In vitro antiviral activity against herpes simplex virus in the abalone Haliotis laevigata

Abstract

As viruses are extremely abundant in oceans, marine organisms may have evolved novel metabolites to protect themselves from viral infection. This research examined a well-known commercial gastropod, abalone (Haliotidae), which in Australia have recently experienced disease due to a neurotropic infection, abalone viral ganglioneuritis, caused by an abalone herpesvirus (AbHV). Due to the lack of molluscan cell lines for culturing AbHV, the antiviral activity of the abalone Haliotis laevigata was assessed against another neurotropic herpesvirus, herpes simplex virus type 1 (HSV-1), using a plaque assay. The concentration range at which abalone extract was used for antiviral testing caused minimal (,10 %) mortality in Vero cells. Haemolymph (20 %, v/v) and lipophilic extract of the digestive gland (3000 mg ml "1 ) both substantially decreased the number and size of plaques. By adding haemolymph or lipophilic extract at different times during the plaque assay, it was shown that haemolymph inhibited viral infection at an early stage. In contrast, the antiviral effect of the lipophilic extract was greatest when added 1 h after infection, suggesting that it may act at an intracellular stage of infection. These results suggest that abalone have at least two antiviral compounds with different modes of action against viral infection, and provide a novel lead for marine antiviral drug discovery. INTRODUCTIONThe greatest biodiversity on earth is found in oceans, with 32 of the 33 animal phyla, 14 of which are not found on land (Nybakken & Bertness, 2005). Currently there are an estimated 230 000-275 000 taxonomically described marine species, and with the new species inventory accruing 1300-1500 species a year, there is predicted to be between 1.4-1.6 million species of macrofauna and flora in the ocean (Bouchet, 2006). Viruses are also abundant in oceans, with about 10 9 or more viruses per litre of water, exceeding numbers of bacteria and Archaea by about 15-fold (Bergh et al., 1989;Fuhrman, 1999;Suttle, 2007). Viral infections are common in marine environments, with an estimated 10 23 infections occurring every second (Suttle, 2007).Due to natural selection, a range of antiviral agents may have evolved in marine organisms to protect them from viruses. The innate defences available to marine organisms can include secondary metabolites, bioactive peptides and proteins, thus serving as models for the development of new drugs for treating human disease. Indeed, several important antiviral compounds of marine origin have been reported, including didemnins (Caribbean tunicate, Trididemnum solidum), eudistomins (shallow-water tunicates within the genus Eudistoma), mycalamide A and B (New Zealand sponge, Mycale sp.), papuamides A (Theonella mirabilis and Theonella swinhoei sponges), avarone (Dysidea avara sponge), gymnochrome D (fossil crinoid Gymnocrinus richer), microspinosamide (Sidonops microspinosa sponge), solenolide A (gorgonian of the genus Solenopodium), hennoxazole A (Polyfibrospongia sp. sponge), thyrsiferol (red alg...

Antiviral immunity in marine molluscs

“…Haemocyanins are copper containing glycoproteins and a major haemolymph component, approximately 50 % to w90 %, of some mollusc species (Coates & Nairn, 2014). Abalone haemocyanin inhibits HSV-1 infection of Vero cells, presumably by blocking viral entry (Dang et al, 2011;Zanjani et al, 2014). The anti-HSV-1 activity of abalone plasma does not increase above baseline levels in response to experimental infection with AbHV (Dang et al, 2013).…”

“…Investigations into the antiviral activity of molluscan AMPs and tissue homogenates is hampered by the lack of continuous cell lines from marine molluscs (Yoshino et al, 2013) and the fact that OsHV-1 cannot be cultured in primary cell cultures from bivalves (details in Garcia et al, 2011). Numerous studies have therefore utilized a heterologous model involving HSV-1 and African green monkey kidney (Vero) cells to identify antiviral compounds in tissue homogenates from commercially important bivalves (Carriel-Gomes et al, 2006;Defer et al, 2009;Green et al, 2014c;Olicard et al, 2005a, b;Segarra et al, 2014a;Zeng et al, 2008) and gastropods (Dang et al, 2011;Zanjani et al, 2014).…”

“…and no studies of cephalopods. Studies investigating the antiviral response of molluscs have mainly focused on identifying antiviral compounds, measuring immune enzyme activity or characterizing the transcriptional response to OsHV-1 infection Dang et al, 2011Dang et al, , 2013Fleury & Huvet, 2012;Green & Montagnani, 2013;Green et al, 2014c;Jouaux et al, 2013;Moreau et al, 2015;Normand et al, 2014;Olicard et al, 2005a, b;Renault et al, 2011;Rosani et al, 2014;Segarra et al, 2014a, c). These studies suggest that the molluscan antiviral response has similarities to the vertebrate interferon pathway (Green & Montagnani, 2013).…”

“…Selective breeding programmes would benefit from identifying the genetic mechanism(s) utilized by resistant molluscs for maintaining viral loads below the mortality threshold. A good starting point would be the antiviral plasma proteins (haemocyanin and cavortin) that are known to interfere with mammalian virus replication (Dang et al, 2011;Green et al, 2014c;Olicard et al, 2005b). Normand et al (2014) concluded expression levels of superoxide dismutase metalloenzymes (i.e.…”

Variation in the antiviral and antibacterial activity of abalone Haliotis laevigata, H. rubra and their hybrid in South Australia

“…Recently, we have shown that plasma of abalone haemolymph also contains antiviral 100 compounds using the plaque assay for HSV-1 (Dang et al 2011 …”