Yingtai: How To Maintain Viral Structural Integrity with Low-Temperature Sterilization

Yingtai: How to Maintain Viral Structural Integrity with Low-Temperature Sterilization  

Key Mechanisms of Low-Temperature Sterilization for Preserving Viral Structure  

Low-temperature sterilization achieves the dual objectives of inactivation and structural preservation by selectively damaging viral genetic material or key enzyme systems while minimizing harm to capsid proteins and envelope structures.  

I. Targeted Nucleic Acid Inactivation  

Chemical Crosslinking Agents  

- Ethylene Oxide Sterilization: At 50-60°C, ethylene oxide gas penetrates the viral envelope and alkylates guanine and adenine in RNA/DNA, forming glycol adducts that block replication.  

- Formaldehyde Low-Temperature Sterilization: In a 40°C environment, formaldehyde binds to amino groups in viral nucleic acids, forming hydroxymethyl derivatives that irreversibly inactivate genetic material while keeping capsid proteins intact (e.g., >95% capsid integrity in inactivated poliovirus).  

Oxidative Damage  

- Hydrogen Peroxide Plasma: At 45-55°C, hydrogen peroxide decomposes into hydroxyl radicals (·OH), which specifically attack phosphodiester bonds in viral RNA/DNA. Capsid proteins, with their stronger antioxidant capacity (due to cysteine residues), suffer less damage.  

II. Physical Inactivation and Structural Preservation  

Low-Temperature Thermal Effects  

- Gradient Heating Inactivation: Treating influenza virus at 60°C for 6 hours increases the fluidity of the envelope lipid layer and dissociates internal ribonucleoprotein (RNP), while hemagglutinin (HA) and neuraminidase (NA) retain their native conformation due to high thermal stability (Tm >70°C).  

Pressure-Assisted Inactivation  

- Vacuum Negative Pressure: In low-temperature steam formaldehyde sterilization, negative pressure (-80 kPa) enhances sterilant penetration to the viral core. Meanwhile, steam humidity (RH 75-85%) maintains capsid protein hydration, reducing denaturation risks.  

III. Structural Stability Enhancement Techniques  

Protectant Additives  

- Sugar Stabilizers: Trehalose (10% w/v) forms hydrogen-bond networks with viral capsid proteins during low-temperature sterilization via water replacement mechanisms, preserving their tertiary structure (e.g., adenovirus vector vaccine capsid integrity improves from 80% to 98%).  

pH Buffer Control  

- Tris-HCl Buffer System: Maintains pH at 7.4±0.2, preventing capsid protein aggregation or degradation due to charge distribution changes under acidic or alkaline conditions (e.g., norovirus VLPs retain a diameter of 38 nm±2 nm post-inactivation).  

IV. Application Cases  

- Inactivated Influenza Vaccine: A 60°C×6-hour inactivation process retains >95% hemagglutinin (HA) activity, with post-vaccination neutralizing antibody GMT reaching 1:320 (compared to 1:160 with traditional formaldehyde inactivation).  

- COVID-19 Inactivated Vaccine (Vero Cell): β-propiolactone inactivation at 4°C for 48 hours preserves >98% spike protein (S protein) trimer integrity, inducing antibodies with 2-4 times greater cross-neutralizing capacity against variants.