INSTITUTO DE INVESTIGACIONES BIOTECNOLOGICAS
Unidad Ejecutora - UE
congresos y reuniones científicas
Function of repetitive elements at the 3'UTR of chikungunya virus
FILOMATORI, CLAUDIA V.; BARDOSSY EUGENIA SOLEDAD; ALVAREZ DIEGO EZEQUIEL
Encuentro; II Argentine Meeting on Biology of Non-coding RNAs; 2018
Universidad Nacional de Quilmes
Chikungunya virus (CHIKV) is an alphavirus transmitted by mosquitoes that infects humans and causes febrile syndrome with rash and articular pain. As other alphaviruses, it has a positive single stranded RNA genome of 11-12kb, with a type 0 cap at the 5? end and a poly (A) tail at the 3?end. The 3?untranslated region (3?UTR) of the viral genome contains short sequence repetitions named direct repeats (DRs). Notably, copy number of DRs varies among viral lineages, indicating that the 3?UTR diverged from a common ancestor that suffered historical events of duplication. Sequences of CHIKV DRs are relatively conserved in closely related lineages, suggesting that they have functional significance. Particularly, CHIKV isolates circulating in America have a 3?UTR with a greater number of repetitions than ancestral viruses. So far, the role of DRs on viral replication and their specific requirement in human and mosquito cell lines remains poorly understood. To perform our studies, we have in the laboratory a CHIKV infectious clone obtained from an isolate of the Caribbean Islands (Cbn-CHIKV), which has the longest 3?UTR described in nature to date, with three copies of repetition (1+2), and two copies of repetition 3. Using a reverse genetic system, we obtained viral mutants with different number of DRs at their 3?UTRs, and then we evaluated their infectivity in mammalian and mosquito cell lines by indirect immunofluorescence and one-step growth curves.We observed that there are differential requirements of the DRs in mammalian and mosquito cell lines. For instance, in mosquito cells, the (1+2) triple deletion drastically decreased viral replication, while in mammalian cells it showed no significant effect. Intermediate deletions did not significantly affect viral replication in mosquito nor in mammalian cells, demonstrating that these elements have a redundant function. his study shows for the first time the effects of systematic deletions of the repetitive elements at the 3?UTR of Cbn- CHIKV on viral replication and their differential role in mosquito and mammal cell lines. We also examined the dynamics of viral populations adapted to mammalian or mosquito cells. We found that sequence repetitions are highly variable in cell culture, recapitulating the 3?heterogeneity of natural isolates. After host switching, the relative abundance of viral variants changes drastically, indicating that viral populations are dynamic when the virus shuttles from mammalian to mosquito cells, with different variants being negatively or positively selected in each cell line.Altogether, our findings provide important insights into the function of CHIKV-3?UTR plasticity for host cell adaptation, pointing out a central role of host-specific requirements on the definition of CHIKVl on-going evolution.