Molecular Determinants of Severe Acute Respiratory Syndrome Coronavirus Pathogenesis and Virulence in Young and Aged Mouse Models of Human Disease

SARS coronavirus (SARS-CoV) causes severe acute respiratory tract disease characterized by diffuse alveolar damage and hyaline membrane formation. This pathology often progresses to acute respiratory distress (such as acute respiratory distress syndrome [ARDS]) and atypical pneumonia in humans, with characteristic age-related mortality rates approaching 50% or more in immunosenescent populations. The molecular basis for the extreme virulence of SARS-CoV remains elusive. Since young and aged (1-year-old) mice do not develop severe clinical disease following infection with wild-type SARS-CoV, a mouse-adapted strain of SARS-CoV (called MA15) was developed and was shown to cause lethal infection in these animals. To understand the genetic contributions to the increased pathogenesis of MA15 in rodents, we used reverse genetics and evaluated the virulence of panels of derivative viruses encoding various combinations of mouse-adapted mutations. We found that mutations in the viral spike (S) glycoprotein and, to a much less rigorous extent, in the nsp9 nonstructural protein, were primarily associated with the acquisition of virulence in young animals. The mutations in S likely increase recognition of the mouse angiotensin-converting enzyme 2 (ACE2) receptor not only in MA15 but also in two additional, independently isolated mouse-adapted SARS-CoVs. In contrast to the findings for young animals, mutations to revert to the wild-type sequence in nsp9 and the S glycoprotein were not sufficient to significantly attenuate the virus compared to other combinations of mouse-adapted mutations in 12-month-old mice. This panel of SARS-CoVs provides novel reagents that we have used to further our understanding of differential, age-related pathogenic mechanisms in mouse models of human disease

Kate 2012

Each year, kate seeks to: explore ideas about normative gender, sex, and sexuality work against oppression and hierarchies of power in any and all forms serve as a voice for race and gender equity as well as queer positivity encourage the silent to speak and feel less afraid build a zine and community that we care about and trusthttps://digitalcommons.otterbein.edu/kate/1007/thumbnail.jp

Activation and inhibition of rat neuronal nicotinic receptors by ABT-418

1. ABT-418 appeared to function as a relatively broad spectrum activator of neuronal nicotinic receptors, expressed in Xenopus oocytes, with little cross reactivity to the mammalian muscle receptor subtype. However, the relative potencies of ABT-418 at the various subtypes differed from those acetylcholine (ACh). For example, ACh was most potent at α3β2 (EC(50)≈30 μM) and least potent at α2β2 (EC(50)≈500 μM). ABT-418 was most potent at α4β2 and α2β2 (EC(50)≈6 μM and 11 μM, respectively) and least potent at α3β4 (EC(50)≈188 μM). 2. In addition to activating neuronal receptors, ABT-418 exhibited complex properties, including the inhibition of ACh responses. 3. The current responses elicited by relatively high concentrations of ABT-418 on the α4β2 receptor subtype were protracted beyond the application interval. The coapplication of ABT-418 with either of the use-dependent inhibitors bis(1,2,2,6,6-tetramethyl-4-pipendimyl)sebacate (BTMPS) or tetramethyl-pipenidine (TMP) eliminated the late protracted phase of the currents with only small effects on the initial activation phase. When the reversible inhibitor TMP was washed from the bath, the previously inhibited late current reappeared, suggesting that the observed mixed agonist-antagonist effects of ABT-418 and (±)-epibatidine on α(4)β(2) were due to a concentration-dependent noncompetitive inhibition, an effect similar to that obtained for (−)-nicotine. 4. The inhibition of α4β2 receptors by ABT-418 was voltage-dependent. When high concentrations of ABT-418 were applied under depolarizing conditions, additional late currents could be observed under conditions which suggested that a build up of ABT-418 in an unstirred layer over the surface of the oocyte was occurring. This may have been due to the dissociation of the drug from channel blocking sites on the receptors themselves, or alternatively, from the plasma membrane of the cells