O presente trabalho foi realizado em duas etapas experimentais. O objetivo do Experimento 1 foi avaliar o perfil de produção de anticorpos anti-eCG em novilhas Bos taurus e Bos indicus tratadas uma, duas ou três vezes, com 400 e com 2000UI de eCG. O experimento foi realizado em duas réplicas com o mesmo desenho experimental, porém com padrões raciais distintos. Os animais foram divididos em 6 grupos: os grupos eCG2000UI_1x (n = 5), eCG2000UI_2x (n = 5) e eCG2000UI_3x (n = 5) receberam, respectivamente, um, dois e três tratamentos com 2000 UI de eCG, enquanto os grupos eCG400UI_1x (n = 5), eCG400UI_2x (n = 5) e eCG400UI_3x (n = 5) receberam os mesmos tratamentos porém com 400 UI de eCG. Foram realizadas coletas de sangue semanais por um período de 63 dias, em seguida o intervalo entre as coletas foi de 30 e 60 dias totalizando um período de 300 dias. A dosagem dos anticorpos anti-eCG foi realizada por teste ELISA. O número de tratamentos não influenciou a produção de anticorpos anti-eCG; a produção de anticorpos foi maior em fêmeas Bos taurus que em Bos indicus, e a aplicação de 2000 UI de eCG resultou em maiores concentrações de anticorpos que a aplicação de 400 UI nos primeiros 21 dias após o tratamento e na resposta tardia. O objetivo do Experimento 2 foi avaliar a memória imunológica celular e humoral de fêmeas Bos taurus previamente tratadas com 400 e 2000 UI de eCG, e verificar a influência dessa possível memória imunológica na atividade biológica da molécula de eCG. Além dos animais utilizados no experimento anterior, no Experimento 2 foram incluídos outros nove animais sem tratamento prévio com eCG: eCG2000UI_Controle (n = 5) e eCG400UI_Controle (n = 4). No D0 os animais receberam 2 mg de benzoato de estradiol e um dispositivo intravaginal de progesterona (DIB). Quatro dias mais tarde, as fêmeas dos grupos eCG2000UI_1x, eCG2000UI_2x, eCG2000UI_3x e eCG2000UI_Controle receberam 2000 UI de eCG, enquanto as fêmeas dos grupos eCG400UI_1x, eCG400UI_2x, eCG400UI_3x e eCG400UI_Controle receberam 400 UI de eCG. No momento da retirada do DIB (D8) os animais receberam PGF₂ e 1 mg de cipionato de estradiol. Foram realizadas coletas de sangue semanais por 32 dias para dosagem de anticorpos, e duas coletas para avaliação da atividade celular proliferativa no D0 e D32. No momento da retirada do DIB as novilhas foram submetidas a exame ultrassonográfico para avaliação da resposta superestimulatória (no. de folículos > 6 mm) e para mensuração do diâmetro do maior folículo nas fêmeas tratadas com 2000 e 400 UI de eCG, respectivamente. O tratamento prévio não gerou memória imunológica humoral, independente da dose e do número de tratamentos realizados. No entanto, foi observada memória imunológica celular, sendo que esta memória foi maior nos animais submetidos a maior número de tratamentos prévios. Foi observada tendência de efeito de réplica na resposta superestimulatória, e correlação negativa entre a concentração de anticorpos e o número de folículos > 6 mm. O tratamento com 400 UI de eCG não mostrou os mesmos efeitos no diâmetro folicular.

The present study was carried out in two experimental steps. Experiment 1 was designed to evaluate the anti-eCG antibodies production in Bos taurus and Bos indicus heifers, in response to 400 and 2000UI of eCG, employed once, twice or three times. This experiment was performed in two identical experimental designs, however, using distinct genetic groups. Animals where randomly divided in six groups: eCG2000UI_1x (n = 5), eCG2000UI_2x (n = 5) and eCG2000UI_3x (n = 5) were respectively treated with one, two and three injections of 2000 UI of eCG. Groups eCG400UI_1x (n = 5), eCG400UI_2x (n = 5) and eCG400UI_3x (n = 5) were submitted to the same treatment protocol aforementioned; however, eCG dose was 400UI. Animals where then submitted to weekly blood sampling during a 63 days period, and then samples were collected within intervals ranging from 30-60 days, totalizing a period of 300 days. Anti-eCG dosage assay was performed by ELISA. Antibody production was not affected by the number of doses; however, was higher in Bos taurus females. Moreover, higher antibodies levels in the first 21 days after treatment and in the late response were observed when 2000 UI of eCG was applied. The Experiment 2 was focused on the evaluation of cellular and humoral immunological memory of Bos Taurus females previously treated with 400 and 2000 UI of eCG, as well as to figure out influence of the possible immunological response on biological activity of eCG molecule. Besides the animals that were used in the first experiment, nine additional heifers were included in the second trial, which were eCG2000UI_Control (n = 5) and eCG400UI_Control (n = 4). The treatment protocol was: on Day 0 (D0) all heifers received 2 mg of estradiol benzoate and one intravaginal progesterone device (DIB). Four days later, groups eCG2000UI_1x, eCG2000UI_2x, eCG2000UI_3x and eCG2000UI_Control received an injection of 2000 UI eCG, while groups eCG400UI_1x, eCG400UI_2x, eCG400UI_3x and eCG400UI_Control received 400 UI. By the time of DIB withdrawal (D8), animals were treated with PGF₂ plus 1 mg of estradiol cipionate treatment. Afterwards, weekly blood samples were collected during 32 days for antibodies assay. Two additional blood samples were performed on day D0 and D32 to evaluate the cellular proliferative activity in response to eCG. In order to evaluate the ovarian stimulatory response (number of follicles > 6mm) in heifers treated with 2000 UI of eCG as well as the size of the largest follicle in those heifers treated with 400UI, ultrasound examination was carried by the time of DIB withdrawal. Humoral immunological memory response was not observed in animals previously treated with 400 or 2000 UI of eCG, regardless the number of treatments. Otherwise, cellular immunological memory response was observed and was higher in animals subjected to an increased number of treatments. A tendency of replicate effect in follicle numbers (> 6mm) was observed, as well as a high negative correlation between antibodies concentration and the number of follicles > 6mm. Same results were not observed when 400 UI of eCG treatment was performed.