Inactivated ostreid herpesvirus-1 induces an innate immune response in the Pacific oyster, Crassostrea gigas, hemocytes

Abstract

Infectious diseases are a major constraint to the expansion of shellfish production worldwide. Pacific oyster mortality syndrome (POMS), a polymicrobial disease triggered by the Ostreid herpesvirus-1 (OsHV-1), has devastated the global Pacific oyster (Crassostrea gigas) aquaculture industry. Recent ground-breaking research revealed that C. gigas possess an immune memory, capable of adaption, which improves the immune response upon a second exposure to a pathogen. This paradigm shift opens the door for developing ‘vaccines’ to improve shellfish survival during disease outbreaks. In the present study, we developed an in-vitro assay using hemocytes – the main effectors of the C. gigas immune system – collected from juvenile oysters susceptible to OsHV-1. The potency of multiple antigen preparations (e.g., chemically and physically inactivated OsHV-1, viral DNA, and protein extracts) to stimulate an immune response in hemocytes was evaluated using flow cytometry and droplet digital PCR to measure immune-related subcellular functions and gene expression, respectively. The immune response to the different antigens was benchmarked against that of hemocytes treated with Poly (I:C). We identified 10 antigen preparations capable of inducing immune stimulation in hemocytes (ROS production and positively expressed immune- related genes) after 1 h of exposure, without causing cytotoxicity. These findings are significant, as they evidence the potential for priming the innate immunity of oysters using viral antigens, which may enable cost-effective therapeutic treatment to mitigate OsHV-1/POMS. Further testing of these antigen preparations using an in-vivo infection model is essential to validate promising candidate pseudo-vaccines.

Surface-Charge-Driven Ferroptosis and Mitochondrial Dysfunction Is Involved in Toxicity Diversity in the Marine Bivalve Exposed to Nanoplastics

“…Notably, the GO terms enriched in the low-dose p-NP group were also significantly enriched in the high-dose p-NP group, but with greater significance, as indicated by the false discovery rate (FDR; Data Set S2). NPs are known to influence immune responses in diverse organisms, and this is particularly relevant for clams, which primarily rely on innate, nonlymphoid immune functions such as phagocytosis to mitigate stress. ,− This aspect was confirmed by both GO and KEGG analyses (Data Set S3). DEGs, as evident in the presented data, were chiefly engaged in processes like protein digestion and autophagy, with those related to mitochondrial functionsuch as ATP generation and mitochondrial respiratory chainbeing significantly enriched in the p-NP group (Figure d,e), highlighting a connection to mitochondrial and associated complications like energy production anomalies and cell death. , …”

The Resistance to Lethal Challenge with Ostreid herpesvirus-1 of Pacific Oysters (Crassostrea gigas) Previously Exposed to This Virus

“…Experimentally, inoculation of C. gigas with polyinosinic:polycytidylic acid (poly I:C), which is a synthetic double-stranded RNA used to stimulate anti-viral immune responses, evokes an interferon response which protects against subsequent challenge with OsHV-1 and the protection could be transmitted vertically to progeny [ 59 , 60 ]. Poly I:C, inactivated OsHV-1 and OsHV-1 proteins stimulated reactive oxygen species production and upregulation of immune-related genes ex vivo in C. gigas hemocytes [ 61 ]. Both intra- and inter-generational immunity to OsHV-1 could be explained by these pathways of innate immune stimulation.…”

Immune Priming of Pacific Oysters (Crassostrea gigas) to Induce Resistance to Ostreid herpesvirus 1: Comparison of Infectious and Inactivated OsHV-1 with Poly I:C

“…That heat-inactivated OsHV-1 produced a strong protective effect against subsequent exposure to virulent OsHV-1 confirms that immune priming with OsHV-1 does not require viral replication in the host. Experiments conducted more recently in a C. gigas hemocyte model enabled the same conclusion that viral replication was not required for an antiviral immune response [ 42 ]. This provides some information about the mechanisms of protection (see below).…”

“…TLR3 expression also affects glucose homeostasis; therefore, the role of TLR3 is more complex than PAMP recognition alone [ 47 ]. Hemocytes of C. gigas have been identified as effector cells with increased reactive oxygen species production and expression of immune-related genes after poly I:C stimulation [ 42 ]. Poly I:C treatment influences immune gene expression and apoptosis in a sustained manner [ 48 ].…”