COMPARATIVE ANTIBODY-RESPONSES AND PROTECTION IN MICE IMMUNIZED BY ORAL OR PARENTERAL ROUTES WITH INFLUENZA-VIRUS SUBUNIT ANTIGENS IN AQUEOUS FORM OR INCORPORATED INTO ISCOMS

The total and subclass antibody responses of mice and protection of th ese animals against live influenza A/Sichuan/2/87 virus challenge infe ction were determined after immunisation with homologous A/Sichuan/87 aqueous or ISCOM-formulated surface glycoprotein subunit antigens admi nistered by either the oral or intramuscular routes. The results show that the greatest systemic and local antibody responses were elicited in mice immunised with A/Sichuan ISCOMs by the intramuscular route; pr otection against homologous virus challenge was also effective in thes e animals, particularly after two doses of the vaccine. However, relat ively high immune responses and protection were also elicited by the A /Sichuan/87 ISCOM vaccine administered orally. Immunisation of mice by the intramuscular route resulted in levels of serum IgG2a subclass an tibody significantly greater than those induced by the same preparatio n given by the oral route, or by the aqueous A/Sichuan/87 subunit anti gen preparation administered by either route. The findings indicate th at the ISCOM delivery system can be used for immunisation by the oral route, although in mice, under the conditions used, this strategy comp ares unfavourably with the intramuscular route in terms of both local and systemic immune responses and protection against homologous challe nge virus infection.