The time course analysis of morphological changes induced by Chikungunya virus replication in mammalian and mosquito cells.

Chikungunya virus (CHIKV), a re-emerging Alphavirus, causes chronic myalgia and arthralgia in infected individuals. However, the exact pathophysiology remains undefined till date. Virus induced time course changes in host cells at the ultrastructural level and host cytoskeleton have been reported for other alphaviruses such as Sindbis and Semliki Forest virus. Few studies have tried to delineate the same for CHIKV leading to some understanding of the replication process. Selective CHIKV infection of progenitor cells involved in muscle repair has been proposed as a cause of myalgia; albeit the outcome of infection on these cells has not been reported. With this background, we investigated CHIKV-induced time course changes in two cell lines - Aedes albopictus (C6/36) and murine myoblasts (C2C12) by transmission electron microscopy (TEM). CHIKV infection of C2C12 cells resulted in cell death, with cells exhibiting well defined apoptotic features. In contrast, mature virions were released from infected C6/36 cells without cytolysis. Double labelling of C2C12 cytoskeletal proteins - such as actin, tubulin and CHIKV revealed that viral nucleocapsids co-localized with these proteins during replication. As the infection progressed, CHIKV disrupted the normal organisation of these cell proteins. CHIKV-induced plasma membrane extensions were observed in infected cells, which so far have been reported only for Sindbis virus. This is a first report describing the time course of morphological changes occurring in host cells as a result of infection with CHIKV at the ultrastructural level. Apoptosis of myoblasts due to CHIKV infection could also be an important factor contributing to the recurrence of myalgia in CHIKV patients. Keywords: Chikungunya; electron microscopy; confocal microscopy; C6/36; C2C12; actin; α-tubulin.