New findings in live, attenuated hepatitis A vaccine development

Area of Science:

• Virology
• Vaccinology
• Infectious Diseases

Background:

• Hepatitis A virus (HAV) causes significant global health concerns.
• Development of effective vaccines is crucial for disease prevention.
• In vitro cell culture passage is a common method for attenuating viruses.

Purpose of the Study:

• To assess the attenuation and immunogenicity of two hepatitis A virus variants (F and F') derived from cell culture.
• To evaluate the potential of these variants as live, attenuated hepatitis A vaccines.

Main Methods:

• Hepatitis A virus strain CR326F was subjected to extensive in vitro passage in FRhK6 and MRC5 cell cultures to generate variants F and F'.
• Virulence was assessed in marmosets and chimpanzees at various passage levels.
• Immunogenicity and safety were evaluated in adult human volunteers following parenteral inoculation.

Main Results:

• Progressive loss of virulence was observed with increasing in vitro passage.
• Variant F retained slight virulence in animal models and caused minor enzyme elevations in some human volunteers.
• Variant F' demonstrated significant attenuation, showing no evidence of virulence in animals and minimal adverse effects in humans, while inducing protective antibodies.

Conclusions:

• Variant F' is more attenuated than variant F.
• Both variants induced protective antibodies in humans and animals.
• Variant F' shows promise as a candidate for a live, attenuated hepatitis A vaccine.