A comparative study of attenuated influenza viruses

Area of Science:

• Virology
• Immunology
• Vaccine Development

Background:

• Influenza A and B viruses were adapted for growth at 25 degrees C.
• Attenuated viruses are crucial for developing safe and effective vaccines.
• Temperature-sensitive (ts) mutants offer a potential avenue for influenza vaccine attenuation.

Purpose of the Study:

• To assess the infectivity, antigenicity, and safety of temperature-adapted influenza viruses.
• To determine the minimum immunizing dose of egg-adapted influenza virus.
• To compare attenuated viruses from different regions with existing vaccine strains.

Main Methods:

• Adaptation of influenza viruses to lower temperatures (25°C).
• Administration of attenuated viruses to volunteer subjects.
• Plaque selection at 25°C followed by passage at 33°C to increase infectivity.
• Comparison of attenuated strains in volunteer trials.

Main Results:

• Adapted influenza viruses were attenuated, infective, and antigenic in human volunteers.
• The minimum immunizing dose was determined to be 10^5.0 EID50 for egg-adapted virus.
• No reversion to virulence was observed after passages.
• Attenuated viruses from the UK and USA showed similar results to USSR vaccine strains.

Conclusions:

• Temperature-sensitive influenza virus mutants can be attenuated while retaining immunogenicity.
• The methods used provide a safe approach for generating influenza vaccine candidates.
• Further research into temperature-sensitive mutants is warranted for influenza vaccine innovation.