In immunology, seroconversion is the development of specific antibodies in the blood serum as a result of infection or immunization, including vaccination.[1] [2] During infection or immunization, antigens enter the blood, and the immune system begins to produce antibodies in response. Before seroconversion, the antigen itself may or may not be detectable, but the antibody is absent. During seroconversion, the antibody is present but not yet detectable. After seroconversion, the antibody is detectable by standard techniques and remains detectable unless the individual seroreverts, in a phenomenon called seroreversion, or loss of antibody detectability, which can occur due to weakening of the immune system or decreasing antibody concentrations over time. Seroconversion refers the production of specific antibodies against specific antigens, meaning that a single infection could cause multiple waves of seroconversion against different antigens. Similarly, a single antigen could cause multiple waves of seroconversion with different classes of antibodies. For example, most antigens prompt seroconversion for the IgM class of antibodies first, and subsequently the IgG class.
Seroconversion rates are one of the methods used for determining the efficacy of a vaccine. The higher the rate of seroconversion, the more protective the vaccine for a greater proportion of the population. Seroconversion does not inherently confer immunity or resistance to infection. Only some antibodies, such as anti-spike antibodies for COVID-19, confer protection.
Because seroconversion refers to detectability by standard techniques, seropositivity status depends on the sensitivity and specificity of the assay. As a result, assays, like any serum test, may give false positives or false negatives and should be confirmed if used for diagnosis or treatment.
The physical structure of an antibody allows it to bind to a specific antigen, such as bacterial or viral proteins,[3] to form a complex.[4] Because antibodies are highly specific in what they bind, tests can detect specific antibodies by replicating the antigen which that antibody binds to. Assays can likewise detect specific antigens by replicating the antibodies that bind to them.[5] If an antibody is already bound to an antigen, that antibody and that antigen cannot bind to the test. Antibody tests therefore cannot detect that specific antibody molecule. Due to this binding, if the amounts of antigen and antibody in the blood are equal, each antibody molecule will be in a complex and be undetectable by standard techniques. The antigen, which is bound as well, will also be undetectable.[6]
| access-date=2021-11-05 | website=clinicalinfo.hiv.gov | language=en |