Aggregation of biotherapeutic proteins- mechanism and effects on the immune response
Therapeutic protein drugs (eg monoclonal antibodies) are now well established in the treatment of many major human diseases, and constitute the most rapidly expanding class of drugs within the portfolio of most, if not all, of the major global pharmaceutical companies. Administration of recombinant human therapeutics can, however, lead to the production of anti-drug antibodies which impair drug function and, although less commonly, can lead to serious adverse health effects. The elimination, or at least reduction, of unwanted immune responses to biotherapeutics is therefore a priority within the bioprocess and biopharmaceutical industries. The presence of aggregates within biopharmaceutical preparations is a matter of concern, particularly how aggregates engage with the immune system and how this might fuel undesirable downstream immunogenicity. One approach is to use a range of biophysical and computational methods to examine how aggregation occurs in therapeutic proteins. This is an interdisciplinary collaboration, with Robin Curtis in Chemical Engineering, Jim Warwicker and Alexander Golovanov in Chemistry, and Alain Pluen in Pharmacy. We hope to obtain a greater understanding of the way in which the structure, solution conditions and dynamics impact on aggregation. We are also examining how aggregation impacts on the nature and vigour of the immune response. Recent data, collected as part of a collaboration with Ian Kimber and Rebecca Dearman in the Faculty, suggests that aggregation causes a Th1 skewing (Ratanji et al. Toxicol. Sci. 153, 258-270). We are also interested in the role which trace contaminants of remaining host cell proteins might influence the response (see Ratanji et al. Immunology, in press). Clearly, this work has direct relevance to the bioprocess industry, and we are currently working with several pharmaceutical companies in these areas.
Integral outer membrane proteins from Neisseria- from fundamental studies to vaccine components
Neisseria meningitidis is the causative agent of bacterial meningococcal meningitis and septicaemia, and is a significant public health problem in developed and developing countries. I have worked for many years towards an understanding the structure and assembly of the cell surface proteins from this organism (eg Marsay et al J Infect 71, 326-337; Saleem et al. PloS ONE 8 e0056746). Current work is aimed at using that information to develop improved vaccines against the disease. We seek to integrate protein structural studies with antigen design, through use of novel protein assemblies and scaffolds for antigen presentation.
Understanding type IV pilus assembly and natural competence in Gram-negative bacteria
Type IV pili are complex polymers, made up principally of a major pilin subunit, which extend 1-2μm from the surface of the bacterium. They are the most widespread fimbrial assembly found in Gram-negative bacteria, and are known to play important roles in cell adhesion, DNA uptake and motility. The property of twitching motility, in particular, is dependent on the rapid retraction of pili, a process which is capable of generating a powerful mechanical force. The process of pilus assembly and disassembly is driven by a powerful macromolecular machine, consisting of a complex of several proteins which span the inner and outer membranes. A fascinating aspect of type IV pili is their relationship to natural competence- the ability of bacteria to take up DNA from the external environment. Our general aim is to use a range of biochemical and biophysical methods to study how this process works at the molecular level (eg Karuppiah et al 2016 J Struct Biol. In press; Karuppiah et al 2014 J Biol Chem 289, 33187-97; Karuppiah et al 2013 PNAS pnas.1312313110; Karuppiah & Derrick 2011 J Biol Chem 286, 24434-24442)