Local Immunity in the Mammary Gland Following the Infusion of a Staphylococcal Cell-Toxoid Vaccine

Abstract

Summary One side of the udder of each of 16 ewes was infused with a polyvalent cell-toxoid vaccine during the dry period. The vaccine contained bacterial cells of several strains including phage type 42D,α-haetnolysin and leucocidin. A dose of 106 organisms of phage type 42D was used to challenge the immunised and non-immunised sides of the udder 3 weeks after lambing. Tiventy-four hours after challenge 5 of the ewes had developed acute mastitis and 7 a mild mastitis of the non-immunised side, but the immunised sides were palpably normal. In 4 ewes there was no evidence of inflammation on either side at this time. Clinical examination one month after challenge revealed that the non-immunised sides were indurated in most of the ewes. During the first 3 days after infection the number of bacteria cultured from milk from the immunised sides was always less than that from the non-immunised sides. Thereafter bacterial counts in milk were sometimes greater in milk from the immunised sides. However, analysis of variance of the results showed that the milk from the immunised sides contained significantly fewer staphylococci than that from the non-immunised sides during the first 14 days after infection. In the majority of the ewes the staphylococcal agglutination titre was higher in milk collected immediately before challenge from the immunised sides. It is suggested that a local immune response to cell wall antigens was largely responsible for the protection observed. Attempts to demonstrate an enhancement of the local response by the addition of 5 μg. of lipopolysaccharide to the vaccine were unsuccessful.