Mouse antisera to GLRaV-2 treated with glutaraldehyde and their activity in ELISA, IEM and Western Blots: Treatment of some viruses with glutaraldehyde increase their immunogenicity, and production of antisera with substantially higher antibody titre than for nati ve viruses can be obtained (Francki & Habili, 1972; Hajimorad & Francki, 1991). To test whether this applies to GLRaV-2, preparations of purified virus were treated with 0,2% glutaraldehyde and then dialysed to remove the glutaraldehyde before immunising four mice. Four control mice were immunised with native virus. Antisera obtained to native and glutaraldehyde-treated GLRaV-2 preparations were tested in ATA-ELISA using extracts of infected and virus-free N. benthamiana and grapevine cv. Shiraz. Results presented in Table 3 show that the absorbance values obtained for infected plants did not differ markedly between the two sets of antisera. The absorbance values obtained with antisera to nati ve GLRaV-2 for virus-free N. benthamiana were highly variable. The values ranged from 0.042 to 1.8 depending on the mouse, whereas the absorbance values obtained with the antisera to glutaraldehyde-treated preparations were fairly uniform. The values remained low and ranged between 0.035 and 0.056. Surprisingly, we observed relatively high levels of nonspecific reaction with the monoclonal antibody to extracts of virus-free plants compared to the polyclonal antisera (Table 3). In contrast to the results obtained for virus-free N. benthamiana, the absorbance values to virus-free grapevine cv. Shiraz were low for both the antisera to glutaraldehyde-treated preparations and to the native GLRa V-2 preparations and were similar to the results obtained with the monoclonal antibody