MATERNAL TRANSMISSION OF IMMUNITY TO EIMERIA-MAXIMA - WESTERN-BLOT-ANALYSIS OF PROTECTIVE ANTIBODIES INDUCED BY INFECTION

Infection of breeding hens with Eimeria maxima induces production of p arasite-specific antibodies which are transferred, via the egg yolk, t o hatchling chicks. These antibodies (immunoglobulin G) are highly pro tective, mediating up to a 97% reduction in oocyst excretion in challe nged hatchlings. However, the degree of maternally derived immunity tr ansferred by the hens to their offspring declines with increasing time after infection of the hens. This decline in immunity is directly rel ated to declining immunoglobulin G titers, However, sera from highly p rotected hatchlings recognize only a very few E. maxima proteins on We stern blots (immunoblots). In particular, a 230-kDa protein band is ou tstanding for its association with maternally derived immunity to E. m axima in hatchlings. This band was excised from a sodium dodecyl sulfa te-polyacrylamide gel electrophoresis (SDS-PAGE) preparative gel of cr ude merozoite protein extract. The SDS-PAGE cutout was emulsified in F reund's adjuvant and injected, intramuscularly, into six breeding hens on two occasions, 2 weeks apart. Eggs were collected from these hens 28 to 39 days after the second injection, and the hatchlings from thes e eggs were challenged with 150 sporulated oocysts of E. maxima. Subse quent oocyst excretion in these hatchlings was, on average, 54% lower than oocyst excretion by control chicks but only 37% lower (significan t at P < 0.05) than that by chicks from hens sham immunized with Freun d's adjuvant, The latter result is apparently due to the ability of th e adjuvant to induce production of antibodies which recognize Eimeria spp. and thereby transfer some degree of protection to hatchlings. The se experiments indicate that protective, maternally derived immunoglob ulin G antibodies may be useful for the identification of putative ant icoccidial vaccine candidates.