Serum-mediated, FcR-dependent MHV-68 infection depends on gp150.

<p>A. Wild-type or gp150-deficient virions were incubated with sera from BALB/c mice, taken 2 months after infection with wild-type (WT), gp150-deficient (M7^-FRT, M7^-STOP) or revertant (REV) viruses as indicated. The virus/serum mixtures were then added to RAW264.7 cells (3 PFU/cell). The proportion of infected cells in each culture was determined 18h later by flow cytometric assay of viral eGFP expression. nil = uninfected, vir = virus only. Each serum sample was pooled from 5 mice. The data are from 1 of 2 equivalent experiments. B. Sera were taken from C57BL/6 mice 6 months after infection with either wild-type (WT) or M7^-STOP (gp150⁻) viruses. EGFP-expressing WT or gp150⁻ viruses were then incubated with sera from individual mice and used to infect RAW264.7 cells. The level of infection was assayed 18h later by flow cytometry of viral eGFP expression. C. Sera were pooled from 5 mice at 6 months after infection with wild-type (WT) or gp150-deficient (M7^-) MHV-68. Gp150-specific antibodies were removed from wild-type-immune sera by 3 rounds of incubation on 2% paraformaldehyde-fixed CHO-gp150 cells (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0000705#pone-0000705-g002" target="_blank">Figure 2D</a>) (WT abs-150). Controls were incubated on paraformaldehyde-fixed CHO cells (WT abs-C). Wild-type or gp150-deficient viruses were incubated with each serum sample and then used to infected RAW264.7 cells (3 PFU/cell, 18 h). The data are representative of 2 experiments.