7月22日出版的PLoS ONE雜誌上，發表的一項研究中，約翰.霍普金斯瘧疾研究院的研究者首次研製出一種瘧疾蛋白（Pfs48/45），這種物質可以在小鼠和非人類靈長類動物中產生明顯的免疫反應，可以作為一種阻斷瘧疾傳播的疫苗使用。Pfs48/45蛋白疫苗誘導出的抗體可以有效阻斷引起瘧疾的寄生蟲—瘧原蟲的性發育。瘧原蟲在蚊子體內生長，性發育是這種寄生蟲一生中的關鍵步驟，是瘧疾從蚊子到人類傳播的必要條件。
研究者約翰.霍普金斯Bloomberg公共衛生學院分子微生物學和免疫學系的Nirbhay Kumar博士說：「研製成一種可以成功阻斷傳播的疫苗，是控制瘧疾全球傳播的重要步驟。在我們的研究中，我們發現一種相對簡單的，可以在小鼠和非人類靈長類動物中表達和誘導阻斷瘧疾傳播的抗體。這種方法從機理上非常合理，也是在人類中檢測阻斷瘧疾傳播疫苗的基礎。」
研究中，研究者在大腸桿菌中表達了全長的Pfs48/45蛋白，用於生產疫苗。先前曾經有人嘗試過完全表達這種蛋白，但是沒有成功。在實驗室中，疫苗首次在小鼠體內應用。肯亞進行的類似實驗中，也在非人類靈長類（奧利夫狒狒）中進行了疫苗測試。根據這項研究，單劑量疫苗產生的免疫反應可以有效阻斷瘧疾傳播，有效率高達93%。在狒狒實驗中，如果幾個月後再次加強一針，有效率超過98%。
Kumar說：「這是一個令人興奮的開端，可能會在瘧疾控制和積極消除瘧疾傳播中成為重要工具。」人類瘧疾沒有動物儲藏處，因此有可能逐漸減少瘧疾傳播，直至幾乎完全根除。但是Kumar警告說，為了達到這個目的，還需要更多的研究。此外還需要進行類似的研究，研製出針對另外一種瘧原蟲的疫苗。
全球瘧疾感染波及五億人，估計每年會引起一百多萬人死亡，其中大多數是非洲兒童。(生物谷Bioon.com)
生物谷推薦原始出處：
PLoS ONE.doi:10.1371/journal.pone.0006352
A Potent Malaria Transmission Blocking Vaccine Based on Codon Harmonized Full Length Pfs48/45 Expressed in Escherichia coli
Debabani Roy Chowdhury1, Evelina Angov2, Thomas Kariuki3, Nirbhay Kumar1
1 Department of Molecular Microbiology and Immunology, Johns Hopkins University, Bloomberg School of Public Health, Baltimore, Maryland, United States of America
2 U.S. Military Malaria Vaccine Program, Walter Reed Army Institute of Research- Naval Medical Research Center (WRAIR-NMRC), Division of Malaria Vaccine Development, Silver Spring, Maryland, United States of America
3 Institute of Primate Research, National Museums of Kenya, Nairobi, Kenya
Malaria caused by Plasmodium falciparum is responsible for nearly 1 million deaths annually. Although much progress has been made in the recent past, the development of a safe, effective and affordable malaria vaccine has remained a challenge. A vaccine targeting sexual stages of the parasite will not only reduce malaria transmission by female Anopheles mosquitoes, but also reduce the spread of parasites able to evade immunity elicited by vaccines targeting pre-erythrocytic and erythrocytic asexual stages. We focused our studies on Pfs48/45, a protein expressed in the sexual stages developing within an infected person and one of the most promising transmission-blocking vaccine targets. Functional immunogenicity of Pfs48/45 protein requires proper disulfide bond formation, consequently evaluation of the immunogenicity of recombinant full-length Pfs48/45 has been hampered by difficulties in expressing properly folded protein to date. Here we present a strategy involving harmonization of codons for successful recombinant expression of full length Pfs48/45 in Escherichia coli. The purified protein, designated CH-rPfs48/45, was recognized by monoclonal antibodies directed against reduction-sensitive conformational epitopes in the native protein. Immunogenicity evaluation in mice revealed potent transmission blocking activity in membrane feeding assays of antisera elicited by CH-rPfs48/45 formulated in three different adjuvants, i.e. Alum, Montanide ISA-51 and complete Freund's adjuvant. More importantly, CH-rPfs48/45 formulated with Montanide ISA-51 when administered to nonhuman primates (Olive baboons, Papio anubis) resulted in uniformly high antibody responses (ELISA titers >2 million) in all five animals. Sera from these animals displayed greater than 93% blocking activity in membrane feeding assays after a single immunization, reaching nearly complete blocking after a booster dose of the vaccine. The relative ease of expression and induction of potent transmission blocking antibodies in mice and nonhuman primates provide a compelling rationale and basis for development of a CH-rPfs48/45 based malaria transmission blocking vaccine.