Abstract
Varying titres of secretory IgA antibodies to poliovirus type 1 were found previously in the milk of unvaccinated, lactating Pakistani mothers during two different years, reflecting the antigenic exposure on mucosal membranes. To study further the changes in the extent and the form of antigenic exposure reflected in the human milk, human milk samples from Pakistani, Indian, Japanese, and Swedish mothers were collected. The quality and the neutralising capacity of the antibodies was also studied. Secretory IgA, IgG, and IgM antibodies to poliovirus type 1 were determined using enzyme linked immunosorbent assay (ELISA) and relative affinity was measured in ELISA by elution with potassium thiocyanide. Microneutralisation tests were also performed. The higher secretory IgA antibody titres to poliovirus type 1 in the unvaccinated, naturally exposed Pakistani and Indian mothers' milk, compared with the Swedish and Japanese mothers, presumably reflect the epidemiological situation in these countries. Neutralising capacity and the relative antibody affinity seemed to be higher both in the Pakistani mothers and the group without natural exposure but only given inactivated poliovirus vaccine, that is the Swedish mothers, than the group meeting only live vaccine strains, that is the Japanese mothers.
Highlights
Varying titres of secretory IgA antibodies to poliovirus type 1 were found previously in the milk of unvaccinated, lactating Pakistani mothers during two different years, reflecting the antigenic exposure on mucosal membranes
Secretory IgA, IgG, and IgM antibodies to poliovirus type 1 were determined using enzyme linked immunosorbent assay (ELISA) and relative affmity was measured in ELISA by elution with potassium thiocyanide
In our previous study we found varying levels of secretory IgA antibodies to poliovirus type 1 in the milk of lactating, unvaccinated mothers living in the poor urban slum areas of Lahore, Pakistan.' Secretory IgA antibodies in the milk of these mothers apparently reflect antigenic exposure on mucosal membranes, especially in the gut, and may follow the changes in the extent and form of antigenic exposure. 2-9
Summary
This study was performed with breast milk samples from four groups of mothers. (1) Unvaccinated Pakistani mothers who were living in an area still endemic for poliomyelitis, but presently with almost 80% infants fully vaccinated from birth onwards using OPV." 20 (2) Unvaccinated mothers from India-where poliomyelitis is still endemic and 45% of infants are presently vaccinated using OPV. 1l (3) OPV vaccinated mothers in Japan-where poliomyelitis does not exist and only OPV is used for vaccinations." (4) Swedish mothers vaccinated exclusively with inactivated poliovirus vaccine (IPV)-where poliomyelitis as well as circulation of poliovirus in the community has been prevented.2'. This study was performed with breast milk samples from four groups of mothers. (1) Unvaccinated Pakistani mothers who were living in an area still endemic for poliomyelitis, but presently with almost 80% infants fully vaccinated from birth onwards using OPV." 20 (2) Unvaccinated mothers from India-where poliomyelitis is still endemic and 45% of infants are presently vaccinated using OPV. Nine samples of colostrum from Pakistani mothers living in the poor urban slum area of Lahore were obtained (mean day of collection was three days after delivery). Eight, and 14 samples of colostrum each were obtained from the Indian, Japanese, and Swedish mothers respectively (mean day of collection was three days after delivery). Mature milk samples were collected from Pakistani, Japanese, and Swedish lactating mothers between 13 to 360 days of lactation. All milk samples were analysed at the same time period
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