Earlier this month, I had the good fortune to attend the “Keystone Joint Symposia” event in Keystone, Colo. (and yes, it was much colder than at Antibody Solutions’ headquarters in Sunnyvale, Calif.!).The speakers during the sessions had two primary goals: (1) to present the most recent advances in the biology of T cell-dependent B cell responses; and (2) to explore how our understanding of B-T cell interactions influence antibody generation and inform vaccine development.
The B and T cell symposium focused on the biology of Germinal Centers, the roles of T follicular helper (Tfh) cells and Memory B Cells (MBC’s), and the clonal dynamics of the antibody response. And later in the day, the Vaccines and Immune Monitoring symposium centered around structure-based vaccine design, antibody-based immune monitoring, and manipulation of humoral immunity to obtain B cells that make the right antibodies for neutralization and protection.
I found both symposia useful in providing: (a) an up-to-date understanding of the biology guiding B cell responses to an antigen, and (b) methods to drive the B cell response to generate desired antibodies.These are both helpful in our quest to discover therapeutic antibodies.
Of particular interest to me was Gabriel Victora’s presentation on the Clonal Dynamics of the Antibody Response. At Antibody Solutions, we occasionally observe a limited repertoire of antibodies (or multiple copies of the same antibody) obtained from an immunization program. As Gabriel explained, in the germinal centers (GCs), while you start with a mixed population, after repeated immunization each GC becomes more or less clonal with hundreds of the same B cell clone. There are many GCs so you can get diversity that way depending upon what became the dominant clonal population in each GC.
The practical outcome of this is a population B cells or hybridomas with many copies of the same clone. One group we work with that does primary B-cell isolation of plasma cells finds that about 30 percent of the Ag-positive clones in the total population are unique by sequencing. When we’ve sequenced hybridoma clones picked from a primary screen with a protein Ag, there are anywhere from 30-70 percent unique clones.
In either case, you might find that one clone is highly represented (e.g., 20 percent) and one is rare (e.g., one percent or less). Picking the top 20 percent from a screen might obtain clones with the same or similar sequence. If the immunogen is small or a unique epitope (e.g., peptide), or you apply a stringent screening criteria, then you will increase the likelihood of getting clones with the same sequence out of the population, since there is limited potential diversity.
There are many approaches that can increase diversity, including using different forms of the antigen, different strains and species of host animals, and different adjuvants. The “best” strategy for each target antigen will vary depending upon the nature of the target, how potential antibodies will be used, and overall goals of the antibody discovery program.
We look forward to our next conference coming up in April, PEGS Boston 2019, where we will be sharing some of our latest findings working with transgenic animal platforms. Hope to see you there.
An observation from Keystone Joint Symposia on: B Cell and T Cell Interactions, and, Molecular Approaches to Vaccines and Immune Monitoring
February 10–14, 2019 Keystone Conference Center Keystone, Colorado, USA
