EBola

Single animal to human transmission event responsible for 2014 Ebola outbreak

August 29, 2014
Health

Scientists used advanced genomic sequencing technology to identify a single point of infection from an animal reservoir to a human in the current Ebola outbreak in West Africa. This research has also revealed the dynamics of how the Ebola virus has been transmitted from human to human, and traces how the genetic code of the virus is changing over time to adapt to human hosts. Pardis Sabeti, M.D., Ph.D, a 2009 National Institutes of Health Director’s New Innovator awardee and her team carried out the research.

“Dr. Sabeti’s research shows the power of using genomic analysis to track emerging viral outbreaks,” said NIH Director Francis S. Collins, M.D., Ph.D. “This ability produces valuable information that can help inform public health decisions and actions.”

The 2014 Ebola outbreak is now the largest outbreak in history, with current estimates of 2,473 infections and 1350 deaths since it began in late December 2013 according to the World Health Organization. This outbreak is also the first in West Africa and the first to affect urban areas. There are no approved drugs for Ebola virus disease, though prompt diagnosis and aggressive supportive care can improve survival. The disease is characterized by high fever, headache, body aches, intense weakness, stomach pain, and lack of appetite. This is followed by vomiting, diarrhea, rash, impaired kidney and liver function and in some cases, internal and external bleeding.

To better understand why this outbreak is larger than previous outbreaks, Dr. Sabeti, senior associate member of the Broad Institute, Cambridge, Massachusetts, led an extensive analysis of the genetic makeup of Ebola samples from patients living in affected regions. Joined by an international team of scientists, Dr. Sabeti used advanced technology to analyze the genetics of the Ebola samples extremely rapidly and with high levels of accuracy. Using this technology, the researchers pinpointed a single late 2013 introduction from an unspecified animal reservoir into humans. Their study showed that the strain responsible for the West African outbreak separated from a closely related strain found in Central Africa as early as 2004, indicating movement from Central to West Africa over the span of a decade. Studying RNA changes occurring over the span of the outbreak suggests that the first human infection of the outbreak was followed by exclusive human to human transmissions.

While analyzing the genetic makeup of the Ebola samples, Dr. Sabeti and colleagues discovered a number of mutations that arose as the outbreak spread. Some of these mutations, termed nonsynonymous mutations, alter the biological state of the virus and may allow it to continually and rapidly adapt to human immune defenses as the outbreak continues. This feature points to the need for improved methods that will allow for close monitoring of changes in the viral genome and the impact on vaccine targets. Such monitoring, called genomic surveillance, can provide important insights into the biology of how the Ebola virus spreads and evolves. It may also allow scientists to develop improved methods to detect infection, and point the way to new and improved drug and vaccines.

Dr. Sabeti’s New Innovator Award is designed to support exceptionally creative new investigators conducting innovative and high-impact research, as part of the NIH Common Fund’s High-Risk, High-Reward program. The original focus of her research was on Lassa fever, a related but distinct hemorrhagic disease. When the Ebola outbreak began, she shifted her research focus to address this pressing challenge.

“Dr. Sabeti’s New Innovator Award provided flexibility to quickly adjust her research when the 2014 Ebola outbreak began,” said James M. Anderson M.D., Ph.D. director of the Division of Program Coordination, Planning and Strategic Initiatives at NIH. “This exemplifies how the High-Risk, High- Reward program allows researchers to tackle the most challenging and urgent scientific questions.”

 

Related

NIH to Launch Human Safety Study of Ebola Vaccine Candidate

 

Initial human testing of an investigational vaccine to prevent Ebola virus disease will begin next week by the National Institute of Allergy and Infectious Diseases (NIAID), part of the National Institutes of Health.

The early-stage trial will begin initial human testing of a vaccine co-developed by NIAID and GlaxoSmithKline (GSK) and will evaluate the experimental vaccine’s safety and ability to generate an immune system response in healthy adults. Testing will take place at the NIH Clinical Center in Bethesda, Maryland.

The study is the first of several Phase 1 clinical trials that will examine the investigational NIAID/GSK Ebola vaccine and an experimental Ebola vaccine developed by the Public Health Agency of Canada and licensed to NewLink Genetics Corp. The others are to launch in the fall. These trials are conducted in healthy adults who are not infected with Ebola virus to determine if the vaccine is safe and induces an adequate immune response.

In parallel, NIH has partnered with a British-based international consortium that includes the Wellcome Trust and Britain’s Medical Research Council and Department for International Development to test the NIAID/GSK vaccine candidate among healthy volunteers in the United Kingdom and in the West African countries of Gambia (after approval from the relevant authorities) and Mali.

Additionally, the U.S. Centers for Disease Control and Prevention has initiated discussions with Ministry of Health officials in Nigeria about the prospects for conducting a Phase 1 safety study of the vaccine among healthy adults in that country.

The pace of human safety testing for experimental Ebola vaccines has been expedited in response to the ongoing Ebola virus outbreak in West Africa. According to the World Health Organization (WHO), more than 1,400 suspected and confirmed deaths from Ebola infection have been reported in Guinea, Liberia, Nigeria, and Sierra Leone since the outbreak was first reported in March 2014.

“There is an urgent need for a protective Ebola vaccine, and it is important to establish that a vaccine is safe and spurs the immune system to react in a way necessary to protect against infection,” said NIAID Director Anthony S. Fauci, M.D. “The NIH is playing a key role in accelerating the development and testing of investigational Ebola vaccines.”

“Today we know the best way to prevent the spread of Ebola infection is through public health measures, including good infection control practices, isolation, contact tracing, quarantine, and provision of personal protective equipment,” added Dr. Fauci. “However, a vaccine will ultimately be an important tool in the prevention effort. The launch of Phase 1 Ebola vaccine studies is the first step in a long process.”

“Tried and true public health interventions, strong supportive medical care and the rapid testing of Ebola vaccines and antiviral treatments can help to reduce suffering now and in the future,” said CDC Director Thomas R. Frieden, M.D., M.P.H.

The investigational vaccine now entering Phase 1 trials was designed by Nancy J. Sullivan, Ph.D., chief of the Biodefense Research Section in NIAID’s Vaccine Research Center (VRC). She worked in collaboration with researchers at the VRC, the U.S. Army Medical Research Institute of Infectious Diseases, and Okairos, a Swiss-Italian biotechnology company acquired by GSK in 2013.

Phase 1 clinical trials are the first step in what is typically a multi-stage clinical trials process). During Phase 1 studies, researchers test an investigational vaccine in a small group of people to evaluate its safety and the immune response it provokes. Phase 2 clinical trials of investigational vaccines are designed to further assess safety and immune response in larger numbers of volunteers. Under certain circumstances, the vaccine’s ability to prevent infection or disease (called efficacy) can be determined in a Phase 2 trial. Phase 3 clinical trials are directed predominantly at determining efficacy.

The NIAID/GSK Ebola vaccine candidate is based on a type of chimpanzee cold virus, called chimp adenovirus type 3 (ChAd3). The adenovirus is used as a carrier, or vector, to deliver segments of genetic material derived from two Ebola virus species: Zaire Ebola and Sudan Ebola. Hence, this vaccine is referred to as a bivalent vaccine. The Zaire species of the virus is responsible for the current Ebola outbreak in West Africa.

The vaccine candidate delivers one part of Ebola’s genetic material to human cells, but the adenovirus vector does not replicate. Rather, the Ebola gene that it carries allows the cells of the vaccine recipient to express a single Ebola protein, and that protein prompts an immune response in the individual. It is important to know that the Ebola genetic material contained in the investigational vaccine cannot cause a vaccinated individual to become infected with Ebola.

“The experimental NIAID/GSK vaccine performed extremely well in protecting nonhuman primates from Ebola infection,” Dr. Fauci noted.

The candidate vaccine builds upon three earlier NIAID-developed investigational Ebola vaccines that began Phase 1 clinical trial testing in 2003.

“The knowledge gained from each of those trials has contributed to the development of the candidate vaccine we are now studying, as well as our improved understanding of human immune responses to investigational Ebola vaccines,” said John R. Mascola, M.D., director of NIAID’s Vaccine Research Center.

The Phase 1 clinical trial, called VRC 207, will be led by principal investigator Julie E. Ledgerwood, D.O., chief of the VRC’s clinical trials program, and will be conducted among 20 healthy adults ages 18 to 50 years. Participants will be divided into two groups of 10 participants each. One group will receive an intramuscular injection of the NIAID/GSK experimental vaccine. The second group will receive a single injection of the same vaccine but at a higher dose.

A number of safety features are built into the study’s design, including daily and weekly reviews of patient data by clinical staff and the study protocol team. Additionally, the trial features a staged enrollment plan that requires interim safety reviews after three participants have been vaccinated and have undergone three days of follow up before enrolling additional study participants into the group. Participants in both groups will be seen and evaluated by clinical staff nine times over a 48-week period.

Additional Phase 1 Tests of the NIAID/GSK Vaccine

As part of the VRC 207 trial, NIAID will also test a version of the NIAID/GSK vaccine that contains genetic material from only the Zaire Ebola species. Hence, this vaccine is referred to as a monovalent vaccine. This portion of the Phase 1 safety study, which will also involve 20 healthy adults, is expected to begin in October at the NIH Clinical Center and potentially another U.S. location. Dr. Ledgerwood will also lead that effort. The VRC 207 clinical trial is being conducted based on expedited review and approval by the U.S. Food and Drug Administration.

In parallel, NIH has partnered with an international consortium that includes the British-based Wellcome Trust, as well as Britain’s Medical Research Council and Department for International Development to test the same NIAID/GSK monovalent vaccine candidate. The vaccine candidate will be tested among 60 healthy volunteers at the University of Oxford in England and among 40 healthy volunteers in Mali by the University of Maryland School of Medicine Center for Vaccine Development and its Center for Vaccine Development in Mali (a joint enterprise of the University of Maryland School of Medicine and the Ministry of Health of Mali). Additionally, the vaccine candidate is expected to be tested among 40 healthy volunteers in Gambia after approval from the relevant authorities.

The Oxford trial is expected to launch in mid-September pending ethical and regulatory approval.

“Today’s announcement shows how private and public partners can pull together to quickly respond to this critical public health emergency. Developing a new vaccine is complex with no guarantees of success, and we are still in the early days for our Ebola vaccine candidate. But we are encouraged by progress so far and will do the best we can, along with WHO and our partners, to speed up development and explore ways in which the vaccine could contribute to this or future Ebola outbreaks,” said Dr. Moncef Slaoui, chairman of Global R&D and Vaccines at GSK.

Initial safety and immunogenicity data from the Phase 1 trials of the NIAID/GSK investigational Ebola vaccine are expected in late 2014.

Vesicular Stomatitis Virus (VSV) Ebola Vaccine Testing

The NIH will also collaborate with the U.S. Department of Defense in support of efforts by NewLink Genetics Corp., a biopharmaceutical company in Ames, Iowa, to conduct Phase 1 safety studies of the investigational recombinant vesicular stomatitis virus Ebola vaccine (called VSV-EBOV) developed by and licensed from the Public Health Agency of Canada. Those clinical trials are expected to begin in the fall at the Clinical Trials Center of Walter Reed Army Institute of Research in Silver Spring, Maryland.

For more information about these early-stage Ebola vaccine clinical trials, see Questions and Answers: Phase 1 Clinical Trials of NIAID/GSK Investigational Ebola Vaccine.


Single animal to human transmission event responsible for 2014 Ebola outbreak

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