Abstract
The cellular cytoskeleton is central for key cellular functions, and as such is a marker for diseased and infected cell states. Here we analyzed infection with rubella virus (RV) strains with respect to phenotypes in cellular mechanical properties, cell movement, and viral cytopathogenicity. Real-time deformability cytometry (RT-DC), as a high-throughput platform for the assessment of cell mechanics, revealed a correlation of an increase in cortical filamentous-actin (F-actin) with a higher cellular stiffness. The additional reduction of stress fibers noted for only some RV strains as the most severe actin rearrangement lowered cell stiffness. Furthermore, a reduced collective and single cell migration speed in a wound healing assay was detected in addition to severe changes in cell morphology. The latter was followed by activation of caspase 3/7 as a sign for induction of apoptosis. Our study emphasizes RT-DC technology as a sensitive means to characterize viral cell populations and to implicate alterations of cell mechanical properties with cell functions. These interdependent events are not only promising options to elucidate viral spread and to understand viral pathologies within the infected host. They also contribute to any diseased cell state, as exemplified by RV as a representative agent for cytoskeletal alterations involved in a cytopathological outcome.
Highlights
Rubella virus (RV) is the only member of the genus Rubivirus of the Togavirus family.The single-stranded RNA genome in plus-strand orientation encodes two non-structural (P150 andP90) and three structural proteins.While postnatal infections are generally mild or asymptomatic, perinatal infections of susceptible women during the first trimester of pregnancy can result in severe malformations of the unborn child known as congenital rubella syndrome (CRS)
cytopathogenic effect (CPE) during rubella virus (RV) infection is visible through cell rounding with subsequent detachment from the monolayer, which generates a population of cells floating in the supernatant (Figure 1A(i))
CPE development could contribute to an increase in the ratio of total number of particles to infectious particles, which was noted for the high-cytopathogenic strains
Summary
Rubella virus (RV) is the only member of the genus Rubivirus of the Togavirus family.The single-stranded RNA genome in plus-strand orientation encodes two non-structural (P150 andP90) and three structural (the envelope glycoproteins E1 and E2 and the capsid protein) proteins.While postnatal infections are generally mild or asymptomatic, perinatal infections of susceptible women during the first trimester of pregnancy can result in severe malformations of the unborn child known as congenital rubella syndrome (CRS). Despite the availability of an effective vaccine, RV is still a cause of outbreaks [5,6] and CRS cases occur even in countries of the Western world [7]. The mechanisms and signaling pathways that lead to the strictly human-specific pathophysiological mechanisms behind CRS are still unknown, but contributing factors were discussed [4,8]. Among those factors was the reduction and rearrangement of actin filaments in discrete clumps in viral protein-enriched areas [9]. All viral proteins involved in RV replication, namely the replicase proteins P90 and P150, and the capsid protein [11], were found to co-localize with the actin cytoskeleton [10,12]
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