Therapy Analysis - Malaria
Malaria - hope for the future
The holy grail in the prevention of malaria is of course the development of a prophylactic vaccine, however, with not one marketed vaccine against any human parasitic illness currently existing, this appears to be a challenge. The complexity of the parasitic genome compared to simpler organisms such as bacteria and viruses, combined with Plasmodium parasite's ability to 'dodge' the immune system has made the development of an effective vaccine strategy extremely complicated.Currently the vaccine closest to launch is Mosquirix, under development by GlaxoSmithKilne Biologicals in collaboration with the US army. Mosquirix is a recombinant vaccine based on the P. falciparum circumsporozoite protein fused to the hepatitis-B surface antigen, and is aimed at preventing the Plasmodium from entering and developing within the liver. In a recent trial involving 2,000 children in Mozambique, it was able to provide protection from malarial infection in approximately 50% of patients, over an 18 month period. This represents a major achievement in the field of malaria vaccine development.
There is unfortunately no 'silver bullet' which will lead to the eradication of malaria.In partnership with a number of leading African research institutions, new studies are now underway in Gabon, Ghana, Kenya, Mozambique and Tanzania to determine the best formulation and dose for a large-scale Phase III trial and other Phase III studies. If Phase III trials are successful, GSK hopes that the candidate vaccine could be submitted for regulatory approval by 2011.
A different approach to vaccine development is being undertaken by Sanaria, a company solely devoted to the development of a malaria vaccine. Sanaria's vaccine is based on research conducted in the 1960s by Ruth Nussenzweig at New York University, which showed that radiation-attenuated P. falciparum sporozoites can illicit an immune response without causing malaria. The vaccine is currently in preclinical development and Sanaria plans to initiate a clinical trial programme during 2008. Other approaches to malaria vaccination currently in development are shown in Table 1, and include recombinant vaccines directed against one or many Plasmodium antigens, such as the merozoite surface protein (MSP-1), DNA-based vaccines, and virus-like particle vaccines.
There is unfortunately no 'silver bullet' which will lead to the eradication of malaria. It seems that the best hope is that large-scale initiatives such as the WHO Global Malaria Programme and the Roll Back Malaria partnership will make some headway in reducing the impact of the disease. In targeting the disease at many different levels, including effective insect control, low cost prevention strategies and the development and supply of safe and affordable prophylaxis and treatment to the people of the world most in need, these programmes undertake the holistic approach required to tackle the growing problem. The increase in non-profit organisations and drug development will also open up a more readily available drug portfolio for the developing world. The eradication of malaria seems a distant hope, but with high expectations of a vaccine breakthrough, this high-impact disease may one day be controllable.
Calida Neal
Image courtesy of James Gathany.
Taken from the CDC, Public Health Library (PHIL)
