Mice deficient in inducible nitric oxide synthase (iNOS) were generated to test the idea that iNOS defends the host against infectious agents and tumor cells at the risk of contributing to tissue damage and shock. iNOS-/-mice failed to restrain the replication of Listeria monocytogenes in vivo or lymphoma cells in vitro. Bacterial endotoxic lipopolysaccharide (LPS) caused shock and death in anesthetized wild-type mice, but in iNOS-/-mice, the fall in central arterial blood pressure was markedly attenuated and early death averted. However, unanesthetized iNOS-/-mice suffered as much LPS-induced liver damage as wild type, and when primed with Propionobacterium acnes and challenged with LPS, they succumbed at the same rate as wild type. Thus, there exist both iNOS-dependent and iNOS-independent routes to LPS-induced hypotension and death.

The serine/threonine kinase Akt has been implicated in the control of cell survival and metabolism. Here we report the disruption of the most ubiquitously expressed member of the akt family of genes, akt1, in the mouse.

The DNA-dependent protein kinase (DNA-PK) is a mammalian serine/threonine kinase that is implicated in the repair of DNA double-strand breaks, DNA replication, transcription, and V(D)J recombination. To determine the role of the DNA-binding subunit of DNA-PK in vivo, we targeted Ku80 in mice. In mutant mice, T and B lymphocyte development is arrested at early progenitor stages and there is a profound deficiency in V(D)J rearrangement. Although Ku80-/- mice are viable and reproduce, they are 40-60% of the size of littermate controls. Consistent with this growth defect, fibroblasts derived from Ku80-/- embryos showed an early loss of proliferating cells, a prolonged doubling time, and intact cell-cycle checkpoints that prevented cells with damaged DNA from entering the cell-cycle. The unexpected growth phenotype suggests a new and important link between Ku80 and growth control.

TRAF2 is believed to mediate the activation of NF-kappaB and JNK induced by the tumor necrosis factor receptor (TNFR) superfamily, which elicits pleiotropic responses in lymphocytes. We have investigated the physiological roles of TRAF2 in these processes by expressing a lymphocyte-specific dominant negative form of TRAF2, thereby blocking this protein's effector function. We find that the TNFR superfamily signals require TRAF2 for activation of JNK but not NF-kappaB. In addition, we show that TRAF2 induces NF-kappaB-independent antiapoptotic pathways during TNF-induced apoptosis. Inhibition of TRAF2 leads to splenomegaly, lymphadenopathy, and an increased number of B cells. These findings indicate that TRAF2 is involved in the regulation of lymphocyte function and growth in vivo.

We recently have shown that mice deficient for the 86-kDa component (Ku80) of the DNA-dependent protein kinase exhibit growth retardation and a profound deficiency in V(D)J (variable, diversity, and joining) recombination. These defects may be related to abnormalities in DNA metabolism that arise from the inability of Ku80 mutant cells to process DNA double-strand breaks. To further characterize the role of Ku80 in DNA double-strand break repair, we have generated embryonic stem cells and pre-B cells and examined their response to ionizing radiation. Ku80 ؊/؊ embryonic stem cells are more sensitive than controls to ␥-irradiation, and pre-B cells derived from Ku80 mutant mice display enhanced spontaneous and ␥-ray-induced apoptosis. We then determined the effects of ionizing radiation on the survival, growth, and lymphocyte development in Ku80-deficient mice. Ku80 ؊/؊ mice display a hypersensitivity to ␥-irradiation, characterized by loss of hair pigmentation, severe injury to the gastrointestinal tract, and enhanced mortality. Exposure of newborn Ku80 ؊/؊ mice to sublethal doses of ionizing radiation enhances their growth retardation and results in the induction of T cell-specific differentiation. However, unlike severe combined immunodeficient mice, radiation-induced T cell development in Ku80 ؊/؊ mice is not accompanied by extensive thymocyte proliferation. The response of Ku80-deficient cell lines and mice to DNA-damaging agents provides important insights into the role of Ku80 in growth regulation, lymphocyte development, and DNA repair.

Tuberculous meningitis (TBM) is a devastating form of tuberculosis that occurs predominantly in children and in immunocompromised adults. To study the pathogenesis of TBM, a rabbit model of acute mycobacterial central nervous system infection was set up (8-day study). Inoculation of live Mycobacterium bovis Ravenel intracisternally induced leukocytosis (predominantly mononuclear cells), high protein levels, and release of tumor necrosis factor-alpha (TNF-alpha) into the cerebrospinal fluid within 1 day. Histologically, severe meningitis with thickening of the leptomeninges, prominent vasculitis, and encephalitis was apparent, and mortality was 75% by day 8. In animals treated with antituberculous antibiotics only, the inflammation and lesions of the brain persisted despite a decrease in mycobacteria; 50% of the rabbits died. When thalidomide treatment was combined with antibiotics, there was a marked reduction in TNF-alpha levels, leukocytosis, and brain pathology. With this combination treatment, 100% of the infected rabbits survived, suggesting a potential clinical use for thalidomide in TBM.

No abstract

Oligosaccharides that block the adherence of bacteria to epithelial cells in vitro--lacto-N-neotetraose (LNnT) and its alpha2-3- and alpha2-6-sialylated derivatives--were tested for their abilities to attenuate the course of pneumococcal pneumonia and to prevent colonization of the nasopharynx in animal models. Intratracheal administration of these agents concurrently with bacteria dramatically decreased pneumococcal load in the lungs of rabbits and conferred protection from bacteremia. The oligosaccharides ameliorated pneumonia and bacteremia when given therapeutically 24 h after infection was established. When administered intranasally, neoglycoconjugates of the active oligosaccharides prevented colonization of the nasopharynx of infant rats. In addition to in vitro anti-adherence properties, LNnT acted directly on cultured lung epithelial cell lines to induce changes such that pneumococcal adherence was prevented for prolonged periods. These activities encourage continued development of oligosaccharides as a class of potentially preventive and therapeutic agents for infectious diseases.