Fig. 2. Anti-CotH3 polyclonal antibodies protect mice from R. delemar intratracheal infection.

Intraperitoneal treatment with a single dose of the polyclonal antibody (Ab), 24 hours after intratracheal infection of neutropenic mice (A to C) or DKA mice (D and E), protected them from R. delemar infection. Survival of neutropenic (A) or DKA mice (D) was conducted using 10 mice per group with confirmed inhaled inoculum of 1.2 × 10⁴ for (A) and 6.3 × 10³ for (D). *P < 0.05 versus mice treated with preimmune IgG. A single dose of 30 μg of anti-CotH3 IgG resulted in a significant reduction of lung and brain fungal burden in neutropenic (B) (inhaled inoculum of 3.2 × 10³) and DKA mice (E) (inhaled inoculum of 3.6 × 10³) when compared to isotype-matched control IgG at the same dose. Mice were euthanized 72 hours after infection. Hematoxylin and eosin staining of lung and brain sections harvested from neutropenic mice (C) revealed extensive tissue edema and hemorrhage in the lungs of mice treated with isotype-matched IgG, whereas mice treated with anti-CotH3 IgG had normal architecture (lower magnification). Abundant fungal hyphae invading lungs of mice treated with isotype-matched IgG, but not anti-CotH3 IgG, could be detected (higher magnification). Brains from isotype-matched IgG-treated, but not anti-CotH3 IgG-treated, mice showed mucormycosis angioinvasion. Scale bars, 300 μm (C).