Diagnosis of respiratory virus infections using GACELISA of urinary antibodies

Sensitive and specific methods are needed to diagnose respiratory virus infections using body fluids such as urine that, unlike blood samples, are readily obtained by non-invasive means. Immunoglobulin G antibody capture enzyme-linked immunosorbent assays were developed for detection of antibody rises to respiratory syncytial virus and influenza A/Taiwan (H1N1) after initial quantification and adjustment of urinary IgG concentration. Of 24 elderly subjects whose sera were assayed by the complement fixation test for antibody to RSV, seven had convalescent titres > or = 32, and five had > or = 4-fold rises in titre. Acute and convalescent urines for six of these seven subjects were tested for virus-specific urinary IgG by GACELISA. Four of four persons with > or = 4-fold rises in CFT had urine ELISA convalescent to acute ratios of > or = 1.8 whereas two subjects with convalescent CF titres > 16, but no increase in serum antibody titre, had urine convalescent/acute ratios of 1.0. Ten subjects with > or = 4-fold rises in CFT or HI antibodies to influenza A/Taiwan had urine ELISA ratios of > or = 1.4 when samples taken on the day of influenza vaccination and 16 days later were compared. These preliminary observations demonstrate clinically significant rises in respiratory pathogen antibody levels between acute and convalescent urine samples, provided that total urinary IgG concentrations are quantified and then standardised.