Abstract Purpose: Human papillomavirus (HPV) type 16 is associated with oropharyngeal carcinomas (OPC). Antibodies (Abs) to HPV16 E6 and E7 oncoproteins have been detected in patient sera, however Abs to other early HPV-derived proteins have not been well explored. Experimental Design: Abs to the HPV16 proteome were quantified using a novel multiplexed bead assay, using C-terminal GST fusion proteins captured onto Luminex beads. Sera were obtained from two cohorts of untreated OPC patients with known Abs to HPV16 Virus-Like Particles (VLP) (N=10), HPV18 VLP (N=10), healthy controls (N=20), and from a validation cohort of untreated patients with OPC (N=30), partners of patients with HPV16+ OPC (N=11), and healthy controls (N=30). Results: OPC patients in the known VLP+ cohort had elevated serum Abs to HPV16 E1, E2, E4, E6, and E7, and L1 antibody levels but not E5. The ratios of specific median fluorescent intensity (MFI) to p21-GST compared to controls were: E1 50.7 vs. 2.1; E4 14.6 vs. 1.3; E6 11.3 vs. 2.4; E7 43.1 vs. 2.6; and L1 10.3 vs. 2.6 (each p<0.01). No cross-reactivity was detected between HPV16 E7 and HPV18 E7 Abs. In the validation cohort, HPV16 E1, E2, and E7 antibody levels were most significantly elevated compared to healthy control samples (p<0.0001) and partners of OPC patients (p<0.01). Conclusion: A novel multiplexed bead assay for the detection of HPV16-specific Abs demonstrates that patients with HPV16+ OPC have detectable Abs to multiple early genes, in particular E1, E2 and E7. These Abs are potential biomarkers for HPV-associated OPC. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 902. doi:10.1158/1538-7445.AM2011-902