VIRUSES/VACCINES

TRULY QUANTITATIVE MEASUREMENT OF TOTAL TITER AND SUBGROUP TITER OF VIRUS

Author: Nanofcm     Date: November 26, 2021

Virus is a general term for a group of tiny organisms that are made up of non-cellular forms of nucleic acid molecules (DNA or RNA) and proteins and live in parasitic life. Although viruses are small in size (20-200 nm), they are by far the most abundant ‘lifeforms’ in nature, and also the chief culprit of many fatal diseases. The pandemic caused by COVID-19 (SARS-CoV-2) has led to dramatic loss of human lives globally, and presents an unprecedented challenge to public health. An interpretation of the biological structure and function of novel Coronavirus and an efficacious vaccine are essential to prevent further morbidity and mortality. On the other hand, viruses have also been used more positively in the medical field. Virus particles have many natural characteristics that can be applied to nanobiology and nanomedicine, and there are unprecedented opportunities for related applications based on the properties of virus nanoparticles. Oncolytic viruses, a typical branch of new immuno-therapeutic agents, rely on both the selective tumor cell killing and the induction of systematic antitumor immunity to achieve antitumor responses, has shown great promise in tumor treatment, especially when combing with other therapies like immune checkpoint inhibitors. As an advanced targeted cancer therapy, chimeric antigen receptor (CAR) T cell therapy has unexpectedly fueled an increasing number of clinical trials for cancer treatment, and encouraging progress has been made continuously. Lentivirus has been extensively used as the gene delivery vector to transfer CAR gene to T cells. Moreover, adeno associated viruses (AAV) are also common vectors for gene transfer in vivo, which show great potential in therapeutic applications. Lentivirus and AAV are two most frequently used vectors for cell and gene therapy and have a lot of advantages such as excellent safety, low immunogenicity, able to infect both mitotic and non-mitotic cells, and able to mediate long-term stable gene expression. With the development of scientific research, rapid detection and accurate description of viruses have become more and more important, which is essential for the applications. The physical and chemical properties of viruses, such as size, concentration, biochemical component as well as the packaging efficiency of functional molecules would cause direct effect to their applications. Transmission electron microscopy (TEM) is still the most recognized means to measure the size and morphology of a virus despite the fact that it is labor intensive and time-consuming. Conventional plaque titer and TCID50 method are the most classical approaches for concentration measurement of infectious viruses, however, they quantify only those which cause visible cell-damage thus exclude the viruses without infectivity. Therefore, a virus analysis method which can quickly and reliably detect, quantify and characterize virus particles with single particle sensitivity is highly needed. Here, the Flow NanoAnalyzer is introduced, which can directly detect MS2 virus with particle size as low as 27 nm by light scattering. The NanoFCM platform provides a versatile and powerful platform for the multiparameter analysis of individual viruses.