Malaria diagnostic kit testing is essential to ensure that this life-saving tool is working as intended with accuracy during critical times. However, it is not a simple process. This article will explore how researchers test malaria diagnostic kits using the pLDH recombinant protein.
Understanding the pLDH Protein
Before understanding how researchers test the diagnostic malaria kits, it’s very important to understand the pLDH protein and its recombinant antibody.
You see, the pLDH, or Plasmodium Lactate Dehydrogenase, protein is a substance that is present only in the body during an active malaria infection.
This is because, when a person becomes infected with malaria, the pLDH protein begins to circulate in their bloodstream, which is transferred by the Plasmodium parasite, which is carried by mosquitoes.
NOTE: The pLDH levels in the blood correspond closely to the number of live parasites in the body.
However, accurately pinpointing the location of the pLDH protein isn’t as simple as placing a blood sample under a microscope. Instead, researchers rely on the biomarkers (more on that below), specifically the pLDH recombinant protein. This difference is what makes it an ideal biomarker.
What is a Recombinant Protein?
Despite the importance of pLDH, researchers cannot always rely on blood samples from infected patients to test their new diagnostic kits. Patient samples can be inconsistent, difficult to transport, and safety-sensitive. This is exactly why a pLDH recombinant protein is needed.
To put it simply, a recombinant protein is a laboratory-made version of a natural protein. Scientists take the genetic "code" for the malaria pLDH and insert it into a host, such as E. coli bacteria. These bacteria then act as a factory, producing large amounts of the pure malaria protein.
By using a recombinant version from a supplier like AAAbio, researchers get a "clean" and highly concentrated sample of the protein. This allows them to know exactly how much protein is in their test tube, which is vital for calibrating a diagnostic kit's sensitivity.
How are Diagnostic Kits Validated?
The process of testing a malaria kit involves several stages of validation. Researchers need to know two main things: Does the test see the malaria protein when it is there (sensitivity)? And does the test stay "negative" when the protein is absent (specificity)?
The Role of Lateral Flow (LF) Testing
The most common type of malaria test is the Lateral Flow Assay, which looks very similar to a standard pregnancy test. It is a small plastic cassette with a strip of paper inside. When a drop of blood is placed on the strip, it travels across several "zones" containing antibodies.
To test these strips during development, researchers "spike" healthy blood with the pLDH recombinant protein. If the strip is working correctly, the antibodies on the paper will grab the recombinant protein and produce a visible colored line. By using different concentrations of the protein, scientists can determine the "limit of detection"—which is the smallest amount of malaria the test can successfully find.
Using ELISA for High-Precision Testing
While the rapid strip tests are great for the field, researchers also use a method called ELISA (Enzyme-Linked Immunosorbent Assay) in the lab. This technique is much more sensitive and is used to provide a mathematical value for how much pLDH is present.
In an ELISA test, the pLDH recombinant protein is placed into small wells on a plastic plate. Researchers then add different antibodies to see which ones stick the best. This helps them choose the highest quality components to put into the mass-produced rapid tests that will eventually be sent to hospitals.
Detecting Different Malaria Species
Since there are several types of malaria parasites, researchers need to ensure that specialized diagnostic kits are designed to find all types, while others are specific to just one.
Researchers use different versions of recombinant proteins to ensure their kits can tell the difference. For instance, by testing a kit against pLDH from P. falciparum and then against pLDH from P. vivax, they can prove that the kit is "species-specific."
