CDC Scientist Describes Multiplex Testing for Malaria at Immunology2022™
Antigen and antibody tests generate important data for characterizing population-level trends, individual immune response, and more
At Immunology2022™, this year’s meeting of the American Association of Immunologists, Eric Rogier, a microbiologist from the CDC, offered an exciting presentation about utilizing bead-based multiplex assays for generating epidemiological and immunological data about malaria.
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Dr. Rogier, a specialist in malaria and other tropical diseases, aims to develop reliable diagnostic and serological tests to aid public health experts in their understanding of outbreaks, disease trends, and immune response. Unlike many tropical diseases that are easy to identify, malaria causes non-specific symptoms (such as fever, chills, headache, and nausea) that can be difficult to diagnose. In addition, asymptomatic infections are common in areas with high rates of transmission. This makes it difficult to estimate the true burden of disease, he noted.
Searching for several antigens at once with xMAP® Technology
Obtaining an accurate case count would allow researchers to track the effectiveness of treatments, monitor progress over time, and perhaps ultimately achieve disease elimination, Rogier informed. Thus, researchers require epidemiological data that is both accurate and plentiful. Unfortunately, the data generated by local health facilities is not always reliable or accessible.
To address these challenges, Rogier and his colleagues have developed multiple tests based on
His team has created several xMAP assays for malaria, with varying numbers of analytes. They have used a 9-plex assay to capture antigens of interest, including a Nigerian household survey that tested samples collected from more than 31,000 children. A separate study in Djibouti averaged 1,000 people and even allowed scientists to identify malaria co-infections of P. falciparum and P. vivax, thereby highlighting xMAP Technology’s cost advantage. Rather than spending $10 per sample on PCR tests for each person, the team spent $2 per sample and the xMAP assay yielded the same data, with results more comprehensive than any single-target test. Eric Rogier, PhD MPH, a microbiologist at the CDC, and his team have created several xMAP assays for malaria, with varying numbers of analytes.“Antibodies don’t lie”
In addition, Rogier has developed serological assays for antibody detection. “You’re looking at a history of exposure for an individual versus an active infection,” he said. This approach provides “an objective measure of malaria exposure in [a] population,” he added. “Antibodies don’t lie.”
Serology testing is especially useful in low-transmission settings, where generating enough data for epidemiological use can be challenging. In one example, Rogier showed that the antibody test identified 50 times more positive samples than tests for active infections. In another, he noted that serology data “can be a very powerful metric to assess population-level exposure.” Thanks to multiplexing, the tests can measure IgM, IgA, IgE, and all four subclasses of IgG.
Generating data for malaria—multiplexing makes it possible
Furthermore, a longitudinal study conducted in Angola offered scientists a view of the immune response to malaria, wherein patients were followed for 42 days with weekly sampling and serological testing. This study involved a 37-plex xMAP assay and led to new insights into antibody half-life and other dynamics. Interestingly, the results also made it possible to distinguish between patients who had malaria for the first time and those who had been infected more than once.
Together, these studies demonstrate that xMAP-based assays can cost-effectively generate rich epidemiological data for malaria in a variety of settings.
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