Figure 4

Vaccination with gp150-containing exosomes does not affect a subsequent MHV-68 challenge infection. A) Virus titers in the lung, B) Spleen weights, C) Ex vivo reactivation of splenocytes and D) Viral genomic load in the spleen. Mice were vaccinated twice (day 0 and 14) with gp150-containing exosomes (293/gp150) or as a control, with exosomes prepared from untransfected 293 cells (293). On day 28, mice were challenged by i.n. infection with 5 × 10⁴ PFU. A) Lytic replication was analyzed five days after infection (day 33) by determining virus titers in lung homogenates by standard plaque assay. Each symbol represents an individual mouse and the bars represent the mean. The data are compiled from 2 independent experiments. B) to D) Seventeen days after infection (day 45), spleens were harvested and the spleen weights were taken (panel B). Single splenocyte suspensions were prepared and analyzed in the ex vivo reactivation assay (panel C) or used for DNA isolation for real time PCR analysis (panel D). Data shown in panel B) are means + SD from 8 mice compiled from two independent experiments. Data shown in panel C are means + SEM compiled from two independent experiments. In each experiment, splenocytes from 5 and 3 mice per group, respectively, were pooled. The dashed line in panel C) indicates the point of 63.2% Poisson distribution, determined by nonlinear regression, which is used to calculate the frequency of cells reactivating lytic replication. In panel D), each symbol represents an individual mouse and the bars represent the mean. The data are compiled from 2 independent experiments. There were no significant differences in virus titers in the lung (panel A), spleen weights (panel B), ex vivo reactivation of splenocytes (panel C) and viral genomic load in the spleen (panel D). The two-tailed Student’s t-test was used for statistical analysis.