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    MinION Sequencing protocol for Rabies virus of Arctic lineage

    pramadaprasad, Harsha P.K., Chitra Pattabiraman

    Published: 2023-01-11 DOI: 10.17504/protocols.io.3byl4jzb8lo5/v1
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    Abstract

    An ONT MinION-based sequencing protocol to retrieve whole genomes of Rabies virus of the Artic lineage. Primers were selected using PrimalScheme (http://primalscheme.com/) and theprotocol was modified from the Zika and SARS-CoV-2 sequencing protocols using the same tool.

    Steps

    RNA Extraction

    1.

    Extract and purify RNA from Brain tissue homogenate using .

    Note
    Removal of genomic DNA by on column DNase treatment (optional)Genomic DNA can be removed by on column DNase I (RNase-free) - 5,000 units treatment for 30 min at room temperature before the wash steps.

    cDNA Preparation

    2.

    Note
    Extracted RNA samples are mixed thoroughly by brief vortex and spin down to collect all liquid at the bottom.

    2.1.

    Prepare the master mix for cDNA Prep as follows in a PCR plate/ tubes for 10μL reaction.

    AB
    ComponentVolume
    Lunascrpit RT Supermix (5X)2µl
    Template8µl
    Total10µl

    Note
    Prepare all reagents in a biosafety cabinet designated for clean work.

    2.2.

    Incubate the reaction mix following the conditions mentioned below in a thermo cycler:

    25°C for 00:02:00

    55°C for 00:10:00

    95°C for 00:01:00

    Hold at 4°C

    Amplicon PCR

    3.

    Primers are designed using Primal Scheme. Resuspend the lyophilized oligos fully in Nuclease free water / 1X TE to a concentration of 100µM, vortex thoroughly,Nuclease-free, and spin down.

    RABV_Arctic_primers.csv

    4.

    Separate odd and even primer sets. Add 5µl of each odd primer to a 1.5mL LoBind tube labelled Pool 1. Repeat the same for all even primers for Pool 2. These are the 100µM stocks of each primer pool.

    5.

    Dilute 100µM stock pools (1:10) in Nuclease free water, to generate 10µM primer stock. A final concentration of 15 nM per primer is used. Here we use a total of 39 primers in Pool 1 and 39 primers in Pool 2. Here 0.75µl of per primer pool (10µM) is required for a 25µl reaction.

    6.

    Set up two PCR reactions per sample (for Pool 1 and 2) as follows in tubes or plates. Mix by gentle pipetting and pulse spin to collect liquid at the bottom.

    ABC
    ComponentReaction Mix 1Reaction Mix 2
    5X Q5 Reaction Buffer5µL5µL
    10 mM dNTPs0.5µL0.5µL
    Q5 Hot Start DNA Polymerase0.25µL0.25µL
    Pool 1 (10µM)0.75µL0µL
    Pool 2 (10µM)0µL0.75µL
    Nuclease-free water18.5µL18.5µL
    7.

    Add 2.5µl cDNA to each of the PCR reactions, mix by gentle pipetting and spin the tube to collect all liquid at the bottom of the tube.

    8.

    Set up the following PCR conditions in the thermal cycler.

    Stage °C Cycles

    Heat Activation 98 °C 00:00:30 1

    Denaturation 98 °C 00:00:15 25-35

    Annealing 65 °C 00:05:00 25-35

    Hold 4 °C Indefinite 1

    Citation
    Quick J, Grubaugh ND, Pullan ST, Claro IM, Smith AD, Gangavarapu K, Oliveira G, Robles-Sikisaka R, Rogers TF, Beutler NA, Burton DR, Lewis-Ximenez LL, de Jesus JG, Giovanetti M, Hill SC, Black A, Bedford T, Carroll MW, Nunes M, Alcantara LC Jr, Sabino EC, Baylis SA, Faria NR, Loose M, Simpson JT, Pybus OG, Andersen KG, Loman NJ 2017 Multiplex PCR method for MinION and Illumina sequencing of Zika and other virus genomes directly from clinical samples. Nature protocols http://doi.org/10.1038/nprot.2017.066

    PCR clean-up

    9.

    Label the tubes/plates and pool the PCR reactions for each samples into a single LoBind tube .

    AB
    PCR pool 125µL
    PCR pool 225µL
    Nuclease Free water0µL
    Total50µL

    Note
    When higher viral loads are anticipated based on Ct values < 20 then reduce the amount of amplicons to 15-20µL each and make up the volume to 50µl with Nuclease free water.

    10.

    Clean-up the amplicons using .

    Thaw the AMPure beads to room temperature and vortex thoroughly to ensure that the beads are well suspended/ until the solution is uniformly brown in colour.

    10.1.

    Add 0.4x volume (0.4:1) of AMPure beads to the sample tube and mix gently by either flicking or pipetting. For example add 20,µl AMPure beads to a 50 µl reaction.

    10.10.

    Quantify 1µl product using the Qubit Fluorometer using the .

    10.2.

    Spin the tubes to collect entire liquid at the bottom and incubate the tubes at room temperature for 00.05.00.

    10.3.

    Place the tubes on magnetic stand and incubate for 00:02:00 or until the beads have settled and the supernatant is completely colourless.

    10.4.

    Carefully remove and discard the supernatant, without disturbing the bead pellet.

    10.5.

    Add 200µl of 70% ethanol or enough to cover the pellet and wait for 30s.Carefully remove and discard ethanol delicately without disrupting the bead pellet.

    10.6.

    and repeat Spin to collect all liquid at the bottom of the tube and carefully remove as much residual ethanol as possible.

    10.7.

    Incubate the tube with open lid for 00:00:30 or until the pellet is dried (if the pellet dries completely it will crack and become difficult to resuspend)

    10.8.

    Resuspend pellet in 30µl Elution Buffer (EB), mix gently by either flicking or pipetting and incubate for 00:02:00.Make sure that the pellet is completely resuspended.

    10.9.

    Place on magnetic stand and transfer sample to a clean 1.5mL LoBind tube ensuring no beads are transferred into this tube.

    End-Prep Reaction

    11.

    In a new PCR plate/ tubes set up the following reaction for each sample. Prepare Master mix and aliquote it into tubes . If the Qubit reading is > 15ng/ul ,

    AB
    ComponentVolume
    PCR dilution from previous step3.3µL
    Ultra II End Prep Reaction Buffer1.2µL
    Ultra II End Prep Enzyme Mix0.5µL
    Nuclease-free water5µL
    Total10µL

    If the Qubit reading is 5ng/ul -15ng/ul

    AB
    ComponentVolume
    PCR dilution from previous step5µL
    Ultra II End Prep Reaction Buffer1.2µL
    Ultra II End Prep Enzyme Mix0.5µL
    Nuclease-free water3.3µL
    Total10µL

    If the Qubit reading is <5ng/ul,

    AB
    ComponentVolume
    PCR dilution from previous step8.3µL
    Ultra II End Prep Reaction Buffer1.2µL
    Ultra II End Prep Enzyme Mix0.5µL
    Nuclease-free water0µL
    Total10µL

    11.1.

    Reaction conditions for End Prep:

    Incubate

    25°C for 00:15:00

    65°C for 00:15:00

    On ice for 00:01:00

    Native Barcoding

    12.

    In a new labelled tube/plate prepare the following components.

    AB
    ComponentVolume
    End-preparation reaction mixture0.75µL
    NBXX barcode1.25µL
    Blunt/TA Ligase Master Mix5µL
    Nuclease-free water3µL
    Total10µL

    12.1.

    Incubate at

    25°C for 00:20:00

    65°C for 00:10:00

    On ice for 00:01:00

    12.10.

    Resuspend pellet in 30µl Elution Buffer(EB), mix gently by either flicking or pipetting and incubate for 00:02:00.

    12.11.

    Place on magnet stand and transfer sample to a clean 1.5mL Eppendorf tube ensuring no beads are transferred into this tube.

    12.12.

    Quantify 1µl of the barcoded amplicons using the Qubit Flurometer.

    Equipment

    ValueLabel
    QubitNAME
    FlurometerTYPE
    InvitrogenBRAND
    Q33228SKU
    12.2.

    In a new 1.5mL LoBind tube pool all barcoded reactions together.

    12.3.

    Add 0.4x volume of AMPure beads to the sample tube and mix by either flicking or gentle pipetting. For example add 96µl AMPure beads to 240µl pooled barcoding reactions.

    12.4.

    Briefly vortex and mix the reactions and incubate at room temperature for 00.05.00.

    12.5.

    Place on magnetic stand and incubate for 00:02:00 or until the beads have pelleted and the supernatant is completely clear. Carefully remove and discard the supernatant, being careful not to touch the bead pellet.

    12.6.

    Remove the tube from the magnetic stand and add 200µl SFB and resuspend beads completely using pipette. Spin down to collect liquid at the bottom of the tube and place on the magnetic stand. Remove supernatant and discard.

    12.7.

    Add 200µl of 70% ethanol to wash the pellet. Carefully remove and discard ethanol, being careful not to touch the bead pellet.

    12.8.

    Spin to collect all liquid at the bottom of the tube and carefully remove as much residual ethanol as possible.

    12.9.

    With the tube lid open incubate for 00:00:30 or until the pellet is dried (if the pellet dries completely it will crack and become difficult to resuspend).

    Adapter Ligation

    13.

    Prepare the following reaction for AMII Adapter ligation in a PCR tube.

    AB
    ComponentVolume
    Barcoded amplicon pool30µL
    NEBNext Quick Ligation Reaction Buffer (2X)40µL
    Adapter Mix (AMII)5µL
    Quick T4 DNA Ligase5µL
    Total80µL
    13.1.

    Incubate at 25°C for 00:20:00, possibly in a thermo cycler.

    Post adapter ligation Clean-up

    14.

    Add 80µl (1:1) of AMPure beads to the sample tube and mix gently by either flicking or pipetting. Spin to collect all liquid at the bottom of the tube.

    14.1.

    Incubate for 00:05:00 at room temperature.

    14.2.

    Place on magnetic rack and incubate for 00:02:00 or until the beads have pelleted and the supernatant is completely clear. Carefully remove and discard the supernatant, being careful not to touch the bead pellet.

    14.3.

    Add 200µl SFB and resuspend beads completely by pipette mixing. Brief spin to collect all liquid at the bottom of the tube. Remove supernatant and discard.

    14.4.

    Repeat step 14.3 to perform a second SFB wash.

    14.5.

    Brief spin and remove any residual SFB. Add 15µl EB (ONT) and resuspend beads by gentle flicking or pipette mixing.

    14.6.

    Incubate at room temperature for 00:02:00 and place on magnetic stand until clear. Transfer final library to a new 1.5mL LoBind tube

    14.7.

    Quantify 1µl of the barcoded amplicons using the Qubit Fluorometer.

    Equipment

    ValueLabel
    QubitNAME
    FlurometerTYPE
    InvitrogenBRAND
    Q33228SKU

    Flow cell Priming and Sequencing

    15.

    Thaw the following reagents.

    Sequencing buffer (SQB)

    Loading beads (LB)

    Flush buffer (FB)

    Flush tether (FLT)

    15.1.

    Add 30µl FLT to the FB tube and mix well by vortex and spin down.

    15.2.

    Prepare the following library dilution for sequencing in a LoBind tube:

    AB
    SQB37.5µL
    LB25.5µL
    Library12-14µL
    Total75-80µL

    15.3.

    Flowcell Priming, loading of the library and sequencing are performed based on the following protocol:

    dx.doi.org/10.17504/protocols.io.bbmuik6w

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