Invited ReviewMicroscopy techniques in flavivirus research
Introduction
The Flavivirus genus within the Flaviviridae virus family comprises numerous medically important pathogens such as Yellow Fever virus (YFV), Dengue virus (DENV), West Nile virus (WNV) and Japanese Encephalitis virus (JEV). Currently, more than half of the world's population (3.6 billion), in over 100 tropical and subtropical countries are at risk of Dengue infection. Approximately 390 million Dengue cases are reported annually, of which 96 million patients suffer from the more severe form of the disease – Dengue haemorrhagic fever (DHF) and Dengue shock syndrome (DSS) (Bhatt et al., 2013). West Nile virus infection causes neuroinvasive diseases such as encephalitis, meningitis, dyskinesis, and acute flaccid paralysis that may potentially lead to death. West Nile virus infection has remained the leading cause of viral encephalitis in the United States (Centers for Disease and Prevention, 2012).
Despite recent advances in flavivirus research, vaccine and antiviral therapy for some of these infectious diseases are yet to be available. This highlights the critical need in forwarding our understanding in flavivirus replication; how they infect and subjugate host cells for their own replication, and cause pathological changes. As the average diameter of flaviviruses is approximately 50 nm, microscopy techniques are proven to be one of the most powerful tools in acquiring knowledge on these nanoscopic pathogens. Through direct visualization, the induced pathological changes within infected cells can be dissected. Together with complementary biochemical and molecular studies, microscopy can expedite the development of promising vaccines and antiviral candidates to treat these potentially fatal diseases. In this review, we will provide brief introductions to the principles behind various microscopy techniques, updates on their latest applications in the context of flavivirus research, and discuss how recently developed microscopy techniques can potentially help advance our understanding in these enveloped viruses.
Section snippets
Bright field light microscopy – morphology of flavivirus-infected cells
The field of microscopy started in the 17th century with the invention of the first microscope by Antonie van Leeuwenhoek. Since then, light microscopes have remained the principle workhorse in Microbiology to date. In Virology, conventional light microscopes are commonly used to examine the stage of virus infection at the cellular level. This is no exception to the study of flaviviruses. Generally, cell death is the ultimate fate of flavivirus-infected cells although persistent infection has
Acknowledgements
We will like to acknowledge Carl Zeiss Imaging Centre (National University of Singapore) and Singapore Bioimaging Consortium (SBIC)-Nikon Imaging Centre for the access to their microscopes, and the kind technical assistance and advices provided by their staff. We will also like to thank the Journal of NanoBiotechnology (BioMed Central) for their permission to reprint the AFM figures.
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