IgG targeting distinct seasonal coronavirus- conserved SARS-CoV-2 spike subdomains correlates with differential COVID-19 disease outcomes.

Despite SARS-CoV-2 being a "novel" virus, early detection of anti-spike IgG in severe COVID-19 patients may be caused by the amplification of humoral memory responses against seasonal coronaviruses. Here, we examine this phenomenon by characterizing anti-spike IgG responses in non-hospitalized convalescent individuals across a spectrum of COVID-19 severity. We observe that disease severity positively correlates with anti-spike IgG levels, IgG cross-reactivity against other betacoronaviruses (ß-CoVs), and FcγR activation. Analysis of IgG targeting ß-CoV-conserved and non-conserved immunodominant epitopes within the SARS-CoV-2 spike protein revealed epitope-specific relationships: IgG targeting the conserved heptad repeat (HR) 2 region significantly correlates with milder disease, while targeting the conserved S2'FP region correlates with more severe disease. Furthermore, a lower HR2-to-S2'FP IgG-binding ratio correlates with greater disease severity, with ICU-hospitalized COVID-19 patients showing the lowest HR2/S2'FP ratios. These findings suggest that HR2/S2'FP IgG profiles may predict disease severity and offer insight into protective versus deleterious humoral recall responses.

Sustained Antibody-Dependent NK Cell Functions in Mild COVID-19 Outpatients During Convalescence.

The coronavirus disease 2019 (COVID19) pandemic has left researchers scrambling to identify the humoral immune correlates of protection from COVID-19. To date, the antibody mediated correlates of virus neutralization have been extensively studied. However, the extent that non-neutralizing functions contribute to anti-viral responses are ill defined. In this study, we profiled the anti-spike antibody subtype/subclass responses, along with neutralization and antibody-dependent natural killer cell functions in 83 blood samples collected between 4 and 201 days post-symptoms onset from a cohort of COVID-19 outpatients. We observed heterogeneous humoral responses against the acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike protein. Overall, anti-spike profiles were characterized by a rapid rise of IgA and sustained IgG titers. In addition, strong antibody-mediated natural killer effector responses correlated with milder disease and being female. While higher neutralization profiles were observed in males along with increased severity. These results give an insight into the underlying function of antibodies beyond neutralization and suggest that antibody-mediated natural killer cell activity is a key function of the humoral response against the SARS-CoV-2 spike protein.

Cytokine Profiles and Antibody Response Associated to Choclo Orthohantavirus Infection.

Background: New World Hantaviruses (NWHs) are the etiological agent underlying hantavirus cardiopulmonary syndrome (HCPS), a severe respiratory disease with high mortality rates in humans. In Panama, infections with Choclo Orthohantavirus (CHOV) cause a much milder illness characterized by higher seroprevalence and lower mortality rates. To date, the cytokine profiles and antibody responses associated with this milder form of HCPS have not been defined. Therefore, in this study, we examined immune serological profiles associated with CHOV infections. Methods: For this retrospective study, sera from fifteen individuals with acute CHOV-induced HCPS, were analyzed alongside sera from fifteen convalescent phase individuals and thirty-three asymptomatic, CHOV-seropositive individuals. Cytokine profiles were analyzed by multiplex immunoassay. Antibody subclasses, binding, and neutralization against CHOV-glycoprotein (CHOV-GP) were evaluated by ELISA, and flow cytometry. Results: High titers of IFNγ, IL-4, IL-8, and IL-10 serum cytokines were found in the acute individuals. Elevated IL-4 serum levels were found in convalescent and asymptomatic seropositive individuals. High titers of IgG1 subclass were observed across the three cohorts analyzed. Neutralizing antibody response against CHOV-GP was detectable in few acute individuals but was strong in both convalescent and asymptomatic seropositive individuals. Conclusion: A Th1/Th2 cytokine signature is characteristic during acute mild HCPS caused by CHOV infection. High expression of Th2 and IL-8 cytokines are correlated with clinical parameters in acute mild HCPS. In addition, a strong IL-4 signature is associated with different cohorts, including asymptomatic individuals. Furthermore, asymptomatic individuals presented high titers of neutralizing antibodies.

Differential CD4 T Regulatory Cell Phenotype Induced by Andes Hantavirus Glycoprotein.

Hantavirus cardiopulmonary syndrome (HCPS) caused by Andes orthohantavirus (ANDV) in South America is a public health threat due to the significant rate of mortality and the lack of a specific treatment. Interestingly, the virus does not produce cytopathic effect, thereby the strong antiviral immune response is suspected to contribute to pathogenesis, hence is important to understand the balance between protective and harmfully immunity. CD4+ T regulatory cells (Treg) are essential to control an exacerbated immune response. In human ANDV infection, little is known about CD4+ Treg cells, which may be involved in control immunopathology associated to the infection. In this report, we characterize the phenotype of memory CD4+ Tregs in a HCPS survivor's cohort. Based on the expression of CXCR3, CCR4, and CCR6, we identified different Th-like Treg populations in ANDV survival's PBMCs. In addition, the effect of ANDV-glycoprotein virus like particles (VLP) was determined. We demonstrated that memory CD4+ Treg from HCPS present a specific phenotype, showing higher frequency of PD-1 compared to healthy donors (HD). In addition, it was observed a decrease in the frequency of Th1-like memory CD4+ Treg in HCPS, important to highlight that this signature could be preserved even years after resolution of infection. Moreover, to gain insight in the mechanism involved, we evaluated whether ANDV-glycoprotein (GP) VLP could modulate CD4+ Treg. Interestingly, ANDV-GP VLP induced a decrease in the frequency of CXCR3 (Th1-like) and an increase in CCR4 (Th2-like) memory CD4+ Treg in both HD and HCPS PBMCs, indicating that ANDV-GP could specifically act over CXCR3 and CCR4 in CD4+ Treg. This report contributes to the study of human CD4+ Treg cells in ANDV infection.

Insights on early mutational events in SARS-CoV-2 virus reveal founder effects across geographical regions.

Here we aim to describe early mutational events across samples from publicly available SARS-CoV-2 sequences from the sequence read archive and GenBank repositories. Up until 27 March 2020, we downloaded 50 illumina datasets, mostly from China, USA (WA State) and Australia (VIC). A total of 30 datasets (60%) contain at least a single founder mutation and most of the variants are missense (over 63%). Five-point mutations with clonal (founder) effect were found in USA next-generation sequencing samples. Sequencing samples from North America in GenBank (22 April 2020) present this signature with up to 39% allele frequencies among samples (n = 1,359). Australian variant signatures were more diverse than USA samples, but still, clonal events were found in these samples. Mutations in the helicase, encoded by the ORF1ab gene in SARS-CoV-2 were predominant, among others, suggesting that these regions are actively evolving. Finally, we firmly urge that primer sets for diagnosis be carefully designed, since rapidly occurring variants would affect the performance of the reverse transcribed quantitative PCR (RT-qPCR) based viral testing.

ß-catenin aggregation in models of ALS motor neurons: GSK3ß inhibition effect and neuronal differentiation.

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease characterized by motor neuron death. A 20% of familial ALS cases are associated with mutations in the gene coding for superoxide dismutase 1 (SOD1). The accumulation of abnormal aggregates of different proteins is a common feature in motor neurons of patients and transgenic ALS mice models, which are thought to contribute to disease pathogenesis. Developmental morphogens, such as the Wnt family, regulate numerous features of neuronal physiology in the adult brain and have been implicated in neurodegeneration. ß-catenin is a central mediator of both, Wnt signaling activity and cell-cell interactions. We previously reported that the expression of mutant SOD1 in the NSC34 motor neuron cell line decreases basal Wnt pathway activity, which correlates with cytosolic ß-catenin accumulation and impaired neuronal differentiation. In this work, we aimed a deeper characterization of ß-catenin distribution in models of ALS motor neurons. We observed extensive accumulation of ß-catenin supramolecular structures in motor neuron somas of pre-symptomatic mutant SOD1 mice. In cell-cell appositional zones of NSC34 cells expressing mutant SOD1, ß-catenin displays a reduced co-distribution with E-cadherin accompanied by an increased association with the gap junction protein Connexin-43; these findings correlate with impaired intercellular adhesion and exacerbated cell coupling. Remarkably, pharmacological inhibition of the glycogen synthase kinase-3ß (GSK3ß) in both NSC34 cell lines reverted both, ß-catenin aggregation and the adverse effects of mutant SOD1 expression on neuronal differentiation. Our findings suggest that early defects in ß-catenin distribution could be an underlying factor affecting the onset of neurodegeneration in familial ALS.

DISC1 promotes translation maintenance during sodium arsenite-induced oxidative stress.

Variation in Disrupted-in-Schizophrenia 1 (DISC1) increases the risk for neurodegenerative diseases, schizophrenia, and other mental disorders. However, the functions of DISC1 associated with the development of these diseases remain unclear. DISC1 has been reported to inhibit Akt/mTORC1 signaling, a major regulator of translation, and recent studies indicate that DISC1 could exert a direct role in translational regulation. Here, we present evidence of a novel role of DISC1 in the maintenance of protein synthesis during oxidative stress. In order to investigate DISC1 function independently of Akt/mTORC1, we used Tsc2-/- cells, where mTORC1 activation is independent of Akt. DISC1 knockdown enhanced inhibition of protein synthesis in cells treated with sodium arsenite (SA), an oxidative agent used for studying stress granules (SGs) dynamics and translational control. N-acetyl-cysteine inhibited the effect of DISC1, suggesting that DISC1 affects translation in response to oxidative stress. DISC1 decreased SGs number in SA-treated cells, but resided outside SGs and maintained protein synthesis independently of a proper SG nucleation. DISC1-dependent stimulation of translation in SA-treated cells was supported by its interaction with eIF3h, a component of the canonical translation initiation machinery. Consistent with a role in the homeostatic maintenance of translation, DISC1 knockdown or overexpression decreased cell viability after SA exposure. Our data suggest that DISC1 is a relevant component of the cellular response to stress, maintaining certain levels of translation and preserving cell integrity. This novel function of DISC1 might be involved in its association with pathologies affecting tissues frequently exposed to oxidative stress.

Rapamycin requires AMPK activity and p27 expression for promoting autophagy-dependent Tsc2-null cell survival.

Tuberous sclerosis complex (TSC) disease results from inactivation of the TSC1 or TSC2 gene, and is characterized by benign tumors in several organs. Because TSC tumorigenesis correlates with hyperactivation of mTORC1, current therapies focus on mTORC1 inhibition with rapamycin or its analogs. Rapamycin-induced tumor shrinkage has been reported, but tumor recurrence occurs on withdrawal from rapamycin. Autophagy has been associated with development of TSC tumors and with tumor cell survival during rapamycin treatment. mTORC1 and AMPK directly inhibit and activate autophagy, respectively. AMPK is hyperactivated in TSC cells and tumors, and drives cytoplasmic sequestration of the cell-cycle inhibitor p27KIP (p27). Whether AMPK and p27 are involved in rapamycin-induced autophagy and survival of TSC cells remain unexplored. Here, we show that inhibition of AMPK by compound C or by shRNA-mediated depletion of LKB1 reduces activation of autophagy by rapamycin in Tsc2-null cells. Similarly, shRNA-mediated depletion of p27 inhibited rapamycin-induced autophagy. In support of p27 lying downstream of AMPK on the activation of autophagy in Tsc2-null cells, a p27 mutant that preferentially localizes in the cytosol recovered the effect of rapamycin on autophagy in both p27- and LKB1-depleted cells, but a nuclear p27 mutant was inactive. Finally, we show that p27-dependent activation of autophagy is involved in Tsc2-null cell survival under rapamycin treatment. These results indicate that an AMPK/p27 axis is promoting a survival mechanism that could explain in part the relapse of TSC tumors treated with rapamycin, exposing new avenues for designing more efficient treatments for TSC patients.

Rheb signaling and tumorigenesis: mTORC1 and new horizons.

Rheb is a conserved small GTPase that belongs to the Ras superfamily, and is mainly involved in activation of cell growth through stimulation of mTORC1 activity. Because deregulation of the Rheb/mTORC1 signaling is associated with proliferative disorders and cancer, inhibition of mTORC1 has been therapeutically approached. Although this therapy has proven antitumor activity, its efficacy is not as expected. Here, we will review the main work on the identification of the role of Rheb in cell growth, and on the relevance of Rheb in proliferative disorders, including cancer. We will also review the Rheb functions that could explain tumor resistance to therapies with mTORC1 inhibitors, and will mainly focus our discussion on mTORC1-independent Rheb functions that could also be implicated in cancer cell survival and tumorigenesis. The current progress on the understanding of the noncanonical Rheb functions prompts future studies to establish their relevance in cancer and in the context of current cancer therapies.