Intramonocytic destruction of Brucella: potentiating effect of glycine on intracellular lysozyme activity

Osmotically sensitive Brucella in infected normal and immune macrophages

When Brucella suis is grown in tissue cultures of normal guinea pig macrophages, the Brucella multiplies significantly without the induction of osmotically sensitive forms. In immune macrophages in the presence of normal guinea pig serum, there is a reduction in the number of intracellular Brucella and no multiplication is seen over a 72-hr period. After 6 hr of exposure to immune macrophages, however, approximately 50% of the surviving intracellular Brucella are osmotically sensitive, i.e., they will survive and grow only on medium containing 0.2 m sucrose. Brucella grown in immune macrophages, in the presence of rabbit antiserum against whole guinea pig serum, show the presence of osmotically sensitive forms, although at a reduced level compared to the number seen with immune macrophages in normal guinea pig serum.

Sensitization and recall of anti-Brucella immunity in Guinea pig macrophages by attenuated and virulent Brucella

Peritoneal macrophages from guinea pigs vaccinated with strain Rev I of Brucella melitensis were only moderately activated thereby to limit, in an in vitro system, the intracellular growth of Rev I bacilli. Nevertheless, the appropriate memory cells had been primed, as demonstrated by the observation that reinfection of animals with virulent B. melitensis followed by intraperitoneal inoculation of mineral oil called forth macrophages in immunized guinea pigs which inhibited strongly the intracellular growth of brucellae. These macrophages slowed the growth of brucellae in the absence of immune serum. The intensity of the recall response was related to the challenge route and to the virulence of the challenge strain. After equal doses of attenuated or virulent brucellae, resistance was highest in macrophages recalled by the virulent strain. An important basis for the attenuation of the Rev I strain may lie in its initially low degree of macrophage activation during primary infection, although still retaining the capacity to prime stem cells. This property is associated with a protein found in fraction I, because 600 mug/ml in Freund's adjuvant primed guinea pigs so that challenge by strain 6015 evoked activated macrophages. This was seen microscopically as a reduced spread of infection in and amongst the macrophage population. Immune serum further reduced this spread and limited the number of viable intracellular brucellae.

Lysis of brucellae by the combined action of glycine and a lysozyme-like agent from rabbit monocytes

Ralston, Doris J. (University of California, Berkeley), B. S. Baer, and S. S. Elberg. Lysis of brucellae by the combined action of glycine and a lysozyme-like agent from rabbit monocytes. J. Bacteriol. 82:342-353. 1961.-An acid-extractable lytic material was obtained from rabbit monocytes. It acts on a substrate in the walls of brucellae and has properties similar to egg-white lysozyme. Brucella melitensis strain Rev Is is completely resistant to this agent and also to crystalline lysozyme, but when the cells are exposed to sufficient amounts of glycine, the surface is rendered susceptible to these lytic agents. Rough type Rev Is cells are more susceptible than smooth, and the virulent B. melitensis strain 6015 is most resistant.

CYTOPATHOGENIC EFFECT OF BRUCELLA SPHEROPLASTS ON MONOCYTES IN TISSUE CULTURE

Freeman, Bob A. (The University of Chicago, Chicago, Ill.), and Barry H. Rumack. Cytopathogenic effect of Brucella spheroplasts on monocytes in tissue culture. J. Bacteriol. 88:1310-1315. 1964.-Mononuclear phagocytes from guinea pig peritoneal exudates were shown to ingest both normal Brucella suis and spheroplasts prepared from B. suis by treatment with glycine and with penicillin. Quantitative ingestion studies with P(32)-labeled Brucella showed that rough normal Brucella are ingested at a greater rate than are smooth normal Brucella. Spheroplasts prepared from smooth cells were phagocytized at a greater rate than were the normal smooth cells, and spheroplasts prepared from rough Brucella were phagocytized well, although apparently to a lesser extent than from the normal rough Brucella. The degree of phagocytosis of all spheroplasts appeared to reach a peak and then decrease, indicating a release of ingested bacteria; this release of intracellular bacteria is believed to be due to the cytopathogenic effect exerted by the spheroplasts. Direct microscopic observations showed that infection with living spheroplasts prepared from either smooth or rough Brucella destroyed a major portion of the host cells within 4 hr, but that formalin-killed spheroplasts were no more destructive than were normal Brucella. When host cell destruction was assayed by the release of cellular constituents into the medium, it was apparent that host-cell destruction by spheroplasts reaches a significant level within 0.5 hr after ingestion begins, and is almost complete by 4 hr. The implications of these findings in studies on the nature of intracellular Brucella are discussed.

Isolation and properties of an RNA fraction present in Brucella culture supernatants

The supernatant fluids of batch and continuous cultures of Brucella strains contained up to 100 mg/l of soluble RNA which could be recovered by precipitation with lysozyme, This RNA fraction had many of the properties of ribosomal RNA and was single-stranded, sensitive to ribonuclease, with an approximate sedimentation constant of 5S, a molecular weight of about 35000 daltons and an adenine; guanine; cytosine; uracil content of 17.5; 26.5; 33; 23 mol% respectively. RNA fractions from lysozyme precipitates evoked high titres of Brucella agglutinins on injection into rabbits and induced acute inflammatory responses in guinea-pig skin. Highly purified RNA fractions prepared by phenol extraction of lysozyme precipitates did not evoke antibodies to Brucella abortus.

Serum-mediated immune cellular responses to Brucella melitensis. I. Role of a macrophage-stimulating factor in promoting ingestion of Brucella by streptomycin-protected cells

Injection of rabbits with living Brucella melitensis Rev I induced the appearance of a macrophage-stimulating-factor (MSF) in the sera of these animals. MSF was involved in ingestion of bacilli, hastening the formation of protected loci as measured by the addition of lethal amounts of dihydrostreptomycin. When sufficient time had been allowed for effective ingestion, streptomycin had little effect. This in turn allowed for multiplication of bacilli intracellularly in the presence of 5 to 250 mug of drug per ml. MSF mediated more effective ingestion by both immune and normal macrophages. Under such conditions, there was little, if any, intracellular growth restriction by macrophages from immune animals. The activity appeared within the first 5 days after injection with 10(9) organisms and was present for several months. Three weeks after injection, the activity of serum was partially heat-labile. All activity was removed by absorption with heat-killed or living Rev I cells, suggesting that a specific globulin is concerned.

Intracellular production of Brucella L forms . II. Induction and survival of Brucella abortus L forms in tissue culture

Hatten, Betty A. (The University of Texas Southwestern Medical School, Dallas), and S. Edward Sulkin. Intracellular production of Brucella L forms. II. Induction and survival of Brucella abortus L forms in tissue culture. J. Bacteriol. 91:14-20. 1966.-Intracellular survival of altered brucellae, possibly L forms, was not greatly affected by penicillin or streptomycin in concentrations ranging from 5.0 to 40 mug/ml, but a combination of these two antibiotics (2.5 to 20 mug/ml each) reduced the number of positive L-form cultures. Tetracycline (2.0 mug/ml) decreased the number of positive L-form cultures at about the same rate as combinations of the higher concentrations of penicillin and streptomycin. Various concentrations of tetracycline (0.1 to 2.0 mug/ml) with 5.0 mug/ml of penicillin or streptomycin significantly reduced the number of positive L-form cultures. L forms were recovered for several days after elimination of bacteria from the cultures by all of the antibiotics tested. L-form production was not dependent upon the presence of antibiotics in the culture medium, but they were recovered in greater numbers when bacteria were still present in the hamster kidney cells. Addition of thallium acetate to infected cells (at varying intervals of time after infection) to control bacterial growth and conversion to the L phase during cellular disintegration decreased the number of positive L-form cultures obtained over a 10-day period. Comparison of the antibiotic sensitivity of bacteria recovered from infected tissue culture cells with the stock strain of Brucella abortus indicated that some resistance to penicillin and tetracycline had developed. A marked resistance to streptomycin was observed in those bacteria recovered from cells maintained in the presence of this antibiotic.