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Although ocular manifestations are commonly reported in patients with coronavirus disease 2019 (COVID-19), there is currently no consensus on ocular tropism of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). To investigate this, we infected K18-hACE2 mice with SARS-CoV-2 using various routes. We observed ocular manifestation and retinal inflammation with cytokine production in the eyes of intranasally (IN) infected mice. An intratracheal (IT) injection resulted in virus spread from the lungs to the brain and eyes via trigeminal and optic nerves. Ocular and neuronal invasion were confirmed by an intracerebral (IC) infection. Notably, eye-dropped (ED) virus did not infect the lungs and was undetectable with time. Using infectious SARS-CoV-2-mCherry clones, we demonstrated the ocular and neurotropic distribution of the virus in vivo by a fluorescence-imaging system. Evidence for the ocular tropic and neuroinvasive characteristics of SARS-CoV-2 was confirmed in wild-type Syrian hamsters. Our data provides further understanding of the viral transmission; SARS-CoV-2 clinical characteristics; and COVID-19 control procedures. SummarySARS-CoV-2 can spread from the respiratory tract to the brain and eyes via trigeminal and optic nerves in animal models. This ocular tropism of SARS-CoV-2 through neuronal invasion likely causes ocular manifestation and retinal inflammation. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=148 SRC="FIGDIR/small/488607v1_ufig1.gif" ALT="Figure 1"> View larger version (44K): org.highwire.dtl.DTLVardef@151c2d5org.highwire.dtl.DTLVardef@ce3aeforg.highwire.dtl.DTLVardef@17f453aorg.highwire.dtl.DTLVardef@99e9c2_HPS_FORMAT_FIGEXP M_FIG C_FIG
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SARS-CoV-2, like other RNA viruses, has a propensity for genetic evolution owing to the low fidelity of its viral polymerase. This evolution results in the emergence of novel variants with different characteristics than their ancestral strain. Several recent reports have described a series of novel SARS-CoV-2 variants. Some of these have been identified as variants of concern (VOCs), including alpha (B.1.1.7, Clade GRY), beta (B.1.351, Clade GH), gamma (P.1, Clade GR), and delta (B.1.617.2, Clade G). VOCs are likely to have some effect on transmissibility, antibody evasion, and changes in therapeutic or vaccine effectiveness. However, the physiological and virological understanding of these variants remains poor. We demonstrated that these four VOCs exhibited differences in plaque size, thermal stability at physiological temperature, and replication rates. The mean plaque size of beta was the largest, followed by those of gamma, delta, and alpha. Thermal stability, evaluated by measuring infectivity and half-life after prolonged incubation at physiological temperature, was correlated with plaque size in all variants except alpha. However, despite its relatively high thermal stability, alphas small plaque size resulted in lower replication rates and fewer progeny viruses. Our findings may inform further virological studies of SARS-CoV-2 variant characteristics, VOCs, and variants of interest. These studies are important for the effective management of the COVID-19 pandemic. IMPORTANCEThe global pandemic caused by SARS-CoV-2 continues to persist, due in part to mutations that have resulted in the emergence of different variants. Many of these variants have become more virulent and infectious than their ancestral strain, resulting in an ever-increasing spread. However, our virological understanding of these variants remains poor. Here, we directly compared the plaque size, stability, and replication kinetics of four SARS-CoV-2 variants of concern following prolonged incubation at physiological temperatures. Our observations may help to characterize each variant in terms of their interactions with host factors and responses to environmental conditions. We also believe that our evaluations will improve understanding of the emergence of new variants and contribute to controlling their spread.
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To evaluate avian hepatitis E virus (aHEV) as an RNA vaccine platform, open reading frame 2 (ORF2) of aHEV was replaced by heterologous genes, such as enhanced green fluorescent protein (eGFP) and hemagglutinin (HA)-tag, in aHEV infectious cDNA clones. eGFP and HA-tag replicons were expressed in leghorn male hepatoma (LMH) cells. To confirm expression of the heterologous protein, ORF2 was replaced with the antigenic S1 gene of infectious bronchitis virus (IBV). The IBVS1 replicon was expressed in LMH cells. To our knowledge, this is the first investigation showing potential as a RNA vaccine platform using an aHEV. In the future, it may be used in the development of RNA vaccines against various pathogens.
RESUMO
To evaluate avian hepatitis E virus (aHEV) as an RNA vaccine platform, open reading frame 2 (ORF2) of aHEV was replaced by heterologous genes, such as enhanced green fluorescent protein (eGFP) and hemagglutinin (HA)-tag, in aHEV infectious cDNA clones. eGFP and HA-tag replicons were expressed in leghorn male hepatoma (LMH) cells. To confirm expression of the heterologous protein, ORF2 was replaced with the antigenic S1 gene of infectious bronchitis virus (IBV). The IBVS1 replicon was expressed in LMH cells. To our knowledge, this is the first investigation showing potential as a RNA vaccine platform using an aHEV. In the future, it may be used in the development of RNA vaccines against various pathogens.
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Two infectious bronchitis virus (IBV) K046-12 and K047-12 strains were isolated and the nearly complete genomes of them were sequenced. Sequence comparisons showed that the K046-12 genome was most similar to Korean IBV strains, and the K047-12 genome was most similar to QX-like IBV strains. Phylogenetic analysis showed that nearly all K046-12 and most K046-12 genes were placed in the same cluster as Korean IBV isolates, but the S1 region was placed in the same cluster as Mass-type IBVs. For K047-12, nearly all K047-12 and most K047-12 genes were located in the same cluster as QX-like IBVs, but the M region was located in the same cluster as Korean IBV isolates with K047-12. Recombination analysis confirmed that K046-12 is a recombinant strain with the primary parental sequence derived from Korean IBVs and minor parental sequence derived from Mass-type IBV, and K047-12 is a recombinant strain with the major parental sequence derived from QX-IBV and minor parental sequence derived from Korean IBVs. This study showed that new IBV recombinants are constantly generated among various IBVs, including those used for vaccination. Therefore, genetic analysis of new virus isolates should be performed for effective infectious bronchitis control and appropriate vaccine development.
Assuntos
Humanos , Bronquite , Genoma , Vírus da Bronquite Infecciosa , Coreia (Geográfico) , Pais , Recombinação Genética , VacinaçãoRESUMO
The helicase genes and hypervariable regions (HVRs) of three avian hepatitis E viruses (HEVs) detected at three different farms were sequenced and characterized. Two isolates (DW-L and GI-B2) were classified as genotype 2 and one isolate (GR-B) was classified as genotype 1. A phylogenetic tree, based on the helicase gene and HVR nucleotide sequences, revealed the newly detected viruses and other avian HEVs were classified similarly. Unlike previously reported avian HEVs, the DW-L isolate detected in broiler breeders with characteristic lesions of avian HEV had no prolinerich motif in its HVR, suggesting that the proline-rich motif is non-essential for viral replication and infection.
RESUMO
The helicase genes and hypervariable regions (HVRs) of three avian hepatitis E viruses (HEVs) detected at three different farms were sequenced and characterized. Two isolates (DW-L and GI-B2) were classified as genotype 2 and one isolate (GR-B) was classified as genotype 1. A phylogenetic tree, based on the helicase gene and HVR nucleotide sequences, revealed the newly detected viruses and other avian HEVs were classified similarly. Unlike previously reported avian HEVs, the DW-L isolate detected in broiler breeders with characteristic lesions of avian HEV had no prolinerich motif in its HVR, suggesting that the proline-rich motif is non-essential for viral replication and infection.
