Leishmania infantum-specific IgG, IgG1 and IgG2 antibody responses in healthy and ill dogs from endemic areas - Evolution in the course of infection and after treatment

The expression of IgG, IgG1 and IgG2 specific antibodies for Leishmania inf antum was studied in five groups of dogs in Catalonia (Spain): I, 99 asympt omatic dogs (infected and uninfected) from a highly endemic area for leishm aniosis; II, 139 untreated dogs with clinically patent leishmaniosis; LII, 11 naturally infected asymptomatic dogs monitored for up to 5 years since t hey were found seropositive to Leishmania antigen and without treatment; IV , 25 naturally infected dogs with clinically patent leishmaniosis and treat ed with either meglumine antimoniate and allopurinol or allopurinol alone a nd V, six experimentally infected dogs, treated with meglumine antimoniate and controlled for 5 years. The levels (ELISA units) of IgG, IgG1 and IgG2 in asymptomatic dogs (group I) were very variable (24 +/- 33, 32 +/- 31 and 26 +/- 31, respectively), and, as expected, lower than in ill dogs (group II) (168 +/- 34, 84 +/- 71 and 172 +/- 31, respectively). In both groups, t he correlation between IgG and IgG2 levels (r = 0.95, P < 0.001 in group I and r = 0.63, P < 0.001 in group II) was higher than between IgG and IgG1 l evels (I = 0.01, P > 0.05 in group I and r = 0.31, P < 0.001 in group II). In group III, IgG and IgG2 expression increased during infection, while IgG 1 expression remained the same. In dogs of group IV, IgG levels after 1 yea r of treatment decreased more in responsive (mean values, 163 +/- 42 before treatment (b.t.) and 100 +/- 36 after treatment (a.t.)) than in unresponsi ve dogs (158 +/- 29 b.t. and 124 +/- 51 a.t.), especially for IgG1 (94 +/- 89 b.t, and 20 +/- 21 a.t. in responsive dogs and 35 +/- 25 b.t. and 22 +/- 13 a.t. in unresponsive dogs) rather than for IgG2 (156 +/- 16 b.t, and 11 4 +/- 45 a.t. in responsive and 151 +/- 11 b.t. and 125 +/- 36 a.t. in unre sponsive dogs). Similar results were observed in the evolution of experimen tally infected animals after consecutive and specific treatments. Overall r esults show the great variation in Leishmania-specific IgG1 expression in a symptomatic and symptomatic dogs, their lack of correlation with that of Ig G2 and chemotherapy is more effective in dogs with initially high expressio n of IgG1. (C) 2001 Elsevier Science B.V. All rights reserved.