An Ironic Story
Neutrophils are one type of ‘first responder’ innate immune cell that secrete antimicrobial proteins in response to infection. Strong’s lab studies one such protein, NGAL, that is a member of a large family of proteins called lipocalins, which have a very telling “cup” structure for binding ligands. Despite detailed structural and biochemical analyses of NGAL, which has a comparatively large and obvious binding pocket, the Strong lab was unable to identify a ligand.
“It (NGAL) looked like a coffee mug,” Strong said. “A deep cavity containing positively charged amino acids almost undoubtedly suggests a binding pocket for a negatively charged molecule.”
Continuing their pursuit to identify and characterize NGAL molecular interactions, Strong’s lab decided to switch from a viral expression system to a more efficient E. coli system for generating the large amount of protein needed for x-ray crystallography.
Moving Toward a Vaccine By Going in Reverse
Most successful vaccines have been made by following a relatively standard formula. Briefly, the disease-causing agent, such as a virus, is 1) isolated; 2) killed or attenuated (becoming an immunogen); and 3) administered to healthy individuals, who then make a strong adaptive immune response that is protective against infection. Unfortunately, despite 30 years of research, this method has heretofore been unsuccessful for HIV.
“Our goal is to develop a prophylactic humoral HIV vaccine so that when you vaccinate a healthy person, the antibody response is sufficient to prevent infection later on,” said Strong.
As opposed to the standard vaccine formula, Strong’s lab uses a novel ‘backward’ approach for HIV vaccine development called reverse vaccinology. There are a minute number of HIV-infected people who have lucked out because their bodies make anti-HIV antibodies that can control infection. His team analyzes these antibodies to determine why they work and what viral immunogens they recognize, and then designs recombinant immunogens that specifically re-elicit that antibody response.
“We don’t truly understand exactly how these antibodies really work: the specific mechanism by which they stop the virus. We have pieces of it, but we don’t have the whole story,” Strong said.
In collaboration with Seattle BioMed’s Dr. Leo Stamatatos, Strong is analyzing two antibodies, called b12 and 4E10, that are directed against certain regions of the HIV protein Env. They use detailed molecular and biophysics techniques to determine the binding kinetics and affinity, thermodynamic properties and conformational changes relating to the interactions between 4E10 and b12 with different Env immunogens. They are also studying how the parental forms of these antibodies interact with immunogens at the start of the immunization process.
In a related study, Strong and Stamatatos recently uncovered a potential reason why the recombinant form of a different Env immunogen fails to induce the broadly neutralizing capability of antibody b12. It turns out that during natural infection, Env actually affects b12 B-cell maturation, a multi-step process that ultimately leads to a person’s highly diverse antibody pool. Without this engagement, Env cannot elicit a productive b12 antibody response.
The capability to define the action/reaction dynamics of molecular interactions allows scientists to explain the big picture by understanding the small picture. Some of Strong’s contributions include illuminating how in-depth antibody-immunogen interaction studies are crucial to the design of future HIV vaccines, discovering and characterizing novel innate immune strategies that regulate microbial infections via iron sequestration, and parsing out various NK- and T-cell receptor interactions with cognate ligands and target cells. Strong has developed a unique niche in VIDD where he uses structural biology and biophysics to address human health issues such as infectious disease and basic immune system function.
»Roland Strong faculty page
»Strong Lab website