RESUMEN
Mucosal sites have an innate defense system--which includes immune cells, antibodies, and mucus--to protect the body from opportunistic pathogens. Some sexually transmitted diseases (STDs), such as HIV, utilize host defense mechanisms to evade detection by infecting motile immune cells present at the site. The infected cells migrate through the mucus layer and penetrate the epithelium undetected. A new strategy for preventing STDs could involve inhibiting cell migration through the mucus. One method for inhibiting migration is to alter the barrier property of mucus by modifying its gel structure. Mucin, the structural component of mucus, is a high molecular weight anionic molecule, which forms an entangled fiber network through non-covalent interactions. The addition of nonionic or cationic polymers, such as poly(ethylene glycol) (PEG) or poly(vinyl pyridine) (PVP), altered the overall gel structure as revealed by scanning electron microscopy (SEM), while anionic poly(acrylic acid) had little effect on the structure. Acid residues on mucin associate with PEG through hydrogen bonds to form regions of coalesced fibers within the mucus. PVP, however, interacts with mucin via electrostatic bonds, forming a gel that had areas of aggregated fibers adjacent to regions with virtually no fibers. These results suggest that addition of small amounts of certain synthetic polymers will modify mucus structure; these changes should alter the barrier properties of mucus.