Whooping cough: scientists describe the bacteria’s mechanisms to survive
CONICET researchers found how this microorganism manages to evade the immune system and remain in the body
María Eugenia Rodríguez and her research team. Photo: courtesy researcher.

Whooping cough, caused by Bordetella pertussis, is one important cause of child morbidiy and mortality. According to the World Health Organization (WHO), it is estimated that there are around 50 million cases annually and 300 deaths.

CONICET scientists at the Research and Development Centre for Industrial Fermentations (CINDEFI, CONICET, UNLP) published a study in which the researchers prove how this microorganism evades the immune system. It was published in Pathogens and Disease magazine.

In 2010 this reserch team had demonstrated that Bordetella pertussis survives within the human macrophages, one of the cell types that belong to the immune system in charge of combating it. The study describes the mechanisms Bordetella pertussis uses to inhabit and replicate inside the macrophages, indicating that these cells could act as a niche for their persistence.

“We found that when there are not opsonic antibodies [that is to say those that ‘mark’ the pathogen for its destruction], this bacteria enters the macrophage and remains in some vesicles, the early endosome, where it can spread, infect the macrophage and create a ‘niche of persistence’, María Eugenia Rodríguez, CONICET principal researcher at the CINDEFI and one of the authors of the research, explains.

That happens through two bacterial toxins, Ptx CyaA, which modulate the response of the macrophages’ genes to avoid their action and survive inside. “Through these two toxins it inhibits all that should kill it, all the inflammatory response and the microbicide reaction” Rodriguez adds.

This find allows scientists to understand how these bacterium persist in adult populations without causing any symptoms. “The bacteria remain in a dormant state within these macrophages and the other cells of the immune system do not ‘consider’ it as infected because Bordetella pertussis regulates all mechanisms that make it detectable. This is called an asymptomatic carrier and explains and allows us to understand why this bacteria has persisted for decades in vaccinated populations and in adults who do not cough”, Rodriguez concludes.

Whooping cough in Argentina:
According to information from the Health Ministry of Argentina, in 2011 there were 1,594 cases and 70 deaths under one year. From the cases that were confirmed, 91% belong to 4 months old infants. In 2012, a number of 568 cases of whooping cough with Bordetella pertussis were confirmed. Currently, the only way to prevent it is through vaccination. The Argentine Immunization Schedule includes four vaccines to provide immunity against whooping cough: pentavalent, which should be given at 2, 4 and 6 months old infants; quadruple at 18 months; triple cell bacterial at school entry; and triple acellular bacterial, which should be given to kids at 11 years old and health personnel who works with children under a year, and those who live with premature babies who weigh less than 1.5 kg. In the cases of babies under six months, pregnant women are vaccinated from the 20th week of gestation.