PROTECTIVE IMMUNITY AGAINST ONCHOCERCA-VOLVULUS AND O-LIENALIS INFECTIVE LARVAE IN MICE

Acquired resistance to both Onchocerca volvulus and O. lienalis infect ive larvae, implanted within micropore chambers, could be induced in m ice following immunization with irradiated L3 larvae. In experiments w ith O. volvulus in BALB/c and BALB/c. By mice, consistent levels of pr otection (61-75 % reductions compared to challenge controls) were achi eved with challenge infections of 2 week duration. In DBA/2 mice, leve ls of protection against O. lienalis were lower and more variable (42- 63 %): Moreover a 3 week period between challenge and recovery was req uired before significant reductions in larval recovery became detectab le in vaccinated animals. Immunization of CBA or BALB/c mice with O. l ienalis microfilariae, or CBA mice with normal or irradiated O. lienal is L3 larvae, failed to induce killing or growth retardation of develo ping larvae. Preliminary characterization of the effector mechanisms a nd cytokines associated with protective immunity against O. volvulus i nfective larvae revealed elevated levels of eosinophils in peripheral blood and within micropore chambers during challenge infections in vac cinated mice. Spleen cells from the same animals stimulated with paras ite antigen induced significant levels of IL-5, IL-4 and IFN gamma. Th ese cytokines were barely detectable in antigen stimulated cells from challenge control mice.