Applications of gold nanoparticles in virus detection

Draz, Mohamed Shehata; Shafiee, Hadi

Hepadnaviridae comprises two main genera, Orthohepadnavirus and Avihepadnavirus. The genus Orthohepadnavirus includes 4 species (HBV, woodchuck hepatitis virus, ground squirrel hepatitis virus, and woolly monkey HBV) that infect mammals, while the genus Avihepadnavirusincludes2 species (duck HBV and heron HBV) infect birds [144] . Hepadnaviruses are spherical, enveloped DNA viruses 40-48 nm in size. They possess a unique gapped genome of 3.2-kb circular dsDNA, which contains 4 partly overlapping ORFs encoding the different viral proteins: the core protein (C), e antigen, polymerase protein (Pol), envelope proteins, and transcriptional transactivator protein [144, 145] . The prototype member of the family Hepadnaviridae, HBV, is a health threat to ~88% of the global population [145, 146] . HBV is the etiological agent of hepatitis type B in humans. It is estimated that nearly 2 billion people around the world have been exposed to HBV infection, and there are more than 360 million chronic carriers suffering from the serious risk of developing liver cirrhosis and cancer [146, 147] . The availability of an effective protective vaccine against HBV has greatly reduced the number of new infections. In addition, there have been significant advances in the available treatments for chronic HBV infection. Viral DNA polymerase inhibitors and PEG-IFNα are now well known to significantly control HBV infection and prevent its progression to chronic hepatitis B-associated liver failure and hepatocellular carcinoma [148, 149] . However, chronic HBV infections remain highly contagious, and the virus can easily be transmitted to other persons through any close contact allowing the transfer of infected bodily fluids. The highly contagious nature of HBV and its ability to spread among people are the main reasons why this pathogen continues to threaten the public. Therefore, diagnostic methods that are highly sensitive to low concentrations of virus are needed to curtail this virus and prevent its dissemination.