30/07/07

African researchers test new TB vaccine

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Clinical trials of a new tuberculosis vaccine have begun in the Gambia and South Africa, announced UK funding body the Wellcome Trust last week (28 July).


The vaccine — known as MVA85A and developed by researchers at the UK-based University of Oxford — could provide another line of defence against tuberculosis (TB).


The current vaccine, Bacille Calmette-Guerin (BCG), protects against severe forms of tuberculosis, but the effect “appears to wane in adolescence”, said Martin Ota, from the Gambia’s Medical Research Council Laboratories and principal investigator for the trials in the Gambia.


BCG is also not safe to use in people with AIDS, and may not be safe to use in HIV positive people, according to Tony Hawkridge, senior clinical researcher at the South African Tuberculosis Vaccine Initiative at the University of Cape Town. This is because it is a live vaccine that can cause disease in people with weak immune systems.


The new MVA85A vaccine is used alongside BCG and uses a protein from the bacteria that causes TB — Mycobacterium tuberculosis — to activate immune cells called T cells, and boost the body’s immune response to BCG.


“Data from HIV negative adults and adolescents [in South Africa] showed that the vaccine is safe and generates very strong immune responses,” Helen McShane, a Wellcome Trust senior clinical research fellow, told SciDev.Net. McShane developed the vaccine.


A phase II clinical trial began last week on infants in the Gambia, says Ota.


The researchers will study data from 471 HIV-negative four-month-old babies to determine the level of immune response it triggers at particular dosing levels and how it interacts with other vaccinations, such as those for diphtheria, pertussis (whooping cough), tetanus and Haemophilus influenzae type b (Hib), which causes pneumonia and meningitis.  


South African researchers are also conducting trials with HIV positive adults, as one third of the world’s HIV positive population also has TB. “The two diseases are somewhat synergistic,” says Jerald Sadoff, chief executive officer of the Aeras Global TB Vaccine Foundation. “Both are diseases of poverty; TB makes HIV worse, HIV makes TB worse.”


“If we want to eliminate the disease, we need a new vaccine,” says Sadoff. With better diagnostics and antibiotics, he says, “estimates are that a million to a million and a half lives a year could be saved. You have to use all the new tools.”

TB kills over one and a half million people a year, and 98 per cent of them are from the developing world.

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