Effects of collagen matrix on Sindbis virus infection of BHK cells

The effects of extracellular matrix (ECM) components on the outcomes of alphavirus interaction with cells are not known. Studies that address such interactions have to address several methodological difficulties, including: the survival of the cells within the matrix; the passage of the virus through the matrix to infect embedded cells; and the dissociation of cells and matrix into single-cell suspension, before and after virus infection, for quantitative analysis. Herein, these issues were addressed in the context of a model system of collagen as the ECM component, baby hamster kidney (BHK) cells, and Sindbis virus. The outcomes of Sindbis virus infection of BHK cells, grown in three-dimensional (3D) collagen gel versus on plastic, and on two-dimensional (2D) collagen versus bovine serum albumin (BSA)-coated surfaces were compared. Cell morphology was more slender in 3D and on 2D collagen than on plastic or BSA-coated surfaces. The cells were able to survive in the 3D environment. Using Sindbis virus carrying the green fluorescent protein gene, the virions were found to be capable of penetrating the 3D collagen matrix and infecting the cells. There was more infectious virus in cultures of cells in 3D and on 2D collagen than on plastic or BSA-coated surfaces, respectively. Higher virus titers from cells on 2D collagen compared to BSA-coated surfaces was not associated with uninfected cell number or viability but with increased cell survival after infection. Infected cells on BSA surfaces became detached, while those on 2D collagen remained attached. These experiments establish procedures for analysis of interaction of collagen, BHK cells, and Sindbis virus and suggest that collagen increases infectious Sindbis virus titers from BHK cells by enhancing post-infection cell survival.