Immunogenicity of multiple antigen peptides containing Plasmodium vivax CS epitopes in BALB/c mice

Multiple antigen peptide systems (MAPs) allow the incorporation of various epitopes in to a single synthetic peptide immunogen. We have characterized the immune response of BALB/c mice to a series of MAPs assembled with different B and T cell epitopes derived from the Plasmodium vivax circumsporozoite (CS) protein. A B-cell epitope from the central repeat domain and two T-cell epitopes from the amino and carboxyl flanking regions were used to assembled eight different MAPs. An additional universal T cell epitope (ptt-30) from tetanus toxin protein was included. Immunogenicity in terms of antibody responses and in vitro T lymphocyte proliferation was evaluated. MAPs containing B and T cell epitopes induced high titers of anti-peptides antibodies, which recognized the native protein on sporozoites as determined by IFAT. The antibody specificity was also determined by a competitive inhibition assay with different MAPs. A MAP containing the B cell epitope (p11) and the universal epitope ptt-30 together with another composed of p11 and the promiscuous T cell epitope (p25) proved to be the most immunogenic. The strong antibody response and specificity for the cognate protein indicates that further studies designed to assess the potential of these proteins as human malaria vaccine candidates are warranted.

Naturally acquired antibodies against the major merozoite surface coat protein (MSP-1) of Plasmodium falciparum acquired by residents in an endemic area of Colombia

A preliminary baseline epidemiological malaria survey was conducted in the village of Punta Soldado, Colombia. Parasite prevalence and density as well as serological data were obtained from 151 asymptomatic children and adults. Fifty individuals were infected with Plasmodium falciparum. The mean parasite density was 184 parasites/mm3. Greater than 90 of the sample population were P. falciparum antibody positive as detected by the indirect immunofluorescent antibody test (IFAT). The enzyme-linked immunosorbent assay (ELISA) was used to detect antibodies against the major merozoite surface protein (MSP-1) of P. falciparum. In this population, anti-MSP-1 antibody concentration is acquired in an age dependent manner with equal immunogenicity to both the N- and C-terminal regions of the molecule. Infection at the time of sampling was associated with a higher anti-MSP-1 antibody concentration than that found in non-infected individuals. Further studies are planned to assess the role of immune and non-immune factors in limiting the number of cases of severe malaria seen in this population.

Efficience of human Plasmodium falciparum malaria vaccine candidates in Aotus lemurinus monkeys

The protective efficacy of several recombinat and a synthetic Plasmodium falciparum protein was assessed in Aoutus monkeys. The rp41 aldolase, the 190L fragment of the MSA-1 protein and fusion 190L-CS. T3 protein containg the CS. T3 helper "universal epitope were emulsified in Freund's adjuvants and injected 3 times in groups of 4-5 monkeys each one. The synthetic polymer Spf (66)30 also emulsified in Freund's adjuvants was injected 6 times. Control groups for both experiments were immunized with saline solution in the same adjuvant following the same schedules. Serology for malaria specific antibodies showed seroconversion in monkeys immunized with the recombinant proteins but not in those immunized with the polymer nor in the controls. Challenge was performed with the 10 (elevado a quinta potência) parasites from the P. falciparum FVO isolate. Neither rp41 nor SPf (66)30 induced protection, whereas 190L induced significant delay of parasitemia. The fusion of the CS. T3 epitope to 190L significantly increased is protective capacity

Uso de la tecnica inmuno-radiometrica (IRMA) en Anopheles de Colombia para la identificacion de esporozoitos de Plasmodium / Use of the immuno-radiometric technique (IRMA) in the colombian Anopheles for identification of Plasmodium sporozoites

El metodo inmuno-radiometrico (IRMA) que utiliza anticuerpos monoclonales con especificidad por la proteina CS de los esporozoitos de Plasmodium falciparum, se uso en el presente trabajo para determinar las tasas de infeccion de mosquitos del genero Anopheles (obtenidos en diversas regiones endemicas malaricas de Colombia). De las especies estudiadas, A.albimanus, A.darlingi, A.alloph y A.neomaculipalpus mostraron infecciones por P.falciparum. Solo las dos primeros habian sido incriminadas previamente como vectoras. Adicionalmente, A.albimanus fue el unico positivo para P.vivax. El metodo IRMA permitio en un corto tiempo y sobre un numero reducido de mosquitos determinar algunos probables vectores en el pais

Capacidad inhibidora del crecimiento intraeritrocitico del Plasmodium falciparum en sueros de areas malaricas / Inhibitory capability of intraeritrocitic growth of Plasmodium falciparum in serum from malaric areas

Se describe el fenomeno de inhibicion del crecimiento intraeritrocitico de Plasmodium falciparum in vitro producido por factores solubles de tipo no anticuerpo presentes en el suero de individuos de areas malaricas de la costa pacifica colombiana, fenomeno denominado "crisis". Se determinaron en sueros de 80 individuos, los titulos de anticuerpos antimalaricos por la tecnica de inmunofluorescencia indirecta y la capacidad inhibitora del crecimiento intraeritrocitico del parasito por el metodo de incorporacion de hipoxantina radiomarcada