Designing a thermally stabilised RH5

Can we use a one-stop protein design platform to improve an RH5-based vaccine?

With the RH5 molecule moving into human clinical trials, conducted by Simon Draper’s group, we wanted to see if we could use structural insight to make it better. In particular, RH5 is not easily expressed, requiring relatively costly insect cell expression systems in which it is produced at low levels. Thermal stability and inexpensive production are both desirable for a malaria vaccine.

rh5 thermo

We therefore teamed up with Adi Goldenzweig and Sarel Fleishman from the Weizmann Institute. Adi and Sarel produced the PROSS (protein repair one-stop shop) algorithm which combines structural insight with assessment of variation in protein sequence to guide Rosetta-based protein design. They used this procedure to design RH5 variants containing ~20 different changes, predicted to stabilise the protein structure. Residues critical for basigin binding, or forming parts of important antibody epitopes, were left unchanged.

Ivan Campeotto then assessed these designs. He showed that PROSS-designed RH5-variants were expressed in simple bacterial expression systems in a functional folded form. Their structure, affinity for basigin and ability to induce growth inhibitory antibodies were unaltered. However, their thermal stability was increased by around 15°C.

A one-stop structure-guided design could therefore improve both the thermal stability and the ease of production of an RH5-based vaccine. 

Campeotto, I., Goldenzweig, A., Davey, J., Barfod, L., Marshall, J.M., Silk, S.E., Wright, K.E., Draper, S.J., Higgins, M.K.* and Fleishman, S.J.* (2017) One-step design of a stable variant of the malaria invasion protein RH5 for use as a vaccine immunogen. Proc Natl Acad Sci U S A. 114 998-1002 (* joint corresponding).