Characterization of Caveola-Vesicle Complexes (CVCs) Protein, PHIST/CVC-81₉₅ in Plasmodium vivax

Plasmodium vivax produces numerous caveola-vesicle complex (CVC) structures beneath the membrane of infected erythrocytes. Recently, a member helical interspersed subtelomeric (PHIST) superfamily protein, PcyPHIST/CVC-81₉₅, was identified as CVCs-associated protein in Plasmodium cynomolgi and essential for survival of this parasite. Very little information has been documented to date about PHIST/CVC-81₉₅ protein in P. vivax. In this study, the recombinant PvPHIST/CVC-81₉₅ N and C termini were expressed, and immunoreactivity was assessed using confirmed vivax malaria patients sera by protein microarray. The subcellular localization of PvPHIST/CVC-81₉₅ N and C termini in blood stage parasites was also determined. The antigenicity of recombinant PvPHIST/CVC-81₉₅ N and C terminal proteins were analyzed by using serum samples from the Republic of Korea. The results showed that immunoreactivities to these proteins had 61% and 43% sensitivity and 96.9% and 93.8% specificity, respectively. The N terminal of PvPHIST/CVC-81₉₅ which contains transmembrane domain and export motif (PEXEL; RxLxE/Q/D) produced CVCs location throughout the erythrocytic-stage parasites. However, no fluorescence was detected with antibodies against C terminal fragment of PvPHIST/CVC-81₉₅. These results suggest that the PvPHIST/CVC-81₉₅ is localized on the CVCs and may be immunogenic in natural infection of P. vivax.

Biochemical and immunological characterization of E. coli expressed 42 kDa fragment of Plasmodium vivax and P. cynomolgi bastianelli merozoite surface protein-1.

Plasmodium vivax is one of the most widely distributed human malaria parasites and due to drug-resistant strains, its incidence and prevalence has increased, thus an effective vaccine against the parasites is urgently needed. One of the major constraints in developing P. vivax vaccine is the lack of suitable in vivo models for testing the protective efficacy of the vaccine. P. vivax and P. cynomolgi bastianelli are the two closely related malaria parasites and share a similar clinical course of infection in their respective hosts. The merozoite surface protein-1 (MSP-1) of these parasites has found to be protective in a wide range of host-parasite systems. P. vivax MSP-1 is synthesized as 200 kDa polypeptide and processed just prior to merozoite release from the erythrocytes into smaller fragments. The C- terminal 42 kDa cleavage product of MSP-1 (MSP-1(42)) is present on the surface of merozoites and a major candidate for blood stage malaria vaccine. In the present study, we have biochemically and immunologically characterized the soluble and refolded 42 kDa fragment of MSP-1 of P. vivax (PvMSP-1(42)) and P. cynomolgi B (PcMSP-1(42)). SDS-PAGE analysis showed that both soluble and refolded E. coli expressed P. vivax and P. cynomolgi B MSP-1(42) proteins were homogenous in nature. The soluble and refolded MSP-1(42) antigens of both parasites showed high reactivity with protective monkey sera and conformation-specific monoclonal antibodies against P. cynomolgi B and P. vivax MSP-1(42) antigens. Immunization of BALB/c mice with these antigens resulted in the production of high titres of cross-reactive antibodies primarily against the conformational epitopes of MSP-1(42) protein. The immune sera from rhesus monkeys. immunized with soluble and refolded MSP-1(42) antigens of both parasites also showed high titered cross-reactive antibodies against MSP-1(42) conformational epitopes. These results suggested that the soluble and refolded forms of E. coli expressed P. vivax MSP-1(42) antigens were highly immunogenic and thus a viable candidate for vaccine studies.

Oxidoreductases in early gestational monkey placenta during maternal malarial infection: histochemical localisation.

BACKGROUND & OBJECTIVES: Early gestational malaria is more deleterious than late gestational infection. Still the pathophysiology of maternofoetal organ--the placenta in malaria remains almost unexplored during early gestation. Present study dealing with oxidoreductases in early gestational placenta during maternal malarial infection of Plasmodium cynomolgi bastianellii in rhesus monkeys was anticipated to provide a better insight into the functional impairment of this organ leading to foetal abnormalities. METHODS: Three control and four experimental monkeys (Macaca mulatta) were quarantined for one month prior to experimentation. Experimental monkeys at 2- 2 1/2 months of gestation were inoculated with P. cynomolgi bastianellii. On attaining first peak of parasitaemia the placentae were collected from anesthetised animals. The snap-frozen, cryostat sections were subjected to histochemical localisation for 3 (or 17) beta-hydroxysteroid dehydrogenase (beta-HSD) [3 (or 17) beta-hydroxysteroid: NAD (P+) oxidoreductase, EC 1.1.1.51 hydroxysteroid dehydrogenases] and NADPH-tetrazolium reductase [NADPH: (acceptor) oxidoreductase, EC 1.6.99.1 NADPH-TR]. Comparative microscopy of control and malaria infected placental sections was performed and analysed. RESULTS: A localised decrease in both the enzymes was observed in syncytiotrophoblast layer of malaria infected monkey placenta. The areas showing morphological damage of syncytiotrophoblast were also depicting gross reduction in NADPH-TR activity. INTERPRETATION & CONCLUSION: The altered enzymatic activities [3 (or 17) beta-HSD and NADPH-TR] in malaria infected early gestational monkey placenta have been discussed in the light of placental function. It could be concluded by present studies that these alterations would affect the cellular metabolism especially steroidogenesis and detoxification process which in turn would affect the normal development of the foetus as well as maintenance of gestation.

Hydrolytic enzyme activity in rhesus monkey placenta during early gestational malaria: histochemical studies.

BACKGROUND & OBJECTIVES: Early gestational malaria is found to be more fatal than late gestational infection but the pathophysiology of early gestational placenta, the maternofoetal organ responsible for maintenance of pregnancy, remains unexplored. Present study dealing with hydrolytic enzymes in early gestational placenta of rhesus monkeys during Plasmodium cynomolgi infection was anticipated to provide a better insight into the functional impairment of this organ during early gestational maternal malaria. METHODS: Experimental monkeys (Macaca multtta) at 2-2 1/2 months of pregnancy were inoculated with P. cynomolgi bastianelli. After attaining first peak of parasitaemia the animals were anesthetised and placentae were collected for histochemical studies. The snap-frozen, cryostat sections were subjected to histochemical reactions for acid phosphatase and alkaline phosphatase. RESULTS: The placental syncytiotrophoblast showed a loss in alkaline phosphatase activity, while the trophoblast layers and phagocytic cells of the maternal blood showed increased acid phosphatase activity during early gestational malarial infection. Morphological damage to the placental tissue whenever occurred was associated with altered Alk pase activity. INTERPRETATION & CONCLUSION: The altered distribution of Ac pase and Alk pase in malaria infected early gestational placenta has been discussed in the light of placental function. It could be concluded by present studies that these malaria induced changes in hydrolytic enzyme activities in monkey placenta have a direct bearing on functional and morphological integrity of the placental tissue. These changes are apparently responsible for early gestational foetal death and abortions as reported in literature.

Induction of protective immunity in rhesus monkey by inoculation with recombinant fusion protein of cholera toxin B subunit-multivalent epitopes of Plasmodium falciparum / 生物工程学报

Rhesus monkeys (5 in each group) were inoculated with recombinant fusion protein of cholera toxin B subunit and multi-valent epitopes of Plasmodium falciparum intranasal or intramuscular (i.m.). Immune-responses and protective effect were evaluated. The antibody titer (Geometry mean) against CTB reached 1:512 (intranasal) and 1:10000 (i.m.) 14 day after 3rd immunization, and antibodies against P. falciparum were also elucidated, the titers in i.m. group were also significantly higher than that in intranasal group. The monkeys were challenged with 1.25 x 10(8) sporozoites of P. cynomolgi, Patent infection was observed in all 5 monkeys in control group inoculated with PBS in 10 - 14 days after challenge. Patent infection was also observed in 5 animals inoculated via intranasal and 2 animals in intramuscular group 19th days after challenge, But the infection last only 4 days in 3 animals in intranasal group and 2 animals in intramuscular group. The results demonstrated that the vaccine candidate could induce protective immune-responses in rhesus monkey against the challenge of P. cynomolgi.

Histochemical changes in host tissues from Plasmodium cynomolgi B infected rhesus monkey (Macaca mulatta).

Plasmodium cynomolgi B has been used to infect the rhesus monkey to study the histochemical changes (lipid infiltration, glycogen, protein, DNA and RNA) in liver, kidney and spleen during early (exoerythrocytic) and late (chronic) stages of malarial infection. Infected liver showed significant lipid infiltration during exoerythrocytic and erythrocytic (acute phase) stage of infection. Kidney showed lipid deposition during acute phase of infection while spleen sections were negative for lipid depositions. As a result of malarial infection there was significant depletion of glycogen in liver during exoerythrocytic stage of infection. Glycogen content increased in liver and kidney during erythrocytic stage of infection. The spleen which is the main target of immunopathology in malaria showed no change in glycogen content. During exoerythrocytic phase host tissue organs showed no change in protein and nucleic acids while erythrocytic phase showed slightly increased proteins in liver and kidney. Nucleic acids became decreased in liver and spleen during erythrocytic phase of infection. The parasite used in this study has a defined prepatent period, can be cyclically passaged with ease and non fatal in nature.

Hydrolytic enzymes of rhesus placenta during Plasmodium cynomolgi infection: ultrastructural and biochemical studies.

Placenta in monkey demonstrated altered pathophysiology after P cynomolgi infection. The electronmicroscopic observations showed slight complete focal necrosis of the placental tissue, besides alterations in total protein, phosphatases and proteinases. These changes in cellular constituents of placenta during malaria infection may be responsible for malfunctioning of the organ and in turn, abnormal development of foetus.

Two-site pan-species monoclonal antibody ELISA for detection of blood stage malaria antigen.

A two-site pan-species monoclonal antibody sandwich ELISA (MAb-MAb ELISA) was developed to detect both Plasmodium vivax and P. falciparum antigens in whole blood impregnated on filter paper. In this assay, the plates were coated with pan-species MAb 3F9 and another pan-species MAb M26-32 conjugated with alkaline phosphatase was used for detection of bound antigen. The sensitivity of this assay was 5, 10 and 10 parasites per 10(6) erythrocytes for cultured P. falciparum, patient-derived P. vivax and P. falciparum, respectively. The coincidence rates for this assay were 93% (92/99) with healthy individuals and 93% (42/45) with microscopically confirmed vivax malaria cases. After two weeks treatment, 77.7% (14/18) of vivax malaria were still positive by this assay but with diminished level of reactivities [corrected].

Detection of circulating plasmodial antigens in human sera by sandwich ELISA with monoclonal antibodies.

Two monoclonal antibodies (MAbs), one produced against Plasmodium falciparum (PF-IG8) and the other against P. cynomolgi (PC-IE12) schizont antigens were used in a sandwich ELISA for the detection of circulating plasmodial antigens in sera of patients infected with either P. falciparum, P. vivax or P. malariae. The mean +/- SD optical density (OD) values for the normal control group using PF-108 and PC-1E12 were 0.351 +/- 0.036 and 0.205 +/- 0.044, respectively. Mean OD values for the three infected groups were found to be significantly higher than those of the normal control group for both MAbs. However, ELISA values for individual serum specimens did not correlate with the level of parasitemia in the infected blood. Using a cut-off point of mean OD +/- 3 SD of the normal control group as indicating a positive reading, the specificity of this assay with both MAbs was 100%. The sensitivity of the assay using PF-1G8 was 95% while that obtained with PC-1E12 was 98%.

Tissue schizontocidal effect of trifluoroacetyl primaquine in Plasmodium yoelii infected mice and Plasmodium cynomolgi infected monkeys.

Trifluoroacetyl primaquine oxalate (M8506) was compared with primaquine phosphate for tissue schizontocidal action in rodent and simian malaria. In Plasmodium yoelii sporozoites infected mice, the causal prophylactic effects of M8506 at 5, 10 and 20 mg(base)/kg were 56.7%, 87.2% and 100%, respectively, comparable to those of primaquine (54.4%, 90.8% and 100%). In P. cynomolgi sporozoites infected rhesus monkeys 4 dosage regimens of the two agents were compared for radical curative effect. On the first day of treatment pyronaridine phosphate 10 mg(base)/kg twice a day were intramuscularly injected to eliminate erythrocytic stages of P. cynomolgi. At the dosage of 3.0 mg(base)/kg/day x 3, both M8506 and primaquine radically cured the monkeys. At 0.75 mg/kg/day x 3, 12 of 13 (92.3%) monkeys cured by M8506, 5 of 9 (55.6%) cured by primaquine. At 1.5 and 0.375 mg/kg/day x 3, the radical curative effects of M8506 were also better than those of primaquine. Since the toxicity of M8506 was significantly milder in mice, rats and dogs than that of primaquine, M8506 has potential as a tissue schizontocide.

Susceptibility of bacillus thuringiensis-treated anopheles stephensi and anopheles gambiae to infection with plasmodium cynomolgi

An. Stephensi and An. Gambiae were treated as larvae with B. thuringiensis israelensis and then fed on monkeys infected with the malaria parasite, P. cynomolgi. The susceptibility of the mosquitos to P. Cynomolgi was evaluated by the presence of oocysts on the wall of the stomach. The data showed that the bacterial toxins did not consistently affect the susceptibility of the mosquitos to several strains of P. cynomolgi