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The filoviruses, which include the marburg- and ebolaviruses, have caused multiple outbreaks among humans this decade. Antibodies against the filovirus surface glycoprotein (GP) have been shown to provide life-saving therapy in nonhuman primates, but such antibodies are generally virus-specific. Many monoclonal antibodies (mAbs) have been described against Ebola virus. In contrast, relatively few have been described against Marburg virus. Here we present ten mAbs elicited by immunization of mice using recombinant mucin-deleted GPs from different Marburg virus (MARV) strains. Surprisingly, two of the mAbs raised against MARV GP also cross-react with the mucin-deleted GP cores of all tested ebolaviruses (Ebola, Sudan, Bundibugyo, Reston), but these epitopes are masked differently by the mucin-like domains themselves. The most efficacious mAbs in this panel were found to recognize a novel “wing” feature on the GP2 subunit that is unique to Marburg and does not exist in Ebola. Two of these anti-wing antibodies confer 90 and 100% protection, respectively, one hour post-exposure in mice challenged with MARV., Author Summary The filoviruses have caused multiple outbreaks among humans this decade, including a 90% lethal outbreak of Marburg virus in Angola and a significant, sustained outbreak of Ebola virus in West Africa. The viral surface glycoprotein (GP), which enables filoviruses to infect host cells, is the primary target of the immune system. Antibodies that target filovirus GP have been shown to provide life-saving therapy in nonhuman primates. However, the majority of known antibodies are only reactive against Ebola virus and not other emerging filoviruses. In this study, we present ten antibodies against Marburg virus, elicited by immunization of mice using engineered forms of its GP. Surprisingly, two antibodies exhibit some cross-reactivity to ebolaviruses (including species Ebola, Sudan, Bundibugyo, Reston). Other antibodies in this panel recognize a novel “wing” feature on a portion of GP that is unique to Marburg and does not exist in ebolaviruses, and protect 90%-100% of mice from lethal exposure. These antibodies, and their structural and functional analysis presented here, illuminate directions forward for therapeutics against Marburg virus.

There is an error in the 18th author's name; the middle initial is missing. The correct name is Jody D. Berry. This author's affiliation is also incorrect. The correct affiliation is: Cangene Corp, now a subsidiary of Emergent Biosolutions. Winnipeg, Manitoba, Canada. This author's current address is: Proteos, Inc., Kalamazoo, MI

The filoviruses Marburg virus and Ebola virus (EBOV) quickly outpace host immune responses and cause hemorrhagic fever, resulting in case fatality rates as high as 90% in humans and nearly 100% in nonhuman primates. The development of an effective therapeutic for EBOV is a daunting public health challenge and is hampered by a paucity of knowledge regarding filovirus pathogenesis. This report describes a successful strategy for interfering with EBOV infection using antisense phosphorodiamidate morpholino oligomers (PMOs). A combination of EBOV-specific PMOs targeting sequences of viral mRNAs for the viral proteins (VPs) VP24, VP35, and RNA polymerase L protected rodents in both pre- and post-exposure therapeutic regimens. In a prophylactic proof-of-principal trial, the PMOs also protected 75% of rhesus macaques from lethal EBOV infection. The work described here may contribute to development of designer, “druggable” countermeasures for filoviruses and other microbial pathogens., Synopsis Ebola virus (EBOV) causes a highly lethal hemorrhagic fever that results in up to 50%–90% mortality in humans. There are currently no available vaccines or therapeutics to treat EBOV infection. To date, multiple pre- and post-exposure therapeutic strategies, primarily focused on bolstering the host immune response or inhibiting viral replication, have been undertaken with limited success. Here, Bavari and colleagues report the development of a successful therapeutic regimen for EBOV infection based on antisense phosphorodiamidate morpholino oligomers (PMOs). PMOs are a subclass of chemically modified antisense oligonucleotides that interfere with the translation of viral mRNA, thus inhibiting viral amplification. Using a cell-free translation system, a cell-based assay, and survival studies in rodents, we identified several efficacious EBOV-specific PMOs. Further, prophylactic administration of a combination of three EBOV-specific PMOs specifically targeting VP24, VP35, and the viral polymerase L protected rhesus macaques from lethal EBOV infection. This is the first successful antiviral intervention against filoviruses in nonhuman primates. These findings may serve as the basis for a new strategy to quickly develop virus-specific therapies in defense against known, emerging, and genetically engineered bioterrorism threats.