The Effect of N-Terminal Cyclization on the Function of the HIV Entry Inhibitor 5P12-RANTES

Efficient production of fluorophore-labeled CC chemokines for biophysical studies using recombinant enterokinase and recombinant sortase

Chemokines are important immune system proteins, many of which mediate inflammation due to their function to activate and cause chemotaxis of leukocytes. An important anti-inflammatory strategy is therefore to bind and inhibit chemokines, which leads to the need for biophysical studies of chemokines as they bind various possible partners. Because a successful anti-chemokine drug should bind at low concentrations, techniques such as fluorescence anisotropy that can provide nanomolar signal detection are required. To allow fluorescence experiments to be carried out on chemokines, a method is described for the production of fluorescently labeled chemokines. First, a fusion-tagged chemokine is produced in Escherichia coli, then efficient cleavage of the N-terminal fusion partner is carried out with lab-produced enterokinase, followed by covalent modification with a fluorophore, mediated by the lab-produced sortase enzyme. This overall process reduces the need for expensive commercial enzymatic reagents. Finally, we utilize the product, vMIP-fluor, in binding studies with the chemokine binding protein vCCI, which has great potential as an anti-inflammatory therapeutic, showing a binding constant for vCCI:vMIP-fluor of 0.37 ± 0.006 nM. We also show how a single modified chemokine homolog (vMIP-fluor) can be used in competition assays with other chemokines and we report a Kd for vCCI:CCL17 of 14 μM. This work demonstrates an efficient method of production and fluorescent labeling of chemokines for study across a broad range of concentrations.

Sustained release silk fibroin discs: Antibody and protein delivery for HIV prevention

With almost 2 million new HIV infections worldwide each year, the prevention of HIV infection is critical for stopping the pandemic. The only approved form of pre-exposure prophylaxis is a costly daily pill, and it is recognized that several options will be needed to provide protection to the various affected communities around the world. In particular, many at-risk people would benefit from a prevention method that is simple to use and does not require medical intervention or a strict daily regimen. We show that silk fibroin protein can be formulated into insertable discs that encapsulate either an antibody (IgG) or the potent HIV inhibitor 5P12-RANTES. Several formulations were studied, including silk layering, water vapor annealing and methanol treatment to stabilize the protein cargo and impact the release kinetics over weeks. In the case of IgG, high concentrations were released over a short time using methanol treatment, with more sustained results with the use of water vapor annealing and layering during device fabrication. For 5P12-RANTES, sustained release was obtained for 31 days using water vapor annealing. Further, we show that the released inhibitor 5P12-RANTES was functional both in vitro and in ex vivo colorectal tissue. This work shows that silk fibroin discs can be developed into formidable tools to prevent HIV infection.

Regulation of Chemokine-Receptor Interactions and Functions

Inflammation is the body's response to injury or infection. As early as 2000 years ago, the Roman encyclopaedist Aulus Cornelius Celsus recognised four cardinal signs of this response-redness, heat, swelling and pain; a fifth sign is loss of function.[...].