Deadly RSV may fall to improved vaccines.

Deadly RSV may fall to improved vaccines

In the alphabet soup of childhood vaccines, pediatricians hope the letters RSV will someday become as familiar as DPT. Diphtheria, pertussis and tetanus -- once major causes of illness and death among children -- have all but disappeared in the United States since development of the DPT vaccine. Not so with RSV.

RSV stands for respiratory syncytial virus, an influenza-like virus and the single most important cause of lower respiratory tract infection in infants and children. In the United States, RSV kills about 2,000 infants each year and hospitalizes an additional 55,000. Despite decades of attempts, major problems have stymied scientists' efforts to develop a vaccine against RSV, which spreads through close contact with infected children and adults and blooms in epidemic proportions each winter.

At this week's annual meeting of the American Society of Virology in London, Ontario, scientists provided some encouraging reports of RSV vaccine progress. Researchers estimate a commercially available vaccine remains three to five years away. But ongoing trials animals and small numbers of humans now suggest they have overcome the major obstacles of previous years. An experimental vaccine in the 1960s enhanced the disease in some children, leading to some deaths and a strategy change among RSV vaccine researchers. Rather than working with inactivated whole viruses, scientists today use purified, antibody-provoking RSV proteins.

After years of tests in rodents and primates, scientists from Praxis Biologics in Rochester, N.Y., say they have immunized 40 aduits and 23 toddlers 2 to 4 years old with a purified protein from the RSV outer jacket. They find high levels of protective antibodies, no disease enhancement and no notable adverse reactions, says Praxis researcher Thomas Kostyk. Pending Food and Drug Administration review of the data, Praxis hopes to begin tests in younger children.

Micael W. Wathen and his colleagues at the Upjohn Co. in Kalamazoo, Mich., report their creation of a genetically engineered vaccine made from a combination of two RSV proteins. They say tests in rates suggest their "chimeric protein" triggers a stronger immune response than does the single protein Praxis uses. Inoculation with the engineered protein protected rats from infection when they were challenged with a nasal spray of RSV. The company plans to expand to primate trials and expects to vaccinate humans within two years, says Upjohn virologist Roger J. Brideau.