Discuss the progress towards vaccines to prevent common cold
Important note:common cold not a single disease but a conventional term for a host of dieases characterized (whats significance for vaccine development?? (from here-on the acronym will be refered to as 'dvt')) by a mild upper respiratory illness. Symptoms include nasal stuffiness, discharge (rhinorrhea), sneezing and sore throat.
Caused by numerous viruses that belong to several families (also significance to efforts to develop vaccine??), e.gs are adenovirus, parainfluenza virus, rhinovirus, respiratory synctial virus (RSV), enterovirus and coronavirus.
Some 20 to 30 percent of colds without proven viral cause (prob cant develop vaccine against unknown causative agent???)
some causative agents might still be undisvovered. Recent discovery of new causative agent , human metapneumonic virus as cause of common cold.
About 5 peercent of common cold infections characterised by more than two or more causative agents
Why develop vaccine???
common cold most common infection in humans.
Main cause of consultations with primary health care providers in the developed world (absenteeism at work etc, all take financial toll)
vaccine thought to be potentially the most effective way of controlling common cold.
Vaccine progress
One of the pertinet questions has always been whether its possible to develop a single or combined effective vaccine to combat all or most of the numerous agents against the cold.
Enormous number of organisms a big problem when it comes to vaccine development.
Possible alternative: dvt of vaccine against the more common viral causative agents ,eg during autumn up to 80 percent of infections due to rhinovirus (at least in the united states anyway).
One possible :vaccine derived from killed or split virus.works for influenza. Not an avenue explored much coz of incident with RSV vaccine trials.
RSV (respiratory synctial virus): once a potential candidate for vaccine dvt. In 1960's formalin inactivated RSV vaccine was associated with increased morbidity and mortality. When vaccine recipients were naturally exposed to RSV virus, 80 percent of RSV vaccines were hospitalized, compared to 5 percent of the control. Two fatalities resulted.
Rhinovirus: most common causative viral agent in all age groups,accounts for most of all resp illnesses. Good candidate for vaccine dvt.
Problems: more than 100 serotypes of rhinovirus have been identified as causing the common cold.
All the different serotypes induce neutralizing antibodies in their own specific way.
Absence of a suitable common antigen across the spectrum of rhinoviruses.
Current avenues of research
vaccine effect through mediated T-cell response.T cell response might be preserved through different viral strains.
Generation of T cell response normally requires endogenous expression of antigen.
Plasmid DNA encoding nucleocapsid protein of influenza known to evoke T cell response after injection into muscle. Protects not only from injected strain but other strains as well. Same appraoch used for common cold???
for parainfluenza virus: evaluation of recombinant bovine (PIV3) and human PIV3 attenuated vaccines in animal models.
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