Caracterização imunológica da formulação vacinal baseada em VLP (Virus Like Particle) da Proteína Circumsporozoíta de Plasmodium vivax / Immunological characterization of the VLP (Virus Like Particle) vaccine formulation fused to Circumsporozoite Protein of Plasmodium vivax

O Plasmodium vivax é a espécie mais comum de parasita causador da malária humana encontrada fora da África, com maior endemicidade na Ásia, América Central e do Sul e Oceania. Embora o Plasmodium falciparum cause a maioria do número de mortes, o P. vivax pode levar à malária grave e resultar em morbimortalidade significativa. O desenvolvimento de uma vacina protetora será um passo importante para a eliminação da malária. Recentemente, uma formulação contendo as três variantes alélicas da proteína circumsporozoíta de P. vivax (PvCSP - All epitopes) induziu proteção parcial em camundongos após desafio com esporozoíto híbrido Plasmodium berghei (Pb), no qual as repetições centrais do PbCSP foram substituídas por repetições PvCSP-VK210 (esporozoítos Pb/Pv). No presente estudo, a proteína quimérica PvCSP contendo as variantes alélicas (VK210, VK247 e P. vivax-like) fusionadas com a proteína de nucleocapsídeo do vírus da caxumba (formando partículas semelhantes a nucleocapsídeos ou do inglês, NLP - Núcleo Like Particles) na ausência (NLP-CSPR) ou na presença do domínio C-terminal (CT) conservado da PvCSP (NLP-CSPCT). Para a realização do estudo selecionamos os adjuvantes Poly (I:C), um RNA sintético de dupla fita, agonista do receptor Toll do tipo 3 (TLR3) ou o adjuvante Montanide ISA 720, uma emulação óleo em agua. Para obter uma forte resposta imune, a levedura Pichia pastoris foi usada para expressar as proteínas recombinantes na forma de NLPs. Camundongos foram imunizados com cada uma das proteínas recombinantes em combinação com os adjuvantes citados. Embora ambas as NLPs tenham sido capazes de gerar uma forte resposta imune, com altos níveis de títulos e longevidade, apenas a formulação contendo a proteína NLP-CSPCT na presença do adjuvante Poly (I:C) foi selecionada para ser explorada em experimentos futuros. Esta proteína em combinação com o adjuvante Poly (I:C) induziu alta frequência de células secretoras de anticorpos específicas para o antígeno homólogo nos dias 5 e 30, no baço e na medula óssea, respectivamente. Altos títulos de IgG contra as 3 variantes de PvCSP foram detectados nos soros. Posteriormente camundongos imunizados com NLP-CSPCT foram desafiados com esporozoítos Pb/Pv e a parasitemia no 5º dia demonstrou proteção estéril em 30% dos camundongos desafiados. Portanto, a formulação vacinal gerada neste estudo tem potencial para ser explorada no desenvolvimento de uma vacina universal contra a malária causada por P. vivax

Plasmodium vivax is the most common species of human malaria parasite found outside Africa, with high endemicity in Asia, Central and South America, and Oceania. Although Plasmodium falciparum causes the majority of deaths, P. vivax can lead to severe malaria and result in significant morbidity and mortality. The development of a protective vaccine will be a major step toward malaria elimination. Recently, a formulation containing the three allelic variants of the P. vivax circumsporozoite protein (PvCSP--All epitopes) showed partial protection in mice after a challenge with the hybrid Plasmodium berghei (Pb) sporozoite, in which the PbCSP central repeats were replaced by the VK210 PvCSP repeats (Pb/Pv sporozoite). In the present study, the chimeric PvCSP allelic variants (VK210, VK247, and P. vivax-like) were fused with the mumps virus nucleocapsid protein (assembling into nucleo like particles - NLP) in the absence (NLP-CSPR) or presence of the conserved C-terminal (CT) domain of PvCSP (NLP-CSPCT). To carry out the study, we selected the adjuvants Poly (I:C), a synthetic double-stranded RNA, Toll-like receptor 3 (TLR3) agonist or Montanide ISA 720 adjuvant, an oil-water emulation. To elicit stronger immune response, Pichia pastoris yeast was used to produce the NLPs. Mice were immunized with each recombinant protein in combination with above. Although both NLPs were able to generate stronger immune response, with high antibodies titer levels and longevity, formulation containing NLP-CSPCT in the presence of Poly (I:C) was selected to be explored in future experiments. NLP-CSPCT with Poly (I:C) adjuvant presented a high frequency of antigen-specific antibody-secreting cells (ASCs) on days 5 and 30, respectively, in the spleen and bone marrow. Moreover, high IgG titers against all PvCSP variants were detected in the sera. Later, immunized mice with NLP-CSPCT were challenged with Pb/Pv sporozoites. Sterile protection was observed in 30% of the challenged mice. Therefore, this vaccine formulation use has the potential to be a good candidate for the development of a universal vaccine against P. vivax 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 IgG, IgG1 and IgG2a levels. Spleen of mice was obtained for preparation of splenic mononuclear cell and the cytokine IL-4 and IFN-γ levels 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 IgG in DNA vaccine immunity group significantly increased (P < 0.01), and IgG1 and IgG2a all increased (P < 0.01). IL-4, IFN-γ content 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 erythrocyte-stage 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 multi-stage combined vaccine components of the life-cycle of plasmodium) is necessary.

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 IgG, IgG1 and IgG2a levels. Spleen of mice was obtained for preparation of splenic mononuclear cell and the cytokine IL-4 and IFN-γ levels 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 IgG in DNA vaccine immunity group significantly increased (P < 0.01), and IgG1 and IgG2a all increased (P < 0.01). IL-4, IFN-γ content 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 erythrocyte-stage 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 multi-stage combined vaccine components of the life-cycle of plasmodium) is necessary.

A detail comprehensive review on vaccines.

A vaccine is a biological preparation which enhances the immunity to a particular disease. A vaccine typically contains an agent that resembles a disease-causing microorganism and is often made from weakened or killed forms of the microbe, its toxins or one of its surface proteins. This agent stimulates the body immune system to recognize the agent as foreign, destroy it, and keep a record of it, so that the immune system can more easily recognize and destroy any of these microorganisms that it later encounters. Vaccines may be therapeutic (means vaccines against cancer are also being investigated; see cancer vaccine) or prophylactic (means to prevent or ameliorate the effects of a future infection by any natural or "wild" pathogen), The term vaccine elucidate by Edward Jenner's 1796 use of cow pox (Latin variola vaccinia, taken from the Latin vaccīn-us, from vacca, cow), to inoculate humans, providing them protection against smallpox.1 Vaccines do not guarantee complete protection from a disease.2 This may be due to a lowered immunity in general (diabetes, steroid, HIV infection,age) or because the host's immune system does not have a B cell capable of generating antibodies to that antigen. In this case, the infection will be less severe and heal faster.3 Adjuvants are typically used to boost immune response. Most often aluminium adjuvants are used, but adjuvants like squalene are also used in some vaccines and more vaccines with squalene and phosphate adjuvants are being tested. Larger doses are used in some cases for older people (50–75 years).

Sequence polymorphisms in Pvs48/45 and Pvs47 gametocyte and gamete surface proteins in Plasmodium vivax isolated in Korea

Nucleotide sequence analyses of the Pvs48/45 and Pvs47 genes were conducted in 46 malaria patients from the Republic of Korea (ROK) (n = 40) and returning travellers from India (n = 3) and Indonesia (n = 3). The domain structures, which were based on cysteine residue position and secondary protein structure, were similar between Plasmodium vivax (Pvs48/45 and Pvs47) and Plasmodium falciparum (Pfs48/45 and Pfs47). In comparison to the Sal-1 reference strain (Pvs48/45, PVX_083235 and Pvs47, PVX_083240), Korean isolates revealed seven polymorphisms (E35K, H211N, K250N, D335Y, A376T, I380T and K418R) in Pvs48/45. These isolates could be divided into five haplotypes with the two major types having frequencies of 47.5% and 20%, respectivelfy. In Pvs47, 10 polymorphisms (F22L, F24L, K27E, D31N, V230I, M233I, E240D, I262T, I273M and A373V) were found and they could be divided into four haplotypes with one major type having a frequency of 75%. The Pvs48/45 isolates from India showed a unique amino acid substitution site (K26R). Compared to the Sal-1 and ROK isolates, the Pvs47 isolates from travellers returning from India and Indonesia had amino acid substitutions (S57T and I262K). The current data may contribute to the development of the malaria transmission-blocking vaccine in future clinical trials.

Evaluation of host humoral antibody production against Plasmodium falciparum recombinant circumsporozoite antigen in Nigerian children.

Background & objectives: The challenge of malaria and efforts targeted at developing malaria vaccines triggered this study on the reactivity of IgG and its subclasses in the test serum specific to CSP. This work was directed at assessing the influence of age and gender on host humoral antibody against Plasmodium falciparum recombinant circumsporozoite antigen in Nigerian children. Methods: In all, 67 serum samples (>10,000 parasites/μl of blood) collected from malaria-infected children at the University College Hospital, Ibadan during the transmission season were analyzed by ELISA. Results: The mean absorbance values of IgG subclasses reactive against P. falciparum CSP appeared to be agedependent and ranged from 0.01 for IgG4 in younger children to 0.95 for IgG3 in older children. The sixty-seven subjects investigated in this study had significantly higher mean IgG1 and IgG3 than the uninfected controls (p <0.01). This follows the order IgG3 >IgG1>IgG2>IgG4 which confirmed the prevalence of the cytophilic antibodies (IgG1 and IgG3) in 65% of the malaria infected children over the non-cytophilic subclasses (IgG2 and IgG4). Similarly, there was low production of IgG4 and IgG2 levels in 35% of the subjects compared with control. IgG was detected in the serum of North American Subjects (NAS) which served as negative control for CSP-specific IgG subclasses. Although the NAS titre was lower than that of the malaria subjects in Nigeria, its IgG2 was, however, higher (0.16) than that of other subclasses. The mean absorbance values of total serum IgG subclass were higher than those of IgG subclasses specific to P. falciparum circumsporozoite antigen. The mean absorbance values of the total serum IgG subclass follows the order IgG2>IgG1>IgG4>IgG3. Interpretation & conclusion: Age and gender-dependent correlations of results suggest that acquired immunity could play a significant role in protection from malaria. Antibody levels are higher in male than female children of the same age group. Antibody levels also increase with age in both the male and female children.

Current scenario of malaria vaccine.

Malaria is one of the deadliest infectious diseases that affects millions of people worldwide including India. As an addition to chemoprophylaxis and other antimalarial interventions malaria vaccine is under extensive research since decades. The vaccine development is more difficult to predict than drug development and presents a unique challenge as already there has been no vaccine effective against a parasite. Effective malaria vaccine could help eliminate and eradicate malaria; there are currently 63 vaccine candidates, 41 in preclinical and clinical stages of development. Vaccines are being designed to target pre-erythrocytic stages, erythrocytic stage or the sexual stages of Plasmodium taken up by a feeding mosquito, or the multiple stages. Two vaccines in preclinical and clinical development target P. falciparum; and the most advanced candidate is the pre-erythrocytic vaccine RTS,S which is in phase-III clinical trials. It is likely that world’s first malaria vaccine will be available by 2015 at the country level. More efficacious second generation malaria vaccines are on the way to development. Safety, efficacy, cost and provision of the vaccine to all communities are major concerns in malaria vaccine issue.

The research on the immunogenicity and in vitro protective efficacy of a polyepitope Plasmodium falciparum candidate vaccine, M.RCAg-1 formulation with different adjuvants / 中华微生物学和免疫学杂志

ObjectiveTo detect the difference of cytokines and antibodies productions by immunologic system from mice and rabbits vaccinated with the M.RCAg-1 chimeric protein,expressed in E.coli,formulation with different adjuvants,including Freund's adjuvant and three clinically acceptable adjuvants,namely,Al(OH)3,Montanide ISA720 and Montanide ISA51.MethodsSix weeks female BALB/c mice were vaccinated with recombinant protein formulated with different adjuvants through intranasal.Serum were collected to detect specific antibodies of M.RCAg-1 and individual Epitope by ELISA ; natural parasite antigen was recognized by indirect immunofluorescence assay; mouse specific T lymphocyte activation was detected by enzyme-linked immunosorbent spot test (ELISPOT) ; Affinity assay between protein and immune IgG of rabbits with the biosensor,and the growth of Plasmodiumfalciparum in vitro to evaluate by growth inhibition assay(GIA).ResultsDifferent formulation can induce different levels of antibody titers,the effection of ISA51 adjuvant was most closely with Freund's adjuvant,and can induce a higher specific antibody of 11 epitopes within proteins,can effectively stimulate cellular immune response based on the IFN-γ,to avidity Montanide ISA51 adjuvant immune antibodies and M.RCAg-1 protein affinity than the other two adjuvants;and Montanide ISA720 adjuvants and Al (OH)3 adjuvant group in mice can't induce a significant IFN-γresponse(P＞0.05).On avidity assay,the Montanide ISA51 formulation group was better than the other two adjuvants; and Montanide ISA720 and Al (OH)3 adjuvant formulation group can't induce a significant IFN-γresponse in mice(P＞0.05) ; the inhibition rates were 60% and 100% in 3D7 and Dd2 Plasmodium falciparum at a concentration of 2 mg/ml IgG by Montanide ISA51 formulated protein,and IgG of Al( OH)3 formulation could not effectively inhibit the in vitro growth of Plasmodium falciparum( 10% ),while IgG of Montanide ISA720 formulation could not inhibit growth of parasite in vitro.ConclusionBy comparing three clinically acceptable adjuvants and Freund's adjuvant in BALB/c mice and New Zealand rabbit,Montanide ISA51 adjuvants can be acceptable formulated M.RCAg-1 protein induced humoral and cellular immune responses,can be used as one of the candidate adjuvants.

Plasmodium vivax thrombospondin related adhesion protein: immunogenicity and protective efficacy in rodents and Aotus monkeys

The thrombospondin related adhesion protein (TRAP) is a malaria pre-erythrocytic antigen currently pursued as malaria vaccine candidate to Plasmodium falciparum. In this study, a long synthetic peptide (LSP) representing a P. vivax TRAP fragment involved in hepatocyte invasion was formulated in both Freund and Montanide ISA 720 adjutants and administered by IM and subcutaneous routes to BALB/c mice and Aotus monkeys. We measured specific humoral immune responses in both animal species and performed a sporozoite challenge in Aotus monkeys to assess the protective efficacy of the vaccine. After immunization both mice and Aotus seroconverted as shown by ELISA, and the specific anti-peptide antibodies cross reacted with the parasite in IFAT assays. Only two out of six immunized animals became infected after P. vivax sporozoite challenge as compared with four out of six animals from the control group. These results suggest that this TRAP fragment has protective potential against P. vivax malaria and deserves further studies as vaccine candidate.

High level expression and purification of 1 C-terminal fragment of merozoite surface protein of Plasmodium falciparum in Pichia pastoris / 中国人兽共患病学报

To obtain an ideal recombinant C-terminal fragment of the merozoite surface protein of Plasmodium falciparum in the Pichia pastoris expression system, the major surface protein-119 (MSP-119) gene sequence bearing the 6-his gene was inserted into expression vector pPIC9k and the target gene was transformed to the susceptible yeast cells GS115 by using electroporation. The multiple inserts were screened and the successfully expressed MSP-119 protein with the relative molecular weight of 12kDa in the supernatants of cell cultures could be detected by SDS-PAGE. Meanwhile, Western blot analysis also demonstrated that this protein reacted with mouse anti-MSP-119 monoclonal antibody, and the expression level of MSP-119 was more than 1.0 g/L. It is concluded that this recombinant protein expressed in the Pichia pastoris expression system resembles the native proteins existed.

Preparation and Characterization of Monoclonal Antibody Specific to PfCP-2.9 Chimeric Protein of Plasmodium falciparum / 中国寄生虫学与寄生虫病杂志

Objective To prepare and characterize monoclonal antibody against a malaria vaccine candidate, PfCP-2.9 chimeric protein of Plasmodium falciparum. Methods BALB/c mice were immunized with PfCP-2.9,and the spleen cells were used for fusion with SP2/0 cells. The monoclonal antibodies were analyzed by ELISA,Western blotting as well as growth inhibition assay. Result A monoclonal antibody was obtained. It interacted with the PfCP-2.9 recombinant protein by ELISA and Western blotting. The interaction of the monoclonal antibody with the protein was reduction-sensitive,indicating that the antibody recognized a conformational epitope. Moreover,the antibody also recognized the cultured parasites of P.falciparum by indirect immunofluorescent antibody test(IFA). When tested by growth inhibition assay,the antibody significantly inhibited parasite growth in vitro of 56% inhibition rate at the antibody concentration of 0.3 mg/ml. Conclusion A monoclonal antibody against PfCP-2.9 malaria vaccine candidate has been obtained,which recognizes a conformational epitope of the protein and natural protein.