Application of FAD synthetase FLAD1 in preparation of medicine for preventing or treating novel coronavirus infection

Abstract

The invention belongs to the technical field of biological medicine, and particularly discloses an application of FAD synthetase FLLA1 in preparation of a medicine for preventing or treating novel coronavirus infection, and the application is that a substance for targeted inhibition of FLLA1 expression is adopted to prepare the medicine for preventing or treating novel coronavirus infection. Experiments prove that the replication of the novel coronavirus in the cells after the FLAD1 is knocked out is obviously reduced, and the FAD synthetase FLAD1 is proved to be capable of effectively inhibiting the proliferation of the novel coronavirus. The invention provides a new treatment strategy for prevention and treatment of infectious diseases caused by novel coronavirus infection.

Description

Technical Field

[0001] The present invention belongs to the field of biomedicine technology, and in particular relates to the use of FAD synthetase FLAD1 in the preparation of drugs for preventing or treating novel coronavirus infection. Background Art

[0002] COVID-19 is a severe acute respiratory syndrome caused by the novel coronavirus (SARS-CoV-2). The novel coronavirus is an enveloped, single-stranded, positive-strand RNA virus that can cause respiratory infections and heart damage in humans, with a mortality rate of about 3.8%.

[0003] The 5' end of the novel coronavirus genome has an m7GTP cap structure, the 3' end has a polyA tail structure and 6 ORFs (open reading frames), of which ORF1 encodes 16 non-structural proteins involved in viral genome replication and transcription; the remaining ORFs encode 7 auxiliary proteins (ORF3a, ORF3b, ORF6, ORF7a, ORF7b, ORF8 and ORF10) and 4 structural proteins (S, E, M and N). With the emergence of mutant strains such as Delta and Omicron, the protectiveness of vaccines has been challenged, so it is urgent to screen a conservative and effective vaccine and drug target. The N protein gene is very conservative and stable. The amino acid homology between SARS-CoV-2 and SARS-CoV N proteins is as high as 91%. The versatility and conservatism of the N protein make it a very potential target for coronavirus drug intervention. Summary of the invention

[0004] In order to solve the above problems, the primary purpose of the present invention is to provide a new therapeutic target for patients infected with the new coronavirus, which is flavin adenine dinucleotide (FAD) synthetase FLAD1, that is, the use of FAD synthetase FLAD1 in the preparation of drugs for preventing or treating new coronavirus infection.

[0005] The specific technical solutions of the present invention include:

[0006] The present invention provides the use of FAD synthetase FLAD1 in the preparation of a drug for preventing or treating novel coronavirus infection.

[0007] As a further optimization scheme of the present invention, the application is to use a substance that targets and inhibits FLAD1 expression to prepare a drug for preventing or treating novel coronavirus infection.

[0008] As a further optimization scheme of the present invention, the substance that targets and inhibits FLAD1 expression includes any one of a FLAD1 inhibitor, a FLAD1 siRNA, or a gene editing tool that knocks out FLAD1 expression.

[0009] As a further optimized solution of the present invention, the FLAD1 siRNA is any one of (1) to (4):

[0010] (1) siRNA formed by annealing two single strands as shown in SEQ ID No. 3 and SEQ ID No. 4;

[0011] (2) siRNA formed by annealing two single strands as shown in SEQ ID No. 5 and SEQ ID No. 6;

[0012] (3) siRNA formed by annealing two single strands as shown in SEQ ID No. 7 and SEQ ID No. 8;

[0013] (4) siRNA formed by annealing two single strands as shown in SEQ ID No. 9 and SEQ ID No. 10.

[0014] The present invention also provides a drug for preventing or treating novel coronavirus infection, wherein the drug is a FLAD1 siRNA that targets and inhibits FLAD1 expression.

[0015] As a further optimized solution of the present invention, the FLAD1 siRNA is a siRNA formed by annealing two single strands as shown in SEQ ID No. 7 and SEQ ID No. 8.

[0016] In summary, the beneficial effects of the present invention are:

[0017] The present invention provides a new target for treating novel coronavirus infection, namely, FAD synthetase FLAD1. Studies have shown that after knocking out the gene expressing FAD synthetase FLAD1, the replication of novel coronavirus is significantly reduced, effectively inhibiting the proliferation of novel coronavirus in cells. FLAD1 is expected to become a potential therapeutic target for novel coronavirus infection. The present invention provides a new strategy for the prevention and treatment of infectious diseases caused by novel coronavirus infection, and has important application value in drug research and development and vaccine development. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 To detect NP by co-immunoprecipitation and immunoblotting SARS-CoV-2 Interaction with FAD synthase FLAD1;

[0019] Figure 2 To detect NP by co-immunoprecipitation and immunoblotting SARS-CoV-2 Whether the interaction with the FAD synthetase FLAD1 is a direct interaction;

[0020] Figure 3To detect NPs using DuoLink immunofluorescence assay SARS-CoV-2 Colocalization with FLAD1;

[0021] Figure 4 Immunoblotting was used to confirm whether FLAD1 was knocked out.

[0022] Figure 5 After knocking down FLAD1 in cells using FLAD1 siRNA, the mRNA level of FLAD1 was detected by fluorescent quantitative PCR.

[0023] Figure 6 After knocking out FLAD1 in cells using CRISPER-Cas9, fluorescent quantitative PCR was used to detect the replication level of the test virus. DETAILED DESCRIPTION

[0024] The present application is further described in detail below in conjunction with the accompanying drawings. It is necessary to point out here that the following specific implementation methods are only used to further illustrate the present application and cannot be understood as limiting the scope of protection of the present application. Technical personnel in this field can make some non-essential improvements and adjustments to the present application based on the above application content.

[0025] 1. Materials

[0026] 1. Plasmid

[0027] Flag-NP SARS-CoV-2 , HA-FLAD1 were constructed by our laboratory. The target fragment was cloned into the pCDNA3.1 vector through the double restriction sites of BamH1 and EcoR1. The Flag (HA) tag was located at the N-terminus of the NP (FLAD1) gene and fused with the target protein for expression. The NP gene was from the research group, and the FLAD1 gene was cloned from the A549 cell genome. The nucleotide sequence of the FLAD1 gene is shown in SEQ ID NO.1, and the FLAD1 protein sequence is shown in SEQ ID NO.2.

[0028] pGEX-4T-1-FLAD1 was purchased from GENERALCBIOL. For structural operations, please refer to the article published by Hartenina et al. in JBC in 2020. (Hartenian E, Nandakumar D, Lari A, Ly M, Tucker JM, Glaunsinger BA. The molecular virology of coronaviruses. J Biol Chem. 2020 Sep 11; 295(37): 12910-12934. doi: 10.1074 / jbc.REV120.013930. Epub 2020 Jul 13. PMID: 32661197; PMCID: PMC7489918.).

[0029] 2. Reagents

[0030] Fluorescence quantitative PCR detection kit was purchased from Promega (catalog number A6020); immunofluorescence DuoLink kit was purchased from Sigma (catalog number DUO92004-100RXN); transfection reagent Lipofectamine 3000 was purchased from Thermo; F-12K culture medium (catalog number 2958713), fetal bovine serum (catalog number 16000-044), trypsin (catalog number 25200-056), and PBS (catalog number C10010500BT) were all purchased from GIBCO; TransIT X2 transfection reagent was purchased from Mirus Bio (catalog number MIR6003); FLAD1 antibody was purchased from Proteintech (catalog number 14118-1-AP); and β-Actin antibody was purchased from Proteintech (catalog number 66009-1-Ig).

[0031] 3. Cells

[0032] Human embryonic kidney 293 cells and human lung gland A549 cells were purchased from the National Laboratory Cell Resource Sharing Platform.

[0033] Human lung gland A549 (FLAD1 KO), the construction method is: based on the CRISPR-Cas9 system, gRNA is designed for the FLAD1 gene, the gRNA and Cas9 are co-expressed in the target cells, and positive clones are obtained by resistance screening.

[0034] Human lung gland A549 (ACE2 OE), ACE2 is the cell surface receptor of the new coronavirus. Since the expression of ACE2 in A549 cells is relatively low, in order to ensure the normal infection of the new coronavirus, ACE2 protein needs to be stably expressed in A549 cells. The specific construction method is: first construct the ACE2 plasmid, then transfect it into the cells, and then obtain a clone that stably expresses ACE2 through resistance screening.

[0035] Unless otherwise specified, all reagents and materials in the present invention are commercially available products.

[0036] 2. Methods

[0037] Unless otherwise specified, the following methods are conventional methods known to those skilled in the art.

[0038] 1. Immunoprecipitation and immunoblotting were used to detect and confirm the interaction between FAD synthetase FLAD1 and the new coronavirus NP. The specific method is as follows:

[0039] (1) HA-FLAD1 and Flag-NP SARS-CoV-2 Plasmids were transfected using Lipofectamine 3000 reagent. Figure 1 The indicated combinations were transfected into human embryonic kidney 293 cells (purchased from the National Laboratory Cell Resource Sharing Platform), 3 μg of plasmid was transfected, the culture medium was aspirated after 48 h, the cells were collected and resuspended in pre-cooled 1× PBS, washed 3 times, and the supernatant was completely discarded. After adding cell lysis buffer (Tris-HCl 50mM pH 8.0, NaCl 150mM, NP40 1%, protease inhibitor 1 tablet / 50mL), place on ice for 30min, centrifuge at 12000rpm for 10min at 4℃, aspirate the supernatant into a clean 1.5mL EP tube, add 15μL agarose beads coupled to Flag antibody, incubate at 4℃ for 2h for immunoprecipitation, centrifuge at 8000rpm for 1min at 4℃, remove the supernatant, wash 3 times with cell lysis buffer without protease inhibitors, add 75μL 1×SDS-PAGE loading buffer to the immunoprecipitated product, boil in water bath for 10min, centrifuge at 4℃ and 8000rpm for 3min, take 15μL supernatant for polyacrylamide gel electrophoresis (SDS-PAGE), electrophoresis at 80V for 30min, adjust the voltage to 120V until bromophenol blue migrates to the bottom of the gel to stop electrophoresis.

[0040] (2) Activate the PVDF membrane with 10 mL of methanol for 10 seconds, wash with deionized water and place in 1× semi-dry transfer buffer (Tris-HCl 24 mM, glycine 5 mM, 20% methanol). Then, place the SDS-PAGE gel after electrophoresis on the PVDF membrane; place them layer by layer on the transfer apparatus in the order of filter paper-gel-membrane-filter paper from top to bottom, use a pressing rod to remove bubbles between layers, and transfer the membrane at 18V for 2 hours. After the transfer, use TBST containing 5% skim milk powder to block at room temperature for 1 hour, and wash 3 times with 1×TBST, each time for 5 minutes. Incubate with antibodies (anti-HA and anti-Flag) diluted 1:1000, at room temperature for 1 hour, and wash 3 times with 1×TBST, each time for 5 minutes. Finally, use enhanced chemiluminescence (ECL) and develop with a developer.

[0041] Figure 1 The results showed that FLAD1 was present in the immunoprecipitation product of Flag-NP, proving that FLAD1 and NP SARS -CoV-2 There is an interaction between them. And it is known that NP SARS-CoV-2 FLAD1 plays an important role in the replication of the new coronavirus. It is also a FAD synthase, which plays an important role in cell metabolism and oxidative phosphorylation. Based on the above experimental results and comprehensive functional analysis of FLAD1, it is determined that FLAD1 is involved in the replication of the new coronavirus. Therefore, by changing the activity of FLAD1, the expression of related genes can be further affected.

[0042] 2. Far-western and immunoblotting were used to detect whether the interaction between FAD synthase FLAD1 and the new coronavirus NP was a direct interaction. The specific methods are as follows:

[0043] (1) Flag-NP SARS-CoV-2 Plasmids were transfected using Lipofectamine 3000 reagent. Figure 2The indicated combinations were transfected into human embryonic kidney 293 cells, 3 μg of plasmid was transfected, the medium was aspirated after 48 h, the cells were collected and resuspended in pre-cooled 1× PBS, washed 3 times, and the supernatant was completely discarded. After adding cell lysis buffer (Tris-HCl 50mM pH 8.0, NaCl 150mM, NP40 1%, protease inhibitor 1 tablet / 50mL), place on ice for 30min, centrifuge at 12000rpm for 10min at 4℃, aspirate the supernatant into a clean 1.5mL EP tube, add 15μL agarose beads coupled to Flag antibody, incubate at 4℃ for 2h for immunoprecipitation, centrifuge at 8000rpm for 1min at 4℃, remove the supernatant, wash 3 times with cell lysis buffer without protease inhibitors, add 75μL 1×SDS-PAGE loading buffer to the immunoprecipitated product, boil in water bath for 10min, centrifuge at 4℃ and 8000rpm for 3min, take 15μL supernatant for polyacrylamide gel electrophoresis (SDS-PAGE), electrophoresis at 80V for 30min, adjust the voltage to 120V until bromophenol blue migrates to the bottom of the gel to stop electrophoresis.

[0044] (2) Activate the PVDF membrane with 10 mL of methanol for 10 seconds, wash with deionized water and place in 1× semi-dry transfer buffer (Tris-HCl 24 mM, glycine 5 mM, 20% methanol), then place the SDS-PAGE gel after electrophoresis on the PVDF membrane; place them layer by layer on the transfer apparatus in the order of filter paper-gel-membrane-filter paper from top to bottom, use a pressing rod to remove bubbles between layers, and transfer the membrane at 18V for 2 hours. After the transfer, use TBST containing 5% skim milk powder to block at room temperature for 1 hour, and wash 3 times with 1× TBST, each time for 5 minutes. Incubate with GST-FLAD1 purified protein diluted 1:100 at room temperature for 1 hour, incubate with antibodies (anti-GST, anti-Flag) diluted 1:1000 at room temperature for 1 hour, and wash 3 times with 1× TBST, each time for 5 minutes. Finally, use enhanced chemiluminescence (ECL) and develop with a developer.

[0045] like Figure 2 The results showed that FLAD1 still existed in Flag-NP by Far-Western Blot method. SARS-CoV-2 The immunoprecipitation product showed that the interaction occurred directly between the two.

[0046] 3. Use immunofluorescence DuoLink to confirm the co-localization of FAD synthase FLAD1 and novel coronavirus NP in cells. The specific method is as follows:

[0047] (1) Place a coverslip in a six-well plate to prepare a human lung gland A549 cell slide and infect the cells with SARS-CoV-2.

[0048] (2) After 48 hours, the culture medium was removed, and the cells were washed three times with 1×PBS, and the supernatant was completely discarded. 1 mL of 4% paraformaldehyde was added, and the cells were removed after 15 minutes. The cells were washed three times with 1×PBS, and the supernatant was completely discarded. 1 mL of 0.3% TritonX-100 was added, and the cells were removed after 15 minutes. The cells were washed three times with 1×PBS, and the supernatant was completely discarded. 100 uL of blocking solution was added, and the cells were removed after 1 hour. The cells were washed three times with 1×PBS, and the blocking solution was completely discarded. 100 μL of primary antibody was added (100 ul antibody dilute contains 2 μL of FLAD1 and NP antibodies, respectively), and the cells were removed after 1 hour. The cells were washed three times with 1×PBS, and the primary antibody was completely discarded. 100 μL of probe system was added (100 uL deionized water contains 20 μL of minus and plus, respectively), and the cells were removed after 1 hour. The cells were washed three times with 1×PBS, and the probe system was completely discarded. Add 40μL of the connection system (40ul deionized water containing 1uL of ligase and 8uL of ligation), aspirate it after 30min, wash it 3 times with 1×PBS, and completely discard the connection system. Add 40μL of the amplification system (40ul deionized water containing 0.5uL of polymerase and 8.5uL of amplification), aspirate it after 100min, wash it 3 times with 1×PBS, and completely discard the amplification system. Drop the sealing liquid containing DAPI on the slide, turn the cover glass upside down on the slide, and take pictures with a ZISSE (LSM-800) laser confocal microscope after about 30min.

[0049] like Figure 3 As shown, red fluorescence represents the co-localization of FLAD1 and NP in the cytoplasm, further confirming the interaction between the two at the cellular level.

[0050] 4. Immunoblotting was used to confirm the knockout efficiency of FAD synthase FLAD1. The specific method is as follows:

[0051] (1) Human lung gland A549 (WT), human lung gland A549 (ACE2 OE), and human lung gland A549 (ACE2 OE / FLAD1 KO) cells were passaged simultaneously. After 48 hours, the culture medium was aspirated, and the cells were collected and resuspended in pre-cooled 1× PBS, washed 3 times, and the supernatant was completely discarded. After adding 600uL of cell lysis buffer (Tris-HCl 50mM pH 8.0, NaCl 150mM, NP40 1%, 1 tablet of protease inhibitor / 50mL), it was placed on ice for 30min, centrifuged at 12000rpm for 10min at 4℃, and the supernatant was aspirated into a clean 1.5mL EP tube. The cell lysate was added to 200 μL of 1× SDS-PAGE loading buffer, placed in a boiling water bath for 10 min, centrifuged at 8000 rpm for 3 min at 4°C, and 15 μL of the sample was subjected to polyacrylamide gel electrophoresis (SDS-PAGE). After electrophoresis at 80 V for 30 min, the voltage was adjusted to 120 V until bromophenol blue migrated to the bottom of the gel and electrophoresis was stopped.

[0052] (2) Activate the PVDF membrane with 10 mL of methanol for 10 seconds, wash with deionized water, and place in 1× semi-dry transfer buffer (Tris-HCl 24 mM, glycine 5 mM, 20% methanol). Then place the SDS-PAGE gel after electrophoresis on the PVDF membrane; place them layer by layer on the transfer apparatus in the order of filter paper-gel-membrane-filter paper from top to bottom, use a pressing rod to remove bubbles between layers, and transfer the membrane at 18V for 2 hours. After the transfer, use TBST containing 5% skim milk powder to block at room temperature for 1 hour, and wash 3 times with 1× TBST, each time for 5 minutes. Incubate with primary antibodies (anti-β-actin, anti-FLAD1) diluted at 1:1000, at room temperature for 1 hour, and wash 3 times with 1× TBST, each time for 5 minutes. Incubate with secondary antibodies diluted at 1:1000, at room temperature for 1 hour, and wash 3 times with 1× TBST, each time for 5 minutes. Finally, use the ECL method and develop with a developer.

[0053] like Figure 4 The results shown in the figure showed that after knocking out FLAD1 in A549 cells using CRISPER-Cas9 technology, no FLAD1 band was detected by immunoblotting, proving that the knockout was effective.

[0054] 5. Use fluorescent quantitative PCR to screen the siRNA with the highest efficiency in knocking down FLAD1. The specific method is as follows:

[0055] (1) 8 μL NC siRNA and 8 μL 4 types of FLAD1 siRNA were transfected into human embryonic kidney 293 cells using TransIT X2 transfection reagent. After 48 h, the culture medium was aspirated, and the cells were collected and resuspended in pre-cooled 1× PBS. The cells were washed three times and the supernatant was completely discarded.

[0056] The information of the four FLAD1 siRNAs is shown in Table 1 .

[0057] Table 1 Summary of information of four FLAD1 siRNAs

[0058]

[0059] (2) Refer to Qiagen Extract total RNA from cells according to the instructions of the Mini Kit. Add 350 μL of Buffer RLT to lyse the cells. After mixing, add 350 μL of 70% ethanol, mix thoroughly and add it to the RNeasy MiniSpin Column adsorption column. Centrifuge at 8000 rpm for 1 min and discard the waste liquid. Add 700 μL of Buffer RW1 to the adsorption column, centrifuge at 8000 rpm for 1 min, and discard the waste liquid. Add 500 μL of Buffer RPE to the adsorption column, centrifuge at 8000 rpm for 1 min, discard the waste liquid, and repeat this step. Transfer the adsorption column to a new 2 mL Collection Tube, centrifuge at 13000 rpm for 5 min, discard the waste liquid, transfer the adsorption column to a new 1.5 mL EP tube, add 60 μL of RNase-free water, centrifuge at 13000 rpm for 1 min, and finally obtain total cellular RNA for RNA concentration determination.

[0060] (3) Refer to Promega RT-qPCR was performed according to the 1-Step RT-qPCR System kit instructions. The primer information is as follows: SEQ ID No. 11: FLAD1-F: 5'-TGACCCCTACTCCTGTAGCC-3'; SEQ ID No. 12: FLAD1-R: 5'-TCTGTAGGTCCAGTCCAGCA-3'.

[0061] (4) This experiment was performed on the iQ5 Real Time PCR instrument from Bio-Rad. 1 μL RNA was used to prepare a 20 μL reaction system. The reaction conditions were: 40°C, 15 min; 95°C, 10 min; 95°C, 10 s, 60°C, 30 s (collecting fluorescence signals), 72°C, 30 s; 40 cycles.

[0062] like Figure 5The results showed that after knocking down FLAD1 in human embryonic kidney 293 cells using four siRNAs, the expression level of FLAD1 decreased significantly, proving that the knockdown was effective, among which siRNA-3 had the best efficiency.

[0063] 6. Fluorescence quantitative PCR was used to detect the effect of knocking out FLAD1 on the replication of the new coronavirus. The experimental group was A549 (ACE2 OE) cells with FLAD1 knocked out infected with the new coronavirus (i.e., A549 (ACE2 OE / FLAD1 KO)), and the control group was A549 (ACE2 OE) cells infected with the new coronavirus. The viral genome mRNA level was tested to evaluate viral replication. The specific method is as follows:

[0064] On day 1, A549 cells were seeded in 6-well plates and cultured for 24 h to allow them to adhere.

[0065] On day 2, cells were infected with SARS-CoV-2 viral supernatant.

[0066] On the 3rd day, the supernatant was replaced with a 5% FBS medium. On the 6th and 7th days, 350uL of supernatant was collected, 350uL of Trizol was added, and the cells were frozen at -80°C for later use. On the 8th day, 350uL of supernatant and cells were collected, 350uL of Trizol was added, and the cells were frozen at -80°C for later use.

[0067] Refer to Qiagen Extract total cell RNA according to the instructions of the Mini Kit. Take out the frozen sample, thaw it on ice, add 70% ethanol in equal proportion, mix it thoroughly and add it to the RNeasy Mini Spin Column adsorption column, centrifuge it at 8000rpm for 1min, and discard the waste liquid. Add 700μL Buffer RW1 to the adsorption column, centrifuge it at 8000rpm for 1min, and discard the waste liquid. Add 500μL Buffer RPE to the adsorption column, centrifuge it at 8000rpm for 1min, discard the waste liquid, and repeat this step. Transfer the adsorption column to a new 2mL Collection Tube collection tube, centrifuge it at 13000rpm for 5min, discard the waste liquid, transfer the adsorption column to a new 1.5mL EP tube, add 60μL RNase-free water, centrifuge it at 13000rpm for 1min, and finally obtain the total cell RNA for RNA concentration determination.

[0068] Refer to Promega RT-qPCR was performed according to the 1-Step RT-qPCR System kit instructions.

[0069] The primer sequence information is as follows: SEQ ID No. 13: NSP10-F: 5'-CCCTGTGGGTTTTACACTTAA-3'; SEQ ID No. 14: NSP10-R: 5'-ACGATTGTGCATCAGCTGA-3'.

[0070] This experiment was performed on the iQ5 Real Time PCR instrument from Bio-Rad. 1 μL RNA was used to prepare a 20 μL reaction system. The reaction conditions were: 40°C, 15 min; 95°C, 10 min; 95°C, 10 s, 60°C, 30 s (collecting fluorescence signals), 72°C, 30 s; 40 cycles.

[0071] The results are as follows Figure 6 As shown, compared with the control group A549 (ACE2 OE), the experimental group A549 (ACE2 OE / FLAD1 KO) can be seen that when FLAD1 was knocked out, the replication of the new coronavirus was significantly inhibited.

[0072] Conclusion

[0073] The present invention has discovered a target for the treatment of novel coronavirus infection, which is the flavin adenine dinucleotide (FAD) synthetase FLAD1. Experiments have shown that after knocking out FLAD1 using CRISPER-Cas9 technology, the replication of novel coronavirus in cells is significantly reduced, proving that FLAD1 can effectively inhibit the proliferation of novel coronavirus. The present invention provides a new treatment strategy for the prevention and treatment of severe acute respiratory syndrome caused by novel coronavirus infection.

[0074] The above-mentioned embodiments only express several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the present invention. It should be pointed out that for ordinary technicians in this field, several improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention.

Claims

1. Application of FAD synthetase FLAD1 in the preparation of drugs for preventing or treating novel coronavirus infection.

2. The use according to claim 1, characterized in that: The application is to prepare a drug for preventing or treating novel coronavirus infection using a substance that targets and inhibits FLAD1 expression.

3. The use according to claim 2, characterized in that: The substance for targeted inhibition of FLAD1 expression includes any one of a FLAD1 inhibitor, a FLAD1 siRNA, or a gene editing tool for knocking out FLAD1 expression.

4. The use according to claim 3, characterized in that: The FLAD1 siRNA is any one of (1) to (4): (1) siRNA formed by annealing two single strands as shown in SEQ ID No. 3 and SEQ ID No. 4; (2) siRNA formed by annealing two single strands as shown in SEQ ID No. 5 and SEQ ID No. 6; (3) siRNA formed by annealing two single strands as shown in SEQ ID No. 7 and SEQ ID No. 8; (4) siRNA formed by annealing two single strands as shown in SEQ ID No. 9 and SEQ ID No.

10.

5. A drug for preventing or treating novel coronavirus infection, characterized in that: The drug is FLAD1 siRNA which targets and inhibits the expression of FLAD1.

6. The drug according to claim 5, characterized in that The FLAD1 siRNA is an siRNA formed by annealing two single strands as shown in SEQ ID No. 7 and SEQ ID No. 8.

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