Marburg virus (MARV) and Ebola virus (EBOV), members of the family Filoviridae, represent a significant challenge to global public health. Currently, no licensed therapies exist to treat filovirus infections, which cause up to 90% mortality in human cases. To facilitate development of antivirals against these viruses, we established two distinct screening platforms based on MARV and EBOV reverse genetics systems that express secreted Gaussia luciferase (gLuc). The first platform is a mini-genome replicon to screen viral replication inhibitors using gLuc quantification in a BSL-2 setting. The second platform is complementary to the first and expresses gLuc as a reporter gene product encoded in recombinant infectious MARV and EBOV, thereby allowing for rapid quantification of viral growth during treatment with antiviral compounds. We characterized these viruses by comparing luciferase activity to virus production, and validated luciferase activity as an authentic real-time measure of viral growth. As proof of concept, we adapt both mini-genome and infectious virus platforms to high-throughput formats, and demonstrate efficacy of several antiviral compounds. We anticipate that both approaches will prove highly useful in the development of anti-filovirus therapies, as well as in basic research on the filovirus life cycle.

In 2012, a female wildlife biologist experienced fever, malaise, headache, generalized myalgia and arthralgia, neck stiffness, and a sore throat shortly after returning to the United States from a 6-week field expedition to South Sudan and Uganda. She was hospitalized, after which a maculopapular rash developed and became confluent. When the patient was discharged from the hospital on day 14, arthralgia and myalgia had improved, oropharynx ulcerations had healed, the rash had resolved without desquamation, and blood counts and hepatic enzyme levels were returning to reference levels. After several known suspect pathogens were ruled out as the cause of her illness, deep sequencing and metagenomics analysis revealed a novel paramyxovirus related to rubula-like viruses isolated from fruit bats.

Recent investigations have shown the Egyptian fruit bat (Rousettus aegyptiacus) to be a natural reservoir for marburgviruses. To better understand the life cycle of these viruses in the natural host, a new reverse genetics system was developed for the reliable rescue of a Marburg virus (MARV) originally isolated directly from a R. aegyptiacus bat (371Bat). To develop this system, the exact terminal sequences were first determined by 5' and 3' RACE, followed by the cloning of viral proteins NP, VP35, VP30 and L into expression plasmids. Novel conditions were then developed to efficiently replicate virus mini-genomes followed by the construction of full-length genomic clones from which recombinant wild type and GFP-containing MARVs were rescued. Surprisingly, when these recombinant MARVs were propagated in primary human macrophages, a dramatic difference was found in their ability to grow and to elicit anti-viral cytokine responses.