South American monkeys in the development and testing of malarial vaccines - a review

South American Aoutus an d Saimiri monkeys, which are susceptible to infection with human malarias, have been used to develop models for the testing of huma malaria vaccines. Studies indicate that blood-stage and sporozoite vaccines can be tested in these monkeys using appropriate strains of parasites.

The antibody response in mice to carrier-free synthetic polymers of Plasmodium falciparum circumsporozoite repetitive epitope is I-Ab-restricted: possible implications for malaria vaccines.

The immunogenicity of a novel synthetic peptide consisting of an average of 40 (Asn-Ala-Asn-Pro) repeats of the circumsporozoite protein of Plasmodium falciparum, (NANP)40, was studied in mice without using any carrier proteins. First, high titers of anti-(NANP)40 antibodies could be obtained after immunization of C57BL/6 mice. These antibodies also reacted with an extract of mosquitoes infected with P. falciparum sporozoites. C57BL/6 nu/nu mice did not produce antibodies against (NANP)40. Secondly, when 14 strains of mice with nine different H-2 haplotypes were immunized with (NANP)40 without carrier, only H-2b mice were found to produce anti-(NANP)40 antibodies, whereas all non-H-2b mice were consistently unresponsive. This response was demonstrated to be I-A-linked by using recombinant and mutant mice. I-Ab [B10.A(5R)] mice produced anti-(NANP)40 antibodies as well as H-2b inbred mice. B6CH-2bm12 I-Ab-mutant mice showed only a very low response. Third, the antibody response against (NANP)40 could be induced in nonresponder mice by immunization with the peptide coupled to a carrier protein. In view of the existence of such an exceptional H-2b restriction in the response to sporozoite synthetic peptides in mice, the triggering of peptide-specific T cell responses in humans receiving sporozoite malaria vaccines might be difficult to achieve.

Desenvolupament de vacunes peptídiques y dendrímers basats en polietilenglicol per al tractament del càncer

El principal problema de les teràpies actuals contra el càncer es la baixa especificitat envers les cèl•lules tumorals, cosa que comporta gran quantitat d’efectes secundaris. Per això es important el desenvolupament de nous tipus de teràpies i sistemes d’alliberament efectius per als fàrmacs ja existents al mercat. En la immunoteràpia contra el càncer es pretén estimular el sistema immunològic per a eliminar les cèl•lules canceroses de manera selectiva. En aquest projecte s’han sintetitzat derivats de l’antigen peptídic de melanoma NY-ESO1 i s’ha estudiat la seva capacitat per a estimular el sistema immunològic com a vacunes contra el càncer. També s’han encapsulat el antígens peptídics en liposomes com a adjuvants i sistemes d’alliberament. De totes les variants peptídiques la que resultà més immunogènica fou la que contenia el grup palmitoil i el fragment toxoide tetànic en la seva estructura. La utilització de liposomes com a sistema adjuvant sembla una estratègia interessant per al disseny de vacunes contra el càncer donat que l’encapsulació del pèptid en liposomes va augmentar notablement la resposta immunològica de l’antigen. Per altra banda, s’han desenvolupat dendrímers basats en polietilenglicol com a sistemes alliberadors de fàrmacs per al tractament de tumors. El polietilenglicol és àmpliament utilitzat com a sistema d’alliberament de fàrmacs degut a les seves interessants propietats, augment de la solubilitat i dels temps de residència en plasma, entre d’altres. La metodologia química descrita permet la diferenciació controlada de varies posicions en la superfície del dendrímer a més del creixement del dendrímer fins a una segona generació. S’ha sintetitzat la primera generació del dendrímer contenint el fàrmac antitumoral 5-fluorouracil i s’han realitzat estudis de citotoxicitat comprovant que l’activitat del nanoconjugat és del mateix ordre de magnitud que el 5-fluorouracil sense conjugar.

A research agenda for malaria eradication: vaccines.

Vaccines could be a crucial component of efforts to eradicate malaria. Current attempts to develop malaria vaccines are primarily focused on Plasmodium falciparum and are directed towards reducing morbidity and mortality. Continued support for these efforts is essential, but if malaria vaccines are to be used as part of a repertoire of tools for elimination or eradication of malaria, they will need to have an impact on malaria transmission. We introduce the concept of "vaccines that interrupt malaria transmission" (VIMT), which includes not only "classical" transmission-blocking vaccines that target the sexual and mosquito stages but also pre-erythrocytic and asexual stage vaccines that have an effect on transmission. VIMT may also include vaccines that target the vector to disrupt parasite development in the mosquito. Importantly, if eradication is to be achieved, malaria vaccine development efforts will need to target other malaria parasite species, especially Plasmodium vivax, where novel therapeutic vaccines against hypnozoites or preventive vaccines with effect against multiple stages could have enormous impact. A target product profile (TPP) for VIMT is proposed and a research agenda to address current knowledge gaps and develop tools necessary for design and development of VIMT is presented.

The yellow fever 17D vaccine virus as a vector for the expression of foreign proteins: development of new live flavivirus vaccines

The Flaviviridae is a family of about 70 mostly arthropod-borne viruses many of which are major public health problems with members being present in most continents. Among the most important are yellow fever (YF), dengue with its four serotypes and Japanese encephalitis virus. A live attenuated virus is used as a cost effective, safe and efficacious vaccine against YF but no other live flavivirus vaccines have been licensed. The rise of recombinant DNA technology and its application to study flavivirus genome structure and expression has opened new possibilities for flavivirus vaccine development. One new approach is the use of cDNAs encopassing the whole viral genome to generate infectious RNA after in vitro transcription. This methodology allows the genetic mapping of specific viral functions and the design of viral mutants with considerable potential as new live attenuated viruses. The use of infectious cDNA as a carrier for heterologous antigens is gaining importance as chimeric viruses are shown to be viable, immunogenic and less virulent as compared to the parental viruses. The use of DNA to overcome mutation rates intrinsic of RNA virus populations in conjunction with vaccine production in cell culture should improve the reliability and lower the cost for production of live attenuated vaccines. The YF virus despite a long period ignored by researchers probably due to the effectiveness of the vaccine has made a come back, both in nature as human populations grow and reach endemic areas as well as in the laboratory being a suitable model to understand the biology of flaviviruses in general and providing new alternatives for vaccine development through the use of the 17D vaccine strain.

Immunogenicity test of tetanus component in adsorbed vaccines by toxin binding inhibition test

Samples from 20 lots of diphtheria-tetanus (adult use dT) vaccine and from 20 lots of diphtheria-tetanus-pertussis (DTP) vaccine were used to standardize and validate the in vitro toxin binding inhibition (ToBI) test for the immunogenicity test of the tetanus component. The levels of tetanus antitoxin obtained by ToBI test were compared to those obtained using the toxin neutralization (TN) test in mice routinely employed to perform the quality control of the tetanus component in adsorbed vaccines. The results ranged from 1.8 to 3.5 IU/ml for dT and 2 to 4 IU/ml for DTP by ToBI test and 1.4 to 3 IU/ml for dT and 1.8 to 3.5 IU/ml for DTP by TN in mice. These results were significantly correlated. From this study, it is concluded that the ToBI test is an alternative to the in vivo neutralization procedure in the immunogenicity test of the tetanus component in adsorbed vaccines. A substantial refinement and a reduction in use of animals can be achieved.

Study of the safety, immunogenicity and efficacy of attenuated and killed Leishmania (Leishmania) major vaccines in a rhesus monkey (Macaca mulatta) model of the human disease

We have compared the efficacy of two Leishmania (Leishmania) major vaccines, one genetically attenuated (DHFR-TS deficient organisms), the other inactivated [autoclaved promastigotes (ALM) with bacillus Calmete-Guérin (BCG)], in protecting rhesus macaques (Macaca mulatta) against infection with virulent L. (L.) major. Positive antigen-specific recall proliferative response was observed in vaccinees (79% in attenuated parasite-vaccinated monkeys, versus 75% in ALM-plus-BCG-vaccinated animals), although none of these animals exhibited either augmented in vitro gamma interferon (IFN-g) production or positive delayed-type hypersensitivity (DTH) response to the leishmanin skin test prior to the challenge. Following challenge, there were significant differences in blastogenic responses (p < 0.05) between attenuated-vaccinated monkeys and naïve controls. In both vaccinated groups very low levels of antibody were found before challenge, which increased after infective challenge. Protective immunity did not follow vaccination, in that monkeys exhibited skin lesion at the site of challenge in all the groups. The most striking result was the lack of pathogenicity of the attenuated parasite, which persisted in infected animals for up to three months, but were incapable of causing disease under the conditions employed. We concluded that both vaccine protocols used in this study are safe in primates, but require further improvement for vaccine application.

Antigenic community between Schistosoma mansoni and Biomphalaria glabrata: on the search of candidate antigens for vaccines

We have previously confirmed the presence of common antigens between Schistosoma mansoni and its vector, Biomphalaria glabrata. Cross-reactive antigens may be important as possible candidates for vaccine and diagnosis of schistosomiasis. Sera from outbred mice immunized with a soluble Biomphalaria glabrata antigen (SBgA) of non-infected B. glabrata snails recognized molecules of SBgA itself and S. mansoni AWA by Western blot. Recognition of several molecules of the SBgA were inhibited by pre-incubation with AWA (16, 30, 36, 60 and 155 kDa). The only specific molecule of AWA, inhibited by SBgA, was a 120 kDa protein. In order to determine which epitopes of SBgA were glycoproteins, the antigen was treated with sodium metaperiodate and compared with non-treated antigen. Molecules of 140, 60 and 24 kDa in the SBgA appear to be glycoproteins. Possible protective effects of the SBgA were evaluated immunizing outbred mice in two different experiments using Freund's Adjuvant. In the first one (12 mice/group), we obtained a significant level of protection (46%) in the total worm load, with a high variability in worm recovery. In the second experiment (22 mice/group), no significant protection was observed, neither in worm load nor in egg production per female. Our results suggest that SBgA constitutes a rich source of candidate antigens for diagnosis and prophylactic studies.

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

We evaluated the usefulness of the combination of three plasmids encoding tegumental (pECL and pSM14) and muscular (pIRV5) antigens of the Schistosoma mansoni on improving the protective immunity over the use of a single antigen as DNA vaccines. Female BALB/c mice were inoculated twice with 25 µg DNA plasmid within two weeks interval. The challenge was performed with 80 cercarias of a regional isolate of S. mansoni (SLM) one week after the last immunization. Six weeks after challenge, all mice were perfused for worm load determination. The following groups were analyzed: saline; empty vector; monovalent formulations of pECL; pSM14 and pIRV5 and also double combinations of pECL/pIRV5 and pIRV5/pSM14 and a triple combination of pECL/pIRV5/pSM14. The protection was expressed as a percentage of worm loads in each group compared with the saline group. The results obtained were 41% (p < 0.05); 52% (p < 0.05); 51% (p < 0.05); 48% (p < 0.05); 55% (p < 0.05); 45% (p < 0.05); 65% (p < 0.05) for each group respectively.

The facts about the MMR and pneumococcal vaccines for babies aged 15 months (English and 10 translations)

This booklet provides the facts about the MMR vaccine against measles, mumps and rubella

Multicenter study on the immunogenicity and safety of two recombinant vaccines against hepatitis B

The immunogenicity and safety of a new recombinant hepatitis B vaccine from the Instituto Butantan (Butang®) were evaluated in a multicenter, double-blind, prospective equivalence study in three centers in Brazil. Engerix B® was the standard vaccine. A total of 3937 subjects were recruited and 2754 (70%) met all protocol criteria at the end of the study. All the subjects were considered healthy and denied having received hepatitis B vaccine before the study. Study subjects who adhered to the protocol were newborn infants (566), children 1 to 10 years old (484), adolescents from 11 to 19 years (740), adults from 20 to 30 years (568), and adults from 31 to 40 years (396). Vaccine was administered in three doses on the schedule 0, 1, and 6 months (newborn infants, adolescents, and adults) or 0, 1, and 7 months (children). Vaccine dose was intramuscular 10 µg (infants, children, and adolescents) or 20 µg (adults). Percent seroprotection (assumed when anti-HBs titers were > 10mIU/ml) and geometric mean titer (mIU/ml) were: newborn infants, 93.7% and 351.1 (Butang®) and 97.5% and 1530.6 (Engerix B®); children, 100% and 3600.0 (Butang®) and 97.7% and 2753.1 (Engerix B®); adolescents, 95.1% and 746.3 (Butang®) and 96% and 1284.3 (Engerix B®); adults 20-30 years old, 91.8% and 453.5 (Butang®) and 95.5% and 1369.0 (Engerix B®); and adults 31-40 years old, 79.8% and 122.7 (Butang®) and 92.4% and 686.2 (Engerix B®). There were no severe adverse events following either vaccine. The study concluded that Butang® was equivalent to Engerix B® in children, and less immunogenic but acceptable for use in newborn infants, adolescents, and young adults.

From genomes to vaccines via the proteome

An effective vaccine against schistosomiasis mansoni would be a valuable control tool and the high levels of protection elicited in rodents and primates by radiation-attenuated cercariae provide proof of principle. A major obstacle to vaccine development is the difficulty of identifying the antigens that mediate protection, not least because of the size of the genome at 280Mb DNA encoding 14,000 to 20,000 genes. The technologies collectively called proteomics, including 2D electrophoresis, liquid chromatography and mass spectrometry, now permit any protein to be identified provided there is extensive DNA data, and preferably a genome sequence. Applied to soluble (cytosolic) proteins from schistosomes, proteomics reveals the great similarity in composition between life cycle stages, with several WHO vaccine candidates amongst the most abundant constituents. The proteomic approach has been successfully applied to identify the secretions used by cercaria to penetrate host skin, the gut secretions of adult worms and the proteins exposed on the tegument surface. Soluble proteins can also be separated by 2D electrophoresis before western blotting to identify the full range of antigenic targets present in a parasite preparation. The next step is to discover which target proteins represent the weak points in the worm's defences.