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Luz Mary Salazar

Publications and source records attributed to Luz Mary Salazar.

16 recordsLinked to original sources
PubMed2006

BTM-P1 polycationic peptide biological activity and 3D-dimensional structure.

The novel BTM-P1 peptide interferes with energetic processes in mitochondria; its antimicrobial activity against Gram-positive and Gram-negative bacteria is described here. BTM-P1 three-dimensional structure was determined by 1H NMR to explain its biological mechanisms and membrane activity. Structural data indicated that BTM-P1 can form an alpha-helix; circular dichroism analysis confirmed the peptide's propensity to behave as a typical transmembrane helix in a lipidic environment. According to the structural characteristics of the polycationic BTM-P1 peptide so revealed, its biological activity can be explained by a mechanism involving the formation of ion-permeable channels in biomembranes.

Amino Acid Sequence↗
PubMed2006

Major histocompatibility complex and T cell interactions of a universal T cell epitope from Plasmodium falciparum circumsporozoite protein.

A 20-residue sequence from the C-terminal region of the circumsporozoite protein of the malaria parasite Plasmodium falciparum is considered a universal helper T cell epitope because it is immunogenic in individuals of many major histocompatibility complex (MHC) haplotypes. Subunit vaccines containing T* and the major B cell epitope of the circumsporozoite protein induce high antibody titers to the malaria parasite and significant T cell responses in humans. In this study we have evaluated the specificity of the T* sequence with regard to its binding to the human class II MHC protein DR4 (HLA-DRB1*0401), its interactions with antigen receptors on T cells, and the effect of natural variants of this sequence on its immunogenicity. Computational approaches identified multiple potential DR4-binding epitopes within T*, and experimental binding studies confirmed the following two tight binding epitopes: one located toward the N terminus (the T*-1 epitope) and one at the C terminus (the T*-5 epitope). Immunization of a human DR4 volunteer with a peptide-based vaccine containing the T* sequence elicited CD4+ T cells that recognize each of these epitopes. Here we present an analysis of the immunodominant N-terminal epitope T*-1. T*-1 residues important for interaction with DR4 and with antigen receptors on T*-specific T cells were mapped. MHC tetramers carrying DR4/T*-1 MHC-peptide complexes stained and efficiently stimulated these cells in vitro. T*-1 overlaps a region of the protein that has been described as highly polymorphic; however, the particular T*-1 residues required for anchoring to DR4 were highly conserved in Plasmodium sequences described to date.

Amino Acid Sequence↗
PubMed2006

High non-protective, long-lasting antibody levels in malaria are associated with haplotype shifting in MHC-peptide-TCR complex formation: a new mechanism for immune evasion.

An effective malarial vaccine must contain multiple immunogenic, protection-inducing epitopes able to block and destroy the P. falciparum malaria parasite, the most lethal form of this disease in the world. Our strategy has consisted in using conserved peptides blocking parasite binding to red blood cells; however, these peptides are non-immunogenic and non-protection-inducing. Modifying their critical residues can make them immunogenic. Such peptides induced antibody titers (determined by immunofluorescence antibody test, IFA) and made the latter reactive (determined by Western blot) and protection inducing against experimental challenge with a highly infective Aotus monkey adapted P. falciparum strain. Modified peptides also induce highly non-protective long-lasting antibody levels. Modifications performed might allow them to bind specifically to different HLA-DRbeta purified molecules. These immunological and biological activities are associated with modifications in their three-dimensional structure as determined by (1)H-NMR. It was found that modified, high non-protective long-lasting antibody level peptides bound to HLA-DR molecules from a different haplotype (to which immunogenic, protection-inducers bind) and had 4.6 +/- 1.4 A shorter distances between residues fitting into these molecules' Pocket 1 to Pocket 9, suggesting fitting into an inappropriate HLA-DR molecule. A multi-component, subunit-based, malarial vaccine is therefore feasible if modified peptides are suitably modified for an appropriate fit into the correct HLA-DRbeta1* molecule in order to form a proper MHC-II-peptide-TCR complex.

Amino Acid Sequence↗
PubMed2005

Protective cellular immunity against P. falciparum malaria merozoites is associated with a different P7 and P8 residue orientation in the MHC-peptide-TCR complex.

Developing a logical and rational methodology for obtaining vaccines, especially against the main parasite causing human malaria (P. falciparum), consists of blocking receptor-ligand interactions. Conserved peptides derived from proteins involved in invasion and having high red blood cell binding ability have thus been identified. Immunization studies using Aotus monkeys have revealed that these peptides were neither immunogenic nor protection inducing. When modified in their critical binding residues, previously identified by Glycine scanning, some of these peptides were immunogenic and non-protection inducers; others induced short-lived antibodies whilst a few were both immunogenic and protection inducing. However, very few of these modified high activity binding peptides (HABPs) reproducibly induced protection without inducing antibody production, but with high cytokine liberation, suggesting that cellular mechanisms had been activated in the protection process. The three-dimensional structure of these peptides inducing protection without producing antibodies was determined by 1H-NMR. Their HLA-DRbeta1* molecule binding ability was also determined to ascertain association between their 3D structure and ability to bind to Major Histocompatibility Complex Class-II molecules (MHC-II). 1H Nuclear Magnetic Resonance analysis and structure calculations clearly showed that these modified HABPs inducing protective cellular immune responses (but not producing antibodies against malaria) adopted special structural configuration to fit into the MHC II-peptide-TCR complex. A different orientation for P7 and P8 TCR contacting residues was clearly recognized when comparing their structure with modified peptides, which induced high antibody titers and protection, suggesting that these residues are involved in activating the immune system associated with antibody production and protection.

Amino Acid Sequence↗
PubMed2005

Elongating modified conserved peptides eliminates their immunogenicity and protective efficacy against P. falciparum malaria.

Plasmodium falciparum malaria protein peptides were synthesised in the search for more effective routes for inducing a protective immune response against this deadly parasite and this information has been associated with such molecules' three-dimensional structure. These peptides had high red blood cell binding activity and their carboxy- and amino-terminal extremes were elongated for determining their immunogenic and protection-inducing activity against this disease in the Aotus monkey experimental model. 1H-NMR was used for analysing their three-dimensional structure; FAST ELISA, immunofluorescence antibody test, and Western blot were used for identifying their antibody inducing capacity and these previously immunised Aotus were inoculated with a highly infective P. falciparum strain to determine whether these elongated peptides were able to induce protection. This was aimed at establishing an association or correlation between long peptides' three-dimensional structure and their immunogenic and protection-inducing response in these monkeys. Peptides 20026 (25 residue), 20028 (30 residue), and 20030 (35 residues) were synthesised based on elongating the amino-terminal region of the 10022 highly immunogenic and protection-inducing modified peptide. 1H-NMR studies revealed that the first three had Classical type III beta-turn structures, different from the 20-amino acid long modified peptide 10022 which had a distorted type III beta-turn. Humoral immune response analysis showed that even when some antibodies could be generated against the parasite, none of the immunised Aotus could be protected with elongated peptides suggesting that elongating them eliminated modified peptide 10022 immunogenic and protection-inducing capacity.

Amino Acid Sequence↗
PubMed2005

Evidence supporting the hypothesis that specifically modifying a malaria peptide to fit into HLA-DRbeta1*03 molecules induces antibody production and protection.

EBA-175 protein is used as ligand in Plasmodium falciparum binding to erythrocytes. Evidence shows that conserved peptide 1815 from this protein having high red blood cell binding ability plays an important role in the invasion process. This peptide is neither immunogenic nor protective. Residues were substituted by amino acids having similar volume or mass but different polarity in 1815 analogues had to make them fit into HLA-DRbeta1*03 molecules; these were synthesised and inoculated into Aotus monkeys, generating different immunogenic and/or protective immune responses. A shortening in alpha-helix structure was found in the immunogenic and protective ones when their secondary structure was analyzed by NMR to correlate their structure with their immunological properties. This data, together with results from previous studies, suggests that this shortening in high-activity binding peptide (HABP) helical configuration may lead to better fitting into immune system molecules as shown by binding to purified HLA-DRbeta1* molecules rendering them immunogenic and protective and therefore, excellent candidates for consideration as components of a subunit based multi-component synthetic vaccine against malaria.

Amino Acid Sequence↗
PubMed2004

Modifying RESA protein peptide 6671 to fit into HLA-DRbeta1* pockets induces protection against malaria.

6671 is a non-immunogenic, conserved high activity red blood cell binding peptide located between residues 141 and 160 of the Plasmodium falciparum RESA protein. This peptide's critical red blood cell (RBC) binding residues have been replaced by amino acids having similar mass but different charge to change their immunologic properties. Three analogues (two of them immunogenic and protective and one immunogenic) were studied by purified HLA-DRbeta1* binding and NMR to correlate their structure with their immunological properties. Native peptide 6671 had a very flexible beta-sheet structure, whilst its immunogenic, protective, and non-protective peptide analogues presented an alpha-helical structure having different locations and lengths. These changes in peptide structure facilitated their fitting into HLA-DRbeta1* molecules. This paper shows for the first time how modifications performed on RESA protein non-immunogenic, non-protectogenic peptides impose a configuration allowing them to fit perfectly into the MHC II-TCR complex, in turn leading to appropriate activation of the immune system.

Alleles↗
PubMed2004

Induction and displacement of an helix in the 6725 SERA peptide analogue confers protection against P. falciparum malaria.

The protein called serine repeat antigen (SERA) is a Plasmodium falciparum malaria antigen; high activity erythrocyte binding peptides have been identified in this protein. One of these, the 6725 peptide (non-immunogenic and non-protective), was analyzed for immunogenicity and protective activity in Aotus monkeys, together with several of its analogues. These peptides were studied by 1H NMR to try to correlate their structure with their biological function. These peptides showed helical regions having differences in their position, except for randomly structured 6725. It is shown that replacing some amino acids induced immunogenicity and protectivity against experimental malaria and changed their three-dimensional (3D) structure, suggesting that such modifications may allow a better fit with immune system molecules.

Amino Acid Sequence↗
PubMed2004

Mapping the anatomy of a Plasmodium falciparum MSP-1 epitope using pseudopeptide-induced mono- and polyclonal antibodies and CD and NMR conformation analysis.

Antigen structure modulation represents an approach towards designing subunit malaria vaccines. A specific epitope's alpha carbon stereochemistry, as well as its backbone topochemistry, was assessed for obtaining novel malarial immunogens. A variety of MSP-1(38-61) Plasmodium falciparum epitope pseudopeptides derived were synthesised, based on solid-phase pseudopeptide chemistry strategies; these included all-L, all-D, partially-D substituted, all-Psi-[NH-CO]-Retro, all-Psi-[NH-CO]-Retro-inverso, and Psi-[CH2NH] reduced amide surrogates. We demonstrate that specific recombinant MSP-1(34-469) fragment binding to red blood cells (RBCs) is specifically inhibited by non-modified MSP-1(42-61), as well as by its V52-L53, M51-V52 reduced amide surrogates and partial-D substitutions in K48 and E49. In vivo tests revealed that reduced amide pseudopeptide-immunised Aotus monkeys induced neutralising antibodies specifically recognising the MSP-1 N-terminus region. These findings support the role of molecular conformation in malaria vaccine development.

Amino Acid Sequence↗
PubMed2003

MHC allele-specific binding of a malaria peptide makes it become promiscuous on fitting a glycine residue into pocket 6.

Peptide 1585 (EVLYLKPLAGVYRSLKKQLE) has a highly conserved amino-acid sequence located in the Plasmodium falciparum main merozoite surface protein (MSP-1) C-terminal region, required for merozoite entry into human erythrocytes and therefore represents a vaccine candidate for P. falciparum malaria. Original sequence-specific binding to five HLA DRB1* alleles (0101, 0102, 0401, 0701, and 1101) revealed this peptide's specific HLA DRB1*0102 allele binding. This peptide's allele-specific binding to HLA DRB1*0102 took on broader specificity for the DRB1*0101, -0401, and -1101 alleles when lysine was replaced by glycine in position 17 (peptide 5198: EVLYLKPLAGVYRSLKG(17)QLE). Binding of the identified G(10)VYRSLKGQLE(20) C-terminal register to these alleles suggests that peptide promiscuous binding relied on fitting Y(12), L(15), and G(17) into P-1, P-4, and P-6, respectively. The implications of the findings and the future of this synthetic vaccine candidate are discussed.

Alleles↗
PubMed2003

6746 SERA peptide analogues immunogenicity and protective efficacy against malaria is associated with short alpha helix formation: malaria protection associated with peptides alpha helix shortening.

Erythrocyte high activity binding peptides (HABPs) have been identified for the Plasmodium falciparum serine repeat antigen (SERA). HABP 6746, located in this protein's 50 kDa fragment had its critical binding residues replaced by amino acids having similar mass but different charge to change their immunologic properties. This peptide analogues were used to immunize Aotus monkeys that were challenged later on with a virulent P. falciparum strain to determine their protective efficacy. A shortening in alpha helix structure was found in the immunogenic and protective ones when their secondary structure was analyzed by NMR, to correlate their structure with their immunologic properties. These data, together with results from previous studies, suggest that this shortening in HABP helical configuration may lead to better fitting with immune system molecules, rendering them immunogenic and protective and therefore making them excellent candidates for consideration as components of a subunit based multicomponent synthetic vaccine against malaria.

Amino Acid Sequence↗
PubMed2003

Analysis of a Plasmodium falciparum EBA-175 peptide with high binding capacity to erythrocytes and their analogues using 1H NMR.

A 175-erythrocyte-binding protein (EBA-175) conserved high-activity binding peptide (HABP), called 1783 (nonimmunogenic, nonprotective against Plasmodium falciparum malaria), was analyzed for antigenic and protective activity in Aotus monkeys, together with several of its analogues. 1H NMR studies of peptides 17912, 14016, and 22814 allowed their structure to be related to their biological function. These peptides showed helical regions having differences in their position and length. Nonimmunogenic, nonprotective peptides 1783 and 17912 showed an extensive helical region, while the 22814 immunogenic protective peptide's alpha-helix was found in the N-terminal region. This suggests that the more flexible C-terminal region will allow better interaction between these peptides and immune system molecules as well as relating these peptides' three-dimensional structure to their immunogenicity and protective activity, thus leading to a more rational development of the new malaria multicomponent vaccine.

Amino Acid Sequence↗
PubMed2002

NMR structure of Plasmodium falciparum malaria peptide correlates with protective immunity.

Apical membrane antigen-1 is an integral Plasmodium falciparum malaria parasite membrane protein. High activity binding peptides (HABPs) to human red blood cells (RBCs) have been identified in this protein. One of them (peptide 4313), for which critical binding residues have already been defined, is conserved and nonimmunogenic. Its critical binding residues were changed for amino acids having similar mass but different charge to change such immunological properties; these changes generated peptide analogues. Some of these peptide analogues became immunogenic and protective in Aotus monkeys.Three-dimensional models of peptide 4313 and three analogues having different immune characteristics, were calculated from nuclear magnetic resonance (NMR) experiments with distance geometry and restrained molecular dynamic methods. All peptides contained a beta-turn structure spanning amino acids 7 to 10, except randomly structured 4313. When analysing dihedral angle phi and psi values, distorted type III or III' turns were identified in the protective and/or immunogenic peptides, whilst classical type III turns were found for the nonimmunogenic nonprotective peptides. This data shows that some structural modifications may lead to induction of immunogenicity and/or protection, suggesting a new way to develop multicomponent, subunit-based malarial vaccines.

Amino Acid Sequence↗
PubMed2002

Protection against experimental P falciparum malaria is associated with short AMA-1 peptide analogue alpha-helical structures.

Apical membrane antigen-1 (AMA-1) is an integral Plasmodium falciparum malaria parasite membrane protein. Peptides having high activity binding to human red blood cells have been identified in this protein. One of them, peptide 4325, with the amino acid sequence MIKSAFLPTGAFKADRYKSH, for which critical binding residues have already been defined (underlined), is conserved and non-immunogenic. Its critical binding residues were changed for amino acids having similar mass but different charge to change such immunological properties. These changes rendered some peptides immunogenic and protective against experimental challenge in Aotus monkeys. Three-dimensional models of peptide 4325 and its analogues, 20032 and 20034, were calculated from NMR experiments with distance geometry and restrained molecular dynamic methods. Non-immunogenic, non-protective peptide 4325 showed differences in its secondary structure with respect to protective, immunogenic peptides 20032 and 20034. Such data suggest that these modifications could have converted non-immunogenic peptides into immunogenic, protective ones, making them excellent candidates for a multi-component subunit synthetic malaria vaccine.

Amino Acid Sequence↗
PubMedDate not supplied

Immunogenicity and protectivity of Plasmodium falciparum EBA-175 peptide and its analog is associated with alpha-helical region shortening and displacement.

EBA-175 protein is used as a ligand in the binding of P. falciparum to red blood cells (RBCs). Evidence shows that the conserved peptide 1779 from this protein (with high red blood cell binding ability and known critical erythrocyte binding residues) plays an important role in the invasion process. This peptide is neither immunogenic nor protective; analogs having critical residues replaced by amino acids with similar volume or mass but different polarity were synthesized and inoculated into Aotus monkeys, and elicited different immunogenic and protective responses. Nuclear Magnetic Resonance (1H-NMR) studies revealed that peptide analog 21696 (non-immunogenic and non-protective) presents a large helical fragment, that the peptide 14012 (immunogenic and non-protective) helical fragment is smaller, while the peptide 22812 (immunogenic and protective) alpha-helix is shorter in a different region and possesses greater flexibility at its N-terminus. The presence of methionine residues could affect the structural stability of peptide 22812 and ultimately its immunological response. Our results suggest a new strategy for designing a new malaria multi-component subunit-based vaccine.

Amino Acid Sequence↗