The influenza A virus host shutoff factor PA-X is rapidly turned over in a strain-specific manner.

The influenza A endoribonuclease PA-X regulates virulence and transmission of the virus by reducing host gene expression and thus regulating immune responses to influenza A virus. Despite this key function in viral biology, the levels of PA-X protein remain markedly low during infection, and previous results suggest that these low levels are not solely the result of regulation of the level of translation and RNA stability. How PA-X is regulated post-translationally remains unknown. We now report that the PA-X protein is rapidly turned over. PA-X from multiple viral strains are short-lived, although the half-life of PA-X ranges from ∼30 minutes to ∼3.5 hours depending on the strain. Moreover, sequences in the variable PA-X C-terminal domain are primarily responsible for regulating PA-X half-life, although the N-terminal domain also accounts for some differences among strains. Interestingly, we find that the PA-X from the 2009 pandemic H1N1 strain has a longer half-life compared to the other variants we tested. This PA-X isoform has been reported to have a higher host shutoff activity, suggesting a role for protein turnover in regulating PA-X activity. Collectively, this study reveals a novel regulatory mechanism of PA-X protein levels that may impact host shutoff activity during influenza A virus infection.IMPORTANCE The PA-X protein from influenza A virus reduces host immune responses to infection through suppressing host gene expression, including genes encoding the antiviral response. Thus, it plays a central role in influenza A virus biology. Despite its key function, PA-X was only discovered in 2012 and much remains to be learned including how PA-X activity is regulated to promote optimal levels of viral infection. In this study, we reveal that PA-X protein levels are very low likely because of rapid turnover. We show that instability is a conserved property among PA-X variants from different strains of influenza A virus, but that the half-lives of PA-X variants differ. Moreover, the longer half-life of PA-X from the 2009 pandemic H1N1 strain correlates with its reported higher activity. Therefore, PA-X stability may be a way to regulate its activity and may contribute to the differential virulence of influenza A virus strains.

The ongoing impact of COVID-19 on asthma and pediatric emergency health-seeking behavior in the Bronx, an epicenter.

BACKGROUND: The Bronx has the highest prevalence of asthma in the United States (US), and was also an early COVID-19 epicenter, making it a unique study location. Worldwide reports describe significant declines in pediatric emergency department (PED) visits during COVID-19. The ongoing impact of COVID-19 on all PED presentations, including asthma, at an early epicenter has not been studied beyond the pandemic peak and into the early phases of state re-opening. OBJECTIVES: To compare PED health-seeking behaviors and clinical characteristics during the 2020 pandemic and subsequent initial New York State (NYS) phased re-opening to the same period in 2019. METHODS: Retrospective chart review of children <21 years utilizing the PED at a high-volume quaternary children's hospital in The Bronx, NY from March 15th 2020 - July 6th 2020 (pandemic cohort) and the same interval in 2019 (comparison cohort). Visits were assigned to pre-determined diagnostic categories. Demographic and clinical data were compared. RESULTS: 19,981 visits were included. Visits declined by 66% during 2020. Proportions of asthma visits (2% vs. 7%, p < 0.0001) and minor medical problems (61% vs. 67%, p < 0.0001) had significant declines in the pandemic cohort, while major medical problems (13% vs. 8%, p < 0.0001), appendicitis (1% vs. 0.4%, p < 0.0001) and other surgical complaints (1% vs. 0.5%, p < 0.0001) had proportional increases in the pandemic cohort. No significant proportional changes were noted among psychosocial and trauma groups between the two cohorts. CONCLUSION: The pandemic cohort experienced a substantial decrease in PED volume, but an increase in acuity and admission rates, which was sustained through the NYS phase-II re-opening. Despite being located in an asthma hub, the incidence of asthma-related PED visits declined appreciably in the pandemic cohort. Future studies examining the effects of indoor allergens in isolation on pediatric asthma are warranted.

A 21st Century Problem: Cannabis Toxicity in a 13-Month-Old Child.

BACKGROUND: Cannabis is one of the most abused drugs worldwide, with more than 20 million users in the United States (US). As access to cannabis products increases with expanding US legislation and decriminalization of marijuana, emergency physicians must be adept in recognizing unintentional cannabis toxicity in young children, which can range from altered mental status to encephalopathy and coma. CASE REPORT: We report the case of a 13-month-old female presenting with self-limiting altered mental status and lethargy, with a subsequent diagnosis of tetrahydrocannabinol exposure on confirmatory urine gas chromatography-mass spectrometry. WHY SHOULD AN EMERGENCY PHYSICIAN BE AWARE OF THIS?: Considering caretakers rarely report possible cannabis exposure, history-taking must review caretakers' medicinal and recreational drug exposures to prevent inadvertently missing the diagnosis. In the young child with altered mental status, prompt urine screening for cannabinoid detection can prevent further invasive and costly diagnostic investigations, such as brain imaging and lumbar puncture.

The Influenza A Virus Endoribonuclease PA-X Usurps Host mRNA Processing Machinery to Limit Host Gene Expression.

Many viruses shut off host gene expression to inhibit antiviral responses. Viral proteins and host proteins required for viral replication are typically spared in this process, but the mechanisms of target selectivity during host shutoff remain poorly understood. Using transcriptome-wide and targeted reporter experiments, we demonstrate that the influenza A virus endoribonuclease PA-X usurps RNA splicing to selectively target host RNAs for destruction. Proximity-labeling proteomics reveals that PA-X interacts with cellular RNA processing proteins, some of which are partially required for host shutoff. Thus, PA-X taps into host nuclear pre-mRNA processing mechanisms to destroy nascent mRNAs shortly after their synthesis. This mechanism sets PA-X apart from other viral host shutoff proteins that target actively translating mRNAs in the cytoplasm. Our study reveals a unique mechanism of host shutoff that helps us understand how influenza viruses suppress host gene expression.

Host Shutoff in Influenza A Virus: Many Means to an End.

Influenza A virus carries few of its own proteins, but uses them effectively to take control of the infected cells and avoid immune responses. Over the years, host shutoff, the widespread down-regulation of host gene expression, has emerged as a key process that contributes to cellular takeover in infected cells. Interestingly, multiple mechanisms of host shutoff have been described in influenza A virus, involving changes in translation, RNA synthesis and stability. Several viral proteins, notably the non-structural protein NS1, the RNA-dependent RNA polymerase and the endoribonuclease PA-X have been implicated in host shutoff. This multitude of host shutoff mechanisms indicates that host shutoff is an important component of the influenza A virus replication cycle. Here we review the various mechanisms of host shutoff in influenza A virus and the evidence that they contribute to immune evasion and/or viral replication. We also discuss what the purpose of having multiple mechanisms may be.

It Is Not Always Sepsis: Fatal Tachypnea in a Newborn.

Coarctation of the aorta (CoA) is a congenital cardiac malformation that is well understood. Despite being well characterized, CoA is a commonly missed congenital heart disease (CHD) during the newborn period. We report a full-term nine-day-old male who presented to the pediatric emergency department (ED) with isolated tachypnea. After an initial sepsis workup, subsequent investigations revealed critical CoA. Because the primary workup focused on sepsis, there was a significant delay in prostaglandin E1 (PGE1) initiation. This case illustrates the importance of early CoA recognition and timely initiation of PGE1 in newborns who present with suspected sepsis along with tachypnea.

The educational value of emergency department teaching: it is about time.

There is a paucity of research on the quality and quantity of clinical teaching in the emergency department (ED) setting. While many factors impact residents' perceptions of attending physicians' educational skill, the authors hypothesized that the amount of time residents spend with attending in direct teaching is a determinant of residents' perception of their shift's educational value. Researchers shadowed emergency medicine (EM) attendings during ED shifts, and recorded teaching time with each resident. Residents were surveyed on their assessment of the educational value (EV) of the shift and potential confounders, as well as the attending physician's teaching quality using the ER Scale. The study was performed in the EDs of two urban teaching hospitals affiliated with an EM residency program. Subjects were EM residents and rotators from other specialties. The main outcome measure was the regression of impact of teaching time on EV. Researchers observed 20 attendings supervising 47 residents (mean 2.35 residents per attending, range 2-3). The correlation between teaching time in minutes (mean 60.8, st.dev 25.6, range 7.6-128.1) and EV (mean 3.45 out of 5, st. dev 0.75, range 2-5) was significant (r = 0.302, r 2 = 0.091, p < 0.05). No confounders had a significant effect. The study shows a moderate correlation between the total time attendings spend directly teaching residents and the residents' perception of educational value over a single ED shift. The authors suggest that mechanisms to increase the time attending physicians spend teaching during clinical shifts may result in improved resident education.