Chimpanzee adenovirus vaccine protects against Marburg virus

Colourised scanning electron micrograph of Marburg virus particles

An experimental vaccine against Marburg virus (MARV) was proved to be safe and induced an immune response in a small, first-in-human clinical trial. 

In areas of Africa where a vaccine for Marburg is most needed, a single-dose vaccine that could protect recipients over a long period of time would be a crucial part of quelling outbreaks. 

The vaccine was developed by researchers at the National Institute of Allergy and Infectious Diseases (NIAID), part of the National Institutes of Health. 

This first-in-human, Phase I study tested an experimental MARV vaccine candidate, known as cAd3-Marburg, which was developed at NIAID’s Vaccine Research Center (VRC).  

The vaccine uses a modified chimpanzee adenovirus called cAd3, which can no longer replicate or infect cells, and displays a glycoprotein found on the surface of MARV to induce immune responses against the virus.  

The cAd3 vaccine platform demonstrated a good safety profile in prior clinical trials when used in investigational Ebola virus and Sudan virus vaccines developed by the VRC. 

MARV, a filovirus in the same family as Ebola virus, causes a rapidly progressive febrile illness that leads to shock and death in a large proportion of infected individuals. No approved vaccines or specific therapies are available for MARV disease, aside from supportive care. While some experimental vaccines have previously been tested, none have proven to be both highly effective and to provide durable protection.  

The Phase I study

In this study, 40 healthy adult volunteers were enrolled at the Walter Reed Army Institute of Research Clinical Trials Center in Silver Spring, Maryland. They received a single dose of either a low dose of the vaccine (1×1010 particle units) or a higher dose (1×1011 particle units). For safety, the volunteers were enrolled in a dose-escalation plan. 

The investigational vaccine appeared to induce strong, long-lasting immunity to the MARV glycoprotein: 95% of participants in the trial exhibited a robust antibody response after vaccination, and 70% maintained that response for more than 48 weeks. 

Plans are in place to conduct further trials of the cAd3-Marburg vaccine in Ghana, Kenya, Uganda, and the United States. 

Read the original article from The Lancet: Safety, tolerability, and immunogenicity of the Marburg chimpanzee adenovirus vector vaccine (cAd3-Marburg) in healthy adults: a phase 1, open-label, dose-escalation trial. 

Image shows: Colourised scanning electron micrograph of Marburg virus particles (blue) both budding and attached to the surface of infected VERO E6 cells (orange). Credit: NIAID.

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