Specific IgE to respiratory allergens and IgG antibodies to Toxoplasma gondii and Streptococcus pneumoniae in Norwegian military recruits.

Declining exposure to infections has been implicated as a cause for the rising trend of allergy. Gastrointestinal infections, in particular, have been suggested to have a protective effect against allergy development. In contrast, there are only limited data available regarding the effect of respiratory tract infections with encapsulated bacteria on allergy development. We investigated the association between IgG antibodies against the gastrointestinal parasite Toxoplasma gondii and the bacterium Streptococcus pneumoniae and specific IgE to common allergens in Norwegian military recruits. IgG antibodies to T. gondii and to a 23-valent pneumococcal polysaccharide vaccine (Pneumovax) were determined by ELISA. Specific IgE to common airborne allergens was determined by Phadiatop. Individuals with Phadiatop values from class 0-2 were classified as non-atopic (n = 419), while those with class 3-6 were classified as atopic (n = 201). No significant difference was observed in IgG antibody levels to pneumococcal polysaccharides between atopic and non-atopic recruits, whereas seropositivity to T. gondii was found to be less frequent among the atopic recruits (odds ratio, 0.37; 95% CI, 0.17-0.81; P = 0.01). Hence, in Norwegian recruits, the serological response to a gastrointestinal pathogen, but not to the respiratory encapsulated bacteria, was found to be associated with a lower probability for being sensitized according to the criteria used. The present study conforms to the hypothesis that reduced rates of infection with certain microorganisms may be associated with an increased risk of allergic sensitization.