Primaquine (PQ) is an essential antimalarial drug but despite being developed over 70 years ago, its mode of action is unclear. Here, we demonstrate that hydroxylated-PQ metabolites (OH-PQm) are responsible for efficacy against liver and sexual transmission stages of Plasmodium falciparum . The antimalarial activity of PQ against liver stages depends on host CYP2D6 status, whilst OH-PQm display direct, CYP2D6-independent, activity. PQ requires hepatic metabolism to exert activity against gametocyte stages. OH-PQm exert modest antimalarial efficacy against parasite gametocytes; however, potency is enhanced ca.1000 fold in the presence of cytochrome P450 NADPH:oxidoreductase (CPR) from the liver and bone marrow. Enhancement of OH-PQm efficacy is due to the direct reduction of quinoneimine metabolites by CPR with the concomitant and excessive generation of H 2 O 2 , leading to parasite killing. This detailed understanding of the mechanism paves the way to rationally re-designed 8-aminoquinolines with improved pharmacological profiles.

Human infections due to the monkey malaria parasite Plasmodium knowlesi are increasingly being reported from Malaysia. The parasite causes high parasitaemia, severe and fatal malaria in humans thus there is a need for urgent measures for its control. The MSP4 is a potential vaccine candidate, which is well studied in Plasmodium falciparum and Plasmodium vivax; however, no study has been conducted in the orthologous gene of P. knowlesi. In this study, we investigated the level of polymorphisms, haplotypes, natural selection and population structure of full-length pkmsp4 in 32 clinical samples from Malaysian Borneo along with 4 lab-adapted strains. We found low levels of polymorphism across the gene with exon I showing higher diversity than the exon II. The C- terminal epidermal growth factor (EGF) domains and GPI-anchored region within exon II were mostly conserved with only 2 non-synonymous substitutions. Although 21 amino acid haplotypes were found, the frequency of mutation at the majority of the polymorphic positions was low. We found evidence of negative selection at the exon II of the gene indicating existence of functional constraints. Phylogenetic haplotype network analysis identified shared haplotypes and indicated geographical clustering of samples originating from Peninsular Malaysia and Malaysian Borneo. High population differentiation values were observed within parasite populations originating from Malaysian Borneo (Kapit, Sarikei and Betong) and laboratory-adapted strains obtained from Peninsular Malaysia and Philippines indicating distinct population structure. This is the first study to genetically characterize the full-length msp4 gene from clinical isolates of P. knowlesi from Malaysia and thus would be very useful for future rational vaccine studies. Further studies with higher number of samples and functional characterization of the protein will be necessary.

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Malaria is a major public health concern, and any tangible intervention during the pre-elimination phase can result in a significant reduction in infection rates. Recent studies have reported that antigens producing cross-protective immunity can play an important role as vaccines and halt malaria transmission in different endemic regions. In this study, we studied the genetic diversity, natural selection, and discovered novel conserved epitopes of a high molecular weight rhoptry protein 2 (RhopH2) in clinical samples of Plasmodium knowlesi and Plasmodium vivax cross-protective domains, which has been proven to produce cross-protective immunity in both species. We found low levels of nucleotide diversity (P. knowlesi; π ~ 0.0093, SNPs = 49 and P. vivax π ~ 0.0014, SNPs = 23) in P. knowlesi (n = 40) and P. vivax (n = 65) samples in the PkRhopH2 cross-protective domain. Strong purifying selection was observed for both species (P. knowlesi; dS - dN = 2.41, p < 0.009, P. vivax; dS - dN = 1.58, p < 0.050). In silico epitope prediction in P. knowlesi identified 10 potential epitopes, of which 7 epitopes were 100% conserved within clinical samples. Of these epitopes, an epitope with 10 amino acids (QNSKHFKKEK) was found to be fully conserved within all P. knowlesi and P. vivax clinical samples and 80%–90% conservation within simian malaria ortholog species, i.e., P. coatneyi and P. cynomolgi. Phylogenetic analysis of the PkRhopH2 cross-protective domain showed geographical clustering, and three subpopulations of P. knowlesi were identified of which two subpopulations originated from Sarawak, Malaysian Borneo, and one comprised only the laboratory lines from Peninsular Malaysia. This study suggests that RhopH2 could be an excellent target for cross-protective vaccine development with potential for outwitting strain as well as species-specific immunity. However, more detailed studies on genetic diversity using more clinical samples from both species as well as the functional role of antibodies specific to the novel conserved epitope identified in this study can be explored for protection against infection.

BACKGROUNDZika virus (ZIKV) is a teratogenic flavivirus that can cause microcephaly. Its main vector, Aedes aegypti, has been previously identified in Saudi Arabia, but no ZIKV infection has yet been reported. Nevertheless, the country is at risk from ZIKV because it receives many travelers throughout the year, including pilgrims from ZIKV-endemic countries.OBJECTIVESScreen asymptomatic pregnant mothers and their newborns attending a major hospital in the Najran region for subclinical or past infections with ZIKV, using ELISA and RT-PCR.DESIGNCross-sectional.SETTINGNajran Maternity and Children Hospital (NMCH).SUBJECTS AND METHODSAll pregnant women admitted to NMCH in labor between November 2016 and July 2017 were included in the study. Clinical and demographic data were collected by pre-validated physician-administered questionnaires. Paired umbilical and maternal serum samples were collected and frozen at −60°C, using ELISA to measure anti-ZIKA IgG and IgM antibodies and RT-PCR to further investigate positive samples.MAIN OUTCOME MEASURESMaternal and newborn serum anti-ZIKV IgM and IgG and ZIKV RT-PCR.SAMPLE SIZE410 mother-newborn pairs.RESULTSThe median gestational age was 38.5 weeks (range 33–42). Most (n=342, 83.41%) of the women were from Najran city. All of the newborns had normal growth parameters with no congenital malformations. None of the mothers had symptoms suggestive of ZIKV infection; 3 (0.7%) exhibited a low-grade fever (38°C), but did not test positive for anti-ZIKV antibodies. Thirty-five (8.53%) of mothers had travelled inside Saudi Arabia, but none outside the country. Twenty-four (5.85%) mothers tested positive for anti-ZIKV IgM and 52 (12.68%) tested positive for anti-ZIKV IgG, but all infant samples were negative. All seropositive ZIKV IgM were also ZIKV IgG positive, but RT-PCR testing of all seropositive samples was negative.CONCLUSIONAlthough previous (resolved) ZIKV infection and cross-reactivity of the ELISA method with other flaviviruses cannot be excluded, the study found no confirmed cases of acute ZIKV infection. However, given the presence of the vector in Saudi Arabia, the presence of presumptive positive serology and the ongoing risk of ZIKV entry via a regular influx of travelers from endemic areas, we propose that continuous surveillance be conducted for ZIKV as well for other flaviviruses. Larger-scale nationwide studies are strongly recommended to gain a broader view of the potential threat from ZIKV in the country.LIMITATIONSSmall sample size, unavailability of plaque reduction neutralization tests to confirm serology results, and RT-PCR was only conducted on ELISA-positive serum samples, due to resource constraints.

Targeted chemotherapy remains the primary choice in controlling various forms of breast cancer (BC) due to its heterogenous gene expressions in various subtypes. In silico and in vitro evaluation of ICY-5, a novel arylidene analogue against c-MET, was performed. ICY-5 exhibited a docking score of −9.6 kcal/mol in inactive conformation and, − 8.6 kcal/mol in active conformation for c-MET. ICY-5 inhibited c-MET enzyme with an IC 50 of 34.34 nM. The compound effectively inhibited MDA-MB 231 and MCF-7 cell proliferation, with GI 50 values of 62.61 and 75.31 nM, respectively, and hepatocyte growth factor (HGF)/R c-MET phosphorylation with IC 50 s of 71.41 and 83.77 nM, respectively. ICY-5 dose-dependently inhibited HGF-induced transmigration, cell scattering, invasion and altered cell cycle. An increase in apoptotic populations of these cells, with a dose-dependent decease in phosphorylation of STAT3 protein was observed. Furthermore, ICY-5 upregulated the caspase-3, caspase-9, Bcl-2-associated X and survivin, and downregulated Bcl-2, vascular endothelial growth factor, matrix metalloproteinase-2 (MMP-2), and MMP-9 in both BC cell lines. In summary, ICY-5 exhibited excellent efficacy in BC cells, targeting c-MET/SAT-3-mediated mitochondrial apoptosis. Further research will be required to ascertain ICY-5 suitability as a targeted chemotherapeutic against multiple forms of BC.

Antibiotic resistance is rising across the world. For a very long time, bitter ginger (Zingiber zerumbet) has been used as one of the most popular herbal remedies to treat a wide range of common diseases. Ginger has been shown to have antioxidant and antibacterial activity. It has various bioactive chemicals that might be utilized as an alternative treatment option for many infectious diseases. The present study aimed to examine the biochemical profile of ginger, antioxidant, and antibacterial activity against selective endodontic microbes. Antioxidant was measured using DPPH and antibacterial activity was performed using disk diffusion tests. Streptococcus mutants, Enterococcus faecalis, Staphylococcus spp., and Lactobacillus spp. were tested for antibacterial activity. Before evaluating the dried extracts, all solvents were eliminated using rotary evaporation. The obtained IC50 value revealed that ethanol extract had the greatest antioxidant activity. Concerning each bacterium, the plant extracts demonstrated considerable antibacterial activity (p = .001). Ethanol extracts showed the strongest antibacterial activity against the studied microorganisms. This study highlights that the Zingiber zerumbet (Z. zerumbet) is a strong antibacterial herb against multidrug‐resistant (MDR) gram‐positive bacteria. It may also be employed as a possible natural antioxidant source.

Anthroponotic cutaneous leishmaniais (ACL) and zoonotic cutaneous leishmaniasis (ZCL) caused by Leishmania tropica and Leishmania major, respectively, are endemic vector-borne diseases in southern Saudi Arabia. In 2021, an outbreak of cutaneous leishmaniasis occurred in the province of Asir. The main objective of our investigation was to analyze the epidemiological features of CL in southern Saudi Arabia. The ministry of health recorded 194 CL patients between January and December 2021 from the Asir province. Our findings showed that the majority of CL patients (87.1%) originated from the governorates of Khamis-Mushait and Abha. Most of the patients were males (62.3%). While CL affected all age groups, those under 13 years old were the most affected (38.1%). For both genders, CL patients were mostly Saudi citizens (90.7%) compared to non-Saudi expatriates. The majority of CL patients (75.2%) suffered from a single lesion, and the majority of lesions (61.3%) were located on the face. The seasonal prevalence of CL showed two peaks, a small one in July–August and a larger one in March. Of a total of 194 Giemsa slides samples, 188 showed positive amplification of Leishmania ITS1 gene. Based on PCR-RFLP and PCR-HMR, 183 patients showed positive amplification of L. tropica and five patients showed positive amplification of L. major. Phylogenetic analysis revealed a clear distinct separation between L. major and L. tropica sequences. Our results provided strong evidence of the pre-domination of L. tropica, the main etiological agent of ACL in Asir province. We reported for the first time the presence of L. major, an etiological agent of ZCL in the study areas. The co-circulation of ACL and ZCL highlighted the complexity of the epidemiology of CL in southern Saudi Arabia, and subsequently, further studies to identify competent vectors and reservoir hosts for the establishment of control strategies are needed.