Rauscher Leukemia Research Articles

Immune response in animals with experimental Rauscher leukemia to mononuclear stem cells and Subalin

The results of the effect of immunomodulating biologically active drugs on the immune response of laboratory animals are presented. To study the processes, a model of experimental Rauscher leukemia was used in mice of pure lines. The morphological changes in the peripheral blood of Bagg Albino C (BALB / c) mice with experimental Rauscher's leukemia after the use of mononuclear stem cell and Subalin preparations were studied. Groups of animals were formed for the experiment: control and three experimental (infected). The animals of the experimental groups were examined simultaneously by intraperitoneal injection of the appropriate biomaterial. It was found that the use of mononuclear stem cells and Subalin does not prolong the life of infected animals. During the observation period, all infected mice died within 11 months. After infection with Rauscher leukemia, a quantitative and qualitative change in blood cells occurs. A shift to the left was noted in the leukogram, eosinophilia and monocytosis were revealed. In the process of experimental reproduction of the chronic form of the disease, the size of the spleen of mice was estimated. An increase in the spleen was observed in the experimental group of animals infected with the Rauscher leukemia virus on the 4th week after infection. It was found that Subalin has a pronounced effect on the leveling of hematological parameters and leukopoiesis in infected mice. In the group where stem cells were used together with the antigen, a slight decrease in the number of lymphocytes and an increase in stab and segmented neutrophils were recorded. In the experimental groups with the use of mononuclear stem cells and Subalin, an increase in young cells in the leukogram was noted.

Abstract 5090: Epitope mapping of mouse TERT for vaccine development

Abstract Telomerase reverse transcriptase (TERT) is one of two essential components of telomerase, an enzyme complex that generates and maintains telomeres. Telomerase is expressed mainly in embryonic and adult stem cells. Telomere biology has recently been implicated in the pathogenesis of a variety of diseases, and mutations in telomerase components result in a predisposition to solid malignancies. More recent findings show that TERT is not only expressed in late stage primary tumor cells and metastatic cells, but also expressed in incipient cancer stem cells and/or tumor-initiating cells, indicating that TERT has essential roles at every stage of tumorigenesis. However, the clinical benefit of a TERT (hTERT)-targeting vaccine, given as a single agent or in combination with chemotherapeutic agents, has been limited in patients with advanced cancer, possibly due to insufficient epitope coverage as well as tumor-induced immune suppression. Thus, targeting TERT in tumor-initiating cells in early stage lesions may be more effective in preventing cancer development and progression. To develop cancer preventive TERT vaccines, novel immunogenic epitopes must be first identified and evaluated in a relevant preclinical model of tumorigenesis. The goal of this project is to identify the epitopes of mouse TERT with high immunogenicity using MHC I-peptide binding assay by flow cytometry analysis. The in vitro peptide-induced MHC Class I stabilization assay was carried out using RMA/S cell line, which was derived from a Rauscher leukemia virus-induced C57BL/6 T cell lymphoma and is deficient in transporter associated with antigen processing (TAP). Results of screening the overlapping peptide library will be presented. Funded by NCI Contract No. HHSN261200800001E Citation Format: Yurong Song, Jason Marshall, Travis Kerr, Ligia Pinto, Shizuko Sei, Robert Shoemaker. Epitope mapping of mouse TERT for vaccine development [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 5090.

МОРФОЛОГИЧЕСКИЕ ИЗМЕНЕНИЯ ПЕРЕФЕРИЧЕСКОЙ КРОВИ У МЫШЕЙ BALB/C ПРИ РАЗВИТИИ ЭКСПЕРИМЕНТАЛЬНОГО ЛЕЙКОЗА РАУШЕРА И ОДНОВРЕМЕННОМ ДЕЙСТВИИ ПРЕПАРАТА «СУБАЛИН»

Were demonstrated morphological changes, that happen in peripheral blood under effect of the drug Subalin in trial group of BALB/c mice, infected by a Rauscher leukemia virus (RLV). The RLV causes the death of 100% of the animals. The introduction of the drug Subalin did not prolong lifespan of the contaminated animals and their death rate did not reduce. The RLV generates an increasing erythropenia and leukopenia in the hyperplastic period of disease. The amount of leucocytes of contaminated animals restores during the terminal stage of leukosis. The leukogram of the infected mice is characterized by intensification of the degenerative left shift, eosinophilia and monocytosis. Under effect of the Subalin occurs the leveling of hematological indexes and leukopoiesis of the RLV-infected mice. The use of the drug Subalin among mice infected with RLV, results in stabilization of hematological indexes and leukopoiesis. Increase in amount of metamyelocytes is observed in the terminal period among the infected mice.

Bone marrow transplantation therapy using resistant donors for retrovirus-induced leukaemia in mice.

Infection with Rauscher leukaemia virus (RLV) causes erythroleukaemia, anaemia, viraemia, and splenomegaly, features which develop very quickly in mice of strains susceptible to RLV but more slowly or not at all in strains resistant to RLV. We compared the effects of bone marrow transplantation (BMT) of donor cells obtained from a mouse strain resistant to the virus with the effects of BMT of donor cells obtained from strains susceptible to the virus, in recipient virus-susceptible mice which had previously been inoculated with RLV. Our results indicated that bone marrow transplantation from a marrow-resistant donor, but not from a susceptible donor, delayed the expression of leukaemia and delayed death, although such treatment did not appear to inhibit viral infection in susceptible recipients.

Virus inactivation studies using ion beams, electron and gamma irradiation

Known methods of virus inactivation are based on the chemical action of some substances such as acetylethylenimine, betapropiolactone, glycidalaldehyde, formaldehyde, etc. In such a process, the viral suspension should be kept at room or higher temperatures for 24–48h. Under these conditions, physical and chemical agents act to degrade the virus antigenic proteins. On the contrary with ionizing radiations at low temperatures, the treatment does not cause such degradation allowing the study of different viral functions.In this work, particle (α, d and ß) and γ irradiations were used for partial and total inactivation of Foot and Mouth Disease Virus (FMDV), Rauscher Leukemia Virus (RLV) and Herpes Simplex Virus (HSV). Obtention of the D37 dose from survival curves and the application of the target theory, permitted the determination of molecular weight of the nucleic acid genomes, EBR values and useful information for vaccine preparation.For RLV virus, a two target model of the RNA genome was deduced in accordance with biological information while from data from the literature and our own work on the structure of the scrapie prion, considering the molecular weight obtained by application of the theory, a new model for prion replication is presented, based on a trimer molecule.

Generalized immunosuppression: how viruses undermine the immune response.

Following infection, a virus must battle against the host's immune response. Viruses have developed many ways to escape immune surveillance and downregulate the host's immune response. Some viruses cause a generalized immunosuppression, thereby inhibiting or depressing the immune response towards themselves as well as towards unrelated pathogens. This review will focus on the mechanisms involved in the three main human viral infections causing immunosuppression: measles, human immunodeficiency virus and cytomegalovirus. We will also discuss what has been learned from the extensively studied mouse models of viral-induced immunosuppression: lymphocytic choriomeningitis virus and Rauscher leukemia virus. All of these viruses that induce generalized immunosuppression appear to do so by very similar mechanisms. They hinder antigen presentation to T cells and/or hematopoiesis. We will highlight the similarities in the viral targets as well as present evidence for alternate mechanisms.

Retrovirally induced switch from production of IL-12 to IL-4 in dendritic cells.

Dendritic cells (DC) in HIV-1 infection show a reduced capacity to stimulate primary T cell proliferation. Exposure of bone marrow-derived DC to Rauscher leukemia virus (RLV) provides a mouse model for studying retrovirally induced reduction in stimulatory capacity for T cells. Treatment with IL-12, a cytokine that promotes the development of Th1 cells, has been postulated as a treatment for AIDS and is effective at restoring cell-mediated immunity in mice infected with mouse AIDS virus or with RLV (see Knight, S. C. and Patterson, S., Annu. Rev. Immunol. 1994. 15: 593-615 for references). Here we studied the direct effect of RLV and of IL-12 on bone marrow-derived DC. Normal DC produced IL-12 and IL-10 and stimulated primary allogeneic T cell proliferation. Exposure of DC to RLV caused reduced production of IL-12, production of IL-4 was seen in DC for the first time and T cell stimulation was inhibited. Addition of IL-12 reinstated and enhanced IL-12 synthesis in RLV-treated DC, abrogated production of IL-10 and IL-4 and restored stimulatory activity. Manipulation of cytokine production in DC could be a stratagem that has evolved in the retrovirus to avoid stimulation of cellular responses.

Interleukin-12 administration in retroviral infection of mice increases the potential to produce functional dendritic cells from bone marrow stem cells

Rauscher leukaemia virus (RLV) infection in mice causes production of lymph node and skin dendritic cells (DC) that fail to stimulate a primary mixed leukocyte reaction (MLR). Treatment of mice with IL-12 around the time of infection results in DC with normal stimulatory function (N.J. Williams, J.J. Harvey, I. Duncan, R.F.G. Booth, S.C. Knight, Cell Immunol. 183 (1988) 121–130). Here we derived DC from mouse bone marrow by culture with granulocyte macrophage colony-stimulating factor (GM-CSF) and tumour necrosis factor-alpha (TNF- α) for 10–12 days; DC were generated from bone marrow cells taken from normal mice, from mice injected 15 days earlier with RLV or from those receiving RLV plus five daily doses of 100 ng of IL-12 starting 2 days before infection. Infection of the DC with RLV was assessed from nested PCR with doubling dilutions of DNA and the capacity of DC to stimulate a MLR was tested. DC derived from bone marrow of IL-12 treated animals showed at least twice the level of infection with RLV as those from non-treated animals although infection never exceeded 20% of the cells. DC derived from bone marrow of mice given RLV caused negligible stimulation of the MLR but those from mice additionally treated with IL-12 functioned normally. Thus, treatment of mice with IL-12 promoted the potential of stem cells taken 12 days after the last IL-12 injection to develop into functional DC despite increased infection with virus. Treatment of mice with IL-12 may have a long term effect on the potential growth of DC from stem cells which may contribute to the potency of this cytokine in promoting cell mediated immune responses.

Interleukin-12 Restores Dendritic Cell Function and Cell-Mediated Immunity in Retrovirus-Infected Mice

The effects of IL-12 treatment on the defects in DC function and on the reduced cell-mediated immunity induced in mice infected with Rauscher leukemia virus (RLV) were studied. DC from RLV-infected mice failed to stimulate significant allogeneic T cell proliferation but T cells from RLV-infected mice showed normal responses to allogeneic DC. In RLV-infected mice treatment with 5 doses of 100 or 300 ng IL-12 around the time of infection resulted in DC that stimulated normal T cell proliferation. Treatment of mice with 300 ng IL-12 but not 100 ng reduced T cell responses. RLV-infected mice showed reduced delayed hypersensitivity to a contact sensitizer. Infected animals receiving the low dose of IL-12 which allowed normal DC and T cell function gave normal delayed hypersensitivity reactions; IL-12 thus resulted in both normal T cell stimulation by DC and cell-mediated immunity. A failure of T cell stimulation by DC is associated with immunosuppression in retrovirus infection and the enhanced capacity of DC to stimulate T cells after IL-12 treatment may be beneficial.

Mechanism of Dendritic Cell Dysfunction in Retroviral Infection of Mice

Dendritic cells (DC) from mice infected with the murine retrovirus Rauscher leukaemia virus (RLV) are poor stimulators of allogeneic and syngeneic T cells and express lower, but still significant, levels of MHC class II. In this paper we further investigated the mechanism of the dysfunction of DC. DC from infected animals did not cause anergy of T cells during coculture for 3 or 6 days. They did not release a substantial amount of soluble factors which could suppress T cell responses. The low T cell responses on stimulation using RLV-infected DC could be overcome by the addition of control DC. Pretreatment of these control DC with monoclonal antibody against MHC class II molecules completely blocked their ability to restore stimulation of T cells in the presence of infected DC. However, antibody against MHC class I or mismatched MHC class II molecules did not prevent restoration of function. The reduced labeling of surface MHC class II molecules previously reported was shown to reflect a loss in total class II molecules within the cells; MHC class I levels were unaltered by exposure to the virus. In DC from RLV-infected mice biosynthesis of MHC class II was decreased by around 50% at the transcriptional level in comparison with β-actin. Thus, the down-regulation of surface class II molecules observed in DC following RLV infection is a consequence of a specific block in its biosynthesis and the failure of DC to stimulate T cells may be a direct consequence of the reduced class II levels. Since reduced stimulation by DC is also seen in HIV-1 infection in humans we speculate that a similar mechanism might operate in retroviral infection in man.

The use of 212P b-labeled monoclonal antibody in the treatment of murine erythroleukemia

Purpose : The goals of this study were to learn whether the DOTA chelator was useful for targeting lead radionuclides ( 203,212Pb) to cells and tissues invaded by the Rauscher leukemia virus (RVB3) and to investigate the therapeutic efficacy of targeted 212Pb in treating the murine leukemia. Methods and Materials : Five to 6-week-old BALB/c mice were inoculated i.v. with RVB3. This virus causes marked splenomegaly and death by day 13 and day 70 postinfection, respectively. Biodistribution, tumor targeting, and toxicity studies were performed using varying doses of 212Pb-DOTA-103A. A heavy metal chelator, DMPS, was administered orally and parenterally in two phases of the toxicity study. Results : Biodistribution studies showed marked tumor targeting (58% ID/g spleen) in mice treated with 203Pb-103A as compared to mice treated with control antibody B3 (4.6% ID/g spleen). Histologic cure was achieved in all leukemic mice treated with 20 μCi 212Pb-103A; however, all of the mice died with leukopenia and secondary bacterial infections due to severe bone marrow toxicity. Nonleukemic mice and mice treated with 20 μCi 212Pb-B3 experienced less marrow toxicity and longer survival. Coadministration of the heavy metal chelator did not diminish the bone marrow toxicity. Conclusion : An effective, nonlethal dose could not be established to treat this tumor. The severe bone marrow toxicity associated with this radionuclide may limit its usefulness in systemic radioimmunotherapy.

Phosphatidylazidothymidine and phosphatidyl-ddC: assessment of uptake in mouse lymphoid tissues and antiviral activities in human immunodeficiency virus-infected cells and in Rauscher leukemia virus-infected mice

During the early stages of human immunodeficiency virus (HIV) infection, although symptoms are absent and viral replication in peripheral blood mononuclear cells is low, substantial levels of HIV replication can be documented in lymphoid tissue [G. Pantaleo, C. Graziosi, J.F. Demarest, L. Butini, M. Montroni, C.H. Fox, J.M. Orenstein, D.P. Kotler, and A.S. Fauci, Nature (London) 362:355-358, 1993, and J. Embretsen, M. Zupancic, J.L. Ribas, A. Burke, P. Racz, K. Tenner-Tacz, and A.T. Haase, Nature (London) 362:359-362, 1993]. This observation suggests that earlier treatment of HIV infection may be indicated and that strategies for enhancing drug targeting to the lymphoid tissue reservoris of HIV infection may be beneficial. To address this issue, we synthesized dioleoylphosphatidyl-ddC (DOP-ddC) and dipalmitoylphosphatidyl-3'-azido-3'-deoxythymidine (DPP-AZT), phospholipid prodrugs which form lipid bilayers and which are readily incorporated into liposomes. The anti-HIV activity of DOP-ddC was similar to that of ddC in HIV type 1-infected HT4-6C cells, but DPP-AZT was considerably less active than AZT in HT4-6C cells. Liposomes containing DOP-[3H]ddC or DPP-[3H]AZT administered intraperitoneally to mice produced greater levels of total radioactivity over time in plasma, spleen, and lymphoid tissue relative to the results with [3H]ddC and [3H]AZT, respectively. DPP-AZT administered intraperitoneally in liposomes as a single daily dose to mice infected with Rauscher leukemia virus prevented increased spleen weight and reverse transcriptase levels in serum with a dose-response roughly comparable to that of AZT given continuously in the drinking water. DOP-ddC, DPP-AZT, and lipid conjugates of other antiretroviral nucleosides may provide higher levels of drug over time in plasma and in lymph nodes and spleen, important reservoirs of HIV infection, and may represent an interesting alternative approach to antiviral nucleoside treatment of AIDS.

Murine Retrovirus Induces Defects in the Function of Dendritic Cells at Early Stages of Infection

The infection and function of lymph node dendritic cells (DC) were analyzed at different time points of Rauscher leukemia virus infection in mice (3, 7, 14, and 21 days). Infection of DC was apparent after 3 days and significant infection (1-10% of the DC population) was documented after 7 days. DC from infected mice as early as 3 days postinfection had a reduced ability to stimulate allogeneic normal T cells in the mixed lymphocyte reaction. T cells did become infected during the coculture but block of cross-infection of T cells by zidovudine did not abolish the inhibitory effect. Other DC-dependent responses were also reduced on infection including DC-stimulated responses to influenza virus. ConA and PMA induced an increase in [Ca2 +] i level in DC from control mice. A low baseline level of [Ca 2+] i in DC from infected mice and reduced calcium mobilization upon ConA stimulation was found at all periods of infection. Ultraviolet-inactivated Rauscher leukemia virus failed to provoke significant changes in DC function in vivo. Six or 7 days after RLV infection DC expressed lower levels of Ia d but not H2D d molecules in parallel with lower expression of some adhesion molecules (CD18, CD54, CD44). No differences in expression of B7 surface antigen between control and infected mice were obtained. We did not find any evidence for the induction of apoptosis of naive syngeneic or allogeneic T cells by infected dendritic cells. The changes in DC function may have implications for the pathogenesis of retroviral infections including HIV infection.

Sodium Deoxycholate Exerts a Direct Destructive Effect on HIV and Influenza Viruses in vitro and Inhibits Retrovirus-Induced Pathology in An Animal Model

The bile salt sodium deoxycholate had a virucidal effect on influenza, Rauscher leukaemia and HIV-1 viruses, reducing virus infectivity by a maximum of 6 logs TCID50 ml−1 after 1 h incubation at 37 °C with 50 μg ml−1 of the compound. Electron microscopy demonstrated directly that sodium deoxycholate and other bile salts perturbed influenza virus structure causing partial or complete disruption of the virion lipid membrane, thus allowing entry of phosphotungstate dye to the virion interior. Parenteral administration of sodium deoxycholate (14 mg kg−1) to Balb/C mice abrogated pathology caused by Rauscher leukaemia virus replicating in the spleen and influenza virus replicating in the lung. Bile salts may also have clinical potential as topical virucidal agents at the point of entry of enveloped viruses and particularly against HIV.

New lipophilic alkyl/acyl dinucleoside phosphates as derivatives of 3′-azido-3′-deoxythymidine: Inhibition of HIV-1 replication in vitro and antiviral activity against Rauscher leukemia virus infected mice with delayed treatment regimens

The antiretroviral activity of two new lipophilic derivatives of azidothymidine (AZT), N 4-hexadecyl-2′-deoxyribocytidylyl-(3′-5′)-3′-azido-2′,3′-deoxythymidine( N 4-hexadecyldC-AZT) and N 4-palmitoyl-2′-deoxyribocytidylyl-(3′-5′)-3′-azido-2′,3′-deoxythymidine( N 4-palmitoyldC-AZT) was evaluated in comparison to AZT. In vitro the drugs were tested in human immunodeficiency virus 1 (HIV-1) infected CD4 + HeLa and H9 cells. The in vivo antiviral effect of these derivatives was analysed in Rauscher leukemia virus (RLV) infected mice. The derivatives were incorporated into small liposomes. In vitro both derivatives inhibited virus proliferation in both HIV-1 infected cell lines in a similar dose-responsive manner as AZT. In a plaque reduction assay, using HeLa cells, the IC 50 values were 0.035 μM for AZT, 0.5 μM for N 4-hexadecyldC-AZT and 4.5 μM for N 4-palmitoyldC-AZT, whereas p24 antigen analysis on H9 cells gave IC 50 values of 0.005 μM, 0.05 μM and 0.05 μM, respectively. RLV infected mice were treated with intermittent schedules i.p. or i.v. on days 1, 6, 11, and days 16 or 0, 3, 7, and 11 after infection. Regimens with further delayed drug application were on days 3, 7, and 11 and 7 and 11 only. While i.p. treatment with total doses of 380–1140 mg/kg free AZT resulted in 10–30% inhibition of RLV induced splenomegaly, the derivatives gave inhibitions of 37–94%. Late onset of treatment with the derivatives was significantly more effective as compared to free AZT. Intravenous treatment with N 4-hexadecyldC-AZT was effective, but with AZT was inactive. The discrepancy in antiviral activity of the AZT derivatives found between the in vitro and in vivo test systems emphasizes the importance of investigating the activity of drug derivatives in vivo.

Effects of murine leukemia viruses on the function of dendritic cells

In asymptomatic human immunodeficiency virus-1 infection T cells respond normally to allogeneic dendritic cells (DC), but DC show reduced stimulatory capacity. By contrast in HTLV-1 infection no significant changes in allogeneic stimulation were seen but DC-stimulated activity of autologous T cells. In seeking animal models relevant to these diseases the effects of two murine leukemia retroviruses, Rauscher leukemia virus (RLV) and Moloney leukemia virus (MLV) on the function of dendritic cells and T cells in a primary mixed leucocyte reaction have been tested. Treatment by RLV in vitro suppressed the ability of DC to stimulate allogeneic T cells from healthy animals. MLV at the same concentration did not significantly affect the ability of DC to stimulate allogeneic T cells, but provoked considerable enhancement of the low level stimulation by DC in the syngeneic system. Similar results were obtained following in vivo exposure to viruses. Two pieces of evidence suggested that these effects were due to impairment of DC function and were not operating through infection of T cells. Firstly, exposure of T cells directly to virus in vitro and in vivo before stimulation with untreated allogeneic DC caused no significant alteration in T cell activity. Secondly, the impact of murine leukemia virus on DC function was not abrogated when infected DC were added to normal T cells and cultured in the presence of zidovudine. Treatment of DC by RLV caused a decrease of cluster formation with allogeneic T cells. No statistically significant influence of MLV was observed on cluster formation after 3-h of incubation in the allogeneic system. However, after 18-h incubation MLV-treated DC formed fewer clusters with T cells than untreated DC. At the same time a stimulatory effect of MLV on DC cluster formation with syngeneic T cells was found. Considerable decrease was found in major histocompatibility complex class II antigen and LFA-1 receptor expression on the DC surface in mice infected by RLV. MLV induced no significant changes. These mouse retroviruses can therefore cause changes in DC function similar to those already reported using human retroviruses and may provide models for studying their effects.

Antitumor effects of binuclear ferrocene derivatives

AbstractOn the basis of an earlier model of chemical carcinogenesis, the antitumor activity of the mono‐, bi‐ and poly‐nuclear ferrocene derivatives ferricenium tri‐iodide (1), ferricenium tetrachloroferrate (2), 1, 1′‐diethylferricenium triiodide: (3), N‐(ferrocenylmethyl)hexamethylenetetramine tetrafluoroborate (4), bis(ferrocenylmethyl)benzotriazolium tetrafluoroborate (5), bis(ferrocenyl‐α‐ethyl)benzotriazolium tetrafluoroborate (6) and bis(ferrocenylmethyl)‐2‐methylbenzimidazolium tetrafluoroborate (7), and the oligomer (—Fc—CH2—Fc+˙—CH2—)7–8− (PF6)7–8 (8) was studied in vivo (FcC10H8Fe). The tumor models studied included MCH‐11 (mouse sarcoma induced by methylcholantrene), P‐815 (mouse mastocytoma of DBA/2 origin) and virus‐induced Raucher leukemia (RLV). The cytotoxic effects of these preparations were examined against in vitro cultured normal murine cells (line L‐929). The binuclear ferrocene derivatives 5, 6 and 7 inhibited the development of experimental tumors in mice. Ferricenium tri‐iodide (1) was effective in Rauscher leukemia. Kinetic dependencies for most complexes had a two‐phase character: the region of inhibition of tumorogenesis was followed by a region in which the complexes accelerated the development of this process. The link between the structure of compounds 1–8 and their antitumor effects is discussed.

Sulfonic Acid Dyes

Over 50 different commercially available sulfonic acid-containing dyes were analyzed for their ability to prevent HIV-1-induced cell killing and in inhibiting HIV-1 replication. Compounds of remarkably similar structure, but with differing patterns of sulfonic acid group substitutions, had a wide range of potency in inhibiting HIV-1. Chicago sky blue (CSB) was highly effective in the inhibition of HIV-1 with less toxicity to CEM-SS cells than most of the other sulfonated dyes tested. Synthesis of CSB was undertaken to produce a product greater than 98% pure and this compound was used to elucidate the possible mechanisms by which this class of structurally related compounds inhibits HIV-1. Addition of CSB to cells infected at high multiplicity at any time up to 24 h after infection, unlike dideoxycytidine (ddC) or oxathiin carboxanilide (OC), inhibited HIV-1-induced cell killing. Other postinfection time course studies revealed that CSB had to be present for 24 h or longer immediately after infection to be protective. Virus binding to cells occurred in the presence of CSB, but the requirement for virion envelope-cell membrane fusion was delayed. CSB was a potent inhibitor of the reverse transcriptase (RT) of both HIV-1 and HIV-2, although it was less active against HIV-2 in a cell killing-based assay. CSB also inhibited Rauscher and LP-BM5 murine leukemia viruses. CSB appears to disrupt the interaction between viral proteins and cell membranes, both in the fusion step early in the infection cycle and in the development of syncytia in the late stages of virus infection.

Effect of Interleukin-1, GM-CSF, Erythropoietin, and Lithium on the Toxicity Associated With 3′-Azido-3′-Deoxythymidine (AZT) In Vitro on Hematopoietic Progenitors (CFU-GM, CFU-MEG, and BFU-E) Using Murine Retrovirus-Infected Hematopoietic Cells

The drug 3'-azido-3'-deoxythymidine (AZT), a synthetic thymidine analogue, has been used clinically in the management of acquired immune deficiency syndrome (AIDS). The drug is an effective antiviral agent due to its ability to block reverse transcriptase activity. This action of AZT was demonstrated in the Rauscher leukemia virus (RLV)-induced murine erythroleukemia model system. Unfortunately, associated with AZT has been the development of hematopoietic toxicity manifested by anemia, neutropenia, and overall bone marrow suppression. Hematopoietic growth factors (GM-CSF, erythropoietin), cytokines (interleukin-1), and agents known to potentiate hematopoiesis (lithium) have been demonstrated to modulate drug and/or radiation-induced hematopoietic toxicity. We report the results of further studies designed to investigate the ability of GM-CSF, erythropoietin, interleukin-1, and lithium to modulate AZT toxicity on murine hematopoietic granulocyte-macrophage (CFU-GM), megakaryocytic (CFU-Meg), and erythroid (BFU-E) progenitors cultured from bone marrow and spleen cells from mice infected with RLV. Hematopoietic progenitors from either normal or RLV-infected animals when exposed to AZT demonstrated concentration-dependent toxicity and differed for each progenitor with BFU-E being the most sensitive (ID50 concentration, 5 x 10(-9) M) and CFU-GM the least sensitive (ID50 concentration, 5 x 10(-5) M). As has been previously demonstrated using normal murine hematopoietic progenitors, when cultured with RLV-infected marrow or spleen cells, addition of GM-CSF, Meg-CSF or erythropoietin failed to inhibit AZT toxicity in vitro on CFU-GM, CFU-Meg, and BFU-E, respectively. However, in the presence of interleukin-1 (recombinant human IL-1 alpha, 30 ngm) or lithium chloride (ultra-pure, 1.0 mM), AZT toxicity CFU-GM, CFU-Meg, and BFU-E cultured from RLV-infected marrow or spleen cells was reduced. These results further demonstrate interleukin-1 and lithium are effective in modulating the toxic action of AZT on hematopoietic progenitors and that RLV-infected animals serve as a useful viral model system to study the effect of agents capable of modulating hematopoiesis in the presence of the anti-viral drug AZT.

Protease Inhibitors as Potential Therapeutic Agents for AIDS

A decade since the epidemic of the acquired immunodeficiency syndrome (AIDS) was first recognized, a wealth of information has accumulated on the molecular biology of the causative agents, the human immunodeficiency viruses (HIV). Of particular interest is knowledge of the viral enzymes involved in the formation of new virus particles. Such enzymes constitute attractive targets for efforts aimed at selecting agents that interfere with virus multiplication and subsequent spread and pathogenesis. Already, several agents that inhibit the viral reverse transcriptase (e.g., nucleoside analogs such as Zidovudine) have proved to have a beneficial effect on the course off the disease, but their prolonged use has been associated with significant toxicity and the emergence of resistant mutants. A second enzyme that has recently attracted attention is the virus-coded protease. This enzyme is involved in the cleavage of viral precursor polyproteins into the final products that constitute the mature virus particle. Protease inhibitors interfere with the process of virus maturation which is required for the formation of infective virus particles. Several custom-made inhibitors with a high selective action against HIV protease have been produced recently. They are nonhydrolyzable peptide analogs that mimic the cleavage sequences of the natural substrate of the enzyme during the transition state of the cleavage reaction. It is hoped that a similar selectivity in vivo may make protease inhibitors a promising new category of AIDS therapeutics.