Anti-bacterial IgE in the antibody responses of house dust mite allergic children convalescent from asthma exacerbation

SummaryBackground Atopic sensitization to the house dust mite (HDM) is associated with alteredantibody responses to the nasopharyngeal colonizing bacterium Haemophilus influenzae andchildren admitted to the emergency department for asthma exacerbation have reduced IgGresponses to HDM allergens.Objective To investigate anti-bacterial and anti-allergen antibody responses duringconvalescence from asthma exacerbation and differences found in exacerbations associatedwith and without viral infection.Results IgE antibodies to the P6 bacterial antigen increased in 60% of sera duringconvalescence and for many children achieved titres as high as IgE titres to allergens. Incontrast IgEanti-HDM titres declined during convalescence. The anti-bacterial IgEtitres werethe same in subjects with and without virus infection while the anti-HDM IgE declined morerapidly invirus-infected subjects.IgG titres tothemajorHDM allergens showednoconsistentincrease and the overall IgG anti-HDM titres even declined in subjects without a virusinfection. Anti-bacterial IgG antibodies in contrast to IgE did not change. Patients withfrequent episodic or persistent asthma had similar IgE anti-bacterial titres to patients withinfrequent asthma during the acute phase, although they had reduced IgG titres to both thebacteria and the HDM.Conclusions During the period following an acute exacerbation of asthma there was a markedandspecificincreaseinanti-bacterialIgEcomparedwithareducedIgEresponsetoHDM.Thisprovides further support for the concept of T-helper type 2 responses to bacterial antigensplaying a role in asthma pathogenesis.Keywords asthma, bacteria, IgE, IgG, rhinovirusSubmitted 14 November 2008; revised 22 February 2009; accepted 24 February 2009