Virus-like particles (VLP) provide an alternative approach to traditional vaccines due to their high immune response, self-adjuvating behavior, neutralization, and safety profiles. VLPs are non-infectious multiprotein structures that mimic the native viruses but lack the disease-causing viral genome making them safer vaccine candidates. Due to their optimal size (20-200nm), they can practically display any epitope in a multivalent format that virtually guarantees the high humoral or cell-mediated immune response in the host. Overall, VLPs are sensed by pathogen recognition receptors (PRRs) present either on cell surface or endosomes of dendritic cells (DC). VLP uptake prompts DC maturation and presentation of peptides along with major histocompatibility complex (MHC) class I or class II molecules for inducing CD8+ or CD4+ T cell responses, respectively. Therefore, VLP-based vaccines are capable of inducing both humoral and cellular immune responses. Besides, VLPs can be produced in a range of production systems, and this provides flexibility in tailoring manufacturing conditions3. Removal of immunosuppressive epitopes from VLP could further enhance their potency and efficacy. Since VLPs provide a protective response at lower doses, they could significantly reduce vaccine cost.
In developing VLP-based vaccines, serious considerations should be given to a robust and faithful production platform that enables the delivery of vaccines in a timely and reproducible manner. As the significance of VLPs has been appreciated for developing next-generation vaccines, several expression platforms for producing VLPs have been developed, including bacteria (Escherichia coli), yeast, insect cells, mammalian cells, and plants. The comparison of the bacteria, yeast, insect, mammalian and plant expression systems and production of several eVLPs-based vaccine candidates tested in pre-clinical trials are summarized in Table 1-3.
A broad range of protein expression systems is currently available, mostly based on cellular organisms of prokaryotic and eukaryotic origin. Limitations of prokaryotic systems occur when complex mammalian target proteins requiring posttranslational modifications, cofactors, and chaperones for correct protein folding, assembly, and activity need to be produced. At the same time, the generation of eukaryotic stable cell lines for protein production purposes is quite laborious due to slow cell growth and low protein yields apart from high production time, thereby leading to costly protein production processes.
To overcome these limitations, Premas Biotech, India, has developed a novel platform D-Crypt™, the world's first integrated platform technology that focuses on DTE-Ps (Difficult to Express Proteins) and membrane proteins, the proteins that account for more than 70% of drug targets. D-Crypt™ has been used to successfully express all three kinds of membrane proteins, ranging in size from 2 to 24 transmembrane domains. In addition, large, multidomain proteins, as well as those with a solution and membrane-bound parts, have been expressed on D-Crypt™.
The platform combines a yeast expression host with over 20 custom-made expression vectors. This proprietary vector directs the insertion of a full-length or truncated polynucleotide sequence encoding the desired target protein into the host cell. The strain is the protease-deficient strain of Baker’s yeast, S. cerevisiae, which provides an ideal eukaryotic environment for expressing recombinant proteins retaining their correct structure, and function. Premas proprietary expression vectors of this platform contain changed upstream regions. To rapidly modify recombinant proteins, genetic variants can be easily integrated into expression vectors. These innovations make it possible to co-express numerous recombinant proteins in controlled quantities, ensuring their functionality. Besides, the yeast culture systems have been granted GRAS (generally recommended as safe) status from the U.S. Food and Drug Administration (USFDA), facilitating rapid regulatory approval and straightforward technology transfer to Premas partners.
24 October 2021
In 2020, the World Health Organisation (WHO) listed reluctance to vaccinate despite their availability as one of the top ten global health threats. As per the report, about 80% of people worldwide think vaccines are both safe and effective. In contrast, the remaining 20% of people are worried and can potentially influence others.Read More