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.
