#CD8+ regulatory T cells limit #immunopathology but impair viral clearance in #Hantaan virus #infection

 

Abstract

In hemorrhagic fever with renal syndrome (HFRS) caused by Hantaan virus (HTNV), virus-specific CD8+ T cells mediate both viral clearance and immunopathology. Here, we characterized a CD8+ regulatory T cell (Treg) subset restricted by HLA-E (and its murine ortholog Qa-1) in HFRS patients and in a murine HTNV infection model. CD8+ Tregs (CD122+Eomes+CD49dloKIR+), a subset substantially enriched for HLA-E-restricted T cells, were significantly reduced in peripheral blood of HFRS patients and displayed a terminally differentiated profile with elevated expression of KLRG-1, NKG2A, CTLA-4, and Fas-L, correlating with disease severity. Two HTNV glycoprotein-derived nonapeptides that bound Qa-1 were identified. Following immunization with the identified HTNV peptides and subsequent HTNV challenge, wild-type (WT) mice showed attenuated renal immunopathology, whereas D227K knock-in mice (with disrupted Qa-1-CD8/TCR interaction) showed enhanced viral clearance in the spleen and kidney but exacerbated renal immunopathology. Mechanistically, Qa-1-restricted CD8+ Tregs from WT mice suppressed effector CD8+ T cell proliferation in a peptide-specific, CD8/TCR-dependent manner via enhanced TGF-β secretion. Strikingly, D227K mutation dichotomously reshaped Treg phenotype: bulk polyclonal CD8+ Tregs displayed compensatory upregulation of inhibitory receptors (NKG2A, CTLA-4, PD-1) and TGF-β, whereas epitope-specific CD8+ Tregs showed impaired antigen-specific suppressive function and attenuated TGF-β production. Collectively, these findings indicate that HLA-E/Qa-1-restricted CD8+ Tregs can restrain immunopathology during HTNV infection, potentially at the cost of delayed viral elimination. Modulation of this axis may provide insights for therapeutic strategies in HFRS and related viral hemorrhagic fevers.

Source: Proceedings of the National Academy of Sciences of the United States of America, https://doi.org/10.1073/pnas.2536836123

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#Hantavirus #stability and #inactivation

 

Abstract

Hantaviruses are zoonotic viruses that can cause highly pathogenic disease, including hantavirus cardiopulmonary syndrome (HCPS) and haemorrhagic fever with renal syndrome (HFRS), in humans with case-fatality rates of up to 50%. However, our understanding of the basic viral life cycle and the underlying causes of viral pathogenesis remains sparse, in large part due to a lack of molecular biology tools for hantaviruses and the need to work in high-containment laboratory facilities with these viruses. The stability and inactivation of hantavirus particles has been examined in some limited previous studies, however, a comprehensive, detailed and robust investigation of the stability of multiple hantaviruses has not been performed yet. Here, we investigated the kinetics of infectious Tula virus (TULV) particle production in Vero E6 cells and subsequent stability in cell culture media. In addition, we evaluated the stability of infectious virus particles in response to different physical and environmental stresses, including heat, freezing, dehydration and UV exposure, answering key questions about the environmental transmission potential of hantaviruses. Interestingly, we observed a remarkable stability of TULV when stored at room temperature or colder, as well as after dehydration, which suggests that hantaviruses could remain infectious for a sustained period of time after being secreted by their host species. Subsequently, we determined the ability of commonly used virus inactivation methods, including RNA and protein extraction buffers, to inactivate TULV both in a cell-free and cell-associated context and found that TULV was efficiently inactivated by all these methods similar to other enveloped RNA viruses. Finally, we successfully validated the complete inactivation using these inactivation methods using the highly pathogenic HCPS-causing New World Andes virus (ANDV) and the HFRS-causing Old World Hantaan virus (HTNV). These results provide valuable information about safe and effective inactivation methods of viral samples and about the environmental risk potential of hantaviruses.

Source: 

Link: https://journals.plos.org/plosntds/article?id=10.1371/journal.pntd.0013781

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