Efeitos do parapoxvirus ovis inativado sobre eventos da resposta imune inata em camundongos

Abstract

The immunostimulatory properties of inactivated parapoxvirus ovis (iPPVO) have been investigated in different animal species and experimental settings. This study investigated the effects of administration of iPPVO on selected events of the innate response in mice. Neutrophil activation, phagocytic activity of macrophages, serum bactericidal activity, induction and antiviral activity of interferon type I (IFN - I) and expression of several classes of cytokines were assayed following intraperitoneal inoculation of Mus musculus with iPPVO (107 TCID50). Serum from iPPVO-treated animals showed IFN-I activity against murine encephalomyocarditis virus (EMCV) between 6 and 12 hours post infection (hpi), as shown by plaque reduction. A significant activation of neutrophils at 6hpi was observed by NBT reduction test in animals treated with the iPPVO. Peritoneal macrophages from mice treated with iPPVO demonstrated a significant increase (p<0.01) in phagocytic activity against Candida albicans both in vivo (between 12 and 96 hpi) and in vitro (24 and 72 hpi). iPPVO treated mice showed increased serum bactericidal activity against Escherichia coli (p<0.05) at two periods (24 and 72 hpi). A second study evaluated the expression of cytokines in response to inoculation of iPPVO. For this, spleens and serum samples were collected from mice treated with iPPVO at different intervals after inoculation and subjected to quantification of messenger RNA (mRNA) by real time PCR (qRT-PCR) and detection/quantification of serum cytokines by ELISA. Quantification of mRNA identified a significant and transient increase in the expression of various cytokines, with variable magnitude and kinetics. mRNA expression of proinflammatory cytokines (IL-1β, TNF-α and IL-8) peaked at 24 hpi (5.4 times increase) and 48 hpi (3 and 10 times, respectively). A 15-fold increase in expression of INF-γ and 6-fold for IL-12 was observed at 48 and 24 hpi, respectively. An increase in the expression of self-regulatory cytokines (Th2) cells, especially IL-10 and IL-4 was detected at later periods (72 and 96 hpi) with peaks of 4.7 and 4.9 fold, respectively. The determination of the concentration of serum cytokines by ELISA showed an increase in IL-1β, TNF-α, IL- 12, IFN-γ and IL-10 with kinetics similar to that observed by qPCR, especially for IL-1 and INF-γ. In summary, these results demonstrate that inoculation with iPPVO stimulates transiently a number events associated with cellular and humoral innate immune responses. If taken together, these effects would likely contribute for the enhanced resistance to certain pathogens observed in animals treated with iPPVO.