Influence of immunisation with Mycobacterium bovisbacillus Calmette-Guérin on the sensitisation to inhaled allergens after infection with respiratory syncytial virus

Abstract

Respiratory syncytial virus (RSV) may play an important role in allergic diathesis by creating a Th2-type immune response. Mycobacterium bovis bacillus Calmette-Guérin (BCG) is known to induce a Th1-type immune response, but the association of BCG vaccination and the suppression of allergy development remain controversial. We investigated the influence of BCG vaccination on the immune response to RSV in a mouse model. Balb/c mice were BCG vaccinated, RSV infected and ovalbumin (OVA) challenged. Mice were sacrificed one, two and four weeks after allergen exposure. Bronchoalveolar lavage was performed. Alveolar macrophages and lymphocytes from spleens and lung-associated lymph nodes were investigated for cytokine production and cell proliferation. Serum was tested for allergen-specific immunoglobulin-E (IgE). Lung eosinophilia was diminished by BCG immunisation. OVA-specific serum IgE was increased regardless of prior BCG vaccination. Interleukin-4 secretion of spleen lymphocytes increased in BCG-vaccinated mice only one week after allergen exposure but was comparable to non-vaccinated mice at four weeks. The reactivity of spleen lymphocytes towards concanavalin-A to secrete interferon-gamma was increased in the vaccinated group at the end of the observation period. Interleukin-6 and tumour necrosis factor-alpha secretion of alveolar macrophages as well as proliferation of stimulated thoracic lymph node cells were increased and prolonged in vaccinated mice. BCG immunisation led to a local suppression of the allergic reaction within the lung. No reduction of systemic IgE production was observed. Further studies are necessary to determine a possible time dependence of BCG immunisation.

Protective T cell immunity against respiratory syncytial virus is efficiently induced by recombinant BCG

“…2). This finding is consistent with previous studies showing that BCG immunization can promote IFN-␥ secretion by T cells after unspecific stimulation, and reduce allergic responses to inhaled antigens (51,52). In addition, it has been demonstrated that immunization of newborns with BCG induces a strong Th1 immune response, despite the fact that newborns are prone to Th2 responses upon antigenic challenge (23,53).…”