Determination of Avidity of IgG Antibodies Directed Towards West Nile Virus

Determination of the avidity of IgG antibodies directed towards West Nile virus (WNV).

Serum. Minimum volume of 250 ml required.

Collect blood in serum separator tubes.

Store samples refrigerated or frozen until shipped for testing. Ship frozen samples on dry ice, and refrigerated samples on wet ice

Shipping of specimens shall be done by a TDG certified individual in accordance with TDG regulations. For additional information regarding classification of specimens for the purposes of shipping, consult either Part 2 Appendix 3 of the TDG Regulations or section 3.6.2 of the IATA Dangerous Goods Regulations as applicable.

Suspected infection with WNV.

Completed Viral Zoonoses requisition including sender laboratory name, address and telephone number. Patient name and / or identifier (specimen reference number), date of birth, test(s) requested, collection date of specimen, date of on-set of symptoms, type of specimen, and clinical and travel history of patient.

N/A

Microplate ELISA or indirect IFA. Assay is used to help distinguish a current WNV infection from non primary WNV infection. Theory of assay is based on the body’s first response to a new infection is the production low avidity antibodies. Avidity refers to the binding intensity of multiple bond interactions between the antibody and antigen. As the infection progresses, the IgG antibodies produced by the body increase in their antigen adaptation, and hence the avidity of the antibody towards the antigen increases. In order to determine the avidity of antibodies in a clinical sample, samples are tested in parallel and subjected to a denaturation treatment that will liberate low avidity antibodies from a solid support but the high avidity antibodies will remain attached. In the event that high avidity IgG is not yet detected in the serum, it can be assumed that the infection is still in an early stage. High avidity IgG indicates a previous WNV infection, low avidity IgG indicates a recently acquired (acute) infection.

14 calendar days.

1. EuroImmun. Avidity determination of IgG antibodies against West Nile virus. Test instruction of the ELISA. 2004.