Autophagy is an essential component of host immunity and used by viruses for survival. However, the autophagy signaling pathways involved in virus replication are poorly documented. Here, we observed that rabies virus (RABV) infection triggered intracellular autophagosome accumulation and results in incomplete autophagy by inhibiting autophagy flux. Subsequently, we found that RABV infection induced the reduction of CASP2/caspase 2 and the activation of AMP-activated protein kinase (AMPK)-AKT-MTOR (mechanistic target of rapamycin) and AMPK-MAPK (mitogen-activated protein kinase) pathways. Further investigation revealed that BECN1/Beclin 1 binding to viral phosphoprotein (P) induced an incomplete autophagy via activating the pathways CASP2-AMPK-AKT-MTOR and CASP2-AMPK-MAPK by decreasing CASP2. Taken together, our data first reveals a crosstalk of BECN1 and CASP2-dependent autophagy pathways by RABV infection.
f Human enteric viruses are among the main causative agents of shellfish-associated outbreaks. In this study, the kinetics of viral bioaccumulation in live oysters and the heat stabilities of the predominant enteric viruses were determined both in tissue culture and in oyster tissues. A human norovirus (HuNoV) GII.4 strain, HuNoV surrogates (murine norovirus [MNV-1], Tulane virus [TV]), hepatitis A virus (HAV), and human rotavirus (RV) bioaccumulated to high titers within oyster tissues, with different patterns of bioaccumulation for the different viruses. We tested the thermal stability of each virus at 62, 72, and 80°C in culture medium. The viruses can be ranked from the most heat resistant to the least stable as follows: HAV, RV, TV, MNV-1. In addition, we found that oyster tissues provided protection to the viruses during heat treatment. To decipher the mechanism underlying viral inactivation by heat, purified TV was treated at 80°C for increasing time intervals. It was found that the integrity of the viral capsid was disrupted, whereas viral genomic RNA remained intact. Interestingly, heat treatment leading to complete loss of TV infectivity was not sufficient to completely disrupt the receptor binding activity of TV, as determined by the porcine gastric mucin-magnetic bead binding assay. Similarly, HuNoV virus-like particles (VLPs) and a HuNoV GII.4 strain retained some receptor binding ability following heat treatment. Although foodborne viruses have variable heat stability, 80°C for >6 min was sufficient to completely inactivate enteric viruses in oysters, with the exception of HAV.A pproximately 7.6 million to 14.5 million illnesses in the United States are attributed to the consumption of contaminated seafood each year, and enteric viruses are responsible for more than 50% of these cases (1). In a review of the available epidemiological evidence, human norovirus (HuNoV) and hepatitis A virus (HAV) were the leading viruses associated with shellfish, accounting for 83.7% and 12.8% of outbreaks, respectively (2). The type of shellfish most frequently associated with viral outbreaks was oysters, which were the vehicle in 58.4% of outbreaks (2). In some regions, human enteric viruses are practically ubiquitous in harvested shellfish. Keller et al. (3) showed that 100% of shellfish samples collected from Vitória Bay, Espírito Santo, Brazil, were positive for rotavirus (RV) and adenovirus. However, only 80% of the growing water samples were positive for these pathogens. Viral titers were 400 times higher in the shellfish samples than in the growing water, indicating high levels of natural bioaccumulation (3). In the Galician Rias area, the largest shellfish production area in the European Union, 55% of mussel, clam, and cockle samples were contaminated by HuNoV genogroup I (GI) and GII and HAV (4). Thus, understanding of the ecology and persistence of enteric viruses in shellfish is needed to help prevent future outbreaks.The consumption of uncooked contaminated bivalve shellfish continues to pose a public ...
Human norovirus (NoV) is the leading cause of foodborne disease in the United States, and epidemiological studies have shown that fresh produce is one of the major vehicles for the transmission of human NoV. However, the mechanisms of norovirus contamination and persistence in fresh produce are poorly understood. The objective of this study is to determine whether human NoV surrogates, murine norovirus (MNV-1) and Tulane virus (TV), can attach and become internalized and disseminated in strawberries grown in soil. The soil of growing strawberry plants was inoculated with MNV-1 and TV at a level of 10 8 PFU/plant. Leaves and berries were harvested over a 14-day period, and the viral titer was determined by plaque assay. Over the course of the study, 31.6% of the strawberries contained internalized MNV-1, with an average titer of 0.81 ؎ 0.33 log 10 PFU/g. In comparison, 37.5% of strawberries were positive for infectious TV, with an average titer of 1.83 ؎ 0.22 log 10 PFU/g. A higher percentage (78.7%) of strawberries were positive for TV RNA, with an average titer of 3.15 ؎ 0.51 log 10 RNA copies/g as determined by realtime reverse transcriptase quantitative PCR (RT-qPCR). In contrast, no or little virus internalization and dissemination were detected when TV was inoculated into bell peppers grown in soil. Collectively, these data demonstrate (i) virally contaminated soils can lead to the internalization of virus via plant roots and subsequent dissemination to the leaf and fruit portions of growing strawberry plants and (ii) the magnitude of internalization is dependent on the type of virus and plant.H uman norovirus (NoV) is the major cause of nonbacterial gastroenteritis, contributing to over 95% of the cases of nonbacterial acute gastroenteritis and an estimated 58% of all foodborne illnesses reported annually in the United States (1-4). In recent years, fresh produce has been identified as a leading cause of foodborne illness in the United States (3, 5, 6). Human NoV alone accounts for over 40% of the fresh produce-related illnesses reported each year in the United States (1, 2, 4-8). Human NoV has been attributed to outbreaks in many diverse types of produce, including fresh cut fruit, lettuce, tomatoes, melons, salads, green onions, strawberries, blueberries, raspberries, and salsa, as well as many others (5-7, 9-15). Human NoV is resistant to common disinfectants, has a low infectious dose, and is highly stable in the environment, which contributes to the high prevalence of foodborne outbreaks associated with the virus and its presence and persistence in food commodities (3,16,17).Foods can become contaminated with human NoV at any point from farm to fork, including production, processing, and preparation. Infected food handler contamination and exposure to fecally contaminated water are thought to be the most frequent modes of human NoV contamination of foods (2, 5, 10, 18). The use of irrigation water that is contaminated with fecal matter is considered a significant cause of viral contamination in soft b...
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