FIG 6.

RSV VLP vaccines do not induce “vaccine-enhanced disease” in murine lung. (A) Hematoxylin and eosin staining of mouse lung 4 days after viral challenge. Microscopic examination of the lungs after the combo VLP vaccination shows the absence of or minor pulmonary pathology. On the other hand, the FI-RSV vaccination induces a very high perivascular immune infiltration. A placebo control is included as a reference. (B) Perivascular infiltration was scored by blind evaluation of sections of mouse lung stained with hematoxylin and eosin 4 days after the viral challenge. The scores range from 0 for normal to a maximum of 3 for massive infiltration. An asterisk indicates a statistically significant difference between VLP vaccination and FI-RSV (P < 0.05). (C) Mouse lungs were harvested 4 and 7 days after RSV challenge and weighed. An asterisk indicates a statistically significant difference with respect to the VLP vaccines and placebo control (P < 0.05).