The structure of Sindbis virus produced from vertebrate and invertebrate hosts as determined by small-angle neutron scattering

Abstract

The complex natural cycle of vectored viruses that transition between host species, such as between insects and mammals, makes understanding the full life cycle of the virus an incredibly complex problem. Sindbis virus, an arbovirus and prototypic alphavirus having an inner protein shell and an outer glycoprotein coat separated by a lipid membrane, is one example of a vectored virus that transitions between vertebrate and insect hosts. While evidence of host-specific differences in Sindbis virus has been observed, no work has been performed to characterize the impact of the host species on the structure of the virus. Here, we report the first study of the structural differences between Sindbis viruses grown in mammalian and insect cells, which were determined by small-angle neutron scattering (SANS), a nondestructive technique that did not decrease the infectivity of the Sindbis virus particles studied. The scattering data and modeling showed that, while the radial position of the lipid bilayer did not change significantly, it was possible to conclude that it did have significantly more cholesterol when the virus was grown in mammalian cells. Additionally, the outer protein coat was found to be more extended in the mammalian Sindbis virus. The SANS data also demonstrated that the RNA and nucleocapsid protein share a closer interaction in the mammalian-cell-grown virus than in the virus from insect cells.

FIG. 1.

SANS patterns of BHK (□)- and C7-10 (▿)-grown Sindbis particles in potassium tartrate buffer at pD 7.2. The Guinier plots for BHK (□) and C7-10 (▿) are shown in the inset. Superimposed are best-fit straight lines, determined by the least-squares procedure, which were used to estimate the radius of gyration, R_g, and zero-angle scattering intensity I(0). The data have been offset for clarity.

FIG. 2.

Distance distribution functions, P(r), of BHK (solid line)- and C7-10 (dotted line)-grown Sindbis particles. The inset plot shows the difference in P(r) values of two particles.

FIG. 3.

Radial-scattering-length-density distribution function of BHK (•)- and C7-10 (○)-grown Sindbis particles.

FIG. 4.

Four-shell model for BHK (□, low-q data; ○, high-q data)- and C7-10 (▵, low-q data; ▿, high-q data)-grown Sindbis particles in potassium tartrate at pD 7.2. The solid line in each curve corresponds to the best fit using the multishell model. The curves have been offset for clarity, further than in Fig. 1.