Ebook Ebola and marburg virus (2nd edition): Part 2
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Ebook Ebola and marburg virus (2nd edition): Part 2
----------------------------------------------- https://khothuvi .com6Methods of Detection and TreatmentHistorically, scientists have measured infecti Ebook Ebola and marburg virus (2nd edition): Part 2ion with filoviruses using tests that detect antibodies to the virus. In fact, scientists use several different tests, with varying degrees of sensitivity (ability to correctly identify positive samples) and specificity (ability to correctly identify negative samples). One common test is called the Ebook Ebola and marburg virus (2nd edition): Part 2indirect fluorescence assay (IFA). A schematic of this test is shown in Figure 6.1. In short, scientists apply cells known to be infected with the EboEbook Ebola and marburg virus (2nd edition): Part 2
la virus to a slide. They then add serum (the liquid portion of the blood, which contains antibodies) from a suspected patient and allow it to dry. Th----------------------------------------------- https://khothuvi .com6Methods of Detection and TreatmentHistorically, scientists have measured infecti Ebook Ebola and marburg virus (2nd edition): Part 2h is often derived from goats) is conjugated (linked) to a protein called fluorescein. When antibodies to Ebola or Marburg are present in the patient’s sample, they will bind to the virus or virus particles on the slide. The fluorescein-labeled secondary antibody will then bind to the primary antibo Ebook Ebola and marburg virus (2nd edition): Part 2dies. Scientists then view the slide under a fluorescent microscope. Samples that are positive will glow a bright green or yellow color (see Figure 6.Ebook Ebola and marburg virus (2nd edition): Part 2
2).One problem with IFA, however, is the fact that both its sensitivity and its specificity are fairly low. Therefore, the test may miss samples that ----------------------------------------------- https://khothuvi .com6Methods of Detection and TreatmentHistorically, scientists have measured infecti Ebook Ebola and marburg virus (2nd edition): Part 2ests are based on the same principle of antigen, primary antibody, and secondary58Methods of Detection and Treatment 59Indirect Fluorescent Antibody TestAdd Ebola infected cellsAdd patient serum samples. Antibodies to Ebola (Y), when present, will stick to cells.Add second antibody (Y), which binds Ebook Ebola and marburg virus (2nd edition): Part 2to first antibody and carries a fluorescent tag.Patient 1 Patient 2View slide under fluorescent microscopePatient 1 is positive for Ebola antibody, meEbook Ebola and marburg virus (2nd edition): Part 2
aning they were previously exposed to the disease. Patient 2 is negative and has not been exposed.o Infobase PublishingFigure 6.1 Schematic representa----------------------------------------------- https://khothuvi .com6Methods of Detection and TreatmentHistorically, scientists have measured infecti Ebook Ebola and marburg virus (2nd edition): Part 2SFigure 6.2 Indirect fluorescent antibody test. A positive sample (one that contains antibody against the target organism, such as the Ebola virus) will bind to infected cells on the glass slide. The secondary antibody, coupled with a protein fluorescein, will attach to the primary antibody, and wil Ebook Ebola and marburg virus (2nd edition): Part 2l fluoresce under ultraviolet light as seen in this figure. (Centers for Disease Control and Prevention)antibody. However, the type of protein that isEbook Ebola and marburg virus (2nd edition): Part 2
conjugated to the secondary antibody, the method of development, and visualization of results differ.Scientists also use ELISA (enzyme-linked immunos----------------------------------------------- https://khothuvi .com6Methods of Detection and TreatmentHistorically, scientists have measured infecti Ebook Ebola and marburg virus (2nd edition): Part 2ecognized by the host immune system) in tiny plastic wells and allow them to dry. Similar to the IFA, they then apply sera from patients, before a secondary antibody is applied. In this case, however, this secondary antibody is often coupled to a molecule called horseradish peroxidase. Scientists th Ebook Ebola and marburg virus (2nd edition): Part 2en add a substrate (in this situation, a chemical that would interact with the horseradish peroxidase) containing a colored dye couMethods of DetectioEbook Ebola and marburg virus (2nd edition): Part 2
n and Treatment 61pled with peroxide. The peroxidase cleaves (cuts) the substrate, resulting in the release of colored molecules. The intensity of col----------------------------------------------- https://khothuvi .com6Methods of Detection and TreatmentHistorically, scientists have measured infecti Ebook Ebola and marburg virus (2nd edition): Part 2nsitive and specific than I FA, but because a special reader is necessary to determine the results, it is a more difficult test to carry out in the field.These tests can also be used to distinguish between a current or very recent infection and a past infection. The human body produces several diffe Ebook Ebola and marburg virus (2nd edition): Part 2rent types of antibodies (technically called immunoglobulins, abbreviated Ig). These different types are known as IgG, IgM, IgA, IgE, and IgD. The mosEbook Ebola and marburg virus (2nd edition): Part 2
t important antibodies for diagnosing Ebola are IgM and IgG. If a secondary antibody specific to human IgM is used, a current or very recent Ebola inf----------------------------------------------- https://khothuvi .com6Methods of Detection and TreatmentHistorically, scientists have measured infecti Ebook Ebola and marburg virus (2nd edition): Part 2 IgM to producing IgG.Scientists recently developed a new immunological test for filoviral infection. Rather than using patient sera, this test uses skin samples from patients suspected of infection. Skin samples are placed in a chemical called formalin. This kills the viruses, making the samples sa Ebook Ebola and marburg virus (2nd edition): Part 2fe to work with in the absence of biosafety level 4 (BSL-4) facilities. The general procedure, however, is quite similar to the assays previously descEbook Ebola and marburg virus (2nd edition): Part 2
ribed.PCR-BASED METHODS OF DETECTIONImmunological methods are most useful for detecting past infection with the Ebola or Marburg viruses. They can det----------------------------------------------- https://khothuvi .com6Methods of Detection and TreatmentHistorically, scientists have measured infecti Ebook Ebola and marburg virus (2nd edition): Part 2ents with a current infection may not be producing antibodies. A test to detect these specific antibodies will be negative, even when the patient is, indeed, infected with a filovirus. In addition, an antibody response is not immediate. Detectable levels of IgM take several days to develop. A test p Ebook Ebola and marburg virus (2nd edition): Part 2erformed too soon may appear falsely negative. An IgG response takes even62 EBOLA AND MARBURG VIRUSESlonger. It can take two weeks or longer for a patEbook Ebola and marburg virus (2nd edition): Part 2
ient to produce enough IgG to detect in an IFA or ELISA.PCR (polymerase chain reaction)-based tests eliminate the antibodies. These tests directly det----------------------------------------------- https://khothuvi .com6Methods of Detection and TreatmentHistorically, scientists have measured infecti Ebook Ebola and marburg virus (2nd edition): Part 2ly sensitive and specific. There are shortcomings, however, with this technique as well. Filoviruses are RNA viruses, and RNA is an unstable molecule that degrades rapidly if not handled correctly. Even proteins on our hands (called RNAses) can destroy any RNA that may be present in a sample. In a f Ebook Ebola and marburg virus (2nd edition): Part 2ield environment, such as rural Africa, material handling obviously poses a problem.While degradation of the sample RNA may produce a false negative rEbook Ebola and marburg virus (2nd edition): Part 2
esult, false positives are possible due to sample contamination. PCR is a very sensitive procedure. Essentially, the amount of virus RNA present in a ----------------------------------------------- https://khothuvi .com6Methods of Detection and TreatmentHistorically, scientists have measured infecti Ebook Ebola and marburg virus (2nd edition): Part 20 to 40 times. If even a miniscule amount of contamination is present—as little as just a few viral particles carried into the sample by the air or present on a contaminated glove or counter top, these will be amplified in the reaction—thus producing a false positive result. Therefore, precautions n Ebook Ebola and marburg virus (2nd edition): Part 2eed to be taken to minimize this contamination. Once again, specialized machines and chemicals are necessary to carry out this procedure, making it diEbook Ebola and marburg virus (2nd edition): Part 2
fficult to perform in rural areas.METAGENOMICSA newer molecular method that has been employed for filovirus detection is called metagenomics. In this ----------------------------------------------- https://khothuvi .com6Methods of Detection and TreatmentHistorically, scientists have measured infecti Ebook Ebola and marburg virus (2nd edition): Part 2e may be taken and sequenced, which would include the host genome sequence (from the blood cells present) and alsoMethods of Detection and Treatment 63Polymerase Chain Reaction Ebook Ebola and marburg virus (2nd edition): Part 2----------------------------------------------- https://khothuvi .com6Methods of Detection and TreatmentHistorically, scientists have measured infectiGọi ngay
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