Katherine Stapp

NEW YORK, Dec 26 2001 (IPS) — Researchers report significant progress in their years-long quest to develop an effective and affordable vaccine for malaria, which is estimated to afflict as many as 500 million people, and to kill more than one million of them, per year.

Doctors in the Gambia, in West Africa, say an experimental malaria vaccine successfully blocked the parasite in about one-third of the adult male test subjects, making it one of the most advanced vaccine candidates tested so far.

Across the Atlantic Ocean, the U.S.-based National Institutes of Health (NIH) and a private laboratory, Genzyme Transgenics Corporation, report having inoculated Aotus monkeys with an experimental vaccine secreted by a specially developed strain of mice.

Only one in five of the monkeys that was injected with the milk became sick from malaria, compared to six out of seven unvaccinated monkeys.

While the technique needs a lot more study, researchers say it raises the possibility that a small herd of cows and goats some day could be genetically engineered to produce large-scale, cheap stocks of a malaria vaccine.

“Malaria causes untold suffering in the poorest regions of the world, so we cannot restrict our focus simply to finding a vaccine that works,” said Anthony S. Fauci, director of the National Institute of Allergy and Infectious Diseases, a division of the NIH.

“Rather, we must look for innovative strategies that will bring effective vaccines to regions where economic conditions preclude the use of costly alternatives,” Fauci added. “Transgenic animals could be one way to accomplish that goal.”

Transgenic animals contain one or more genes that have been artificially introduced from another organism. Assuming the technique worked with larger animals like cows and goats – something with which Genzyme already has been experimenting – the milk could be used to inoculate some 20 million people per year.

However, Anthony Stowers, a leading NIH scientist on the project, cautioned that the particular malaria vaccine administered in the mouse experiment was not safe for use in humans because it stimulated the immune system too much. The research was reported in the Proceedings of the National Academy of Sciences on Dec. 18.

A better candidate is the Gambia vaccine, developed by the European pharmaceutical giant GlaxoSmithKline. According to data reported in the British medical journal The Lancet, it has proven 34 percent effective in human trials where the subjects were given three doses, and 47 percent effective when a fourth dose was administered.

Kalifa Bojang, of the Medical Research Council Laboratories in the Gambia, noted that the vaccine had only been tested on adults and might prove less safe or effective among children, who are the primary victims of malaria.

Nevertheless, Bojang added, the success of the Gambian trials means that “we are on the right path.”

Phase II trials involving children between the ages of one and five are set to begin in Mozambique, according to Regina Rabinovich, director of the Malaria Vaccine Initiative, a U.S.- based non-profit organisation and partner of GlaxoSmithKline.

Rabinovich said that while the Gambia subjects were followed for 15 weeks, the Phase II trials planned for Mozambique would involve year-round assessment of the vaccine’s efficacy.

The vaccine works by preventing Plasmodium falciparum, the deadliest of four parasites that cause malaria, from entering red blood cells and disabling the immune system. It is known by the code name RTS,S/AS02.

Malaria is spread through the bite of mosquitoes. Symptoms include high fever, anaemia, chills, and vomiting. More than 15 percent of those who survive malarial attacks are left with severe neurological damage and impaired function. Drugs are available to treat the disease but the parasite has evolved resistance to them in many areas.

In the absence of a vaccine, health authorities have focused on eliminating the mosquitoes that transmit the malaria parasite to humans through the use of bednets, extensive spraying of pesticides like DDT, and other methods.

However, in parts of Africa and Asia where malaria is endemic, these efforts have not made much of a dent, according to experts, because the mosquito populations are too enormous.

Another avenue of attack is to disable the ability of mosquitoes to transmit the parasite, which scientists are pursuing by sequencing the genome of the Anopheles gambiae mosquito, one of the main carriers.