Frequency analysis of functional Ig C epsilon gene expression in the presence and absence of interleukin 4 in lipopolysaccharide-reactive murine B cells from high and low IgE responder strains

A mouse model of HIES reveals pro- and anti-inflammatory functions of STAT3

Mutations of STAT3 underlie the autosomal dominant form of hyperimmunoglobulin E syndrome (HIES). STAT3 has critical roles in immune cells and thus, hematopoietic stem cell transplantation (HSCT), might be a reasonable therapeutic strategy in this disease. However, STAT3 also has critical functions in nonhematopoietic cells and dissecting the protean roles of STAT3 is limited by the lethality associated with germline deletion of Stat3. Thus, predicting the efficacy of HSCT for HIES is difficult. To begin to dissect the importance of STAT3 in hematopoietic and nonhematopoietic cells as it relates to HIES, we generated a mouse model of this disease. We found that these transgenic mice recapitulate multiple aspects of HIES, including elevated serum IgE and failure to generate Th17 cells. We found that these mice were susceptible to bacterial infection that was partially corrected by HSCT using wild-type bone marrow, emphasizing the role played by the epithelium in the pathophysiology of HIES.

Codon optimization and mRNA amplification effectively enhances the immunogenicity of the hepatitis C virus nonstructural 3/4A gene

We have recently shown that the NS3-based genetic immunogens should contain also hepatitis C virus (HCV) nonstructural (NS) 4A to utilize fully the immunogenicity of NS3. The next step was to try to enhance immunogenicity by modifying translation or mRNA synthesis. To enhance translation efficiency, a synthetic NS3/4A-based DNA (coNS3/4A-DNA) vaccine was generated in which the codon usage was optimized (co) for human cells. In a second approach, expression of the wild-type (wt) NS3/4A gene was enhanced by mRNA amplification using the Semliki forest virus (SFV) replicon (wtNS3/4A-SFV). Transient tranfections of human HepG2 cells showed that the coNS3/4A gene gave 11-fold higher levels of NS3 as compared to the wtNS3/4A gene when using the CMV promoter. We have previously shown that the presence of NS4A enhances the expression by SFV. Both codon optimization and mRNA amplification resulted in an improved immunogenicity as evidenced by higher levels of NS3-specific antibodies. This improved immunogenicity also resulted in a more rapid priming of cytotoxic T lymphocytes (CTLs). Since HCV is a noncytolytic virus, the functionality of the primed CTL responses was evaluated by an in vivo challenge with NS3/4A-expressing syngeneic tumor cells. The priming of a tumor protective immunity required an endogenous production of the immunogen and CD8+ CTLs, but was independent of B and CD4+ T cells. This model confirmed the more rapid in vivo activation of an NS3/4A-specific tumor-inhibiting immunity by codon optimization and mRNA amplification. Finally, therapeutic vaccination with the coNS3/4A gene using gene gun 6-12 days after injection of tumors significantly reduced the tumor growth in vivo. Codon optimization and mRNA amplification effectively enhances the overall immunogenicity of NS3/4A. Thus, either, or both, of these approaches should be utilized in an NS3/4A-based HCV genetic vaccine.

Impact of V beta 8+/+ T cells on the development of increased airway reactivity and IgE production in SJL mice

SJL mice have been extensively characterized as "low-responder" animals in terms of IgE-dependent immediate-type hypersensitivity responses. Since these mice are genetically deficient in certain TCR Vbeta gene segments, we asked whether this might be the reason for the "low-responder" status. Specifically in H-2d mice the TCR-Vbeta8.2 gene element has been shown to play an important role in Th2 immune responses to ovalbumin (OVA). Utilizing a TCR Vbeta8. 2-transgenic SJL (SJL Vbeta8+/+) mouse, we examined whether the H-2s -bearing "low-responder" mouse could be converted into a "high-responder" animal. Remarkably, non-sensitized SJL Vbeta8+/+ mice demonstrated strongly elevated levels of total IgE antibody. Mitogen-stimulated T cells from these mice released high amounts of IL-4 as compared to SJL wild-type (wt) mice. In addition, sensitization to OVA via the airways resulted in the development of increased airway responsiveness in SJL Vbeta8+/+ mice, but not in SJL wt animals. The results indicate that the capacity to produce IgE and IL-4 and to develop increased airway responsiveness can be restored in SJL wt mice by introducing the Vbeta8.2 gene segment into the TCR repertoire.

Vbeta8+ T lymphocytes are essential in the regulation of airway hyperresponsiveness and bronchoalveolar eosinophilia but not in allergen-specific IgE in a murine model of allergic asthma

BACKGROUND

There is increasing evidence that in allergic asthma the inflammatory process is regulated by T lymphocytes. In BALB/c mice the majority of ovalbumin responsive T lymphocytes express the Vbeta8.1+ and Vbeta8.2+ T-cell receptor.

OBJECTIVE

We analysed the contribution of Vbeta8+ T lymphocytes during the sensitization and challenge phase in the regulation of antigen-specific IgE, airway hyperresponsiveness and cellular infiltration in the airways in a murine model of allergic asthma.

METHODS

Mice strains genetically lacking (SJL/J and SJA/9) and expressing (BALB/c) the Vbeta8+ T cell receptor were used. In addition, prior to the sensitization and prior to the challenge BALB/c mice were treated with antibodies to Vbeta8. Mice were sensitized with ovalbumin, followed by repeated challenge with ovalbumin or saline aerosols.

RESULTS

In ovalbumin challenged BALB/c mice treated with control antibody a significant increase in eosinophils in the bronchoalveolar lavage, airway hyperresponsiveness and increased serum levels of ovalbumin-specific IgE were observed compared to control mice. Treatment of BALB/c mice with antibodies to Vbeta8 prior to the sensitization or prior to the challenge period completely inhibited the ovalbumin induced infiltration of eosinophils and airway hyperresponsiveness, while ovalbumin-specific IgE was slightly decreased. In SJA/9 and SJL/J mice ovalbumin challenge did not induce eosinophilic infiltration and airway hyperresponsiveness. In SJL/J mice ovalbumin challenge induced an upregulation of ovalbumin-specific IgE, however, in SJA/9 mice no upregulation was observed.

CONCLUSION

It is demonstrated that Vbeta8+ T lymphocytes are essential for infiltration of eosinophils in the airways and development of airway hyperresponsiveness in a murine model of allergic asthma. In contrast, although Vbeta8+ T lymphocytes seem to be important for the extent of IgE levels, no essential role for Vbeta8+ T lymphocytes in the induction of antigen-specific IgE was observed.

CD8+ T cells inhibit immunoglobulin E synthesis in low responder SJL/J mice

In an effort to examine the basis for low IgE responsiveness of SJL/J strain mice, we analysed the profiles of cytokines, such as interleukin-2 (IL-2), IL-4 and interferon-gamma (IFN-gamma), in SJL/J and A.SW/SnJ mice following immunization. Splenocytes of ovalbumin (OVA)-immunized SJL/J mice, secreted significantly higher levels of IL-4 and lower levels of IFN-gamma than those of A.SW/SnJ mice. A time-course analysis of cytokine expression in in vitro cultures of spleen cells indicated that the levels of IL-4 and IL-2 remained persistently high throughout in the cultures of SJL/J splenocytes as opposed to those of A.SW/SnJ. Depletion of CD4+ T cells in vivo suppressed the production of IL-2, IL-4 and IFN-gamma suggesting that CD4 T cells are the producers of most cytokines in both SJL/J and A.SW/SnJ mice. Depletion of CD8+ T cells in vivo not only induced productive epsilon transcript but also enhanced IgE production in SJL/J mice. Moreover, CD8 depletion in SJL/J mice led to decreased production of IFN-gamma, resulting in a net decrease in the ratio of IFN-gamma to IL-4. A similar shift in the IFN-gamma/IL-4 ratio was found in splenocytes of SJL/J mice following irradiation, which is known to enhance IgE synthesis in these mice. Taken together, it is concluded that low IgE responsiveness in SJL/J mice is not due to a defect in IL-4 production per se. Increased IFN-gamma production by the CD8+ T cells inhibits class switch and suppresses IgE antibody production in SJL/J mice.

Immunomodulatory properties of a strain of Mycobacterium chelonae--II. Qualitative and quantitative stimulation of mouse splenocytes by Mycobacterium chelonae

Intraperitoneal [i.p.] and subcutaneous [s.c.] administration to BALB/C mice with a single dose of 5 mg/kg body weight (wet weight) of live Mycobacterium chelonae (Mch) augmented splenocyte blastogenesis. Similar increases in splenocyte blastogenesis manifested during a single oral administration to mice with 100 mg/kg body weight (wet weight) of this Mycobacterium. When splenocytes issued from these mice are activated by mitogens, a highly significant enhancement of lymphoblastic transformation was observed. On the other hand, multiple oral administrations with 50 mg/kg body weight (wet weight) to Mch/dose did not manifest statistically significant differences in splenocyte blastogenesis as compared to controls. Meanwhile, a highly increased transformation of splenocytes, issued from such mice, is observed in response to lectins and to the mitogenic effect of this microorganism. Splenocyte counts have shown 44.5, 37.6, and 23.2% increases in response to i.p., s.c. and multiple oral administration of this bacterium, respectively, as compared to solvent controls. Repeated s.c. administration of this mycobacterium manifested short lived and weak syndromes of anaphylactic shock during and immediately after the second inoculation of Mch. This phenomenon is not observed during repeated intraperitoneal and oral administrations. In conclusion, parenteral (i.p. and s.c.) and oral administration of Mch stimulates the immune system of mice. This effect is characterised by increased in vivo cell multiplication and by enhanced ex vivo DNA synthesis of murine splenocytes. The need of further studies is eminent to elucidate classes of immunocompetent cells involved in this phenomenon.

Regulation of IgG1 and IgE synthesis by interleukin 4 in mouse B cells

Mouse interleukin 4 (IL-4) has been shown to act on B cells as an induction factor for Ig class switch. We studied the characteristics of IL-4-regulated Ig isotype production in lipopolysaccharide (LPS)-stimulated splenic B-cell cultures with emphasis on the comparison between the IgG1 and IgE responses. The results show that the kinetics for the appearance of IgG1 and IgE isotypes are similar, but that the dose of IL-4 required for the induction of an IgE response is 3-10 times higher than that for an IgG1 response. No requirement for T cells was found for the induction of either isotype. Pre-incubation of cells for 24 h with IL-4 alone was sufficient to induce an IgG1 response when cells were recultured with LPS from days 1 to 6. However, the simultaneous presence of both IL-4 and LPS for at least 24 h was required for a detectable IgE response. For an optimal IgE response, IL-4 needed to be present for more than 72 h in LPS-activated cultures. The possible reasons for the different regulation of IgG1 and IgE responses are discussed.