Immunosurveillance and immunodiagnostic

Unit responsible: 

Detecting and monitoring infectious diseases using the immune response

We help the federal government to develop vaccination strategies to prevent and tackle infectious diseases. We work alongside the Epidemiology of Infectious Diseases and Viral diseases services, to investigate the extent to which the Belgian population is (still) protected against vaccine-preventable diseases (serosurveillance). We do this using seroprevalence studies, in which the blood of a representative sample of the population is examined for the presence of antibodies against the vaccine-preventable diseases such as whooping cough, diphtheria and tetanus (this is called the immune status). These studies mirror the impact of vaccination within the Belgian population. The number of people who have been exposed to these vaccine-preventable diseases (disease burden) is mapped by the National Reference Centers (NRC). The combination of seroprevalence and disease burden shows how vaccination has influenced the presence of diseases in the population.

Within the NRC for toxigenic Corynebacteria we are responsible for determining the immune status against diphtheria. Within the NRC for Bordetella pertussis we specialize in the serodiagnosis of whooping cough, extremely valuable for (young) adults in whom the disease is often mild or asymptomatic. Because whooping cough is highly contagious, these (young) adults are often a source of infection for infants and young children, the most vulnerable group where the disease can range from very serious to fatal. Besides providing a diagnosis, serodiagnosis is mainly used to monitor suspected outbreaks and to estimate the presence of whooping cough in Belgium. Our scientific research focuses mainly on the human immune response that is triggered following infection or vaccination (immune monitoring).

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The diagnosis of a whooping cough infection is not always easy because the bacterium that causes it is difficult to detect and then only for a short space of time. By determining the presence or absence of antibodies, a diagnosis is still possible at a point when the pathogenic bacterium itself can no longer be detected (serodiagnosis).  If whooping cough is suspected, antibodies directed against the pertussis toxin (anti-PT IgG) are determined. Shortly after an acute infection, these are strongly present and can be quantified. However, because the same antibodies are also generated after vaccination, a correct interpretation (diagnosis) is often difficult in patients who were recently vaccinated. In this case, anti-PT IgA antibodies are sometimes determined that are present after an infection, but are rarely generated after vaccination.

In collaboration with various partners, we mainly map the human immune response that occurs after vaccination with DTPa vaccines (diphtheria-tetanus-acellular pertussis). This involves independent clinical studies in which protection after vaccination is evaluated in certain populations (whether immune deficient or not). To detect vaccine-induced antibodies we use the ELISA or (more advanced) multiplex technology. As a center of expertise for whooping cough, our task consists of gaining an understanding of the correlates of immunological protection against whooping cough. In this context we unravel the various humoral and cellular immune responses that occur after a natural whooping cough infection or reinfection. To do so we invest in the development of innovative in vitro humoral and cellular assays.

Continuous surveillance of the disease burden, vaccination coverage and seroprevalence remains necessary to support the vaccination policy and optimize the vaccination schedule. Within our national seroprevalence studies we determine the immune status against pertussis, diphtheria and tetanus. The quantity and frequency of antibodies present in a cross-section of the Belgian population reflects the protection against these vaccine-preventable diseases. To make these determinations we use a multiplex technology with which various parameters can be determined simultaneously. For whooping cough, we also participate in European seroprevalence studies.

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