My at-home SARS-CoV-2 antibody test result

recently i had a false positive pcr test result for sars cov2 i followed it up with a rapid at-home antibody test for soros cov2 in this video i'll explain how these rapid antibody tests work and what the results mean for me i'm vincent dracheniello and recently i had a false positive pcr test for sars co v2 you can see the video i made about that it's linked above here it'll explain what the results meant and how i thought it was a false positive result there's still a faint possibility that i actually was at the end of a asymptomatic infection which is why my ct value for the pcr test was low so to address that issue i decided to do an at-home rapid antibody test and this would check for antibodies to sars covi2 virus particles and i was sent this test by a company who's developing the test and i would like to show you how it works i'll then show you how it was done what my result was and what it means first let's take a look at what it means to have an immune response after an infection with any virus in this slide i am showing an immune response on the y-axis with time after infection so we're looking at either antibodies or t cells in an individual when you get your first infection sometime between 7 and 14 days you generate an antibody and a t cell response against the virus once that infection is cleared the immune response is then declined to some low level which protects you from subsequent infection now we can measure the presence of antibodies in our blood quite easily with at home tests these are called lateral flow assays and that's the sort of test that i did on myself and i want to now explain to you how it works it all starts with a drop of blood which contains the antibodies that you produce when you're infected when these antibodies are first produced the very first ones are a type of antibody called igm those are later replaced with antibodies of a type called igg and the igm antibodies eventually go away so looking for igm and igg antibodies is a way to tell whether you're early in an infection or much later okay what's a lateral flow assay those of you who have taken pregnancy tests are familiar with this it is a very simple device you put a sample and it reads out a result in this case this is a pregnancy test which has at one end an absorbent pad you put urine on that the urine flows by capillary action through the device and in a way which we'll describe in a minute the device shows lines depending on whether you have certain protein in your urine which is indicative of pregnancy so you can see in this test a single line means you're not pregnant but that single line means the assay has worked it's a control line if you have two lines it means you're pregnant because that second line means the assay is picking up the protein in your urine which indicates that you're pregnant in a similar way we can look for antibodies this is actually an antigen test we're looking for a protein we can also look for antibodies that are produced during virus infection and that is the basis for the test that i did on myself so here is a diagram of a lateral flow assay to detect viral antibodies this graphic illustrates one way of designing a lateral flow assay there are certainly other ways that it can be done and i don't actually know that this represents how the kit that i used actually functions but the basic principles are the same and this will serve to illustrate how the assay works it's constructed on a pad which is covered with different pieces of absorbent material and you typically would add your blood to one end of the pad this is all encased in a plastic container of course and then the blood components move from left to right by capillary flow and along the way the reactions take place and that's why it's called a lateral flow assay because the material you put on one end flows laterally to the other end now if we start with blood and we're looking for antiviral antibodies this could be a mixture of igm or igg antibodies and i've given them two different colors i'm pretty sure the igm or the magenta i'm pretty sure i did that on purpose so i would remember igm and igg so you put a drop of blood on the sample pad and then the fluid begins to move to the right by capillary flow it then passes this first pad which contains the reagents that are going to give you a readout and they include gold anti-rabbit igg conjugate this is the control material these are antibodies against rabbit igg and they're going to be involved in the reaction later on they're coupled to gold particles and that is one way to make a line on the rapid flow assay that is a line that you can see also on this pad are gold particles those are the yellow circles conjugated to the viral protein or the viral antigen and it's that antigen whose antibodies you're looking for so in the case of these rapid lateral flow assays to detect saurus cov2 antibodies they're typically looking for antibodies to the spike glycoprotein so we would put the spike protein conjugated to gold beads on this pad here so as the blood is put on the sample pad it moves across this first reagent pad here and it picks up these reagents and then the the sample is going to move towards three different zones uh one zone where there are antibodies to human igm placed they're linked to the pad a second where we have antibodies to human igg and a third where we have anti-rabbit antibodies and so i think you can see right away that each of these is going to be picking up a different kind of antibody the yellow will pick up human igm antibodies the blue will pick up human igg antibodies and the green will pick up the rabbit antibodies that have the gold and that's the control for our reaction to make sure that everything works because here is a anti-rabbit igg and we're going to see if we can pick those up by these anti-rabbit antibodies so again you put the blood at the left it begins to flow to the right it picks up the reagents and then moves on so the next step is shown here now we have picked up the viral antigen gold complexes here both an igg and an igm antibody have reacted with those proteins and of course here's the rabbit gold antibody as well of course if you're very early in infection you would only have igm antibodies if you're very late you would have igg only and if you're somewhere in the middle you could have both the next step is the final step where you read out the lines all the way on the right is our control line so we have the rabbit antibodies that are conjugated to gold they're reacting with anti-rabbit igg that gives you a line the line again is formed by the gold particles that tells you the assay is working then if you have igg antibodies these antibodies that are stuck to the pad these are anti igg antibodies so they're pulling down or holding igg antibodies which are then in turn coupled to sars cov2 viral spike protein or whatever protein you're looking for of course you can have igg molecules that are not reacting with spike in your blood and these would be bound by the anti-igg antibodies on the pad but they wouldn't give you a line because they wouldn't be binding to gold via the viral protein so that's our line for igg and then of course igm antibodies will be grabbed by the anti-igm antibodies on the pad and if they have the viral protein coupled to the gold sphere which again was put on the reagent pad we'll get a line showing up here so that's how the assay works it's relatively straightforward in its concept not so easy to make so that it works properly and this is something that can be done at home using just a drop of blood you can also design a lateral flow assay for viral protein if you want to look in the course of an infection to actually see if you're infected not just if you're making antibodies but if you have viral proteins present you can do a lateral flow assay for viral proteins so here it's illustrated using your clinical sample could be blood could be a nasal wash which has viral antigens it's put on the sample pad this moves past a reagent pad which contains antibodies to your antigen coupled to gold will then move across the the wicking pad by capillary flow and you see now that our viral antigen in red has been picked up by these reagent antibodies and then finally they will these antibodies will be bound on the test line in this case the antibodies attached to the matrix are actually antibodies to the viral protein so they are binding the viral protein which is in turn is already bound to the antibody to the protein coupled to gold and that'll give you a line and of course we have a controlled test line which shows that the assay is working uh in this case these are antibodies to the igg so that's how the lateral flow assay for either antibodies to viral proteins or for viral proteins works let me now show you how i did the assay on my sample as you can see these kits are still in development there's handwriting on the lateral flow cassette for example and it hasn't yet been assembled into its final form so i received as part of this kit two lateral flow cartridges as you can see here together with lancets to pierce your finger and a little pipette and so all i did was to take the end off of the lancet the the lancet or the needle is buried in there it's got a spring in it that juts into your finger it makes a little hole blood comes out you take one of the pipettes and you draw the blood up to a line it takes a little bit of squeezing to get the blood up to that line and then you put the blood in the sample pad on the lateral flow cassette as you can see here you then put a drop of buffer which helps to wick or move the sample by capillary action to the remainder of the cassette and here's the result that i got so you can see at the bottom is the sample pad where i initially put the blood when i added the buffer the sample then moved through the reagent region where it picks up the reagents that we talked about earlier and then the three areas of the pad with antibodies bound to them the igm region the igg region and the control region so you can see this is the result from my assay assay worked because you can see a line at the control but there are neither igg nor igm antibodies to sars kovi 2 spike protein so what does this mean for me this means that i have no antibodies to sars cov2 spike protein that could mean that i was never infected with sars cov2 and therefore my false positive pcr was in in reality a false positive and not the end of a asymptomatic infection however there are some caveats of course rapid at home lateral flow antibody tests are not perfect they can have both false positives but in our case the relevant part would be a false negative in other words maybe i was infected and i do have antibodies but the essay is not picking it up now to address that you can repeat the assay and i took another blood sample and used the other cassette and repeated it and it was also negative ideally one would have a different assay altogether not all of us have access to that so i'm confident saying that i was never infected with source cov2 i have no antibodies to the virus my initial false positive pcr was indeed a false positive pcr and not the end of an asymptomatic infection i hope that helps you to understand how these lateral flow assays work the one that i used is under development it's not yet available it's not yet been approved but at some point soon assays like this one will be available for us to test our antibodies at home and as you saw from my demonstration it's not very hard to do i'm vincent raqueniello and i'm earth's virology professor you

Channel: MicrobeTV

Views: 55,335

Keywords: virus, viruses, viral, virology, SARS-CoV-2, COVID-19, coronavirus, pandemic, antibody, lateral flow assay, at home diagnostic test

Id: HvXCISbrK9Q

Length: 14min 16sec (856 seconds)

Published: Wed Dec 09 2020