The TIGIT+ T regulatory cells subset associates with nosocomial infection and fatal outcome in COVID-19 patients under mechanical ventilation.

The TIGIT+FOXP3+Treg subset (TIGIT+Tregs) exerts robust suppressive activity on cellular immunity and predisposes septic individuals to opportunistic infection. We hypothesized that TIGIT+Tregs could play an important role in intensifying the COVID-19 severity and hampering the defense against nosocomial infections during hospitalization. Herein we aimed to verify the association between the levels of the TIGIT+Tregs with the mechanical ventilation requirement, fatal outcome, and bacteremia during hospitalization. TIGIT+Tregs were immunophenotyped by flow cytometry from the peripheral blood of 72 unvaccinated hospitalized COVID-19 patients at admission from May 29th to August 6th, 2020. The patients were stratified during hospitalization according to their mechanical ventilation requirement and fatal outcome. COVID-19 resulted in a high prevalence of the TIGIT+Tregs at admission, which progressively increased in patients with mechanical ventilation needs and fatal outcomes. The prevalence of TIGIT+Tregs positively correlated with poor pulmonary function and higher plasma levels of LDH, HMGB1, FGL2, and TNF. The non-survivors presented higher plasma levels of IL-33, HMGB1, FGL2, IL-10, IL-6, and 5.54 times more bacteremia than survivors. Conclusions: The expansion of the TIGIT+Tregs in COVID-19 patients was associated with inflammation, lung dysfunction, bacteremia, and fatal outcome.

Breastfeeding by chikungunya virus-infected dams confers resistance to challenge in the offspring.

Vertical transmission of Chikungunya virus (CHIKV) has been reported in humans, but the transmission routes have not been completely understood, and experimental animal models are needed to enable detailed investigation of the transmission and pathogenesis of congenital infections. The intertwining of immune response and virus components at the gestation/breastfeeding interfaces between mother and fetus/newborn may have effects during the offspring development. An experimental model of CHIKV was established by infecting pregnant BALB/c female mice that enabled confirmation that dams inoculated up to the 10th gestational day transmit CHIKV transplacentally to approximately 8.4% of the fetuses, resulting in severe teratogenic effects. CHIKV neutralizing antibodies were detected in sera from adult mice born to healthy females and breastfed by CHIKV-infected dams, while no neutralization was detected in sera from animals born to CHIKV-infected dams. Moreover, adult mice born to healthy dams and cross-fostered for breastfeeding by CHIKV-infected dams were resistant to challenge with CHIKV on the 90th day after birth. The animals also had reduced viral loads in brain and spleen as compared to controls. There was expression of fluorescent CHIKV non-structural protein, and detection of viral RNA by RT-PCR in breast tissue from infected dams. CHIKV RNA and proteins were also detected in breast milk retrieved from the stomachs of recently fed newborns. The experimental results were also complemented by the finding of CHIKV RNA in 6% of colostrum samples from healthy lactating women in a CHIKV-endemic area. Breastfeeding induces immune protection to challenge with CHIKV in mice.

Gasdermin-D activation by SARS-CoV-2 triggers NET and mediate COVID-19 immunopathology.

BACKGROUND: The release of neutrophil extracellular traps (NETs) is associated with inflammation, coagulopathy, and organ damage found in severe cases of COVID-19. However, the molecular mechanisms underlying the release of NETs in COVID-19 remain unclear. OBJECTIVES: We aim to investigate the role of the Gasdermin-D (GSDMD) pathway on NETs release and the development of organ damage during COVID-19. METHODS: We performed a single-cell transcriptome analysis in public data of bronchoalveolar lavage. Then, we enrolled 63 hospitalized patients with moderate and severe COVID-19. We analyze in blood and lung tissue samples the expression of GSDMD, presence of NETs, and signaling pathways upstreaming. Furthermore, we analyzed the treatment with disulfiram in a mouse model of SARS-CoV-2 infection. RESULTS: We found that the SARS-CoV-2 virus directly activates the pore-forming protein GSDMD that triggers NET production and organ damage in COVID-19. Single-cell transcriptome analysis revealed that the expression of GSDMD and inflammasome-related genes were increased in COVID-19 patients. High expression of active GSDMD associated with NETs structures was found in the lung tissue of COVID-19 patients. Furthermore, we showed that activation of GSDMD in neutrophils requires active caspase1/4 and live SARS-CoV-2, which infects neutrophils. In a mouse model of SARS-CoV-2 infection, the treatment with disulfiram inhibited NETs release and reduced organ damage. CONCLUSION: These results demonstrated that GSDMD-dependent NETosis plays a critical role in COVID-19 immunopathology and suggests GSDMD as a novel potential target for improving the COVID-19 therapeutic strategy.

High-Dose Convalescent Plasma for Treatment of Severe COVID-19.

To assess whether high-dose coronavirus disease (COVID-19) convalescent plasma (CCP) transfusion may benefit patients with severe COVID-19, we conducted a multicenter randomized trial in Brazil. Patients with severe COVID-19 who were within 10 days of initial symptom onset were eligible. Patients in the CCP group received 3 daily doses of CCP (600 mL/d) in addition to standard treatment; control patients received standard treatment only. Primary outcomes were death rates at days 30 and 60 of study randomization. Secondary outcomes were ventilator-free days and hospital-free days. We enrolled 107 patients: 36 CCP and 71 control. At day 30, death rates were 22% for CCP and 25% for the control group; at day 60, rates were 31% for CCP and 35% for control. Needs for invasive mechanical ventilation and durations of hospital stay were similar between groups. We conclude that high-dose CCP transfused within 10 days of symptom onset provided no benefit for patients with severe COVID-19.

A class II MHC-targeted vaccine elicits immunity against SARS-CoV-2 and its variants.

The pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has resulted in over 100 million infections and millions of deaths. Effective vaccines remain the best hope of curtailing SARS-CoV-2 transmission, morbidity, and mortality. The vaccines in current use require cold storage and sophisticated manufacturing capacity, which complicates their distribution, especially in less developed countries. We report the development of a candidate SARS-CoV-2 vaccine that is purely protein based and directly targets antigen-presenting cells. It consists of the SARS-CoV-2 Spike receptor-binding domain (SpikeRBD) fused to an alpaca-derived nanobody that recognizes class II major histocompatibility complex antigens (VHHMHCII). This vaccine elicits robust humoral and cellular immunity against SARS-CoV-2 and its variants. Both young and aged mice immunized with two doses of VHHMHCII-SpikeRBD elicit high-titer binding and neutralizing antibodies. Immunization also induces strong cellular immunity, including a robust CD8 T cell response. VHHMHCII-SpikeRBD is stable for at least 7 d at room temperature and can be lyophilized without loss of efficacy.

Human Respiratory Syncytial Virus Infection in a Human T Cell Line Is Hampered at Multiple Steps.

Human respiratory syncytial virus (HRSV) is the most frequent cause of severe respiratory disease in children. The main targets of HRSV infection are epithelial cells of the respiratory tract, and the great majority of the studies regarding HRSV infection are done in respiratory cells. Recently, the interest on respiratory virus infection of lymphoid cells has been growing, but details of the interaction of HRSV with lymphoid cells remain unknown. Therefore, this study was done to assess the relationship of HRSV with A3.01 cells, a human CD4+ T cell line. Using flow cytometry and fluorescent focus assay, we found that A3.01 cells are susceptible but virtually not permissive to HRSV infection. Dequenching experiments revealed that the fusion process of HRSV in A3.01 cells was nearly abolished in comparison to HEp-2 cells, an epithelial cell lineage. Quantification of viral RNA by RT-qPCR showed that the replication of HRSV in A3.01 cells was considerably reduced. Western blot and quantitative flow cytometry analyses demonstrated that the production of HRSV proteins in A3.01 was significantly lower than in HEp-2 cells. Additionally, using fluorescence in situ hybridization, we found that the inclusion body-associated granules (IBAGs) were almost absent in HRSV inclusion bodies in A3.01 cells. We also assessed the intracellular trafficking of HRSV proteins and found that HRSV proteins colocalized partially with the secretory pathway in A3.01 cells, but these HRSV proteins and viral filaments were present only scarcely at the plasma membrane. HRSV infection of A3.01 CD4+ T cells is virtually unproductive as compared to HEp-2 cells, as a result of defects at several steps of the viral cycle: Fusion, genome replication, formation of inclusion bodies, recruitment of cellular proteins, virus assembly, and budding.

SARS-CoV-2-triggered neutrophil extracellular traps mediate COVID-19 pathology.

Severe COVID-19 patients develop acute respiratory distress syndrome that may progress to cytokine storm syndrome, organ dysfunction, and death. Considering that neutrophil extracellular traps (NETs) have been described as important mediators of tissue damage in inflammatory diseases, we investigated whether NETs would be involved in COVID-19 pathophysiology. A cohort of 32 hospitalized patients with a confirmed diagnosis of COVID-19 and healthy controls were enrolled. The concentration of NETs was augmented in plasma, tracheal aspirate, and lung autopsies tissues from COVID-19 patients, and their neutrophils released higher levels of NETs. Notably, we found that viable SARS-CoV-2 can directly induce the release of NETs by healthy neutrophils. Mechanistically, NETs triggered by SARS-CoV-2 depend on angiotensin-converting enzyme 2, serine protease, virus replication, and PAD-4. Finally, NETs released by SARS-CoV-2-activated neutrophils promote lung epithelial cell death in vitro. These results unravel a possible detrimental role of NETs in the pathophysiology of COVID-19. Therefore, the inhibition of NETs represents a potential therapeutic target for COVID-19.

Natural infection of Neotropical bats with hantavirus in Brazil.

Bats (Order: Chiroptera) harbor a high diversity of emerging pathogens presumably because their ability to fly and social behavior favor the maintenance, evolution, and dissemination of these pathogens. Until 2012, there was only one report of the presence of Hantavirus in bats. Historically, it was thought that these viruses were harbored primarily by rodent and insectivore small mammals. Recently, new species of hantaviruses have been identified in bats from Africa and Asia continents expanding the potential reservoirs and range of these viruses. To assess the potential of Neotropical bats as hosts for hantaviruses and its transmission dynamics in nature, we tested 53 bats for active hantaviral infection from specimens collected in Southeastern Brazil. Part of the hantaviral S segment was amplified from the frugivorous Carollia perspicillata and the common vampire bat Desmodus rotundus. DNA sequencing showed high similarity with the genome of Araraquara orthohantavirus (ARQV), which belongs to one of the more lethal hantavirus clades (Andes orthohantavirus). ARQV-like infection was detected in the blood, urine, and organs of D. rotundus. Therefore, we describe a systemic infection in Neotropical bats by a human pathogenic Hantavirus. We also propose here a schematic transmission dynamics of hantavirus in the study region. Our results give insights to new, under-appreciated questions that need to be addressed in future studies to clarify hantavirus transmission in nature and avoid hantavirus outbreaks.

Development of New Modular Genetic Tools for Engineering the Halophilic Archaeon Halobacterium salinarum.

Our ability to genetically manipulate living organisms is usually constrained by the efficiency of the genetic tools available for the system of interest. In this report, we present the design, construction and characterization of a set of four new modular vectors, the pHsal series, for engineering Halobacterium salinarum, a model halophilic archaeon widely used in systems biology studies. The pHsal shuttle vectors are organized in four modules: (i) the E. coli's specific part, containing a ColE1 origin of replication and an ampicillin resistance marker, (ii) the resistance marker and (iii) the replication origin, which are specific to H. salinarum and (iv) the cargo, which will carry a sequence of interest cloned in a multiple cloning site, flanked by universal M13 primers. Each module was constructed using only minimal functional elements that were sequence edited to eliminate redundant restriction sites useful for cloning. This optimization process allowed the construction of vectors with reduced sizes compared to currently available platforms and expanded multiple cloning sites. Additionally, the strong constitutive promoter of the fer2 gene was sequence optimized and incorporated into the platform to allow high-level expression of heterologous genes in H. salinarum. The system also includes a new minimal suicide vector for the generation of knockouts and/or the incorporation of chromosomal tags, as well as a vector for promoter probing using a GFP gene as reporter. This new set of optimized vectors should strongly facilitate the engineering of H. salinarum and similar strategies could be implemented for other archaea.