McGill researchers report breakthrough in rapid malaria detection

Optical laser technique could eliminate the need for slides, staining and microscopes

A research team led by Dr. Paul Wiseman of the Departments of Physics and Chemistry at McGill University has developed a radically new technique that uses lasers and non-linear optical effects to detect malaria infection in human blood, according to a study published in the Biophysical Journal. The researchers say the new technique holds the promise of simpler, faster and far less labour-intensive detection of the malaria parasite in blood samples.

Malaria is a vector-borne infectious disease spread by parasites of the genus Plasmodium. Most common in tropical and subtropical regions, it is a global scourge with 350 to 500 million new cases – and one to three million fatalities – reported annually. Most of the fatalities are concentrated in sub-Saharan Africa, where the resources and trained personnel currently required to accurately diagnose the disease are spread the thinnest.

Current detection techniques require trained technicians to stain slides, look for the parasite’s DNA signature under the microscope, and then manually count all the visible infected cells, a labourious process dependent on the skill and availability of trained analysts. By contrast, the proposed new technique relies on a known optical effect called third harmonic generation (THG), which causes hemozoin – a crystalline substance secreted by the parasite – to glow blue when irradiated by an infrared laser.

“People who are familiar with music know about acoustic harmonics,” said Dr. Wiseman. “You have a fundamental sound frequency and then multiples of that frequency. Non-linear optical effects are similar: if you shine an intense laser beam of a specific frequency on certain types of materials, you generate multiples of the frequency. Hemozoin has a huge, non-linear optical response for the third harmonic, which causes the blue glow.”

Dr. Wiseman and his colleagues now hope to adapt well-established existing technologies like fibre-optic communications lasers and fluorescent cell sorters to quickly move the technique out of the laboratory and into the field.

“We’re imagining a self-contained unit that could be used in clinics in endemic countries,” said Dr. Wiseman. “The operator could inject the cell sample directly into the device, and then it would come up with a count of the total number of existing infected cells without manual intervention.”

LUNG CANCER

Preventing lung scarring may extend lives of lung cancer patients

Researchers have found that using a special type of drug called a pharmaceutical monoclonal antibody to block the integrin beta6-TGF-beta pathway prevents a serious side effect of radiation therapy for lung cancer patients – pulmonary fibrosis (scarring of the lungs), thereby extending patients’ lives and improving their quality of life, according to a study presented at the Plenary I session on October 29, 2007, at the American Society for Therapeutic Radiology and Oncology’s 49th Annual Meeting in Los Angeles.

“The toxicity of pulmonary fibrosis limits the amount of the radiation dose that can be safely given to patients,” said Simon Cheng, M.D., Ph.D., an author of the study and a radiation oncologist at New York University Medical Center in New York. “These study results may lead to more effective radiation therapies for advanced lung cancer, which is the leading cause of cancer deaths in the U.S.”
More than 50 percent of patients receiving radiation therapy for advanced lung cancer develop radiation-induced lung fibrosis, a painful side effect that can affect patients’ quality of life and, in some cases, can be fatal. Pulmonary (lung) fibrosis involves inflammation and scarring of the lungs causing patients to feel short of breath, have a chronic dry cough, feel fatigue and pain in the chest, and suffer loss of appetite and weight loss. Over time, fibrosis causes the air sacs of the lungs to be replaced by scar tissue, causing difficulty breathing and an irreversible loss of the tissue’s ability to transfer oxygen into the bloodstream.

This study involved mice treated with a 14 Gy single dose of radiation to the lungs. Researchers wanted to determine if using an antibody to block integrin beta6 (a specific activator of the transforming growth factor (TGF-beta) signaling pathway), could prevent the onset of radiation-induced pulmonary fibrosis. The study shows that mice that were given integrin beta6 monoclonal antibodies did not develop radiation-induced lung fibrosis, while the control group of mice developed the lung condition.

“Fibrosis is a very serious side effect that often keeps doctors from giving patients a full dose of radiation for fear that the serious problems caused by fibrosis will outweigh the good done by the radiation. If further studies conclude that this drug can indeed prevent fibrosis in lung cancer patients, I believe researchers are a huge step closer to curing this disease,” said Dr. Cheng.