Intranasal sensitization of Japanese cedar pollen by the co-administration of low doses of cholera toxin but not its recombinant B subunit to mice

Aerofloral studies and allergenicity of dominant pollen types in Taraba and Bauchi States of Northeastern Nigeria

Pollen and spores have been identified as major airborne bio-particles inducing respiratory disorders including allergic rhinitis and atopic dermatitis among hypersensitive individuals. The present study was conducted with a view to investigating monthly depositional rate of atmospheric palynomorphs to determine the influence of the immediate vegetation on airborne pollen distribution; allergenic activities of dominant atmospheric pollen types at selected study locations in Taraba and Bauchi States, Northeastern Nigeria. Bioaerosols were collected using Tauber-like pollen traps and subjected to standard palynological treatment procedures, microscopy and photomicrography. Plant enumeration within the surrounding vegetation revealed that some airborne pollen types were produced by local plants at the study locations. Spores of Nephrolepis sp., Pteris sp. and a trilete fern, as well as diatoms were also recovered. Crude protein contents of some dominant pollen types; Borreria verticillata (L.) G.F.W. Meyer and Panicum maximum Jacq. for Taraba State; Leucaena leucocephala (Lam.) de Wit. and Terminalia catappa L. for Bauchi State, were quantified and extracted to sensitize Mus musculus mice for serology (ELISA) and haematology (differential and total white blood cell counts). Statistical significance was tested and recorded in the correlation between levels of serological and haematological parameters elicited by each test group; differences between levels of these parameters elicited by each test group and those of the control, as well as at varying sensitization periods. In the Leucaena leucocephala test group, swollen body and histopathological morbid features showing more extensive areas of inflammatory cells and alveoli filled with fluid in the lungs, were recorded in two dead M. musculus, respectively. The study revealed that all the tested pollen types are possible allergens at the study locations, establishing a complexity of interaction among allergy mediators at varied periods of mice sensitization and forming a paradigm of human immune response to the different pollen allergens.

Intranasal sensitization with Blomia Tropicalis antigens induces allergic responses in mice characterized by elevated antigen-specific and non-specific serum ige and peripheral blood eosinophil counts

In order to evaluate the potential allergenicity of Blomia tropicalis (Bt) antigen, IgE production of both specific and non-specific for Bt antigen was monitored in BALB/c mice after exposure to the antigen by nasal route. It was evidenced that B. tropicalis contains a functional allergen in its components. The allergenic components, however, when administered intranasally without any adjuvant, did not function to induce IgE response within a short period. On the other hand, intranasal inoculation of Bt antigens augmented serum IgE responses in mice pretreated by a subcutaneous priming injection of the same antigens. Inoculation of Bt antigen without subcutaneous priming injections induced IgE antibody production only when the antigen was continuously administered for a long period of over 24 weeks. Even when the priming injection was absent, the Bt antigen inoculated with cholera toxin (CT) as a mucosal adjuvant also significantly augmented the Bt antigen-specific IgE responses depending on the dose of CT co-administered. The present study also demonstrated that Bt antigen/CT-inoculated mice showed increased non-specific serum IgE level and peripheral blood eosinophil rates without noticeable elevations of the total leukocyte counts. The immunoblot analysis demonstrated 5 main antigenic components reactive to IgE antibodies induced. These components at about 44-64 kDa position were considered to be an important candidate antigen for diagnosis of the mite-related allergy.

Chimeras of labile toxin one and cholera toxin retain mucosal adjuvanticity and direct Th cell subsets via their B subunit

Native cholera toxin (nCT) and the heat-labile toxin 1 (nLT) of enterotoxigenic Escherichia coli are AB5-type enterotoxins. Both nCT and nLT are effective adjuvants that promote mucosal and systemic immunity to protein Ags given by either oral or nasal routes. Previous studies have shown that nCT as mucosal adjuvant requires IL-4 and induces CD4-positive (CD4+) Th2-type responses, while nLT up-regulates Th1 cell production of IFN-gamma and IL-4-independent Th2-type responses. To address the relative importance of the A or B subunits in CD4+ Th cell subset responses, chimeras of CT-A/LT-B and LT-A/CT-B were constructed. Mice nasally immunized with CT-A/LT-B or LT-A/CT-B and the weak immunogen OVA developed OVA-specific, plasma IgG Abs titers similar to those induced by either nCT or nLT. Both CT-A/LT-B and LT-A/CT-B promoted secretory IgA anti-OVA Ab, which established their retention of mucosal adjuvant activity. The CT-A/LT-B chimera, like nLT, induced OVA-specific mucosal and peripheral CD4+ T cells secreting IFN-gamma and IL-4-independent Th2-type responses, with plasma IgG2a anti-OVA Abs. Further, LT-A/CT-B, like nCT, promoted plasma IgG1 more than IgG2a and IgE Abs with OVA-specific CD4+ Th2 cells secreting high levels of IL-4, but not IFN-gamma. The LT-A/CT-B chimera and nCT, but not the CT-A/LT-B chimera or nLT, suppressed IL-12R expression and IFN-gamma production by activated T cells. Our results show that the B subunits of enterotoxin adjuvants regulate IL-12R expression and subsequent Th cell subset responses.