Influence of whole human milk, and fractions thereof, on inclusion-formation of Chlamydia trachomatis in McCoy cells.

A study of the effect of human breast milk, and components thereof, on the capacity of Chlamydia trachomatis to form inclusions in cycloheximide-treated McCoy cells, was undertaken. Pooled whole milk collected during the first week of breast feeding caused a concentration-dependent inhibition of the chlamydial inclusion-formation. The activity resided in the fat and fat globule membrane (FGM) components of the milk. The active principle in the FGM fraction is heat-stable and pronase-sensitive, but resistant to both neuraminidase and periodate. Immunoglobulins was not responsible for the inhibition. Whey and casein fractions of milk increased the chlamydial inclusion-formation. The activity of the whey was heat-stable, dose-related, and had a mol. wt. of greater than or equal to 12,000. The casein fraction was still active after heat treatment. Whey samples collected up to 28 days after delivery varied slightly in their stimulatory activity, with an optimum between the 7th and 14th days. The present study demonstrated a multieffect of breast milk on chlamydial inclusion-formation: an inhibitory activity due to a protein compound as well as another factor in the fat fraction and an enhancing effect due to a heat-stable factor(s).