Diagnosis of Epstein-Barr Virus Infection (III)
The IFAC method for anti-EBNA is applied to heat-inactivated samples (56 º C, 30 min). A critical aspect in the determination of antibodies to EBNA is that the wells should not be dry between incubations, as you can get false negative results.
With these techniques in the course of primary infection occurring anti-VCA responses, both IgM and IgG isotype, in a virtually simultaneous. In most cases reach the peak in the time symptoms appear, or a few days later, so in most cases it is possible to detect IgG seroconversion. Between 2 and 3 months after onset of illness, the IgM response falls to undetectable levels, while IgG remains at good levels throughout the life of the individual.
A significant proportion of patients (about 85%) developed IgG against early antigen diffuse component (EA-D), whose peak was reached a few days after onset, and usually disappears within a few months. Antibodies to EBNA appear weeks or even several months after the onset of the disease.
Thus, the profile of antibodies against primary infection by EBV is characterized by the presence of IgG and IgM responses against the capsid antigen in the absence of anti-EBNA. This profile is presented in more than 90% of cases of IM caused by EBV.
In a few patients displayed abnormal patterns with early onset of anti-EBNA and others is not possible to detect the IgM response. In cases where no typical profile obtained is very useful the tests for the characterization of specific IgG avidity.
In recent years methods have been developed for IgG and IgM anti-VCA and IgG anti-EBNA, based on the use of recombinant proteins. When compared the IFIs and conventional techniques using recombinant proteins for detection of IgM anti-VCA some outlying result is obtained because the cell lines used in IFI express not only AC but some other antigens against which also IgM response occurs.
The fluorescence assay for anti-EBNA with recombinant antigen has the advantage of using the technique of IFI, easier development of IFAC. A novel alternative is to apply a test of IFAC on a cell line that expressed both EBNA and VCA and EA. The method offers the advantage of allowing a single determination on a single well, to establish whether it is an acute infection, past or absent depending on the pattern of fluorescence obtained.
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good thanks \o/
good information