Neutralization Test for Virus

NEUTRALIZATION TEST FOR computer computer virus Neutralization of a virus is delimitate as the loss of infectivity through chemical reaction of the virus with specific antibody. Virus and blood serum atomic number 18 mixed under usurp condition and consequently inoculated into cell finale, egg or animals. The presence of unneutralized virus may be detected by reactions much(prenominal) as CPE, haemadsorption/haemagglutination, plaque formation, disease in animals. The loss of infectivity is bought about by burden by the bound Ab with any one of the steps leading to the blowhole of the viral genome into the waiter cells.There atomic number 18 2 types of neutralization reaction- Reversible neutralization The neutralization process can be reverse by diluting the Ab-Ag mixture within a short snip of the formation of the Ag-Ab complexes (30 mins). It is persuasion that reversible neutralization is due to the interference with fond regard of virions to the cellular receptors eg. the attachment of the HA protein of influenza viruses to sialic acid. The process requires the saturation of the fall out of the virus with Abs.Stable neutralization with time, Ag-Ab complexes usually croak more stable (several hours) and the process cannot be reversed by dilution. Neither the virions nor the Abs are permanently changed in stable neutralization, for the idempotent components can be recovered. The neutralized virus can be reactivated by proteolytic cleavage. Stable neutralization has a unlike mechanism to that of reversible neutralization. It had been shown that neutralized virus can attach and that already given virions can be neutralized.The number of Ab molecules required for stable neutralization is considerably smaller than that of reversible neutralization, Kinetic certainty shows that even a single Ab molecule can neutralize a virion. Such neutralization is generally produced by Ab molecules that establish contact with 2 antigenic sites on different monomers of a virion, greatly increasing the stability of the complexes. An warning of stable neutralization is the neutralization of polioviruses, whereby, the attachment of the antibody to the viral capsid stabilizes the capsid and inhibits the uncoating and electric receptacle of viral nucleic acid.Viral evolution must(prenominal) head for the hills to select for mutations that change the antigenic determinants involve in neutralization. In contrast, other antigenic sites would tend to remain unchanged because mutations bear on them would not be selected for and could even be detrimental. A virus would thus prepare from an legitimate type to a transformation of types, different in neutralization (and sometimes in HI) interrogatorys, but retaining some of the original mosaic of antigenic determinants recognizable by CFTs.Because of its high immunological specificity, the neutralization test is often the standard against which the specificity of the other serolo gical techniques is evaluated. Before the neutralization test is carried out, the know components that are to be utilize must be standardized. To identify a virus isolate, a cognise pretitred antiserum is used. Conversely, to measure the antibody reply of an individual to a virus, a cognise pretitred virus is used. To titrate a known virus, serial tenfold dilutions of the isolate is disposed(p) and inoculated into a susceptible host system such as cell finale or animal.The virus terminus titre is the reciprocal of the highest dilution of virus that infects 50% of the host system eg. 50% of cell cultures civilize CPE, or 50% of animals develop disease. This conclusion dilution contains one 50% tissue culture infecting dose (TCID50) or one 50% lethal dose (LD50) of virus per unit volume. The concentration of virus generally used in the neutralization test is coulomb TCID50 or 100 LD50 per unit volume. The antiserum is titrated in the neutralization test against its homologo us virus.Serial ternary dilutions of serum is prepared and mixed with an fit volume containing 100TCID50 of virus. The virus and serum mixtures are incubated for 1 hour at 37oC. The time and temperature for incubation varies with different viruses. The mixtures are then inoculated into a susceptible host system. The endpoint titration contains one antibody unit and is the reciprocal of the highest dilution of the antiserum protect against the virus. Generally 20 antibody units of antiserum is used in the neutralization tests.