Disruption of plasmepsin-4 and merozoites surface protein-7 genes in Plasmodium berghei induces combined virulence-attenuated phenotype

Abstract

Blood stage malaria parasites causing a mild and self limited infection in mice have been obtained with either radiation or chemical mutagenesis showing the possibility of developing an attenuated malaria vaccine. Targeted disruption of plasmepsin-4 (pm4) or the merozoite surface protein-7 (msp7) genes also induces a virulence-attenuated phenotype in terms of absence of experimental cerebral malaria (ECM), delayed increase of parasitemia and reduced mortality rate. The decrease in virulence in parasites lacking either pm4 or msp7 is however incomplete and dependent on the parasite and mouse strain combination. The sequential disruption of both genes induced remarkable virulence-attenuated blood-stage parasites characterized by a self-resolving infection with low levels of parasitemia and no ECM. Furthermore, convalescent mice were protected against the challenge with P. berghei or P. yoelii parasites for several months. These observations provide a proof-of-concept step for the development of human malaria vaccines based on genetically attenuated blood-stage parasites.

Transcriptomic profiling of microglia reveals signatures of cell activation and immune response, during experimental cerebral malaria

“…To monitor the integrity of the blood brain barrier during experimental ECM, groups of control and PbA-infected C57BL/6 were injected intravenously with 0.1 ml of 2% Evan’s Blue dye in sterile phosphate-buffered saline (PBS) 6 days post infection47. The dye was allowed to circulate for 2 h, and then the mice were sacrificed, systematically perfused with 10 mL PBS and the brains were isolated and photographed.…”

Whole organism blood stage vaccines against malaria

“…Protection was observed in mice subsequently challenged with homologous or heterologous parasites. Further work with virulence attenuated parasites involved the sequential disruption of both the Plasmepsin-4 and Merozoite Surface Protein-7 genes, resulting in a parasite whose virulence attenuation was greater than either of the individual knockout strains [37]. Inoculation with these double knockout parasites also resulted in a self-resolving infection (in some mice there was a reduction in peak parasitemia), failure to induce ECM in susceptible mice and induction of strong homologous and heterologous protection when recipient mice were challenged.…”

Aspartyl Proteinases of Eukaryotic Microbial Pathogens: From Eating to Heating

“…In particular, the virulence-attenuated, plasmepsin IV-deleted strain of P . berghei , an agent of murine malaria, has been suggested as a blood-stage, whole-cell vaccine [23–24]. The plasmepsins’ redundancy and consequent stringent requirements for their use of molecular targets of new plasmodial inhibitors has been critically discussed [9].…”