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. 2017 Nov 25;17(1):732.
doi: 10.1186/s12879-017-2834-6.

Effects of IFN-γ coding plasmid supplementation in the immune response and protection elicited by Trypanosoma cruzi attenuated parasites

Cecilia Pérez Brandán  1 , Andrea C Mesías  2 , Cecilia Parodi  2 , Rubén O Cimino  3 , Carolina Pérez Brandán  4 , Patricio Diosque  2 , Miguel Ángel Basombrío  2
Affiliations

Effects of IFN-γ coding plasmid supplementation in the immune response and protection elicited by Trypanosoma cruzi attenuated parasites

Cecilia Pérez Brandán et al. BMC Infect Dis. .

Abstract

Background: Previous studies showed that a naturally attenuated strain from Trypanosoma cruzi triggers an immune response mainly related to a Th2-type profile. Albeit this, a strong protection against virulent challenge was obtained after priming mice with this attenuated strain. However, this protection is not enough to completely clear parasites from the host. In T. cruzi infection, early Interferon-gamma (IFN-γ) is critical to lead type 1 responses able to control intracellular parasites. Therefore we evaluated whether the co-administration of a plasmid encoding murine IFN-γ could modify the immune response induced by infection with attenuated parasites and improve protection against further infections.

Methods: C57BL/6J mice were infected intraperitoneally with three doses of live attenuated parasites in combination with plasmid pVXVR-mIFN-γ. Before each infection dose, sera samples were collected for parasite specific antibodies determination and cytokine quantification. To evaluate the recall response to T. cruzi, mice were challenged with virulent parasites 30 days after the last dose and parasite load in peripheral blood and heart was evaluated.

Results: As determined by ELISA, significantly increase in T. cruzi specific antibodies response was detected in the group in which pVXVR-mIFN-γ was incorporated, with a higher predominance of IgG2a subtype in comparison to the group of mice only inoculated with attenuated parasites. At our limit of detection, serum levels of IFN-γ were not detected, however a slight decrease in IL-10 concentrations was observed in groups in which pVXVR-mIFN-γ was supplemented. To analyze if the administration of pVXVR-mIFN-γ has any beneficial effect in protection against subsequent infections, all experimental groups were submitted to a lethal challenge with virulent bloodstream trypomastigotes. Similar levels of challenge parasites were detected in peripheral blood and heart of mice primed with attenuated parasites alone or combined with plasmid DNA. Expansion of IgG antibodies was not significant in TCC+ pVXVR-mIFN-γ; however, the overall tendency to sustain a Th2 profile was maintained.

Conclusions: Overall, these results suggest that administration of plasmid pVXVR-mIFN-γ could have beneficial effects on host specific antibody production in response to T. cruzi attenuated infection; however, this outcome is not reflected in an improved protection against further virulent infections.

Keywords: Attenuated infection; IFN-γ; Trypanosoma cruzi.

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Conflict of interest statement

Ethics approval

All animal protocols adhered to the National Institutes of Health (NIH) “Guide for the care and use of laboratory animals” and were approved by the School of Health Sciences and by the Ethical Committee of the National University of Salta, Argentina (N° 014–2011).

Consent for publication

Not applicable.

Competing interests

The authors declare that they have no competing interests.

Publisher’s Note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Figures

Fig. 1
Fig. 1
pVXVR-mIFN-γ administration alters the parasite-specific immune response elicited by infection with attenuated parasites. Mice (n = 4) were infected (4 weeks apart) with 3 doses of 105 metacyclic trypomatigotes of the attenuated TCC strain, 50 μg of plasmid pVXVR-mIFN-γ or a combination of both. After each infection dose, serum samples were collected for IgG and cytokines determination. a T. cruzi specific total IgGs levels; b serum levels of parasite specific IgG subtypes, c IL-10 measurement determined by ELISA and (d) IL-10 and IFN-γ levels in supernatant from T. cruzi stimulated spleen cells. Data are representative of three independent experiments. * p < 0.05 Kruskal-Wallis test for single-day measurements with Dunn’s Multiple Comparison Test
Fig. 2
Fig. 2
Control of parasite replication in animals primed with TCC+ pVXVR-mIFN-γ after lethal challenge. Thirty days after the last dose with attenuated parasites and plasmid DNA, animals were challenged with 500 blood trypomastigotes from the Tulahuen strain (n = 4). a Survival rate during the challenge period; b parasite load in peripheral blood as determined by fresh blood mount and (c) parasite load in heart as determined by Real Time PCR 30 days post challenge. Data are representative of three independent experiments. * p < 0.05 and ** p < 0.01 Kruskal-Wallis test for single-day measurements with Dunn’s Multiple Comparison Test
Fig. 3
Fig. 3
Expansion of immune specific antibodies in response to T. cruzi infection. Thirty days after challenge serum samples from animals primed with TCC, TCC+ pVXVR-IFN-γ, pVXVR-IFN-γ and PBS were collected for (a) parasite specific IgG antibodies and (b) IgG subtypes by ELISA. Data are representative of three independent experiments. * p < 0.05 Kruskal-Wallis test for single-day measurements with Dunn’s Multiple Comparison Test
Fig. 4
Fig. 4
Cytokines levels in response to virulent T. cruzi infection. Cytokine concentration in serum of TCC and TCC+ pVXVR-IFN-γ primed animals challenged with virulent parasites. Samples were collected 30 days post challenge and cytokines level measured by ELISA for (a) IFN-γ, (b) IL-10 and (c) TNF-α. Data are representative of three independent experiments. * p < 0.05 Kruskal-Wallis test for single-day measurements with Dunn’s Multiple Comparison Test
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