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Innate Lymphoid Cells (ILCs) are immune cells typically found on mucosal surfaces and in secondary lymphoid organs where they regulate the immune response to pathogens. Despite their key role in the immune response, there are still fundamental gaps in our understanding of ILCs. Here we report a human ILC population present in the follicles of tonsils and lymph nodes termed follicular regulatory ILCs (ILCFR) that to our knowledge has not been previously identified. ILCFR have a distinct phenotype and transcriptional program when compared to other defined ILCs. Surprisingly, ILCFR inhibit the ability of follicular helper T (Tfh) cells to provide B cell help. The localization of ILCFR to the germinal centers suggests these cells may interfere with germinal center B cell (GC-B) and germinal center Tfh cell (GC-Tfh) interactions through the production of transforming growth factor beta (TGF-β. Intriguingly, under conditions of impaired GC-Tfh-GC-B cell interactions, such as human immunodeficiency virus (HIV) infection, the frequency of these cells is increased. Overall, we predict a role for ILCFR in regulating GC-Tfh-GC-B cell interactions and propose they expand in chronic inflammatory conditions. Margaret O'Connor et al. report a new Innate Lymphoid Cell population in human tonsils and lymph nodes that inhibit the functional interaction of follicular helper T cells and germinal center B cells. They show that this cell population is expanded under chronic HIV infection and results in decreased antibody production, suggesting a potential role for these cells in diseases with dysregulated immune responses. [ABSTRACT FROM AUTHOR]

People infected with severe acute respiratory syndrome coronavirus 2 display a wide range of illness, from asymptomatic infection to severe respiratory distress resulting in death. We measured serum biomarkers in uninfected individuals and in individuals with mild, moderate, or critical coronavirus disease 2019 (COVID-19) disease. Levels of monocyte activation (soluble CD14 and fatty acid-binding protein 4) and inflammation (tumor necrosis factor receptors 1 and 2 [TNFR1 and TNFR2]) were increased in COVID-19 individuals, regardless of disease severity. Among patients with critical disease, individuals who recovered from COVID-19 had lower levels of TNFR1 and TNFR2 at hospital admission compared to these levels in patients with critical disease who ultimately died. [ABSTRACT FROM AUTHOR]

The article presents a study that analyzed the quality of HIV-specific CD8+ T cell responses emerging in the earliest stages of acute infection and assessed whether these responses could control viral replication and HIV reservoir seeding after antiretroviral therapy initiation. Topics discussed include HIV-specific CD8+ T cell expansion in the early stages of acute HIV-1 infection and loss of cytokine secretion and survival potential ofHIV-specific CD8+T cells during acute HIV infection.

The rapid host response to virus infection is crucial for establishment of the antiviral state and for the release of pro-inflammatory mediators that coordinate the adaptive immune response. Induction of antiviral and inflammatory genes is achieved largely through recognition of viral nucleic acid motifs by pattern recognition receptors. Dengue virus (DENV) is a significant human pathogen that causes a wide spectrum of clinical symptoms, ranging from mild dengue fever to severe hemorrhagic fever and shock syndrome. The cytosolic receptors RIG-I/MDA5 as well as the membrane-bound TLR3/TLR7 localized in the endosomes are important sensors of DENV infection. The role of reactive oxygen species (ROS) in the activation of biological processes such as autophagy, necrosis, and inflammasome activation adds another layer of complexity to the regulation of immune sensing. Transcriptome analysis of DENV-infected human monocyte-derived dendritic cells (Mo-DC) revealed the activation of distinct patterns of gene transcription, with involvement of pathways including the antiviral response, the TNF superfamily and late activation of death receptor signaling. Interestingly, a dominant early gene network associated with the Nrf2-dependent antioxidant response was also identified; DENV infection induced an early production of ROS that was dependent on NADPH-oxidase, and was essential for the activation of inflammatory and antiviral programs, through NF-κB and IRF-3 transcription factors, respectively. Using a high throughput qPCR assay, we demonstrated that interfering with NADPH-oxidase inhibited DENV-induced antiviral and inflammatory responses. We also demonstrated that the antioxidant pathway controlled by the transcription factor Nrf2 is a pivotal upstream link to the regulation of DENV-induced antiviral and inflammatory responses under oxidative conditions. In conclusion, these findings demonstrate that ROS production is crucial for effective activation of pathways leading to innate immune responses against DENV infection in human Mo-DC. [ABSTRACT FROM AUTHOR]

RIG-I is a cytosolic sensor critically involved in the activation of the innate immune response to RNA virus infection. In the present study, we evaluated the inhibitory effect of a RIG-I agonist on the replication of two emerging arthropod-borne viral pathogens, dengue virus (DENV) and chikungunya virus (CHIKV), for which no therapeutic options currently exist. We demonstrate that when a low, noncytotoxic dose of an optimized 5'triphosphorylated RNA (5'pppRNA) molecule was administered, RIG-I stimulation generated a robust antiviral response against these two viruses. Strikingly, 5'pppRNA treatment before or after challenge with DENV or CHIKV provided protection against infection. In primary human monocytes and monocyte-derived dendritic cells, the RIG-I agonist blocked both primary infection and antibody-dependent enhancement of DENV infection. The protective response against DENV and CHIKV induced by 5'pppRNA was dependent on an intact RIG-I/MAVS/TBK1/IRF3 axis and was largely independent of the type I IFN response. Altogether, this in vitro analysis of the antiviral efficacy of 5'pppRNA highlights the therapeutic potential of RIG-I agonists against emerging viruses such as DENV and CHIKV. [ABSTRACT FROM AUTHOR]

Background: Central nervous system (CNS) infiltration by CD8 T cells is associated with neuroinflammation in many neurodegenerative diseases, including HIV-associated dementia. However, the role of CD8 T cells in the CNS during acute HIV infection (AHI) is unknown., Methods: We analyzed the phenotype, gene expression, T cell receptor (TCR) repertoire, and HIV specificity of CD8 T cells in cerebrospinal fluid (CSF) of a unique cohort captured during the earliest stages of AHI (n = 26), chronic (n = 23), and uninfected (n = 8)., Results: CSF CD8 T cells were elevated in AHI compared with uninfected controls. The frequency of activated CSF CD8 T cells positively correlated to CSF HIV RNA and to markers of CNS inflammation. In contrast, activated CSF CD8 T cells during chronic HIV infection were associated with markers of neurological injury and microglial activation. CSF CD8 T cells in AHI exhibited increased functional gene expression profiles associated with CD8 T cells effector function, proliferation, and TCR signaling, a unique restricted TCR Vbeta repertoire and contained HIV-specific CD8 T cells directed to unique HIV epitopes compared with the periphery., Conclusions: These results suggest that CSF CD8 T cells in AHI expanding in the CNS are functional and directed against HIV antigens. These cells could thus play a beneficial role protective of injury seen in chronic HIV infection if combination antiretroviral therapy is initiated early.

CD8 + T cells play a critical role in controlling HIV viremia and could be important in reducing HIV-infected cells in approaches to eradicate HIV. The simian immunodeficiency virus model provided the proof of concept for a CD8 + T cell-mediated reservoir clearance but showed conflicting evidence on the role of these cells to eliminate HIV-infected cells. In humans, HIV-specific CD8 + T cell responses have not been associated with a reduction of the HIV-infected cell pool in vivo. We studied HIV-specific CD8 + T cells in the RV254 cohort of individuals initiating ART in the earliest stages of acute HIV infection (AHI). We showed that the HIV-specific CD8 + T cells generated as early as AHI stages 1 and 2 before peak viremia are delayed in expanding and acquiring effector functions but are endowed with higher memory potential. In contrast, the fully differentiated HIV-specific CD8 + T cells at peak viremia in AHI stage 3 were more prone to apoptosis but were associated with a steeper viral load decrease after ART initiation. Their capacity to persist in vivo after ART initiation correlated with a lower HIV DNA reservoir. These findings demonstrate that HIV-specific CD8 + T cell magnitude and differentiation are delayed in the earliest stages of infection. These results also demonstrate that potent HIV-specific CD8 + T cells contribute to the reduction of the pool of HIV-producing cells and the HIV reservoir seeding in vivo and provide the rationale to design interventions aiming at inducing these potent responses to cure HIV infection., (Copyright © 2017, American Association for the Advancement of Science.)

Recombinant simian virus 40 (rSV40)-derived vectors are particularly useful for gene delivery to bone marrow progenitor cells and their differentiated derivatives, certain types of epithelial cells (e.g., hepatocytes), and central nervous system neurons and microglia. They integrate rapidly into cellular DNA to provide long-term gene expression in vitro and in vivo in both resting and dividing cells. Techniques used to produce, purify, and quantitate these vectors are simple, give reproducible results, and may be used to generate vectors that are deleted only for large T antigen (Tag), or for all SV40-coding sequences capable of carrying up to 5 kb of foreign DNA. Viruses are purified by centrifugation using discontinuous sucrose or cesium chloride (CsCl) gradients. Resulting vectors are replication-incompetent and contain no detectable wild-type SV40 revertants. Viruses are titered by quantitative polymerase chain reaction (qPCR), described here. qPCR measures the number of rSV40 genomes in purified viral stocks using primers specific for the rSV40, coupled with SYBR Green detection of PCR products. Sample purity is assessed using qPCR via melt (dissociation) curve analysis. The only specialized equipment necessary is a quantitative real-time PCR machine.

Recombinant simian virus 40 (rSV40)-derived vectors are particularly useful for gene delivery to bone marrow progenitor cells and their differentiated derivatives, certain types of epithelial cells (e.g., hepatocytes), and central nervous system neurons and microglia. They integrate rapidly into cellular DNA to provide long-term gene expression in vitro and in vivo in both resting and dividing cells. Here we describe a protocol for production and purification of these vectors. These procedures require only packaging cells (e.g., COS-7) and circular vector genome DNA. Amplification involves repeated infection of packaging cells with vector produced by transfection. Cotransfection is not required in any step. Viruses are purified by centrifugation using discontinuous sucrose or cesium chloride (CsCl) gradients and resulting vectors are replication-incompetent and contain no detectable wild-type SV40 revertants. These approaches are simple, give reproducible results, and may be used to generate vectors that are deleted only for large T antigen (Tag), or for all SV40-coding sequences capable of carrying up to 5 kb of foreign DNA. These vectors are best applied to long-term expression of proteins normally encoded by mammalian cells or by viruses that infect mammalian cells, or of untranslated RNAs (e.g., RNA interference). The preparative approaches described facilitate application of these vectors and allow almost any laboratory to exploit their strengths for diverse gene delivery applications.