Population genetic structure of the Plasmodium vivax circumsporozoite protein (Pvcsp) in Sri Lanka

Molecular methods elucidate evolutionary and ecological processes in parasites, where interaction between hosts and parasites enlighten the evolution of parasite lifestyles and host defenses. Population genetics of Plasmodium vivax parasites accurately describe transmission dynamics of the parasites and evaluation of malaria control measures. As a first generation vaccine candidate against malaria, the Circumsporozoite Protein (CSP) has demonstrated significant potential in P. falciparum. Extensive polymorphism hinders the development of a potent malaria vaccine. Hence, the genetic diversity of Pvcsp was investigated for the first time in 60 Sri Lankan clinical isolates by obtaining the nucleotide sequence of the central repeat (CR) domain and examining the polymorphism of the peptide repeat motifs (PRMs), the genetic diversity indices and phylogenetic relationships. PCR amplicons determined size polymorphism of 610, 700 and 710 bp in Pvcsp of Sri Lanka where all amino acid sequences obtained were of the VK210 variant, consisting variable repeats of 4 different PRMs. The two most abundant PRMs of the CR domain, GDRADGQPA and GDRAAGQPA consisted ~ 2-4 repeats, while GNRAAGQPA was unique to the island. Though, different nucleotide sequences termed repeat allotypes (RATs) were observed for each PRM, these were synonymous contributing to a less polymorphic CR domain. The genetic diversity of Pvcsp in Sri Lanka was due to the number of repetitive peptide repeat motifs, point mutations, and intragenic recombination. The 19 amino acid haplotypes defined were exclusive to Sri Lanka, whereas the 194 Pvcsp sequences of global isolates generated 57 more distinct a.a. haplotypes of the VK210 variant. Strikingly, the CR domain of both VK210 and VK247 variants was under purifying selection interpreting the scarcity of CSP non-synonymous polymorphisms. Insights to the distribution of RATs in the CR region with geographic clustering of the P. vivax VK210 variant were revealed. The cladogram reiterated this unique geographic clustering of local (VK210) and global isolates (VK210 and VK247), which was further validated by the elevated fixation index values of the VK210 variant.     

Efficacy of rupatadine in reducing the incidence of dengue haemorrhagic fever in patients with acute dengue: A randomised,double blind,placebo-controlled trial

BackgroundRupatadine was previously shown to reduce endothelial dysfunction in vitro, reduced vascular leak in dengue mouse models and to reduce the extent of pleural effusions and thrombocytopenia in patients with acute dengue. Therefore, we sought to determine the efficacy of rupatadine in reducing the incidence of dengue haemorrhagic fever (DHF) in patients with acute dengue.Methods and findingsA phase 2, randomised, double blind, placebo controlled clinical trial was carried out in patients with acute dengue in Sri Lanka in an outpatient setting. Patients with ≤3 days since the onset of illness were either recruited to the treatment arm of oral rupatadine 40mg for 5 days (n = 123) or the placebo arm (n = 126). Clinical and laboratory features were measured daily to assess development of DHF and other complications. 12 (9.7%) patients developed DHF in the treatment arm compared to 22 (17.5%) who were on the placebo although this was not significant (p = 0.09, relative risk 0.68, 95% CI 0.41 to 1.08). Rupatadine also significantly reduced (p = 0.01) the proportion of patients with platelet counts <50,000 cells/mm³ and significantly reduced (p = 0.04) persisting vomiting, headache and hepatic tenderness (p<0.0001) in patients. There was a significant difference in the duration of illness (p = 0.0002) although the proportion of individuals who required hospital admission in both treatment arms. Only 2 patients on rupatadine and 3 patients on the placebo developed shock, while bleeding manifestations were seen in 6 patients on rupatadine and 7 patients on the placebo.ConclusionsRupatadine appeared to be safe and well tolerated and showed a trend towards a reducing proportion of patients with acute dengue who developed DHF. Its usefulness when used in combination with other treatment modalities should be explored.Trial registrationInternational Clinical Trials Registration Platform: SLCTR/2017/024.