Characterization of Influenza A(H1N1)pdm09 Viruses Isolated in the 2018-2019 and 2019-2020 Influenza Seasons in Japan.

The influenza A(H1N1)pdm09 virus that emerged in 2009 causes seasonal epidemic worldwide. The virus acquired several amino acid substitutions that were responsible for antigenic drift until the 2018-2019 influenza season. Viruses possessing mutations in the NA and PA proteins that cause reduced susceptibility to NA inhibitors and baloxavir marboxil, respectively, have been detected after antiviral treatment, albeit infrequently. Here, we analyzed HA, NA, and PA sequences derived from A(H1N1)pdm09 viruses that were isolated during the 2018-2019 and 2019-2020 influenza seasons in Japan. We found that A(H1N1)pdm09 viruses possessing the D187A and Q189E substitutions in HA emerged and dominated during the 2019-2020 season; these substitutions in the antigenic site Sb, a high potency neutralizing antibody-eliciting site for humans, changed the antigenicity of A(H1N1)pdm09 viruses. Furthermore, we found that isolates possessing the N156K substitution, which was predicted to affect the antigenicity of A(H1N1)pdm09 virus at the laboratory level, were detected at a frequency of 1.0% in the 2018-2019 season but 10.1% in the 2019-2020 season. These findings indicate that two kinds of antigenically drifted viruses-N156K and D187A/Q189E viruses-co-circulated during the 2019-2020 influenza season in Japan.

P-selectin expression, but not GPIIb/IIIa activation, is enhanced in the inflammatory stage of Takayasu's arteritis.

BACKGROUND: Inflammation and thrombosis are closely related processes, but the association between disease activity and thrombogenicity in Takayasu's arteritis (TA) is poorly understood. To investigate the link between platelet activation and disease activity, flow cytometric analyses of platelet P-selectin and activated GPIIb/IIIa expression were performed in patients with TA. METHODS AND RESULTS: Twenty-two patients with TA, classified into active (Group A, n = 9) and inactive (Group I, n = 13) according to blood-derived inflammatory markers, and 14 healthy age- and gender-matched controls (Group C) were studied. Compared with Group C, the mean fluorescence intensity of P-selectin in response to 0.1-10 micromol/L of ADP was significantly upregulated in Group A, but not in Group I. No differences in platelet GPIIb/IIIa expression in stimulated platelets were seen among the 3 groups. Standard platelet aggregation studies revealed that disease activity did not influence platelet aggregation by ADP. CONCLUSIONS: P-selectin expression, but not activated GPIIb/IIIa, is enhanced in ADP-activated platelets from patients in the inflammatory stage of TA. P-selectin may play a significant role in the inflammatory and thrombotic responses associated with intractable TA, presumably by inducing platelet-leukocyte interactions.

Perindopril augments ecto-ATP diphosphohydrolase activity and enhances endothelial anti-platelet function in human umbilical vein endothelial cells.

OBJECTIVES: Recent clinical trials have demonstrated that angiotensin-converting enzyme inhibitors (ACEIs) reduce thrombotic events by unknown mechanisms in patients with atherosclerotic cardiovascular diseases. DESIGN: We studied the in-vitro effects of perindopril, an ACEI, on the ability of human umbilical vein endothelial cells (HUVEC) to inhibit platelet aggregation. METHODS: Platelet aggregation in the presence of HUVEC and endothelial surface expression and activities of ecto-ATP diphosphohydrolase (ecto-ADPase), CD39, were determined. The capability of HUVEC to release prostacyclin and nitric oxide (NO) was also investigated. RESULTS: Perindoprilat (an active metabolite of perindopril) significantly enhanced the surface expression and activities of ecto-ADPase and prostacyclin release, resulting in enhancement of ability to inhibit platelet aggregation by HUVEC. These effects of perindoprilat were also observed in HUVEC activated by tumour necrosis factor (TNF)-alpha, which increased the expression of intracellular adhesion molecule-1 (ICAM-1), CD54, and, despite up-regulation of prostacyclin release, attenuated endothelial anti-platelet properties by decreasing ecto-ADPase activity. Perindoprilat partially restored this capability, but failed to reduce enhanced expression of ICAM-1. By contrast, the role of NO as a platelet inhibitor appeared minimal in HUVEC. Candesartan, an angiotensin II receptor (AT(1)) blocker, did not affect endothelial anti-platelet property. CONCLUSIONS: Perindoprilat was found to augment endothelial capability to inhibit platelet aggregation by increasing ecto-ADPase activity and prostacyclin release in HUVEC. This beneficial effect of perindoprilat appeared to be preserved in the activated cells exposed to TNF-alpha, although no evidence was found to support that it could reverse the inflammation process induced by cytokines.

Acute vigorous exercise primes enhanced NO release in human platelets.

Activation of platelets by acute vigorous exercise has been demonstrated by various parameters, including an increase in agonist-induced platelet [Ca2+]i levels. However, direct evidence is lacking regarding how acute exercise affects platelet-derived NO. Twenty-three healthy male non-smokers (21-59 years) underwent a symptom-limited treadmill exercise test. Washed platelets were prepared from blood samples obtained before and immediately after exercise. All subjects completed at least Bruce stage 2 and were each negative for ischemia. With a low dose (2 microg/ml) of collagen, NO release from washed platelets, detected by the NO-selective microelectrode, was significantly increased after exercise (pmols/10(8) platelets, before: 0.64+/-0.11, after: 1.03+/-0.18; P<0.005) without changes in aggregation ability. This enhanced NO release was accompanied by increased platelet [Ca2+]i levels (before: 232+/-25, after: 296+/-37; P<0.01). With a high dose (5 or 10 microg/ml) of collagen, NO release and aggregation were both modestly, but significantly, enhanced after exercise. The exercise-induced enhancement of platelet NO release in response to collagen was also suggested by increase in platelet cyclic guanosine monophosphate accumulation and augmenting effect of N(G)-monomethyl-L-arginine on platelet aggregation. In summary, acute strenuous exercise primes enhanced NO release and may play a protective role against exercise-induced activation of platelets in normal subjects.