Evaluación de la protección inducida por una vacuna de DNA contra la infección por Trichinella spiralis en modelo de ratón

Abstract

Trichinellosis is a parasitic zoonosis caused by the genus Trichinella, which is widely distributed in the world. Chemotherapy is fundamental in the control of this disease; nevertheless, there exist reports of therapeutic failure. Therefore, a veterinary vaccine could be an option to control the disease. A 30-mer synthetic peptide (Ag30) derived from a 43-kDa glycoprotein (gp43) induced significant protection against enteric T. spiralis infection in mice when it was administered by intranasal route (36%). More recently, Salmonella enterica serovar Typhimurium carrying Ag30 induced a protective immune response against the T. spiralis challenge at the enteral phase (61.83%). It is of interest to increase the protection conferred by Ag30, thus, the use of a DNA vaccine was considered. The main objective of this study was to evaluate the protection induced by a DNA vaccine encoding Ag30 against the enteral phase of T. spiralis. The expression vector pVAX1 was used to construct the DNA vaccine; it included the gp43 peptide signal sequence (PS), followed by the Ag30 sequence and a molecular FLAG. The oligonucleotides used for the PCR amplification of PS and Ag30 were designed according to T. spiralis gp43 sequence (GenBank accession number M95499). FLAG sequence was amplified from a previous coupling reaction. The amplified products PS, Ag30 and FLAG were ligated and cloned into pRLnull vector and the sequence PS-Ag30-FLAG was further cloned into pVAX1 expression vector (pVAX-Ag30). PS-Ag30-FLAG was sequenced, demonstrating its adequate orientation. In order to evaluate the protection induced by pVAX-Ag30, groups of seven male BALB/c mice were twice immunized with 100 μg of pVAX-Ag30 and pVAX1 at two week-intervals. An infection control group was included. Two weeks after the last immunization animals were challenged with 300 T. spiralis ML and eight days after infection, T. spiralis adults were recovered from the intestine. pVAX-Ag30 did not confer protection against the intestinal phase of T. spiralis, however, it does not rule out the possible induction of protection at the systemic level. Further studies are necessary to be carried out in order to define the protection induced by pVAX-Ag30, as well as other considerations to enhance the immune response like changing the immunization schedule, the administration routes and the use of immunostimulatory molecules