International HBV Meeting: Primary Cell Screening Assays, HAV Outbreak, and HBV Stock Production

by Robert W. Buckheit III, Ph.D.

September 13, 2017

Members of ImQuest BioSciences' scientific team recently returned from the International HBV Meeting in Washington DC. The annual meeting sponsored by the Hepatitis B Foundation, focused on the molecular biology of HBV and the development of novel treatment strategies to combat the virus. Hepatitis B virus (HBV) infection can cause both acute and chronic liver disease, with an estimated 250 million people infected, resulting in over 880,000 deaths in 2015 alone. While an effective vaccine has been available for 35 years, the need for viable treatment options to use in many under-developed regions of the world remains. At the meeting, scientists from academic groups, non-profit organizations and biotech companies presented new data on the function of HBV accessory proteins, the establishment and maintenance of cccDNA, improvements in animal models for hepatitis infection, and advances in the development of novel therapeutics. We appreciated the opportunity to meet with our colleagues in the field of antiviral and HBV drug and vaccine development, and look forward to working in partnership to assist the development of novel HBV therapeutic products.

The conference also featured keynote sessions and updates on related, liver-specific viruses, such as Hepatitis A, Hepatitis E and Hepatitis D virus. Updates on these related viruses could not have come at a more opportune time, as public health officials in San Diego are continuing to combat a deadly outbreak of Hepatitis A virus (HAV) in the city, predominately affecting the homeless population due to lack of access to sanitary facilities. Efforts to contain this spread of HAV in San Diego continue into this week. This public health event comes on the heels of a multi-state occurrence of HAV infections last year, that was linked to the import of frozen strawberries. Of note, ImQuest has recently developed a qPCR-based assay that allows the rapid and robust assessment of anti-HAV therapeutic products, and this technology is available for immediate use by companies interested in the development of anti-HAV therapeutic agents. Contact us to learn more and to screen compounds.

ImQuest also had the opportunity to present a poster detailing our development of a robust, reproducible, microtiter-based in vitro system to screen anti-HBV compounds utilizing primary human hepatocytes (PHHs). This assay was initially developed using the chronically infected cell lines AD38 and HepG2.2.15 and has been used extensively to screen for effective antiviral agents against HBV infection. While the AD38 and HepG2.2.15 assay remains a reliable and robust assay for screening, the fact remains that utilizing chronically infected target cells renders the assay incapable of assessing agents that might result in inhibition of the early stages of the viral infection, including virus entry, un-coating and initial cccDNA formation. To this end we developed our assay using PHH grown in collagen-coated plates, which we infect with infectious HBV produced at ImQuest. These infected primary hepatocytes can then be used to screen for antiviral compounds targeting multiple markers of HBV infection, yielding data on compound efficacy, toxicity and potential mechanism of action simultaneously. Given the nature of the assay, we can adjust the timing of the infection and compound addition such that we can assess the formation of many of the markers of HBV replication in target cells, such as early cccDNA formation, the emergence of the pre-genomic RNA (pgRNA), as well as the translation and reverse transcription products of the pgRNA. The ability to optimize the timing of the infection compared to compound addition has proved critical to the precise assessment of the emergence of particular HBV markers. The use of PHH in an infection assay most closely resembles the natural HBV infection and thus is the gold standard for antiviral agent screening for both acute and chronic infection inhibitors of HBV replication and transmission. (Click here to view our poster presented at the International HBV meeting detailing the PHH Screening Method).

ImQuest also has the capability to produce HBV stocks and can routinely achieve virus concentrations of approximately 5x1010 genome equivalents per milliliter. We can produce crude virus preparations ascwell as highly concentrated virus utilizing tangential flow filtration technology. This service is available for HBV and a variety of other viral systems, and can be customized to fit our clients’ needs.

We look forward to next year’s International HBV Meeting in Italy and hope to continue to work in partnership with the international community to identify and develop novel therapeutic products to target and treat Hepatitis B virus infection. Contact us to learn more about our HBV, HAV and other antiviral services, as well as to inquire about our Virus Stock Production and Expansion programs.

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