Towards an in vitro system of predictive biomarkers of in vivo liposome efficacy

点击翻译按钮获取中文摘要

Vaccines are designed to induce protective immune responses in individuals without the need for natural infection. They contain 'antigens' (whole pathogens or sub-units of pathogens) against which an immune response is desirable. Adjuvants are an important component of vaccines, especially those that do not contain live pathogens, as adjuvants increase the efficacy of the antigenic material that is provided. Given that 'live vaccines', due to their less tolerable safety profile, are rejected in favour of more advanced sub-unit and DNA vaccines, adjuvants thus play a key role in vaccine development. There are a range of different adjuvants currently available but the use of liposomes (a hollow 'bag' of lipid) are highly attractive as they have the advantage that they are both adjuvant in nature and also have the capacity to deliver antigens (e.g. within the hollow core or on their surface). This project is directed towards the effective in vitro screening of liposomes for the identification of more effective adjuvant preparations.With every new vaccine formulation, many in vivo tests are essential to ensure efficacy and safety of the vaccine. Thus the generation of novel liposome formulations has tended to be evolutionary rather than revolutionary i.e. minor modifications based on a formulation that has shown some use. Such an incremental approach is slow and the ability to screen large libraries of formulations will speed the development of new and more effective vaccines for the prevention of a range of important diseases (e.g. TB, HIV, malaria and chlamydiae). However currently, large-scale screening is prohibitively expensive in animals and man-hours.In this project we will test liposome formulations that have already been tested in vivo (ranging from effective-ineffective) including formulations with varying physical and chemical characteristics and those that generate different 'types' of immune responses, so called Th1 and Th2 responses. This will allow us to data mine both effective and ineffective responses without further in vivo studies. Generation of the appropriate 'type' of immune response for each disease is critical to the success of any vaccine. For example, Th1 responses protect against pathogens such as viruses that live within cells and thus a Th2 response would not be desirable. We will test our liposomes in a range of in vitro tests and by integrating the results in a 'systems biology' approach, we will identify a 'fingerprint' of in vitro biological activity that is predictive of in vivo efficacy. This will save the use of very significant numbers of animals and will improve the drug-discovery pipeline, as we will then be able to efficiently screen large libraries of formulations to identify leads for further work. This project will thus speed the development of novel liposomes and vaccines.Our unique panel of in vitro assays has been carefully selected to be relevant to the generation of immune responses. Once a vaccine is injected, a vaccine must attract and activate key immune system cells known as antigen presenting cells (APC). Consequently we will assess in vitro the behavior of APC in the presence of each liposome. We will assess (A) migration of APC to liposomes; (B) association of liposomes with APC; (C) liposome-activation of APC (that are usually quiescent) and (D) correlate the in vitro results with known in vivo efficacy.Our approach will identify key in vitro markers of in vivo efficacy of liposomes. This 'biomarker fingerprint' will then be used in future work to screen libraries of formulations in vitro for likely in vivo efficacy. This approach will identify key biomarkers of effective in vivo preparations of liposomes. The net effect of this will be to speed and make more efficient the vaccine development pipeline with significant beneficial impact for human health.