Research in The Lancet Microbe in February 2023 presents a positive update from an NIH group with their vaccine candidate against Sudan virus (SUDV). Based on the licensed Ebola virus (EBOV) vaccine, the new vaccine VSV-SUDV demonstrated efficacy in cynomolgus macaques. Following the outbreak of SUDV in Uganda, declared over in January 2023, research into a safe and effective vaccine has accelerated. No treatment or vaccine is licensed.
The outbreak in Uganda
The study highlights the focusing of “public attention” on filoviruses following the outbreak of SUDV in Uganda towards the end of last year and into 2023. SUDV has an estimated case fatality rate of 50%, with the recent outbreak conforming to the trend. As we observed at the end of the outbreak, a number of vaccine candidates are in clinical trials, with the expectation of testing before the outbreak was successfully contained.
The authors note that “EBOV-specific vaccines” are “not expected to be effective against SUDV infections due to the absence of cross-protective immune responses”. Thus, it is essential to develop an alternative, SUDV-specific, vaccine.
VSV-SUDV in trial
The vaccine is developed by scientists at NIAID in Montana. It is a live attenuated vector vaccine using genetically engineered vesicular stomatitis virus (VSV) to express an SUDV protein as a single-dose vaccine.
The researchers tested the vaccine’s safety and efficacy in macaques, involving 11 animals. Each of the animals had received the EBOV vaccine 9 months prior to the study. 6 were vaccinated with VSV-SUDV, while 5 control animals were vaccinated with VSV-MARV, a vaccine candidate in development for Marburg virus.
NIH reports that after 28, “during which no animals showed adverse effects”, the macaques were challenged with a “lethal dose SUDV”. None of the animals that had been vaccinated with VSV-SUDV showed signs of disease, but 4 of the 5 control animals “developed clinical signs of Sudan virus disease”.
The scientists were “surprised” that one of the control animals responded similarly to the vaccinated animals and they plan further studies to investigate cross-protective immune responses. The study concludes that the vaccine “completely protects” against lethal SUDV challenge and is a “potent candidate for clinical trials.
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