Antibodies are extremely important as the primary mediators of the immune response to infectious agents and vaccines, but also as recombinant molecules used as therapeutics, diagnostics, and research reagents. Thus, understanding the mechanisms by which antibodies form, bind, and neutralize their targets is very important in multiple biomedical areas. Most vertebrate antibody repertoires form their diversity through V(D)J recombination, where combinatorial rearrangement of V, D, and J genes form a vast repertoire where the complementarity determining regions (CDRs) form a relatively flat binding surface for interaction with antigen. Remarkably, cows appear to have a different mechanism for generating diversity and binding antigen; cow antibodies have particularly long CDR H3 regions, a subset of which can be over 70 amino acids long, which form ?-ribbon ?stalk? and disulfide-bonded ?knob? minidomains that protrude far from the typical antibody surface. Remarkably, antibodies from this repertoire can potently and broadly neutralize HIV, whereas normal human or mouse antibody repertoires cannot. Therefore, they have unique abilities to bind and neutralize particularly challenging antigens. Here we propose studies to understand in molecular detail the genetic mechanisms underlying formation of these antibodies, the binding properties of the stalk and knob minidomains, and the unique potential of these antibodes to bind bivalently and bispecifically. These studies will provide insight into mechanisms of viral neutralization generally, and particularly HIV neutralization. Additionally, given the potential of these antibodies to bind recessed epitopes, we will generate additional antibodies against particularly challenging antigens like enzymatic active sites and ion channels. We will employ mutagenesis, binding, and structural methods, as well as cellular assays to evaluate the unique properties of these antibodies. Understanding this novel class of antibodies in detail could provide fundamental insights needed for effective vaccine design as well as discovery and engineering of antibodies against some of the most challenging targets in biomedicine. Similarly, our unique antibodies discovered and characterized in this proposal could eventually become therapeutic candidates themselves.
Antibodies are important in medicine through binding their target antigens with a relatively flat binding surface, however some recessed or concave epitopes are very challenging for traditional antibodies. We have discovered a class of cow antibodies with utralong CDR H3 regions with protruding ?stalk? and ?knob? minidomains that are able to bind challenging epitopes and, in this regard, can broadly neutralize the HIV-1 virus. We aim to understand the molecular mechanisms for how this unusual type of antibody forms, and how they interact with antigen.
| Haakenson, Jeremy K; Huang, Ruiqi; Smider, Vaughn V (2018) Diversity in the Cow Ultralong CDR H3 Antibody Repertoire. Front Immunol 9:1262 |
| Stanfield, Robyn L; Haakenson, Jeremy; Deiss, Thaddeus C et al. (2018) The Unusual Genetics and Biochemistry of Bovine Immunoglobulins. Adv Immunol 137:135-164 |
| Sok, Devin; Le, Khoa M; Vadnais, Melissa et al. (2017) Rapid elicitation of broadly neutralizing antibodies to HIV by immunization in cows. Nature 548:108-111 |
| Vadnais, Melissa L; Smider, Vaughn V (2016) Bos taurus ultralong CDR H3 antibodies. Curr Opin Struct Biol 38:62-7 |
| Stanfield, Robyn L; Wilson, Ian A; Smider, Vaughn V (2016) Conservation and diversity in the ultralong third heavy-chain complementarity-determining region of bovine antibodies. Sci Immunol 1: |
| Muyldermans, Serge; Smider, Vaughn V (2016) Distinct antibody species: structural differences creating therapeutic opportunities. Curr Opin Immunol 40:7-13 |
| de los Rios, Miguel; Criscitiello, Michael F; Smider, Vaughn V (2015) Structural and genetic diversity in antibody repertoires from diverse species. Curr Opin Struct Biol 33:27-41 |
