Abstract
ABSTRACT: The innate immune system of honeybees mainly consists in antimicrobial peptides, cellular immunity and melanisation. In order to investigate the immune response of honeybees to immune stressors, three stress degrees were tested. Newly emerged bees naturally DWV-infected were collected from a Varroa mite-free apiary and divided into three experimental groups: naturally DWV infected bees, PBS injected bees, and artificially DWV super infected bees. Phenoloxidase activity and haemolymph cellular subtype count were investigated. Phenoloxidase activity was highest (P<0.05) in DWV-superinfected bees, and the haemocyte population differed within the three observed groups. Although, immune responses following DWV infection have still not been completely clarified, this investigation sheds light on the relation between cell immunity and the phenoloxidase activity of DWV-naturally infected honeybees exposed to additional stress such as injury and viral superinfection.
Highlights
Honeybees are social insects and their complex defence mechanisms are structured at social and individual levels (CREMER et al, 2007)
The PO cascade can be activated by some molecules such as lipopolysaccharides, β-glucans and peptidoglycans as observed in recent studies focused on the effect of these molecules on both phenoloxidase activity and haemocytes populations
At day 13, experimental groups showed significant differences in PO activity (P
Summary
Honeybees are social insects and their complex defence mechanisms are structured at social and individual levels (CREMER et al, 2007). Social innate immune defence is a complex and structured system characterized by the specific hygienic behaviour of honeybees (WILSON-RICH et al, 2009; ALAUX et al, 2010). The individual innate immune system consists in a wide variety of highly effective innate defence pathways based on humoral and cellular responses, such as phagocytosis, nodule formation and encapsulation mediated by melanisation (SCHMID et al, 2008; WILSON-RICH et al, 2009). Within these defence mechanisms, phenoloxidase (PO) is a key enzyme responsible for melanin production (SCHMID-HEMPEL, 2005; SIVA-JOTHY et al, 2005). The PO cascade can be activated by some molecules such as lipopolysaccharides, β-glucans and peptidoglycans as observed in recent studies focused on the effect of these molecules on both phenoloxidase activity and haemocytes populations
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