How does zinc modify the common cold? Clinical observations and implications regarding mechanisms of action.

Clinical studies have shown that ionic zinc (Zn2+) dissolved in the mouth shortened manifestations of the common cold significantly, by an unknown mechanism. The observed immediate effect on symptoms is consonant with osmotic transport of Zn2+, placing a temporary chemical clamp on critical nerves. It is proposed that transient elevation of Zn2+ concentration in and around the nasal cavity facilitates Zn2+ complexation with known intercellular adhesion molecule binding sites on rhinovirus surfaces which prevents rhinovirus binding to cells and interrupts infection. The crystallographically determined surface of rhinovirus-14 has been found to contain binding sites for at least 360 Zn2+. Such binding of Zn2+ would be stabilized by numerous histidine, methionine, tyrosine and carboxyl/carboxylate groups known to line the HRV-14 surface canyons. The resulting blockage of HRV docking with intercellular adhesion molecule binding sites is proposed to be responsible for the observed reduction of the duration of colds by statistically significant and clinically meaningful times.