Mutant/mutation
In the mutant (CS^5MΔP1-2) the wild type cs gene is replaced with a mutated cs gene carrying 5 mutations that changed the natural H-2K^d restricted epitope SYIPSAEKI to SIINFEKL, an H-2K^b restricted epitope. In addition, the Pexel/VTS motifs of the cs gene are mutated (he conserved arginine and leucine were mutated to alanine; see also mutant RMgm-286 for a P. berghei mutant expressing a cs gene with  similar mutated Pexel/vTS motifs).

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
See additional information.

Additional information
Two mutants have been analysed in this study:
1) The CS^5M mutant (RMgm-613) in which  the wild type cs gene is replaced with a mutated cs gene carrying 5 mutations that changed the natural H-2K^d restricted epitope SYIPSAEKI to SIINFEKL, an H-2K^b restricted epitope;
2) The CS^5MΔP1-2 which, in addition to the mutated cs gene with the SIINFEKL H-2K^b epitope, contains mutations in the Pexel/VTS motifs of the cs gene.

Phenotype analyses of both mutants revealed the following:
Phenotype analyses of sporozoites of these mutants provide evidence that both dendritic cells (DCs) and hepatocytes CS epitopes must reach the cytosol and use the TAP transporters to access the ER.
In addition evidence is presented that in DCs, CS is cross-presented via endosomes while, conversely, in hepatocytes the CS protein must be secreted directly into the cytosol. These observations suggests that the main targets of protective CD8+ T cells are parasite proteins exported to the hepatocyte cytosol.
Secretion of the CS protein into hepatocytes was not dependent upon parasite-export (Pexel/VTS) motifs in this protein (see also mutant
Phenotype analyses of another mutant with similarly mutated Pexel/VTS motifs had indicated CS export to the hepatocyte cytosol was eliminated in the absence of  functional Pexel/VTS motifs (see mutant RMgm-286). Sporozoites of both mutants that express CS with mutated Pexel/VTS motifs show reduced infectivity.

Other mutants
RMgm-613: A mutant (CS^5M) in which the wild type cs gene is replaced with a mutated cs gene carrying 5 mutations that changed the natural H-2K^d restricted epitope SYIPSAEKI to SIINFEKL, an H-2K^b restricted epitope
RMgm-286: A mutant expressing CS with mutated Pexel/VTS motifs (the conserved arginine and leucine mutated to alanine by site directed mutagenesis).