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THe PfSPZ vaccine is a candidate malaria vaccine made of non-replicating irradiated whole sporozoites and developed by Sanaria. PfSPZ is the acronym of words: ''Plasmodium falciparum'' (Pf) and sporozoites (SPZ). Clinical trials have been promising, but it has been subject to some criticism regarding its ultimate feasibility with regard to large-scale production and delivery in Africa, since it must be stored in super-cold liquid nitrogen. == History == In the first half of the 20th century there were first attempts to protect people from malaria. At the beginning Pasteur´s approach of developing bacterial vaccines was used as a big hope in eradication of this fatal disease. But inactivated malaria sporozoites (by formalin) were ineffective in inducing the protection. In 1948 inactivated merozoites with an adjuvant were used for preventing lethal malaria to kill a group of monkeys. But the strong toxicity of the adjuvant and inability to obtain sufficient count of parasites from human blood stopped further efforts in this way. In 1967 irradiated malaria sporozoites (extracted from salivary glands of infected mosquitos) induced immune response in mice without the need of the adjuvant and similar evidence obtained in human volunteer trials. The mice were exposed to irradiated mosquitos infected by malaria parasites. Mice and volunteers did not acquire malaria because mosquitos and the sporozoites were irradiated and their immune cells triggered response that could protect them from following infection. Yet this approach was not further developed during problems with obtaining sufficient number of sporozoites and with the harvesting of parasites. Later, modern adjuvants and the possibility of preparing of single parasite proteins started another way to obtain malaria vaccine. Today, a vaccine called RTS,S based on coat protein of sporozoites of the ''Plasmodium falciparum'' is the most advanced subunit vaccine and is in the phase III clinical trials. It protects about 50% of subjects infected by controlled human malaria infection (CHMI) after 2 – 3 weeks and about 23% at 5 months after last immunization. In large III phase trial in Africa RTS,S/AS01 reduced acquired malaria over a 12 months period by 31,3% and 36,6%. In 2003 Sanaria ran trials in which ''falciparum'' sporozoites were manually dissected from salivary glands of mosquitos, irradiated and preserved before inoculation with one goal: to develop and commercialize a non-replicating, metabolically active PfSPZ vaccine. In human volunteer trials PfSPZ was applied subcutaneously (SC) or intradermally (ID) and such as it showed only modest immune response. When PfSPZ was injected intravenously (IV) to nonhuman primates or mice it finally triggers CD8+ T-cells producing IFNγ. These T cells are believed to be the main immunologic mechanism to fight malaria in liver. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「PfSPZ vaccine」の詳細全文を読む スポンサード リンク
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