Proteome snags grant for TB test

Sydney's Proteome Systems has won a US$2 million federal government R&D Start grant to advance development of its new rapid diagnostic for tuberculosis.

Proteome Systems' TB test will be developed as an easily administered, point-of-care (POC) system, and will deliver an accurate result within hours, according to Proteome's head of discovery and diagnostics, Dr Jenny Harry.

Harry said that a prototype test could be ready before the end of 2005. Unlike rival TB diagnostics, the new test will directly detect proteins expressed by the TB microbe Mycobacterium tuberculosis in infected individuals, as well as measuring the severity of an infection.

TB is the most prevalent infection in the world today - a third of the world's population is infected, and 2 million people die of TB every year.

The HIV epidemic has led to the re-emergence of TB as a major public health problem. Immunodeficient AIDS patients are particularly vulnerable to infection, and intensive antibiotic therapy has selected for multi-drug resistant strains. It has been estimated that some 40 per cent of AIDS patients die of TB.

Harry said current tests - including the new QuantiFERON-TB GOLD test developed by Melbourne diagnostics company Cellestis (ASX-CST) - do not test directly for the presence of proteins expressed by the TB microbe in vivo.

Cellestis' QuantiFERON-TB GOLD test, approved by the US Food and Drug Administration in December, measures levels of interferon gamma, secreted by T-cells as the patient's immune system responds to the TB microbe.

Other tests look for TB antibodies in the patient's blood, a method Harry said is also subject to error because it is based on antibodies to proteins expressed by the TB microbe in the artificial environment of cell culture, rather than in vivo.

Using the company's technology, Proteome researchers has identified 19 disease-specific proteins expressed in vivo - more than half of which are not expressed in the artificial medium of cell culture.

The company's researchers have shown that several of these proteins elicit antibody responses, even in severely immunocompromised AIDS patients. Tests that measure gamma interferon levels in these patients as a proxy for TB infection may be unreliable because of their low T-cell counts.

The ability to quantify the severity of infection by measuring antibody levels to these expressed antigens meant doctors could also track the course of a TB infection, and the patient's response to drug therapy.