[Experimental protective of fraction I of the plague microbe]

The immunogenic properties of the freeze-dried preparation of fraction I tisolated from the culture of avirulent Pasteurella pestis strain were studied in experiments on hamadryas baboons, guinea-pigs and white mice. The preparation was found to have a pronounced protective effect in hamadryas baboons and white mice, especially when the preparation was used in mixture with incomplete Freund adjuvant. In hamadryas baboons resistance to infection was shown to correlate with hemagglutionation antibody titres.