Peter F. Bonventre

Leishmania donovani infection in athymic mice derived from parental strains of the susceptible (Lshs) or resistant (Lshr) phenotype.

Leishmania donovani, the agent of disseminated leishmaniasis, is a vectortransmitted protozoan parasite which multiplies exclusively within tissue macrophages of the infected host [16,25,39]. The etiologic agent is one of several species responsible for human leishmamasis manifested either by cutaneous or systemic disease [25,391. Visceral leishmaniasis is a chronic and life-threatening infection. The parasite is disseminated from the skin to the liver, spleen, and bone marrow, where macrophages serve as obligatory host cells for the amastigote (tissue) form of Leishmania donovani. The genetic basis for resistance or susceptibility to infection has become amenable to analysis primarily by the development of congenic and recombinant inbred strains of mice for use as experimental hosts [3,6,9,32,35,36]. Less than 10 years ago, Bradley et al [6,8,9] performed seminal studies showing that inbred strains of mice can be classified as innately resistant or susceptible to L donovani by the patterns of infection which ensue after challenge. Resistance or susceptibility as measured by the increase in the total parasite burden in the liver after several weeks of infection reveal that some inbred mouse strains restrict intrahepatic multiplication while others permit significant multiplication within macrophages so that a 10-100-fold increase in L donovani amastigotes is evident within 30 days. It was subsequently established that resistance or susceptibility of mice is controlled by a single autosomal gene on mouse chromosome I [9]. The gene designated as Lsh appears to govern macrophage functions so that significant intracellular multiplication of the protozoan parasite in the liver and spleen is either permitted or restricted

A fas Antigen Receptor Mutation Allows Development of Toxic Shock Syndrome Toxin-1 -Induced Lethal Shock in Vβ8.2T-Cell Receptor Transgenic Mice

Recombinant toxic shock syndrome toxin-1 (rTSST-1) administered to MRL-lpr/lpr TCR V beta 8.2 transgenic mice at doses of 0.1 microgram/mouse resulted in 100% mortality. This was an unexpected finding since TSST-1 does not activate V beta 8.2 T cells. In contrast, control mice heterozygous at the lpr locus and also for the transgene (MRL-lpr/+; V beta 8.2/0) survived doses of superantigen 100 times higher. The transgenic mice which succumbed to rTSST-1 challenge exhibited histopathology of the liver consistent with toxic shock (generalized inflammation and hepatocellular necrosis) as well as substantially elevated serum TNF-alpha, IL-2, and IL-6 cytokine levels. Splenic T cells derived from transgenic mice stimulated with rTSST-1 in vitro did not undergo detectable proliferation as measured in a standard mitogen assay. However, PCR amplification of cDNA prepared from the V beta 8.2 splenocytes revealed the presence of minor populations of TSST-1-reactive V beta elements (i.e. V beta 3 and V beta 15). Furthermore, an expansion of the V beta 3 and V beta 15 T-cell families was detected by PCR assay of spleen cell cultures stimulated with rTSST-1. These results suggested that the exquisite sensitivity of the MRL-lpr/lpr V beta 8.2 transgenic animals to rTSST-1 was not dependent exclusively on T-cell proliferation but was augmented by the influence of a defective fas antigen receptor expressed in homozygous lpr mice. To test this hypothesis more directly, we compared the sensitivity of MRL-lpr/lpr mice (not carrying the V beta 8.2 transgene) to MRL-+/+ mice. The MRL-lpr/lpr fas antigen-defective mice were substantially more susceptible to rTSST-1 challenge. Mice carrying the lpr mutation on another genetic background (C57BL/6.C3H-lpr/lpr) were also more sensitive to rTSST-1 challenge than were C57BL/6.C3H-+/+ mice. Although induction of toxic shock is clearly associated with T-cell proliferation, defects in fas antigen receptor or ligand may also contribute substantively to superantigen-mediated lethal shock by still undefined mechanisms.

Effects of solid tumors on the resistance of mice to viral and bacterial infections.

Abstract Balb/c mice, athymic mice with a Balb/c genetic background, and their heterozygote littermates were used in experiments to evaluate the consequence of developing solid tumors on resistance to viral and bacterial infections. Mice bearing 15-day tumors were challenged with Streptococcus pneumoniae, Listeria monocytogenes, herpes simplex virus type 2, or ectromelia virus. The Balb/c tumors employed were a methylcholanthrene-induced fibrosarcoma (Meth A) and a mammary carcinoma (D2-7041): these were shown experimentally to be immunogenic and nonimmunogenic, respectively. The data show that these rapidly developing tumors do not impair the native resistance of either the immunocompetent or athymic strains when compared to non-tumor-bearing mice. Tumor burden imparted an enhanced resistance of immunocompetent mice to L. monocytogenes while exerting no measurable effects on the outcome of pneumococcal or ectromelia and herpes simplex virus infections.

Specific reversal of diphtheria toxin mediated inhibition of protein synthesis in guinea pig tissues

Abstract Formation of inactive transferase II by the action of diphtheria toxin in vivo has been demonstrated only in heart and other muscle tissues. Excess nicotinamide and toxin restored the activity of soluble extracts from the muscle tissues to normal levels. Soluble extracts derived from spleen, kidney and lung of diphtheritic guinea pigs could not be reactivated in this manner.

Studies on the Effect of Diphtheria Toxin on Protein Synthesis in Mice

Summary Mice are several orders of magnitude more resistant to diphtheria toxin than are guinea-pigs and man. Resistance is, however, relative rather than absolute, because 2000 guinea-pig lethal doses cause death of mice within 36 hr. Mice subjected to this quantity of toxin subsequently received an injection of tritiated leucine during the latter stages of the toxaemia in order to assess de novo protein synthesis in vivo. All tissues from toxin-treated mice, with the exception of skeletal muscle and kidney, incorporated 3H-leucine to the same extent as did comparable tissues of normal animals, or to a greater extent. In view of the fact that the biochemical action of diphtheria toxin on more susceptible animals is known to result in a cessation of protein synthesis, the implications of the unexpected results are discussed in terms of species resistance to toxin and the pathophysiology of diphtheritic toxaemia.

Nonspecific resistance toListeria monocytogenes in mice infected and elicited withStaphylococcus aureus

Normal mice and mice displaying delayed hypersensitivity toStaphylococcus aureus were challenged with a lethal dose ofListeria monocytogenes. Nonspecific antimicrobial activity was assessed by inhibition of bacterial growth in the spleen and by increased survival rates. Administration of specific staphylococcal antigen prior to challenge was a prerequisite for the induction of nonspecific resistance. Both the time of administering eliciting antigen and the route were important consideration for evoking the response. Similar responses were seen in 3 strains of inbred mice following immunization with both encapsulated and nonencapsulated staphylococci. Although enhanced resistance as measured by viable counts in the spleens was achieved after 2 injections, protection as measured by survival required 4 injections ofS. aureus followed by elicitation with staphylococcal antigens. Nonspecific resistance could be detected as late as 9 weeks after the disappearance of delayed hypersensitivity.

Killing of Leishmania Donovani Amastigotes by Murine Macrophages

Activated tissue macrophages are the effector cells responsible for containment of a variety of intracellular, bacterial, mycotic and protozoan parasites. The term “activated” macrophage employed originally to describe enhanced bactericidal capability (1) has been extended in recent years to tumoricidal activity (2,3). An activated macrophage system arises as a consequence of stimuli provided by one or more soluble mediators of T lymphocyte origin (4). The mechanisms responsible for destruction of intracellular parasites and killing of tumor cells by activated macrophages may be related (5,6).

Acquired cellular resistance following transfer of lymphocytes from mice infected repeatedly with Staphylococcus aureus

Abstract Cell-mediated immunity following multiple staphylococcal infections of mice was found to differ from other established experimental models of infection with facultative intracellular microorganisms in that acquired cellular resistance was of extremely short duration. This is perhaps a reflection of the fact that Staphylococcus aureus does not multiply or survive within mononuclear phagocytes and are eliminated from the tissues within a few days. Thus, a sustained antigenic stimulus required for maintenance of cellular immunity does not occur. Spleen cells from immunized mice transferred simultaneously with staphylococcal antigen conferred resistance against Listeria monocytogenes on unimmunized syngeneic mice. Treatment of immune splenic lymphocytes with antilymphocyte serum and complement markedly inhibited or abolished capacity of the lymphocytes to transfer resistance to Listeria . These results support and extend our previous data which suggest that mice infected repeatedly with staphylococci are able to suppress the growth of L. monocytogenes via cellular rather than humoral mechanisms.

Studies on the Mode of Action of Diphtheria Toxin VI. Inhibition of Protein Synthesis Induced by Local Infection with Toxinogenic Corynebacterium diphtheriae

Summary Protein synthesis in the tissues of guinea pigs after intramuscular challenge with viable, toxinogenic diphtheria bacilli was evaluated by measuring incorporation of 3H–leucine into cellular proteins. Significant inhibition of protein synthesis occurred in muscle tissues (heart, diaphragm, and skeletal muscle) and several non–muscle tissues (kidneys, liver, and adrenal gland). Protein synthesis in the spleen, small intestine, lung and brain was unimpaired. Inhibition of protein synthesis subsequent to intramuscular injection of 10 MLD purified diphtheria toxin was restricted to the three muscle tissues while non–muscle tissues were unaffected. Purified neuraminidase and deoxyribonuclease injected simultaneously with toxin failed to increase the range of tissues inhibited. Possible reasons for the difference in the patterns of inhibition obtained with C. diphtheriae bacilli and purified toxin are considered.