[Experimental study of postvaccinal immunity to sheep-pox]

Area of Science:

• Veterinary Virology
• Immunology

Background:

• Sheep-pox is a contagious viral disease affecting sheep worldwide.
• Live virus vaccines are crucial for controlling sheep-pox outbreaks.

Purpose of the Study:

• To develop and compare two live virus sheep-pox vaccines (Perego and RM65 strains) derived from lamb testicular cells.
• To evaluate vaccine safety, immunogenicity, and efficacy against sheep-pox.

Main Methods:

• Vaccine preparation using lamb testicular cells.
• Comparative assessment of safety and activity in lambs against a commercial vaccine.
• Immunogenicity evaluation via antibody detection (neutralizing and precipitating) and challenge resistance using a protective index.

Main Results:

• The Perego vaccine, at 10(4) DICT50, demonstrated reliable immunity with no severe post-inoculation reactions.
• The RM65 vaccine exhibited a lower protective index, only preventing generalized infection.
• A correlation was observed between seroneutralizing titers and protective index, with virulent challenge providing better protection data.

Conclusions:

• The Perego strain live virus sheep-pox vaccine is a promising candidate for reliable sheep-pox control.
• Virulent challenge models appear more effective in assessing vaccine-induced protection levels than serological titers alone.