Faculty Bibliography

To better understand the contribution of interferon-gamma (IFN-gamma) to the immune response during the first 60 days of mycobacterial infection in the lungs, IFN-gamma gene disrupted (IFN-gamma-/-) mice were infected via aerosol with recombinant Mycobacterium bovis Bacillus Calmette-Guerin (BCG) secreting murine IFN-gamma (BCG-IFN-gamma) and compared to mice infected with recombinant BCG containing the vector only (BCG-vector). When IFN-gamma-/- mice were infected with BCG-vector, increasing bacillary loads and large undifferentiated granulomas that did not express inducible nitric oxide synthase (iNOS) were observed in the lungs. In contrast, infection with BCG-IFN-gamma resulted in reduced bacillary load and better differentiated granulomas containing epithelioid macrophages expressing iNOS as well as reduced levels of interleukin 10 (IL-10) mRNA. However, local production of IFN-gamma by the recombinant BCG did not protect IFN-gamma-/- mice from subsequent challenge with M. tuberculosis. Infection of IFN-gamma-/- peritoneal macrophages in vitro with BCG-IFN-gamma led to induction of iNOS expression and lower IL-10 mRNA levels. Nevertheless, the growth of the intracellular BCG was unaffected. Since IFN-gamma induced-iNOS protein and reduced IL-10 production were insufficient to control mycobacterial growth in vitro, the results suggest that additional mediator(s) present in vivo are required for control of mycobacterial growth

We performed a placebo-controlled study to evaluate the effects of immunomodulatory treatment with thalidomide on HIV levels, TNF-alpha levels, and immune status of 31 HIV-infected individuals, after temporary suppression of viral replication with antiretroviral drugs. Treatment with a combination of zidovudine and lamivudine (ZDV/LMV) for 14 days resulted in a median decline in plasma viremia of 1.94 log10 RNA equivalents/ml. After discontinuation of ZDV/LMV, thalidomide therapy (200 mg/day for 4 weeks) did not retard the prompt return of HIV titers to the pretreatment levels, and had no effect on plasma levels of TNF-alpha. In contrast, thalidomide treatment resulted in significant immune stimulation. We observed increased levels of plasma soluble IL-2 receptor, soluble CD8 antigen, and IL-12 (p < 0.01 for all parameters), as well as increased cutaneous delayed-type hypersensitivity reactions to recall antigens (p < 0.01) in thalidomide-treated patients. These changes were associated with a median increase in HIV titer of 0.2 log10 RNA equivalents/ml in the thalidomide-treated group (p < 0.05), which resolved after stopping the drug. Further studies were performed in vitro to elucidate the mechanism of thalidomide-induced immune stimulation. When purified T cells from HIV-infected individuals were stimulated by immobilized anti-CD3 in the presence of thalidomide, a costimulatory effect of the drug was observed, resulting in increased production of IL-2 and IFN-gamma, and increased T cell-proliferative responses. Further experiments showed that thalidomide increased IL-12 production by antigen-presenting cells in a T cell-dependent manner. Our findings suggest a potential application for thalidomide as a novel immune adjuvant in HIV disease.

Despite the antimicrobial mechanisms of vertebrate phagocytes, mycobacteria can survive within the phagosomes of these cells. These organisms use various strategies to evade destruction, including inhibition of acidification of the phagosome and inhibition of phagosome-lysosome fusion. In contrast to mycobacteria, Coxiella burnetii, the etiologic agent of Q fever, inhabits a spacious acidified intracellular vacuole which is prone to fusion with other vacuoles of the host cell, including phagosomes containing mycobacteria. The Coxiella-infected cell thus provides a unique model for investigating the survival of mycobacteria in an acidified phagosome-like compartment. In the present study, murine bone marrow-derived macrophages were infected with either Mycobacterium avium or Mycobacterium tuberculosis and then coinfected with C. burnetii. We observed that the majority of phagocytosed mycobacteria colocalized to the C. burnetii-containing vacuole, which maintained its acidic properties. In coinfected macrophages, the growth of M. avium was not impaired following fusion with the acidified vacuole. In contrast, the growth rate of M. tuberculosis was reduced in acidified vacuoles. These results suggest that although both species of mycobacteria inhibit phagosome-lysosome fusion, they may be differentially susceptible to the toxic effects of the acidic environment in the mature phagolysosome

Angiogenesis is a crucial process in inflammatory reactions as well as in tumor implantation and growth. Tumors with high rates of invasion and recurrence such as gliomas, are specially dependent on neovascularization. This suggests that inhibition of angiogenesis might reduce the growth of these tumors. Thalidomide has been previously shown to inhibit angiogenesis induced by basic fibroblast growth factor in vivo, using the rabbit corneal micropocket assay. Therefore, the effect of thalidomide and a thalidomide analogue (cc-1069) on the proliferation in vitro of endothelial and glioma cells was tested. We observed a decrease in endothelial cell proliferation in cultures treated with thalidomide or the thalidomide analogue cc-1069. The analogue inhibited endothelial cell proliferation more efficiently than thalidomide. The inhibition occurred in association with a marked decrease in the activity of the nuclear factor SP1 and a moderate inhibition of NF-kappaB activation in nuclear extracts of endothelial cells. The drugs did not impair cell viability. There was no effect of thalidomide or the thalidomide analogue on the proliferation of the glioma cell line (U251) in vitro

Hammerhead ribozymes were used as substrates to examine endoribonucleolytic activities in cell extracts and cultured human cells. Primer-extension analyses showed that ribozymes directed against tumor necrosis factor-alpha mRNA and human immunodeficiency virus type 1 tat mRNA were cleaved at UA and CA dinucleotides by extracts. Preferred cleavage sites were similar to those observed following digestion with RNase A, and cleavage was blocked by RNasin, an inhibitor of pyrimidine-specific ribonucleases. Removal of UA and CA dinucleotides rendered ribozymes more stable when incubated in cell extracts that were not significantly contaminated by extracellular nucleases. Placement of UA dinucleotides adjacent to a ribozyme in mRNA led to excision of the ribozyme from long transcripts during incubation in extracts. UA dinucleotides also made mRNA more labile than a control RNA when expressed from an endogenous plasmid gene in the human myeloid cell line U937. Similarly, UA and CA dinucleotides caused ribozymes to have a shorter half-life when delivered to U937 cells by lipofectin-mediated transformation. Taken together, these data indicate that one or more members of the pyrimidine-specific ribonuclease family is involved in the intracellular degradation of RNA, and they explain the paucity of UA dinucleotides in eukaryotic mRNA. Judicious manipulation of preferred target sequences of pyrimidine-specific ribonucleases may be useful in designing effective hammerhead ribozymes

Thalidomide has been shown to selectively inhibit TNF-alpha production in vitro by lipopolysaccharide (LPS)-stimulated monocytes. TNF-alpha has been shown to play a pivotal role in the pathophysiology of endotoxic shock. Using a mouse model of LPS-induced shock, we investigated the effects of thalidomide on the production of TNF-alpha and other cytokines and on animal survival. After injection of 100-350 micrograms LPS into mice, cytokines including TNF-alpha, IL-6, IL-10, IL-1 beta, GM-CSF and IFN-gamma were measured in the serum. Administration of 200 mg/kg thalidomide to mice before LPS challenge modified the profile of LPS-induced cytokine secretion. Serum TNF-alpha levels were reduced by 93%, in a dose-dependent manner, and TNF-alpha mRNA expression in the spleens of mice was reduced by 70%. Serum IL-6 levels were also inhibited by 50%. Thalidomide induced a two-fold increase in serum IL-10 levels. Thalidomide treatment did not interfere with the production of GM-CSF, IL-1 beta, or IFN-gamma. The LD50 of LPS in this model was increased by thalidomide pre-treatment from 150 micrograms to 300 micrograms in 72 h. Thus, at otherwise lethal doses of LPS, thalidomide treatment was found to protect animals from death