Poly A:U-induced secretion of T-lymphocyte helper factors

Studies on interference with tolerance induction in T cells

The mechanism of T-cell tolerance to a thymus-dependent antigen was examined, using the adjuvant polyadenylic-polyuridylic acid (poly A:U). In adoptive transfer experiments, thymus cells obtained from donor mice 2 days after treatment with a tolerogenic dose of bovine gamma-globulin (sBGG) did not cooperate with bone marrow (BM) cells in irradiated recipients challenged with aggregated BGG (aBGG). In contrast, thymus cells from donors given sBGG plus poly A:U retained their helper activity, as assayed by hemagglutination and rosette formation of spleen cells. The effect of poly A:U in preventing tolerance induction was also demonstrable in the cortisone-resistant population, in that thymus cells from cortisone-treated donors that had received sBGG and poly A:U retained their helper function. The presence of suppressor cells and the effect of poly A:U on their stimulation were also examined. sBGG-treated thymus cells suppressed the response of BGG-primed spleen cells in lethally irradiated mice, whereas thymus cells from donors treated with sBGG and poly A:U were not suppressive. These observations show that poly A:U prevents tolerance induction and the development of suppressor activity in T cells.

Lack of a role for natural killer cells in early control of Brucella abortus 2308 infections in mice

Studies were conducted to determine if natural killer (NK) cells are important for early control of the virulent strain Brucella abortus 2308 following infection of mice with high or low challenge doses. Splenocytes from C57BL/10 and BALB/c mice that had been infected with the lower dose of B. abortus displayed increased cytotoxicity against YAC-1 cells during the first week after infection, while infection of C57BL/10 mice with the higher challenge dose either did not alter the level of NK cytotoxic activity or decreased it, depending upon the time postinfection. In vivo depletion of NK cells by monoclonal antibody anti-NK1.1 or polyclonal anti-asialoGM1 antiserum did not result in an increase in the number of brucellae recovered from the spleens or livers of the brucella-resistant C57BL/10 mice or from the spleens of the susceptible BALB/c mice during the first week after infection. Treatment of control mice with the NK-reactive antibodies, however, decreased killing of the NK-sensitive target YAC-1, indicating that the NK cell depletion regimes were effective. Our results suggest that NK cells are not crucial for early control of B. abortus 2308 even though they may be activated following infection. Further experiments indicated that treatment of C57BL/10 mice with poly(A:U) did not decrease the number of brucellae recovered from their spleens although it did decrease the CFU in livers of mice infected with the high challenge dose.

Efficacy of polyadenylic.polyuridylic acid in the treatment of chronic active hepatitis B

In order to assess whether polyadenylic.polyuridylic acid [poly(A).poly(U)] can be used as a new therapeutic agent for the treatment of chronic hepatitis B, 19 patients with histologically proven chronic active hepatitis B were injected intravenously with 100-150 mg of poly(A).poly(U) weekly for six weeks. Changes in alanine aminotransferase (ALT) levels, 2',5'-oligoadenylate synthetase (2'.5'-AS) activities and HBV markers were sequentially checked during and after treatments. Serum ALT levels were decreased gradually and 2'.5'-AS activities were significantly increased after initiation of poly(A).poly(U) injections. At the end of this trial (24th week) we have observed the normalizations of elevated ALT levels in 14 (73.7%), negative conversion of HBeAg in 11 (57.9%) and loss of HBV-DNA in 12 out of 19 patients (63.1%). Complete responses which had both normalization of ALT levels and negative conversion of HBeAg were noted in 11 patients (57.9%) and partial responses showing either normalization of ALT levels or negative conversion of HBeAg alone were in four out of 19 patients (21.1%). No notable adverse effects were observed during the treatments and follow-up period. It can be concluded that poly(A).poly(U) seems to be effective in the treatment of chronic active hepatitis B and has an advantage of being free of significant side effects.

Involvement of gamma interferon in antibody enhancement by adjuvants

In a previous study the adjuvant action of a monophosphoryl lipid A, a nontoxic derivative of endotoxic lipopolysaccharide (LPS), was found to be negated by a monoclonal anti-gamma interferon (anti-IFN-gamma) antibody. The present investigation centered on three other adjuvants of diverse microbial origins, testing for their capacity to affect the release of IFN-gamma as an explanation for their antibody-enhancing action. The adjuvant action of each of the three, a wild-type LPS, synthetic poly(A)-poly(U) complexes, and a synthetic muramyl dipeptide, n-acetylmuramyl-L-alanyl-D-glutaminyl-n-butyl ester (murabutide), was transferable by adjuvant-stimulated T cells to normal spleen cells on coculture. Supernatant fluids from these T cells contained increased levels of IFN-gamma. Addition of a monoclonal anti-IFN-gamma antibody to adjuvant-stimulated spleen cell cultures reduced the adjuvant action by approximately one-half. Removal of natural killer cells from spleen cell populations prior to culture with antigen had no effect on the enhancement induced by LPS and monophosphoryl lipid A. It was concluded that the enhancement induced by the adjuvants LPS, poly(A)-poly(U), and murabutide is mediated in part by their action on T cells resulting in release of IFN-gamma suggesting activation of a common transmembrane signal.