As part of the Meet the Expert series, Isabel Vincent and JC Le Bayon set up a malaria diagnostics lab in the foyer of Glasgow Science Centre on Sunday April the 17th. People visiting the Science Centre were asked to help diagnose a suspected case of malaria in a fictional young boy in a Cambodian hospital.
Malaria is a deadly parasitic disease transmitted by mosquitoes and is common throughout the tropics. The parasites live inside red blood cells and can cause anaemia and brain damage. There is a lot of malaria drug resistance in Cambodia and doctors were worried that the boy had malaria and that it might be resistant to the two drugs that they had in the pharmacy – artemisinin and methotrexate.
Questions
- Does the boy have malaria?
- If yes, is his malaria going to respond to methotrexate or artemisinin, or both or neither?
If we take a sample of the boy’s blood, we can separate malaria-infected red blood cells from the other cells in his blood using a fluorescence activated cell sorter (FACS) machine. To demonstrate how a FACS machine works, JC used a drain pipe with different sized holes in it to sort cherry tomatoes (red blood cells) from limes (lymphocytes).
The “malaria-infected” tomatoes were sorted into the first bucket using a laser (torch) to detect DNA from the parasites inside the cells, while “non-infected” tomatoes and limes were sorted into a second bucket. A real FACS machine is able to measure the size and complexity of cells using a laser and creates different charges on the cells to sort them into different tubes. In a real FACS machine we would use different florescent probes to detect infected red blood cells, such as glycophorin A – for all RBCs – and SYBR-Green for malaria infected erythrocytes.
The volunteer diagnosticians were asked to throw the fruit down out fruit sorting machine and then check the buckets to see if any malaria infected cells were detected.
Once we had concentrated our malaria infected cells we wanted to see whether the parasites would be killed by our drugs. Measuring the levels of different molecules within the cells using a mass spectrometer can tell us whether the parasites have developed drug resistance. Isabel used her time of flight mass spectrometer to detect these molecules in the infected cells.
Molecules (blue balls) travel along the tube in the mass spectrometer with the distance they travel related to the molecular weight of the molecule. Depending on where the molecules (balls) stopped, we could say whether the parasites had high levels of dUMP (indicative of resistance to methotrexate), dTMP (no resistance detected) or PIP3 (resistance to artemisinin).
Detecting drug resistance molecules in our makeshift mass spectrometer
In a real mass spec, millions of chemical signals are detected and interpreted to give a view of the internal metabolism of the parasite in a technique known as “metabolomics”.
Many of our diagnosticians found that the boy had malaria that was resistant to one of the drugs, but not the other so a treatment plan could be formulated and the boy was cured! In real life, things aren’t so simple and drug resistance is a problem for many diseases around the world and particularly in South East Asia.
