Antimalarial vaccine

It has been estimated that about 500,000 million cases of malaria occur annually and about 1-2 million deaths due to Plasmodium falciparum are involved [1]. Most of these cases occur in tropical countries and there appears to be little systematic research to discover novel antimalarial drugs. Perhaps one of the reasons for this lack of interest is that there is hope that an antimalarial vaccine is the answer, but this is not expected to be available in the near future, if ever. 

Vaccination. Inspite of the tremendous impetus and thrust instituted legitimately by WHO, the dream of developing an effective, safer, economically viable antimalarial vaccine is yet to be discovered to combat the human sufferings, more specifically the rate of infant mortality in economically less privileged and developed countries of the world. 

M. E. Patarroyo, A. Bermudez and A. Moreno-Vranich, Towards the Development of a Fully Protective Plasmodium Falciparum Antimalarial Vaccine,... 

As a generalization, to be orally well absorbed a compound must be soluble in the contents of the gastrointestinal lumen [4]. Solubility in aqueous buffer is commonly used as a simpHfying surrogate for intestinal content solubility. There are rare exceptions to the principle that to be absorbed a compound must be soluble. SoHd particles, e.g. starch, can be absorbed. Absorption of very small quantities of even biologically very large compounds can occur via lymphoid tissue, e.g. orally active vaccines. Very hpophihc basic compounds, e.g. certain antimalarials, can be absorbed via the intestinal lymphatics and dehvered directly to the heart... 

Prophylaxis for malaria includes the administration of antimalarial tablets and protection against mosquito bites but does not include any vaccinations. Hepatitis C is a viral infection and no vaccine is available. Hepatitis B is a viral infection and prophylaxis is provided by a vaccine. 

Although some efficacious drugs have been known for centuries, such as the antimalarial quinine first used in 1639, most important discoveries are of more recent origin. Smallpox vaccine was discovered around 1800, morphine in 1820, aspirin in 1894, and phenobarbital in 1912. But the discovery of the antibacterial activity of sulfur drugs in 1932 and penicillin in 1940 started the golden era of rapid expansion and discovery in the industry. Nearly all important drugs today have been discovered since 1940, some very recently. 

A connection between swampy areas and fever was made centuries ago, and the word malaria reflects the popular belief that the illness was caused by bad air (Italian, mol aria). During the sixteenth century, people discovered that the disease could be treated using quinine, a compound derived from the bark of the tropical Cinchona tree. No vaccine for malaria has yet been developed, although preliminary trials for an initial vaccine were scheduled to begin in malaria-endemic areas in late 2003. Currently, the synthetic agent chloroquine is the most widely used antimalarial drug it can clear nonre-sistant parasites from the blood in two to three days. 

The Committee noted some of the activities of the United Nations Children s Fund (UNICEF) related to pharmaceuticals. These include qualification of suppliers, specifications for products, contracts with suppliers and the management of warehouses. It was noted that UNICEF uses the WHO lists of prequalified products and manufacturers in the procurement of HIV/ AIDS products and vaccines. Due to the lack of prequalified antimalarial products, an interim assessment process was used. Another problem identified was that some products included in the WHO Model List of Essential Medicines were not available on the market. 

The increasing prevalence of strains of P. falciparum that are resistant to chloroquine (CQ), a blood schizontocide which had been efficacious, safe, accessible and affordable, poses a serious problem for malaria control, predisposing Afiica to an unprecedented situation since the only affordable treatment options are rapidly losing therapeutic efficacy. Drug-resistant strains of P. falciparum are endemic in many areas of the world and the majority of conventional antimalarial drugs have been associated with treatment failure. These developments and the difficulty of creating efficient vaccines, coupled with adverse reactions to chemotherapy, underline the urgent need for novel, cheap, safe and... 

It is clear that these problems of (multiple) resistance are a serious concern. Although the discovery of a new antimalarial that would not eventually succumb to resistance would seem an impossible goal, new strategies based on the chemistry of bioorganometallics have been developed, which may help to hold the line imtil a vaccine becomes available [125]. 

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