A safe and effective Hantaan virus (HTNV) vaccine is highly desirable because HTNV causes an acute and often fatal disease (hemorrhagic fever with renal syndrome, HFRS). Since the immunity of the inactivated vaccine is weak and the safety is poor, HTNV virus-like particles (VLPs) offer an attractive and safe alternative. These particles lack the viral genome but are perceived by the immune system as virus particles. We hypothesized that adding immunostimulatory signals to VLPs would enhance their efficacy. To accomplish this enhancement, we generated chimeric HTNV VLPs containing glycosylphosphatidylinositol (GPI)-anchored granulocyte macrophage colony-stimulating factor (GM-CSF) or CD40 ligand (CD40L) and investigated their biological activity in vitro. The immunization of mice with chimeric HTNV VLPs containing GM-CSF or CD40L induced stronger humoral immune responses and cellular immune responses compared to the HTNV VLPs and Chinese commercial inactivated hantavirus vaccine. Chimeric HTNV VLPs containing GM-CSF or CD40L also protected mice from an HTNV challenge. Altogether, our results suggest that anchoring immunostimulatory molecules into HTNV VLPs can be a potential approach for the control and prevention of HFRS.
Hantaan viruses (HTNVs) are zoonotic pathogens transmitted mainly by rodents and capable of infecting humans. Increasing knowledge of the human response to HTNV infection can guide the development of new preventative vaccines and therapeutic strategies. Here, we show that HTNV can infect CD8+ T cells in vivo in patients diagnosed with hemorrhagic fever with renal syndrome (HFRS). Electron microscopy-mediated tracking of the life cycle and ultrastructure of HTNV-infected CD8+ T cells in vitro showed an association between notable increases in cytoplasmic multivesicular bodies and virus production. Notably, based on a clinical cohort of 280 patients, we found that circulating HTNV-infected CD8+ T cell numbers in blood were proportional to disease severity. These results demonstrate that viral infected CD8+ T cells may be used as an adjunct marker for monitoring HFRS disease progression and that modulating T cell functions may be explored for new treatment strategies.
Infection of Hantaan virus (HTNV) usually causes hemorrhagic fever with renal syndrome (HFRS). China has the worst epidemic incidence of HFRS as well as high fatality. Inactivated whole virus has been used for HFRS vaccination, however there are still problems such as safety concerns. CD40 ligand (CD40L) and granulocyte macrophage colony-stimulating factor (GM-CSF) are well-known immune stimulating molecules that can enhance antigen presenting, lymphocytes activation and maturation, incorporation of CD40L and GM-CSF to the surface of virus like particles (VLPs) can greatly improve the vaccination effect. We constructed eukaryotic vectors expressing HTNV M segment and S segment, as well as vectors expressing HTNV M segment with CD40L or GM-CSF, our results showed successful production of CD40L or GM-CSF incorporated HTNV VLPs. In vitro stimulation with CD40L or GM-CSF anchored HTNV VLP showed enhanced activation of macrophages and DCs. CD40L/GM-CSF incorporated VLP can induce higher level of HTNV specific antibody and neutralizing antibody in mice. Immunized mice splenocytes showed higher ability of secreting IFN-γ and IL-2, as well as enhancing CTL activity. These results suggest CD40L/GM-CSF incorporated VLP can serve as prospective vaccine candidate.
The rapid evolution of highly infectious pathogens is a major threat to global public health. In the front line of defense against bacteria, fungi, and viruses, antimicrobial peptides (AMPs) are naturally produced by all living organisms and offer new possibilities for next-generation antibiotic development. However, the low yields and difficulties in the extraction and purification of AMPs have hindered their industry and scientific research applications. To overcome these barriers, we enabled high expression of bomidin, a commercial recombinant AMP based upon bovine myeloid antimicrobial peptide-27. This novel AMP, which can be expressed in Escherichia coli by adding methionine to the bomidin sequence, can be produced in bulk and is more biologically active than chemically synthesized AMPs. We verified the function of bomidin against a variety of bacteria and enveloped viruses, including severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), herpes simplex virus (HSV), dengue virus (DENV), and chikungunya virus (CHIKV). Furthermore, based on the molecular modeling of bomidin and membrane lipids, we elucidated the possible mechanism by which bomidin disrupts bacterial and viral membranes. Thus, we obtained a novel AMP with an optimized, efficient heterologous expression system for potential therapeutic application against a wide range of life-threatening pathogens.
The cytotoxic T lymphocyte (CTL) response plays a key role in controlling viral infection, but only a few epitopes within the HTNV glycoprotein (GP) that are recognized by CTLs have been reported. In this study, we identified one murine HTNV GP-derived H2-Kb-restricted CTL epitope in C57BL/6 mice, which could be used to design preclinical studies of vaccines for HTNV infection. First, 15 8-mer peptides were selected from the HTNV GP amino acid sequence based on a percentile rank of <=1% by IEDB which is the most comprehensive collection of epitope prediction and analysis tool. A lower percentile rank indicates higher affinity and higher immune response. In the case of the consensus method, we also evaluated the binding score of peptide-binding affinity by the BIMAS software to confirm that all peptides were able to bind H2-Kb. Second, one novel GP-derived CTL epitope, GP6 aa456-aa463 (ITSLFSLL), was identified in the splenocytes of HTNV-infected mice using the IFN-γ ELISPOT assay. Third, a single peptide vaccine was administered to C57BL/6 mice to evaluate the immunogenic potential of the identified peptides. ELISPOT and cell-mediated cytotoxicity assays showed that this peptide vaccine induced a strong IFN-γ response and potent cytotoxicity in immunized mice. Last, we demonstrated that the peptide-vaccinated mice had partial protection from challenge with HTNV. In conclusion, we identified an H2-Kb-restricted CTL epitope with involvement in the host immune response to HTNV infection.
Hantaan virus (HTNV) infects humans and causes hemorrhagic fever with renal syndrome (HFRS). The development of well-characterized animal models of HFRS could accelerate the testing of vaccine candidates and therapeutic agents and provide a useful tool for studying the pathogenesis of HFRS. Because NLRC3 has multiple immunoregulatory roles, we investigated the susceptibility of Nlrc3−/− mice to HTNV infection in order to establish a new model of HFRS. Nlrc3−/− mice developed weight loss, renal hemorrhage, and tubule dilation after HTNV infection, recapitulating many clinical symptoms of human HFRS. Moreover, infected Nlrc3−/− mice showed higher viral loads in serum, spleen, and kidney than wild type C57BL/6 (WT) mice, and some of them manifested more hematological disorders and significant pathological changes within multiple organs than WT mice. Our results identify that HTNV infected Nlrc3−/− mice can develop clinical symptoms and pathological changes resembling patients with HFRS, suggesting a new model for studying the pathogenesis and testing of candidate vaccines and therapeutics.
Hemorrhagic fever with renal syndrome (HFRS) is a severe, viral zoonotic disease which occurs worldwide, particularly in Asia and Europe. In China, the Hantaan virus (HTNV) and the Seoul virus (SEOV) are known to be the most prevalent causative agents of HFRS. Since no protective vaccines or effective treatments are available for human use, accurate and reliable diagnostic methods are essential for disease surveillance. In the present study, the viral loads in cell culture supernatant, infected mice blood and clinical serum samples were quantified using the SYBR‑Green I-based reverse transcription-quantitiative polymerase chain reaction (RT-qPCR) assay, which targeted the S gene sequence of the HTNV and SEOV genomes. The cRNA of these two viruses were synthesized as a positive control and 10-fold serially diluted from 1x105 to 1x100 copies/µl. Standard curves were generated by plotting the mean cycle threshold (Ct) values versus copy numbers. The standard curve of HTNV had a correlation coefficient (R2) of 0.994, efficiency of amplification (E) of 101.9%, and the slope of -3.278, whereas that of SEOV had an R2 of 0.993, E of 104.8%, and the slope of -3.212. The minimum detection limit of the RT-qPCR assay for HTNV and SEOV was 101 copies/µl. Two qPCR assays were successfully established for the detection of HTNV and SEOV, respectively. Taken together, these findings demonstrate that using the SYBR‑Green I-based RT-qPCR assay, the HTNV and SEOV may be genotyped precisely without cross-reactivity. Furthermore, viral RNA may be detected and quantified in cells, mice and infected individuals, which may be useful in epidemiological studies as well as for early monitoring and further preventative treatment against SEOV and HTNV-induced diseases.
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