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Few molecules are active against respiratory viruses. In upper respiratory tract infections, which are frequent and fortunately not severe, their deficiency is not a problem. However some molecules are able to block in vitro the interaction between a rhinovirus and its receptor: anti-receptor antibodies, soluble ICAM-1, capsid-binding agents. The lower respiratory tract infections (bronchiolitis, pneumonia...), mainly due to respiratory syncytial virus and influenza viruses are potentially more severe, and 2 groups of compounds are or have been used in these infections: amantadine and ribavirin. Ribavirin is effective in respiratory infections due to respiratory syncytial, influenza and parainfluenza viruses, and on many other viruses. Its toxicity needs to administrate it as an aerosol, and in France, ribavirin is used as compassional treatment in severe forms of bronchiolitis or pneumonia due to respiratory syncytial virus, and in high-risk children. Anti-parkinsonian drugs, related to amantadine (Mantadix, Roflual) are no longer on sale. Therefore there is no active molecule yet available against these viruses.

Rhinoviruses are the main etiologic agents of infectious common colds, which represent about 40% of the acute respiratory infections in man. The antigenic diversity of rhinoviruses precludes any prevention by vaccination. Within the last 20 years, efforts have therefore concentrated on chemoprophylaxis or chemotherapy with antiviral agents. Interferons (alpha and beta) administered intranasally at high doses, exerted a significant prophylactic activity in volunteers inoculated with rhinoviruses or in the course of epidemics in families. By contrast, the therapeutic activity of interferons is almost nonexistent, which greatly limits their practical interest. Various synthetic chemicals exert a marked and selective inhibitory effect on the replication of various serotypes of rhinoviruses in cell cultures. In the absence of an animal model of rhinovirus infection, in vivo studies of these molecules have been performed in human volunteers, chiefly at the Common Cold Research Unit in Salisbury (Great Britain). 3 synthetic compounds (an imidazothiazole, a benzimidazole derivative and a piperazinyl-pyridazine) have exerted a significant prophylactic activity, especially marked with the latter. None of these compounds, however, was active when administered after the infectious challenge. The search for selective anti-rhinovirus compounds is still going on; it will probably be facilitated through a combination of structural studies of rhinovirus capsids (or of their cellular receptors) with computer-assisted design of synthetic molecules. The recent observation of the influence of psychological factors on the propensity of rhinovirus-infected subjects to develop clinically apparent common cold must be taken into account in future studies.