No abstract

The outer surface lipoproteins of Borrelia burgdorfieri, OspA and OspB, stimulate the production of nitric oxide (NO) by murine bone marrow-derived macrophages from BALB/c, C3H/HeN, and C3H/HeJ mice. Gamma interferon (IFN-y) caused a threeto fivefold enhancement of this production of NO, and the L-arginine analog N-guanidino-monomethyl L-arginine inhibited it. Activation of transcription of the inducible NO synthase gene in stimulated macrophages was demonstrated by reverse transcriptase rapid PCR. Although IFN-y increased the amount of NO produced in macrophage cultures, it did not cause transcription of the inducible NO synthase gene greater than that seen with the Borrelia proteins. OspA and OspB also induced the production of high levels (40 to 150 ng/ml) of IFN-y in cultures of macrophages incubated with interleukin-2 (IL-2)-elicited cells from normal (T and NK cells) and scid (NK cells) mice but not in macrophages or IL-2-elicited cells cultured individually. This suggests that OspA stimulated macrophage production of cytokines, which, in turn, stimulated the production of IFN-y by NK and T cells. Reverse transcriptase rapid PCR demonstrated that OspA and sonicated B. burgdorferi stimulated production of several inflammatory cytokines in macrophage cultures, including IL-1, IL-6, IL-12, IFN-1l, and tumor necrosis factor alpha. As tumor necrosis factor alpha, IFN-I, and IL-12 are potent activators of IFN-y production by T and NK cells, their presence in these cocultures could be responsible for the IFN-y production. Lymphocytes from infected C3H mice also produced IFN-y when stimulated with B. burgdorferi; thus, immune cells may also modulate NO responses. The generation of NO during infection with B. burgdorferi may be important, as NO has potent antimicrobial properties. NO can also be involved in pathological inflammatory processes in which its generation is detrimental to the host. Thus, the colocalization of B. burgdorferi lipoproteins, NO-producing cells, and regulatory cytokines may determine the outcome of infection.

No abstract

Borrelia burgdorferi produces potent cell-activating molecules capable of stimulating polyclonal proliferation and immunoglobulin production by murine B lymphocytes and cytokine production by a variety of cell types. These stimulatory molecules function in infected mice, resulting in elevated levels of circulating immunoglobulins and serum interleukin-6. We have recently demonstrated that the purified outer surface lipoproteins OspA and OspB possess these properties. To assess their possible involvement in human disease, we determined whether cells from normal human donors could respond to these activities. Normal human B lymphocytes but not T lymphocytes proliferated when incubated with either sonicated B. burgdorferi or purified OspA. Sonicated B. burgdorferi was efficient at stimulating immunoglobulin M production by human mononuclear cell cultures; however, purified OspA was relatively inactive. Both sonicated B. burgdorferi and purified OspA stimulated production of high levels of interleukin-6 by mononuclear cells. These findings extend our observations with the mouse model and suggest that the stimulatory lipoproteins could indeed be involved in the symptoms and pathologies of human infection with B. burgdorferi.

Human hepatocellular carcinoma (HCC) often arises from a background of liver cirrhosis. Therefore, in order to develop therapeutic strategies for HCC, an animal model bearing multifocal liver tumors accompanied by liver cirrhosis is a preferred experimental setting. In this study, we developed a rapid and reproducible method for generating such a model in rats by weekly administration of diethylnitrosamine (DEN) at doses based on body weight (BW). By adjusting the duration of administration of DEN, the animals could be induced to develop HCC alone, or HCC and liver cirrhosis simultaneously. The latter model was used for evaluating the therapeutic effects of adenoviral delivery of interferon-alpha (IFN-alpha). Our results demonstrated that targeting of IFN-alpha expression to the liver significantly reduced liver tumor volume and ameliorated liver cirrhosis. Mechanistic studies revealed that IFN-alpha gene therapy induced immunomodulatory, antiproliferative, and proapoptotic activities that were effective in the control of tumor growth, and reduced the expressions of transforming growth factor-beta (TGF-beta) and tissue inhibitor of metalloproteinase-1 (TIMP-1), leading to amelioration of liver cirrhosis. These results suggest that IFN-alpha gene therapy is a promising strategy to treat HCC patients who have concomitant liver cirrhosis.