Trichinellosis is a cosmopolitan zoonotic disease produced mainly by the consumption of poorly cooked swine meat. Several studies have probed the efficiency of immunotherapy as a method for the treatment of trichinellosis. In this work, a 45 kDa immunodominant antigen was characterized, and the presence of IgA, IgM and IgG anti-Trichinella spiralis antibodies was evaluated during the course of the infection. In addition, the differences between sublingual and parenteral administration of the 45 kDa T. spiralis antigen were determined. Long Evans rats were used both to purify the 45 kDa antigen and to evaluate the immune response produced in six different groups: healthy and infected controls; two groups of immunized murines (sublingually and parenterally) with four doses of the 45 kDa T. spiralis immunogen administered at days 0, 7, 14 and 21 and challenged with 500 T. spiralis infective larvae (IL) 7 days after the last immunization; and finally, two groups of murines infected with 500 IL of T. spiralis, immunized at week 4 post infection by the same two routes. The humoral response was evaluated by indirect immunofluorescence by confocal microscopyin order to determine the presence of IgA, IgM and IgG antibodies.