G-Quadruplex ligands: Potent inhibitors of telomerase activity and cell proliferation in Plasmodium falciparum.

Telomeres are DNA and protein structures located at the ends of eukaryotic chromosomes. These structures maintain chromosomal stability by impeding chromosomal ends from being recognized and processed as fragmented DNA. They also support the complete replication of the genome by providing mechanisms that solve the end-replication problem. Telomeric DNA is formed of short, repeating, guanine-rich sequences. The G-rich sequence extends towards the 3' end, forming a protruding single-stranded end that can acquire a conformation known as G-quadruplex. The ligands stabilizing this structure are potent inhibitors of telomerase activity, a catalytic activity necessary to compensate for the loss of telomeric DNA that occurs in each round of replication. In the absence of telomerase, telomeres shorten after a given number of cell divisions, after which the cell enters a senescence state and finally dies. In the presence of telomerase activity, telomeres are preserved, and cells reach a state of indefinite replication or immortalization. This study analyzed the effect of two ligands of the G-quadruplex (TMPyP4 and Telomestatin) on the telomerase activity and cell proliferation of Plasmodium falciparum, given that this parasite has a high proliferation rate and an almost indefinite replication capacity. The effect of the ligands on telomerase activity was evaluated using the TRAP (Telomere Repeat Amplification Protocol) activity assay, which was performed in the presence of increasing concentrations of each ligand. In this study, TMPyP4 showed the highest inhibitory effect, reaching 50% inhibition at a 5µM concentration. Regarding proliferation, both ligands drastically affected parasite growth, but Telomestatin had a stronger effect. After three days of treatment, parasite growth decreased by 90%. Thus, it is possible that this compound interferes with other vital pathways for the parasite beyond the elongation of telomeric DNA by telomerase.

Description of high rates of unapparent and simultaneous multiple dengue virus infection in a Colombian jungle settlement.

Dengue disease statistics is mainly based on consulting patients with febrile illness, but misdiagnosed and asymptomatic cases are important to measure dengue epidemiology in endemic areas. The main objective of this work was to determine the prevalence of IgM and IgG antibodies or NS1 antigen and viral RNA in a group of healthy volunteers from an isolated village in Colombian Chocó rain forest. It found 51.7% of virologically PCR confirmed asymptomatic cases, despite low IgM seroprevalence. It was confirmed that all four serotypes are in the circulation and in 17.2% of individuals it detected natural coinfections of two or three different serotypes simultaneously. This is the first report in Colombia evaluating viremia in asymptomatic volunteers. These findings pose a big concern about the transmission of dengue virus by asymptomatic individuals because they can spread the virus without take appropriate control measures.