Chromosome size polymorphisms in plasmodium falciparum can involve deletions and are frequent in natural parasite populations

Corcoran, Lynn M.; Forsyth, Karen P.; Bianco, A. E.; Brown, Graham V.; Kemp, David J.

doi:10.1016/0092-8674(86)90487-3

Cited by 165 publications

(69 citation statements)

References 35 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Transmission to the mosquito vector and passage through the mosquito stages were not affected by deletion of either P52 or P36. Furthermore, although loss of gametocyte production and transmissibility has been reported after prolonged culture of P. falciparum (29,30), the selection procedure for cytoadherence we used to minimize loss of chromosome ends (31) appeared to have circumvented this problem.…”

Section: Discussionmentioning

confidence: 99%

Preerythrocytic, live-attenuated Plasmodium falciparum vaccine candidates by design

VanBuskirk

O'Neill

Vega

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

155

150

View full text Add to dashboard Cite

Falciparum malaria is initiated when Anopheles mosquitoes transmit the Plasmodium sporozoite stage during a blood meal. Irradiated sporozoites confer sterile protection against subsequent malaria infection in animal models and humans. This level of protection is unmatched by current recombinant malaria vaccines. However, the live-attenuated vaccine approach faces formidable obstacles, including development of accurate, reproducible attenuation techniques. We tested whether Plasmodium falciparum could be attenuated at the early liver stage by genetic engineering. The P. falciparum genetically attenuated parasites (GAPs) harbor individual deletions or simultaneous deletions of the sporozoiteexpressed genes P52 and P36. Gene deletions were done by double-cross-over recombination to avoid genetic reversion of the knockout parasites. The gene deletions did not affect parasite replication throughout the erythrocytic cycle, gametocyte production, mosquito infections, and sporozoite production rates. However, the deletions caused parasite developmental arrest during hepatocyte infection. The double-gene deletion line exhibited a more severe intrahepatocytic growth defect compared with the single-gene deletion lines, and it did not persist. This defect was assessed in an in vitro liver-stage growth assay and in a chimeric mouse model harboring human hepatocytes. The strong phenotype of the double knockout GAP justifies its human testing as a whole-organism vaccine candidate using the established sporozoite challenge model. GAPs might provide a safe and reproducible platform to develop an efficacious whole-cell malaria vaccine that prevents infection at the preerythrocytic stage.genetically attenuated parasites ͉ malaria vaccine ͉ P36 ͉ P52 ͉ sporozoite M alaria is a formidable global health problem, affecting 300 million to 500 million people worldwide annually (1). The resulting Ϸ1 million deaths per year are mainly caused by Plasmodium falciparum infections. Eradication of malaria will in large part depend on an effective vaccine that prevents infection by Plasmodium, but such a vaccine has remained elusive. The parasites' preerythrocytic stages, encompassing the mosquito-inoculated sporozoites and liver stages that develop from sporozoites after their invasion of hepatocytes, are attractive targets for antiinfection vaccines, because at this stage the number of infected host cells is low, and further transmission of the parasite is not yet possible. Occurrence of blood-stage infection after sporozoite challenge is completely preventable by immunization with radiation-attenuated sporozoites in mouse models of malaria (2). This was a landmark finding that set the standards for malaria preerythrocytic vaccine development. Radiation-attenuated sporozoites arrest in development during hepatocyte infection, but their safety and efficacy are dependent on a precise irradiation dose. Humans immunized with P. falciparum radiation-attenuated sporozoites have been effectively protected from subsequent challenge with homologous an...

show abstract

Section: Discussionmentioning

confidence: 99%

Preerythrocytic, live-attenuated Plasmodium falciparum vaccine candidates by design

VanBuskirk

O'Neill

Vega

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

155

150

View full text Add to dashboard Cite

show abstract

“…Subtelomeric deletions in cultured isolates are known to result in the loss of a number of functional genes of Plasmodium falciparum (1)(2)(3)(4)(5)(6)(7). To examine whether this phenomenon occurs in nature or is an artifact of growth in vitro, we used two-dimensional pulsed-field gradient electrophoresis (PFGE) to examine chromosomal DNA from fresh field isolates.…”

mentioning

confidence: 99%

Subtelomeric chromosome deletions in field isolates of Plasmodium falciparum and their relationship to loss of cytoadherence in vitro.

Biggs

Kemp

Brown

1989

Proc. Natl. Acad. Sci. U.S.A.

100

View full text Add to dashboard Cite

Subtelomeric deletions are responsible for the loss of expression of several Plasmodium falciparum antigens, including the knob-associated histidine-rich protein (KAHRP). Such deletions are detectable by two-dimensional pulsed-field gradient electrophoresis (PFGE) in which the chromosomes separated in dimension 1 are cleaved with Apa I, and the sizes of telomeric fragments are determined in dimension 2. This sensitive technique has enabled us to examine the role of subtelomeric deletions in two aspects of the biology of Plasmodium falciparum. First, we show that similar subtelomeric deletions to those that occur in vitro also occur in field isolates. Second, we demonstrate a correlation between subtelomeric deletions and loss of the phenotype of "cytoadherence" in cultured isolates. Subclones were generated from the cytoadherent cloned isolate ItG2F6, and their phenotypes were examined with respect to cytoadherence, the expression of "knobs," and agglutination of infected erythrocytes with rabbit antiserum. The only chromosomal change detectable by two-dimensional PFGE among subclones that differ from wild type in each of these three characteristics is a deletion of approximately 100 kilobases at one end of chromosome 2. This deletion includes the gene coding for KAHRP and the subtelomeric repeat designated rep20.Subtelomeric deletions in cultured isolates are known to result in the loss of a number of functional genes of Plasmodium falciparum (1-7). To examine whether this phenomenon occurs in nature or is an artifact of growth in vitro, we used two-dimensional pulsed-field gradient electrophoresis (PFGE) to examine chromosomal DNA from fresh field isolates. This technique allows resolution of telomeric fragments after digestion of separated chromosomes with the restriction endonuclease Apa I. It relies on the observation that a conserved complex consisting of telomeric repeats, an Apa I site(s), and a block of rep20 subtelomeric repeats is common to all chromosomes of P. falciparum (Fig.

show abstract

“…Approximately 20-µL pieces of agarose blocks of chromosomal DNA (∼30 µg/mL) prepared from purified sporozoites Shirley 1994), were digested overnight with 30 units of a restriction endonuclease (GIBCO BRL), as described by Corcoran et al (1986) and Shirley (1994) by using conditions and 50-100 µL of the buffers recommended by the supplier.…”

Section: Southern Hybridization Of Rflpsmentioning

confidence: 99%

A Genetic Linkage Map of the Apicomplexan Protozoan Parasite Eimeria tenella

Shirley¹,

Harvey²

2000

Genome Res.

View full text Add to dashboard Cite

Apicomplexan protozoan parasites have complex life cycles that involve phases of asexual and sexual reproduction. Some genera have intermediate insect hosts, for example, Plasmodium spp. (the cause of malaria), but related genera such as Eimeria spp. (causative agents of coccidiosis in poultry) have a direct life cycle occurring in only a single host. Mechanisms that regulate the life cycles of apicomplexan parasites are unknown, but the intracellular growth of avian Eimeria spp. is easily shortened by serial selection for the first parasites to complete the transition from asexual to sexual reproduction (to yield so-called precocious lines). To investigate the genetic basis of such an abbreviated life cycle, we have used the species E. tenella and analyzed the inheritance of 443 polymorphic DNA markers in 22 recombinant cloned progeny derived from a cross between parents that had selectable phenotypes of precocious development or resistance to an anticoccidial drug. The markers were placed in 16 linkage groups (which defined 12 chromosomes) and a further 57 unlinked groups. Two linkage groups showed an association (P = .0105) with the traits of precocious development or drug-resistance and were mapped to chromosome 2 (ca 1.2 Mbp) and chromosome 1 (ca 1.0 Mbp), respectively. The map provides a framework for further studies on the identification of genetic loci implicated in the regulation of the life cycle of an important protozoan parasite and a representative of a major taxonomic group.[A table with the segregation data is available as an online supplement at http://www.genome.org.]

show abstract

Chromosome size polymorphisms in plasmodium falciparum can involve deletions and are frequent in natural parasite populations

Cited by 165 publications

References 35 publications

Preerythrocytic, live-attenuated Plasmodium falciparum vaccine candidates by design

Preerythrocytic, live-attenuated Plasmodium falciparum vaccine candidates by design

Subtelomeric chromosome deletions in field isolates of Plasmodium falciparum and their relationship to loss of cytoadherence in vitro.

A Genetic Linkage Map of the Apicomplexan Protozoan Parasite Eimeria tenella

Contact Info

Product

Resources

About