Figure 2. Different antibody formats that have been investigated for their utility in neutralizing snake toxins. (A) Schematic representations of an immunoglobulin G (IgG) antibody, a heavy-chain-only antibody (HCAb), and a variable heavy-chain domain (V_HH). IgG antibodies are composed of four polypeptide chains: two identical heavy chains (H) and two identical light chains (L), forming a flexible Y-shaped structure. Each chain contains a variable (V) region and one or more constant (C) region(s). In contrast, camelids produce a unique type of antibodies, consisting of only heavy chains known as HCAbs. When expressed alone, the variable domains of HCAbs are referred to as V_HHs and are notably smaller in size compared to the IgG. (B) The crystal structure of a representative V_HH (PDB ID 4PPT). The complementarity-determining regions (CDRs), particularly the long flexible loop of CDR3, are highly variable and crucial for antigen binding. CDRs 1, 2, and 3 are indicated in red, yellow, and blue, respectively. The figure was created with BioRender.com.