Combined treatments with interferon (alpha,beta) plus PGA1 to control early infection with HTLV-I in primary cord blood-derived mononuclear cells

Interferon (IFN) alpha and beta can activate an antiviral and immunomodulating response in primary cord blood-derived mononuclear cells (CBMC) exposed to infection with Human T-cell Leukemia Virus type I (HTLV-I), resulting in partial inhibition of early infection in vitro. On the other hand, PGA1, a PGE1-derived cyclopentenone prostaglandin, can inhibit in vitro the proliferation of virus-infected CBMC, preventing the emergence of the potentially transformed clone. In order to achieve a complete control of HTLV-I infection in this experimental model, we evaluated whether the antiviral activity of IFNs and the antiproliferative activity of PGA1 could be preserved in a combination therapy scheme. Recipient CBMC were treated with IFN alpha or beta (1000 IU/ml) at the onset of the co-culture with lethally irradiated virus-donor MT-2 cells, followed by multiple treatments with PGA1 (4 micrograms/ml every 4 days, starting on day 0) for 6 weeks post infection (p.i.). In PGA1-treated co-cultures the percentage of virus-positive CBMC was constantly doubled during culture time as well as the amount of viral transcripts and p19 virus core protein production were increased. The antiviral effects of IFNs, resulting in about a 50% reduction of the percentage of virus-positive CBMC and consequently in a partial inhibition of virus expression (HTLV-I transcription and p19 production) until 4 weeks p.i., were suppressed by multiple PGA1 treatments. However, the antiproliferative effect of PGA1 was enforced in IFN-treated co-cultures, leading to earlier control of proliferation of virus-infected cells. Interestingly, infection of CBMC with HTLV-I was associated with persistent expression of 70 kDa heat shock protein (HSP70), for at least 4 weeks p.i. IFNs and PGA1 showed antagonistic effects on HSP70 production in infected CBMC. In fact, production of HSP70 was suppressed (or prevented) in IFN-treated co-cultures, tested 2 and 4 weeks p.i. The fact that the expression of HSP70 is apparently suppressed (or prevented) by IFN treatment is surprising, since expression of this protein family has been associated with antiviral immunity. PGA1 could totally reverse the IFN-mediated suppression of HSP70 expression in these co-cultures. It is presently unclear whether HSP70 expression is directly involved in the control of proliferation exerted by PGA1 against virus-infected CBMC or is an epiphenomenon associated with inhibition of cell growth.

In vitro combined effects of human interferons and interleukin-2 on natural cell-mediated cytotoxicity

In vitro modulation of natural cell-mediated cytotoxicity (NCMC), following sequential treatment of human mononuclear cells (MNC) with cytokines was investigated. Recombinant Interleukin-2 (IL2) used in combination with interferons (IFNs) induced variable effects on the cytolytic function of different MNC preparations obtained from 16 healthy donors. When MNC were treated with IFNs on day 4, after IL2 induction of LAK cells, increase or no change in cytotoxic activity was found. On the other hand, either no change or decrease in LAK activity occurred when MNC were treated with IFNs on day 0 before exposure to IL2. In this case the effect of IFNs on NCMC did not correlate with their activity on cell proliferation or on TAC antigen expression. In conclusion the present study points out that the NCMC of MNC of healthy donors, subjected to IL2 treatment in vitro, can be significantly increased by IFNs. However this effect is largely schedule-dependent (i.e. detectable with IL2-IFNs but not with IFNs-IL2 sequence), and can be obtained in a relatively limited number of cases. Moreover it is suggested that these in vitro studies could provide preclinical bases for a rational approach to in vivo treatment with cytokine cascade in a clinical setting.

Antiviral activity of individual versus combined treatments with interferon alpha, beta and gamma on early infection with HTLV-I in vitro

We have shown previously that infection of mononuclear cells derived from neonatal cord (CBMC) or adult peripheral (PBMC) blood with HTLV-1 can be controlled in vitro by treatment with interferon (IFN) alpha, beta or gamma. The activity of IFNs was mainly related to the induction of an active antiviral competence in host's immune effector cells. The antiviral activity of IFN-boosted CBMC could be ascribed both to a positive regulation of cell-mediated immunity and to inhibition of viral infection. Data described herein provide further information on the mechanisms of the antiviral activity of IFNs and compare the activity of each type of IFN with the association of alpha + beta, alpha + gamma and beta + gamma IFNs, at a concentration of 100 or 1000 IU/ml. When added at the onset of the co-culture of CBMC with lethally irradiated, virus-donor MT-2 cells, IFNs could protect host CBMC by inhibiting HTLV-1 infection in terms of reduced proviral integration and a lower percentage of virus-positive cells, until 4 weeks of culture. Infection of CBMC was inhibited at a comparable extent by either individual or combined IFN treatments. However, a clearcut inhibition of HTLV-I transcription was found only when alpha 100 + beta 1000 IU/ml and especially alpha 1000 + gamma 100 IU/ml combined treatments were tested. When the chronically infected, virus-producing MT-2 cells were treated with IFNs, a remarkable inhibition of HTLV-I transcription was found only after multiple treatments. However, MT-2 cells became resistant to the antiviral activity of IFN gamma, but not to that of IFN alpha or beta. These data provide further information on the control of HTLV-I replication mediated by IFNs at different steps of the viral life cycle, being therefore relevant to the clinical use of combined IFNs in the treatment of acute infection. Moreover, IFNs could be used to prevent the establishment of a persistent infection, which is a prerequisite for developing adult T-cell leukemia (ATL) and/or virus-associated myelopathy.

Correlation between P19 presence and MHC class II expression in human fetal astroglial cells cocultured with HTLV-I donor cells

The possibility of a direct infection of human brain by HTLV-I, has been studied using an in vitro model. Human fetal astroglial cells were cocultivated with irradiated HTLV-I donor cell line MT-2, and assayed for the presence of HTLV-I core protein p19 after 1 week. Fifty-six per cent of GFAP positive astrocytes showed the viral core protein p19 and increased expression of Class II MHC antigens. Electron microscopy of astroglial cells exposed to HTLV-I revealed the presence of vacuoli-like structures containing viral core protein p19. Cell intermediate filament cytoskeleton was also disorganized. Even if this study does not provide direct evidence for virus replication inside astroglial cells, all these findings suggest that HTLV-I can indeed enter the cell and exert a cytopathic effect. Therefore the results of the present study are consistent with the hypothesis that astroglial cells could be involved in demyelination processes occurring in the HTLV-I associated neurological disorders, such as human associated myelopathy and tropical spastic paraparesis.

Comparative anti-viral and anti-proliferative activity of PGA1 and PGJ2 against HTLV-I-infected MT-2 cells

Prostaglandin (PG) A and J exert anti-viral and anti-proliferative effects in a number of experimental models. In particular, multiple treatments with PGAs prevent in vitro the clonal selection of HTLV-I-infected and potentially transformed cord-blood-derived mononuclear cells. Proliferation of HTLV-I-infected leukemic T cells is refractory in most cases to conventional anti-blastic therapy. We examined whether these cyclopentenone PGs might control cell proliferation and/or alter virus replication also in HTLV-I-transformed cells. We show that PGA1 and PGJ2 can exert powerful control of proliferation of the HTLV-I-immortalized, virus-producing MT-2 cell line, in a concentration-dependent fashion. Cells were preferentially arrested at the G1/S interface by treatment with PGA1 or PGJ2 without any detectable cellular toxicity. The anti-proliferative effect of PG treatment was independent of the growth phase of MT-2 cells, since both asynchronous and synchronous cells were sensitive to treatment. This effect was accompanied by an increase in the synthesis of a 70 kDa heat-shock protein (HSP70). However, synthesis of HSP70 was induced to a much greater extent by PGJ2 than by PGA1 at the same concentration. Neither PGA1 or PGJ2 inhibited the transcription of HTLV-I in MT-2 cells, but treatment with PGJ2, and not with PGA1, moderately inhibited the synthesis of viral proteins, i.e., p40 Tax and p19 core proteins. Moreover, infection of recipient K562 cells was significantly inhibited after pre-treatment of MT-2 cells with PGJ2 14 hr before or co-treatment at the onset of the co-culture with K562 cells. This effect was not obtained when MT-2 cells were repeatedly pre-treated with PGJ2 for 1 week before co-culturing. This suggests that reduced infection could be related to impairment of some step in virus-transmission phase.

Cytotoxic effects of dacarbazine in patients with acute myelogenous leukemia: a pilot study

BACKGROUND AND METHODS

Preclinical studies performed in our laboratory showed that mouse leukemias become highly immunogenic following in vivo treatment with Decarbazine. This observation led to a successful immunochemotherapy protocol in mice using Dacarbazine plus cytoreductive chemotherapy. Therefore an in vivo and in vitro pilot study was conducted in patients (pts) with resistant or relapsed acute myelogenous leukemia (AML). The DNA-repair enzyme O6-alkylguanine-DNA-alkyl-transferase (OGAT) and the in vitro chemosensitivity to Temozolomide, a Dacarbazine derivative, were evaluated in leukemic blasts.

RESULTS

Nine pts received Dacarbazine (0.4-0.8 g/sqm/day) on days 0, 1 and 2. On day 7, noticeable blast reduction occurred in 4 pts: pt 1 was in partial remission on day 21, pt 6 still showed bone marrow leukemia, pt 8 died of sepsis on day 8, pt 9 is still in aplasia on day 25. Low OGAT levels and consistent sensitivity to Temozolomide in vitro were found in the blasts of pts responsive to Dacarbazine. Subsequently, pts 1-7 underwent Ara-C (1g/sqm/day) plus Mitoxantrone (6mg/sqm/day) treatment for 6 days. Four pts entered complete remission after 27-45 days of aplasia. Failures were due to hypoplastic death, absolute drug resistance, or hypoplasia followed by blast cell regrowth.

CONCLUSIONS

These data point out that Dacarbazine can induce a marked reduction of blast cells as well as severe myelotoxicity in leukemic patients.

[Etiopathogenesis and therapeutic trends in adult T-cell leukemia associated with HTLV-I retrovirus]

HTLV-I (Human T-cell leukemia virus type I) has been the first human retrovirus identified and then associated with a definite pathological entity, a leukemic syndrome that specifically affects mature T-lymphocytes (ATL, adult T-cell leukemia), expressing CD3+, CD4+, CD8-, CD11- phenotype. This form of leukemia/lymphoma is endemic in southwestern islands of Japan, although at present the number of HTLV-I seropositive individuals has greatly increased, with a worldwide diffusion, following the expansion wave of the AIDS-associated HIV retrovirus. In fact, double seropositivity for both HIV and HTLV is frequently found among intravenous drug users. Although ATL leukemia or lymphoma occurs with a low frequency among HTLV-I seropositive individuals, it is likely that the evolution from a latent phase of infection to acute leukemia could be favoured by depression of immunosurveillance levels in the host. Therefore, special attention is required to prevent the diffusion of this retrovirus in adults, taking into consideration that newborn babies from seropositive mothers have to be considered at high risk for development of HTLV-I associated disease, on the basis of their immature immunocompetence.

Immuno-chemotherapy of advanced colorectal cancer with alpha-2a interferon and 5-fluorouracil. Immunopharmacological studies

Twelve patients with metastatic colorectal cancer received alternating cycles of low immunomodulating doses of alpha-IFN + 5-Fluorouracil (5-FU) or 5-FU alone. Hematological, biochemical and physical evaluation showed that both treatment cycles were well tolerated. However, transient fever and moderate flu-like symptoms were observed following alpha-IFN administration. Treatment with 5-FU alone produced long-lasting inhibition of CD8+ T lymphocytes, but did not depress NK activity (NKA). Combined treatment with alpha-IFN produced a short-term increase of NKA and antagonized the effect of 5-FU on CD8+ cells on day 5 of the cycle. Parallel studies on in vitro models showed antiproliferative effects of 5-FU on PHA-stimulated MNC and confirmed the preferential inhibition of CD8+ cells. Pretreatment with alpha-IFN did not reverse the effect of 5-FU on CD8+ lymphocytes, but partially protected MNC from the toxic effects of the drug. This was presumably due to the cytostatic effects induced by alpha-IFN on MNC before exposure to the cycle-specific antineoplastic agent. This investigation suggests that alpha-IFN could play a positive role in immuno-chemotherapy of colorectal cancer through multiple mechanisms not entirely related to direct antitumor effects of the agent.

Drug-mediated increase of susceptibility of human lung cancer to NK or LAK effector cells

Previous studies in murine models have shown that in vivo or in vitro treatment of tumor cells with mutagenic triazene compounds (TZC) lead to the appearance of novel drug-mediated tumor antigens (DMTA) capable of eliciting graft resistance in syngeneic hosts. This phenomenon, defined as 'chemical xenogenization' (CX), could be of potential value for immunochemotherapy of human neoplasias. It was also shown that TZC modulate NK sensitivity of murine tumor cells. Therefore, experiments were conducted to evaluate whether susceptibility of a human lung adenocarcinoma cell line (H125) to natural cytotoxic effectors could be affected by treatment with an in vitro active TZC. The results showed that drug treatment of H125 line leads to heritable increase of susceptibility to NK and LAK cells. Moreover, increased binding between effector and drug-treated target cells was observed. Additional studies on HLA antigens showed that changes in HLA-ABC molecule expression were probably not involved in TZC-induced increase of NK/LAK susceptibility. These results suggest that TZC treatment of a human tumor could result in increased expression of membrane structures recognized by natural cytotoxic effector cells. Further studies are required to explore whether these changes are generated by mutational events correlated with TZC-induced CX of human cancer cells.

Effect of human T lymphotropic retrovirus-I exposure on cultured human glioma cell lines

Four different human tumor cell lines of glial origin have been exposed to a human T lymphotropic retrovirus (HTLV-I). All these cell lines were positive for the glial marker glial fibrillary acidic protein (GFAP). The presence of virus RNA was demonstrated by in situ hybridization using an HTLV-I, SStI-SStI viral insert as probe. Virus expression has been monitored through an indirect immunofluorescence assay using a monoclonal antibody against virus core protein p19. All the four glioma cell lines tested became positive for p19 after 2 weeks of co-cultivation and showed a clear alteration of GFAP expression.

HTLV-I neurotropism. In vitro studies

The human T cell leukemia lymphoma virus (HTLV-I) has been recently associated to neurological disorders. In order to investigate the interaction between this virus and the central nervous system, cells of neuroectodermic origin have been exposed to HTLV-I through an experimental in vitro model. The results revealed the presence of HTLV-I virus core protein p19 inside glial cells, after a short time exposure to a chronically infected donor cell line. This suggests a possible role of a lymphotropic retrovirus in neurological diseases.

An immunopharmacological approach for prevention of retrovirus-associated disease in human pathology

Retroviruses of the HTLV and HIV subfamilies share a number of similar properties in terms of route of transmission and ultimate targeting to CD4+ T-cells, which results in leukaemic transformation in the case of HTLV and in depletion of CD4+ population and failure of T-helper function in HIV-infected individuals. Both diseases gain poor benefit from therapy at the stage of clinical diagnosis as ATL leukaemia or AIDS, respectively. Therefore the best chances to limit the worldwide distribution of these human retroviruses reside in an effective prevention of viral diffusion, possibly by vaccination, and of the onset of disease in virus-positive subjects. The possibility is discussed of defining protocols to prevent the development of clinical disease. These protocols could be based on pharmacological reconstitution of host's immune reactivity, that is altered early after infection with these retroviruses, and on the control of virus replication by antiviral therapy.

Mononuclear cells from peripheral blood of adult donors and from cord blood are equally protected by alpha- and beta-interferons against infection with HTLV-I

Human mononuclear cells derived from peripheral blood of adult donors (PBMC) or from neonatal cord blood (CBMC) were found to be equally sensitive to the protective effect of alpha- and beta-interferons (IFNs) against the infection with HTLV-I during long-term culture. The effect of IFNs was evidenced by a remarkable reduction of the number of virus-positive cells during culture as evaluated by indirect immunofluorescence for the p19 virus core protein. Moreover, the appearance of p19-positive immortalized clones was inhibited by IFNs in PBMC co-cultures, whereas it was delayed in CBMC cultures. These kinetics are in relation with the higher permissivity of CBMC to the virus in comparison with PBMC, since in CBMC cultures infected cells can be clearly detected starting already 1 week post-infection (p.i.), whereas in PBMC cultures their appearance time is approximately at the 6th week p.i. IFNs acted by 'priming' PBMC and CBMC to an active antiviral competence, since one single treatment with 1000 IU/ml of alpha- or beta-IFN at the onset of the co-culture of mononuclear cells with irradiated virus-donor cells was able to maintain very low levels of infection for approximately 6 weeks in CBMC cultures and at least for 18 weeks in PBMC cultures. As a consequence, it seems likely that IFN action is mediated by the expression of a defined, although not completely identified, set of genes in the host cells.

Effect of in vitro interferon treatment on the rapid clearance of murine leukemia cells in vivo

Previous work showed that interferon (IFN) can protect target cells from NK mediated lysis in vitro. In the present study we investigate the effect of IFN alpha/beta or IFN gamma treatment of three different murine leukemia cell lines. For this purpose FLC-745 (susceptible to the antiproliferative activity of IFN alpha/beta and gamma), FLC-3C18 (IFN alpha/beta -resistant and IFN gamma - susceptible) of DBA/2 origin and EL-4 (IFN alpha/beta - susceptible and IFN gamma - resistant) leukemia of C57B1/6 origin were treated with IFN alpha/beta or gamma in vitro and assayed for their susceptibility to natural resistance measured in vivo as organ rapid clearance 4 hr after iv injection into syngeneic mice. Using young or Poly I:C stimulated hosts, but not mice with low levels of natural resistance (i.e. older animals or mice treated with cyclophosphamide), slower elimination of treated cells was observed with: (a) FLC-745 cells treated with IFN alpha/beta and IFN gamma and (b) FLC 3C18 treated with IFN gamma. Such a delayed clearance was not observed with: (a) FLC-3C18 cells treated with IFN alpha/beta and (b) EL-4 leukemia cells preincubated with IFN alpha/beta or IFN gamma. These results suggest that under selected conditions IFNs can protect leukemic cells from in vivo natural reactivity.

N-methylformamide affects spontaneous metastases of 3LL lines and increases natural killer activity of tumor-bearing mice

The antitumor activity of the polar solvent N-methylformamide (NMF) was evaluated on three lines derived from the Lewis lung carcinoma (3LL), endowed with different metastatic potential. Two administration schedules were tested, these being repeated regimens of NMF (200 mg/kg per dose) for 12 consecutive days, starting 24 h or 6-10 days after tumor implantation (early or late treatment, respectively). The results of the present work can be summarized as follows: (1) NMF regimens did not greatly affect tumor growth behavior of 3LL lines; conversely, they markedly influenced their spontaneous colonizing ability in the lungs, either by delaying early metastatic spread or by reducing the number and size of pulmonary metastases already implanted. (2) A significant increase of NK cell activity during and after early treatment with NMF was observed in the more-metastasizing lines, thus suggesting the possibility of an immunomodulating effect of NMF.

Selection of HTLV-I positive clones is prevented by prostaglandin A in infected cord blood cultures

Type A prostaglandins (PGA1 and 16,16-dimethyl-PGA2-methyl ester) were found to block the proliferation of HTLV-I infected cord blood lymphocytes (CBL) in vitro, thus preventing the clonal immortalisation that is considered as a predisposing condition to HTLV-I positive leukaemia. PGA1 and di-M-PGA2 did not affect the long-term survival of normal non-infected CBL, whereas they suppressed the proliferation of an established cord-blood derived HTLV-I positive cell line, MT-2. As shown by the number of HTLV-I infected p19+ cells, the block of the selection of immortalised, infected clones by PGAs did not appear to be due to an inhibition of early stages of HTLV-I infection. The possibility that the effect of PGAs could be mediated by an action on the immune response was also examined. PGAs regulated the cell-mediated cytotoxic function of CBL to a different extent when normal non-infected or HTLV-I exposed CBL were compared. In fact, PGAs down-regulated the natural killing and macrophage/lymphocyte cytotoxic response of normal CBL, whereas they did not modify the already depressed immune response of CBL challenged with HTLV-I. These results suggest that the protective effect of PGAs against HTLV-I infection in vitro is mostly related to the direct suppression of the clonal expansion of virus-infected cells, rather than to the anti-viral activity or modulation of the cell-mediated immunity.

Modulation of the cell-mediated immune function by interferon alpha, beta or gamma can partially reverse the immunosuppression induced by human T-cell leukemia virus I in human cord blood cultures

Infection with human T-cell leukemia virus type I (HTLV-I) is associated in vitro and in vivo with a remarkable depression of cell-mediated immune functions. In the present report it is shown that early events following virus-induced suppression of the cell-mediated immune response of freshly isolated cord blood mononuclear cells (CBL) infected with HTLV-I can be partially counteracted by treatment with interferons alpha, beta or gamma (IFN). All three types of IFN exerted a protective effect on CBL cultures exposed to the virus. This resulted in: (a) a reduced number of virus-positive cells until 4 weeks of culture; (b) delay in the clonal expansion of infected cells (IFN alpha and gamma); (c) increased natural killer cell activity of CBL, 1 week post-infection (p.i.), mediated by IFN gamma; (d) increase of allospecific recognition of infecting and priming HTLV-I donor MT-2 cells by CBL in a cytotoxic-T-lymphocyte-like response, mediated by IFN and particularly by IFN gamma; (e) phenotype distribution of CBL subpopulations, tested 4 days p.i., more similar to that of non-infected CBL cultures. In contrast, the overall CBL proliferation, that is profoundly depressed during the first week p.i., was not restored by IFN treatments, suggesting that boosting of the cell-mediated killing induced by IFN might involve the maturation of undifferentiated precursor cells rather than stimulation of their proliferation. The improvement of the efficiency of the antiviral immune response induced by treatment with IFN is likely to contribute to the clearance of virus-positive cells during the early phase of infection. This would provide experimental evidence to support an immunopharmacological approach contributing to the conversion of HTLV-I carriers from positive to negative.

IL-2 reverses the inhibition of cytotoxic T-cell responses induced by 5-(3,3' dimethyl-1-triazeno)-imidazole-4-carboxamide (DTIC) in vitro

One of the major limitations in the use of triazene compounds for inducing increased immunogenicity of tumor cells in vivo (i.e. chemical xenogenization) is the profound immunodepressive activity of these drugs. The present study analysed the inhibitory effects of DTIC on various T-dependent immune responses in mice in an attempt to determine the mechanism of action and appropriate treatments for reverting the immune damage produced by the agent. Results obtained show that treatment with DTIC in vivo produced: (a) inhibition of spleen cell proliferation; (b) reduced IL-2 production in response to allogeneic stimuli; (c) reduction of the generation of IL-2R + CD8 + cells in allogeneic MLC; (d) inhibition of allo-CTL generation. The addition of IL-2 to MLC on day 2 of the co-culture restored full allogeneic CTL responses. These data suggest that exogenous IL-2 could be used to counteract DTIC-induced depression of T-cell reactivity, which is presumably involved in hosts' responses against autochthonous xenogenized tumor cells.

Natural resistance in mice against Friend cells injected intravenously. III. Comparison between in vivo and in vitro passaged interferon-sensitive (745) and interferon-resistant (3Cl8) cell clones

In vitro (FLC-Vt) or in vivo (FLC-V) passaged Friend erythroleukaemia cells of DBA/2 origin were tested for susceptibility to natural resistance (NR) in vivo or to NK cell activity in vitro. Scarcely oncogenic FLC-Vt cells were highly susceptible to in vivo NR (measured as rapid organ clearance or growth inhibition in lethally irradiated mice) or to in vitro NK attack. Conversely, highly oncogenic FLC-V cells were weakly susceptible to NR and to NK as well. These data seem to point out that natural immunity, which is up-regulated by endogenous or exogenous interferons, can play a significant role in surveillance against mouse leukaemic cells of retrovirus origin.