Sensitive immunoassay of Legionella using multivalent conjugates of engineered VHHs.

This article focuses on the development of a sensitive immunoassay system for detecting Legionella pneumophila serogroup 1 (LpSG1), the primary pathogen causing Legionnaires' disease, using VHH antibodies (nanobodies) derived from alpaca heavy-chain antibodies. A VHH phage display library was constructed from immunized alpacas, leading to the isolation of two LpSG1-specific VHH clones, Env9 and Env21, which were engineered and conjugated to carrier proteins such as bovine serum albumin (BSA) and keyhole limpet hemocyanin (KLH). These multivalent VHH conjugates demonstrated significantly enhanced sensitivity in a latex agglutination assay compared to monomeric or dimeric VHHs and outperformed a commercial Legionella detection kit. The study highlights the potential of engineered VHH conjugates for rapid, specific, and sensitive detection of Legionella in clinical and environmental settings.