Recent advances on vaccines against malaria: A review

This review aims to summarize the currently viable vaccine strategies including the approved vaccines and the those in trials for next-generation malaria vaccines.Data on malaria vaccine development was collected through a comprehensive review.The literature search was performed using databases including Google Scholar,PubMed,NIH,and Web of Science.Various novel approaches of vaccination are being developed,including those based on radiation-attenuated strategies,monoclonal antibodies,targeted immunogenic peptides,RNA and DNA vaccines,nanoparticle-based vaccines,protein-based vaccination protocols,and whole organism-based vaccination strategies.Trials on RTS,S have entered phase Ⅲtesting,and those based on blood-stage vaccines and vaccines to interrupt malarial transmission have advanced to higher stages of trials.Mathematical modeling,combined drug and vaccine strategies,mass drug administration,polyvalent vaccine formulations,and targeted vaccination campaigns is playing an important role in malarial prevention.Furthermore,assessing coverage,accessibility,acceptability,deployment,compilation,and adherence to specific vaccination strategies in endemic regions is essential for vaccination drives against malaria.

Malaria vaccines:looking back and lessons learnt

The current status of malaria vaccine approaches has the background of a long and arduous path of malaria disease control and vaccine development.Here,we critically review with regard to unilateral interventional approaches and highlight the impact of socioeconomic elements of malaria endemicity. The necessity of re-energizing basic research of malaria life-cycle and Plasmodium developmental biology to provide the basis for promising and cost-effective vaccine approaches and to reach eradication goals is more urgent than previously believed.We closely analyse the flaws of various vaccine approaches,outline future directions and challenges that still face us and conclude that the focus of the field must be shifted to the basic research efforts including findings on the skin stage of infection.We also reflect on economic factors of vaccine development and the impact of public perception when it comes to vaccine uptake.

R21 vaccine:A ray of hope for malaria elimination

The steady decline in malaria cases and deaths in recent years is a step ahead toward elimination;however,an increasing number of reports of antimalarial and insecticide resistance highlight the importance of having newer approaches to achieve the goal in the stipulated time frame.Therefore,having an effective and durable malaria vaccine is extremely crucial,which can complement the tools currently in use.Although the malaria vaccine development efforts initiated in the 1910’s with the first attempts to develop a malaria vaccine involved inoculating humans with live,attenuated strains of the malaria parasite but the efforts have been intensified over the previous decade,resulting in several significant developments.

Acceptance,availability and feasibility of RTS,S/AS01 malaria vaccine:A review of literature

Malaria remains the most serious infectious disease and is one of the leading causes of death among children in malaria endemic areas.The development of malaria vaccines has been underway since 1960s.Significant progress in the development of vaccine has been made in the last decade.On 6 October 2021,World Health Organization recommended widespread use of the RTS,S/AS01 malaria vaccine.The level of acceptance of RTS,S/AS01 malaria vaccine is relatively low in middle-income countries.This might be because of lack of information regarding vaccine implementation in such countries.The proper and efficient execution of the malaria vaccination program necessitates careful consideration of each community's socio-cultural setting.The most prominent RTS,S/AS01 vaccine trial was conducted from 2009 to 2011 in which eleven sites in seven African countries participated.Results of the trial,published in 2015,provided a promising advance in the development of a malaria vaccine for African children.As of 2019,large-scale pilot studies of the vaccine have been conducted in Ghana,Kenya,and Malawi,involving several hundreds of thousands of infants.The RTS,S/AS01 vaccine shows modest efficacy against malaria and has a feasible mode of administration.Although there is increased risk of meningitis,cerebral malaria,pneumonia,anemia,febrile convulsions and gastroenteritis,the vaccine still has a feasible mode of administration and high cost effectiveness and can be easily implemented in resource-limited settings.

Bridging the Knowledge Gap in Transmission-Blocking Immunity to Malaria: Deciphering Molecular Mechanisms in Mosquitoes

The worldwide decline over the last decade in the number of clinical cases of malaria does not mean an end to the universal problem of malaria pathogenesis in those afflicted by infection. Resistance to drugs, higher risk of disease relapse and failure to maintain effective memory of the pathogen in the absence of persistent exposure result in the repeated failure of anti-malarialtreatments. The artificial blocking of transmission of the Plasmodium parasite between hosts from human to Anopheles mosquito, and vice versa, is crucial to restricting the spread of disease. However, a limited knowledge of the molecular mechanisms in operation for transmission of malaria has impeded progress towards a transmission-blocking vaccine. This review highlights the role of anti-malarial immune responses to antigen-specific targets for designing effective vaccines against the sexual stages of Plasmodium that occur within the invertebrate vector. In particular, artificial induction of gametocyte and ookinete apoptosis as a novel means to prevent gamete fertilization and oocyte development, respectively, is highlighted. This and other recent insights into our understanding of the molecular regulation of transmission-blocking immunity are discussed and future prospects considered.

Oral vaccination of mice against rodent malaria with recombinant Lactococcus lactis expressing MSP-1_(19)

AIM： To construct the recombinant Lactococcus/actis as oral delivery vaccination against malaria. METHODS： The C-terminal 19-ku fragments of MSP1 （MSP-119） of Plasmodium yoelii265-BY was expressed in L. lactis and the recombinant L. lact/s was administered orally to BALB/c and C57BL/6 mice. After seven interval vaccinations within 4 wk, the mice were challenged with P. yoelii 265-BY parasites of erythroo/tic stage. The protective efficacy of recombinant L. lactiswas evaluated. RESULTS： The peak parasitemias in average for the experiment groups of BALB/c and C57BL/6 mice were 0.8± 0.4% and 20.8±26.5%, respectively, and those of their control groups were 12.0±0.8% and 60.8±9.6%, respectively. None of the BALB/c mice in both experimental group and control group died during the experiment. However, all the C57BL/6 mice in the control group died within 23 d and all the vaccinated mice survived well. CONCLUSION： The results imply the potential of recombinant L. lactis as oral delivery vaccination against malaria.

Immunogenicity and immunizing protection effect of GAMA gene DNA vaccine on Plasmodium berghei

Objective: To explore the effect of immunogenicity and immunizing protection of GAMA gene DNA vaccine, which was related with merozoite, ookinete and sporozoite invasion. Methods:Gene fragments were obtained using PCR technique and eukaryotic expression vector(containing immunostimulatory sequence) was built. BALB/c mice were divided into PBS control group, empty vector control group and study group and were immunized at week 0, 3 and 6 respectively. Blood was collected 2 weeks after each immunization and serum was separated to detect the Ig G, Ig G1 and Ig G2 a levels. Spleen of mice was obtained for preparation of splenic mononuclear cell and the cytokine IL-4 and IFN-αlevels were detected. Indirect immunofluorescence and western blot were employed to verify the specificity of antiserum. Sporozoite and merozoite invasion were used respectively to detect the immune protective effect 2 weeks after the third immunization. Ookinete conversion rate in vitro and oocyst numbers of mosquito stomach were observed to evaluate the transmission-blocking levels. Results: In GAMA DNA vaccine group: antiserum could be combined with recombinant protein specifically and green fluorescence signals of merozoite, ookinete and sporozoite were observable, while specific fragments and fluorescence signals were not observable in empty vector group. Compared with control group, specific Ig G in DNA vaccine immunity group significantly increased(P<0.01), and Ig G1 and Ig G2 a all increased(P<0.01). IL-4, IFN-αcontent in study group significantly increased, compared with control group(P<0.01). GAMA DNA vaccine immunity could not obviously block the erythrocyte-stage infection(caused by sporozoite invasion); compared with control group, liver worm load was slightly reduced(P<0.05), and antiserum ookinete numbers(cultured in vitro) had no significant difference with oocyst numbers of mosquito stomach in DNA vaccine group. Conclusions:GAMA has good antigenicity, which could stimulate the body to produce specific immune responses; while DNA vaccine immunity could not play a good protective effect, the effect of which is only limited to the slight reduction of liver worm load, and has no obvious erythrocytestage protective effect and transmission-blocking effect. Therefore, trying other immunization strategies for further research on the value of GAMA(as multi-stage antigen vaccine and multistage combined vaccine components of the life-cycle of plasmodium) is necessary.

From control to eradication of malaria:the end of being stuck in second gear?

More than 2 billion people are at risk of malaria,which primarily affects poor populations in tropical and subtropical areas,including Southern Asia.As malaria incidence has been reduced strongly in some parts of endemic regions by combinations of interventions,including artemisinin-based therapies and insecticide-treated bed nets,a new goal has been established recently by charity foundations which support research on malaria:the worldwide eradication of the pathology.Doing away with control approaches which have been applied for the last 50 years and more focus on elimination objectives will deeply change priorities in the area of malaria treatment,chemoprevention,vector control,vaccine research and health system assessment.In this review,actual knowledge on pathogenesis and pharmacology is discussed,and new drugs, vaccines and insecticides are described.

Effects of the configuration of a multi epitope chimeric malaria DNA vaccine on its antigenicity to mice

Objective Four B and Th cell epitopes were selected from conservative domain of Plasmodium falciparum antigens to construct two groups of chimeric malaria DNA vaccines with different configurations and their antigenicities were studied Methods The partially synthesized oligonucleotide was annealed, PCR amplified and cloned into a mammalian cell expression vector By using a pair of isocaudamers on the vector, different single copies of B epitopes were multiplied and were tenderly stringed into two groups of chimeric DNA vaccine with different configurations BALB/c mice were immunized with these DNA plasmids by either intramuscular or intradermal injections Results The antisera from the immunized mice tested by ELISA showed that only the configuration which had a single copy of universal T helper cell epitope, CS T3, located at the C terminal of the multi copy B cell epitopes induced a high antibody response The T helper cell epitope at any other position of the peptide, or the double T helper cell epitopes configured with the B cell epitopes did not enhance antibody response, and some configurations even decreased the humoral response to a B cell epitope Conclusion This study demonstrated that both combination and configuration of the epitope may affect the antigenicity of a chimeric multiple antigen

同尾酶技术在构建疟疾多价重组DNA疫苗中的应用

同尾酶是一类识别不同核苷酸序列但能酶切产生相同粘性末端的限制性内切酶，依靠同尾酶的这种特性，可以根据需要将不同的ＤＮＡ 片段进行灵活组合，获得各种排列顺序的多价表位重组疫苗．将这种方法用于疟疾多价重组ＤＮＡ 疫苗的研制；ＢＡＬＢ／ｃ 小鼠免疫实验对所得重组疫苗ＰＵ２８６的免疫原性进行了测定．

我国疟疾疫苗研究进展及前景

研发安全有效的疟疾疫苗是当前全球疟疾防治的重要需求。以生物技术为代表的新型技术的应用,有效推动了疟疾疫苗的研发进程。30多年疟疾疫苗研发已取得了重要的成果,鉴定了一批有价值的疫苗候选抗原,其中一些已进入临床试验,一些结果令人鼓舞。我国疟疾疫苗研发同样取得可喜进展。自主研制PfCP-2.9疟疾疫苗在国内率先进入临床试验,一些疟疾疫苗候选抗原也陆续进入临床前研究阶段。近年来,多种国家科技计划和国际上研究经费的投入也促进我国疟疾疫苗的研发工作。尽管研发有效疫苗以控制乃至根除疟疾是个长期目标,取得疟疾疫苗突破仍需在疟疾免疫学以及多个技术层面上解决一些关键问题,但我们正在朝着这个目标迈进。

Pfs25蛋白单克隆抗体的制备及双抗体夹心ELISA的建立

目的:制备恶性疟原虫子孢子囊表面膜蛋白Pfs25的单克隆抗体(mAb),建立检测Pfs25蛋白的双抗体夹心ELISA方法。方法:纯化毕赤酵母表达的重组Pfs25蛋白,并免疫BALB/c小鼠,采用骨髓瘤细胞Sp2/0与免疫BALB/c鼠脾细胞杂交的细胞融合技术,通过间接ELISA检测获得分泌抗Pfs25抗体的阳性杂交瘤细胞株,通过免疫F1鼠诱生腹水,纯化腹水,并进行mAb的各项生物学鉴定。辣根过氧化物酶(HRP)标记纯化后的抗体,以4B7为包被抗体,1B4为酶标抗体,建立了双抗体夹心ELISA法。结果:获得3株抗Pfs25的杂交瘤细胞株,其中2株有良好的稳定性和特异性。并建立了双抗体夹心ELISA检测法,检测有效范围在0.07～1 mg/mL,其检测灵敏度为41.6 ng/mL。结论:成功制备抗Pfs25蛋白的单克隆抗体,并建立了一种可用于Pfs25蛋白检测的双抗体夹心ELISA法,为Pfs25蛋白制备传播阻断型疟疾疫苗奠定了基础。

恶性疟原虫传播阻断抗原Pfs25和Pfs48/45基因编码序列的体外扩增

目的：体外扩增编码恶性疟原虫传播阻断抗原Pfs和Pfs48／45的基因序列，为进一步对其进行克隆和体外高效表达创造条件。方法：特定寡核苷酸引物的设计、合成与纯化；恶性疟原虫FCC1／HN株体外培养；利用碱裂解法从培养的恶性疟原虫FCC1／HN株提取染色体DNA；PCR扩增和琼脂糖凝胶电泳分析。结果：从恶性疟原虫FCC1／HN株基因组DNA中特异扩增出编码Pfs25和Pfs48／45基因序列，其片段大小分别为657bp和1，359bp。而用间日疟原虫基因组DNA为模板作对照，无扩增条带出现。结论：体外扩增编码恶性疟原虫传播阻断抗原Pfs25和Pfs48／45基因序列与预期长度相符合，从而，为该基因的克隆、测序和表达奠定基础。

一种新型疟疾核酸疫苗生产工艺的初步研究

疟疾是危害人类健康和生命的主要寄生虫病之一,寻找合适的疫苗一直是该病控制的重要方向。在疟疾核酸疫苗方面作了系列尝试,取得较好研究结果,并最终构建了以胸腺嘧啶合成酶基因为筛选标记的、具有大肠杆菌平衡致死特征的新一代疟疾核酸疫苗pThyAAWTE。对影响工程菌高密度发酵的几个因素进行了分析,所优化程序可使工程菌发酵密度达OD60 0 60以上;此外,还对质粒初步纯化过程中的几个重要参数进行了分析,初步结果表明,悬浮液体积(ml) :菌体湿重(g)在2 :1以上,对质粒的得率没有明显影响;碱裂解时间在一定范围内不影响质粒的质量;合适的悬浮液体积/裂解液/中和液比能明显提高质粒产量;用优化程序所提取的质粒其产量与试剂盒提取的量相当。为pThyAAWTE的大规模纯化打下了基础。

重组霍乱毒素B亚基与疟原虫多表位融合蛋白的免疫保护作用研究

对以霍乱毒素B亚基为载体蛋白的重组疟疾多价抗原在小鼠及恒河猴中的免疫原性及对相应疟原虫感染的免疫保护作用进行了研究。结果表明 :该抗原免疫小鼠后 ,对约氏疟子孢子攻击的保护率在 5 0 %左右 ;恒河猴免疫后用 1× 10 8食蟹疟裂殖子攻击 ,对照组 2只动物在攻击后 4d感染 ,感染持续 30d以上 ;免疫组 2只动物中 ,两只动物在感染 6～ 7d后完全恢复 ,且 1只推迟 3d感染 。

中国脑型疟患者恶性疟原虫分离株裂殖子表面蛋白MSP1第16-17区基因和MSP2基因的分子克隆与鉴定

目的 :为设计研制安全有效的人脑型疟疫苗提供理论依据。方法 :根据 MAD2 0株裂殖子表面蛋白 1( MSP1)和 FC2 7株裂殖子表面蛋白 2 ( MSP2 )基因编码区高度保守碱基设计并合成两对引物 ,应用多聚酶链反应 ( PCR)技术对 5例脑型疟患者恶性疟原虫云南省勐腊县勐罕分离株 CMH/ YN和云南省盈江县农场 CYJ/ YN分离株基因组 DNA MSP1第 13- 17区基因和MSP2基因进行扩增 ,并将扩增产物分别经 Eco RI和 Kpn I,Bam HI和 Hind III双酶切后 ,分子定向克隆 M13mp18和 M13mp19载体 ,转染大肠杆菌 ( E.coli) TG1,从含 X- gal和 IPTG的 LB平板上 ,将随机筛选得到的单个无色噬菌斑经 E.coli JM10 3扩增 ,用碱裂解法抽提重组子复制型DNA ( RFDNA)后 ,再分别经 Eco RI和 Kpn I,Bam HI和 Hind III双酶切鉴定。结果 :证实重组子为编码脑型疟患者恶性疟原虫 CMH/ YN和 CYJ/ YN分离株 MSP1第 16- 17区基因和 MSP2基因分子克隆 M13载体。结论 :首次报道确证脑型疟患者恶性疟原虫 CMH/ YN和 CYJ/ YN分离株MSP1第 16- 17区基因和 MSP2基因分别与 MAD2 0株 MSP1和 FC2 7株 MSP2相应基因完全一致。这些发现对研究预防人脑型疟疫苗和建立一种新型脑型疟恶性疟原虫检测方法具有重要意义。

疟原虫环子孢子蛋白的研究进展

环子孢子蛋白(circumsporzoite protein,CSP)是疟原虫成熟子孢子表面的锚定蛋白,约含400个氨基酸,由N端保守I区、种属特异性的中央重复区和C端保守Ⅱ区构成。CSP在疟原虫的迁移、靶细胞入侵和增殖过程中发挥重要作用。近年研究显示,CSP在疟疾疫苗和靶向给药系统中具有良好的应用前景。本文对疟原虫CSP的结构特征、功能及其应用前景作一综述。

疟疾偶联疫苗

很多疟疾抗原在人体中是弱免疫原,化学偶联是一种提升弱免疫原免疫原性的方法,其价值已在疟疾疫苗的研究工作中得到证明。本文介绍了蛋白质偶联的一些常用化学连接剂和载体蛋白,并综述了疟疾偶联疫苗的研究进展。

恶性疟原虫基因工程疫苗的研究——Ⅰ.恶性疟原虫保护性抗原复合基因的合成与克隆

本文应用基因工程技术,设计并化学合成了编码恶性疟原虫红内期保护性抗原MSA_1,MSA_2和RESA上多个免疫原性决定簇(含T、B细胞位点)以及来自白细胞介素-1(IL-1)和破伤风类毒素(TT)上的外源性T细胞激活位点的复合基因HGFC。全基因共由246个碱基对组成,编码一个75肽的复合抗原。合成后的基因克隆在M13mp18载体上,并经序列分析证实与设计完全一致。杂合基因合成和克隆的成功,为在基因水平上进行多价疟疾疫苗的蛋白质工程研究创造了条件。

人工合成恶性疟原虫复合基因在大肠杆菌中的表达及产物的初步鉴定

将人工合成与构建的恶性疟原虫保护性抗原复合基因ＨＧＦＣ和ＨＧＦＣＡＣ分别与表达载体ｐＷＲ４５０－１重组并转化大肠杆菌ＪＭ１０９，工程菌经ＩＰＴＧ诱导后表达出含外源基因产物与β－半乳糖苷酶部分氨基酸的融合蛋白，分子量分别为６５ｋＤａ和７７ｋＤａ。免疫印迹分析显示表达产物可与兔抗恶性疟原虫ＲＥＳＡ多肽抗原的抗体发生特异性免疫反应，提示融合蛋白中含有恶性疟原虫抗原位点。