About 80 percent of serious infections occur in children under two years. In Mexico, mandatory vaccination has decreased significantly the cases of preventable diseases, such as polio, measles and smallpox. However, Haemophilus influenzae continues to be a pathogen causing infections at pediatric ages, such as otitis, sinusitis, conjunctivitis, bronchitis and meningitis.
Despite the existence of a vaccine against it, the antigen only protects against serotype b. This is why Alejandro Carabarin Lima, a research professor at the Institute of Sciences (ICUAP) of the Meritorious Autonomous University of Puebla (BUAP) ventured into the development of a vaccine to protect the infants of this organism, both from capsulated and non-capsulated strains, found in the respiratory tract of humans.
Since 1931, six capsular serotypes have been known: a, b, c, d, e and f. The capsule prevents recognition of the bacteria by the immune system, so this type generates the greatest virulence, causing systemic diseases, such as the presence of bacteria in the blood and septicemia (complication of an infection). In addition, there are non-capsulated serotypes that cause localized diseases; however, in recent years it has been shown that non-capsulated H. influenzae also produces systemic infections.
To understand how this non-capsulated pathogen evades the immune response to reach the bloodstream, Carabarin Lima proposed that this bacillus could be using a protein called enolase, to adhere, invade and spread in the body.
“Looking at the response that enolase has in Trypanosoma cruzi (parasite that triggers Chagas disease), we look for whether this same enzyme would have a similar participation in the pathogenesis of H. influenzae.”
For three years and in collaboration with Dr. Rosa del Carmen Rocha Gracia, from the Research Center in Microbiological Sciences of ICUAP, Carabarin Lima investigates the development of an effective vaccine against non-capsulated and uncapsulated serotypes of Haemophilus influenzae .
From the bacterium’s DNA, the gene encoding the enolase protein was cloned, expressed, purified and tests were performed to observe its probable immune response. “In silico tests (by computer) showed that this protein has regions that could be recognized by the immune system (T and B lymphocytes), called epitopes, to generate a humoral and cellular response.”
This same result is being tested experimentally in animal models (murine). The next step will be to test the effectiveness of the vaccine against the different serotypes.
The development of an antigen implies a strong economic investment, since molecular biology and immunology are worked on in animal models. Also, obtaining results is a slow process that depends on the behavior of the specimens.
“We are in the initial phase of the investigation. We have to fully characterize the immune response and validate the cell populations that are generated, as well as the induced cytokines (proteins that regulate the function of the cells that produce them over other cell types). The foregoing will lead to knowing the immunological protection mechanism generated by the vaccine,” said Alejandro Carabarin Lima.