Technetium-99m-human polyclonal IgG radiolabeled via the hydrazino nicotinamide derivative for imaging focal sites of infection in rats.

TLDR

The study evaluated the biological behavior of human polyclonal IgG radiolabeled with technetium‑99m via a novel nicotinyl hydrazine derivative in rats. The authors compared 99mTc‑IgG and 111In‑IgG by co‑injecting them into rats, measuring biodistribution at 2, 6, and 16 h, and assessing imaging of deep‑thigh E. coli infection.

Abstract

The biologic behavior of human polyclonal immunoglobulin (IgG) radiolabeled with technetium-99m (99mTc) by a novel method, via a nicotinyl hydrazine derivative, was evaluated in rats. Technetium-99m- and indium-111-IgG were co-administered to normal rats and biodistribution was determined at 2, 6, and 16 hr. The inflammation imaging properties of the two reagents were compared in rats with deep-thigh infection due to Escherichia coli. Blood clearance of both antibody preparations was well described by a bi-exponential function: (99mTc-IgG: t1/2 = 3.82 +/- 0.89 and 57.52 +/- 1.70 hr. 111In-IgG: 3.93 +/- 0.117 and 40.71 +/- 1.26 hr). Biodistributions in the solid organs were similar, however, small but statistically significant differences were detected: 99mTc-IgG greater than 111In-IgG in lung, liver, and spleen; 99mTc-IgG less than 111In-IgG in kidney and skeletal muscle (p less than 0.01). At all three imaging times, target-to-background ratio and percent residual activity for the two compounds were remarkably similar. These studies establish that human polyclonal IgG labeled with 99mTc via a nicotinyl hydrazine modified intermediate is equivalent to 111In-IgG for imaging focal sites of infection in experimental animals.