Competitive PCR for quantification of BM5d proviral DNA in mice with AIDS

Murine AIDS in C57BL/6 mice is caused by a unique mixture of murine leukemia viruses. We report the use of a competitive PCR to detect and quantitate BM5d proviral DNA. This assay allowed discrimination among endogenous wild-type murine retroviruses and BM5d sequences. Furthermore, the method was subsequently used to evaluate the amount of BM5d in infected mice and in infected AZT (zidovudine)-treated mice, providing an effective way to quantitatively evaluate drug efficacy in the murine AIDS model.

Inhibition of murine AIDS by a new azidothymidine homodinucleotide

A new antiretroviral drug (azidothymidine homodinucleotide, AZTp2AZT), designed for the protection of macrophages against retroviral infection, was evaluated in a murine retrovirus-induced immunodeficiency model of AIDS (MAIDS) alone and in combination with oral azidothymidine (AZT). C57BL/6 mice were infected with the retroviral complex LP-BM5 and treated for 3 months by weekly administrations of 15 nmol of AZTp2AZT encapsulated into autologous erythrocytes for macrophage protection. AZTp2AZT treatment was found to reduce lymphoadenopathy (48%), splenomegaly (26%), and BM5d proviral DNA content in lymph nodes, spleen, and brain of 37%, 40%, and 36%, respectively, compared with untreated animals. AZT administration in drinking water (0.25 mg/ml) was more effective than administration of AZTp2AZT encapsulated into erythrocytes in reducing lymphoadenopathy, splenomegaly, gammaglobulinemia, and proviral DNA content in lymph nodes, but it caused a reduction in erythrocyte count and hematocrit levels. Although combined treatments do not provide additive responses in the several parameters investigated, they were found to be much more effective in reducing the proviral DNA content in brain (67%) than were monotherapies. Furthermore, no apparent signs of hematotoxicity were observed. Thus, macrophage delivery of antiviral drugs may contribute to brain protection from retroviral infections by mechanisms other than those exerted by oral AZT administration.

Antiretroviral effect of combined zidovudine and reduced glutathione therapy in murine AIDS

A combination of antiretroviral drugs acting at different points in the virus replication cycle was evaluated in a murine retrovirus-induced immunodeficiency model of AIDS (MAIDS). Intramuscular administration of high doses of reduced glutathione (GSH, 100 mg/mouse/day) and AZT (0.25 mg/ml in drinking water) was found to reduce lymphoadenopathy (92%), splenomegaly (80%), and hypergammaglobulinemia (90%) significantly more than AZT alone. Combined treatment resulted in a reduction in proviral DNA content of 69, 66, and 60%, respectively, in lymph nodes, spleen, and bone marrow. Furthermore, the stimulation index of B cells was also significantly higher in animals receiving GSH and AZT whereas additional responses were not observed in the T cell stimulation index and blood lymphocyte phenotype analyses. In conclusion, the administration of high doses of GSH and AZT, a new combination of antiviral drugs, seems to provide additional advantages compared to single-agent therapy.

Up-regulation of the ubiquitin-conjugating and proteolytic systems in murine acquired immunodeficiency syndrome

Lymphoproliferation, chronic B-cell activation resulting in hypergammaglobulinemia, and profound immunodeficiency are prominent features of retrovirus-induced murine acquired immunodeficiency syndrome (murine AIDS). Here we demonstrate that in murine AIDS the ATP-dependent and ubiquitin-dependent proteolytic system is strongly affected, at least in the lymph nodes of infected mice. Solid-phase immunochemical assays show that the ubiquitin-conjugate pools increase by about threefold 10 weeks after infection, then decline slightly 15 weeks after infection to a twofold increase. Accumulation of ubiquitin conjugates is accompanied by induction of the ubiquitin-conjugating pathway, involving several carrier-protein isozymes (E2), mainly 14-kDa E2 and 17-kDa E2. Furthermore, accumulation of ubiquitin conjugates and induction of the conjugating system are coincident with an increase in the proteolytic activity supported by the 26S proteolytic complex. However, 15 weeks after infection, when the conjugation rate and levels of ubiquitin conjugates decrease, proteasome activity returns to values similar to those of the control, suggesting that a higher proteosomal activity is no longer needed. The concerted induction of the ubiquitin-conjugating and proteolytic systems in murine AIDS apparently does not involve the breakdown of viral products nor is it supported by virus-coded events, but probably arises as a cellular response to viral infection.

Inhibition of murine AIDS by reduced glutathione

The imbalance of the redox state in cells and body fluids in HIV-1-infected patients may result in progression of the disease as well as in immunologic disfuctions. In this report, we have evaluated whether the direct administration of high doses of reduced glutathione (GSH) exerts any antiviral activity and/or improves immune functions in a murine immunodeficiency animal model. Intramuscular administration of 50 or 100 mg GSH/mouse for five consecutive days weekly to LP-BM5-infected mice did not show local or systemic signs of acute toxicity. During the first 3 weeks from infection, a period in which clinical signs of disease were not yet detectable, GSH significantly reduced the viral load in lymph nodes and spleen as evaluated by a PCR semiquantitative assay of the proviral DNA content. At 10 weeks a GSH concentration-dependent reduction of splenomegaly, lymphadenopathy and hypergammaglobulinemia was evident in all treated mice. Evaluation of proviral DNA content showed that GSH was effective in inhibiting LP-BM5 infectivity in lymph nodes, spleen, and bone marrow at 100 mg/day, while it was less effective when administered at 50 mg/day. At 10 weeks some animals receiving the highest GSH dose died, thus only the mice receiving 50 mg GSH were followed up to 15 weeks without signs of toxicity. In this case, almost not significant differences among infected untreated or treated animals were observed. Thus, GSH is effective in reducing the proviral DNA load in the first period of infection. These data and the failure of sulfhydril supplementation to further counteract the progression of disease after 10 weeks of infection suggest that combinations of GSH and other antiviral agents may be useful for improving current antiviral therapies.

Antiviral efficacy and toxicity of ribavirin in murine acquired immunodeficiency syndrome model

The antiretroviral efficacy and hematotoxicity of ribavirin, a guanosine analogue, have been evaluated in mice infected with the LP-BM5 virus pool [murine acquired immunodeficiency syndrome (MAIDS) model]. Doses ranging from 6.25 to 200 mg/kg/day were injected intraperitoneally twice a day for 6 weeks to infected mice. Drug treatment induced a significant protection against splenomegaly and lymphadenopathy at doses > or = 25 mg/kg. Moreover, doses starting at 50 mg/kg protected against hypergammaglobulinemia, minimized the loss of spleen CD8+ T cells, and reconstituted the capacity of splenocytes to proliferate in response to concanavalin A. The spleen and cervical lymph node architectures were protected, and a reduction in the emergence of germinal centers was observed at 50 mg/kg ribavirin. Hematotoxicity appeared at doses > or = 50 mg/kg ribavirin, and severe anemia was predominant only at doses of 100 and 200 mg/kg. This study shows that ribavirin protects mice against the effects resulting from retrovirus infection at doses of > or = 50 mg/kg in a MAIDS model and induces severe hematotoxicity at doses > or = 100 mg/kg.

Inhibition of murine AIDS by combination of AZT and dideoxycytidine 5'-triphosphate

SUMMARY

A combination of antiretroviral drugs acting on different cell types (lymphocytes and macrophages) was evaluated in a murine retrovirus-induced immunodeficiency model of AIDS (MAIDS). In a first experiment, C57BL/6 mice were infected with a single i.p. administration of LP-BM5 and treated with 0.125 or 0.25 mg/ml AZT in drinking water for 3 months. AZT treatment was found to reduce lymphadenopathy (60 and 65 percent, respectively), splenomegaly (37 and 50 percent, respectively), and hypergammaglobulinemia (6 and 50 percent, respectively). Furthermore, at the highest AZT concentration, BM5d proviral DNA content in lymph nodes and in the spleen showed a reduction of 78 and 70 percent, respectively, compared to untreated animals. In a second experiment, infected mice were treated with AZT (0.25 mg/ml in drinking water) and with 2',3'-dideoxycytidine 5'-triphosphate (ddCTP) encapsulated into autologous erythrocytes for macrophage protection. Combined treatments resulted in a further reduction of lymphadenopathy (a further 33 percent with respect to the single treatment of AZT) and splenomegaly (a further 28 percent respect to the single treatment of AZT) but not of gammaglobulinemia. Proviral DNA in lymph nodes and spleen showed a reduction of 82 and 77 percent, respectively, compared to infected mice. Stimulation index of T cells was also significantly increased in animals receiving both treatments versus AZT only. In conclusion, the selective administration of antiviral drugs that preferentially protect different cell types seems to provide additional advantages compared to single-agent therapy.