The structural viral proteins can be amended to present foreign antigens on the surface of the VLP. As the antigens are presented in a highly repetitive and native structure, VLPs induce a strong immunogenic response both humoral and cellular, even in the absence of any adjuvant. VLPs are self-assembled spherical particles of viral structural proteins, mimicking the overall appearance and structure of a native virus and due to a lack of genetic material are unable to replicate or infect, making them generally safe. Promising future vaccine candidates that incorporate most of the desired properties are virus-like particles (VLPs). Conventional vaccines such as inactivated and attenuated viruses however, have a lengthy production time, expensive production costs and might be risky for people with immunodeficiency. Another important point that is often neglected is the need for low production costs, thus enabling affordable to use in low income countries, which often suffer the most from infectious diseases and otherwise may function as a residual reservoir for global threat. An ideal vaccine candidate to do so is highly immunogenic, exceptionally safe and can be quickly mass produced. Once emerged a sustainable control can only be achieved by mass vaccination as demonstrated for example for Polio and Measles. can spread rapidly so keeping a local outbreak under control is challenging. In a globally-mobile world pathogens such as corona virus, influenza virus, Ebola virus etc. The current outbreak of COVID-19 shows dramatically the threat of global pandemics and the need for potent vaccines that can be mass-manufactured efficiently. High throughout studies allowed the screening of a vast design space within weeks, rather than months, and unveiled complicated binding behaviour for Capto TM MMC. Purified capsid protein could be easily assembled in-vitro into well-defined virus-like particles by lowering pH with addition of calcium chloride to the eluate.
Modular polyomavirus major capsid protein could be purified within hours using the optimised process achieving purities above 87% and above 96% with inclusion of an initial precipitation step. Samples derived from each purification process were thoroughly characterized by RP-HPLC, SEC-HPLC, SDS-PAGE and LC-ESI-MS/MS Mass Spectrometry analytical methods. A dynamic binding capacity of 14 mg ml −1 was achieved for Capto™ MMC resin. High throughput process technology studies were conducted to optimise binding and elution conditions for multi modal cation exchanger, Capto™ MMC and strong anion exchanger Capto™ Q. The major contaminants like host cell proteins, DNA and aggregates can be efficiently removed by the optimised strategy, without the need for a size exclusion polishing chromatography step, which otherwise could complicate the process scalability and increase overall cost. This approach allows an integrated process without any buffer adjustment between the purification steps. Among the methods, the optimised purification strategy consists of an anion exchange step in flow through mode followed by a multi modal cation exchange step in bind and elute mode. In this study, we investigated alternative purification pathways to identify and optimise a suitable purification pathway to overcome some of the current challenges. There are many described protocols for the purification of microbially-produced viral protein in the literature, however, they suffer from inherent limitations in efficiency, scalability and overall process costs. Modular virus-like particles and capsomeres are potential vaccine candidates that can induce strong immune responses.
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