Neutralization test

The Neutralization Test is based on the determination of the infectivity of the virus and the ability of the immune serum to neutralize the virus based on the comparison of the residual infectivity of the virus after neutralization by the immune serum. When an animal is infected with a virus, a specific neutralizing antibody is produced in the body and specifically binds to the corresponding virion, thereby preventing the virus from adsorbing to the sensitive cell or inhibiting its invasion, so that the virus loses its ability to infect. Basic Information Specialist classification: Infectious disease examination and classification: immunological examination Applicable gender: whether men and women apply fasting: not fasting Analysis results: Below normal: Normal value: no Above normal: negative: Less than 10 is negative and no virus. 10 to 49 are suspicious. Positive: Generally, a neutralization index greater than 50 is considered positive, and a virus is present. Tips: Pay attention to normal eating habits and pay attention to personal hygiene. Normal value Fixed serum dilution virus method: For viruses, usually the neutralization index is greater than 50, and 10 to 49 are suspicious, and less than 10 is negative. Neutralization test normal value: the human body is in a dynamic equilibrium and healthy state. Clinical significance This test is mainly used to detect antibodies from the serum to be tested, or to detect viruses from the disease material, thereby diagnosing viral infections; 2 to check the toxins in the materials with anti-toxin serum or to identify the type of toxins in the bacteria; Viral serum or anti-toxin titer; 4 Identification and typing of newly isolated viruses, neutralization test can be carried out not only in susceptible experimental animals, but also on cell culture or chicken embryos. The test methods mainly include simple qualitative test, fixed serum dilution virus method, fixed virus dilution serum method, and plaque reduction method. Positive results may be diseases: mumps, AIDS, dengue fever, Japanese encephalitis, Coxsackie virus rash, foot and mouth disease, rabies precautions Forbidden before examination: Pay attention to normal eating habits and pay attention to personal hygiene. Requirements for inspection: Actively cooperate with the doctor. Inspection process (1) Simple qualitative neutralization test This method is mainly used to detect the virus in the disease material, and can also be initially identified or finalized. Test animals (or chicken embryos, cell culture) and routes of inoculation are first selected based on viral susceptibility. The material is ground and diluted to a certain concentration (about 100 LD50 ~ 1000 LD50 or TCID50). Contaminated materials need to be added antibiotics (200 to 1000 units of penicillin and streptomycin), or filtered with a bacterial filter, mixed with known antiserum (appropriately diluted or not diluted), and diluted with normal serum For comparison. After mixing, the cells were inoculated at 37 ° C for 1 h, and at least 3 animals in each group. Isolation feeding, observation of morbidity and mortality. The control animals died, while the animals in the neutralization group did not die, which confirmed that the disease contained the virus corresponding to the antiserum. This method can also be used for the identification and typing of toxins (such as toxins). (2) Fixed serum dilution virus method In this method, the virus was diluted 10-fold in increments, and two tubes were placed, the first column was added with normal serum (control group), and the second column was added with serum to be tested (test group). After mixing, the cells were inoculated at 37 ° C for 1 h, and each tube mixture was inoculated separately into the selected test animals, and 3 to 5 animals were used for each dilution. After inoculation, observe daily and record the number of deaths. After the observation, calculate the LD50 and neutralization index (Table 7-1, Table 7-2). This method is applicable to the detection of a large number of samples. This method is mostly used to detect neutralizing antibodies in the serum to be tested. For viruses, the neutralization index is usually greater than 50 and is positive, 10 to 49 is suspicious, and less than 10 is negative. (3) Fixed virus dilution serum method This method is used to determine the neutralization price of antiviral serum. The serum to be tested is diluted 2 times, and the virus solution with the same toxic value is added (mixed with serum, each dose contains virus 100LD50), shake well. The test animals were inoculated at 37 ° C for 1 h. Note: [1] Inoculation dose 0.1 ml, containing virus 100LD50. [2] refers to the dilution after mixing with the virus. [3] The denominator is the number of inoculations, and the numerator is the number of protection. [4] PD50 is half-protection, and its calculation method is the same as LD50 calculation. (4) plaque reduction method The virus neutralization test was carried out on cell culture, and in recent years, the plaque reduction method was frequently used. First, the virus is diluted to an appropriate concentration, so that 80 to 100 PFU (plaque forming unit) per 0.2 ml is mixed with the different dilutions of the serum to be tested, and placed at 37 ° C for 1 h to 2 h to measure PFU, respectively. A 50% serum dilution of the plaque is the neutralization price of the serum. See Table 7-4. Table 7-4 Example of neutralization test for plaque reduction method Note: [1] Serum was diluted in 4 fold increments. [2] The plaque is reduced by 50% of the serum dilution, and the calculation method is the same as the calculation of LD50. Not suitable for the crowd People with reduced hematopoietic function such as leukemia, various anemia, myelodysplastic syndrome, or people with thrombocytopenia should pay attention to blood draw, and should not take more or more blood. Adverse reactions and risks 1. After the blood is drawn, do not press the needle hole to avoid subcutaneous hematoma. If there is a small piece of bruise in the blood, it is slightly tender, please don't panic, you can do hot compress after 24 hours to promote the absorption of blood. The general small amount of congestion will gradually absorb in 3 to 5 days and the color will become lighter and return to normal. 2. After the blood draw, symptoms such as dizziness, vertigo, fatigue, etc. should be immediately supine, drink a small amount of syrup, and then undergo a physical examination after the symptoms are relieved.

The material in this site is intended to be of general informational use and is not intended to constitute medical advice, probable diagnosis, or recommended treatments.