The colostrum or late milk of 71 mothers was tested against the Lansing strain of type 2 poliovirus in mice, and antipoliomyelitic activity was found in the majority of specimens only when antibody was also present in the serum. When milk specimens were obtained from mothers with type 2 poliovirus antibody in the serum, the incidence of virus neutralization was 85% of 25 tested 2 to 6 days postpartum and 62% of 39 tested 35 to 356 days postpartum. Two of three milk specimens obtained 330 to 356 days postpartum neutralized the virus.
The concentration of antipoliomyelitic substance was usually higher in the colostrum (average titer of 1:26 versus 50 LD50 of virus) than in the regular milk (average titer of 1:5). There was no correlation between the titer of antipoliomyelitic activity in the colostrum and the titer of antibody in the serum, while in the case of regular milk the mothers with higher serum antibody titers generally, but not always, yielded milks with higher concentrations of antipoliomyelitic substance.
The regular milk of 6 of 20 cows neutralized at least 100 LD50 of virus on one or more occasions, but the antepartum or early postpartum colostrum, or both, of 16 cows all neutralized the virus. In gravid cows neutralizing activity was found as early as 58 days antepartum and in some instances disappeared from the milk as soon as 2 days postpartum. Antipoliomyelitic activity was found only in the colostrum or milk of cows whose serum also neutralized the virus, but there was no correlation between the concentration in the serum and in the colostrum or milk. Type 2 poliovirus was neutralized by 80% of sera from 112 cows, aged 3 to 7 years, in Ohio, Maryland and California, by 28% of 25 California calves aged 6 to 12 months, and by only 7% of 30 Ohio calves aged 5 months. Tests on the sera of 16 Ohio cows also revealed their capacity to neutralize type 1 poliovirus and less frequently type 3 poliovirus.
The antipoliomyelitic activity of human and bovine colostrum and milk as well as of bovine serum possessed properties that could not be differentiated from those of specific antibody as regards resistance to heating at 60°C, destruction at 100°C, rapid neutralization of virus without preliminary incubation, and association of the activity with the gamma-globulin fraction. A variety of distinct antiviral factors were found in human colostrum and milk against the herpes simplex virus, the group B arthropod-borne viruses (Japanese B, St. Louis, West Nile, dengue, yellow fever) and western equine encephalitis virus without reference to the presence of antibodies for these viruses in the serum. These antiviral factors had properties different from specific antibody. Mothers possessing specific serum antibodies for the herpes simplex virus did not yield cobostrum or milk with specific neutralizing activity of the antibody variety.
Since mothers with specific antibody in their serum for the viruses of poliomyelitis and herpes simplex yielded colostrum and milk with specific neutralizing activity of the antibody variety only against poliovirus, there would appear to be special laws governing the appearance or production of antibody in the mammary gland that require further elucidation.