Cultivating Rickettsia prowazeki (vaccine strain E) in human amnion cells enhanced its antigenic activity and virulence. These biological property changes were observed in over 45% of cell cultures after prolonged passages.

Area of Science:

Microbiology
Cell Biology
Vaccinology

Background:

Rickettsia prowazeki is the causative agent of epidemic typhus.
Vaccine strain E of Rickettsia prowazeki has been used for prophylaxis.
Understanding changes in microbial properties during host cell cultivation is crucial for vaccine development.

Purpose of the Study:

To investigate alterations in the biological properties of Rickettsia prowazeki vaccine strain E.
To assess the impact of human amnion (A1) cell cultivation on rickettsial antigenic activity and virulence.

Main Methods:

Infection of A1 cells with Rickettsia prowazeki vaccine strain E.
Serial passage of infected A1 cell cultures.
Monitoring changes in antigenic activity and virulence of Rickettsia prowazeki populations.

Main Results:

Cultivation in A1 cells led to increased antigenic activity and virulence in Rickettsia prowazeki.
Observed changes in 10 out of 22 cell cultures (45.5%).
Increased antigenic activity occurred in 6 cultures; increased antigenic activity and virulence in 4 cultures, with changes appearing between 12-18 and 53-102 days.

Conclusions:

Human amnion cell cultivation can modify the biological properties of Rickettsia prowazeki vaccine strain E.
These modifications involve enhanced antigenic activity and virulence.
The findings have implications for the stability and efficacy of Rickettsia vaccines.