Preparation of Antiserum to Enteroviruses in Large Animals

Summary The usefulness of five species of large domestic animals for the preparation of enterovirus immune serum was investigated systematically, using horses, cattle, sheep, goats and swine and five representative enterovirus strains, namely, poliovirus 1, coxsackievirus A9, coxsackievirus B3, and echoviruses 4 and 11. Monkey kidney tissue culture fluids of the prototype strains were treated with molar MgCl2 to preserve maximal viral infectivity and antigenicity, and concentrated tenfold by the Mg-Al carbonate method, for use as immunizing antigens. The results of serum neutralization tests showed that horses, cattle, sheep and goats produce serum of useful titer against all five viruses, and large volumes of antisera were collected. Swine responded to poliovirus 1 but not to the other four viruses. The horse appears to be the animal of choice in terms of the height of the antibody response and the closely similar titers among individual animals of each group. Booster doses, administered 21 to 28 weeks after completion of primary immunization with four doses of antigen, were effective in elevating the serum antibody titers to levels equal to or above the highest titers previously observed. Recommendations are proposed for a practical scheme to yield antiserum of high titer (10,000 range) in volumes as large as 25 L, from as few as two animals. A problem of fundamental significance was emphasized by tests performed on the echovirus 4 antisera. These sera, though high in neutralizing antibody titer against the DuToit strain of echovirus 4, were essentially negative when tested against the prototype virus (Pesascek) which had been used as the immunizing antigen. This paradoxical situation has been studied and is discussed further in a separate publication (19).