None.
This invention relates to a method for screening potential anti-viral compounds. In particular, the present invention is an assay for testing a compound""s ability to inhibit uncoating of protein-coated double-stranded DNA (dsDNA) viruses.
Viral infections have proven to be especially challenging for the medical field. So far, research has failed to find a cure for a viral infection, and many times the best that can be done is to relieve the symptoms associated with the illness. Even vaccines against viruses are not totally effective at blocking an infection. Therefore, attention has focused on stopping a viral infection during its initial stages of infection. This stops further spread and prevents the infection from developing into a productive disease state.
Protein-coated dsDNA viruses make up a class of viruses which have a wide spectrum of effects. Some are harmless while others cause life-threatening conditions. Families of viruses that are included are Papovavirus, Polyomavirus, Adenovirus, and Herpesvirus. Human Papilloma Virus (HPV) is a serious human pathogen that is thought to be the causative agent of a vast majority of diagnosed cervical cancers, and it falls into this category of viruses. Another example is Herpesvirus, which, though not usually life-threatening, can be very devastating.
The infection process of these similarly structured protein-coated dsDNA viruses is believed to be the same within all viral families that fall into this group. The process has been divided into three stages: adsorption to the surface of the cell, penetration of the cell membrane and transport to the nucleus, and uncoating (removal of capsid proteins) within the nucleus. Using a combination of biochemical fractionation and electron microscopy. the first two stages have been relatively well characterized. For example, these types of methods were used to study the Simian Virus 40 (SV40) and polyoma viruses. Both viruses followed a similar pattern where the majority of infecting virus was found on the cell surface fifteen minutes postinfection and maximal transport to the nucleus occurred at three hours postinfection.
Viral uncoating has not been as well studied. Previous notions were that all virus that entered a cell was opened up, or uncoated, simply as a consequence of being inside the cell. The idea has recently emerged, however, that the process of uncoating is regulated and active and, thus, theoretically can be inhibited. Developing a system for screening and identifying compounds that inhibit this process would, therefore, be very advantageous in progressing available viral drug therapies.
The invention is an assay for identifying compounds that have anti-viral activity. Susceptible host cells are exposed to a potential viral inhibitor and then infected with a virus. The host cells are incubated to allow the virus to be transported to the nucleus and uncoated. The percentages of input virus appearing as intact virus and uncoated viral chromatin is determined. An effective inhibitor shows a decrease in uncoated viral chromatin with a corresponding increase in intact virus.