ABSTRACT
Plasmodium falciparum can invade all stages of red blood cells, while Plasmodium vivax can invade only reticulocytes. Although many P. vivax proteins have been discovered, their functions are largely unknown. Among them, P. vivax reticulocyte binding proteins (PvRBP1 and PvRBP2) recognize and bind to reticulocytes. Both proteins possess a C-terminal hydrophobic transmembrane domain, which drives adhesion to reticulocytes. PvRBP1 and PvRBP2 are large (> 326 kDa), which hinders identification of the functional domains. In this study, the complete genome information of the P. vivax RBP family was thoroughly analyzed using a prediction server with bioinformatics data to predict B-cell epitope domains. Eleven pvrbp family genes that included 2 pseudogenes and 9 full or partial length genes were selected and used to express recombinant proteins in a wheat germ cell-free system. The expressed proteins were used to evaluate the humoral immune response with vivax malaria patients and healthy individual serum samples by protein microarray. The recombinant fragments of 9 PvRBP proteins were successfully expressed; the soluble proteins ranged in molecular weight from 16 to 34 kDa. Evaluation of the humoral immune response to each recombinant PvRBP protein indicated a high antigenicity, with 38-88% sensitivity and 100% specificity. Of them, N-terminal parts of PvRBP2c (PVX_090325-1) and PvRBP2 like partial A (PVX_090330-1) elicited high antigenicity. In addition, the PvRBP2-like homologue B (PVX_116930) fragment was newly identified as high antigenicity and may be exploited as a potential antigenic candidate among the PvRBP family. The functional activity of the PvRBP family on merozoite invasion remains unknown.
Subject(s)
Female , Humans , Middle Aged , Epitopes, B-Lymphocyte/chemistry , Immunodominant Epitopes/chemistry , Malaria, Vivax/immunology , Plasmodium vivax/chemistry , Protein Structure, Tertiary , Protozoan Proteins/chemistry , Reticulocytes/parasitologyABSTRACT
The gag gene of HIV-1 encodes a single open reading frame of 55 kDa that contains three subdomains: the matrix domain (p17), the capsid domain (p24) and the nucleocapsid domain (p15). The p24 and p17 proteins have a predominant a-helical structure and perform important functions throughout thevirallife-cycle. The determination of gag-specific antibodies is important because declining titers of these antibodies herald clinical deterioration.In this work we present the results obtained on immunoreactiviy of synthetic peptides that mimic immunogenic a-helical regions of p24 and p17. The influence on the immunoreactivity of structural modifications in native sequences, including the addition of non immunogenic side chains: AAAC- and -CAAA on both side of minimal epitopes was evaluated in indirect and competitive enzymeimmunoassays. The conformational characteristcs to the peptides were analysed by circular dichroism and these results were correlated with that obtained in the immunoassays. It was shown that the reactivity of peptides mimicking short a-helical regions of p24 and p17 is improved by adding short non immunogenic chains on both N- and C- terminus. These modifications enhanced the immobilization of the peptides onto the solid support and allowed more accesibility to the minimal epitopes byspecific antibodies, in solution.
El gen gag del VIH-1 codifica una región de 55kDA que contiene tres subdominios: matriz (p17), cápside (p24) y nucleocápside (p15). Las proteínas p24 y p17 tienen una estructura predominante helicoidal y cumplen un rol importante en el ciclo de vida del virus. En este trabajo presentamos los resultados de inmunorreactividad de péptidos sintéticos que imitan regiones helicoidales de p24 y p17. Utilizando enzimoinmunoensayos se evaluó la influencia de modificaciones en las secuencias nativas sobre la capacidad de reconocimiento de anticuerpos específicos en solución y en fase sólida, incluyendo el agregado de cadenas no inmunogénicas en ambos extremos de los epitopes mínimos. La conformación de los péptidos se determinó por dicroísmo circular y los resultados se correlacionaron con los de inmunorreactividad. Se observó que la capacidad de reconocimiento de anticuerpos por péptidos pequeños que imitan estructuras helicoidales de p24 y p17 mejoró con el agregado de cadenas no inmunogénicas en ambos extremos de los epitopes. Estas modificaciones mejoran la inmovilización sobre las superficies sólidas y permiten una mayor accesibilidad de los anticuerpos a los epitopes mínimos en solución.
Subject(s)
Humans , Antigen-Antibody Reactions , Enzyme-Linked Immunosorbent Assay/methods , Gene Products, gag/immunology , HIV Antibodies/immunology , HIV Antigens/immunology , /immunology , HIV-1 , Molecular Mimicry , Peptide Fragments/immunology , Viral Proteins/immunology , Amino Acid Sequence , Amino Acid Substitution , Circular Dichroism , gag Gene Products, Human Immunodeficiency Virus , Gene Products, gag/chemistry , HIV Antibodies/isolation & purification , HIV Antigens/chemistry , /chemistry , HIV Infections/blood , HIV Infections/immunology , Immunodominant Epitopes/chemistry , Immunodominant Epitopes/immunology , Molecular Sequence Data , Protein Binding , Protein Conformation , Protein Structure, Secondary , Protein Structure, Tertiary , Peptide Fragments/chemical synthesis , Solutions , Viral Proteins/chemistryABSTRACT
Three monospecific antibodies MSAb 1, MSAb 2 and MSAb 3 were raised in BALB/C mice against respective antigens. M. smegmatis whole cell lysate was first separated on SDS-PAGE and randomly chosen bands were cut and then used for immunization. Antibodies were collected as ascites by injecting mice with myeloma cell line P3X63 Ag 658.4. All the three antibodies showed high reactivity with denatured antigens compared to native. Different extent of cross-reactivity was observed as evident from ELISA. MSAb1 recognized a 75 kDa immunodominant antigen from M. smegmatis and 66 kDa from M. tuberculosis (H37Ra), respectively. An apparently similar molecular weight antigen shown to be present in M. tuberculosis (H37Ra) an avirulent strain and BCG, but not recognized by MSAb1. The 75 kDa antigen has a stimulatory effect on T-cell proliferation.