Carbon monoxide (CO) is an activator of soluble guanylyl cyclase and is implicated as a neuronal messenger. CO production, nitric oxide synthase (NOS) activity, and guanosine 3',5'-monophosphate (cGMP) levels were quantitated in cerebellar granule cell cultures. Metabolic labeling experiments enabled the direct measurement of neuronal CO production in vitro. CO production is significant, and peaked during early stages of culture. NOS activity and cGMP levels synchronously increased as cells matured. Whereas inhibition of NOS depleted cGMP in mature cultures, inhibitors of CO production potentiated the nitric oxide (NO)-mediated cGMP increase. Exogenous CO at similar concentrations to endogenous levels blocked the NO-mediated cGMP increase. These results directly demonstrate that endogenous neuronal CO production is high and indicate that while NO is the major regulator of cGMP in these neurons, CO may modulate the NO-cGMP signaling system.

Backgound Antibodies (Abs) to the HPV16 proteome increase risk for HPV-associated OPC (HPVOPC). The goal of this study was to investigate the association of a panel of HPV16 Abs with risk for OPC as well as the association of these Abs with tumor HPV and smoking status among patients with OPC. Methods IgG Abs to the HPV16 antigens E1, E2, E4, E5, E6, E7, L1, L2 were quantified using a programmable ELISA assay. Sera were obtained from 258 OPC patients at diagnosis and 250 healthy controls. HPV16 tumor status was measured by PCR for 137 cases. Multivariable logistic regression was used to calculate odds ratios for the association of HPV16 Abs with risk for OPC. Results HPV16 E1, E2, E4, E5, E6, E7 and L1-specific IgG levels were elevated in OPC patients compared to healthy controls (p<0.05). After multivariable adjustment, Ab positivity for NE2, CE2, E6, and/or E7 was associated with OPC risk (OR [95% CI], 249.1 [99.3–624.9]). Among patients with OPC, Ab positivity for these antigens was associated with tumor HPV status, especially among never or light smokers (OR [95% CI], 6.5 [2.1–20.1] and OR [95% CI], 17.5 [4.0–77.2], respectively). Conclusions Antibodies to HPV16 proteins are associated with increased risk for HPVOPC. Among patients with OPC, HPV16 Abs are associated with tumor HPV status, in particular among HPV positive patients with no or little smoking history.

Purpose Oropharyngeal carcinoma (OPC) positive for human papillomavirus type 16 (HPV16) has a significantly better prognosis than OPC unrelated to HPV. Within HPV16-positive OPC, biomarkers of prognosis are urgently needed to individualize care. We hypothesized that serum antibodies specific to HPV16, the major HPV type causing OPC, have biological relevance and are potential biomarkers for improved prognosis among patients with HPV16-positive OPC. Methods IgG antibodies to the HPV16 antigens E1, E4-E7, L1, L2, and the N-terminal and C-terminal fragments of E2 (NE2, CE2) were quantified using a custom programmable enzyme-linked immunosorbent assay. Sera were obtained at diagnosis from 209 OPC patients (96 HPV16-positive). The ratios of median fluorescent intensity (MFI) for each antigen to MFI for control GST protein were determined. Kaplan-Meier survival curves and Cox proportional hazards regression were used to determine survival differences between groups. ROC curves were used to determine the best combination of E antibodies to predict disease recurrence. Results E1, NE2, and E6 antibody positivity were all strongly associated with improved overall and progression-free survival in the entire cohort and in patients with known HPV16-positive tumors (P<.05). For both overall and progression-free survival among HPV-positive patients, hazard ratios were 0.2 for NE2, 0.3 for E1, and 0.3 for E6 antibody positivity. Conclusion We identified 3 HPV16-specific antibodies that are associated with improved overall and progression-free survival in patients with HPV-related OPC. These results suggest that differential serologic responses in patients may reflect differential biological processes within the host and tumor and may have prognostic value.

Objectives We hypothesized that viral and host factors impact the serologic responses to HPV early antigens in HPV-positive oropharyngeal cancer (HPVOPC). Materials and methods We conducted a multicenter study to measure HPV16-specific IgG among patients with HPVOPC, their long-term sexual partners, and healthy volunteers. Risk factor surveys and rinse and gargle specimens were collected. Peripheral blood samples at diagnosis were evaluated for IgG Abs to HPV16 antigens using a programmable ELISA assay. Predictors for HPV16 serologic responses were evaluated using univariate and multivariable linear regression. Results 116 patients with HPVOPC, 43 partners, and 81 healthy volunteers were enrolled and had baseline sera for analysis. Cases were primarily male (90%), with a median age of 56 years. Abs to E1, E2, E6 or E7 antigens were detected more often in HPVOPC compared with volunteers or partner sera (p<0.0001). HPV16 Abs to at least one early protein (E1, E2, E4, E5, E6, or E7) were detected in the sera of 90.6% of cases, 0% of partners and 7.4% of healthy volunteers. Gender, race, sexual behavior, and viral integration were not associated with antibody response. Younger age and higher oral HPV16 copy number were associated with higher HPV16 E6 and NE2 antibody levels. Conclusions HPV16 seroreactivity is commonly detected among patients with HPVOPC at diagnosis, but not among partners or healthy volunteers. Seroreactivity among cases are correlated with viral load and stage and not with other demographic or behavioral factors. Positive HPV16 serology was strongly associated with HPV 16 oropharyngeal cancer.