There are nine human herpesvirus (HHV) pathogens that cause significant worldwide morbidity and mortality with treatment costs in the billions of dollars annually. Their ubiquitous nature contributes to primary infection early in life and most adults permanently harbor one or more latent herpesvirus species. Primary disease ranges from asymptomatic to self-limiting (herpes labialis) to life-threatening (cancer). The PI studies a series of non-toxic, non-nucleoside small molecule antiviral drug candidates (PORT compounds) with a unique mechanism of action: inhibition of viral DNA packaging by targeting the viral portal protein. The proposed studies seek to exploit the remarkable structural and functional relatedness of herpesvirus portals. During herpesvirus genome replication, concatamers of viral dsDNA are cleaved into single length units by a virus-encoded terminase and packaged into procapsids through a channel located at a single capsid vertex - the portal. The portal is absolutely required for viral replication. In all cases, function is highly conserved in that portals are essential for DNA packaging and play a role in releasing viral DNA during infection. Our recent findings, which are the basis of this grant application, show that PORT 1 can prevent viral replication in human and animal species in all three herpesvirus subfamilies (alpha, beta and gamma). The remarkable structural conservation of the portal protein core for all herpesvirus species across all three sub- families may provide an opportunity to develop a broad-spectrum HHV drug. Furthermore, a drug with a completely different mechanism than nucleoside analogs (e.g. acyclovir) would have great clinical value for treating drug resistant herpesviruses. A broad-spectrum anti-herpesviral drug could be used to treat more than one herpesvirus infection at one time ? particularly in immunocompromised cancer and transplant patients, and fill the need for alternative or first generation therapies for certain herpesviruses (EBV and CMV). We propose four complementary Aims to further these studies.
Aim 1 will include synthesis and testing of PORT 1 in vitro activity against alpha, beta, and gamma herpesviruses. PORT1 mechanism of action will be confirmed via TEM by showing that cells infected by a virus from any HHV subfamily contain only empty capsids.
Aims 2 -4 were conceptualized based on the hypothesis that PORT 1 exhibits broad-spectrum activity against human and animal herpesviruses. Preliminary data are provided showing that PORT 1 has significant in vitro activity against murine cytomegalovirus and murine gammaherpesvirus 68. These results were not unexpected based on the remarkable structural and functional relatedness of ALL herpesvirus portals.
Aims 2 -4 will test the in vivo efficacy of the lead broad spectrum PORT 1 compound activity against herpes-viruses from all three subfamilies. In the spirit of the NIH REAP grant mechanism, these studies will provide an exciting, mentored laboratory experience for undergraduate, graduate and medical student researchers.
There are nine different herpesviruses (Herpes simplex types 1 and 2, Varicella-zoster virus, Epstein-Barr virus, Human Cytomegalovirus, Human herpesvirus types 6a, 6b, 7 and Kaposi?s Sarcoma virus) that cause mild to severe disease in humans. Our laboratory is interested in a series of novel small molecules that prevent infectious viral particles from forming in infected cells. The discovery of a broad-spectrum, anti-herpesviral drug with few side effects and a novel mechanism of action would fill an important unmet clinical need.
