Viral Diversity and Epidemiology in Critically Endangered Yangtze Finless Porpoises (Neophocaena asiaeorientalis asiaeorientalis).

The Yangtze finless porpoise (YFP) (Neophocaena asiaeorientalis asiaeorientalis) is a critically endangered freshwater cetacean, with about 1,249 individuals thought to be left in the wild. However, viral entities and viral diseases of YFPs remain obscure. In this study, anal swabs for virome analysis were collected during the physical examination of YFPs in the Tian-E-Zhou Oxbow (TEO) ex situ reserve. A total of 19 eukaryotic viral species belonging to 9 families, including Papillomaviridae, Herpesviridae, Picornaviridae, Picobirnaviridae, Caliciviridae, Retroviridae, Parvoviridae, Virgaviridae, and Narnaviridae, and other unclassified viruses were identified based on metasequencing. Among these detected viruses, a novel herpesvirus (NaHV), two different kobuviruses (NaKV1-2), and six different papillomaviruses (NaPV1 to -6) were considered potential risks to YFPs and confirmed by PCR or reverse transcription-PCR (RT-PCR). Most YFPs sampled were found to harbor one or more kinds of detected viral genomes (52/58 [89.7%]). Surveillance results demonstrated that kobuvirus and herpesvirus displayed obvious age distribution and PVs showed significant gender difference in YFPs. According to species demarcation criteria in individual genera in Papillomaviridae, two novel species (referred to as Omikronpapillomavirus 2 and 3) and four novel isolates of PV were identified in YFPs. Further evolutionary analysis suggested that NaPVs would occupy the mucosal niche and that virus-host codivergence mixed with duplications and host-switching events drives the evolution of cetacean PVs. Divergence times of PVs in YFP and other cetacean reflect the incipient speciation of YFPs. In summary, our findings revealed the potential viral entities, their prevalence, and their evolutionary history in YFPs, which raises an important issue regarding effects of viral infection on the fitness of YFPs. IMPORTANCE The Yangtze finless porpoise (YFP) is the only cetacean species in freshwater following the functional extinction of the baiji (Lipotes vexillifer). Health management, disease treatment, and other special measures are important for maintaining the existing YFP populations, especially in in situ and ex situ reserves. The discovery of potential viral entities and their prevalence in YFPs raises an important issue regarding the effects of viral infection on the fitness of YFPs and may contribute to the conservation of YFPs. The evolutionary history of papillomaviruses in YFP and other cetaceans reflects the phylogeny of their hosts and supports the status of incipient species, opening a window to investigate the evolutionary adaptation of cetaceans to freshwater as well as their phylogeny to remedy the deficiency of fossil evidence.

Mangiferin and Taurine Ameliorate MSRV Infection by Suppressing NF-κB Signaling.

The emergence or reemergence of viruses pose a substantial threat and challenge to the world population, livestock, and wildlife. However, the landscape of antiviral agents either for human or animal viral diseases is still underdeveloped. The far tougher actuality is the case that there are no approved antiviral drugs in the aquaculture industry, although there are diverse viral pathogens. In this study, using a novel epithelial cell line derived from the brain of Micropterus salmoides (MSBr), inflammation and oxidative stress were found to implicate the major pathophysiology of M. salmoides rhabdovirus (MSRV) through transcriptome analysis and biochemical tests. Elevated levels of proinflammatory cytokines (interleukin-1ß [IL-1ß], IL-6, IL-8, tumor necrosis factor alpha [TNF-α], and gamma interferon [IFN-γ]) and accumulated contents of reactive oxygen species (ROS) as well as biomarkers of oxidative damage (protein carbonyl and 8-OHdG) were observed after MSRV infection in the MSBr cells. Mangiferin or taurine dampened MSRV-induced inflammation and rescued the oxidative stress and, thus, inhibited the replication of MSRV in the MSBr cells with 50% effective concentration (EC50) values of 6.77 µg/mL and 8.02 µg/mL, respectively. Further, mangiferin or taurine hampered the activation of NF-κB1 and the NF-κB1 promoter as well as the increase of phosphorylated NF-κB (p65) protein level induced by MSRV infection, indicating their antiviral mechanism by suppressing NF-κB signaling. These findings exemplify a practice approach, aiming to dampen and redirect inflammatory responses, to develop broad-spectrum antivirals. IMPORTANCE Aquaculture now provides almost half of all fish for human food in 2021 and plays a significant role in eliminating hunger, promoting health, and reducing poverty. There are diverse viral pathogens that decrease production in aquaculture. We developed a novel epithelial cell line derived from the brain of Micropterus salmoides, which can be used for virus isolation, gene expressing, and drug screening. In this study, we focus on M. salmoides rhabdovirus (MSRV) and revealed its pathophysiology of inflammation and oxidative stress. Aiming to dampen and redirect inflammatory responses, mangiferin or taurine exhibited their antiviral capability by suppressing NF-κB signaling. Our findings exemplify a practice approach to develop broad-spectrum antivirals by dampening and redirecting inflammatory responses.

Effect of dietary Bacillus subtilis supplement on Cd toxicokinetics and Cd-induced immune and antioxidant impairment of Procambarus clarkii.

Cadmium (Cd), a non-biodegradable contaminant in freshwater ecosystems, can pose a serious threat to aquatic animals at high levels. In this study, the Cd toxicokinetics and the immune and antioxidant defense were explored in Procambarus clarkii exposed to different levels of Cd (0, 0.1, 1.0 mg Cd/L) or treated with 1.0 mg Cd/L and dietary Bacillus subtilis supplementation (1 × 107 cfu/g). Results from the 21-day uptake and depuration experiment revealed that Cd exposure elicited a dose- and time-dependent uptake in all crayfish tissues, and the rank order of Cd concentration was gill > hepatopancreas > exoskeleton > muscle. The one-compartment model demonstrated that gills had the highest uptake rate (ku) value after Cd aqueous exposure and the ku and elimination rate (kd) values in gill, hepatopancreas, and exoskeleton of the group with 1.0 mg Cd/L were higher than those of the group at alow Cd concentration (0.1 mg Cd/L). However, B. subtilis could decrease Cd ku and increase Cd kd in hepatopancreas, resulting in the reduction of bioconcentration factors (BCF), steady-state concentrations (Css), and biological half-life (Tb1/2). A positive correlation was found between aqueous Cd concentration and the severity of hepatopancreas histopathological injury, while B. subtilis could ameliorate the pathological damage in the high Cd group. Similarly, aqueous exposure to Cd elevated malonaldehyde (MDA) content and suppressed the activities of lysozyme (LZM), acid phosphatase (ACP) in hepatopancreas and alkaline phosphatase (AKP) in hemolymph. The activities of superoxide dismutase (SOD) and catalase (CAT) in hepatopancreas were also inhibited. Nevertheless, they were all recovered with the dietary addition of B. subtilis. In conclusion, our results indicated that exposure to Cd significantly increased Cd accumulation and toxic damages in crayfish hepatopancreas, while dietary administration of B. subtilis to crayfish significantly decreased Cd accumulation and improved the immune and antioxidant defense, leading to the prevention in toxic effects of Cd.