TOWARDS A VACCINE AGAINST MALARIA

For 20 years, the prospect of anti-malarial vaccination has aroused many hopes, but in the end, it has mostly given rise to doubts and disappointment. If most attempts have been to no avail, this is because the issue at stake is amazingly difficult. Besides the very complex antigenic structure of the protozoa Plasmodium, there is first the existence of at least three different targets during the plasmodial cycle, then the necessity of appropriate adjuvants and, most of all, the imperfection of our experimental models. Recently, Pattaroyo and the various groups who worked with him have eventually met success with vaccine trials in man: they used a synthetic antigene, SPf66, on volunteers in South America, then on a larger population sample in East Africa. The results are still quite modest: people are protected against the malarial disease but not against the parasitemia and only in approximately 40% of cases. Nevertheless, these results have the merit or representing the first successful anti-malarial vaccination in man. Although great advances are still needed, a decisive step forward has been taken. Other types of vaccine will soon be tested by other groups (anti-gametocyte vaccines) and prospects of significant improvements are offered by the technique of DNA-vaccines. If it is now certain that one or several vaccines will be available ina near future, no one is able to set the time delay necessary to reach this stage. In any case, hoping that this type of vaccine will eradicate the disease is not realistic since a disease as complex as malaria, in terms of epidemiology, cannot be eliminated by only one method. It is probable that only the wise use of all the techniques available (anti-vectorial protection and fight, chemoprophylaxis and chemotherapy) will lead to success. Vaccination will then come as a complement when it is available.