Identification of a nanobody specific to human pulmonary surfactant protein A.

ABSTRACT: Nanobody (Nb) is a promising vector for targeted drug delivery. This study aims to identify an Nb that can specifically target the lung by binding human pulmonary surfactant protein A (SP-A). Human lung frozen tissue sections were used for 3 rounds of biospanning of our previously constructed Nb library for rat SP-A to establish a sub-library of Nb, which specifically bound human lung tissues. Phage-ELISA was performed to screen the sub-library to identify Nb4, which specifically bound human SP-A. The binding affinity Kd of Nb4 to recombinant human SP-A was 7.48?×?10-7 M. Nb4 (19?kDa) was stable at 30?°C-37?°C and pH 7.0-7.6 and specifically bound the SP-A in human lung tissue homogenates, human lung A549 cells, and human lung tissues, whereas didn't react with human liver L-02 cells, kidney 293T cells, and human tissues from organs other than the lung. Nb4 accumulated in the lung of nude mice 5?minutes after a tail vein injection of Nb4 and was excreted 3?hours. Short-term exposure (one month) to Nb4 didn't cause apparent liver and kidney toxicity in rats, whereas 3-month exposure resulted in mild liver and kidney injuries. Nb4 may be a promising vector to specifically deliver drugs to the lung.

SUBMITTER: He X 

PROVIDER: S-EPMC5431231 | biostudies-literature | 2017 May

REPOSITORIES: biostudies-literature