Prevalence and temporal changes of mutations linked to anti-malarial drug resistance in Plasmodium falciparum and Plasmodium vivax in Palawan, Philippines

Molecular surveillance of antifolate drug resistance markers in Plasmodium vivax from Khyber Pakhtunkhwa province, northwest Pakistan

The emergence and spread of antimalarial drug resistance pose significant challenges in the fight against malaria. Mutations in dihydrofolate reductase (DHFR) and dihydropteroate synthetase (DHPS) in Plasmodium vivax are associated with sulfadoxine-pyrimethamine (SP) drug resistance. This study assessed SP resistance status in P. vivax isolates collected in Khyber Pakhtunkhwa province, Pakistan, by analyzing mutations in pvdhfr and pvdhps. Both genes were successfully amplified concurrently from 112 Pakistan P. vivax isolates. Sequence analysis of pvdhfr indicated that mutations F57L, S58R, and S117N were present with frequencies of 0.9 %, 31.3 %, and 46.4 %, respectively. The predominant wild-type haplotype F57S58T61S117 was identified in 51.8 % of samples, whereas mutant haplotypes were also detected: F57R58T61N117 (29.5 %), F57S58T61N117 (16.9 %), F57R58T61S117 (0.9 %), and L57R58T61S117 (0.9 %). In pvdhps, the sole mutation A383 G was found at a low frequency of 1.8 %, leading to a mutant haplotype S382G383K512A553V585. The integrated analysis of pvdhfr and pvdhps haplotypes showed that the wild-type haplotype was the most prevalent (50.9 %), followed by mutant haplotypes F57R58T61N117/ S382A383K512A553V585 (28.6 %) and F57S58T61N117/S382A383K512A553V585 (16.9 %). These findings indicate a relatively low level of antifolate resistance in Pakistan P. vivax isolates, suggesting that Pakistan P. vivax may still be amenable to SP treatment. Nevertheless, the persistence of similar mutation rates and patterns associated with SP resistance in the Pakistan pvdhfr and pvdhps populations, despite the absence of current SP pressure, underscores the importance of ongoing monitoring of SP resistance in the Pakistan P. vivax population.

Advancing artemisinin resistance monitoring using a high sensitivity ddPCR assay for Pfkelch13 mutation detection in Asia

The spread of Pfkelch13 mutations in Southeast Asia threatens the effectiveness of artemisinin-based combination therapies (ACTs) for malaria. Previous studies revealed a high prevalence of key mutations, including C580Y, P574L, and R561H, emphasizing the need for the surveillance to combat drug resistance. This study, we developed a droplet digital PCR (ddPCR) assay for the rapid screening of common mutations including P441L, Y493H, P527H, G538V, R539T, I543T, R561H, P574L, C580Y, and A675V. The assay was designed to detect minor populations of mutant strain within multiple infection, offering high sensitivity and specificity using artificial mixtures of mutant and wild-type alleles. Field samples collected in Thailand during 2015-2020 and in 2023 (N = 130) were also analyzed to validate the assay in a real-world setting. The ddPCR assay demonstrated exceptional performance, with 100% sensitivity and 90% specificity. The R539T, R561H, and C580Y mutations were detected in clinical samples collected from several study sites in Thailand. Notably, the R561H mutation was detected in 100% of the P. falciparum isolates from Mae Hong Son, Thailand in 2023, underscoring the assay's utility in identifying critical mutations associated with drug resistance. Moreover, ddPCR can detect multiple parasite populations in clinical samples and can be used to analyze the ratios of wild-type and mutant alleles. These results validate the assay's ability to serve as a powerful tool for the early detection of minor allele frequencies, facilitating the timely implementation of interventions to curb the spread of ACT resistance. The ddPCR assays developed in this study provide a sensitive and specific method for detecting Pfkelch13 mutations, allowing the identification of minor parasite populations with artemisinin resistance. These assays enhance our ability to monitor and respond to malaria drug resistance, offering a crucial tool for early detection and contributing to global malaria elimination efforts.

Comparative efficacy of sulphadoxine-pyrimethamine and dihydroartemisinin-piperaquine against malaria infection during late-stage pregnancy in mice

The introduction of artemisinin combination therapies (ACTs) against malaria infections opened up a window of possibilities to combat malaria in pregnancy. However, the usefulness of ACTs in all stages of pregnancy must be critically assessed. This study was designed to evaluate dihydroartemisinin-piperaquine (DHAP) as a suitable alternative to sulphadoxine-pyrimethamine (SP) in the treatment of malaria during third-trimester pregnancy in mice. Experimental animals were inoculated with a parasitic dose of 1x10⁶Plasmodium berghei (ANKA strain) infected erythrocytes and randomly allocated into treatment groups. The animals received standard doses of chloroquine alone (CQ)[10 mg/kg], SP [25 mg/kg] and [1.25 mg/kg] and DHAP [4 mg/kg] and [18 mg/kg] combinations. Maternal and pupil survival, litter sizes, pup weight and still-births were recorded, while the effect of the drug combinations on parasite suppression, recrudescence and parasite clearance time were evaluated. The day 4 chemo-suppression of parasitemia by DHAP in infected animals was comparable to SP, and CQ treatment (P > 0.05). The mean recrudescence time was significantly delayed (P = 0.031) in the DHAP treatment group compared to the CQ treatment group, while, there was no recrudescence in animals treated with SP. The birth rate in the SP group was significantly higher than in the DHAP group (P < 0.05). There was 100% maternal and pup survival in both combination treatments comparable with the uninfected gravid controls. The overall parasitological activity of SP against Plasmodium berghei in late-stage pregnancy appeared better than DHAP. In addition, SP treatment resulted in better birth outcomes assessed compared to DHAP treatment.

Chloroquine regulates the proliferation and apoptosis of palate development on mice embryo by activating P53 through blocking autophagy in vitro

Cleft lip and palate is one of the most frequent congenital developmental defects. Autophagy is a highly conserved process of cell self-degradation in eukaryotes, involving multiple biological processes in which chloroquine (CQ) is the most common inhibitor. However, whether CQ affects and how it affects palate development is unknown. Mouse embryonic palatal cells (MEPCs) were treated with CQ to observe cell viability, apoptosis, migration, osteogenic differentiation by cell proliferation assay, flow cytometric analysis, scratch assay, and alizarin red staining. PI staining was used to measure cell cycle distribution. Immunofluorescence (IF) assay and transmission electron microscopy were used to detect autophagosomes. The autophagy-related factors (LC3 and P62), apoptosis-related markers (P53, caspase-3 cleaved caspase-3, BAX, and BCL-2), and cell cycle-related proteins (P21, CDK2, CDK4, cyclin D1, and cyclin E) were all measured by western blot. CQ inhibited the proliferation of MEPCs by arresting the G0/G1 phase of the cell cycle in a concentration- and time-dependent manner with cell cycle-related proteins P21 upregulated and CDK2, CDK4, cyclin D1, and cyclin E downregulated. Then we detected CQ also induced cell apoptosis in a dose-dependent manner by decreasing the BCL-2/BAX ratio and increasing cleaved caspase-3. Next, it was investigated that migration and osteogenesis of MEPCs decreased with CQ treatment in a dose-dependent manner. Meanwhile, CQ blocked the autophagy pathway by upregulating LC3II and P62 expressions which activated the P53 pathway. CQ activates P53 which affects MEPC biological characteristics by changing the proliferation and apoptosis of MEPCs through inhibiting autophagy.