Fig. 6: Histopathologic features of injection site, lymph node, and liver in rats following vaccination with monovalent influenza modRNA-HA.
From: Preclinical immunogenicity and safety of hemagglutinin-encoding modRNA influenza vaccines
a Injection site section of mIRV (H1) immunized animals euthanized 2 days after the third dose (Day 17) showing inflammatory cells (arrows) admixed with pale eosinophilic fluid (edema) (black asterisk) infiltrating and expanding subcutaneous tissue and connective tissue of skeletal muscle. b 20x magnification of (a) showing inflammatory cells (mainly neutrophils with fewer plasma cells, macrophages, and lymphocytes) (arrows) and edema fluid (asterisk) surrounding myofibers. c Injection site section of mIRV immunized animals euthanized after a 3-week recovery showing fewer inflammatory cells infiltrating and expanding subcutaneous tissue and spaces around skeletal myofibers (arrows). d 20x magnification of (c) showing inflammatory cells (fewer plasma cells and lymphocytes) surrounding myofibers (arrows). e Lymph node sections of mIRV immunized animals showing prominent germinal centers (GC) and inflammatory cells (predominantly plasma cells) expanding sinuses (inset). f Liver sections of mIRV immunized animals euthanized 2 days after the third dose (Day 17) showing hepatocytes containing small clear round membrane bound structures within cytoplasm (black arrowheads).
