Three non-repeated transmission blocking epitopes recognized in the 21 kD surface antigen of zygotes-ookinetes of Plasmodium berghei.

Two-site and competitive ELISA have been developed against a surface antigen of zygotes-ookinetes of Plasmodium berghei using monoclonal antibodies (MoAbs) which block transmission of the parasite to the mosquito. Three such MoAbs have been studied, each of which recognized a protein of an Mr 21 kD (Pbs21) using immunoblot techniques. The assays showed that there are at least 3 single B-cell epitopes expressed in Pbs21. One epitope recognized by MoAb 17.9 is conformation dependent and antibodies bound to it interfered with other MoAbs (12.1 and 13.1) each recognizing a different, apparently linear epitope. Glycosylation might not be relevant to the binding of any of the antibodies tested to their respective epitopes.     

Role of macrophage-processed antigen in a Plasmodium berghei model

Summary The present study demonstrates that malarial parasite could be processed by macrophages in vitro to release 'super antigens'. These super antigens obtained from the peritoneal macrophages were more protective than those processed by the splenic adherent cells. BCG-stimulated macrophages were also able to process the antigens efficiently and these antigens were even superior to those obtained from the unstimulated macrophages. These modified antigens were potent inducers of DFPS to malarial antigens. It is thus concluded that parasite antigens, processed in vitro, carry specific immunogenic potential and are able to protect the recipients to parasite challenge.     

Studies on the immunogenicity of a recombinant ookinete surface antigen Pbs21 from Plasmodium berghei expressed in Escherichia coli

Plasmodium berghei ookinete surface antigen (Pbs21), was produced as a fusion product with maltose binding protein (MBP) in Escherichia coli and used to induce transmission-blocking immunity in mice. Specificity of induced antibody was confirmed by Western blotting with native ookinete Pbs21, and by the indirect immunofluorescent antibody test on ookinete bloodfilms. Immunized mice were infected with P. berghei and transmission to Anopheles stephensi mosquitoes determined by both the intensity and prevalence of oocyst infections. Compared with a control group immunized with MBP alone the maximum blockade of oocyst intensity was 66% in the mice immunized with recombinant MBP-Pbs21. Over nine experiments blockade averaged only 33%. By comparison with native Pbs21 protein, which usually induces 90% blockade, our data suggests the recombinant protein produced in this bacterial system is a less effective immunogen despite expressing epitopes recognized by known transmission-blocking monoclonal antibodies.     

约氏疟原虫与伯氏疟原虫侵入期抗原的初步研究

目的　用针对鼠约氏疟原虫(Plasmodiumyoelii)侵入期的8种单克隆抗体,对约氏疟原虫和伯氏疟原虫(P.berghei)侵入期即动合子、裂殖子和子孢子棒状体和表面抗原检测分析。　方法　间接免疫荧光实验(IFA)对各侵入期抗原进行亚细胞结构定位,SDSPAGE及Western印迹对两种鼠疟原虫的不同侵入期进行抗原组分分析。　结果　经上述两种方法检测发现,顶端复合体抗原成分复杂,约氏疟原虫和伯氏疟原虫的棒状体有共同的抗原表位,约氏疟原虫的动合子与其自身的裂殖子有类似成分,也有各自独特的抗原。两种鼠疟原虫动合子抗原有类似成分。约氏疟原虫的子孢子具有与裂殖子、动合子不同的抗原成分。　结论　疟原虫侵入期棒状体和表面抗原在同一虫种的不同侵入期和不同虫种中有共同的抗原表位,也有各自的独特组分。     

Ookinete antigens of Plasmodium berghei. Appearance on the zygote surface of an Mr 21 kD determinant identified by transmission-blocking monoclonal antibodies

Zygotes and ookinetes of the rodent malaria Plasmodium berghei can be enriched 50-fold, from whole blood cultures by ammonium chloride lysis. Three monoclonal antibodies (MoAbs) raised against such enriched preparations specifically bind to a determinant of Mr 21 kD as assessed by 125I-labelled goat anti-mouse IgG probed immunoblots of Western transfers of SDS-PAGE gels. Indirect immunofluorescence indicates that the 21 kD determinant bound by specific MoAbs, whilst not detectable on gametocytes or gametes, appears on the parasite surface within 2 h of exflagellation/fertilization and increases thereafter. The three MoAbs specifically binding the 21 kD determinant block oocyst development in mosquitoes by at least 90%, as assessed either by in-vitro membrane feeds or by live feeds on passively immunized mice. These MoAbs reduce ookinete formation in vitro by between 52 and 100%. Possible mechanisms of action of these MoAbs are discussed.     

Transmission-blocking antibodies against multiple, non-variant target epitopes of the Plasmodium falciparum gamete surface antigen Pfs230 are all complement-fixing

We have studied the properties of 16 newly derived monoclonal antibodies (MoAbs) against Pfs230, a gamete surface protein of Plasmodium falciparum and a target of transmission-blocking antibodies. All 16 MoAbs recognized Pfs230 by immunoprecipitation from non-ionic detergent extracts of the protein radio-labelled with ¹²⁵Iodine. The MoAbs also recognized this protein on Western blots under non-reducing conditions but none of them recognized the protein under reducing conditions. Using an immunoradiometric assay the MoAbs appear to define nine different epitope regions. The MoAbs were tested for their ability to lyse extra-cellular female gametes of P. falciparum isolate 3D7. Eight of the MoAbs, all of isotype IgG2a, mediated complement-dependent lysis of the gametes; seven of the MoAbs, all isotype IgG1, failed to lyse the gametes in the presence of active complement. The eight complement-fixing MoAbs mediated almost total suppression of infectivity of gameto-cytes of P. falciparum 3D7 to mosquitoes; where tested this suppression was mainly complement-dependent. The seven non-complement-fixing MoAbs had no significant effect on the infectivity of gametocytes of P. falciparum 3D7 to mosquitoes. When tested by immunofluorescence the target epitopes of all the MoAbs were conserved in each of the five different isolates of P. falciparum which were tested.     

伯氏疟原虫氯喹抗性逆转的实验观察

目的 寻找伯氏疟原虫氯喹抗性逆转剂.方法 将健康昆明小鼠72只(雌、雄各半)每只腹腔注射0.2 ml伯氏疟原虫ANKA株氯喹敏感系(chloroquine sensitive,CS)或由其选育的高抗氯喹系(chloroquine resistance,CR),按下述随机分组后灌胃给药治疗,观察各组疗效.(1)小鼠感染CS疟原虫30 min后随机均分为4组,每组6只,给D-6182{(Z,Z)-N,N,N-三甲基-2,3-双[(1-氧代-9-十八碳烯酸)-氧代]-1-丙胺基盐酸盐|、C-2832[胆畄醇-3-N-(二甲胺基乙基)氨甲酸酯]、Ket(酮替酚)、0.1%西黄蓍胶(对照组),连续灌药5 d.于D1至D7每天每鼠取尾血涂片作常规镜检,确定各实验组的原虫血症.(2)小鼠感染CR疟原虫后第3天随机均分为8组,每组6只,给D-6182、C-2832、Ket组、氯喹组、0.1%西黄蓍胶对照组及给予D-6182、C-2832、Ket后2 h再加灌服小剂量12 mg/(kg·d)氯喹(5%ED90),连续5 d.每鼠于D4至D7每天取尾血涂片作常规镜检,确定各实验组的原虫血症,并计算各组的原虫减虫率.结果 (1)感染伯氏疟原虫CS株的小鼠,分别灌服80 mg/(kg·d)D-6182、120 mg/(kg·d)C-2832或10 mg/(kg·d)Ket连续5 d,各给药组与对照组小鼠的原虫感染率自D1至D4逐日上升,至D4达峰值,D5时对照组小鼠原虫感染率继续上升,而各给药组维持在D4的峰值水平.(2)感染伯氏疟原虫CR株的小鼠给适宜剂量的C-2832、D-6182或Ket后2 h加灌服小剂量氯喹12 mg/(kg·d)(5%ED90),此后连续5 d(D3-D7),于D4原虫减虫率可达到97.77%、99.28%或96.73%,而在D7可达到99.81%、98.87%或100.00%.结论 C-2832和D-6182两种化合物对伯氏疟原虫CR株感染小鼠的氯喹抗性具有逆转作用,其逆转能力与Ket相当.     

The roles of the glycosylphosphatidylinositol anchor on the production and immunogenicity of recombinant ookinete surface antigen Pbs21 of Plasmodium berghei when prepared in a baculovirus expression system

Malarial ookinetes express an immunodominant surface protein (P28) that is a priority candidate for the development of transmission-blocking vaccines. The full length P28 gene from Plasmodium berghei [Pbs21(1-213)] and a deletion construct [Pbs21(1-188)] encoding a protein that lacks the 25 C-terminal amino acids, including the glycosylphosphatidylinositol (GPI) anchor signal, were expressed in insect cells using baculovirus vectors. Pbs21(1-213) protein is strongly hydrophobic, found in the cytoplasm and on the surface of Spodoptera Sf21 cells, and in the culture medium. Pbs21(1-188) protein was largely found in the aqueous phase of the medium and in the cytoplasm of Sf21 cells, but was not detected on the cell surface. The presence of 25 C-terminal amino acids is therefore critical to the attachment of recombinant Pbs21 to the parasite plasma membrane. Mice were immunized subcutaneously or intramuscularly with affinity purified recombinant Pbs21(1-213), Pbs21(1-188) or native Pbs21 proteins. Following two immunizations, native Pbs21 induces higher titres when administered by either route, than the recombinant protein bearing an insect GPI anchor, which in turn is markedly more immunogenic than the recombinant polypeptide lacking a GPI anchor. When specific anti Pbs21 antibody titres exceeded 1 mg/ml all three antigens were capable of inducing transmission blockade > or = 90%, below 1 mg/ml blockade did not correlate with antibody concentration.     

Vaccination to prevent transmission of Plasmodium yoelii malaria

Summary It was possible to block the transmission of infection of the rodent malaria parasite Plasmodium yoelii nigeriensis to Anopheles stephensi mosquitoes by immunizing mice with a vaccine containing formalin-fixed gametes. Both intramuscular and intravenous routes were effective, immunity was achieved with a single dose and the immunity persisted for 6 months at least. Transmission-blocking immunity was found to reside in a serum factor, probably antibody, and to be directed against extracellular gametes, acting on them in the gut of the mosquito, while gametocytes in the circulation of the vertebrate host remained unaffected. The gamete vaccine afforded partial protection against the disease, but immunization with asexual parasites alone showed that this protection was due largely to the presence of asexual forms as contaminants and that anti-gamete immunity is stage specific.     

伯氏疟原虫青蒿素抗性系的培育研究

目的　培育伯氏疟原虫青蒿素抗性系。　方法与结果　采用伯氏疟原虫接种传代和青蒿素剂量递增法分3条路线进行培育 :A线 ,青蒿素起始剂量为 12 6 .2 mg/kg相当于 1/2 ED50 ) ,递增剂量为 6 0 mg/kg,每隔 2代改为12 6 .2 mg/kg加强 1次。第 14、30、4 4及第 6 0代抗性指数 I50 )逐渐上升 ,分别为 4 .0 1、10 .11、16 .0 2及 18.93;至第76代 ,抗性减弱 ,I50 为 14 .89;至第 10 8代 ,剂量达 886 2 .5 mg/kg,I50 仅为 10 .4 9。B线 ,是从 A线第 6 6代转种而来 ,此后每周给药 1次 ,剂量为 4 0 0 0 mg/kg,至第 4 0代 I50 为 2 7.4 5 ,抗药性明显增强。C线 ,是从 B线第 19代转种而来 ,此后每周给药 1次 ,剂量为 2 0 0 0 mg/kg,至第 15代 ,I50 为 17.4 1。　结论　已培育出具有中度抗药性的伯氏疟原虫青蒿素抗性系     

伯氏疟原虫ANKA株抗哌喹系小鼠模型免疫学分析

目的观察伯氏疟原虫(Plasmodium berghei,Pb)ANKA抗哌喹(PQR)系小鼠模型的免疫学特征方法64只昆明小鼠随机分为3组,A组和C组各16只,B组32只(其中16只用于观察存活天数)。A组B组小鼠分别经腹腔感染伯氏疟原虫ANKA株哌喹敏感系(PbPQS)和抗性系(PbPQR)红内期原虫1×10~7个(200μl血),C组(健康对照组)注射等量生理盐水。每组于感染后4、8、12和16d各取4只小鼠,取尾血制薄血膜镜检,计算红细胞原虫感染率(简称原虫率)。脱颈处死小鼠,无菌取脾制备脾淋巴细胞悬液,用CCK-8法测定各组小鼠脾淋巴细胞经刀豆球蛋白A(ConA)刺激后的增殖反应,用Griess法和ELISA分别测定脾淋巴细胞培养上清中N0含量和γ干扰素(IFN-γ)水平。另取10只昆明小鼠,每鼠腹腔接种PbPQR系原虫约1×10~7个,待原虫率上升后下降,典型的原虫转变为蓝染细胞时,腹腔感染PbPQS系原虫(1×10~6个)进行攻击感染,观察小鼠原虫率和小鼠存活情况。结果 A组小鼠平均存活(9.0±3.0)d,感染后6～12d原虫率均>50%,出现严重贫血。感染后16d,B组小鼠全部存活,原虫率为(26.66±2.54)%。A、B两组小鼠的脾淋巴细胞经Con A刺激后增殖显著,感染后12d,分别为0.65±0.08和0.86±0.20(P<0.01)。脾淋巴细胞培养上清中,N0含量随感染时间延长而上升,感染后12d,A、B和C组分别为(48.80+3.49)、(54.80±2.17)和(7.80±0.71)μmol/L,三者比较差异有统计学意义(P<0.01)、A组脾淋巴细胞培养上清中IFN-γ水平随感染时间延长而上升,感染后12d达到最高,为(752.20+39.49)pg/ml,B组于感染后8d升至峰值[(855.80±33.65)pg/ml],感染后12d降至(620.20±27.11)pg/ml;感染后8d和12d,A组和B组IFN-γ水平的差异有统计学意义(P<0.01)。用PbPQS系攻击感染PbPQR系小鼠模型后10d,原虫率为(2.44±2.07)%,随之逐渐消失,感染后40d未检出虫体,无小鼠死亡。结论伯氏疟原虫ANKA株哌喹抗性系感染小鼠的脾淋巴细胞增殖水平、NO水平和IFN-γ含量均显著高于PbANKA株PQS系感染小鼠,可诱导小鼠产生一定保护性免疫反应。     

Characterization of a differential immunoscreen epitope of Plasmodium falciparum using combinatorial agents

A differential serological screening of a lambdagt11 cDNA expression library has identified several clones, which react exclusively to sera samples from persons clinically immune to malaria but not to acute malaria patient sera. One such clone, IPf9, has a 315-bp cDNA insert, which was found to be conserved in different strains of the human and rodent malarial parasite Plasmodium falciparum and Plasmodium berghei, respectively. The induced expression product of IPf9 was used to generate polyclonal sera in rabbits. The IPf9 expression product was also screened with phage surface display combinatorial libraries to isolate reagents that specifically bound to the IPf9 product. The polyclonal antisera and the combinatorial reagents recognized a 50-kDa protein from P. falciparum, and a 53-kDa product from P. berghei. Immunofluorescence studies using asexual and sexual stages of P. falciparum showed the protein to be present within the parasite in each of the asexual and sexual stages. The combinatorial reagents showed a partial inhibition in the growth of P. falciparum in vitro. Mice infected with the P. berghei showed the presence of T-cells that exhibited lymphoproliferation when stimulated with the IPf9 protein. It is suggested that IPf9 protein is a conserved protein epitope, and may be relevant for a protective immune response to malaria.     

IL-12在抗伯氏疟原虫感染中的免疫佐剂作用

目的　探讨IL - 12在抗伯氏疟原虫感染中的免疫佐剂作用。方法　BALB/c小鼠分别皮下用抗原sAg、IL - 12、抗原sAg联合IL - 12或抗原sAg联合弗氏佐剂进行免疫 ,共免疫 3次 ,每次间隔 2wk ,末次免疫后 1wk以 5× 10 5个感染P berghei的RBC攻击感染 ,观察各组小鼠原虫血症变化及存活时间。攻击感染后 1wk收集各组小鼠血清 ,采用ELISA检测血清中IFN -γ、IL - 4、IL - 10及IgG水平。结果　抗原sAg联合IL - 12免疫可较其它各免疫组及未免疫对照组显著延长小鼠存活时间 ,且全部小鼠在原虫血症达 5 0 %时开始死亡 ;而单独抗原sAg、单独IL - 12或抗原sAg联合弗氏佐剂免疫与未免疫比较 ,对小鼠原虫血症及存活时间均无明显影响 ,且半数以上小鼠均在原虫血症小于 2 5 %时死亡。抗原联合IL - 12免疫组小鼠血清中IFN -γ及IgG水平较单独抗原sAg、单独IL - 12及未免疫组显著升高。 结论　结果表明 ,IL - 12与sAg抗原共同免疫小鼠可诱导对P berghei攻击感染的部分抵抗力 ,具有一定的免疫佐剂活性。     

Expression of the Plasmodium berghei ookinete protein Pbs21 in a baculovirus-insect cell system produces an efficient transmission blocking immunogen

A surface protein of Plasmodium berghei ookinetes, Pbs21, was expressed in a baculovirus-insect cell system in cell culture and in Heliothis virescens larvae. Groups of BALB/c mice received two intraperitoneal inoculations of either i) Tris-buffer or homogenized H. virescens larvae infected with wild-type baculovirus; ii) enriched, homogenized ookinetes, or Hi) homogenizedH. virescens larvae expressing recombinant Pbs21 (rPbs21). All animals immunized with ookinetes or with rPbs21 had high litres of antibodies (IgG isotype) that bound to native Pbs21. The large majority of antibodies in immune sera of both groups recognized the antigen under non-reducing but not under reducing conditions. The predominant IgG-sub-classes in mice immunized with ookinetes was IgGl and in mice immunized with rPbs21, the subclasses were IgGl and IgG2a. Immunization with rPbs21 reduced the infec-tivity of P. berghei to mosquitoes by 91% compared to a 99% reduction following immunization with ookinetes. This preliminary data indicate that rPbs21 expressed in this eukaryotic system induces a transmission-blocking immunity which is more effective than that achieved using rPbsll expressed in Escherichia coli (Matsuoka et al. 1994).     

Inhibition of the growth of Plasmodium falciparum and Plasmodium berghei in vitro by an extract of Cochlospermum angolense (Welw.).

An extract of Cochlospermum angolense (Welw.) is used in the traditional medicine of Angola for the therapy of icterus and for the prophylaxis of malaria. From the roots of this plant red crystalline substances have been isolated and tested for their effect on Plasmodium falciparum in vitro and on the DNA and protein synthesis of Plasmodium berghei. The multiplication of P. falciparum was decreased to 50% of the control in the presence of 10 μg/ml extracted material and there was a total inhibition at a concentration of 50 μ/ml. If mice erythrocytes infected by P. berghei were incubated for 6 h with 25 μg/ml of the extract DNA synthesis was depressed to nearly background level. And, even more important, this effect could be demonstrated immediately. On the contrary, protein synthesis continued for at least 90 min at a reduced rate and stopped then. The results obtained show the direct antiparasitic effect of the substances extracted from C. angolense. The activity seems to be directed against DNA synthesis.     

伯氏疟原虫静息巯基氧化酶的生物信息学分析和体外酶活检测

目的克隆、表达伯氏疟原虫静息巯基氧化酶(PbQSOX)基因,纯化重组Pb QSOX蛋白(rPbQSOX),并对其生物信息学特点和酶活性进行分析。方法分别采用BLAST、SMART、ClustalW对P QSOX蛋白的信号肽、蛋白结构域、活性位点、同源性进行分析;通过BLAST和MAGA5构建PbQSOX的系统进化树;应用SWISS-MODEL对PbQSOX蛋白的三级结构进行预测。BALB/c雌性小鼠经腹腔感染伯氏疟原虫(1×10^7/鼠),于感染后第4天提取疟原虫基因组DNA。PCR扩增PbQSOX基因,经测序正确后,将目的片段连接至原核表达载体pET30a(+),构建重组质粒pET30a(+)-PbQSOX。将鉴定正确的重组质粒转化至大肠埃希菌BL21中,经异丙基-β-D-硫代半乳糖苷(IPTG)诱导后,取菌液进行十二烷基硫酸钠-聚丙烯酰胺凝胶电泳(SDS-PAGE)和蛋白质免疫印迹(Western blotting)分析;应用镍氨三乙酸琼脂糖柱纯化可溶性的rPbQSOX,并以三(2-羧乙基)膦(TCEP)或二硫苏糖醇(DTT)为酶反应底物分析rPbQSOX的酶活性。P QSOX大部分其他物种的同源基因。多序列蛋白比对与蛋白结构域分析结果显示,PbQSOX蛋白含1个信号肽,存在Trx1、ψErv和Erv/ALR结构域,但完全缺失了Trx2结构域。Pb QSOX蛋白含3个关键的CXXC活化基序(C为半胱氨酸Cys,X为任意氨基酸),即CPAC、CRNC和CNYC;采用MAGA5邻接法构建的系统进化树显示,PbQSOX与约氏疟原虫QSOX(PyQSOX)的亲缘关系最近;SWISS-MODEL同源建模法分析结果显示,用已知的布氏锥虫QSOX(TbQSOX)可预测PbQSOX蛋白的三级结构。PCR扩增PbQSOX基因,获得1486 bp目的条带,经测序为PbQSOX基因序列;pET30a(+)-PbQSOX质粒经NdeⅠ、HindⅢ双酶切与测序鉴定正确。SDS-PAGE和Western bloting分析结果显示,rPbQSOX重组蛋白主要以可溶形式表达,相对分子质量约59000。纯化后的rPbQSOX对TCEP的催化活性为0.84±0.18,DTT的催化活性为0.78±0.14(P<0.01)。结论PbQSOX蛋白为单Trx1结构域的伯氏疟原虫静息巯基氧化酶,构建、表达的rPbQSOX蛋白为可溶性蛋白,具有一定的静息巯基氧化酶催化活性。     

伯氏疟原虫对小鼠脾B细胞和自然杀伤细胞及其表面分子的影响

为探讨伯氏疟原虫对小鼠脾B细胞和自然杀伤(NK)细胞及其表面分子的影响,将10只雌性C57BL/6小鼠随机分为健康对照组和感染组,每组5只。感染组小鼠经尾静脉注射伯氏疟原虫(106个/鼠)进行感染,健康对照组注射等量生理盐水。感染后6 d,取小鼠脾,制备单细胞悬液,采用流式细胞术检测小鼠B细胞和NK细胞的含量及其表面分子CD62L、CXCR3、CD69的表达水平。结果显示,感染组小鼠脾B细胞百分比含量为(79.2±3.6)%,高于健康对照组的(54.3±4.4)%(P<0.01);感染组脾NK细胞百分比为(2.2±0.7)%,低于健康对照组的(4.6±0.8)%(P<0.01)。CD62L在感染组B细胞中的百分比为(77.7±4.4)%,高于健康对照组的(72.8±7.1)%,但二者差异无统计学意义(P>0.05);CD62L在感染组NK细胞中的百分比为(61.9±4.8)%,低于健康对照组的(86.6±4.2)%(P<0.01)。CXCR3在感染组B细胞中的百分比为(4.1±0.1)%,高于健康对照组的(3.0±0.2)%(P<0.01);CXCR3在感染组NK细胞中的百分比为(2.1±0.9)%,低于健康对照组的(2.3±0.4)%,但二者差异无统计学意义(P>0.05)。CD69在感染组B细胞和NK细胞中的百分比分别为(54.3±4.7)%、(22.2±1.6)%,均高于健康对照组的(1.9±0.4)%、(1.3±0.3)%(P<0.01)。提示感染疟原虫的小鼠可能通过增加B细胞的数量以及上调其表面分子CXCR3和CD69及NK细胞表面分子CD69的表达水平发挥抗疟作用。     

The primary antibody response of malaria patients to Plasmodium falciparum sexual stage antigens which are potential transmission blocking vaccine candidates

Summary Thirty serum samples collected from adult patients attending the Hospital for Tropical Diseases, London, with P. falciparum malaria, were studied. Sera were screened by indirect immunofluorescence for anti-gametocyte antibodies. Twelve of the serum samples taken from 14 patients with primary infections were found to have both IgM and IgG antibodies to gametocyte antigens and total Ig titres comparable with those of patients who had had previous malaria attacks. Sera of individuals from hyperendemic areas have been found to immunoprecipitate the 230 and 48/45 kD gametocyte surface antigens which are known targets of transmission blocking antibodies. To investigate the epitope specificity of the serum samples from our adult patients, competitive ELISAs with 3 monoclonal antibodies (MAbs) that block transmission and recognize different epitopes on the 48/45 Kd antigen, were carried out. Specific antibodies for these epitopes were found in 60% of the sera while nearly a third were able to inhibit the binding of at least two MAbs.     

Inheritance of post-vaccinal resistance against Plasmodium berghei infection in mice

The protective effect of specific vaccination against Plasmodium berghei (P. berghei) was compared in terms of survival percentage in DBA/2, C3H, outbred albino mice and in two lines of mice produced by selective breeding for either high or low antibody responsiveness to sheep erythrocyte (H and L lines respectively). The efficacy of induced protection varies according to genetic constitution. It is very strong in H line and albino mice, intermediate in DBA/2 and very weak in L line and C3H. The inheritance of post-vaccinal resistance to infection was studied in F1 hybrids and backcrosses between C3H and the other lines. The control was polygenic in all cases. The dominance of the characteristic depends on the strain combination. On the whole the results suggest the non-identity of the genes controlling protection in the various lines. The lack of a quantitative parameter for a more precise genetic analysis of protective immunity in inbred lines is stressed, since both anti-P. berghei antibody production and parasitaemia proved to be unreliable.