Mallick, P. K. | bioRxiv Science

bioRxiv2024

Erythrocytic plasma membrane calcium ATPase (PMCA4b) variations mediate redox imbalance to determine artemisinin sensitivity in malaria

Artemisinin resistance in Plasmodium falciparum remains a major public health challenge for the ongoing malaria elimination programs. Till now, artemisinin resistance is linked with the variations in the genome of P. falciparum which are mainly clustered in the Pfkelch13 gene. Several studies reported artemisinin resistance in the malaria endemic areas without finding any evidence of genetic variation in parasite for this occurrence. This study interrogated whether host genetic variations have any association with artemisinin sensitivity of malaria parasite. We investigated the relationship of 1) genetic variations in the human ATP2B4 gene and 2) the resultant surface expression of plasma membrane calcium ATPase (PMCA4b) with the intraerythrocytic levels of calcium, reactive oxygen species (ROS) and the resistance towards artemisinin in the intraerythrocytic parasite. This study found negative correlation of PMCA4b expression level with intraerythrocytic calcium and ROS levels. Further in-vitro growth assays revealed that artemisinin sensitivity is reduced in the parasites growing within the RBCs having low PMCA4b and high oxidative stress. Overall, this study highlights the strong association of host PMCA4b in cellular calcium mediated redox imbalance, which significantly contributes to artemisinin resistance in malaria parasite. Hence, this is the first study to document the effect of host variations on artemisinin sensitivity of the parasite. We further emphasize that many redox modulating RBC polymorphisms that are prevalent in malaria endemic areas could influence artemisinin resistance and can serve as potential biomarkers for predicting therapeutic response. Thus, detailed population specific research may provide new insights for personalized malaria treatment and may inform future drug development strategies. SignificanceThe human host and malaria parasite share a closely interconnected relationship hence host variations could influence parasite drug resistance. This study demonstrates that reduced PMCA4b expression, the primary calcium efflux pump in RBCs, significantly increases the erythrocytic calcium and reactive oxygen species (ROS) levels, thereby decreasing the P. falciparum growth as well as artemisinin sensitivity. Many ROS inducing RBC polymorphisms, such as sickle cell, thalassemia, G6PD deficiency, PMCA4b variations etc. have emerged as strong malaria protective traits in several studies in malaria endemic areas. But these traits could also influence artemisinin resistance and can serve as potential biomarkers for predicting therapeutic response and highlights the importance of host erythrocytes oxidative microenvironment surveillance in monitoring antimalarial drug resistance.

microbiology↗

bioRxiv2022

Molecular tools for early detection of invasion of malaria vector Anopheles stephensi

There are increasing reports of the expansion of the Asian malaria vector Anopheles stephensi in new geographical areas posing a threat to the elimination of urban malaria. Efficient surveillance of this vector in affected areas and early detection in new geographical areas is key for the containment and control of this species. To overcome the practical difficulties associated with the morphological identification of immature stages and adults of An. stephensi, a species-specific PCR and a Real-Time PCR assay were developed for their identification targeting a unique segment of ITS2 lacking homology to any other organism. Both PCRs can be used to identify An. stephensi individually or in pooled samples of mixed species, including when present in extremely low proportion. This study also reports a method for selective amplification and sequencing of An. stephensi for their confirmation in pooled samples of mixed species.

molecular biology↗

bioRxiv2022

First report of classical knockdown resistance (kdr) mutation, L1014F, in human head louse Pediculus humanus capitis (Phthiraptera: Anoplura)

There are at least three known knockdown resistance (kdr) mutations reported globally in the human head louse Pediculus humanus capitis (Phthiraptera: Anoplura) that are associated with reduced sensitivity to pyrethroids. However, prevalence of kdr mutation is not known in the Indian subcontinent. To identify kdr mutations in the Indian population, the genomic region of the voltage-gated sodium channel gene encompassing IIS1-2 linker to IIS6 segments was PCR-amplified and sequenced from P. humanus capitis samples collected from different geographic localities of India. DNA sequencing revealed the presence of four kdr mutations, i.e., M827I, T929I, L932F and L1014F. The presence of a classical kdr mutation, L1014F, a most widely reported mutation across insect-taxa associated with kdr-trait, is being reported for the first time in P. humanus capitis.

molecular biology↗