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1.
Emerg Microbes Infect ; 11(1): 1778-1786, 2022 Dec.
Article in English | MEDLINE | ID: covidwho-1915483

ABSTRACT

The Omicron BA.1 (B.1.1.529) SARS-CoV-2 variant is characterized by a high number of mutations in the viral genome, associated with immune escape and increased viral spread. It remains unclear whether milder COVID-19 disease progression observed after infection with Omicron BA.1 in humans is due to reduced pathogenicity of the virus or due to pre-existing immunity from vaccination or previous infection. Here, we inoculated hamsters with Omicron BA.1 to evaluate pathogenicity and kinetics of viral shedding, compared to Delta (B.1.617.2) and to animals re-challenged with Omicron BA.1 after previous SARS-CoV-2 614G infection. Omicron BA.1 infected animals showed reduced clinical signs, pathological changes, and viral shedding, compared to Delta-infected animals, but still showed gross- and histopathological evidence of pneumonia. Pre-existing immunity reduced viral shedding and protected against pneumonia. Our data indicate that the observed decrease of disease severity is in part due to intrinsic properties of the Omicron BA.1 variant.


Subject(s)
COVID-19 , SARS-CoV-2 , Animals , Cricetinae , Humans , Mesocricetus , SARS-CoV-2/genetics , Vaccination
2.
Trends Neurosci ; 45(5): 358-368, 2022 05.
Article in English | MEDLINE | ID: covidwho-1783775

ABSTRACT

Severe acute respiratory syndrome-coronavirus 2 (SARS-CoV-2) infection is associated with a diverse spectrum of neurological complications during the acute and postacute stages. The pathogenesis of these complications is complex and dependent on many factors. For accurate and consistent interpretation of experimental data in this fast-growing field of research, it is essential to use terminology consistently. In this article, we outline the distinctions between neuroinvasiveness, neurotropism, and neurovirulence. Additionally, we discuss current knowledge of these distinct features underlying the pathogenesis of SARS-CoV-2-associated neurological complications. Lastly, we briefly discuss the advantages and limitations of different experimental models, and how these approaches can further be leveraged to advance the field.


Subject(s)
COVID-19 , Nervous System Diseases , Humans , SARS-CoV-2
3.
EuropePMC; 2022.
Preprint in English | EuropePMC | ID: ppcovidwho-331261

ABSTRACT

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection is associated with various neurological complications. SARS-CoV-2 infection induces neuroinflammation in the central nervous system (CNS), whereat the olfactory bulb seems to be involved most frequently. Here we show differences in the neuroinvasiveness and neurovirulence among SARS-CoV-2 variants in the hamster model five days post inoculation. Replication in the olfactory mucosa was observed in all hamsters, but most prominent in D614 inoculated hamsters. We observed neuroinvasion into the CNS via the olfactory nerve in D614G-, but not Delta (B.1.617.2)- or Omicron BA.1 (B.1.1.529) inoculated hamsters. Neuroinvasion was associated with neuroinflammation in the olfactory bulb of hamsters inoculated with D614G but hardly in Delta or Omicron BA.1. Altogether, this indicates that there are differences in the neuroinvasive and neurovirulent potential among SARS-CoV-2 variants in the acute phase of the infection in the hamster model.

4.
EuropePMC; 2022.
Preprint in English | EuropePMC | ID: ppcovidwho-330302

ABSTRACT

The Omicron BA.1 (B.1.1.529) SARS-CoV-2 variant is characterized by a high number of mutations in the viral genome, associated with immune-escape and increased viral spread. It remains unclear whether milder COVID-19 disease progression observed after infection with Omicron BA.1 in humans is due to reduced pathogenicity of the virus or due to pre-existing immunity from vaccination or previous infection. Here, we inoculated hamsters with Omicron BA.1 to evaluate pathogenicity and kinetics of viral shedding, compared to Delta (B.1.617.2) and to animals re-challenged with Omicron BA.1 after previous SARS-CoV-2 614G infection. Omicron BA.1 infected animals showed reduced clinical signs, pathological changes, and viral shedding, compared to Delta-infected animals, but still showed gross- and histopathological evidence of pneumonia. Pre-existing immunity reduced viral shedding and protected against pneumonia. Our data indicate that the observed decrease of disease severity is in part due to intrinsic properties of the Omicron BA.1 variant.

5.
mSphere ; 6(3): e0027021, 2021 06 30.
Article in English | MEDLINE | ID: covidwho-1280401

ABSTRACT

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection is associated with a wide variety of neurological complications. Even though SARS-CoV-2 is rarely detected in the central nervous system (CNS) or cerebrospinal fluid, evidence is accumulating that SARS-CoV-2 might enter the CNS via the olfactory nerve. However, what happens after SARS-CoV-2 enters the CNS is poorly understood. Therefore, we investigated the replication kinetics, cell tropism, and associated immune responses of SARS-CoV-2 infection in different types of neural cultures derived from human induced pluripotent stem cells (hiPSCs). SARS-CoV-2 was compared to the neurotropic and highly pathogenic H5N1 influenza A virus. SARS-CoV-2 infected a minority of individual mature neurons, without subsequent virus replication and spread, despite angiotensin-converting enzyme 2 (ACE2), transmembrane protease serine 2 (TMPRSS2), and neuropilin-1 (NPR1) expression in all cultures. However, this sparse infection did result in the production of type III interferons and interleukin-8 (IL-8). In contrast, H5N1 virus replicated and spread very efficiently in all cell types in all cultures. Taken together, our findings support the hypothesis that neurological complications might result from local immune responses triggered by virus invasion, rather than abundant SARS-CoV-2 replication in the CNS. IMPORTANCE Infections with the recently emerged severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are often associated with neurological complications. Evidence suggests that SARS-CoV-2 enters the brain via the olfactory nerve; however, SARS-CoV-2 is only rarely detected in the central nervous system of COVID-19 patients. Here, we show that SARS-CoV-2 is able to infect neurons of human iPSC neural cultures but that this infection is abortive and does not result in virus spread to other cells. However, infection of neural cultures did result in the production of type III interferon and IL-8. This study suggests that SARS-CoV-2 might enter the CNS and infect individual neurons, triggering local immune responses that could contribute to the pathogenesis of SARS-CoV-2-associated CNS disease.


Subject(s)
Induced Pluripotent Stem Cells/cytology , Influenza A Virus, H5N1 Subtype/physiology , Neurons/virology , SARS-CoV-2/physiology , Viral Tropism , Virus Replication , Animals , Brain Diseases/etiology , COVID-19/complications , Chlorocebus aethiops , Dogs , Humans , Influenza A Virus, H5N1 Subtype/immunology , Kinetics , Madin Darby Canine Kidney Cells , SARS-CoV-2/immunology , Vero Cells
6.
mSphere ; 6(3): e0031121, 2021 06 30.
Article in English | MEDLINE | ID: covidwho-1247323

ABSTRACT

COVID-19 is associated with a wide range of extrarespiratory complications, of which the pathogenesis is currently not fully understood. However, both systemic spread and systemic inflammatory responses are thought to contribute to the systemic pathogenesis. In this study, we determined the temporal kinetics of viral RNA in serum (RNAemia) and the associated inflammatory cytokines and chemokines during the course of COVID-19 in hospitalized patients. We show that RNAemia can be detected in 90% of the patients who develop critical disease, compared to 50% of the patients who develop moderate or severe disease. Furthermore, RNAemia lasts longer in patients who develop critical disease. Elevated levels of interleukin-10 (IL-10) and MCP-1-but not IL-6-are associated with viral load in serum, whereas higher levels of IL-6 in serum were associated with the development of critical disease. In conclusion, RNAemia is common in hospitalized patients, with the highest frequency and duration in patients who develop critical disease. The fact that several cytokines or chemokines are directly associated with the presence of viral RNA in the circulation suggests that the development of RNAemia is an important factor in the systemic pathogenesis of COVID-19. IMPORTANCE Severe COVID-19 can be considered a systemic disease as many extrarespiratory complications occur. However, the systemic pathogenesis is poorly understood. Here, we show that the presence of viral RNA in the blood (RNAemia) occurs more frequently in patients who develop critical disease, compared to patients with moderate or severe disease. In addition, RNAemia is associated with increased levels of inflammatory cytokines and chemokines, like MCP-1 and IL-10, in serum during the course of disease. This suggests that extrarespiratory spread of SARS-CoV-2 contributes to systemic inflammatory responses, which are an important factor in the systemic pathogenesis of COVID-19.


Subject(s)
COVID-19/immunology , Cytokines/blood , RNA, Viral/blood , SARS-CoV-2/genetics , COVID-19/etiology , COVID-19/virology , Hospitalization , Humans , Kinetics , Severity of Illness Index
8.
Cell Rep ; 31(3): 107549, 2020 04 21.
Article in English | MEDLINE | ID: covidwho-100496

ABSTRACT

Importin-α adaptor proteins orchestrate dynamic nuclear transport processes involved in cellular homeostasis. Here, we show that importin-α3, one of the main NF-κB transporters, is the most abundantly expressed classical nuclear transport factor in the mammalian respiratory tract. Importin-α3 promoter activity is regulated by TNF-α-induced NF-κB in a concentration-dependent manner. High-level TNF-α-inducing highly pathogenic avian influenza A viruses (HPAIVs) isolated from fatal human cases harboring human-type polymerase signatures (PB2 627K, 701N) significantly downregulate importin-α3 mRNA expression in primary lung cells. Importin-α3 depletion is restored upon back-mutating the HPAIV polymerase into an avian-type signature (PB2 627E, 701D) that can no longer induce high TNF-α levels. Importin-α3-deficient mice show reduced NF-κB-activated antiviral gene expression and increased influenza lethality. Thus, importin-α3 plays a key role in antiviral immunity against influenza. Lifting the bottleneck in importin-α3 availability in the lung might provide a new strategy to combat respiratory virus infections.


Subject(s)
Influenza A virus/immunology , Influenza, Human/immunology , Orthomyxoviridae Infections/immunology , alpha Karyopherins/biosynthesis , A549 Cells , Animals , Cell Line, Tumor , Chlorocebus aethiops , Down-Regulation , Female , HEK293 Cells , Humans , Influenza, Human/genetics , Influenza, Human/virology , Mice , Mice, Inbred C57BL , Mice, Knockout , Middle Aged , Orthomyxoviridae Infections/genetics , Orthomyxoviridae Infections/virology , RNA, Messenger/genetics , RNA, Messenger/metabolism , Vero Cells , alpha Karyopherins/genetics , alpha Karyopherins/immunology
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