Immunofluorescence-assisted investigation of Human Astrovirus-1 in oyster processing and production

This study evaluated the antiviral efficacy of chlorine dioxide (ClO₂) and peracetic acid (PAA) as chemical disinfectants, and UV-C irradiation as a physical treatment, against HAstV-1, applied individually or sequentially on three relevant matrices: oysters, stainless steel (SS; food-contact surface), and low-density polyethylene (LDPE; packaging surface). Infectious viral titers were quantified using a modified immunofluorescence (IF) assay, which was optimized for oyster matrices in this study by adjusting virus adsorption time, antibody conditions, and buffer composition to enhance reproducibility and signal clarity. Treatment with ClO₂ (200 ppm, 5 min) and PAA (200 ppm, 1 min) resulted in greater reductions (>2 log₁₀ FFU/mL) on oyster tissues compared to UV-C irradiation (1800 mJ/cm²; 1.8 log₁₀ FFU/mL). HAstV-1 levels dropped below the detection limit when treated with ≥700 ppm ClO₂ and ≥1500 ppm PAA on SS and ≥300 ppm ClO₂ and ≥900 ppm PAA on LDPE, respectively. UV-C treatment at 3600 mJ/cm² achieved reductions of 1.37 and 1.63 log₁₀ FFU/mL on SS and LDPE, respectively. Sequential treatments combining ClO₂ (50 ppm) or PAA (150 ppm) with subsequent UV-C irradiation (600 mJ/cm²) significantly enhanced HAstV-1 inactivation on oyster surfaces, yielding additional reductions of 0.96 and 0.57 log₁₀ FFU/mL, respectively. Texture and color analyses indicated slight decreases in hardness and chewiness (p < 0.05); however, no significant differences were observed in elasticity or color parameters (p > 0.05). The modified IF assay demonstrated improved reproducibility and signal clarity and was successfully applied for detecting infectious HAstV-1 in oyster matrices.