First clinical study of new pediatric croup vaccine shows safety, tolerability in adults

08/23/04

Scientists at St. Jude Children's Research Hospital are investigating in adults the use of a vaccine given by nose drops that might ultimately protect children against human parainfluenza virus-type 1 (hPIV-1). This virus is the most common cause of croup, a pediatric respiratory disease that causes almost 30,000 hospitalizations each year and many more emergency room visits.

These findings are published in the current issue of Vaccine.

Successful development of an effective hPIV-1 vaccine would be significant because none is currently available and a vaccine that is given to infants using nose drops would eliminate the discomfort and complications of injections.

Because the vaccine contains a live virus, it should stimulate both antibody and cellular immune responses, which together may provide durable protection from hPIV-1. In cellular immunity, special cells, rather than antibodies, destroy virus-infected cells inside the body.

The vaccine consists of Sendai virus (SeV), a mouse virus that is similar enough to hPIV-1 to act as a vaccine, but different enough to have never been associated with a human disease, according to Karen Slobod, M.D., associate member of the department of Infectious Diseases.

Slobod is the lead author of the Vaccine report.

Pre-clinical studies by the St. Jude team proved that intranasal SeV vaccine can protect against the human croup virus. The results of the study in nine healthy adults demonstrated that the SeV vaccine was safe and well tolerated. None of those vaccinated experienced any significant reactions, such as respiratory symptoms or laboratory abnormalities.

This FDA-approved Phase I trial was initiated in adults as a first step, prior to future testing in children and then infants--the ultimate target population, said Jerry Shenep, M.D., member of the department of Infectious Diseases and a co-author of the paper.

"The St. Jude team based the vaccine on SeV for two reasons," said Allen Portner, Ph.D., member of the department of Infectious Diseases and a co-author of the paper. "First, it appears likely that this virus will provide immunity against hPIV-1 in infants. Second, despite the fact that children frequently have close contact with mice carrying SeV, there has never been a confirmed case of SeV infection in humans." Using a natural mimic of a human virus follows in the tradition of the world's most successful vaccine, the smallpox vaccine, said Julia Hurwitz, Ph.D. member of the department of Immunology.

"The smallpox vaccine was based on the cowpox virus, which caused only limited skin infection in healthy humans," Hurwitz said. "Yet it provided lifelong protection against smallpox and eradicated this disease from the human population in the 1970s. We hope that SeV will similarly help eradicate hPIV-1 as a cause of childhood croup."

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