Specific humoral and cellular immunity induced by Trypanosoma cruzi DNA immunization in a canine model

Abstract

Chagas disease has a high incidence in Mexico and other Latin American countries. Because one of the most important known methods of prevention is vector control, which has been effective only in certain areas of South America, the development of a vaccine to protect people at risk has been proposed. In this study, we assessed the cellular and humoral immune response generated following immunization with pBCSP and pBCSSP4 plasmids containing the genes encoding a trans-sialidase protein (present in all three forms of T. cruzi) and an amastigote specific glycoprotein, respectively, in a canine model. Thirty-five beagle dogs were divided randomly into 5 groups (n = 7) and were immunized twice intramuscularly with 500 μg of pBCSSP4, pBCSP, pBk-CMV (empty plasmid) or saline solution. Fifteen days after the last immunization the 4 groups were infected intraperitoneally with 500 000 metacyclic trypomastigotes. The fifth group was unimmunized/infected. The parasitaemia in the immunized/infected dogs was for a shorter period (14 vs. 29 days) and the parasite load was lower. The concentration of IgG1 (0.612 ± 0.019 O.D.) and IgG2 (1.167 ± 0.097 O.D.) subclasses was measured (absorbance) 15 days after the last immunization with both recombinant plasmids, the majority of which were IgG2. The treatment of parasites using the serum from dogs immunized with pBCSP and pBCSSP4 plasmids produced 54% (± 11.8) and 68% (± 21.4) complement-mediated lysis, respectively. At 12 h post immunization, an increase in cytokines was not observed; however, vaccination with pBCSSP4 significantly increased the levels of IFN-γ and IL-10 at 9 months post-infection. The recombinant plasmid immunization stimulated the spleen cell proliferation showing a positive stimulatory index above 2.0. In conclusion, immunization using both genes effectively induces a humoral and cellular immune response.

Effect of the Plasmid-DNA Vaccination on Macroscopic and Microscopic Damage Caused by the Experimental ChronicTrypanosoma cruziInfection in the Canine Model

“…Our experimental canine model of CD has already been standardized in accordance with lethal doses 50 assays to determine an adequate inoculum and achieving the establishment of the acute and chronic phases of CD through the systemic infection (one of the natural routes of infection in dogs, besides of the oral route by ingesting the vector). Our observations confirmed that DNA-immunization did not abrogate the parasitemia found in all experimental groups during the acute phase of CD; however, the antibodies produced by DNA-immunized dogs mediated the lysis of parasites through the complement system, which had an impact during the acute phase of the illness because parasitemia and parasite load was lower over time in the animals of the vaccinated groups than those nonimmunized dogs [35].…”

“…Experimental studies indicate that different T. cruzi laboratory strains exhibit varying degrees of tissue tropism, and the pattern of inflammation in tissues and organs allowed the classification of T. cruzi strains into six discrete typing units (DTUs) according to their genetic background and biodomes. In Mexico, the most of the T. cruzi strains that have been genetically analyzed to date belong to the T. cruzi I group, such as T. cruzi Ninoa strain (MHOM/1994/MX/Ninoa (T. cruzi I)), a reference Mexican strain used in many kinds of studies, which has been classified as a low-virulence strain belonging to biodeme 3 and T. cruzi I group in accordance with these criteria [28,33,34]; it can behave pathogenically in the human host, as described in the murine model and now in the canine model [24,25,35].…”

Echocardiographic Findings in Canine Model of Chagas Disease Immunized with DNA Trypanosoma cruzi Genes

“…The rest of the positive control dogs (n = 6) were infected with an inoculum size that ranged from 50 × 10 3 to 2 × 10 6 metacyclic trypomastigotes. The amount of T. cruzi Ninoa strain inoculum had no effect on the severity of the canine ChD [34][35][36]38].…”

“…The aim of this study was to examine the usefulness of echocardiography in determining the prophylactic effect of the DNA vaccines on heart damage using T. cruzi genes cloned into an expression vector, which was intramuscularly injected to beagle dogs. To do so, we use this cardiac imaging method to measure hemodynamic parameters to determine whether echocardiography provides accurate data on the development of morphological changes in the heart of experimentally infected and immunized/infected chagasic dogs and if these data are consistent with those reported previously [34][35][36].…”

“…Immunological protection against experimental infection with T. cruzi has been studied since the second decade of the last century, testing many types of immunogens [31]. In our previous studies, TcSP (encoding trans-sialidase protein) and TcSSP4 (encoding amastigote-specific protein) genes were evaluated prophylactically as DNA vaccines in both murine and canine model of ChD [32][33][34][35][36]. The clinical, serological, and postmortem parameters obtained were consistent among these studies, showing a moderate effectiveness in protection against experimental ChD.…”