Seroconversion
In immunology, seroconversion is the development of specific antibodies in the blood serum as a result of infection or immunization, including vaccination.
Similarly, a single antigen could cause multiple waves of seroconversion with different classes of antibodies.
[4] Because seroconversion refers to detectability by standard techniques, seropositivity status depends on the sensitivity and specificity of the assay.
[5] The physical structure of an antibody allows it to bind to a specific antigen, such as bacterial or viral proteins,[6] to form a complex.
[16] Similarly, because standard techniques utilize assumptions about the specificity of antibodies and antigens and are based on chemical interactions, these tests are not completely accurate.
More rarely, individuals who have recently had some vaccines or who have certain autoimmune conditions can temporarily test falsely seropositive.
An individual who is seropositive for anti-HIV antibodies will retain that infection chronically unless treated with medications specific to HIV.
For example, higher concentrations of antibodies after seroconversion in individuals vaccinated against COVID-19 predicts reduced chance of breakthrough infection.
In this context, seroconversion refers to the process of anti-viral antibodies becoming detectable in the human population serum.
[27] Rapid tests procurable at a consumer level often fail to detect antibody until at least three months have passed since the initial infection.
[27] Similarly, individuals taking pre-exposure prophylaxis (PrEP) can experience extended window periods compared to the average population, leading to ambiguous testing.
Symptoms can include lymphadenopathy (swelling of the lymph glands), general fatigue and malaise, chills, low-grade fever, sore throat, body aches, night sweats, ulcers in the mouth, pain in the joints and muscles, loss of appetite, headache, and a maculopapular rash on the trunk of the body.
[25] The immune system mounts an acute effort to resolve the HIV infection during the seroconversion period.
The symptoms of seroconversion lessen and disappear in most people, with HIV entering a stage of clinical latency.
At this stage, the infection remains within the body without causing symptoms, and the viral load gradually increases.
The body continues producing anti-HIV antibodies throughout clinical latency, and the HIV infection remains detectable.
However, seroconversion may be helpful for individuals with suspected infections who are negative by RT-PCR testing for viral load.
[36] Concentrations of antibodies develop after several days and reach their maximal value approximately two to three weeks after infection.
[36][39] The length of time that anti-spike IgG remains high varies greatly between different individuals.
Younger individuals tend to have much higher and more sustained peaks of anti-spike IgG antibodies following the second dose.
[48] Many otherwise ill individuals, such as those with cancer or chronic liver disease, still exhibit similar rates of seroconversion to the general population.
[49][50] On the other hand, individuals with weakened immune systems, such as due to immunosuppressive medications or leukemia, can exhibit decreased rates of seroconversion for currently available vaccines.
[36] This implies that the resistance may not last long-term in older individuals, leaving them suspectible to subsequent COVID-19 infections.
[55] Some studies have disputed the link between concentrations of antibodies of either IgM or IgG and the severity of the disease course.
[58][57] Some individuals who have recovered from COVID-19 may decline vaccination due to the belief that their recovery from infection has a protective effect.
[60] As in other viral infections, seropositivity indicates that an individual has a sufficiently high concentration of antibody or antigen in the blood to be detectable by standard techniques.
[64] The window period for HBsAg/anti-HBs testing occurs as concentration of HBsAg falls and before the body develops anti-HBs antibodies, lasting approximately six to eight weeks in most individuals.
The presence of core antibody (anti-HBc) indicates an individual with an infection in general, whether current or previously resolved.
An individual with an acute HBV infection would test positive for HBsAg and anti-HBc (total and IgM) while negative for anti-HBs.
[71] Other studies have indicated that even for those who seroconvert, the immunity conferred may decrease over time, and boosters are also recommended for immunocompromised individuals after five years.
