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Updated: Jul 22, 2026
Protocol for Production of a Genetic Cross of the Rodent Malaria Parasites
Published on: January 3, 2011
A genetic investigation of virulence in a rodent malaria parasite
Abstract:
The genetic basis of virulence in a line (YM) of Plasmodium yoelii yoelii was investigated in a cross with a mild line (A/C). The blood forms of the virulent line developed extensively in mature erythrocytes of mice, causing death of the host within 7 days; infections with the mild line were normally restricted to reticulocytes, infected animals recovering after three weeks. Lines YM and A/C differed additionally in enzyme and drug-sensitivity markers. Studies on infections established from each line alone from sporozoite mixtures of the two lines and from the cross between the lines showed that the appearance of virulence had been caused by a genetic change in the parasite, and not by other factors such as a concurrent infection with another organism. An analysis of the characters of 56 clones derived from the cross showed that the virulence character had undergone recombination with the other markers, and appeared to be inherited in Mendelian fashion. Three clones exhibited atypical virulence, although it was not clear whether this had been produced by genetic recombination.
Insights
Genetic factors determine Plasmodium yoelii yoelii virulence. A cross between virulent (YM) and mild (A/C) lines revealed virulence is heritable and undergoes genetic recombination, impacting parasite pathogenicity.
Area of Science:
- Genetics
- Parasitology
- Immunology
Background:
- Virulence in Plasmodium yoelii yoelii varies significantly between parasite lines.
- The virulent YM line causes rapid, fatal infections in mice by targeting mature erythrocytes, while the mild A/C line primarily infects reticulocytes, allowing host recovery.
Purpose of the Study:
- To investigate the genetic basis of virulence in Plasmodium yoelii yoelii.
- To determine if virulence is a heritable trait and if it undergoes genetic recombination.
Main Methods:
- A genetic cross was performed between a virulent (YM) and a mild (A/C) Plasmodium yoelii yoelii line.
- Infections were established from parental lines, sporozoite mixtures, and the F1 cross progeny.
- Phenotypic analysis of 56 clones derived from the cross, assessing virulence, erythrocyte tropism, enzyme markers, and drug sensitivity.
Main Results:
- The study confirmed that virulence in Plasmodium yoelii yoelii is caused by a genetic change within the parasite, not external factors.
- Analysis of 56 clones showed that the virulence trait recombined with other genetic markers and followed Mendelian inheritance patterns.
- Three clones displayed atypical virulence, suggesting potential complex genetic interactions or recombination events.
Conclusions:
- Virulence in Plasmodium yoelii yoelii is a genetically determined trait.
- The virulence gene(s) in Plasmodium yoelii yoelii are subject to genetic recombination and Mendelian inheritance.
- Further research is needed to elucidate the genetic mechanisms behind atypical virulence phenotypes.
