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PubMed2026

Culture of infectious human norovirus isolated from live contaminated oysters.

Human noroviruses are a major cause of foodborne outbreaks worldwide. Filter-feeding shellfish, such as oysters, can bioaccumulate these viruses in their digestive tissue when grown in sewage-impacted coastal areas and are often implicated in norovirus foodborne outbreaks. Despite the high sensitivity of current molecular assays, these methods for norovirus detection in shellfish fail to distinguish between infectious and non-infectious particles. Assessing norovirus infectivity in shellfish remains a challenge due to the lack of suitable isolation methods that maintain capsid integrity. In this study, a protocol for isolating infectious norovirus from oyster tissues, based on chloroform-butanol elution and polyethylene glycol concentration (CB-PEG), was optimized for the recovery of human norovirus GI and GII. While CB-PEG method recovered various norovirus GI and GII genotypes, it was less efficient at the genomic level than a protocol based on proteinase K elution (adapted from ISO 15216) and showed genotype-dependent viral recovery rates. By optimizing the flocculation step, we improved the method's compatibility with human intestinal enteroid (HIE) cultures. Using this approach, we successfully quantified infectious norovirus GII.3 titers recovered from artificially-contaminated live oysters. Interestingly, infectious virus was better isolated following a freezing step of the digestive tissues, with titers ranging from 13 to 40 TCID50/mL for positive samples. In conclusion, this study established an optimized methodological approach for the relative quantification of infectious norovirus GII.3 in shellfish, paving the way for future research on viral persistence and inactivation strategies in this foodstuff.

Norovirus↗

PubMed2026

Multi-omics analysis reveals stage-associated differences in gut immunity and microbiota between juvenile and adult common carp (Cyprinus carpio).

In vertebrates, the development of intestinal immunity is closely associated with dynamic changes in the gut microbiota. However, stage-associated differences in intestinal immunity and gut microbial communities remain poorly characterized in teleost fish. In this study, transcriptomic analysis combined with 16S rRNA gene sequencing was employed to characterize intestinal immunity and gut microbial communities in juvenile and adult common carp (Cyprinus carpio). Transcriptomic profiling revealed marked developmental differences in intestinal immune function. Juvenile carp exhibited a predominantly innate immune phenotype, characterized by elevated expression of pro-inflammatory cytokines, antimicrobial peptides, and lysozyme-related genes. This immune profile was accompanied by enhanced mucosal barrier function and a relatively pro-inflammatory intestinal environment. In contrast, adult carp displayed increased expression of genes associated with adaptive immunity, suggesting that adult common carp exhibit relatively stronger adaptive immune characteristics than juvenile fish. Gut microbiota analysis demonstrated significant stage-dependent differences in microbial diversity and community composition. Juvenile fish were enriched with bacterial taxa potentially associated with innate immune activation, whereas adult fish harbored distinct microbial communities linked to intestinal homeostasis and barrier maintenance. Furthermore, correlation analyses identified significant associations between specific microbial taxa and innate immune-related gene expression, suggesting a close association between gut microbiota composition and intestinal immune characteristics in juvenile and adult common carp. Collectively, these findings reveal stage-associated differences in intestinal immunity and gut microbial communities between juvenile and adult common carp, thereby providing insights into intestinal immune characteristics at different developmental stages in teleost fish.

Animals↗

PubMed2026

Pre-transport dietary chitosan improves the physiological robustness of juvenile largemouth bass (Micropterus salmoides) by modulating antioxidant and inflammatory responses.

The acute stress caused by long-distance transport can lead to oxidative damage, immune dysfunction, and health deterioration in fish. This study evaluated dietary chitosan as a pre-transport nutritional strategy for juvenile largemouth bass (Micropterus salmoides). Five experimental diets contained chitosan at 0, 2.5, 5.0, 7.5, or 10.0 g/kg, designated as p0, p25, p50, p75, and p100, respectively, for 56 d. The effects of dietary chitosan were evaluated using growth performance, feed utilization, digestive function, antioxidant capacity, nonspecific immunity, and resistance to Aeromonas hydrophila infection. Then, fish from the p0 and p50 groups underwent a 12-h transport stress test, with samples collected before, during, and 7 d after transport. Dietary chitosan improved most of these parameters. Among the treatment groups, p50 and p75 showed the best overall performance. The dose-response analysis further indicated that the appropriate dietary inclusion range was 5.0-7.5 g/kg. Under transport stress, fish in the p50 group exhibited more stable antioxidant enzyme responses and lower lipid peroxidation, as indicated by reduced MDA levels. Consistent with these enzyme responses, antioxidant-related genes remained relatively stable. At the same time, expression patterns related to the Nrf2-Keap1 and NF-κB signaling pathways suggested that 5.0 g/kg chitosan alleviated transport-induced oxidative damage and inflammation. Dietary chitosan also attenuated pro-inflammatory gene induction and altered the temporal expression patterns of anti-inflammatory genes. Overall, 5.0-7.5 g/kg dietary chitosan is suitable for juvenile largemouth bass, and 5.0 g/kg may serve as an effective pre-transport dietary inclusion level.

Animals↗

PubMed2026

Optimization of a niosomal formulation for Quercetin delivery: Comparative effects on growth performance, antioxidant and immune responses, and disease resistance against Streptococcus iniae in rainbow trout (Oncorhynchus mykiss).

Quercetin (QUR) is a flavonoid with antibacterial and antioxidant properties that has been studied for its effects on fish health and the immune system. Due to the low bioavailability of QUR, the present study was primarily aimed at developing a niosomal formulation of QUR to enhance its bioavailability and therapeutic properties. The performance of niosomal QUR was then compared with that of its free form by evaluating their effects on the growth and immune system of rainbow trout, Oncorhynchus mykiss. For this purpose, an optimal QUR-containing niosome was formulated by testing different proportions of cholesterol, surfactant, and stabilizer, and the niosomes were then added to the fish diet. A QUR-free diet and a diet containing QUR-free niosomes (QFN) were considered control groups. Niosomes prepared at low hydrophilic-lipophilic balance (HLB) values showed higher QUR entrapment efficiency (QUR-EE%) (P < 0.01). An increase in the molar ratio of cholesterol to surfactant significantly reduced QUR-EE% (P < 0.05). A surfactant/cholesterol/stabilizer ratio of 1:1:0.1 increased QUR-EE% (P < 0.05). The particle size of the niosomes was also affected by HLB and the surfactant/cholesterol/stabilizer ratio. Low HLB values resulted in smaller particle sizes (P < 0.01). Furthermore, a surfactant/cholesterol/stabilizer ratio of 1:1:0.1 resulted in the smallest niosomal particle size (P < 0.05). The presence of diacetyl phosphate as the stabilizer in the formulation improved the niosomal zeta potential to -40.55 mV. The optimal niosomal formulation (HLB = 6.6; surfactant/cholesterol/stabilizer ratio of 1:1:0.1) remained stable at 2 °C over 10 days of storage, as the niosomal QUR content and size did not show significant changes during this period (P > 0.01). After preparation of the diets containing the optimal niosomal QUR, fish were fed the experimental diets for two months. QUR, in both niosomal and free forms, resulted in better growth performance than the QUR-free diets (P < 0.01). There were no significant differences in growth performance between the free and niosomal forms of QUR; however, 500 mg/kg QUR showed significantly better growth performance than 250 mg/kg QUR (P < 0.01). Although both the niosomal and free forms of QUR enhanced immune and antioxidant components in the fish, the effects of the niosomal form were more significant (P < 0.01). In addition, QUR in both free and niosomal forms reduced fish mortality after challenge with Streptococcus iniae. In conclusion, the results of this study suggest that the niosomal form of QUR has strong potential for improving the immune system of fish and increasing resistance to S. iniae infection.

Animals↗