Development, Characterization and Immunogenicity of a Multi-Stage, MultivalentPlasmodium falciparumVaccine Antigen (FALVAC-1A) Expressed inEscherichia coli

A synthetic multistage, multi-epitope Plasmodium falciparum malaria antigen (FALVAC-1A) was designed and evaluated in silico, and then the gene was constructed and expressed in Escherichia coli. The FALVAC-1A protein was purified by inclusion body isolation, followed by affinity and ion exchange chromatography. Although FALVAC-1A was a synthetic antigen, it folded to a specific, but as yet incompletely defined, molecular conformation that was stable and comparable from lot to lot. When formulated with four different adjuvants, FALVAC-1A was highly immunogenic in rabbits, inducing not only ELISA reactivity to the cognate antigen and most of its component epitopes, but also in vitro activity against P. falciparum parasites as demonstrated by inhibition of sporozoite invasion, antibody dependent cellular inhibition and the immunofluorescence assay.

Poor housing quality increases risk of rodent infestation and Lassa fever in refugee camps of Sierra Leone

Lassa fever, a viral hemorrhagic fever endemic in parts of West Africa, is a severe febrile illness transmitted to humans by the rodent Mastomys natalensis. To determine risk of Lassa fever in households in Sierra Leonean refugee camps, we analyzed the spatial relationships between households with a Lassa case and focal locations of potential rodent habitats. Quality and hygiene factors of households were assessed to determine possible risk factors for household rodent infestation and occurrence of Lassa fever. The odds to have a rat burrow were higher in case houses than in control houses (OR 24, 95% CI 6.0-93). Case houses scored significantly worse in the quality of housing and external hygiene. These findings suggest that risk of Lassa fever in refugee camps depends on individual housing quality and the hygiene of the immediate surrounding environment.

Placental malaria diminishes development of antibody responses to Plasmodium falciparum epitopes in infants residing in an area of western Kenya where P. falciparum is endemic

To determine the effect of placental malaria (PM) infection on the development of antibody responses to malaria in infants, we measured immunoglobulin G levels to seven different Plasmodium falciparum epitopes by using plasma samples collected at monthly intervals from infants born to mothers with and without PM. Overall, PM was associated with diminished antibody levels to all of the epitopes tested, especially with infants aged >or=4 to 12 months, and the difference was statistically significant for four of the seven epitopes (P<0.0035). These findings suggest that PM can negatively influence the development of immune responses to malaria in infants.