Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0024530 (malaria)
 44,886 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Immunodominant T-cell antigenic sites can so dominate a response that their presence leads to high responsiveness and their absence to low responsiveness. Therefore, it is important to locate such sites for vaccine development. Factors that lead to immunodominance include features extrinsic to the structure of the site itself, such as the major histocompatibility complex (MHC) molecules of the host and the types of fragments produced by processing of the protein antigen before the T cell sees it. They also include factors intrinsic to the structure of the T-cell site, that determine a repertoire of potential immunodominant sites from which the extrinsic factors select a subset that will be immunodominant in a given individual. We have focused on one of these intrinsic factors, helical amphipathicity, that we have found to be a common feature among both helper and cytotoxic T-cell antigenic sites, suggesting that the same physical principles apply to sites seen in association with class I and class II MHC molecules. We have used this feature to locate immunodominant epitopes on the circumsporozoite protein of the Plasmodium falciparum malaria parasite and the envelope protein of the AIDS virus. Both helper and cytotoxic T-cell epitopes were identified. At least in the case of the helper T-cell sites, it was striking that the same sites in both the malaria and AIDS proteins studied that were immunodominant in the mouse were also immunodominant in the human, an indication that the same principles apply across species, and that the animal model will be useful for identifying sites to be used in vaccines for humans. These sites have been coupled with neutralizing antibody sites to produce artificial constructs that can elicit antibodies. It is hoped that the rational design of more complex versions of these artificial constructs will produce vaccines that are more effective than the natural pathogen proteins used in subunit vaccines, since such pathogen protein antigens have been selected through evolution to evade the immune system, not to optimize immunogenicity.
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PMID:Mechanisms of immunodominance in T-cell recognition, with applications to vaccine design. 247 31

This paper provides a review on the development of hepatitis core antigen as a vaccine carrier moiety and the use of recombinant Salmonella vaccine strains expressing hybrid HBcAg particles as live oral vaccines. Salmonella spp. can be attenuated by defined genetic means so that they become avirulent, yet preserve invasiveness after oral uptake. Oral immunization of mice with such avirulent candidate Salmonella typhimurium vaccine strains elicited serum antibody responses against a limited number of bacterial antigens. A highly immunogenic viral nucleocapsid antigen, hepatitis B virus core antigen (HBcAg) that can be expressed in prokaryotes was used as a carrier moiety for B-cell epitopes. Insertion sites with an enhanced immunogenicity for the carried epitopes were defined using HBV envelope protein virus neutralizing epitopes. An internal insertion site in HBcAg was found that drastically enhanced the immunogenicity of the foreign (pre-S1) epitope while reducing the immunogenicity of the carrier protein. Internally fused HBc/pre-S hybrid particles were expressed in Salmonella typhimurium and S. typhi vaccine strains. A single oral immunization of mice with such live recombinant S. typhimurium strains elicited a high titred serum anti-pre-S1 IgG response. Similarly, circumsporozoite repeat epitopes of three different malaria parasites were expressed as HBcAg/CS hybrids in recombinant S. spp. and were found to be highly immunogenic.
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PMID:Development of recombinant Salmonellae expressing hybrid hepatitis B virus core particles as candidate oral vaccines. 795 69

Invasion of hepatocytes by Plasmodium sporozoites is a prerequisite for establishment of a malaria infection, and thus represents an attractive target for anti-malarial interventions. Still, the molecular mechanisms underlying sporozoite invasion are largely unknown. We have previously reported that the tetraspanin CD81, a known receptor for the hepatitis C virus (HCV), is required on hepatocytes for infection by sporozoites of several Plasmodium species. Here we have characterized CD81 molecular determinants required for infection of hepatocytic cells by P. yoelii sporozoites. Using CD9/CD81 chimeras, we have identified in CD81 a 21 amino acid stretch located in a domain structurally conserved in the large extracellular loop of tetraspanins, which is sufficient in an otherwise CD9 background to confer susceptibility to P. yoelii infection. By site-directed mutagenesis, we have demonstrated the key role of a solvent-exposed region around residue D137 within this domain. A mAb that requires this region for optimal binding did not block infection, in contrast to other CD81 mAbs. This study has uncovered a new functionally important region of CD81, independent of HCV E2 envelope protein binding domain, and further suggests that CD81 may not interact directly with a parasite ligand during Plasmodium infection, but instead may regulate the function of a yet unknown partner protein.
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PMID:Hepatocyte permissiveness to Plasmodium infection is conveyed by a short and structurally conserved region of the CD81 large extracellular domain. 1838 82

This article focuses on a novel vaccine strategy known as vector-mediated antibody gene transfer, with a particular focus on human immunodeficiency virus (HIV). This strategy provides a solution to the problem of current vaccines that fail to generate neutralizing antibodies to prevent HIV-1 infection and AIDS. Antibody gene transfer allows for predetermination of antibody affinity and specificity prior to "immunization" and avoids the need for an active humoral immune response against the HIV envelope protein. This approach uses recombinant adeno-associated viral (rAAV) vectors, which have been shown to transduce muscle with high efficiency and direct the long-term expression of a variety of transgenes, to deliver the gene encoding a broadly neutralizing antibody into the muscle. Following rAAV vector gene delivery, the broadly neutralizing antibodies are endogenously synthesized in myofibers and passively distributed to the circulatory system. This is an improvement over classical passive immunization strategies that administer antibody proteins to the host to provide protection from infection. Vector-mediated gene transfer studies in mice and monkeys with anti-HIV and simian immunodeficiency virus (SIV)-neutralizing antibodies demonstrated long-lasting neutralizing activity in serum with complete protection against intravenous challenge with virulent HIV and SIV. These results indicate that existing potent anti-HIV antibodies can be rapidly moved into the clinic. However, this methodology need not be confined to HIV. The general strategy of vector-mediated antibody gene transfer can be applied to other difficult vaccine targets such as hepatitis C virus, malaria, respiratory syncytial virus, and tuberculosis.
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PMID:Vector-Mediated In Vivo Antibody Expression. 2610 92

The malaria parasite Plasmodium falciparum presents antigens on the infected erythrocyte surface that bind human receptors expressed on the vascular endothelium. The VAR2CSA mediated binding to a distinct chondroitin sulphate A (CSA) is a crucial step in the pathophysiology of placental malaria and the CSA binding region of VAR2CSA has been identified as a promising vaccine target against placental malaria. Here we designed adenovirus encoded virus-like particles (VLP) by co-encoding Simian Immunodeficiency Virus (SIV) gag and VAR2CSA. The VAR2CSA antigen was fused to the transmembrane (TM) and cytoplasmic tail (CT) domains of either the envelope protein of mouse mammary tumour virus (MMTV) or the hemagglutinin (HA) of influenza A. For a non-VLP incorporation control, a third design was made where VAR2CSA was expressed without TM-CT domains. In the primary immunogenicity study in Balb/c mice, VAR2CSA fused to HA TM-CT was significantly superior in inducing ID1-ID2a specific antibodies after the first immunization. A sequential study was performed to include a comparison to the soluble VAR2CSA protein vaccine, which has entered a phase I clinical trial (NCT02647489). The results revealed the induction of higher antibody responses and increased inhibition of parasite binding to CSA using either VAR2CSA HA TM-CT or VAR2CSA MMTV TM-CT as priming vaccines for protein double-boost immunizations, compared to protein prime-double boost regimen. Analysis of pooled serum samples on peptide arrays revealed a unique targeting of several epitopes in mice that had been primed with VAR2CSA HA TM-CT. Consequently, modification of VLP anchors is an important point of optimization in virus-encoded retroviral VLP-based vaccines, and adenovirus VLPs boosted by recombinant proteins offer hope of increasing the levels of protective VAR2CSA specific antibodies.
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PMID:Novel adenovirus encoded virus-like particles displaying the placental malaria associated VAR2CSA antigen. 2813 94

Virus-like particles (VLPs) are noninfectious multiprotein structures that are engineered to self-assemble from viral structural proteins. Here, we developed a novel VLP-based vaccine platform utilizing VLPs from the chikungunya virus. We identified two regions within the envelope protein, a structural component of chikungunya, where foreign antigens can be inserted without compromising VLP structure. Our VLP displays 480 copious copies of an inserted antigen on the VLP surface in a highly symmetric manner and is thus capable of inducing strong immune responses against any inserted antigen. Furthermore, by mimicking the structure of the immature form of the virus, we altered our VLP's in vivo dynamics and enhanced its immunogenicity. We used the circumsporozoite protein (CSP) of the Plasmodium falciparum malaria parasite as an antigen and demonstrated that our VLP-based vaccine elicits strong immune responses against CSP in animals. The sera from immunized monkeys protected mice from malaria infection. Likewise, mice vaccinated with P. yoelii CSP-containing VLPs were protected from an infectious sporozoite challenge. Hence, our uniquely engineered VLP platform can serve as a blueprint for the development of vaccines against other pathogens and diseases.
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PMID:Development of a Novel Virus-Like Particle Vaccine Platform That Mimics the Immature Form of Alphavirus. 2851 33