Role of Chlamydia pneumoniae as an Inducer of Asthma

Chlamydia pneumoniae (Cpn) could have three distinguishable causal effects as an asthma inducer. First, an acute infection (or reactivation of a latent infection) could cause an acute worsening of preexisting asthma. Indeed, it is generally accepted that acute Cpn infection can cause some acute asthma exacnhations('~*) but most evidence suggests that other organisms [mainly respiratory viruses, and, to a lesser extent, Mycoplasma pneumoniue ( M P ~ ( ~ ) ) ] are associated with the majority of asthma exacerbations in both children(" and adults.(" Second, because of its propensity to produce persistent infection, Cpn chronic lung infection could cause worsening of established asthma over time. Again, Cpn has been associated with asthma severity(') and a possible promoting role for Cpn in asthma is a focus of active investigation.(') Third, an acute primary or secondary Cpn infection, in a previously asymptomatic nonasthmatic individual, could cause acute wheezing that develops into chronic asthma. That Cpn can initiate asthma is a radical idea for which there is some evidence(*) but how important a role Cpn plays as an asthma initiator remains to be determined. It is conceivable that acute Cpn infection, as an asthma initiator, could contribute to a substantial number of cases. This chapter focuses on the substantial body of evidence favoring a promoting role for Cpn, and also reviews the existing evidence for Cpn as an asthma initiator.