“Two 7U stocks can be very different – for example one predominantly 7U stock with around 50% 7U and another 7U stock with around 98%,” Geisber said. “The only way to know for sure is to deep sequence them.”
Viruses with high populations of 7U cause a more rapid disease in macaques and are theoretically more difficult to protect against, he said. However, “past studies performed with viruses containing higher populations of 7U viruses using other MAbs did not protect [non-human primates] against Ebola-Zaire, whereas studies using different antibodies containing high populations of 8U did. It is hard to say whether the difference is because of the antibodies or the virus used.
“My gut feeling is that the difference is because virus stocks with high populations of 7U are more pathogenic in primates and harder to protect against.”
While Geisbert thought the use of siRNAs was more promising, treating Ebola could come down to a combination of “the most promising treatments -like HIV treatments – combined,” he said.
Kobinger said the study used a 7U virus that contained around 80% of the wild type population. The next step would be to work with another leading antibody team to find an “even more potent cocktail” to extend the treatment window.
siRNAs were effective but “a proof of concept” that didn’t fit with real world conditions, he said. “[They are] best when injected everyday for seven days, but treatment has to be initiated within 30 minutes after infection to reach 100% … Even within a lab contamination, this might be unrealistic. In the real world we need to go past 24 hours.”
Ebola first emerged in Sudan and Zaire (now the Democratic Republic of the Congo) in the mid-1970s. Since then five strains have been identified: Zaire (1976), Sudan (1976), Reston (1989) Côte d’Ivoire (1994) and Bundibugyo (2007) – each named after where they were first discovered. Reston, discovered in Virginia in the US and later in pigs in the Philippines (and antibodies in a few pig farmers) isn’t known to cause hemorrhagic fever in humans. Ebola Côte d’Ivoire was discovered after a scientist contracted the infection from an autopsy on a dead chimpanzee.
Antoine Wystrach does not work for, consult to, own shares in or receive funding from any company or organization that would benefit from this article, and has no relevant affiliations.