Yolanda Silva
National University of Colombia
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Featured researches published by Yolanda Silva.
Vaccine | 1996
María V. Valero; Roberto Amador; J.J. Aponte; A. Narvaez; C. Galindo; Yolanda Silva; Jaiver Rosas; Fanny Guzman; Manuel E. Patarroyo
A double-blind randomized placebo-controlled field trial with the SPf66 malaria vaccine was carried out in an endemic area consisting of 14 small villages with exclusive fluvial access, in a rain forest area along the Rosario River, Colombia. A total of 1257 subjects completed the full three dose vaccination schedule on days 0, 30 and 180 (643 vaccinated group/623 placebo group) and were followed-up by passive and active surveillance over a period of 22 months. One hundred and thirty-four Plasmodium falciparum malaria episodes were detected (53 in vaccinated group/81 in placebo group), yielding an attack rate of 5.47 cases/100 person years of follow-up (pyears) in the vaccine group and 8.44/100 pyears in the placebo group. The estimated vaccine protective efficacy was 35.2% (95% CI 8.4-54.2%, P = 0.01). This result supports earlier findings that the SPf66 malaria vaccine diminishes the risk of infection by P. falciparum in endemic areas of South America.
Parasite Immunology | 1991
Manuel E. Patarroyo; Javier Vinasco; Roberto Amador; Fabiola Espejo; Yolanda Silva; Alberto Moreno; Mauricio Rojas; Ana Lucia Mora; Margarita Salcedo; Victoria Valero; Ana Karla Goldberg; Jorge Kalil
Summary Two independent vaccination trials using a hybrid synthetic poly pep‐tide containing epitopes from four proteins of Plasmodium falciparum were performed. In the first trial 63 and in the second 122 volunteers were vaccinated, using different immunization schedules. The analysis of the humoral response to the vaccine, measured by IgG antibody titres to the polypeptide showed a bimodal distribution in both cases suggesting genetic control of the immune response to this protein. There was a small group of low or non‐responders and a large group of good responders. HLA phenotyping of the two groups disclosed an association of the low responders to HLA‐DR4 antigens with chi‐square P value of 0.00039 when compared with the good responders group. These findings provide evidence for the genetic control of the immune response to the synthetic vaccine by the association of this response with particular alleles of the HLA class II antigens; such findings may lead to an explanation of the mechanism involved in disease susceptibility and need to be used in the design of a totally effective vaccine.
Vaccine | 2003
Adriana Y. Sierra; Carlos A. Barrero; Raul Rodriguez; Yolanda Silva; Camilo Moncada; Magnolia Vanegas; Manuel A. Patarroyo
Two E. coli expressed recombinant polypeptides (rPvMSP-1(14) and rPvMSP-1(20)) contained in the 33kDa fragment, located within Plasmodium vivax merozoite surface protein (PvMSP-1) 42kDa C-terminal region, and a cocktail of high reticulocyte binding synthetic peptides located within these fragments, were evaluated for immunogenicity and protective immune responses in splenectomised and spleen intact Aotus nancymaae monkeys. Thirty splenectomised monkeys who had been previously immunised with either rPvMSP-1(14), rPvMSP-1(20), or a mixture of both recombinant fragments were intravenously challenged with the heterologous P. vivax VCG-1 strain (as determined by DNA sequencing); full protection was observed in five monkeys and low parasitaemia levels were obtained in eight more monkeys. Splenectomised control monkey group rapidly developed high parasitaemia levels, while no significant parasitaemia was obtained in the non-splenectomised control group. Although PvMSP-1 42 and 33kDa fragments were recognised by Western Blot and whole parasites by IFAT when tested with immune monkey sera, no correlation between protection and antibody titres by IFAT and ELISA was observed, suggesting that protection is not being solely mediated by a humoral immune response. This data showed that partial protection against a heterologous strain challenge was best achieved when immunising with a rPvMSP-1(14)-rPvMSP-1(20) mixture (2 were fully protected and 4 with low parasitaemia out of 12) suggesting for the first time, that these fragments could be good candidates for inclusion in a P. vivax multi-stage, multi-antigen vaccine.
Biological Chemistry | 2003
José Manuel Lozano; Martha Patricia Alba; Magnolia Vanegas; Yolanda Silva; José Libardo Torres-castellanos; Manuel Patarroyo
Abstract Merozoite Surface Protein-1 (MSP-1) has been considered as a malaria vaccine candidate. It is processed during the Plasmodium falciparum invasion process of red blood cells (RBCs). A conserved MSP-1 C-terminal peptide was identified as a high-activity erythrocyte binding peptide (HAEBP) termed 1585. Since conserved HAEBPs are neither antigenic nor immunogenic we decided to assess the significance of a single peptide bond replacement in 1585. Thus, two pseudopeptides were obtained by introducing a ψ[CH2-NH] reduced amide isoster into the 1585 critical binding motif. The pseudopeptides bound to different HLA-DR alleles, suggesting that backbone modifications affect MHC-II binding patterns. Pseudopeptide antibodies inhibit in vitro parasite RBC invasion by recognizing MSP-1. Each pseudopeptide-induced antibody shows distinct recognition patterns. 1H-NMR studies demonstrated that isoster bonds modulate the pseudopeptides structure and thus their immunological properties, therefore representing a possible subunit malaria vaccine component.
Angewandte Chemie | 2001
Fabiola Espejo; Marcia Cubillos; Luz Mary Salazar; Fanny Guzman; Mauricio Urquiza; Marisol Ocampo; Yolanda Silva; Raul Rodriguez; Eduardo Lioy; Manuel E. Patarroyo
FEBS Journal | 2003
Mary Helena Torres; Luz Mary Salazar; Magnolia Vanegas; Fanny Guzman; Raul Rodriguez; Yolanda Silva; Jaiver Rosas; Manuel E. Patarroyo
Biochemistry | 2005
Manuel Patarroyo; Martha Patricia Alba; Luis Eduardo Vargas; Yolanda Silva; Jaiver Rosas; Raul Rodriguez
Vaccine | 2005
Carlos A. Barrero; Gabriela Delgado; Adriana Y. Sierra; Yolanda Silva; Carlos Parra-López; Manuel A. Patarroyo
Protist | 2013
Darwin A. Moreno-Pérez; Rafael Areiza-Rojas; Ximena Flórez-Buitrago; Yolanda Silva; Manuel E. Patarroyo; Manuel A. Patarroyo
Biochemical and Biophysical Research Communications | 2005
José Manuel Lozano; Fabiola Espejo; Ricardo Vera; Luis Eduardo Vargas; Jaiver Rosas; Liliana Patricia Lesmes; Elizabeth Torres; Jimena Cortes; Yolanda Silva; Manuel E. Patarroyo