Mutant/mutation
The mutant expresses a mutated form of the circumsporozoite protein (CS). It expresses a hybrid P. berghei/P. falciparum CS in which the P. berghei CS repeat region  was exchanged with the P. falciparum CS repeat region.

Protein (function)
The CS protein is the major protein on the surface of sporozoites and is critical for development of sporozoites within the oocysts and is involved in motility and invasion of both the salivary gland of the mosquito and the liver cells. The protein is also found on the oocyst plasma membrane and on the inner surface of the oocyst capsule. Specific motifs in CS are involved in sporozoite binding to mosquito salivary glands and in sporozoite attachment to heparan sulfate proteoglycans in the liver of the mammalian host. During substrate-dependent locomotion of sporozoites, CS is secreted at the sporozoite anterior pole, translocated along the sporozoite axis and released on the substrate at the sporozoite posterior pole. Following sporozoite invasion of hepatocytes, the CS is released in the host cell cytoplasm.

Phenotype
The phenotype analysis shows that P. berghei CS bearing the P. falciparum CS repeat region can complement the wild type P. berghei CS protein, although the mutant sporozoites show a reduced salivary gland invasion.
Monoclonal and polyclonal Abs to the P. falciparum repeats neutralize the infectivity to HepG2 cells in vitro of the mutant sporozoites and infectivity to the C57Bl/6 mice was strongly reduced when mice were treated with mAbs against  the P. falciparum repeats. Mice immunized with the  P. falciparum (T1B)4 MAP vaccine  are protected against challenge with the mutant sporozoites.
This mutant has been used in a 'transgenic sporozoite neutralization assay (TSNA)'  to test the inhibition of sporozoite invasion of HepG2 cells by sera obtained from humans immunized with (T1B)4 MAP, a peptide vaccine containing P. falciparum CS repeats (Kumar et al., 2004, J. Immunol. Methods 292, 157-64).

Other mutants
A P. berghei mutant has been generated that lacks expression of CS (RMgm-9) .
A P. berghei mutant has been generated that produces reduced levels of CS (RMgm-72).
P. berghei mutants have been generated with a mutated GPI-anchor addition sequence (RMgm-73).
A P. berghei mutant has been generated in which the endogenous P. berghei CS was replaced with P. falciparum CS (RMgm-69).
Two P. berghei mutants have been generated that express mutated forms of P. falciparum CS (RMgm-70 with a mutated Region I; RMgm-71 with a mutated Region II).
A P. berghei mutant has been generated in which the endogenous P. berghei CS was replaced with P. gallinaceum CS (RMgm-74).
A P. berghei mutant has been generated in which the endogenous P. berghei CS was replaced with P. yoelii CS (RMgm-75).