Antibody responses of chickens to inoculation with Mycoplasma gallisepticum membrane proteins in immunostimulating complexes.

Membrane proteins of Mycoplasma gallisepticum (MG) strain R were extracted with the detergent Mega-10 and incorporated into immunostimulating complexes (ISCOMs). A membrane protein of approximately 64 kD (p64) molecular weight was a major component of MG ISCOMs. Six-week-old specific-pathogen-free leghorn chickens were inoculated by various routes (subcutaneous; combined intranasal and eyedrop; and combined subcutaneous, intranasal, and eyedrop) with 10 micrograms MG proteins in ISCOMs, or inoculated subcutaneously with 10 micrograms MG proteins in Freund's adjuvant. Subcutaneous inoculation of MG ISCOMs, or MG Freund's adjuvant resulted in higher sero-positive rates (detected by enzyme-linked immunosorbent assay) in serum and respiratory tract washings, compared to combined routes of MG ISCOM inoculation. In chickens inoculated subcutaneously with MG ISCOMs antibodies were first detected at 31 days postinoculation (PI) and the sero-positive rate peaked at 56 days PI. Sero-positive rates started to decline at day 64 PI. In the Freund's adjuvant group, MG antibodies were first detected at day 21 PI, and the sero-positive rate peaked at day 39 PI and did not decline. MG antibodies were detected by ELISA in upper respiratory tract and tracheal washes from chickens inoculated subcutaneously with MG ISCOMs and MG Freund's adjuvant. Immunoblots to MG strain R whole cell proteins showed that respiratory tract washings and sera from chickens inoculated subcutaneously with MG ISCOMs contained immunoglobulins to MG proteins, with a prominent reaction to p64.