Sample collection and storage- Blood samples would be collected in plain vials/vacutainers. CSF samples would be collected in cryovials. Blood samples would be allowed to clot at room temperature for 1 hour. The clotted blood in the plain vacutainers would be centrifuged at 2000 rpm for 15 minutes to separate out the serum. Serum would be pipetted off into cryovials. All samples would be stored at -80˚C immediately till further analysis.