Protective immunity of single and multi-antigen DNA vaccines against schistosomiasis

An Insight into the Potential Parasitological Effect of Schistosoma mansoni Antigens in Infected Mice: Prophylactic Role of Cercarial Antigen

Schistosomiasis is a multifactorial disease that includes environmental, behavioral, parasitic, vector, and host factors. This study aimed to assess the protective effect of single and polyvalent antigens from cercarial antigen preparations (CAPs), soluble worm antigen preparations (SWAPs), and soluble egg antigens (SEAs) which were used as candidate vaccines in an experimental model of Schistosoma mansoni-infected mice. The efficiency of the antigens was tested by determining their effects on fecal egg count, egg viability analysis, and tissue egg counts. Histological and morphometric analyses of granulomas in liver and intestine tissues were performed. In the present study, all immunized groups showed a significant reduction in the average fecal egg count and tissue egg load compared with infected mice. The most substantial reduction in fecal egg count was observed in the combined vaccinated group (23.23 ± 3.2). The group vaccinated with CAP before infection showed the highest reduction in tissue egg load (liver and intestine: 85.22 and 91.70%, respectively). Immunized animals showed a highly significant reduction in the numbers of hepatic granulomas compared with the infected non-immunized group. In conclusion, combining these different antigens (CAP, SWAP, and SEA) augments the protective immunity compared with other immunized groups.

Fasciola hepatica vaccine: we may not be there yet but we're on the right road

Major advances have been made in identifying potential vaccine molecules for the control of fasciolosis in livestock but we have yet to reach the level of efficacy required for commercialisation. The pathogenesis of fasciolosis is associated with liver damage that is inflicted by migrating and feeding immature flukes as well as host inflammatory immune responses to parasite-secreted molecules and tissue damage alarm signals. Immune suppression/modulation by the parasites prevents the development of protective immune responses as evidenced by the lack of immunity observed in naturally and experimentally infected animals. In our opinion, future efforts need to focus on understanding how parasites invade and penetrate the tissues of their hosts and how they potentiate and control the ensuing immune responses, particularly in the first days of infection. Emerging 'omics' data employed in an unbiased approach are helping us understand liver fluke biology and, in parallel with new immunological data, to identify molecules that are essential to parasite development and accessible to vaccine-induced immune responses.

Fasciola gigantica fatty acid binding protein (FABP) as a prophylactic agent against Schistosoma mansoni infection in CD1 mice

Although schistosomicidal drugs and other control measures exist, the advent of an efficacious vaccine remains the most potentially powerful means for controlling this disease. In this study, native fatty acid binding protein (FABP) from Fasciola gigantica was purified from the adult worm's crude extract by saturation with ammonium sulphate followed by separation on DEAE-Sephadex A-50 anion exchange chromatography and gel filtration using Sephacryl HR-100, respectively. CD1 mice were immunized with the purified, native F. gigantica FABP in Freund's adjuvant and challenged subcutaneously with 120 Schistosoma mansoni cercariae. Immunization of CD1 mice with F. gigantica FABP has induced heterologous protection against S. mansoni, evidenced by the significant reduction in mean worm burden (72.3%), liver and intestinal egg counts (81.3% and 80.8%, respectively), and hepatic granuloma counts (42%). Also, it elicited mixed IgG₁/IgG_2b immune responses with predominant IgG1 isotype, suggesting that native F. gigantica FABP is mediated by a mixed Th1/Th2 response. However, it failed to induce any significant differences in the oogram pattern or in the mean granuloma diameter. This indicated that native F. gigantica FABP could be a promising vaccine candidate against S. mansoni infection.

Construction and expression of DNA vaccine pIRES-Sj97-Sj14-Sj26 and its immunogenicity in mice

To find a new preventive strategy for the infection of Schistosoma japonica, plasmid pIRES-Sj97-Sj14-Sj26 that contains fatty binding protein (Sj14), GST (Sj26) and paramyocin (Sj97) that are expressed on the membrane, was constructed. RT-PCR was used to detect the expression of Sj14 mRNA, Sj26 mRNA and Sj97 mRNA in the Hela cells, the indirect immunofluorescent test was employed for the detection of the expression of trans-membrane Sj26 after the plasmid was transfected into Hela cells. Fifty BALB/c mice were randomly divided into 5 groups and pIRES-Sj97-Sj14-Sj26 plasmid DNA, pIRES-Sj14-Sj26 plasmid DNA, pIRES-Sj26 plasmid DNA, pIRES blank vector and normal saline were respectively injected into the quadriceps muscles of thigh. Eight weeks after the immunization the mice were killed and significantly higher level of IgG was detected in the pIRES-Sj97-Sj14-Sj26 group as compared with the pIRES blank vector, normal saline and pIRES-Sj26 groups (P<0.01) and the pIRES-Sj14-Sj26(P<0.05). Single splenocyte suspension was prepared to detected the level of IFN-gamma by ELISA and the lymphocyte stimulating index (SI) by MTT. SI was significantly higher of in the pIRES-Sj97-Sj14-Sj26 group than in other groups (P<0.01), while the IFN-gamma level was significantly higher the pIRES-Sj97-Sj14-Sj26 group than in pIRES blank vector and normal saline groups (P<0.01), but no significant differences were found when compared with pIRES-Sj14-Sj26 and pIRES-Sj26 groups. Flow cytometery showed that the percent-ages of CD4+ and CD8+ T cells were much higher in the pIRES-Sj97-Sj14-Sj26 group (P< 0.01, P<0.05). It was concluded that pIRES-Sj97-Sj14-Sj26 vaccine may induce stronger immune response in BALB/c mice.

Comparison of DNA vaccines producing HIV-1 Gag and LAMP/Gag chimera in rhesus macaques reveals antigen-specific T-cell responses with distinct phenotypes

Optimized DNA expression vectors encoding the native HIV-1 Gag or a fusion of Gag with the lysosomal membrane associated protein 1 (LAMP) were compared for immunogenicity upon intramuscular DNA delivery in rhesus macaques. Both vaccines elicited CD4(+) T-cell responses, but with significant differences in the phenotype of the Gag-specific cells: the native Gag induced CD4(+) responses with a phenotype of central memory-like T cells (CD28(+) CD45RA(-)), whereas the LAMP/Gag chimera induced CD4(+) responses with effector memory phenotype (CD28(-) CD45RA(-)). Antigen-specific T cells producing both IFN-gamma and TNFalpha were found in the animals receiving the native Gag, whereas the LAMP/Gag chimera induced humoral responses faster. These results demonstrate that modification of intracellular Gag trafficking results in the induction of distinct immune responses. Combinations of DNA vectors encoding both forms of antigen may be more potent in eliciting anti-HIV-1 immunity.

Forma pseudoneoplásica de esquistossomose pulmonar crônica sem hipertensão pulmonar

A esquistossomose é uma doença que, no Brasil, é causada pelo Schistosoma mansoni e transmitida através da água por moluscos do gênero Biomphalaria. Essa espécie ocorre na África, nas Antilhas e na América do Sul. O parasita, ao atingir a fase adulta de seu ciclo biológico no sistema vascular do homem, alcança as veias mesentéricas. Cada fêmea põe cerca de 400 ovos por dia, e estes, a partir da submucosa, chegam à luz intestinal. Há relatos de casos a respeito de ovos de S. mansoni nos pulmões de pacientes sem evidência de fibrose hepática. Relatamos um caso dessa forma atípica de apresentação da doença. O paciente apresentava dor torácica não-ventilatóriodependente, perda ponderal significativa e tosse seca. A TC de tórax mostrou uma tumoração irregular no lobo inferior esquerdo, mas somente a biópsia pulmonar evidenciou ovos de S. mansoni degenerados. O paciente não apresentava sinais clínicos de hipertensão pulmonar ou portal, as quais tampouco foram diagnosticadas através de exames.

Recent advances in vaccine research against schistosomiasis in Brazil

Schistosomiasis continues to be a significant public health problem in tropical countries such as Brazil. Even though drug treatment in endemic areas has been shown to be efficient for controlling morbidity, it does not reduce prevalence due to constant reinfections. Therefore, a long-term disease control strategy is needed combining mass chemotherapy with a protective vaccine. Although the field of vaccine development has experienced more failures than successes, encouraging results have been obtained in recent years using defined recombinant derived Schistosoma mansoni antigens. This article primarily reviews the progress in the development of a vaccine against S. mansoni in Brazil. We discuss here different forms of vaccine tested in Brazil in pre-clinical trials and immunologic studies performed with patients in endemic areas of schistosomiasis. Lastly, we reviewed the S. mansoni genomic projects developed in the country and the recent advances in the identification of new molecules with potential as vaccine targets.

Oral immunization with Salmonella harboring a Sm14-based DNA vaccine does not protect mice against Schistosoma mansoni infection

The protection against Schistosoma mansoni infection was evaluated in SWISS mice orally vaccinated with an attenuated strain of Salmonella carrying a Sm14-based DNA vaccine. Although this formulation was not able to afford a reduction in the worm burden, a non-antigen-specific decrease in schistosome-induced granulomatous reaction was verified in livers of mice that received Salmonella.

Experimental vaccines in animal models for schistosomiasis

Considerable morbidity and mortality results from the affliction of an estimated 200 million people worldwide by several species of schistosomes; 779 million are exposed to the disease in 74 different countries. Even though anti-parasitic drugs and other control measures, including public hygiene and snail control are available, the advent of an effective vaccine still remains the most potentially powerful means for the control of this disease. The putative vaccine could be administered to small children prior to the time when their contact with infected water is maximal, so as to prevent severe infection in the subsequent years. This review attempts to summarize the status of schistosome vaccine development with special emphasis on functionally important vaccine candidates. The importance of utilizing both murine and nonhuman primate models as a prerequisite for clinical trials is discussed.

Assessment of a DNA vaccine encoding an anchored-glycosylphosphatidylinositol tegumental antigen complexed to protamine sulphate on immunoprotection against murine schistosomiasis

Protamine sulphate/DNA complexes have been shown to protect DNA from DNase digestion in a lipid system for gene transfer. A DNA-based vaccine complexed to protamine sulphate was used to induce an immune response against Schistosoma mansoni anchored-glycosylphosphatidylinositol tegumental antigen in BALB/c mice. The protection elicited ranged from 33 to 44%. The spectrum of the elicited immune response induced by the vaccine formulation without protamine was characterized by a high level of IgG (IgG1> IgG2a). Protamine sulphate added to the DNA vaccine formulation retained the green fluorescent protein encoding-plasmid longer in muscle and spleen. The experiments in vivo showed that under protamine sulphate effect, the scope of protection remained unchanged, but a modulation in antibody production (IgG1= IgG2a) was observed.

Mycobacterial codon optimization of the gene encoding the Sm14 antigen of Schistosoma mansoni in recombinant Mycobacterium bovis Bacille Calmette-Guérin enhances protein expression but not protection against cercarial challenge in mice

A mycobacterial codon-optimized gene encoding the Sm14 antigen of Schistosoma mansoni was generated using oligonucleotide assembly. This synthetic gene enhanced approximately fourfold the protein expression level in recombinant Mycobacterium bovis Bacille Calmette-Guérin (rBCG) when compared to that obtained using the native gene in the same expression vector. Immunization of mice with rBCG expressing Sm14 via the synthetic gene induced specific cellular Th1-predominant immune responses, as determined by interferon-gamma production of Sm14-stimulated splenocytes, which were comparable to those recorded in animals immunized with an rBCG strain expressing the native gene. Administration of a single dose of the rBCG-Sm14 construct carrying the synthetic gene conferred protection against cercarial challenge in outbred Swiss mice, at a level equivalent to those provided by either a single dose of rBCG expressing the native gene or three doses of Escherichia coli-derived recombinant Sm14. Our data demonstrated that despite improving the level of antigen expression, the codon optimization strategy did not result in enhanced immunity or protection against cercarial S. mansoni challenge.

Invertebrate Muscles: Muscle Specific Genes and Proteins

This is the first of a projected series of canonic reviews covering all invertebrate muscle literature prior to 2005 and covers muscle genes and proteins except those involved in excitation-contraction coupling (e.g., the ryanodine receptor) and those forming ligand- and voltage-dependent channels. Two themes are of primary importance. The first is the evolutionary antiquity of muscle proteins. Actin, myosin, and tropomyosin (at least, the presence of other muscle proteins in these organisms has not been examined) exist in muscle-like cells in Radiata, and almost all muscle proteins are present across Bilateria, implying that the first Bilaterian had a complete, or near-complete, complement of present-day muscle proteins. The second is the extraordinary diversity of protein isoforms and genetic mechanisms for producing them. This rich diversity suggests that studying invertebrate muscle proteins and genes can be usefully applied to resolve phylogenetic relationships and to understand protein assembly coevolution. Fully achieving these goals, however, will require examination of a much broader range of species than has been heretofore performed.

Schistosomiasis--an unusual cause of ureteral obstruction: a case history and perspective

A male, 32 years of age, presented with dysuria and abdominal pain, but no gross hematuria. He emigrated three years earlier from Somalia, East Africa, and was currently employed as a poultry processor in a rural Wisconsin community. The patient denied any trauma, sexual activity, or family history of significant illness. Abdominal and genitourinary exams were normal with negative tests for gonococcus and chlamydia. Urinalysis demonstrated microhematuria. A urogram and retrograde pyelogram revealed a mildly dilated right ureter down to the ureterovesical junction. Cystoscopy showed punctate white lesions on the bladder urothelium. Ureteroscopy was used to biopsy abnormal tissue in the distal ureter and bladder. Biopsy tissue demonstrated deposits of Schistosoma haematobium eggs. No ova were seen in collected urine specimens. The patient was successfully treated with praziquantel and will be monitored for sequelae of the disease. Schistosomiasis (Bilharziasis) can be expected to be seen with increasing frequency in the United States with the continuing influx of immigrants and refugees, as well as the return of travelers and soldiers from endemic areas. While no intermediate snail host exists for the transmission of Schistosoma sp. in the United States, the continued importation of exotic animals including snails from Africa, as well as the ability of schistosomes to shift host species warrants concern. Additionally, increasing disease associated with non-human bird schistosomes of the same genus seen in the midwestern United States is occurring throughout Europe. One should be aware that praziquantel may not always be available or effective in the treatment of schistosomiasis. It behooves the practicing clinician to remain updated on the status of this widespread zoonosis.

Induction of protective immunity against Schistosoma mansoni via DNA priming and boosting with the large subunit of calpain (Sm-p80): adjuvant effects of granulocyte-macrophage colony-stimulating factor and interleukin-4

Considerable morbidity and mortality result from schistosomiasis, an affliction affecting an estimated 200 million people. Although schistosomicidal drugs and other control measures (including public hygiene and snail control) exist, the advent of an efficacious vaccine remains the most potentially powerful means for controlling this disease. We have targeted a vaccine candidate (large subunit of calpain, Sm-p80) because of its consistent immunogenicity, protective potential, and integral role in surface membrane biogenesis of schistosomes. Since surface membrane renewal appears to be one of the major phenomena employed by schistosomes to evade the host's immune system; an immune response directed against Sm-p80 should render the parasite susceptible to immune clearance from the host by both providing a focus of attack and by potentially impairing the membrane repair process. In the present study, we have employed DNA immunization protocols using Sm-p80 with plasmids encoding granulocyte-macrophage colony-stimulating factor (GM-CSF) and interleukin-4 (IL-4). Sm-p80 by itself provided 39% protection (P = < or =0.0001) against challenge infection in C57BL/6 mice. This protection was increased to 44% (P = < or =0.0001) when the plasmid encoding GM-CSF was coadministered with Sm-p80 DNA. Coinjection of plasmid DNA encoding IL-4 with Sm-p80 DNA yielded a protection level of 42% (P = < or =0.0001). Statistically, the protection conferred by including GM-CSF, but not IL-4, was significantly greater than that when only Sm-p80 was used. Sm-p80 DNA by itself elicited strong responses that include IgG2A and IgG2B antibody isotypes. The introduction of GM-CSF DNA with Sm-p80 DNA led to distinct increases in total IgG and IgG1 titers, whereas the coadministration of IL-4 DNA with Sm-p80 DNA resulted in a slight elevation of IgG1 and IgG3 titers and in some reduction of IgG2A and IgG2B titers. Our data again indicate that Sm-p80 can be an excellent candidate for a schistosomiasis vaccine.

Enhancement of Sm-p80 (large subunit of calpain) induced protective immunity against Schistosoma mansoni through co-delivery of interleukin-2 and interleukin-12 in a DNA vaccine formulation

Schistosomiasis afflicts an estimated 200 million people in 76 countries and an additional 600 million people are at risk of acquiring this infection. Even though effective anthelmintic treatment and snail eradication control programs exist, the discovery of an effective vaccine still remains the most potentially powerful means of control for this disease. We have concentrated on a vaccine candidate (large subunit of calpain or Sm-p80) because of its potential in conferring protection against challenge infection and its pivotal role in surface membrane biogenesis of schistosomes. Since surface membrane renewal is a major phenomenon employed by hemohelminths to evade host immune system; an immune response directed against Sm-p80 should make the parasite prone to immune clearance from the host by both providing a well-targeted attack and by potentially inhibiting the surface membrane biogenesis process. In the present study, we have utilized DNA immunization protocols using Sm-p80 with plasmids encoding interleukin-2 (IL-2) and interleukin-12 (IL-12). Sm-p80 by itself provided a 39% protection (P</=0.0001) against challenge infection in C57BL/6 mice. This protection was increased to 57% (P</=0.0001) when plasmid encoding IL-2 was co-administered with Sm-p80 DNA. Co-injection of plasmid DNA encoding IL-12 with Sm-p80 DNA yielded a protection level of 45% (P</=0.0001). Statistically, the protection conferred by including IL-2 and IL-12 was significantly greater than when only the Sm-p80 was used. Sm-p80 DNA by itself elicited strong responses that includes IgG(2A) and IgG(2B) antibody isotypes. The introduction of IL-2 DNA with Sm-p80 DNA led to an increase in total IgG and IgG(2A) and IgG(2B) titres. Whereas co-administration of IL-12 DNA with Sm-p80 DNA resulted in the augmentation of only total IgG and IgG(2A). This data reinforces the potential of Sm-p80 as an excellent candidate for a schistosomiasis vaccine.