Neuraminidase is a host-directed approach to regulate neutrophil responses in sepsis and COVID-19

BACKGROUND AND PURPOSE

Neutrophil overstimulation plays a crucial role in tissue damage during severe infections. Because pathogen-derived neuraminidase (NEU) stimulates neutrophils, we investigated whether host NEU can be targeted to regulate the neutrophil dysregulation observed in severe infections.

EXPERIMENTAL APPROACH

The effects of NEU inhibitors on lipopolysaccharide (LPS)-stimulated neutrophils from healthy donors or COVID-19 patients were determined by evaluating the shedding of surface sialic acids, cell activation, and reactive oxygen species (ROS) production. Re-analysis of single-cell RNA sequencing of respiratory tract samples from COVID-19 patients also was carried out. The effects of oseltamivir on sepsis and betacoronavirus-induced acute lung injury were evaluated in murine models.

KEY RESULTS

Oseltamivir and zanamivir constrained host NEU activity, surface sialic acid release, cell activation, and ROS production by LPS-activated human neutrophils. Mechanistically, LPS increased the interaction of NEU1 with matrix metalloproteinase 9 (MMP-9). Inhibition of MMP-9 prevented LPS-induced NEU activity and neutrophil response. In vivo, treatment with oseltamivir fine-tuned neutrophil migration and improved infection control as well as host survival in peritonitis and pneumonia sepsis. NEU1 also is highly expressed in neutrophils from COVID-19 patients, and treatment of whole-blood samples from these patients with either oseltamivir or zanamivir reduced neutrophil overactivation. Oseltamivir treatment of intranasally infected mice with the mouse hepatitis coronavirus 3 (MHV-3) decreased lung neutrophil infiltration, viral load, and tissue damage.

CONCLUSION AND IMPLICATIONS

These findings suggest that interplay of NEU1-MMP-9 induces neutrophil overactivation. In vivo, NEU may serve as a host-directed target to dampen neutrophil dysfunction during severe infections.

Recombinant Bacillus Calmette-Guérin Expressing SARS-CoV-2 Chimeric Protein Protects K18-hACE2 Mice against Viral Challenge

COVID-19 has accounted for more than 6 million deaths worldwide. Bacillus Calmette-Guérin (BCG), the existing tuberculosis vaccine, is known to induce heterologous effects over other infections due to trained immunity and has been proposed to be a potential strategy against SARS-CoV-2 infection. In this report, we constructed a recombinant BCG (rBCG) expressing domains of the SARS-CoV-2 nucleocapsid and spike proteins (termed rBCG-ChD6), recognized as major candidates for vaccine development. We investigated whether rBCG-ChD6 immunization followed by a boost with the recombinant nucleocapsid and spike chimera (rChimera), together with alum, provided protection against SARS-CoV-2 infection in K18-hACE2 mice. A single dose of rBCG-ChD6 boosted with rChimera associated with alum elicited the highest anti-Chimera total IgG and IgG2c Ab titers with neutralizing activity against SARS-CoV-2 Wuhan strain when compared with control groups. Importantly, following SARS-CoV-2 challenge, this vaccination regimen induced IFN-γ and IL-6 production in spleen cells and reduced viral load in the lungs. In addition, no viable virus was detected in mice immunized with rBCG-ChD6 boosted with rChimera, which was associated with decreased lung pathology when compared with BCG WT-rChimera/alum or rChimera/alum control groups. Overall, our study demonstrates the potential of a prime-boost immunization system based on an rBCG expressing a chimeric protein derived from SARS-CoV-2 to protect mice against viral challenge.

Neuraminidase inhibitors rewire neutrophil function in vivo in murine sepsis and ex vivo in COVID-19

Neutrophil overstimulation plays a crucial role in tissue damage during severe infections. Neuraminidase (NEU)-mediated cleavage of surface sialic acid has been demonstrated to regulate leukocyte responses. Here, we report that antiviral NEU inhibitors constrain host NEU activity, surface sialic acid release, ROS production, and NETs released by microbial-activated human neutrophils. In vivo, treatment with Oseltamivir results in infection control and host survival in peritonitis and pneumonia models of sepsis. Single-cell RNA sequencing re-analysis of publicly data sets of respiratory tract samples from critical COVID-19 patients revealed an overexpression of NEU1 in infiltrated neutrophils. Moreover, Oseltamivir or Zanamivir treatment of whole blood cells from severe COVID-19 patients reduces host NEU-mediated shedding of cell surface sialic acid and neutrophil overactivation. These findings suggest that neuraminidase inhibitors can serve as host-directed interventions to dampen neutrophil dysfunction in severe infections.

Selection of TcII Trypanosoma cruzi population following macrophage infection

BACKGROUND

Chagas disease is caused by the protozoan parasite Trypanosoma cruzi, which exhibits a high genetic variability. TcI, TcII, or mixed TcI/TcII strains may be found during acute human infection while mainly TcII parasites are present at the chronic stage of disease. In a previously studied Chagas disease outbreak, we identified mixed TcI/TcII strains in the vector Triatoma tibiamaculata and only TcII strains in infected humans, indicating that T. cruzi populations may be selected within the human host.

METHODS

Utilizing molecular typing and cell biology techniques, we investigated the interaction of TcI, TcII, and mixed TcI/TcII strains with macrophages, an important cell population implicated in controlling protozoan infection.

RESULTS

TcII but not TcI strains were selected by both human and murine macrophages in vitro and by peritoneal cavity cells in vivo. Biological analysis revealed that, compared with TcI, TcII strains display higher infective and multiplicative ability as well as lower doubling time inside macrophages. However, TcI and TcII strains present similar susceptibility to interferon-γ-activated macrophages in vitro.

CONCLUSIONS

Taken together, our results reveal the existence of an intracellular selection process in macrophages that favors TcII, but not TcI, when infection occurs with vector-derived mixed TcI/TcII strains.

Differential upregulation of extracellular matrix molecules associated with the appearance of granule cell dispersion and mossy fiber sprouting during epileptogenesis in a murine model of temporal lobe epilepsy

We have investigated changes in the extracellular matrix of the hippocampus associated with the early progression of epileptogenesis in a murine model of temporal lobe epilepsy using immunohistochemistry. In the first week following intrahippocampal injection of the glutamate agonist, domoate, there is a latent period at the end of which begins a sequential upregulation of extracellular matrix (ECM) molecules in the granule cell layer of the dentate gyrus, beginning with neurocan and tenascin-C. This expression precedes the characteristic dispersion of the granule cell layer which is evident at 14 days post-injection when the first recurrent seizures can be recorded. At this stage, an upregulation of the chondroitin sulfate proteoglycan, phosphacan, the DSD-1 chondroitin sulfate motif, and the HNK-1 oligosaccharide are also observed. The expression of these molecules is localized differentially in the epileptogenic dentate gyrus, especially in the sprouting molecular layer, where a strong upregulation of phosphacan, tenascin-C, and HNK-1 is observed but there is no expression of the proteoglycan, neurocan, nor of the DSD-1 chondroitin sulfate motif. Hence, it appears that granule cell layer dispersion is accompanied by a general increase in the ECM, while mossy fiber sprouting in the molecular layer is associated with a more restricted repertoire. In contrast to these changes, the expression of the ECM glycoproteins, laminin and fibronectin, both of which are frequently implicated in tissue remodelling events, showed no changes associated with either granule cell dispersion or mossy fiber sprouting, indicating that the epileptogenic plasticity of the hippocampus is accompanied by ECM interactions that are characteristic of the CNS.

Tenascin glycoproteins and the complementary ligand DSD-1-PG/ phosphacan--structuring the neural extracellular matrix during development and repair

The differentiation and morphogenesis of neural tissues involves a diversity of interactions between neural cells and their environment. Many potentially important interactions occur with the extracellular matrix (ECM), a complex association of extracellular molecules organised into aggregates and polymers. The large modular glycoprotein, Tenascin-C, and the chondroitin sulphate proteoglycan, DSD-1-PG/Phosphacan, have complex and frequently overlapping expression patterns in the developing CNS. Their presence in zones of cell proliferation, migration, and differentiation, as well as in boundary structures, suggest that they may be involved in the modulation of an extensive range of cellular processes. They are both strongly up-regulated in a range of CNS lesions and pathologies, being components of the glial scar, and expressed by gliomas. Functional roles in many cellular processes are possible through their extensive molecular interaction sites, both with each other, and with many of the same cell surface receptors, adhesion molecules, growth factors and other matrix proteins. These multiple interactions involve sites on both their protein domains and on the heterogeneous carbohydrate groups with which they are post-translationally modified. In vitro assays demonstrate cell-type specific effects on adhesion, migration and the formation and extension of cellular processes, including neurites and axons.