Pokeweed antiviral protein depurinates the sarcin/ricin loop of the rRNA prior to binding of aminoacyl-tRNA to the ribosomal A-site

Ribosome-inactivating proteins, such as the pokeweed antiviral protein (PAP), inhibit translation by depurinating the conserved sarcin/ricin loop of the large ribosomal RNA. Depurinated ribosomes are unable to bind elongation factor 2, and, thus, the translocation step of the elongation cycle is inhibited. Though the consequences of depurination are well characterized, the ribosome conformation required for depurination to take place has not been described. In this report, we correlate biochemical and genetic data to conclude that pokeweed antiviral protein depurinates the sarcin/ricin loop when the A-site of the ribosomal peptidyl-transferase center is unoccupied. We show that prior incubation of ribosomes with puromycin, an analog of the 3′-terminus of aminoacyl-tRNA, inhibits both binding and depurination by PAP in a concentration-dependent manner. Expression of PAP in the yeast strain mak8-1 results in little depurination unless the cells are lysed, a process that would promote loss of aminoacyl-tRNA from the ribosome. The mak8-1 strain is known to exhibit a higher affinity for aminoacyl-tRNA compared with wild-type cells, and therefore, its ribosomes are more resistant to PAP in vivo. These data contribute to the mechanism of action of pokeweed antiviral protein; specifically, they have uncovered the ribosomal conformation required for depurination that leads to subsequent translation inhibition

Abstract P104: Incidence, Characteristics and Outcomes of Large Vessel Stroke in Covid-19: An International Multicenter Study

Background: While there are reports of acute ischemic stroke (AIS) in COVID-19 patients, the overall incidence of acute ischemic stroke and clinical characteristics of large vessel occlusion in such patient remains to be established. Methods: A retrospective, international multicenter study of large vessel occlusion (LVO) was undertaken from March 1 to May 1, 2020 at 12 stroke centers from 4 countries. Detailed data were collected on consecutive LVOs in hospitalized patients with laboratory-confirmed severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and the incidence of AIS/LVO was measured. Among patients who underwent mechanical thrombectomy, stroke outcomes along with COVID-19 symptoms were reported. Results: Out of a total of 6698 COVID-19 patients admitted to 10 stroke centers, the incidence of stroke was found to be 1.3% (range 0.6-2.6%). The median age of patients who presented with LVO was 51 years (range 27-87) and in the US centers, African Americans comprised 28% of all patients. Ten patients (16 %) were less than 50 years of age with no significant risk factors for LVOs the vast majority. Among the LVOs eligible for MT, the average time to presentation from symptom onset to presentation was 9.3 hours. Successful revascularization was achieved in 81% of patients and the intracranial hemorrhage rate was 14% with no symptomatic hemorrhages. Twenty-one (50%) patients were either discharged to home or to acute rehabilitation facilities. Conclusion: LVOs was predominant in patients with AIS and COVID-19, occurring at a significantly younger age and affecting African Americans disproportionately

Incidence, Characteristics and Outcomes of Large Vessel Stroke in COVID-19 Cohort: An International Multicenter Study

Graphical Abstrac

Neutrophil-Lymphocyte Ratio Is Associated With Poor Clinical Outcome After Mechanical Thrombectomy in Stroke in Patients With COVID-19

BACKGROUND: The neutrophil-lymphocyte ratio (NLR) is emerging as an important biomarker of acute physiologic stress in a myriad of medical conditions, and is a confirmed poor prognostic indicator in COVID-19. OBJECTIVE: We sought to describe the role of NLR in predicting poor outcome in COVID-19 patients undergoing mechanical thrombectomy for acute ischemic stroke. METHODS: We analyzed NLR in COVID-19 patients with large vessel occlusion (LVO) strokes enrolled into an international 12-center retrospective study of laboratory-confirmed COVID-19, consecutively admitted between March 1, 2020 and May 1, 2020. Increased NLR was defined as ≥7.2. Logistic regression models were generated. RESULTS: Incidence of LVO stroke was 38/6698 (.57%). Mean age of patients was 62 years (range 27-87), and mortality rate was 30%. Age, sex, and ethnicity were not predictive of mortality. Elevated NLR and poor vessel recanalization (Thrombolysis in Cerebral Infarction (TICI) score of 1 or 2a) synergistically predicted poor outcome (likelihood ratio 11.65, p  =  .003). Patients with NLR \u3e 7.2 were 6.8 times more likely to die (OR 6.8, CI95% 1.2-38.6, p  =  .03) and almost 8 times more likely to require prolonged invasive mechanical ventilation (OR 7.8, CI95% 1.2-52.4, p  =  .03). In a multivariate analysis, NLR \u3e 7.2 predicted poor outcome even when controlling for the effect of low TICI score on poor outcome (NLR p  =  .043, TICI p  =  .070). CONCLUSIONS: We show elevated NLR in LVO patients with COVID-19 portends significantly worse outcomes and increased mortality regardless of recanalization status. Severe neuro-inflammatory stress response related to COVID-19 may negate the potential benefits of successful thrombectomy