1. 1 Procleix ® WNV Assay: A TMA-based Assay for Screening Blood Donations for West Nile Virus RNA Jeff Linnen, Ph.D. Research and Development Gen-Probe Incorporated, San Diego, CA USA SoGAT July 3, 2003 Procleix® is a registered trademark of Chiron Corporation

2. 2 Procleix WNV Assay Based on Transcription Mediated Amplification (TMA) Uses same instrument platform as Gen-Probe’s licensed NAT blood screening assay –Procleix Semi-automated System currently used with Procleix HIV-1/HCV Assay TECANTarget Capture System (TCS)Luminometer

3. 3 Specificity of the Procleix WNV Assay 1,680 normal blood donations were tested at Gen-Probe –99.8% initial specificity; 100% resolved specificity –over 40,000 archived samples from 2002 high risk populations have been tested by American Red Cross (S. Stramer) No cross reactivity to other blood borne viruses –Testing included HTLV, HIV-1/-2, HCV, HBV, HGV, Rubella, HAV, CMV, EBV, HCV, Parvo B19 Assay designed to specifically detect West Nile virus: –No cross reactivity to other flaviviruses: Dengue (1-4), Yellow Fever Virus, and St. Louis Encephalitis virus ; weak cross reactivity to Murray Valley Encephalitis virus –Detects Kunjin virus (Australian subtype of West Nile virus)

4. 4 Analytical Sensitivity *virus quantified by BBI TaqMan Assay (BBI Diagnostics, West Bridgewater, MA). Based on data from Procleix WNV Assay kit lot manufactured at 2 million test scale **Quantitation for this panel is probably not accurate Probit Analysis (results from BBI panels): Lineage 1: 95% detection at 4 to 14 copies/mL Lineage 2: 95% detection at 4 to 8 copies/mL

5. 5 Samples from CDC WNV Transfusion Transmission Case Investigations (2002) Positive Results from testing 383 blinded samples sent to Gen-Probe from the American Red Cross All donations implicated in transfusion transmission were detected at 1:16 dilution with TMA

6. 6 Nationwide WNV Blood Screening in the United States, 2003 Testing using the Procleix WNV Assay started on June 19 –Implemented nationwide on July 1 –Test development which normally takes 2 to 3 years was condensed into less than 9 months. –Procleix WNV Assay is being used to test over 80% of the US blood supply Most donations are being tested in pools of 16 (some sites are testing individual donations) –reactive pools will be resolved to individual donation Testing will reduce the risk of WNV transfusion transmission –will provide real time surveillance of human WNV activity in North America

7. 7 Acknowledgements Gen-Probe WNV Assay Development Team –(Front to back, left to right) Mike Shih, Josh Cary, Geoffrey Dennis, Janice Cline, Martha Alden, Wen Wu, Mackenzie Lewis, Michelle Cass, Amy Broulik, Jeff Linnen, Stephanie Miller National Heart, Lung, and Blood Institute (NHLBI) for partial funding Susan Stramer, American Red Cross Chiron Corporation