Schistosoma bovis: vaccine effects of a recombinant homologous glutathione S-transferase in sheep.

The economic importance of the trematode Schistosoma bovis in African livestock has justified the development of a specific vaccine. Administered preventively to sheep, rSb28GST--the only molecule cloned from S. bovis which has demonstrated vaccine potentialities in goats and cattle--reduced the mean worm burden in vaccinated animals and improved their health status compared with that of non-vaccinated controls. As in goats, but not in bovines, the fecundity of the settled worm pairs was not modified. Therefore, rSb28GST can be proposed as a universal tool for the prevention of clinical disorders engendered by the main schistosome species affecting domestic ruminants in the African continent.     

Progress towards a defined vaccine for schistosomiasis

During the last five years considerable progress has been made in studies o f schistosome immunology. Convergent views have emerged from the study of human and animal immunity which agree on the mechanisms required and the antigens involved. The reproducible induction of protective immunity with attenuated parasites and with antigenic preparations has now led to agreement that vaccination against schistosomiosis is on achievable goal. The evidence that led to this optimistic view was reviewed at a scientific working group on 'Prospects for Immunological Intervention in Human Schistosomiosis' held in Geneva in May 1986, under the auspices of the UNDP/World Bonk/WHO Special Programme.     

Cloning and partial nucleotide sequence of Schistosoma japonicum paramyosin: a potential vaccine candidate against schistosomiasis.

, , , and 1992. Cloning and partial nucleotide sequence of Schistosoma japonicum paramyosin: a potential vaccine candidate against schistosomiasis. International Journal for Parasitology 22: 1187–1191. Paramyosin from the blood fluke, Schistosoma mansoni, has shown promise as a vaccine candidate for schistosomiasis mansoni. Here we report the cloning and partial nucleotide sequence of a cDNA encoding paramyosin from the related human parasite, Schistosoma japonicum. Affinity purified antibodies to this clone recognized a S. japonicum antigen of molecular weight 97 kDa, equivalent to the reported size of S. mansoni paramyosin. Alignment of the cDNA sequence with that of S. mansoni paramyosin revealed 90% identity. Comparison of the predicted amino acid sequences revealed 95% identity. Although these two parasites differ in many characteristics, the substantial homology demonstrated here between S. mansoni and S. japonicum paramyosin could have important implications for the development of a S. japonicum vaccine.     

Schistosoma japonicum: The design and experimental evaluation of a multivalent DNA vaccine

The aim of this study was to construct and evaluate the immunity efficacy of the DNA multivalent vaccine pVIVO₂SjFABP-23. The vaccine was constructed and produced as follows. Forty BALB/c mice were divided into four groups designated pVIVO₂, pVIVO₂Sj23, pVIVO₂SjFABP and pVIVO₂SjFABP-23. Each mouse was immunized with 100 μg of the corresponding plasmid DNA by intramuscular injection. 28 days post-vaccination, the mice were challenged with S. japonicum cercariae, and the worm and egg burdens were determined 42 days post-challenge. Serum samples were collected from all the mice before and after vaccination and at the end of the experiment, and used for antibody detection. The IFN-γ and IL-4 levels were quantified in the supernatants of specifically stimulated spleen cells. The number of worms was reduced by 52%, 40% and 42% in mice respectively immunized with pVIVO₂SjFABP-23, pVIVO₂Sj23 or pVIVO₂SjFABP. A respective 61%, 38% and 39% egg reduction was determined relative to those mice that only received the empty pVIVO2 plasmid. pVIVO₂SjFABP-23 immunization increased IgG levels against SWAP and SEA. Increased IFN-γ levels were detected in the supernatant of specific stimulated spleen cells from mice immunized with the 3 different constructs. The multivalent DNA vaccine developed induced higher levels of protection than the two monovalent tested vaccines.     

Glycoprotein gp50-negative pseudorabies virus: a novel approach toward a nonspreading live herpesvirus vaccine.

Essential herpesvirus glycoproteins are involved in membrane fusion processes during infection, e.g., viral penetration and direct cell-to-cell transmission. We previously showed that the gD-homologous glycoprotein gp50 of pseudorabies virus (PrV) is essential for virus entry into target cells but proved to be dispensable for direct viral cell-to-cell spread in cell culture (I. Rauh and T. C. Mettenleiter, J. Virol. 65:5348-5456, 1991). For gp50-negative (gp50-) viruses, after phenotypic complementation necessary for primary infection, the only means of viral spread is by way of direct cell-to-cell transmission. In contrast, virus mutants lacking the essential gB-homologous glycoprotein gII after phenotypic complementation are only able to infect primary target cells and are blocked in further viral spread. To analyze how these in vitro phenotypes translate into virus replication in the animal, mice were infected intranasally with gp50- or gII- PrV mutants after prior phenotypic complementation by propagation on cell lines providing the essential glycoprotein in trans. Our results show that whereas the gII- mutants did not cause disease or any symptoms, gp50- mutants derived from two different PrV strains were fully virulent, with animals exhibiting severe symptoms ultimately leading to death. However, free infectious virus could not be recovered from either gp50- or gII- PrV-infected animals. We conclude that direct cell-to-cell transmission as the only means of viral spread of the gp50- mutants is sufficient for a full virulent phenotype in mice. After infection of pigs with phenotypically complemented gp50- PrV, only mild symptoms were observed, whereas the gII- mutant was totally avirulent. In both cases, shedding of infectious virus did not occur, in contrast to results with animals infected by gX- PrV that showed severe signs of disease and extensive virus shedding. After challenge infection with the highly virulent NIA-3 strain, the previously gII- PrV-infected animals exhibited severe symptoms, whereas the gp50- PrV-infected pigs showed a significant level of protection. In conclusion, vaccination with a PrV mutant lacking glycoprotein gp50, which is unable to spread between animals because of a lack of formation of free infectious virions, can confer on pigs protection against challenge infection. These results provide the basis for the development of new, nonspreading live herpesvirus vaccines based on gp50- PrV mutants.     

Research on calpain of Schistosoma japonicum as a vaccine candidate

Vaccine development by the use of calpain of Schistosoma japonicum has been tried in our laboratory. We cloned cDNA encoding the heavy chain of S. japonicum calpain, and prepared recombinant molecule of a possible vaccine region of the heavy chain. When BALB/c mice were immunized with our recombinant calpain of S. japonicum with Freund's complete adjuvant, we observed significant reduction in worm burden (41.2% reduction, P<0.05), and also significant anti-fecundity effects. In this sense, calpain of S. japonicum seems to have infection control as well as anti-disease effects. Mechanisms of vaccine effects of calpain remain to be clarified, however, several effector mechanisms are suspected. In immunized mice, raised level of iNos expression was observed, while adhesion of peritoneal exudates cells were also observed in the presence of calpain-immunized sera, suggesting the possibilities of both cellular and humoral protective mechanisms. We examined tissue distribution of calpain in various developmental stages of S. japonicum. Strong signal was observed around excretory grand of cercariae, and they secreted calpain during their migratory movement tested in vitro. Together with the findings, calpain seems to induce larvicidal effects in the immunized mice. We observed time-course kinetics of antibody production against vaccine candidates in experimental S. japonicum infection in pigs. Although significant levels of antibody production were observed for paramyosin and GST, no significant antibody production was observed for calpain. This suggests that calpain is less immunogenic, and route of immunization and/or choice of adjuvant are important in future trials of calpain vaccine.     

A chemically defined synthetic vaccine model for HIV-1.

Multiple Ag peptide (MAP) system without the use of a protein carrier was used as a vaccine model in three species of animals. Synthetic peptides from the V3 region of the gp120 of IIIB, RF and MN HIV-1 isolates were used as the Ag. MAP consisting of various chain lengths, from 11 to 24 residues, were prepared in a monoepitope configuration containing four repeats of each individual peptide. In parallel, they were synthesized in a diepitope configuration adding at the carboxyl-terminus of the V3 peptides a conserved sequence, known to be a Th cell epitope of gp120. The antibody response elicited by the monoepitope constructs was species-dependent. Rabbits produced immunity against all nine peptides, whereas mice were strongly reactive mainly to the longest sequence of the IIIB isolate. The immune response of guinea pigs was intermediate to those of rabbits and mice. Diepitope MAPs were immunogenic in all three species and elicited significantly higher titers than those raised by the immunization with the monoepitope MAPs. The response was type specific; the high-titered antibodies were reactive mostly against the isolate from which the peptides were derived, with a small cross-reactivity in ELISA between IIIB and RF strains. The dominant antigenic site of the B cell epitope, IIIB sequence, was located at the amino and central part of the MAP and a sequence overlapping the putative V3 reverse-turn was particularly reactive with the raised antibodies. Moreover, sera from the immunized animals inhibited virus-dependent cell fusion. These results show that MAP, with a chemically defined structure and without the use of a protein carrier, can be potentially useful for the design of synthetic HIV-1 vaccine candidates.     

Schistosoma malayensis n. sp.: a Schistosoma japonicum-complex schistosome from Peninsular Malaysia

Schistosoma malayensis n. sp., a member of the Schistosoma japonicum complex is described from Rattus muelleri in Peninsular Malaysia and 2 strains are characterized. The only morphological differences noted among adults from natural hosts were that S. malayensis are in general smaller than S. mekongi and S. japonicum. But these differences may be the result of host-induced variations and therefore are of little taxonomic value. To minimize the effects of host-induced variations, adult worms recovered from laboratory mice with similar worm burdens at 50-56 days postinfection were compared. These comparisons revealed only minor morphometric differences among these 3 species. Schistosoma malayensis eggs from naturally and experimentally infected hosts are most similar to those of S. mekongi, with eggs of both species being, in general, smaller than those of S. japonicum. The egg index for S. malayensis is usually higher than for S. japonicum and lower than for S. mekongi. Differences were noted in the developmental rates in mice for 2 isolates of S. malayensis, S. mekongi, and S. japonicum (Philippine strain), but relatively large differences observed between isolates of S. malayensis indicate that, in this case, the developmental rate is not a useful taxonomic character. Schistosoma malayensis is erected principally on the basis of differences, reported elsewhere, in the life histories and in the electrophoretic migration patterns of isoenzymes of adult worms as compared to S. mekongi and S. japonicum. These comparisons indicate that S. malayensis is more closely related to S. mekongi than to S. japonicum.     

Tuberculosis vaccine development: recent progress

Recent years have seen a renewed effort to develop new vaccines against tuberculosis. As a result, several promising avenues of research have developed, including the production of recombinant vaccines, auxotrophic vaccines, DNA vaccines and subunit vaccines. In this article we briefly review this work, as well as consider the pros and cons of the animal models needed to test these new vaccines. Screening to date has been carried out in mouse and guinea pig models, which have been used to obtain basic information such as the effect of the vaccine on bacterial load, and whether the vaccine can prevent or reduce lung pathology. The results to date lead us to be optimistic that new candidate vaccines could soon be considered for evaluation in clinical trials.     

Progress toward a malaria vaccine: efficient induction of protective anti-malaria immunity

Malaria can be a very severe disease, particularly in young children, pregnant women (mostly in primipara), and malaria na?ve adults, and currently ranks among the most prevalent infections in tropical and subtropical areas throughout the world. The widespread occurrence and the increased incidence of malaria in many countries, caused by drug-resistant parasites (Plasmodium falciparum and P. vivax) and insecticide-resistant vectors (Anopheles mosquitoes), indicate the need to develop new methods of controlling this disease. Experimental vaccination with irradiated sporozoites can protect animals and humans against the disease, demonstrating the feasibility of developing an effective malaria vaccine. However, developing a universally effective, long lasting vaccine against this parasitic disease has been a difficult task, due to several problems. One difficulty stems from the complexity of the parasite's life cycle. During their life cycle, malaria parasites change their residence within the host, thus avoiding being re-exposed to the same immunological environment. These parasites also possess some distinct antigens, present at different life stages of the parasite, the so-called stage-specific antigens. While some of the stage-specific antigens can induce protective immune responses in the host, these responses are usually genetically restricted, this being another reason for delaying the development of a universally effective vaccine. The stage-specific antigens must be used as immunogens and introduced into the host by using a delivery system that should efficiently induce protective responses against the respective stages. Here we review several research approaches aimed at inducing protective anti-malaria immunity, overcoming the difficulties described above.     

Mesenchymal stem cells: progress toward promise

Despite having access to embryonic stem cells, many laboratories choose to study adult stem cells, not because of philosophical reasons but because of the practical aspects and day-to-day progress necessary for developing cellular therapeutics. There is certainly the ethical desire and responsibility to provide patients with therapies where few options exist. Multipotential cells have been isolated from adult tissues in many laboratories, characterized and their multipotentiality examined. Mesenchymal stem cells (MSC) can be isolated from several tissues but easily accessible BM seems to be the most common source. These adult stem cells may not be as 'powerful' or diverse as embryonic stem cells may one day become, but at present they offer many advantages for developing cellular therapeutics: ease of isolation, expansion potential, stable phenotype, shippability, and compatibility with different delivery methods and formulations. Their potential use as cellular therapeutics has prompted the investigation of interactions of allogeneic MSC with the immune response. The great importance of cardiovascular medicine has demanded that MSC also be tested in this discipline. We believe MSC continue to provide a substantial scientific and therapeutic opportunity, and have reviewed some of the recent developments in the field.     

Waiting for the vaccine: sporozoite vaccine research entails important progress in malaria epidemiology.

The research efforts aimed at developing a vaccine against malaria, although failing thus far in their main objective, have produced molecular tools of great utility for epidemiological studies. For example, monoclonal antibodies directed against the repeats of Plasmodium circumsporozoite (CS) protein allowed the 2-site assay for detecting sporozoites in mosquitoes to be established. This immunoassay is advantageous compared with the conventional method of salivary gland dissection and microscopic examination, for it makes the identification of the sporozoite species possible, thanks to species-specific aminoacid sequences of the CS repeats. Other examples of vaccine research-derived tools are synthetic peptides reproducing the repetitive part of the CS protein, which allow antibodies to sporozoites, in individuals exposed to malaria, to be detected. Antibodies to the CS repeats of Plasmodium (Laverania) falciparum proved to be a reliable indicator of the intensity of malaria transmission and, therefore, were suitable for monitoring the impact of malaria control programmes. Finally, a project is outlined that, relying on the application of these tools, will aim at characterizing the transmission of Plasmodium (Plasmodium) malariae and at unveiling the possible relationship among different species thriving in the same distribution area, an issue which may become of relevance in view of the likely introduction of a vaccine directed against a single species.     

Iron requirement of Lactobacillus spp. in completely chemically defined growth media

A completely chemically-defined growth medium, containing guanine, thymine, cytidine, 2'-deoxyadenosine and 2'-deoxyuridine as DNA precursors, was developed for Lactobacillus johnsonii, on the basis of statistically designed techniques suitable for other lactobacilli. Particular focus was given to the nucleotide composition of different defined media, and to the specific nucleotide requirements of Lact. johnsonii. Most of the lactobacilli tested grew in a medium containing five free bases, four ribonucleosides or five deoxyribonucleosides. Adenine and guanine were replaceable by inosine. The requirement for thymine and cytosine was satisfied with uracil. The presence of inosine and uracil was identified as being essential for the growth of different Lactobacillus species, displaying their inability to synthesize purines and pyrimidines de novo. Defined recipes with different nucleotide composition were used to investigate iron requirements of lactobacilli. Only marginal differences in growth were observed in iron-depleted media supplemented with five free bases, four ribonucleosides or five deoxyribonucleosides; iron depletion had a greater effect on growth when inosine and uracil were supplied as the only nucleotide sources. The results suggest that iron plays a role in the pyrimidine and purine metabolism of lactobacilli. Lactobacillus spp., particularly Lact. johnsonii, require iron under particular environmental conditions with limited or specific nucleotide sources.     

Simultaneous degradation of 3-chlorobenzoate and phenolic compounds by a defined mixed culture ofPseudomonas spp.

A mixed culture of a chlorobenzoate-(3-CBA)-degradingPseudomonas aeruginosa, strain 3mT, and a phenol/cresols-degradingPseudomonas sp., strain CP4, simultaneously and efficiently degraded mixtures of 3-CBA and phenol/cresols. However, strains 3mT and CP4 usedortho- andmeta-ring cleavage pathways, respectively. Degradation of 3-CBA was complete when the 3-CBA was equal in amount to or less than that of phenol. CP4/3mT inoculum ratios (w/w) of 1:1 or 1:2 gave the most effective degradation of both the substrates in the mixture. The mixed culture degraded equimolar mixtures of 3-CBA/phenol up to 10mm. Equimolar mixtures of 3-CBA ando-, m- orp-cresol were also degraded by the mixed culture.The authors are with the Microbiology and Bioengineering Department, Central Food Technological Research Institute, Mysore-570013, India;     

Progress toward the development of a genetically engineered attenuated hepatitis A virus vaccine.

Mutations which positively affect growth of hepatitis A virus in cell culture may negatively affect growth in vivo. Therefore, development of an attenuated vaccine for hepatitis A may require a careful balancing of mutations to produce a virus that will grow efficiently in cells suitable for vaccine production and still maintain a satisfactory level of attenuation in vivo. Since such a balance could be achieved most directly by genetic engineering, we are analyzing mutations that accumulated during serial passage of the HM-175 strain of hepatitis A virus in MRC-5 cell cultures in order to determine the relative importance of the mutations for growth in MRC-5 cells and for attenuation in susceptible primates. Chimeric viral genomes of the HM-175 strain were constructed from cDNA clones derived from a virulent virus and from two attenuated viruses adapted to growth in African green monkey kidney (AGMK) and MRC-5 cells, respectively. Viruses encoded by these chimeric genomes were recovered by in vitro or in vivo transfection and assessed for their ability to grow in cultured MRC-5 cells or to cause hepatitis in primates (tamarins). The only MRC-5-specific mutations that substantially increased the efficiency of growth in MRC-5 cells were a group of four mutations in the 5' noncoding (NC) region. These 5' NC mutations and a separate group of 5' NC mutations that accumulated during earlier passages of the HM-175 virus in primary AGMK cells appeared, independently and additively, to result in decreased biochemical evidence of hepatitis in tamarins. However, neither group of 5' NC mutations had a demonstrable effect on the extent of virus excretion or liver pathology in these animals.