The effect of bacillus Calmette-Guérin immunization depends on the genetic predisposition to Th2-type responsiveness

Prime-boost BCG vaccination with DNA vaccines based in β-defensin-2 and mycobacterial antigens ESAT6 or Ag85B improve protection in a tuberculosis experimental model

The World Health Organization (WHO) has estimated that there are about 8 million new cases annually of active Tuberculosis (TB). Despite its irregular effectiveness (0-89%), the Bacillus Calmette-Guérin) BCG is the only vaccine available worldwide for prevention of TB; thus, the design is important of novel and more efficient vaccination strategies. Considering that β-defensin-2 is an antimicrobial peptide that induces dendritic cell maturation through the TLR-4 receptor and that both ESAT-6 and Ag85B are immunodominant mycobacterial antigens and efficient activators of the protective immune response, we constructed two DNA vaccines by the fusion of the gene encoding β-defensin-2 and antigens ESAT6 (pDE) and 85B (pDA). After confirming efficient local antigen expression that induced high and stable Interferon gamma (IFN-γ) production in intramuscular (i.m.) vaccinated Balb/c mice, groups of mice were vaccinated with DNA vaccines in a prime-boost regimen with BCG and with BCG alone, and 2 months later were challenged with the mild virulence reference strain H37Rv and the highly virulent clinical isolate LAM 5186. The level of protection was evaluated by survival, lung bacilli burdens, and extension of tissue damage (pneumonia). Vaccination with both DNA vaccines showed similar protection to that of BCG. After the challenge with the highly virulent Mycobacterium tuberculosis strain, animals that were prime-boosted with BCG and then boosted with both DNA vaccines showed significant higher survival and less tissue damage than mice vaccinated only with BCG. These results suggest that improvement of BCG vaccination, such as the prime-boost DNA vaccine, represents a more efficient vaccination scheme against TB.

Pulmonary cryptococcosis induces chitinase in the rat

Background

We previously demonstrated that chronic pulmonary infection with Cryptococcus neoformans results in enhanced allergic inflammation and airway hyperreactivity in a rat model. Because the cell wall of C. neoformans consists of chitin, and since acidic mammalian chitinase (AMCase) has recently been implicated as a novel mediator of asthma, we sought to determine whether such infection induces chitinase activity and expression of AMCase in the rat.

Methods

We utilized a previously-established model of chronic C. neoformans pulmonary infection in the rat to analyze the activity, expression and localization of AMCase.

Results

Our studies indicate that intratracheal inoculation of C. neoformans induces chitinase activity within the lung and bronchoalveolar lavage fluid of infected rats. Chitinase activity is also elicited by pulmonary infection with other fungi (e.g. C. albicans), but not by the inoculation of dead organisms. Enhanced chitinase activity reflects increased AMCase expression by airway epithelial cells and alveolar macrophages. Systemic cryptococcosis is not associated with increased pulmonary chitinase activity or AMCase expression.

Conclusion

Our findings indicate a possible link between respiratory fungal infections, including C. neoformans, and asthma through the induction of AMCase.

Respiratory syncytial virus infection reversed anti-asthma effect of neonatal Bacillus Calmette-Guerin vaccination in BALB/c mice

Bacillus Calmette-Guerin (BCG) vaccination can protect animals from asthma, but the effect of BCG on childhood asthma prevention is controversial in humans. To verify the hypothesis that the BCG anti-asthma effect in childhood might be reversed by a respiratory virus infection, newborn BALB/c mice were divided into five groups. Control and ovalbumin (OVA) groups were mock vaccinated and mock infected. The BCG/OVA group was BCG vaccinated and mock infected. The respiratory syncytial virus (RSV)/OVA group was mock vaccinated and RSV infected. The BCG/RSV/OVA group was BCG vaccinated and RSV infected. Except for the control group, all groups underwent OVA sensitization and challenge. Airway hyperresponsiveness (AHR) was measured after challenge and cells in bronchoalveolar lavage fluid (BALF) were counted. Cytokines in BALF and serum OVA-specific IgE were detected by ELISA and inflammatory characteristics of lung sections were scored. Mice with neonatal BCG vaccination (BCG/OVA group) were significantly protected from BALF eosinophilia, AHR to methacholine, peribronchiolitis, alveolitis, and peribronchial eosinophilia in comparison with the OVA, RSV/OVA, and BCG/RSV/OVA groups. AHR in the OVA group was greater than in the BCG/OVA group but lower than in the RSV/OVA and BCG/RSV/OVA groups. No significant differences in BALF eosinophilia, AHR, and lung inflammation were found between the RSV/OVA and BCG/RSV/OVA groups. The impact of BCG vaccination on anti-asthma in mice was not dependent on interferon-gamma, IL-4, and IL-10 levels. The results suggested that RSV infection can reverse the anti-asthma effect of neonatal BCG vaccination in BALB/c mice.

BCG vaccine modulates intestinal and systemic response to beta-lactoglobulin

Beta-Lactoglobulin (BLG) is a clinically important antigen in cow's milk and one of the major allergens causing cow's milk allergy. Bacillus Calmette-Guerin (BCG) vaccination has been suggested to modify immune response possibly decreasing the risk of allergy to some antigens in both human and experimental animals. In the present study, we have analyzed whether the early BCG vaccination has any effect on the markers of systemic and gastrointestinal (GI) sensitization to BLG. We immunized two groups of Hooded-Lister rat puppets with intraperitoneal injections of native BLG at 43 and 62 days with pertussis vaccine as adjuvant, one group receiving additionally BCG. The animals were then fed native and denatured milk products twice weekly from 73 to 131 days of age, when they were killed. Control group was not vaccinated and received normal rat forage. Total immunoglobulin E (IgE) levels and BLG-specific IgG(1) and IgG(2a) concentrations were determined in serum samples. Spontaneous interleukin (IL)-4 and interferon (IFN)-gamma production from duodenal specimens were measured, and the inflammatory cells were quantitated in specimens from different sections of the GI tract. Administration of BCG simultaneously with BLG resulted in reduced IgE concentration in serum, while the specific IgG(1) and IgG(2a) antibody responses and the spontaneous secretion of IL-4 and IFN-gamma were not affected. Furthermore, BCG-induced eosinophilic infiltration and increase of intraepithelial lymphocytes (IEL) in the GI mucosa, and a trend toward increased number of lamina propria mononuclear inflammatory cells in the colon (BCG compared with BLG, p = 0.09; BCG compared with controls, p = 0.02). Controls showed increment of IgG(1) response in comparison with the BLG group (p = 0.04) and increase of mucosal eosinophilic infiltration. The BCG modified the response to BLG both at the systemic level as shown by decrease of total IgE and at GI mucosa where increase of eosinophilic infiltration and increased number of IEL were seen. Increment of IgG(1) level and eosinophils in the controls might be related with the lack of modulatory effect of pertussis vaccination. A shift of response toward the lower GI tract after BCG immunization as shown by a trend for increase of mononuclear inflammatory cells in colon lamina propria mimics disease development in some cases of clinical food allergy, and emphasizes the need for evaluation of the changes in the whole GI tract in food allergy models.

Immunotherapy with mycobacteria

PURPOSE OF REVIEW

To summarize and evaluate critically recent progress with mycobacteria as a potential novel disease modifying treatment strategy in asthma.

RECENT FINDINGS

The link between exposure to pathogenic or saprophytic mycobacteria and protection from allergic diseases is still controversial, and recent epidemiological studies, which addressed only exposure to Mycobacterium tuberculosis or bacillus Calmette-Guérin, did not help to clarify this issue. Moreover, the clear efficacy of mycobacterial treatment seen in animal models has not been reproduced in human asthma, and a recent small study testing the hypothesis that heat-killed Mycobacterium vaccae attenuates asthmatic reactions after allergen challenge did not provide convincing results. However, it has been shown that treatment of mice with M. vaccae induces the generation of allergen-specific T regulatory cells capable of suppressing allergen-mediated eosinophilic lung inflammation, suggesting that a general deficiency of T regulatory cell activity might be responsible for the increased prevalence of asthma. This hypothesis is supported by findings that a lack of T regulatory cells, as found in genetic disorders of man and mouse attributable to a mutation of Foxp3, a transcription factor specifically expressed by T regulatory cells, is associated with manifestations of severe atopy and autoimmunity, precisely the spectrum of diseases linked to the hygiene hypothesis.

SUMMARY

Further studies on the relationship between mycobacteria and atopic disorders are needed, but there is reason to believe that the novel findings and molecular mechanisms associated with mycobacterial infections will further strengthen the currently unproved therapeutic value of immunotherapy with mycobacteria.

Immunization and atopy: possible implications of ethnicity

The possible effects of immunization on subsequent development of asthma and atopy remains a matter of controversy. Although some studies have suggested that immunization might increase the risk for atopic disease, a number of studies have found no association or have even reported a protective effect for immunization against atopy. Recent studies have provided evidence that ethnicity might affect the susceptibility to the immunomodulatory effects of vaccination. In this review the association between immunization and atopy and the effect of ethnicity on this association are briefly outlined. The focus will be particularly on BCG vaccination.

Short-term smoke exposure attenuates ovalbumin-induced airway inflammation in allergic mice

Little is known about effects of smoking on airway inflammation in asthma. We tested the hypothesis that smoking enhances established airway inflammation in a mouse model of allergic asthma. C57Bl/6j mice were sensitized to ovalbumin (OVA) and challenged with OVA (OVA-mice) or sham-sensitized to phosphate-buffered saline (PBS) and challenged with PBS aerosols (PBS-mice) for 7 wk. At 4 wk, mice were additionally exposed to air (nonsmoking controls) or mainstream smoke for 3 wk. Using whole body plethysmography, we found OVA-induced bronchoconstriction to be significantly inhibited in smoking OVA-mice as compared with nonsmoking OVA-mice (1 +/- 2% increase versus 22 +/- 6% increase in enhanced pause, respectively). Smoking did not change airway hyperresponsiveness (AHR) to methacholine in PBS-mice, yet significantly attenuated AHR in OVA-mice 24 h after OVA challenge as compared with nonsmoking mice. This was accompanied by reduced eosinophil numbers in lung lavage fluid and tissue of smoking OVA-mice compared with nonsmoking OVA-mice. In contrast to our hypothesis, short-term smoking reduced responsiveness to OVA and methacholine in OVA-mice and decreased airway inflammation when compared with nonsmoking mice. This effect of smoking may be different for long-term smoking, in which remodeling effects of smoking can be expected to interrelate with remodeling changes caused by asthmatic disease.

Therapeutic treatment with heat-killed Mycobacterium vaccae (SRL172) in a mild and severe mouse model for allergic asthma

The hypothesis that a lack of early childhood bacterial infections would favor the development of allergic disease suggests that bacteria can be used as a potential treatment for allergic asthma. Therefore, in this study, we investigated the therapeutic potential of heat-killed Mycobacterium vaccae in two mouse models of allergic asthma. For this purpose, mice were sensitized i.p. with ovalbumin/alum (severe model) or ovalbumin alone (mild model) and challenged on days 77, 80 and 83 by inhalation of either ovalbumin or saline aerosols. Treatment of mice with M. vaccae (s.c. 10(7) or 10(8) colony-forming units) on days 56 and 63, however, did not reduce airway hyperresponsiveness and eosinophilia, IgE and interleukin-5 production 24 h after ovalbumin challenge in either mouse model. We therefore conclude that treatment of sensitized mice with M. vaccae before allergen exposure is not able to reduce the allergic and asthma-like response in a mild and a severe model of allergic asthma.

Inhibition of allergic disorders by infection with bacteria or the exposure to bacterial products

The incidence, severity, and mortality rate of allergic diseases, such as asthma, atopic dermatitis and rhinitis is increasing in the developed nations of the world, despite the use of steroids and other drugs. The reason for this development is unknown, but has been speculated to be due to a steady decline in infectious diseases. This view is supported by recent epidemiological and experimental findings showing that bacterial infections have the capacity to inhibit the development of allergic disorders. In addition, the exposure to bacterial products such as lipopolysaccharide (LPS) or bacterial DNA is also associated with a decrease in allergen-specific Th2 responses. Although the immunological mechanisms responsible for these protective effects are ill defined, recent publications indicate that they are associated with the induction of Th1 or T regulatory responses. This review focuses on experimental and epidemiological studies addressing the question if bacterial infections or the exposure to bacterial products can inhibit the development of allergic responses.