VACCINATION AGAINST TUBERCULOSIS WITH NONLIVING VACCINES .2. VACCINATION OF GUINEA PIGS WITH PHENOL-KILLED TUBERCLE BACILLI

Abstract

A vaccine prepared from phenol-killed human tubercle bacilli was found to be at least as effective, under certain experimental conditions, as living BCG in prolonging the survival time of guinea pigs infected by inhalation of a cloud of virulent tubercle bacilli. The degree of survival protection bestowed by the killed vaccine varied with the dosage, the route and vehicle of administration, and the length of the vaccination-challenge interval. ''The preparation was most effective when very small quantities were used: a single intraperitoneal injection of 1.5 mg suspended in saline, or of 0.5 mg suspended in Freund''s adjuvant, provided a somewhat better protection than living BCG. When the killed bacilli were suspended in adjuvant, the subcutaneous route of vaccination appeared to be more effective than the intraperitoneal one. Under certain conditions of administration, the duration of the heightened resistance elicited by the killed vaccine was of the same order as that evoked by living BCG even when a period of almost 9 months elapsed between vaccination and challenge. The killed vaccine caused no gross manifestations of toxicity in quantities at which protection was elicited. Even in considerably larger amounts, its toxic action was almost invariably mild and transient. A similarly prepared and killed vaccine made from the saprophytic Mycobacterium phlei was consistently devoid of any protective activity.