Dysfunctional phenotype of systemic and pulmonary regulatory T cells associate with lethal COVID-19 cases.

Severe cases of COVID-19 present hyperinflammatory condition that can be fatal. Little is known about the role of regulatory responses in SARS-CoV-2 infection. In this study, we evaluated the phenotype of regulatory T cells in the blood (peripheral blood mononuclear cell) and the lungs (broncho-alveolar) of adult patients with severe COVID-19 under invasive mechanical ventilation. Our results show important dynamic variation on Treg cells phenotype during COVID-19 with changes in number and functional parameters from the day of intubation (Day 1 of intensive care unit admission) to Day 7. We observed that compared with surviving patients, non-survivors presented lower numbers of Treg cells in the blood. In addition, lung Tregs of non-survivors also displayed higher PD1 and lower FOXP3 expressions suggesting dysfunctional phenotype. Further signs of Treg dysregulation were observed in non-survivors such as limited production of IL-10 in the lungs and higher production of IL-17A in the blood and in the lungs, which were associated with increased PD1 expression. These findings were also associated with lower pulmonary levels of Treg-stimulating factors like TNF and IL-2. Tregs in the blood and lungs are profoundly dysfunctional in non-surviving COVID-19 patients.

Monitoring the Establishment of VOC Gamma in Minas Gerais, Brazil: A Retrospective Epidemiological and Genomic Surveillance Study.

Since its first identification in Brazil, the variant of concern (VOC) Gamma has been associated with increased infection and transmission rates, hospitalizations, and deaths. Minas Gerais (MG), the second-largest populated Brazilian state with more than 20 million inhabitants, observed a peak of cases and deaths in March-April 2021. We conducted a surveillance study in 1240 COVID-19-positive samples from 305 municipalities distributed across MG's 28 Regional Health Units (RHU) between 1 March to 27 April 2021. The most common variant was the VOC Gamma (71.2%), followed by the variant of interest (VOI) zeta (12.4%) and VOC alpha (9.6%). Although the predominance of Gamma was found in most of the RHUs, clusters of Zeta and Alpha variants were observed. One Alpha-clustered RHU has a history of high human mobility from countries with Alpha predominance. Other less frequent lineages, such as P.4, P.5, and P.7, were also identified. With our genomic characterization approach, we estimated the introduction of Gamma on 7 January 2021, at RHU Belo Horizonte. Differences in mortality between the Zeta, Gamma and Alpha variants were not observed. We reinforce the importance of vaccination programs to prevent severe cases and deaths during transmission peaks.

SARS-CoV-2 Omicron BA.1, BA.2, and XAG identification during routine surveillance on a university campus in Belo Horizonte, Brazil, 2022.

We report SARS-CoV-2 genomic surveillance results between Belo Horizonte, Brazil's third and fourth case waves. Samples were obtained through a routine university monitoring COVID-19 program from the 9th to the 22nd epidemiological weeks (March and June 2022). We identified ten samples from the BA.1 clade (BA.1, BA.1.1, and BA.1.14.1 lineages) and 45 samples from the BA.2 clade (BA.2, BA.2.56, BA.2.9, BA.2.62, BA.2.23, BA.2.81, and BA.2.10). We observed progressive replacement of the BA.1 by the BA.2 clade. Furthermore, two XAG recombinants were found in the 22nd week. Diversification of the omicron variant seems to have contributed to the resurgence of cases in Belo Horizonte, similarly to what has been reported in South Africa.

Ketamine potentiates TRPV1 receptor signaling in the peripheral nociceptive pathways.

TRPV1 is a cation channel expressed in peripheral nociceptive pathways and its activation can trigger nociception signals to the brain. Ketamine is an intravenous anesthetic routinely used for anesthesia induction and with potent analgesic activity. Despite its proven depressant action on peripheral sensory pathways, the relationship between ketamine and TRPV1 receptors is still unclear. In this study, we evaluated the effect of ketamine injected peripherally in a rat model of spontaneous pain induced by capsaicin. We also investigated the effect of ketamine on Ca2+ transients in cultured dorsal root ganglia (DRG) neurons and HEK293 cells expressing the TRPV1 receptor (HEK-TRPV1 cells). Intraplantar administration of ketamine caused an unexpected increase in nocifensive behavior induced by capsaicin. Incubation of HEK-TRPV1 cells with 10 µM ketamine increased TRPV1 and PKCє phosphorylation. Ketamine potentiated capsaicin-induced Ca2+ transients in HEK-TRPV1 cells and DRG neurons. Ketamine also prevented TRPV1 receptor desensitization induced by successive applications of capsaicin. єV1-2, a PKCє inhibitor, reduced potentiation of capsaicin-induced Ca2+ transients by ketamine. Taken together, our data indicate that ketamine potentiates TRPV1 receptor sensitivity to capsaicin through a mechanism dependent on PKCє activity.

Phoneutria toxin PnTx3-5 inhibits TRPV1 channel with antinociceptive action in an orofacial pain model.

Capsaicin, an agonist of TRPV1, evokes intracellular [Ca2+] transients and glutamate release from perfused trigeminal ganglion. The spider toxin PnTx3-5, native or recombinant is more potent than the selective TRPV1 blocker SB-366791 with IC50 of 47 ±â€¯0.18 nM, 45 ±â€¯1.18 nM and 390 ±â€¯5.1 nM in the same experimental conditions. PnTx3-5 is thus more potent than the selective TRPV1 blocker SB-366791. PnTx3-5 (40 nM) and SB-366791 (3 µM) also inhibited the capsaicin-induced increase in intracellular Ca2+ in HEK293 cells transfected with TRPV1 by 75 ±â€¯16% and 84 ±â€¯3.2%, respectively. In HEK293 cells transfected with TRPA1, cinnamaldehyde (30 µM) generated an increase in intracellular Ca2+ that was blocked by the TRPA1 antagonist HC-030031 (10 µM, 89% inhibition), but not by PnTx3-5 (40 nM), indicating selectivity of the toxin for TRPV1. In whole-cell patch-clamp experiments on HEK293 cells transfected with TRPV1, capsaicin (10 µM) generated inward currents that were blocked by SB-366791 and by both native and recombinant PnTx3-5 by 47 ±â€¯1.4%; 54 ±â€¯7.8% and 56 ±â€¯9.0%, respectively. Intradermal injection of capsaicin into the rat left vibrissa induced nociceptive behavior that was blocked by pre-injection with either SB-366791 (3 nmol/site i.d., 83.3 ±â€¯7.2% inhibition) or PnTx3-5 (100 fmol/site, 89 ±â€¯8.4% inhibition). We conclude that both native and recombinant PnTx3-5 are potent TRPV1 receptor antagonists with antinociceptive action on pain behavior evoked by capsaicin.