A new study will expose healthy adult volunteers to respiratory syncytial virus (RSV), a virus that causes cold-like symptoms in adults. Better understanding of how adults develop RSV infection and immune system responses to infection will assist researchers in developing and testing future antivirals and vaccines to combat the virus. The research is being conducted by the National Institute of Allergy and Infectious Diseases (NIAID), part of the National Institutes of Health.
RSV is the most common cause of lower respiratory tract infections — including pneumonia and bronchiolitis mdash; among young children worldwide, according to the Centers for Disease Control and Prevention. In the United States each year, RSV leads to an average of about 55,000 hospitalizations among children younger than 5 years, with most of these hospitalizations involving infants younger than 6 months. Healthy adults infected with RSV tend to develop cold-like symptoms and recover without any problems, but the infection can cause severe disease in premature infants, children younger than two years with heart or lung problems, children and adults with weakened immune systems, and the elderly. RSV infection causes roughly 14,000 deaths annually among U.S. adults older than 65 years.
“Challenge studies such as this are a unique way of enabling scientists to monitor, in a controlled setting, the natural history of a disease in exquisite detail, using the most powerful tools of molecular biology,” says NIAID director Anthony S. Fauci, MD. “By studying RSV infection in healthy adults, we hope to improve understanding of how this infection develops and determine the suitability of this particular strain of the virus for use in future RSV vaccine and treatment trials.”
The NIAID pilot study, led by Lesia K. Dropulic, MD, of NIAID’s Laboratory of Infectious Diseases, will enroll up to 60 healthy men and non-pregnant women ages 18-50 years. Study participants will receive a drop of liquid containing RSV in each nostril and will remain hospitalized in isolation at the NIH Clinical Center in Bethesda, Maryland, for approximately one to two weeks. This is being done both to allow for monitoring of the study volunteers and because RSV is highly contagious.
While at the Clinical Center, medical staff will monitor study participants daily for signs and symptoms of RSV infection and conduct blood draws and sample nasal secretions to intensively study the development of infection. Participants will also have tests to measure how much air they can move in and out of their lungs.
Investigators will use a laboratory-developed strain of RSV commonly used in research called RSV A2. The strain is the first molecularly cloned challenge virus, meaning the RSV A2 study virus originates from a single clone of the virus strain and has been tested to ensure it is not contaminated with other infection-causing pathogens. Once infected with RSV A2, study participants are likely to develop cold-like symptoms, including a runny nose, cough, ear pain, fever, headache, sinus congestion and sore throat. However, because virtually all adults have been infected with RSV during childhood, some study participants may remain completely well. Any volunteers who do become unexpectedly, seriously ill would be medically treated at the Clinical Center and provided with the standard of care.
“We do not anticipate that the healthy, carefully screened adult volunteers in this study will become severely sick from the RSV challenge virus because, in general, healthy adults are repeatedly exposed to RSV in their lives and either remain asymptomatic or develop a mild to moderate cold,” says Dropulic.
The first three participants enrolled in the study will receive a low dose of RSV A2 and will remain isolated for monitoring at the Clinical Center for at least one week. If no major safety concerns or complications arise, investigators will enroll additional participants who will be randomly assigned to receive either the same low dose of RSV A2 or a higher dose. Investigators are testing two different doses because some adults may need more of the virus to develop cold-like symptoms. Neither the study staff nor the participants will know which participants receive the higher dose.
NIAID investigators, in collaboration with the Johns Hopkins University School of Public Health, Baltimore, will analyze participant samples to measure levels of virus shedding and immune protection. Participants will be discharged from the Clinical Center once they have two consecutive negative tests for RSV and no symptoms of RSV-associated respiratory tract illness. All participants are expected to return to the Clinical Center for two follow-up visits 28 days and 56 days after they were infected. Participants who develop RSV disease will return for a third visit at 180 days (if it does not occur during RSV season), so that investigators can assess the durability of immune responses to RSV. Investigators expect to release results of the trial in 2017.
The Food and Drug Administration approved the testing of RSV A2 in healthy people, and an independent data and safety monitoring board composed of clinical research experts will closely monitor participant safety throughout the trial.