EFFECT OF CARRAGEENAN ON THE RESISTANCE OF CONGENITALLY ATHYMIC NUDE AND NORMAL BALB C MICE TO INFECTIVE LARVAE OF BRUGIA-MALAYI/

Resistance of BALB/c mice to infective third-stage larvae (L3) of the human filarial parasite Brugia malayi is thymus-dependent, although th e actual effector mechanisms that mediate larval killing are unknown. The present study examined the effect of carrageenan (CGN) on the mech anisms of resistance to B. malayi infection in heterozygous (nu/+) and nude (nu/nu) mice. Mice were treated with CGN at a single dose of 20 or 200 mg/kg and were inoculated intraperitoneally 1 day later with 10 0 L3. The results showed a dose-dependent increase in the numbers of L 4 and L5 that were recovered from nu/+ and nu/nu mice. CGN treatment a lso enhanced the recovery of mature adult worms from nu/nu mice and ap peared to abolish partially the dichotomy of resistance between the us ually more susceptible male and the more resistant female nu/nu mouse. Microfilariae were found in the peripheral blood and the peritoneal c avity of CGN-treated male and female nu/nu mice and in the peritoneal cavity of male but not female nu/+ mice. Fewer larval granulomas were recovered from the peritoneal cavity of treated mice. CGN-treated, par asitized nu/+ and nu/nu mice showed high titers of IgM and IgG antibod ies. An experimental compound, CGP 20376, showed 100% larvicidal activ ity following the administration of a single dose of 20 mg/kg to CGN-t reated mice. From this study, we conclude that macrophages alone or in conjunction with other cells are actively involved in the resistance of mice to B. malayi L3.