Infectivity of Strongyloides venezuelensis is influenced by variations in temperature and time of culture Eleuza Rodrigues Machado a, * , Marlene Tiduko Ueta a,1 , Elaine Vicente Lourenço b , Fernanda de Freitas Aníbal c , Érica Vitalino Garcia da Silva c , Maria Cristina Roque-Barreira b , Julia Maria Costa-Cruz d , Lúcia Helena Faccioli c,1 a Departamento de Parasitologia, Instituto de Biologia, Universidade Estadual de Campinas, Cidade Universitária ‘Zeferino Vaz’ s/n. CEP. 13083-970, Caixa Postal 6109, Campinas, SP, Brazil b Departamento de Biologia Celular, Molecular e Bioagentes Patogênicos, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, SP, Brazil c Departamento de Análises Clínicas, Toxicológicas e Bromatológicas, Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, SP, Brazil d Departamento de Imunologia, Microbiologia e Parasitologia, Instituto de Ciências Biomédicas, Universidade Federal de Uberlândia, Uberlândia, MG, Brazil article info Article history: Received 3 December 2009 Received in revised form 25 June 2010 Accepted 28 June 2010 Available online 3 July 2010 Keywords: Strongyloides venezuelensis Cytokine Eosinophilia Antibody Mononuclear cells Temperature Time abstract The present research investigated the influence of temperature and time of larvae culture on the infectivity of Strongyloides venezuelensis. Mice were infected s.c. with 1500 larvae of S. venezuelensis main- tained at 28 °C for three days of culture (dc), 28 °C for seven dc or 18 °C for seven dc. On days 1, 3, 5, 7, 14 and 21 post-infection the animals were sacrificed and cell numbers in the blood, peritoneal cavity fluid (PCF), broncoalveolar fluid (BALF), cytokines, immunoglobulins, number of parasites and eggs/g of feces were quantified. Results demonstrated an increase in eosinophils and mononuclear cells in the blood, PCF and BALF of infected mice. Larvae at 28 °C/3dc induced earlier eosinophils in the PCF and BALF as opposed to larvae at 28 °C/7dc and 18 °C/7dc. Larvae at 28 °C/7dc induced higher synthesis of IL-4, IL-5 and IL-10 on days 5 and 7 post-infection. Larvae at 28 °C/3dc in culture induced higher synthesis of IL-12 than lar- vae of seven dc, but time in culture induced better synthesis of IFN-c after larval migration had ceased and only adult worms were present. Larvae at 28 °C/3dc in culture induced higher synthesis of IgG and IgG1 and expelled less female parasites than larvae cultivated for seven days. In conclusion, it was observed that the infectivity of S. venezuelensis is influenced by variations in temperature and time of culture. Ó 2010 Elsevier Inc. All rights reserved. 1. Introduction Strongyloidiasis is caused by a nematode of the genus Strongy- loides occurring in humans, domestic and wild mammals, birds, reptiles and amphibians (Grove, 1996). This form of helminthiasis has a worldwide distribution but appears primarily in tropical and subtropical areas where environmental conditions encourage its development (Thompson et al., 2006; Olsen et al., 2009). The life cycle of Strongyloides sp. is divided into two types of development: direct and indirect cycles. In the direct cycle, eggs are expelled from the host with rhabditiform larvae (L1), in the environment they are transformed into rhabditiform larvae (L2) of the second-stage, which develop into filariform larvae, also called infectious third-stage larvae (L3i). In the indirect cycle, eggs are also expelled from the host with rhabditiform larvae (L1) and in the environment are transformed into rhabditiform larvae (L2) of the second-stage, that develop through free-living L3 and L4 stages to free-living adult and females. Free-living adults reproduce sexu- ally in the environment and all descendents become infective L3. The L3 of either cycle can penetrate the skin of the host, pass through the circulation to the lungs, enter the air passages, be swallowed, and finally reach the intestine where they mature into adult egg-laying females (Neva, 1986; Grove, 1996). The relationship between helminths and their hosts is charac- terized by a cellular immune response mediated by eosinophils, mast cells, and with a significant increase in the production of IL- 3, IL-4, IL-5 cytokines (Rotman et al., 1996; Tegoshi et al., 1997; Machado et al., 2005; Maizels et al., 2009; Machado et al., 2009) and IgA, IgE, IgG and IgM antibodies (Neva, 1986; Atkins et al., 1997; Machado et al., 2005, 2008). In humans and in some animals the immune response induced by Strongyloides stercoralis is able to stop the infection. However, some parasites can escape the protec- tive response and induce chronic infection that may persist for 0014-4894/$ - see front matter Ó 2010 Elsevier Inc. All rights reserved. doi:10.1016/j.exppara.2010.06.027 * Corresponding author. Fax: +55 19 3788 6282. E-mail addresses: eleuzarm_2007@hotmail.com, ermachad@hotmail.com (E.R. Machado). 1 The authors contributed equally to this study. Experimental Parasitology 127 (2011) 72–79 Contents lists available at ScienceDirect Experimental Parasitology journal homepage: www.elsevier.com/locate/yexpr