Successful sporozoite challenge model in human volunteers with Plasmodium vivax strain derived from human donors.

Successful establishment of a Plasmodium vivax sporozoite challenge model in humans is described. Eighteen healthy adult, malaria-naïve volunteers were randomly allocated to Groups A-C and exposed to 3 +/- 1, 6 +/- 1, and 9 +/- 1 bites of Anopheles albimanus mosquitoes infected with P. vivax, respectively. Seventeen volunteers developed signs and symptoms consistent with malaria, and geometric mean prepatent periods of 11.1 days (9.3-11) for Group A; 10.8 days (9.8-11.9) for Group B; and 10.6 days (8.7-12.4) for Group C, with no statistically significant difference among groups (Kruskal-Wallis, P = 0.70). One volunteer exposed to eight mosquito bites did not develop a parasitemia. No differences in parasite density were observed and all individuals successfully recovered after anti-malarial treatment. None of the volunteers developed parasite relapses within an 18-month follow-up. In conclusion, malaria-naive volunteers can be safely and reproducibly infected with bites of 2-10 An. albimanus mosquitoes carrying P. vivax sporozoites. This challenge method is suitable for vaccine and anti-malarial drug testing.

Hemoglobin levels related to days of illness, race, and Plasmodium species in Colombian patients with uncomplicated malaria.

Prevalence of malaria-related anemia in disease-endemic regions of the American continents has been poorly studied. We describe the relationships between hemoglobin level and race, Plasmodium species, and days of illness in 150 Colombian patients with uncomplicated malaria diagnosed by thick blood smear. Hemoglobin was measured at admission and a standardized questionnaire was used to determine days of illness and other variables. Associations between hemoglobin and the variables were estimated and adjusted according to the other covariates using regression analysis. Plasmodium falciparum and P. vivax were found in similar proportions and mild anemia was present in 50% of the patients. Volunteers were classified as Afro-Colombians (61%) and non-Afro-Colombians (39%). An inverse relationship between hemoglobin and days of illness was identified, and a statistical interaction was found between race and P. falciparum infection in determining the hemoglobin concentration. These observations could guide the design of research to better understand malarial anemia.

Antibody response to Plasmodium vivax antigens in Fy-negative individuals from the Colombian Pacific coast.

The Duffy antigen (Fy) is necessary for Plasmodium vivax invasion of human erythrocytes. Some populations have a highly prevalent Fy-negative phenotype; such persons are naturally protected from P. vivax blood infection but are expected to completely support the P. vivax pre-erythrocytic cycle, representing a valuable model for studying the immune response during these parasitic stages. We typed 214 individuals, mostly Afro-Colombians, from a P. vivax-endemic area for Fy expression and determined the antibody response to P. vivax pre-erythrocytic (sporozoites and CS) and blood-stage antigens (blood forms, P. vivax merozoite surface protein 1, and P. vivax Duffy binding protein [PvDBP]). Antibody titers to P. vivax circumsporozoite protein, P11, and N-terminal peptides and the number of responders were similar in Fy-negative and Fy-positive individuals. The number of responders to sporozoites, blood forms, and PvDBP were different between these groups. Thus, Fy-negative individuals from malaria-endemic areas can be used to study the immune response to the P. vivax liver phase without interference of the erythrocytic cycle.

Restricted genetic diversity of Plasmodium falciparum major merozoite surface protein 1 in isolates from Colombia.

The merozoite surface protein 1 (MSP-1) gene of Plasmodium falciparum encodes a major immune target under development as a malaria vaccine. In this study, we typed MSP-1 variable regions of parasites obtained from Buenaventura, Colombia. Four MSP-1 gene types were detected corresponding to prototype and recombinant K1 and MAD20 block 4 sequences. In contrast to variability within block 4, blocks 2, 6, and 16-17 corresponded exclusively to the MAD20 allelic type. Most (80%) blood samples contained multiple MSP-1 gene types. The presence of four MSP-1 variants within block 4 against a MAD20 background indicates that current P. falciparum populations in Buenaventura are derived from parasites expressing K1 and MAD20 alleles, some of which underwent two recombination events within or flanking block 4. Restricted MSP-1 diversity appears to be relatively stable in Buenaventura and suggests that selection has resulted in the dominance of the MAD20 type in most of the polymorphic blocks with the exception of block 4.

Immune responses to Plasmodium vivax pre-erythrocytic stage antigens in naturally exposed Duffy-negative humans: a potential model for identification of liver-stage antigens.

Duffy antigen is the receptor used by Plasmodium vivax to invade erythrocytes. Consequently, individuals lacking Duffy antigen [Fy(-)] do not develop blood-stage infections. We hypothesized that naturally exposed Fy(-) humans may develop immune responses mainly to pre-erythrocytic stages and could be used to study acquired immunity to P. vivax and to identify liver-stage antigens. We report here that antibody and IFN-gamma responses to known sporozoite antigens were significantly induced by natural exposure in Fy(-) humans, whereas responses to blood-stage antigens were significantly induced in Fy(+) humans. IFN-gamma responses to sporozoite antigens were lower in Fy(+) than in Fy(-) humans, indicating that in Fy(+) humans blood-stage infections may have suppressed T cell responses to pre-erythrocytic stages. We evaluated the immune responses to 18 novel P. vivax homologs of P. falciparum sporozoite proteins identified from the P. vivax genome sequence. Eight proteins recalled IFN-gamma responses in P. vivax-exposed but not in unexposed individuals. Of these, 3 antigens elicited IFN-gamma responses in Fy(-) but not in Fy(+) individuals. These results suggest that differential immune responses observed in naturally exposed Fy(-) and Fy(+) individuals can be exploited to identify P. vivax stage-specific antigens.

Identification of HLA-A2 restricted CD8(+) T-lymphocyte responses to Plasmodium vivax circumsporozoite protein in individuals naturally exposed to malaria.

Specific CD8(-) T-lymphocyte (CTL) activity against Plasmodium pre-erythrocytic stages (P-ES) derived antigens is considered one of the most important mechanisms for malaria protection. Plasmodium vivax is the second most prevalent human malaria parasite species distributed worldwide. Although several CTL epitopes have been identified in Plasmodium falciparum P-ES derived antigens, none has been described for P. vivax to date. In this study, we analysed HLA-A*0201 specific CD8(-) T-lymphocyte responses to the P. vivax circumsporozoite (CS) protein in both malaria exposed and non-exposed populations from the Colombian Pacific Coast. First, we analysed the prevalence of HLA-A2 allele in the study populations and found that approximately 38 of the individuals expressed this molecule and that 50 of them were HLA-A*0201. We then selected, on the P. vivax CS, five peptide sequences containing the HLA-A*0201 binding motifs and used the corresponding synthetic peptides to evaluate the CD8(-) T-lymphocyte interferon (IFN)-gamma response. Peripheral blood mononuclear cells from the HLA-A*0201 donors were in vitro stimulated with these peptides and IFN-gamma production was determined by an ELISPOT assay. Specific CD8(-) T-lymphocyte responses were detected for three peptides located in the C-terminal region of the protein. Specific responses to these peptides were also detected in several individuals expressing different HLA-A*02 subtypes. The potential of these peptides to induce specific cytolysis and that of long synthetic peptides comprising these epitopes as P. vivax malaria vaccine subunits are being studied.

Caracterización de la transmisión de Plasmodium malariae en cuatro regiones colombianas endémicas de malaria / Characterization of Plasmodium malariae transmission in four malaria endemic regions in Colombia

En Colombia, la detección del número de casos de infección por Plasmodium malariae muestra una distribución porcentual focalizada en la Costa Pacífica, donde alcanza un 95 por ciento, en contraste con el 5 por ciento de casos más esporádicos que se presentan en otras regiones. El departamento del Valle del Cauca aporta el 85 por ciento y el 15 por ciento restante corresponde a los departamentos de Chocó y Cauca. La región de Zacarías aporta el 70 por ciento, seguida por las regiones de Citronela, Puerto Merizalde, Anchicayá, Meseta y Boca Dagua, regiones que conjuntamente contribuyen con el 30 por ciento. En un estudio transversal, realizado en 1997 mediante gota gruesa en la población de Zacarías, se encontró una frecuencia de 9,1 por ciento de casos de P. malariae. Se usaron muestras de donantes infectados con gametocitos de P. malariae para alimentar mosquitos Anopheles albimanus y reproducir exitosamente el ciclo ex vivo. Se analizaron 242 plasmas obtenidos de individuos de Zacarías y Punta Soldado (Valle) y Pizarro (Chocó) para determinar la presencia de anticuerpos específicos para P. malariae. Se encontró que el 9,1 por ciento contenía anticuerpos identificables por la técnica de Elisa contra una preparación cruda de antígeno y que el 42,1 por ciento presentaba anticuerpos contra el péptido sintético (NAAG) derivado de la proteína circumesporozoíto (CS). En 50 muestras analizadas de la región del Bajo Guaviare, se encontró presencia de anticuerpos contra (NAAG) en el 16 por ciento. Los resultados de este estudio muestran una gran delimitación de los casos de la Costa Pacífica, el área de Zacarías, indicando también la posible presencia de este parásito en otras regiones del país

Aislamiento de bacterias aeróbicas patógenas de secreción conjuntival de niños / Isolation of pathogen aeribic bacteria from conjuntival secretion of children / Annual Reports 1992

The presence of microbial organisms in conjunctival secretions always raises the doubt of whether they are the result of contamination or a real infection. Culture records of conjunctival secretion from children, who attended the Laboratory of Microbiology of the Instituto de Investigaciones en Ciencias de la Salud and the consulting roon of the Hospital de Clinícas from January 1990 to July 1992, were analyzed to determine the most frequent infectious agenis. The most commonly microorganism foud was Staphylococcus aureus (36.4 percent of the cases), followed by Streptococcus viridans (21.2 percent), Streptococcus pneumoniae (15 percent) pseudomonas aeruginosa (9 percent) and Neisseria gonorroheae (6 peecent). Nor Haemophilus influenzae neither fungi were detected

Estudio microbiológico de una infección causada por un cáteter permanente en un niño / Annual Reports 1992 / Microbiologic study of an infection caused by a permannet catheter in a child

Microbiologic study were done on a sample isolated from the end of a catheter used in a child who had devepoped acute bacterial meningitis after several admissons to hospital. The isolate was identified as Klebsiella pneumoniae which showed a remarkable multiresistance to the most common antibiotics used in hospitals

Estudio etiológico de infección de secrecion endocervical en un grupo de alto riesgo (prostistutas) / Annual Reports 1991 / Study on the etiology of infections of endocervical secretions in a high risk group (prostitutes)

In order to determine the incidence and the etiology of the sexually trasnmitted diseaes (STD) 500 women, belonging to a high risk group (prostitutes), were studied from August, 1989 to Octuber 1990, and bacteriological and mycological studied were performed. Also, a questionnaire comprising detailed sexual behavior were rendered. High incidence of Gardnerella vaginalis (41.4 percent), Neisseria gonorrhoeae (12.2 percent), Trichomonas vaginalis (10.2 percent) and Candida albicans (10 percent) were found, in contrast with the low level found for Lactobacillus sp. The questinnaire revealed very low utilization of contraceptives as well as condom employement