Antimalarial pyronaridine resistance may be associated with elevated MDR-1 gene expression profiles but not point mutation in Plasmodium berghei ANKA isolates

The selection of resistance is inevitable whenever chemotherapy is necessary for pathogen control. Notably, Plasmodium falciparum has developed multifaceted means to overcome the toxicity of nearly all antimalarial medicines. To bypass this challenge, not only should novel drugs be developed, but the resistance mechanisms to new and existing drugs need should be fully explored. Pyronaridine is a companion drug in Pyramax®, a blend of artesunate (ASN)-pyronaridine (PRD) which is the WHO prequalified alternative for malaria treatment in the African setting. However, half-life mismatch predisposes the PRD to swift emergence of resistance especially in high malaria transmission settings. However, there are no well-characterized PRD-resistant parasite lines. Previously, stable PRD- resistant P. berghei ANKA lines were selected by in vivo drug pressure and preliminary results showed cross-resistance with quinolines, therefore, hypothetically the activity of PRD and chloroquine or other quinolines may be comparable, hence, the resistance mechanisms may be parallel. Consequently, genetic polymorphisms and expression profiles of PbMDR-1 that could be associated with pyronaridine resistance were examined by PCR amplification, sequencing and transcript quantification by RT-qPCR. The transcripts level increased during resistance selection while translated PbMDR-1 sequence alignment of PRD-sensitive and PRD-resistant was the same, the expression may be linked to PRD resistance but not mutations.   Key words: Quinolines, malaria, Pyronaridine, Pyramax®, resistance, expression, MDR-1 gene.