CONICET | Buscador de Institutos y Recursos Humanos

Waning of immunityinduced by vaccines and pathogen adaptation to escape vaccine-induced immunity arethe main causes proposed to explain pertussis resurgence. Regarding pathogen evolutionit was reported that circulating Bordetellapertussis isolates differ in their genotypes from the strains used invaccines production. Polymorphism in genes coding for proteins included in vaccineswere described in different countries that use different type ofpertussis-vaccine, however only in countries where acellular vaccines (aP) areused, high prevalence of pertactin-(vaccine antigen)-deficient strains wasdescribed. This suggests that aP vaccines exert a strong selection pressure onthe circulating bacterial population allowing the prevalence of strainsdeficient in the expression of vaccine antigen. To corroborate this hypothesis,systematic studies carried out in countries that use pertussis whole cellvaccine (wP) are needed. Under this context, here we present data on pertussisepidemiology and molecular characterization of B. pertussis isolates obtained during 2000-2017 period in BuenosAires, the most populated province of Argentina-a country with whole-cell pertussisprimary vaccination.The data presented show that during the studied period there was a sustainedincrease in the number of pertussis cases since 2002 with outbreaks every 4years, being the one occurred in 2011 the greatest. The majority of cases weredetected in infants under 1 year unvaccinated or with incomplete vaccinationschedule because of the age. Using the MLST technique, we detected that the circulatingisolates, mostly have ptxP3-ptxA1-prn2-fim3-2 genotype (327/360,91%). Seven percent (25/360) have ptxP3-ptxA1-prn2-fim3-1 genotype, and2% (8/360) ptxP1, ptxAno1-prn1-fim3-1. Of the totalnumber of isolates analyzed, only 2 were found to be deficient in pertactin expressionas consequence of an IS481 insertion in prncoding sequence. The observed low prevalence of pertactin deficient strain inBuenos Aires support that the loss of its expression might be aP vaccine-driven.

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