title: Factors regulating natural transmission of Plasmodium berghei to the mosquito vector, and the cloning of a transmission-blocking immunogen.
abstract: Naturally occurring factors that regulate the infectivity of P. berghei infected rodent hosts to the mosquito vector in vivo have been compared in T.O., Balb/C and immunodeficient SCID mice. No detectable differences in infectivity were observed suggesting B and T cell mediated factors are not involved. Further studies investigated roles for macrophage colony stimulating factors, the cytokines IFN gamma and TNF alpha, of neutrophils, and of nitric oxide in the SCID mouse, but have failed to demonstrate an important role in vivo for any factor examined. Differences between these results and those obtained in vitro on the human and primate parasites must therefore be explained by biological differences between the parasite/host combinations, or by technical differences in experimental designs. Induced immunity to the ookinete surface antigen Pbs 21 of P. berghei can totally block the transmission of the parasite from the gametocyte infected host to the vector. We have cloned the gene encoding Pbs 21 and shown it bears striking structural similarities to Pfs 25, Pgs 25 and more particularly Pgs 28 in that it has a high cysteine content (9.5%), 4 EGF-like domains and hydrophobic amino-'signal'--and carboxyl-'anchor' sequences. The encoding gene is on chromosome 5 and is found also in P. chabaudi, P. yoelii and P. vinckei.
authors.affiliation: Department of Biology, Imperial College, London, U.K.
authors.forename: R E
authors.initials: RE
authors.lastname: Sinden
authors.forename: G C
authors.initials: GC
authors.lastname: Barker
authors.forename: M J
authors.initials: MJ
authors.lastname: Paton
authors.forename: S L
authors.initials: SL
authors.lastname: Fleck
authors.forename: G A
authors.initials: GA
authors.lastname: Butcher
authors.forename: A
authors.initials: A
authors.lastname: Waters
authors.forename: C J
authors.initials: CJ
authors.lastname: Janse
authors.forename: M H
authors.initials: MH
authors.lastname: Rodriguez
mesh_terms: D000594:Amino Acid Oxidoreductases / Q000037:antagonists & inhibitors; D000595:Amino Acid Sequence; D000818:Animals; D000852:Anopheles / Q000469:parasitology*; D000953:Antigens, Protozoan / Q000235:genetics / Q000276:immunology*; D001120:Arginine / Q000031:analogs & derivatives / Q000494:pharmacology; D001483:Base Sequence; D003001:Cloning, Molecular; D016384:Consensus Sequence; D018076:DNA, Complementary / Q000235:genetics; D016054:DNA, Protozoan / Q000235:genetics; D005260:Female; D006790:Host-Parasite Interactions; D007303:Insect Vectors / Q000469:parasitology*; D008070:Lipopolysaccharides / Q000494:pharmacology; D008288:Malaria / Q000150:complications / Q000276:immunology / Q000469:parasitology / Q000635:transmission*; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C / Q000276:immunology / Q000469:parasitology; D016513:Mice, SCID / Q000276:immunology / Q000469:parasitology; D008969:Molecular Sequence Data; D019001:Nitric Oxide Synthase; D016366:Open Reading Frames; D010961:Plasmodium / Q000235:genetics; D010962:Plasmodium berghei / Q000276:immunology / Q000502:physiology*; D015800:Protozoan Proteins / Q000235:genetics / Q000276:immunology*; D012098:Reproduction; D016511:Severe Combined Immunodeficiency / Q000150:complications; D013045:Species Specificity; D019323:omega-N-Methylarginine
chemical_list: D000953:Antigens, Protozoan; D018076:DNA, Complementary; D016054:DNA, Protozoan; D008070:Lipopolysaccharides; D015800:Protozoan Proteins; C084246:ookinete surface antigen Pbs21, Plasmodium; D019323:omega-N-Methylarginine; D001120:Arginine; D019001:Nitric Oxide Synthase; D000594:Amino Acid Oxidoreductases