One-pot Golden Gate Assembly of an avian infectious bronchitis virus reverse genetics system.

Avian infectious bronchitis is an acute respiratory disease of poultry of particular concern for global food security. Investigation of infectious bronchitis virus (IBV), the causative agent of avian infectious bronchitis, via reverse genetics enables deeper understanding of virus biology and a rapid response to emerging variants. Classic methods of reverse genetics for IBV can be time consuming, rely on recombination for the introduction of mutations, and, depending on the system, can be subject to genome instability and unreliable success rates. In this study, we have applied data-optimized Golden Gate Assembly design to create a rapidly executable, flexible, and faithful reverse genetics system for IBV. The IBV genome was divided into 12 fragments at high-fidelity fusion site breakpoints. All fragments were synthetically produced and propagated in E. coli plasmids, amenable to standard molecular biology techniques for DNA manipulation. The assembly can be carried out in a single reaction, with the products used directly in subsequent viral rescue steps. We demonstrate the use of this system for generation of point mutants and gene replacements. This Golden Gate Assembly-based reverse genetics system will enable rapid response to emerging variants of IBV, particularly important to vaccine development for controlling spread within poultry populations.

Stigma Related to the Non-Medical Use and Diversion of Prescription Stimulant Drugs: Should We Care.

BACKGROUND: Non-medical use (NMU) and diversion of prescription stimulants are prevalent on college campuses. Diversion represents a primary source of acquisition for NMU among young adults. This study examined relationships between stigmatizing beliefs related to NMU and diversion of stimulant medications and engagement in these behaviors, as well as how such perceptions are associated with indicators of psychological distress among those who engage in these behaviors. METHODS: Young adults (N = 384) were recruited from a large US university to participate in this cross-sectional electronic survey-based study. Relationships between stigma variables and NMU and diversion were assessed. Among those who engage in NMU and diversion, we tested relationships between stigma variables and indicators of psychological distress, using validated instruments. RESULTS: Perceived social and personal stigmatic beliefs did not significantly predict NMU. However, perceived social and personal stigma of diversion significantly reduced diversion likelihood. For NMU, associations were found between stigma variables and indicators of psychological distress. Markedly, we found that as stigmatic perceptions of NMU increased, so did depressive, anxiolytic, and suicidal symptomatology among those who engage in NMU. CONCLUSIONS: Stigmatization does not deter NMU; however, stigmatization is positively associated with psychological harm among those who engage in NMU. Interventions should be developed to reduce stigmatization in order to improve psychological health among those who engage in NMU. Stigmatic perceptions of diversion were not predictive of psychological harm, though they are negatively associated with diversion behavior.

A novel optimized pre-embedding antibody-labelling correlative light electron microscopy technique.

In the intricate environment of a cell, many studies seek to discover the location of specific events or objects of interest. Advances in microscopy in recent years have allowed for high detail views of specific areas of cells of interest using correlative light electron microscopy (CLEM). While this powerful technique allows for the correlation of a specific area of fluorescence on a confocal microscope with that same area in an electron microscope, it is most often used to study tagged proteins of interest. This method adapts the correlative method for use with antibody labelling. We have shown that some cellular structures are more sensitive than others to this process and that this can be a useful technique for laboratories where tagged proteins or viruses, or dedicated CLEM instruments are not available.

Effect of Timing by Endometrial Receptivity Testing vs Standard Timing of Frozen Embryo Transfer on Live Birth in Patients Undergoing In Vitro Fertilization: A Randomized Clinical Trial.

Importance: Endometrial receptivity testing is purported to improve live birth following frozen embryo transfer by identifying the optimal embryo transfer time for an individual patient; however, data are conflicting. Objective: To compare live birth from single euploid frozen embryo transfer according to endometrial receptivity testing vs standardized timing. Design, Setting, and Participants: Double-blind, randomized clinical trial at 30 sites within a multicenter private fertility practice in the Eastern US. Enrollment was from May 2018 to September 2020; follow-up concluded in August 2021. Participants underwent in vitro fertilization, preimplantation genetic testing for aneuploidy, endometrial receptivity testing, and frozen embryo transfer. Those with euploid blastocyst(s) and an informative receptivity result were randomized. Exclusion criteria included recurrent pregnancy loss, recurrent implantation failure, surgically aspirated sperm, donor egg(s), and unmitigated anatomic uterine cavity defects. Interventions: The intervention group (n = 381) underwent receptivity-timed frozen embryo transfer, with adjusted duration of progesterone exposure prior to transfer, if indicated by receptivity testing. The control group (n = 386) underwent transfer at standard timing, regardless of receptivity test results. Main Outcomes and Measures: The primary outcome was live birth. There were 3 secondary outcomes, including biochemical pregnancy and clinical pregnancy. Results: Among 767 participants who were randomized (mean age, 35 years), 755 (98%) completed the trial. All randomized participants were analyzed. The primary outcome of live birth occurred in 58.5% of transfers (223 of 381) in the intervention group vs 61.9% of transfers (239 of 386) in the control group (difference, -3.4% [95% CI, -10.3% to 3.5%]; rate ratio [RR], 0.95 [95% CI, 0.79 to 1.13]; P = .38). There were no significant differences in the intervention vs the control group for the prespecified secondary outcomes, including biochemical pregnancy rate (77.2% vs 79.5%, respectively; difference, -2.3% [95% CI, -8.2% to 3.5%]; RR, 0.97 [95% CI, 0.83 to 1.14]; P = .48) and clinical pregnancy rate (68.8% vs 72.8%, respectively; difference, -4.0% [95% CI, -10.4% to 2.4%]; RR, 0.94 [95% CI, 0.80 to 1.12]; P = .25). There were no reported adverse events. Conclusions and Relevance: Among patients for whom in vitro fertilization yielded a euploid blastocyst, the use of receptivity testing to guide the timing of frozen embryo transfer, compared with standard timing for transfer, did not significantly improve the rate of live birth. The findings do not support routine use of receptivity testing to guide the timing of embryo transfer during in vitro fertilization. Trial Registration: ClinicalTrials.gov Identifier: NCT03558399.

The relationship between trait emotional intelligence and problematic alcohol use among college students.

Background: Problematic alcohol use among college students is a significant public health concern. Emotional intelligence (EI), or the ability to detect one's own and others' emotions and to use this information to direct behavior, is suggested to mitigate problematic alcohol use. The purpose of this study was to examine the relationship between EI and problematic alcohol use among college students while controlling for drug use covariates. Methods: This cross-sectional study utilized an online survey comprised of previously validated measures to determine EI, problematic alcohol use, and drug use among college students from a large, public university in the south-central United States. Regression modeling and independent samples t-test were used to determine the relationship between EI and problematic alcohol use. Results: Problematic alcohol consumption was reported among 27.3% of participants (n=587). In regression modeling, EI demonstrated a significant, protective effect on problematic alcohol use (b =-0.050, P <0.001, 95% CI: -0.076 - -0.023), when adjusting for important covariates. Independent samples t-test showed that students who screened positive for harmful alcohol use reported significantly lower EI values than those who did not (Mean difference=4.53, t =2.98, P =0.003, 95% CI: 1.54-7.51). Conclusion: The findings from this study show that problematic alcohol use is prevalent among college students and EI may provide a protective effect against this deleterious behavior. Given the findings observed in this study, university officials should incorporate EI training into the university curriculum, such as in onboarding courses for freshman and transfer students, to target prevention of potentially harmful alcohol consumption and associated negative health impacts.

Live birth after transfer of a single euploid vitrified-warmed blastocyst according to standard timing vs. timing as recommended by endometrial receptivity analysis.

OBJECTIVE: To determine whether endometrial receptivity analysis (ERA) improves live births in patients with and without a history of unsuccessful frozen embryo transfers (FETs). DESIGN: Retrospective cohort study. SETTING: Large reproductive center. PATIENT(S): Patients with and without ERA before euploid single FET were included in the analysis. INTERVENTION(S): Subjects in the exposed group underwent ERA and ERA-timed FETs. Subjects in the unexposed group followed a standard protocol FET without ERA. Outcomes were compared between nonreceptive and receptive subjects undergoing an ERA-timed FET and between ERA-timed vs. standard protocol FETs. MAIN OUTCOME MEASURE(S): The primary outcome was a live birth; secondary outcomes were biochemical and clinical pregnancy rates. RESULT(S): A total of 307 ERA-timed FETs and 2,284 standard protocol FETs were analyzed. One hundred twenty-five patients (40.7%) were ERA receptive, and 182 (59.3%) were ERA nonreceptive. After adjusting for the number of the previously failed FETs, there was no difference in the proportion of receptive and nonreceptive ERA results. There were no statistically significant differences in live births in patients with ERA-receptive vs. ERA-nonreceptive results (48.8% and 41.7%, respectively; adjusted odds ratio 1.17; 95% CI, 0.97-1.40). There were no statistically significant differences in live births in patients with or without ERA testing results before FET (44.6% and 51.3%, respectively; adjusted odds ratio 0.87; 95% CI, 0.73-1.04). CONCLUSION(S): Patients with an increasing number of previous failed euploid FET cycles are not at an increased risk of a displaced window of implantation. Patients categorized as receptive vs. nonreceptive and those without ERA testing results have comparable FET success rates.

Coronavirus RNA Synthesis Takes Place within Membrane-Bound Sites.

Infectious bronchitis virus (IBV), a gammacoronavirus, is an economically important virus to the poultry industry, as well as a significant welfare issue for chickens. As for all positive strand RNA viruses, IBV infection causes rearrangements of the host cell intracellular membranes to form replication organelles. Replication organelle formation is a highly conserved and vital step in the viral life cycle. Here, we investigate the localization of viral RNA synthesis and the link with replication organelles in host cells. We have shown that sites of viral RNA synthesis and virus-related dsRNA are associated with one another and, significantly, that they are located within a membrane-bound compartment within the cell. We have also shown that some viral RNA produced early in infection remains within these membranes throughout infection, while a proportion is trafficked to the cytoplasm. Importantly, we demonstrate conservation across all four coronavirus genera, including SARS-CoV-2. Understanding more about the replication of these viruses is imperative in order to effectively find ways to control them.

Manipulation of the unfolded protein response: A pharmacological strategy against coronavirus infection.

Coronavirus infection induces the unfolded protein response (UPR), a cellular signalling pathway composed of three branches, triggered by unfolded proteins in the endoplasmic reticulum (ER) due to high ER load. We have used RNA sequencing and ribosome profiling to investigate holistically the transcriptional and translational response to cellular infection by murine hepatitis virus (MHV), often used as a model for the Betacoronavirus genus to which the recently emerged SARS-CoV-2 also belongs. We found the UPR to be amongst the most significantly up-regulated pathways in response to MHV infection. To confirm and extend these observations, we show experimentally the induction of all three branches of the UPR in both MHV- and SARS-CoV-2-infected cells. Over-expression of the SARS-CoV-2 ORF8 or S proteins alone is itself sufficient to induce the UPR. Remarkably, pharmacological inhibition of the UPR greatly reduced the replication of both MHV and SARS-CoV-2, revealing the importance of this pathway for successful coronavirus replication. This was particularly striking when both IRE1α and ATF6 branches of the UPR were inhibited, reducing SARS-CoV-2 virion release (~1,000-fold). Together, these data highlight the UPR as a promising antiviral target to combat coronavirus infection.

Targeting the Conserved Stem Loop 2 Motif in the SARS-CoV-2 Genome.

RNA structural elements occur in numerous single-stranded positive-sense RNA viruses. The stem-loop 2 motif (s2m) is one such element with an unusually high degree of sequence conservation, being found in the 3' untranslated region (UTR) in the genomes of many astroviruses, some picornaviruses and noroviruses, and a variety of coronaviruses, including severe acute respiratory syndrome coronavirus (SARS-CoV) and SARS-CoV-2. The evolutionary conservation and its occurrence in all viral subgenomic transcripts imply a key role for s2m in the viral infection cycle. Our findings indicate that the element, while stably folded, can nonetheless be invaded and remodeled spontaneously by antisense oligonucleotides (ASOs) that initiate pairing in exposed loops and trigger efficient sequence-specific RNA cleavage in reporter assays. ASOs also act to inhibit replication in an astrovirus replicon model system in a sequence-specific, dose-dependent manner and inhibit SARS-CoV-2 replication in cell culture. Our results thus permit us to suggest that the s2m element is readily targeted by ASOs, which show promise as antiviral agents. IMPORTANCE The highly conserved stem-loop 2 motif (s2m) is found in the genomes of many RNA viruses, including SARS-CoV-2. Our findings indicate that the s2m element can be targeted by antisense oligonucleotides. The antiviral potential of this element represents a promising start for further research into targeting conserved elements in RNA viruses.

Associations between stress, anxiety, depression, and emotional intelligence among osteopathic medical students.

Context: Stress, anxiety, and depression affect medical student populations at rates disproportionate to those of general student populations. Emotional intelligence (EI) has been suggested as a protective factor in association with psychological distress. Objective: To explore the relationships between EI and stress, anxiety, and depression among a sample of US osteopathic medical students. Methods: From February to March 2020, a convenience sample of medical students enrolled at an osteopathic medical school in the southeastern region of the United States were invited to complete a voluntary and anonymous 54-item online questionnaire that included sociodemographic items as well as validated and reliable scales assessing perceived stress, anxiety, depression, and EI. Univariate statistics were calculated to describe the participant characteristics and the study variables of interest. Pearson's product-moment correlations were used to examine relationships between EI and study variables. Three multiple regression models were fitted to examine the relationship between EI and stress, anxiety, and depression, adjusting for sociodemographic factors exhibiting significant bivariate relationships with outcome variables. Dichotomous variables were created that were indicative of positive screens for potential depressive disorder or anxiety disorder. Independent-sample t-tests were used to determine the presence of a statistically significant difference in EI scores between positive screeners for depression and anxiety and their respective counterparts; an alpha level of 0.05 was set a priori to indicate statistical significance. Results: In all, 268 medical students participated in this study, for a response rate of approximately 27%. Importantly, EI exhibited significant negative correlations with stress, anxiety, and depression (r=-0.384, p<0.001; r=-0.308, p<0.001; r=-0.286, p<0.001), respectively). Thus, high levels of stress, anxiety, and depression were observed in the sample. Significant relationships remained following covariate adjustment. Established cutoffs for anxiety and depression were used to classify positive and negative screens for these morbidities. Using these classifications, individuals screening positive for potential anxiety and depression exhibited significantly lower levels of EI than their counterparts showing subclinical symptoms (t=5.14, p<0.001 and t=3.58, p<0.001, respectively). Conclusion: Our findings support the notion that higher levels of EI may potentially lead to increased well-being, limit psychological distress, improve patient care, and facilitate an ability to thrive in the medical field. We encourage continued study on the efficacy of EI training through intervention, measurement of EI in both academic and clinical settings as an indicator of those at risk for programmatic dropout or psychological distress, and consideration of EI training as an adjunct to the educational program curriculum.

Donor oocyte recipients do not benefit from preimplantation genetic testing for aneuploidy to improve pregnancy outcomes.

STUDY QUESTION: Do donor oocyte recipients benefit from preimplantation genetic testing for aneuploidy (PGT-A)? SUMMARY ANSWER: PGT-A did not improve the likelihood of live birth for recipients of vitrified donor oocytes, but it did avoid embryo transfer in cycles with no euploid embryos. WHAT IS KNOWN ALREADY: Relative to slow freeze, oocyte vitrification has led to increased live birth from cryopreserved oocytes and has led to widespread use of this technology in donor egg IVF programs. However, oocyte cryopreservation has the potential to disrupt the meiotic spindle leading to abnormal segregation of chromosome during meiosis II and ultimately increased aneuploidy in resultant embryos. Therefore, PGT-A might have benefits in vitrified donor egg cycles. In contrast, embryos derived from young donor oocytes are expected to be predominantly euploid, and trophectoderm biopsy may have a negative effect relative to transfer without biopsy. STUDY DESIGN, SIZE, DURATION: This is a paired cohort study analyzing donor oocyte-recipient cycles with or without PGT-A performed from 2012 to 2018 at 47 US IVF centers. PARTICIPANTS/MATERIALS, SETTING, METHODS: Vitrified donor oocyte cycles were analyzed for live birth as the main outcome measure. Outcomes from donors whose oocytes were used by at least two separate recipient couples, one couple using PGT-A (study group) and one using embryos without PGT-A (control group), were compared. Generalized estimating equation models controlled for confounders and nested for individual donors contributing to both PGT-A and non-PGT-A cohorts, enabling a single donor to serve as her own control. MAIN RESULTS AND THE ROLE OF CHANCE: In total, 1291 initiated recipient cycles from 223 donors were analyzed, including 262 cycles with and 1029 without PGT-A. The median aneuploidy rate per recipient was 25%. Forty-three percent of PGT-A cycles had only euploid embryos, whereas only 12.7% of cycles had no euploid embryos. On average 1.09 embryos were transferred in the PGT-A group compared to 1.38 in the group without PGT-A (P < 0.01). Live birth occurred in 53.8% of cycles with PGT-A versus 55.8% without PGT-A (P = 0.44). Similar findings persisted in cumulative live birth from per recipient cycle. LIMITATIONS, REASONS FOR CAUTION: Pooled clinical data from 47 IVF clinics introduced PGT-A heterogeneity as genetic testing were performed using different embryology laboratories, PGT-A companies and testing platforms. WIDER IMPLICATIONS OF THE FINDINGS: PGT-A testing in donor oocyte-recipient cycles does not improve the chance for live birth nor decrease the risk for miscarriage in the first transfer cycle but does increase cost and time for the patient. Further studies are required to test if our findings can be applied to the young infertility patient population using autologous oocytes. STUDY FUNDING/COMPETING INTEREST(S): No external funding was used for this study. There are no conflicts of interest to declare. TRIAL REGISTRATION NUMBER: N/A.

Preparation of Cultured Cells Using High-Pressure Freezing and Freeze Substitution for Subsequent 2D or 3D Visualization in the Transmission Electron Microscope.

Transmission electron microscopy (TEM) is an invaluable technique used for imaging the ultrastructure of samples, and it is particularly useful when determining virus-host interactions at a cellular level. The environment inside a TEM is not favorable for biological material (high vacuum and high energy electrons). Also biological samples have little or no intrinsic electron contrast and rarely do they naturally exist in very thin sheets, as is required for optimum resolution in the TEM. To prepare these samples for imaging in the TEM therefore requires extensive processing which can alter the ultrastructure of the material. Here we describe a method which aims to minimize preparation artifacts by freezing the samples at high pressure to instantaneously preserve ultrastructural detail, then rapidly substituting the ice with resin to provide a firm matrix which can be cut into thin sections for imaging. Thicker sections of this material can also be imaged and reconstructed into 3D volumes using electron tomography.

Infectious Bronchitis Virus Regulates Cellular Stress Granule Signaling.

Viruses must hijack cellular translation machinery to express viral genes. In many cases, this is impeded by cellular stress responses. These stress responses result in the global inhibition of translation and the storage of stalled mRNAs, into RNA-protein aggregates called stress granules. This results in the translational silencing of the majority of mRNAs excluding those beneficial for the cell to resolve the specific stress. For example, the expression of antiviral factors is maintained during viral infection. Here we investigated stress granule regulation by Gammacoronavirus infectious bronchitis virus (IBV), which causes the economically important poultry disease, infectious bronchitis. Interestingly, we found that IBV is able to inhibit multiple cellular stress granule signaling pathways, whilst at the same time, IBV replication also results in the induction of seemingly canonical stress granules in a proportion of infected cells. Moreover, IBV infection uncouples translational repression and stress granule formation and both processes are independent of eIF2α phosphorylation. These results provide novel insights into how IBV modulates cellular translation and antiviral stress signaling.

Association between prescription opioid misuse and dimensions of suicidality among college students.

Suicide rates among young adults have increased in recent years. Prescription opioid misuse is not only associated with depression onset but misuse has also been reported as means to manage existing depressive symptoms. College students are at increased risk for psychological distress compared to other populations. The current cross-sectional study aimed to fill a literature gap by examining a relationship between prescription opioid misuse and 3 dimensions of suicidality among a large sample of college students (n = 889). Binomial logistic regression examined relationships between prescription opioid misuse and suicidality while adjusting for the effect of important demographic and substance use covariates. Among this sample 38.8% reported suicidal ideation, 11.6% reported making a plan to kill themselves, and 7.8% reported at least one suicide attempt in the past 12 months. Past year prescription opioid misuse was common (21.6% of participants) and significantly associated with each dimension of suicidality. Though the relationships were attenuated, past year prescription opioid misuse remained significantly associated with suicidal ideation, planning, and attempts following covariate adjustment. At a local level, University health promotion specialists should give particular consideration to individuals exhibiting prescription opioid misuse as this may serve as an indicator of underlying psychological distress and possible suicidality.

The Porcine Deltacoronavirus Replication Organelle Comprises Double-Membrane Vesicles and Zippered Endoplasmic Reticulum with Double-Membrane Spherules.

Porcine deltacoronavirus (PDCoV) was first identified in Hong Kong in 2012 from samples taken from pigs in 2009. PDCoV was subsequently identified in the USA in 2014 in pigs with a history of severe diarrhea. The virus has now been detected in pigs in several countries around the world. Following the development of tissue culture adapted strains of PDCoV, it is now possible to address questions regarding virus-host cell interactions for this genera of coronavirus. Here, we presented a detailed study of PDCoV-induced replication organelles. All positive-strand RNA viruses induce the rearrangement of cellular membranes during virus replication to support viral RNA synthesis, forming the replication organelle. Replication organelles for the Alpha-, Beta-, and Gammacoronavirus genera have been characterized. All coronavirus genera induced the formation of double-membrane vesicles (DMVs). In addition, Alpha- and Betacoronaviruses induce the formation of convoluted membranes, while Gammacoronaviruses induce the formation of zippered endoplasmic reticulum (ER) with tethered double-membrane spherules. However, the structures induced by Deltacoronaviruses, particularly the presence of convoluted membranes or double-membrane spherules, are unknown. Initially, the dynamics of PDCoV strain OH-FD22 replication were assessed with the onset of viral RNA synthesis, protein synthesis, and progeny particle release determined. Subsequently, virus-induced membrane rearrangements were identified in infected cells by electron microscopy. As has been observed for all other coronaviruses studied to date, PDCoV replication was found to induce the formation of double-membrane vesicles. Significantly, however, PDCoV replication was also found to induce the formation of regions of zippered endoplasmic reticulum, small associated tethered vesicles, and double-membrane spherules. These structures strongly resemble the replication organelle induced by avian Gammacoronavirus infectious bronchitis virus.

Infectious Bronchitis Virus Nonstructural Protein 4 Alone Induces Membrane Pairing.

Positive-strand RNA viruses, such as coronaviruses, induce cellular membrane rearrangements during replication to form replication organelles allowing for efficient viral RNA synthesis. Infectious bronchitis virus (IBV), a pathogenic avian Gammacoronavirus of significant importance to the global poultry industry, has been shown to induce the formation of double membrane vesicles (DMVs), zippered endoplasmic reticulum (zER) and tethered vesicles, known as spherules. These membrane rearrangements are virally induced; however, it remains unclear which viral proteins are responsible. In this study, membrane rearrangements induced when expressing viral non-structural proteins (nsps) from two different strains of IBV were compared. Three non-structural transmembrane proteins, nsp3, nsp4, and nsp6, were expressed in cells singularly or in combination and the effects on cellular membranes investigated using electron microscopy and electron tomography. In contrast to previously studied coronaviruses, IBV nsp4 alone is necessary and sufficient to induce membrane pairing; however, expression of the transmembrane proteins together was not sufficient to fully recapitulate DMVs. This indicates that although nsp4 is able to singularly induce membrane pairing, further viral or host factors are required in order to fully assemble IBV replicative structures. This study highlights further differences in the mechanism of membrane rearrangements between members of the coronavirus family.

From the field to the lab - An European view on the global spread of PEDV.

Porcine Epidemic Diarrhea Virus (PEDV) is a member of the genus Alphacoronavirus, in the family Coronaviridae, of the Nidovirales order and outbreaks of porcine epidemic diarrhoea (PED) were first recorded in England in the 1970s. Intriguingly the virus has since successfully made its way around the globe, while seemingly becoming extinct in parts of Europe before its recent return from Northern America. In this review we are re-evaluating the spread of PEDV, its biology and are looking at lessons learnt from both failure and success. While a new analysis of PEDV genomes demonstrates a wider heterogeneity of PEDV than previously anticipated with at least five rather than two genotypes, biological features of the virus and its replication also point towards credible control strategies to limit the impact of this re-emerging virus.

Feline Calicivirus Infection Disrupts Assembly of Cytoplasmic Stress Granules and Induces G3BP1 Cleavage.

UNLABELLED: In response to stress such as virus infection, cells can stall translation by storing mRNAs away in cellular compartments called stress granules (SGs). This defense mechanism favors cell survival by limiting the use of energy and nutrients until the stress is resolved. In some cases it may also block viral propagation as viruses are dependent on the host cell resources to produce viral proteins. Human norovirus is a member of the Caliciviridae family responsible for gastroenteritis outbreaks worldwide. Previous studies on caliciviruses have identified mechanisms by which they can usurp the host translational machinery, using the viral protein genome-linked VPg, or regulate host protein synthesis through the mitogen-activated protein kinase (MAPK) pathway. Here, we examined the effect of feline calicivirus (FCV) infection on SG accumulation. We show that FCV infection impairs the assembly of SGs despite an increased phosphorylation of eukaryotic initiation factor eIF2α, a hallmark of stress pathway activation. Furthermore, SGs did not accumulate in FCV-infected cells that were stressed with arsenite or hydrogen peroxide. FCV infection resulted in the cleavage of the SG-nucleating protein Ras-GTPase activating SH3 domain-binding protein (G3BP1), which is mediated by the viral 3C-like proteinase NS6(Pro) Using mutational analysis, we identified the FCV-induced cleavage site within G3BP1, which differs from the poliovirus 3C proteinase cleavage site previously identified. Finally, we showed that NS6(Pro)-mediated G3BP1 cleavage impairs SG assembly. In contrast, murine norovirus (MNV) infection did not impact arsenite-induced SG assembly or G3BP1 integrity, suggesting that related caliciviruses have distinct effects on the stress response pathway. IMPORTANCE: Human noroviruses are a major cause of viral gastroenteritis, and it is important to understand how they interact with the infected host cell. Feline calicivirus (FCV) and murine norovirus (MNV) are used as models to understand norovirus biology. Recent studies have suggested that the assembly of stress granules is central in orchestrating stress and antiviral responses to restrict viral replication. Overall, our study provides the first insight on how caliciviruses impair stress granule assembly by targeting the nucleating factor G3BP1 via the viral proteinase NS6(Pro) This work provides new insights into host-pathogen interactions that regulate stress pathways during FCV infection.