Is IFN expression by NK cells a hallmark of severe COVID-19?

Natural Killer cells (NK) are crucial in host defense against viruses. There are many unanswered questions about the immune system in COVID-19, especially the mechanisms that contribute to the development of mild or severe forms of the disease. Although NK cells may have an essential role in the pathogenesis of COVID-19, the mechanisms involved in this process are not yet fully elucidated. Here, we demonstrate that CD3-CD56+ NK cells frequency in the volunteers who recovered from mild COVID-19 (Mild CoV) presented a significant increase compared to the healthy control (HC) and individuals recovering from severe COVID-19 (Severe CoV) groups. Furthermore, distinct IFN profiles in recovered COVID-19 patients with mild or severe clinical forms of the disease were observed in the total NK cells (CD3-CD56+). In the first group, NK cells express increased levels of IFN-α compared to the severe CoV, while higher production of IFN-γ in severe CoV was found. Moreover, NK cells in mild CoV express more cytolytic granules depicted by granzyme B and perforin. Compared to HC, PBMCs from mild CoV presented higher Ki-67 and TIM-3 production after Pool CoV-2 and Pool Spike CoV-2 peptides stimulus. In addition, non-stimulated PBMCs in the mild CoV group had higher NK TIM-3+ frequency than severe CoV. In the mild CoV group, Pool Spike CoV-2 and Pool CoV-2 peptides stimuli elicited higher granzyme B and perforin coexpression and IFN-α production by PBMCs. However, in severe CoV, Pool Spike CoV-2 reduced the coexpression of granzyme B, perforin, and CD107a suggesting a decrease in the cytotoxic activity of NK cells. Therefore, our study shows that NK cells may have a crucial role in COVID-19 with the involvement of IFN-α and cytotoxic properties that aid in developing qualified immune responses. Furthermore, the data suggest that higher amounts of IFN-γ may be linked to the severity of this disease.

Downregulation of CD73 on CD4+ T cells from patients with chronic Chikungunya infection.

Chikungunya is an important mosquito-borne disease caused by the arthritogenic chikungunya virus, characterized by sporadic outbreaks all around the world. Although CD4+ T cells seem to have an important role in the pathogenesis of chikungunya, the mechanisms involved in this process are not yet fully elucidated. The ectoenzymes CD39 and CD73, also expressed by CD4 T lymphocytes, are involved in the hydrolysis of pro-inflammatory extracellular ATP and generation of immunosuppressive adenosine and seem to be modulated in some arthritogenic pathologies. However, their involvement in Chikungunya disease is unclear. Thus, using flow cytometry, we investigated peripheral CD4+ T cells from patients with acute and chronic chikungunya to assess the expression of ectonucleotidases CD39 and CD73 and coinhibitory receptors and production of cytokine and cytolytic granules. Patients in the acute phase displayed increased levels of PD-1, CTLA-4, IL-10, and IFN-γ compared to healthy individuals and patients in the chronic phase. Moreover, during chronic Chikungunya, analyses of Mean Fluorescent Intensity (MFI) demonstrated a reduced density of LAP, Perforin and Granzyme B compared to the healthy control. Finally, reduced levels of the ectoenzymes CD39 and CD73 expression was found during the chronic phase suggesting a possible modulation of extracellular ATP and adenosine by CD4+ T cells that may be involved in the persistence of arthritogenic symptoms.

Human CD8 T-cell activation in acute and chronic chikungunya infection.

There is a need for more detailed elucidation of T-cell immunity in chikungunya infection. CD8 T cells are one of main actors against viruses. Here, we analysed CD8+ T lymphocytes from patients in the acute and chronic phases of chikungunya disease (CHIKD). Our results demonstrate that CD8+ T cells expressed higher ex vivo granzyme B, perforin and CD107A expression in patients in the acute phase of CHIKD compared with healthy individuals and higher ex vivo expression of CD69, interleukin-17A, interleukin-10 and CD95 ligand, and co-expression of CD95/CD95 ligand. These results elucidate the importance of these lymphocytes, demonstrating immune mechanisms mediated in human chikungunya infection.

Molecular and clinical epidemiological surveillance of dengue virus in Paraíba, Northeast Brazil

ABSTRACT INTRODUCTION: Despite being the most prevalent arboviral disease worldwide, dengue has been neglected lately. However, recent epidemics of arboviruses such as Zika and chikungunya in locations throughout the world have alerted health authorities to these diseases. This study evaluated the incidence pattern of dengue, its clinical characteristics, and co-circulation of serotypes from 2007 to 2015 in Paraiba State, Northeast Brazil. METHODS: Data on dengue cases from 2007 to 2015 were extracted from clinical reports of the National System for Notifiable Diseases [Sistema Nacional de Agravos de Notificação (SINAN)] of Brazil provided by the Paraiba Health Department. Reverse transcription polymerase chain reaction (RT-PCR) assays for dengue serotypes were carried out on plasma samples obtained from patients with suspected dengue. The data were analysed using descriptive statistics. RESULTS: According to clinical features, dengue fever [n = 39,083 (70.2%)] and dengue without warning signs [n = 15,365 (27.7%)] were the most common classifications of dengue. On RT-PCR, DENV 1 was the most commonly identified serotype (80.5%) in all years studied. Co-circulation of all four DENV serotypes was observed in 2013 and 2014. Furthermore, we observed an increase in dengue notifications in 2015, possibly due to the rise of Zika and chikungunya. CONCLUSIONS: Our findings support the hypothesis that co-circulation of the four DENV serotypes may be a reason for the increased prevalence of severe forms of dengue in the years studied. This study may contribute to directing research, health policy, and financial resources toward reducing poorly controlled epidemic diseases.

Methanolic extracts from brown seaweeds Dictyota cilliolata and Dictyota menstrualis induce apoptosis in human cervical adenocarcinoma HeLa cells.

Carcinoma of the uterine cervix is the second most common female tumor worldwide, surpassed only by breast cancer. Natural products from seaweeds evidencing apoptotic activity have attracted a great deal of attention as new leads for alternative and complementary preventive or therapeutic anticancer agents. Here, methanol extracts from 13 species of tropical seaweeds (Rhodophytas, Phaeophyta and Chlorophyta) collected from the Northeast of Brazil were assessed as apoptosis-inducing agents on human cervical adenocarcinoma (HeLa). All extracts showed different levels of cytotoxicity against HeLa cells; the most potent were obtained from the brown alga Dictyota cilliolata (MEDC) and Dictyota menstrualis (MEDM). In addition, MEDC and MEDM also inhibits SiHa (cervix carcinoma) cell proliferation. Studies with these two extracts using flow cytometry and fluorescence microscopy showed that HeLa cells exposed to MEDM and MEDC exhibit morphological and biochemical changes that characterize apoptosis as shown by loss of cell viability, chromatin condensation, phosphatidylserine externalization, and sub-G1 cell cycle phase accumulation, also MEDC induces cell cycle arrest in cell cycle phase S. Moreover, the activation of caspases 3 and 9 by these extracts suggests a mitochondria-dependent apoptosis route. However, other routes cannot be ruled out. Together, these results point out the methanol extracts of the brown algae D. mentrualis and D. cilliolata as potential sources of molecules with antitumor activity.

Low-level laser therapy promotes proliferation and invasion of oral squamous cell carcinoma cells.

Low-level laser therapy (LLLT) has been shown to be effective in promoting cell proliferation. There is speculation that the biostimulatory effect of LLLT causes undesirable enhancement of tumor growth in neoplastic diseases since malignant cells are more susceptible to proliferative stimuli. This study evaluated the effects of LLLT on proliferation, invasion, and expression of cyclin D1, E-cadherin, ß-catenin, and MMP-9 in a tongue squamous carcinoma cell line (SCC25). Cells were irradiated with a diode laser (660 nm) using two energy densities (0.5 and 1.0 J/cm(2)). The proliferative potential was assessed by cell growth curves and cell cycle analysis, whereas the invasion of cells was evaluated using a Matrigel cell invasion assay. Expression of cyclin D1, E-cadherin, ß-catenin, and MMP-9 was analyzed by immunofluorescence and flow cytometry and associated with the biological activities studied. LLLT induced significantly the proliferation of SCC25 cells at 1.0 J/cm(2), which was accomplished by an increase in the expression of cyclin D1 and nuclear ß-catenin. At 1.0 J/cm(2), LLLT significantly reduced E-cadherin and induced MMP-9 expression, promoting SCC25 invasion. The results of this study demonstrated that LLLT exerts a stimulatory effect on proliferation and invasion of SCC25 cells, which was associated with alterations on expression of proteins studied.