Abstract
Assessing components of the immune system may reflect disease resistance. In some invertebrates, heat shock proteins (HSPs) are immune effectors and have been described as potent activators of the innate immune response. Several diseases have become a threat to abalone farming worldwide; therefore, increasing disease resistance is considered to be a long-term goal for breeding programs. A trait will respond to selection only if it is determined partially by additive genetic variation. The aim of this study was to estimate the heritability (h 2) and the additive genetic coefficient of variation (CV A) of HSP70 as a component of innate immunity of the abalone Haliotis rufescens, in order to assess its potential response to selection. These genetic components were estimated for the variations in the intracellular (in haemocytes) and extracellular (serum) protein levels of HSP70 in response to an immunostimulant agent in 60 full-sib families of H. rufescens. Levels of HSP70 were measured twice in the same individuals, first when they were young and again when they were pre-harvest adults, to estimate the repeatability (R), the h 2 and the potential response to selection of these traits at these life stages. High HSP70 levels were observed in abalones subjected to immunostimulation in both the intracellular and extracellular haemolymph fractions. This is the first time that changes in serum levels of HSP70 have been reported in response to an immune challenge in molluscs. HSP70 levels in both fractions and at both ages showed low h 2 and R, with values that were not significantly different from zero. However, HSP70 induced levels had a CV A of 13.3–16.2% in young adults and of 2.7–8.1% in pre-harvest adults. Thus, despite its low h 2, HSP70 synthesis in response to an immune challenge in red abalone has the potential to evolve through selection because of its large phenotypic variation and the presence of additive genetic variance, especially in young animals.
Highlights
IntroductionDisease resistance may be reflective of immune function and can be measured by assessing the resistance of the organism to a particular pathogen or by measuring components of the immune system [1, 2] Similar to the majority of invertebrates, abalone only possess an innate immune system with humoral and cellular (mediated by haemocytes) defence mechanisms [3]
Disease resistance may be reflective of immune function and can be measured by assessing the resistance of the organism to a particular pathogen or by measuring components of the immune system [1, 2] Similar to the majority of invertebrates, abalone only possess an innate immune system with humoral and cellular defence mechanisms [3]
After 24 h, individuals injected with zymosan had approximately 3-fold higher levels of heat shock protein 70 (HSP70) in the haemocytes and serum compared with those of non-injected control abalone or control abalone injected with sterilised seawater (SSW) (P < 0.01) (Fig 1)
Summary
Disease resistance may be reflective of immune function and can be measured by assessing the resistance of the organism to a particular pathogen or by measuring components of the immune system [1, 2] Similar to the majority of invertebrates, abalone only possess an innate immune system with humoral and cellular (mediated by haemocytes) defence mechanisms [3]. It goes without saying that the immunomodulatory function of HSP70 has been well studied in vertebrates [14,15,16]; it is known to have both intracellular (cytoprotective/anti-apoptotic) and extracellular functions (immunogenic) [4]. These immune functions have been less studied in invertebrates, HSP70 appears to have similar roles to those described for vertebrates [17]
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