Effects of inactivated parapoxvirus ovis on cellular and humoral events of the innate immune response in mice D. Anziliero a,⇑ , L.C. Kreutz b , E.F. Flores a , R. Weiblen a a Programa de Pós-Graduação em Medicina Veterinária, Departamento de Medicina Veterinária Preventiva, Universidade Federal de Santa Maria, Santa Maria, Rio Grande do Sul, Brazil b Programa de Pós-graduação em Bioexperimentação, Universidade de Passo Fundo, Campus I, Bairro São José, BR 282, km 171, 99052-900 Passo Fundo, RS, Brazil article info Article history: Received 4 October 2013 Accepted 14 March 2014 Available online 29 March 2014 Keywords: Contagious ecthyma virus Orf virus Immunostimulant Innate immunity abstract The immunostimulating properties of inactivated parapoxvirus ovis (iPPVO) have long been demonstrated in vivo and in vitro, yet the biological and molecular mechanisms involved remain largely unknown. We herein report that intraperitoneal inoculation of iPPVO in mice results in stimulation of several events of the innate immune response. Increased interferon I (IFN-I) activity was demonstrated in sera of mice treated with iPPVO at 6 and 12 h post-inoculation (hpi), and enhanced expression of IFN-c (15-fold increase) and IL-12 (6-fold) mRNA was detected in the spleen of treated mice at 24 and 48 hpi, respectively. A significant increase in neutrophil activity (p < 0.01) was observed at 6 hpi in the blood of iPPVO treated mice. In addition, increased phagocytic activity by peritoneal macrophages of iPPVO-treated mice (p < 0.01) was detected in vivo (from 24 to 72 hpi) and in vitro (12 to 96 hpi). Bactericidal activity of sera mice treated with iPPVO against Escherichia coli was also increased (p < 0.05) at 24 and 72 hpi. Taken together, these results demonstrate that iPPVO administration leads to a transient stimulation of selected innate immune mechanisms, likely contributing to the immunostimulant effects observed against viral and bacterial infections in vivo. Ó 2014 Elsevier Inc. All rights reserved. 1. Introduction Parapoxvirus ovis (PPVO) or orf virus (OV or OrfV) is a member of the genus Parapoxvirus (PPV), family Poxviridae [1]. PPVO infection in sheep and goats – its natural hosts – results in a mucocutaneous, debilitating disease known as contagious ecthyma or contagious pustular dermatitis. The disease is characterized by inflammatory, proliferative and scabby lesions in the mucocutaneous junction of the lips, labial commissure, muzzle and, less frequently, in the udder and coronary bands. Human infection may occasionally occur and courses with self-limiting vesicular and pustular lesions in the hands and fingers [2]. Contagious ecthyma is endemic in most sheep and goat raising countries and leads to important eco- nomic losses [2]. In several countries, vaccination has been used with relative success to reduce the losses associated with the dis- ease [3]. An interesting aspect of PPVO biology is the ability to re-infect the hosts in spite of a strong immune response [4]. Neutralizing antibodies are barely – if so – detected and seem not to confer protection to reinfection [3]. Upon infection, PPVO strongly stimulates many events of the innate immunity, including phagocytosis, NK cell activity and production of several cytokines (IFN-a, b; TNF-a, GM-CSF) [5]. On the other hand, a number of immune escape mechanisms have been demonstrated for this agent [2–4]. The 138 kilobases (kb) PPVO genome encodes a series of products interfering with the host innate response, including an interferon resistance gene [6], inhibitors of GM-CSF and IL-2 [7,8],a Bcl-2-like apoptosis inhibitor [9], an IL-10 homologue [10],a vascular endothelial growth factor (VEGF) [11] and inhibitors of the NF-KB signaling pathway [12]. The survival strategy of PPVO seems to rely upon a balance between immune stimulatory and escape mechanisms [5]. In addition to the complex interactions with the immune system during infection, inactivated PPVO (iPPVO) has long been recognized to stimulate the innate immune response. Administra- tion of inactivated PPVO was first demonstrated to reduce the mortality of mice challenged with Pseudomonas aeruginosa [13]. Then, a number of studies investigated the immunostimulatory effects of iPPVO in different pathological conditions [5,14]. The promising effects of iPPVO as immunostimulant led to the http://dx.doi.org/10.1016/j.cellimm.2014.03.005 0008-8749/Ó 2014 Elsevier Inc. All rights reserved. ⇑ Corresponding author. Address: Avenida Roraima, 1000, Sala 4200, Prédio 20, Santa Maria, Rio Grande do Sul, Brazil. Fax: +55 5532208034. E-mail address: anzziliero@yahoo.com.br (D. Anziliero). Cellular Immunology 289 (2014) 36–41 Contents lists available at ScienceDirect Cellular Immunology journal homepage: www.elsevier.com/locate/ycimm