SARS-CoV-2 and Other Respiratory Viruses: What Does Oxidative Stress Have to Do with It?

The phenomenon of oxidative stress, characterized as an imbalance in the production of reactive oxygen species and antioxidant responses, is a well-known inflammatory mechanism and constitutes an important cellular process. The relationship of viral infections, reactive species production, oxidative stress, and the antiviral response is relevant. Therefore, the aim of this review is to report studies showing how reactive oxygen species may positively or negatively affect the pathophysiology of viral infection. We focus on known respiratory viral infections, especially severe acute respiratory syndrome coronaviruses (SARS-CoVs), in an attempt to provide important information on the challenges posed by the current COVID-19 pandemic. Because antiviral therapies for severe acute respiratory syndrome coronaviruses (e.g., SARS-CoV-2) are rare, knowledge about relevant antioxidant compounds and oxidative pathways may be important for understanding viral pathogenesis and identifying possible therapeutic targets

Profile of the TNF-α response induced by extracellular and intracellular TLR activation in peripheral blood and cord blood of HIV-1-infected mothers.

<p>(A–G) PBMCs obtained from mothers (M) and cord blood (CB) of HIV-1-infected mothers (n = 15) and uninfected controls (n = 15) were stimulated or not (baseline) for 48 h with agonists of extracellular TLRs (TLR2/Pam3Cks4, TLR4/LPS, TLR5/flagellin) or intracellular TLRs (TLR3/poly I:C, TLR7/Imiquimode, TLR7/TLR8/CL097, TLR9/CpG). Cell-free supernatants were assessed for TNF-α secretion by cytometric bead array. Bars indicate the mean ± SEM. *p≤0.05, **p≤0.01, ***p≤0.001 when compared with the control group; #p≤0.05, ##p≤0.01 when compared with the respective mother. (H) TNF-α secretion –induced by CL097 from HIV-infected mothers was assessed according to the mother CD4+ T cells number, <350 cells/µL (open circles) or >350 cells/µL (closed circles). Figure represents the median. *p≤0.05 when compared with the CD4+ T cells >350 cells/µL group.</p

Marked decrease in pDC responsiveness to TLR activation in peripheral blood and CB from HIV-1-infected mothers.

<p>PBMCs from mothers (M) and cord blood (CB) of HIV-1-infected (n = 15) and uninfected controls (n = 15) were stimulated or not (baseline) for 20 h with agonists of TLR7 (Imiquimode), TLR7/TLR8 (CL097) and TLR9 (CpG). Brefeldin was added after 5 h of stimulation. Intracellular IFN-α secretion by pDCs (CD123+lin-HLA-DR+) was assessed by flow cytometry. a) Representative histograms of CD123+IFN-α+ cells upon TLR stimulation from one HIV-infected and one uninfected mother. The number in the corner represents the cell percentage. b) Data represent the mean percentage ± SEM. *p≤0.05, **p≤0.01, ***p≤0.001 when compared with the control group; +p≤0.05, ++p≤0.01, +++p≤0.001 when compared with baseline levels.</p

TLR7/TLR8 Activation Restores Defective Cytokine Secretion by Myeloid Dendritic Cells but Not by Plasmacytoid Dendritic Cells in HIV-Infected Pregnant Women and Newborns

<div><p>Mother-to-child transmission (MTCT) of HIV-1 has been significantly reduced with the use of antiretroviral therapies, resulting in an increased number of HIV-exposed uninfected infants. The consequences of HIV infection on the innate immune system of both mother-newborn are not well understood. In this study, we analyzed peripheral blood and umbilical cord blood (CB) collected from HIV-1-infected and uninfected pregnant women. We measured TNF-α, IL-10 and IFN-α secretion after the stimulation of the cells with agonists of both extracellular Toll-like receptors (TLRs) (TLR2, TLR4 and TLR5) and intracellular TLRs (TLR7, TLR7/8 and TLR9). Moreover, as an indicator of the innate immune response, we evaluated the responsiveness of myeloid dendritic cells (mDCs) and plasmacytoid DCs (pDCs) to TLRs that are associated with the antiviral response. Our results showed that peripheral blood mononuclear cells (PBMCs) from HIV-1-infected mothers and CB were defective in TNF-α production after activation by TLR2, TLR5, TLR3 and TLR7. However, the TNF-α response was preserved after TLR7/8 (CL097) stimulation, mainly in the neonatal cells. Furthermore, only CL097 activation was able to induce IL-10 and IFN-α secretion in both maternal and CB cells in the infected group. An increase in IFN-α secretion was observed in CL097-treated CB from HIV-infected mothers compared with control mothers. The effectiveness of CL097 stimulation was confirmed by observation of similar mRNA levels of interferon regulatory factor-7 (IRF-7), IFN-α and TNF-α in PBMCs of both groups. The function of both mDCs and pDCs was markedly compromised in the HIV-infected group, and although TLR7/TLR8 activation overcame the impairment in TNF-α secretion by mDCs, such stimulation was unable to reverse the dysfunctional type I IFN response by pDCs in the HIV-infected samples. Our findings highlight the dysfunction of innate immunity in HIV-infected mother-newborn pairs. The activation of the TLR7/8 pathway could function as an adjuvant to improve maternal-neonatal innate immunity.</p></div

Improved TNF-α secretion by mDCs in peripheral blood and CB of HIV-1-infected mothers after stimulation with TLR7/8 agonists.

<p>PBMCs from mothers (M) and cord blood (CB) of HIV-1-infected (n = 15) and uninfected controls (n = 15) were stimulated or not (baseline) for 20 h with agonists of TLR7 (Imiquimode), TLR7/TLR8 (CL097) and TLR9 (CpG). Brefeldin was added after 5 h of stimulation. Intracellular TNF-α secretion by mDCs (CD11c+lin-HLA-DR+) was assessed by flow cytometry. a) representative histograms of mDCs (CD11c+TNF-α+) upon TLR stimulation. The number in the corner represents the cell percentage. b) Data represent the mean percentage ± SEM. *p≤0.05, **p≤0.01, ***p≤0.001 when compared with the control group; +p≤0.05, ++p≤0.01 when compared with baseline levels.</p

Demographic characteristics of mothers.

<p>Median (range).</p

Profile of IRF-7, IFN-α and TNF-α gene expression induced by TLR7/8 and TLR9 activation.

<p>PBMCs from mothers (M, left side column) and cord blood (CB, right side column) of HIV-1-infected (n = 6–10, closed circles) and uninfected controls (n = 4–11, open circles) were stimulated or not (baseline) for 4 h with agonists of TLR7/TLR8 (CL097) and TLR9 (CpG). The expression of IRF-7, IFN-α and TNF-α were assessed by real–time PCR, and relative expression was normalized to GAPDH mRNA levels. *p≤0.05, **p≤0.01 when compared with the control group.</p

Enhanced IL-10 secretion by TLR7/8 ligand stimulation in HIV-1-infected mothers and newborns.

<p>(A–G) PBMCs from mothers (M) and cord blood (CB) of HIV-1-infected (n = 15) and uninfected controls (n = 15) were stimulated or not (baseline) for 48 h with agonists for TLR2/Pam3Cks4, TLR4/LPS, TLR5/flagellin, TLR3/poly I:C, TLR7/Imiquimode, TLR7/TLR8/CL097 and TLR9/CpG. IL-10 secretion was determined by cytometric bead array. Bars indicate the mean ± SEM. *p≤0.05, **p≤0.01, *** p≤0.001 when compared with the control group; ++p≤0.01 when compared with baseline levels. (H) IL-10 secretion –induced by CL097 from HIV-infected mothers was assessed according to the mother CD4+ T cells number, <350 cells/µL (open circles) or >350 cells/µL (closed circles). Figure represents the median. *p≤0.05 when compared with the CD4+ T cells >350 cells/µL group.</p

Obesity Induces an Impaired Placental Antiviral Immune Response in Pregnant Women Infected with Zika Virus

Obesity is increasing in incidence worldwide, especially in women, which can affect the outcome of pregnancy. During this period, viral infections represent a risk to the mother, the placental unit, and the fetus. The Zika virus (ZIKV) outbreak in Brazil has been the cause of congenital Zika syndrome (CZS), with devastating consequences such as microcephaly in newborns. Herein, we analyzed the impact of maternal overweight/obesity on the antiviral factors&rsquo; expression in the placental tissue of Zika-infected mothers. We accessed placentas from women with and without obesity from 34 public health units (S&atilde;o Paulo) and from Zika-infected mothers with and without obesity from the Clinical Cohort Study of ZIKV pregnant women (Rio de Janeiro, Brazil). We first verified that obesity, without infection, did not alter the constitutive transcriptional expression of antiviral factors or IFN type I/III expression. Interestingly, obesity, when associated with ZIKV infection, showed a decreased transcriptional expression of RIG-I and IFIH1 (MDA-5 protein precursor gene). At the protein level, we also verified a decreased RIG-I and IRF-3 expression in the decidual placenta from the Zika-infected obese group, regardless of microcephaly. This finding shows, for the first time, that obesity associated with ZIKV infection leads to an impaired type I IFN downstream signaling pathway in the maternal&ndash;fetal interface

Platelet-Based Biomarkers for Diagnosis and Prognosis in COVID-19 Patients

Coronavirus disease 2019 (COVID-19) caused millions of deaths worldwide. COVID-19’s clinical manifestations range from no symptoms to a severe acute respiratory syndrome, which can result in multiple organ failure, sepsis, and death. Severe COVID-19 patients develop pulmonary and extrapulmonary infections, with a hypercoagulable state. Several inflammatory or coagulatory biomarkers are currently used with predictive values for COVID-19 severity and prognosis. In this manuscript, we investigate if a combination of coagulatory and inflammatory biomarkers could provide a better biomarker with predictive value for COVID-19 patients, being able to distinguish between patients that would develop a moderate or severe COVID-19 and predict the disease outcome. We investigated 306 patients with COVID-19, confirmed by severe acute respiratory syndrome coronavirus 2 RNA detected in the nasopharyngeal swab, and retrospectively analyzed the laboratory data from the first day of hospitalization. In our cohort, biomarkers such as neutrophil count and neutrophil-to-lymphocyte ratio from the day of hospitalization could predict if the patient would need to be transferred to the intensive care unit but failed to identify the patients´ outcomes. The ratio between platelets and inflammatory markers such as creatinine, C-reactive protein, and urea levels is associated with patient outcomes. Finally, the platelet/neutrophil-to-lymphocyte ratio on the first day of hospitalization can be used with predictive value as a novel severity and lethality biomarker in COVID-19. These new biomarkers with predictive value could be used routinely to stratify the risk in COVID-19 patients since the first day of hospitalization