Infections such as lower respiratory illness potentially contribute to the initiation of
asthma and are major factors in recurring acute exacerbations of the condition. Although typical bacterial respiratory pathogens such as Streptococcus pyogenes, Streptococcus pneumoniae and Hemophilus influenzae do not initiate asthmatic exacerbations, data from a subgroup of adults suggest a potential role for Mycoplasma pneumoniae and Chlamydia pneumoniae in the onset of
asthma. Common cold viruses, predominantly respiratory syncytial virus (RSV) in young children and rhinoviruses in older children and adults, are the major causes of acute exacerbations of
asthma. These exacerbations are not prevented with maintenance
therapies that are used for chronic
asthma, but do respond to short courses of systemic
corticosteroids. There are continued attempts to produce a successful
vaccine and
antiviral agents for the treatment of RSV that are more effective and more practical to use than
ribavirin, which is currently the only available
antiviral for RSV. The prevention and treatment of rhinovirus
infections have focused on the major receptor for the virus,
intercellular adhesion molecule-1 (ICAM-1), which is located on respiratory epithelial cells. A multivalent, recombinant, antibody fusion
protein identified as
CFY196 has high avidity for
ICAM-1 and has the potential to protect against rhinovirus
infection. Another approach for preventing and treating rhinovirus
infection uses a recombinant, soluble, truncated form of
ICAM-1 in which the transmembrane and intracellular domains of the
protein have been deleted. An initial clinical study on this agent demonstrated clinical efficacy in ameliorating the symptoms of experimental rhinovirus
infection in volunteers, but did not significantly prevent
infection.