is in concert with the observation that B27 is expressed only in the medulla of the thymus and not detectable in the cortex.

Recognition of xeno-(HLA, SLA) major histocompatibility complex antigens by mouse cytotoxic T cells is not H-2 restricted: a study with transgenic mice.

Cytotoxic T lymphocytes (CTLs) recognize antigens in the context of major histocompatibility complex (MHC) class I gene products. The T-cell receptor (TCR) that mediates this MHC-restricted antigen recognition recognizes short peptide fragments rather than the intact antigen. Presentation of peptides to the TCR may thus be a major function of the MHC. An intriguing question emerging from this model is whether peptide presentation also applies to foreign MHC antigens and which of the available MHC molecules can present preferentially the peptides of the foreign MHC molecule. Allo- and xenoreactive CTLs might either recognize native MHC class I molecules or peptides presented by self MHC or by the foreign class I MHC itself. The finding that synthetic peptides corresponding to MHC class I regions are recognized by allo- and xenoreactive CTLs suggests that recognition of foreign MHC by CTLs might involve degraded fragments presented by syngeneic class I molecules. We used MHC transgenic mice as a tool to study these questions. The CTL responses against human (HLA) antigen B27 were analyzed by using HLA-B27 transgenic mice with various H-2 haplotypes. We report here that mouse xeno-MHC-specific (anti-B27) CTLs are perfectly able to kill human and mouse cells expressing the appropriate xenoantigen and that in primary and secondary responses to xeno-MHC, the mouse T-cell repertoire does not use self-H-2 as a restriction element. Absence of H-2 restriction was confirmed by the lack (less than 1/10(6] of H-2-restricted HLA-specific CTL precursors. Therefore, H-2-restricted recognition of xeno-MHC antigens cannot be generalized as part of a classical MHC class I-specific response. These results indicate that xenoreactive CTLs usually recognize intact MHC molecules or MHC peptides preferentially presented by their native MHC molecule. We suggest the latter possibility.