Biomedical subjects

M Sarzotti

Publications and source records attributed to M Sarzotti.

At least 19 recordsLinked to original sources

PubMed1997

Induction of cytotoxic T cell responses in newborn mice by DNA immunization.

Cytotoxic T cells (CTL) play a critical role in controlling viral infections. Infection of neonatal NFSIN mice with a high dose of Cas-Br-M murine leukemia virus, a neuropathogenic type C retrovirus, results in virus-induced neurologic disease and in their failure to generate a protective CTL response. Cas-Br-M-specific CTL are necessary in the protection of neonatal mice from Cas-Br-M-induced neurologic disease. Here we demonstrate that intramuscular inoculation of newborn mice with naked DNA expressing the full length Cas-Br-M genome induces a virus-specific CTL-mediated response. This CTL response is mediated by CD8+ T cells, is long lasting and, when transferred to susceptible neonatal recipients, protects them from Cas-induced neurologic disease. We also provide evidence that the intramuscular inoculation of neonates with plasmid DNA encoding only env sequences induces a dose-dependent CTL response in the absence of an anti-MuLV antibody response.

3T3 Cells↗

PubMed1997

Immunologic tolerance.

Understanding the phenomenon of immunologic tolerance and the mechanisms that control it at different stages of lymphocyte development is rapidly progressing. This review summarizes some recent findings in T-cell tolerance, focusing on neonatal and peripheral tolerance.

Animals↗

PubMed1996

Induction of protective CTL responses in newborn mice by a murine retrovirus.

The susceptibility of neonates to virus-induced disease is thought to reflect, in part, the immaturity of their immune systems. However, inoculation of newborn mice with low doses of Cas-Br-M murine leukemia virus induced a protective cytotoxic T lymphocyte (CTL) response. The inability of neonates to develop a CTL response to high doses of virus was not the result of immunological immaturity but correlated with the induction of a nonprotective type 2 cytokine response. Thus, the initial viral dose is critical in the development of protective immunity in newborns.

Animals↗

PubMed1996

Retrovirus-elicited interleukin-12 and tumour necrosis factor-alpha as inducers of interferon-gamma-mediated pathology in mouse AIDS.

Spleen cells from mice resistant or sensitive to mouse acquired immune deficiency syndrome (MAIDS) were examined for cytokine mRNA. In MAIDS-resistant BALB/c mice, cytokine transcripts peaked at 1 week after infection with Type 1 cytokines [interleukin-2 (IL-2), tumour necrosis factor-alpha (TNF-alpha), interferon-gamma (IFN-gamma), IL-12], dominating over Type 2 cytokines (IL-4, IL-10). Expression of cytokines other than IL-2 later declined to levels seen in uninfected mice. In MAIDS-sensitive B6 mice, transcripts for all cytokines were increased at 1 week and, except for IL-2, increased progressively. Spontaneous production of IFN-gamma protein was associated with enhanced mRNA expression at 1 week after infection of either strain, but none was detectable in association with even higher levels of transcripts at later times after infection of B6 mice. Spleen cells from longer-term-infected B6 mice, however, produced substantial amounts of IFN-gamma following treatment with lipopolysaccharide (LPS) or IL-12. Inclusion of anti-IL-12 or anti-TNF-alpha antibodies blocked induction of IFN-gamma by LPS. Induction of IFN-gamma by IL-12 was potentiated by TNF-alpha following stimulation of intact spleen cells and purified CD4+ or CD8+ T cells, as well as negatively selected CD4-8- cells from infected B6 mice. Further studies showed that IFN-gamma knockout mice on a B6 background developed MAIDS with a prolonged time-course, whereas BALB/c knockout mice were unchanged in their resistance to MAIDS. These studies suggest that continuing low-level expression of IFN-gamma, stimulated by IL-12 and TNF-alpha, contributes to the susceptibility of B6 mice to MAIDS but is not required for the resistance of BALB/c mice to disease.

Animals↗

PubMed1995

Immunogenic determinants of a neuropathogenic murine leukemia virus.

Previous studies of Cas-Br-M murine leukemia virus (MuLV) (Cas-MuLV) infection demonstrated that cytotoxic T cells (CTL) of the CD8+ phenotype play a role in resistance to the neuropathogenic effects of the virus in NFS/N mice. In the current study, we sought to identify the Cas-MuLV epitopes that are immunogenic for the CTL response. Infection of adult NFS/N mice with a well-characterized neuropathogenic variant of Friend MuLV, PVC-211 MuLV (PVC-MuLV), was not immunogenic for MuLV-specific CTL. Therefore, we constructed chimeric viruses between Cas-MuLV and PVC-MuLV. Infectious chimeras contained the Cas-MuLV env gene on a PVC-MuLV background (PVC-CasenvMuLV) and the PVC-MuLV env gene on a Cas-MuLV background (Cas-PVCenvMuLV). Cas-MuLV-specific CTL were found following inoculation of both the chimeric viruses and the parental Cas-MuLV but not the parental PVC-MuLV, despite evidence of antibody responses to both parental and chimeric MuLV. CTL generated in response to infection with PVC-CasenvMuLV and Cas-PVCenvMuLV were exclusively of the CD8+ phenotype. These results indicate that both the env and gag-pol regions of Cas-MuLV express epitopes that are immunogenic for CTL.

3T3 Cells↗

PubMed1995

Treatment of intracranial alphavirus infections in mice by a combination of specific antibodies and an interferon inducer.

Finding an effective treatment for viral infections that cause encephalitis remains an important problem. A model of human alphavirus infections, Semliki Forest virus, causes lethal encephalitis in weanling mice. Mice are viremic within 24 hr of an intraperitoneal challenge with the equivalent of three 75% lethal doses of Semliki Forest virus. Virus reaches the brain by 48 hr, and mortality results in all mice in 5-7 days. Introduction of virus intracranially accelerates the course of the infection. Neither anti-Semliki Forest virus hyperimmune serum nor the potent interferon inducer poly I:CLC given intraperitoneally are protective when used therapeutically after an intracranial virus infection, but a combination of 1,000 U hyperimmune serum and 80 micrograms/mouse of poly I:CLC results in a 50% survival rate. This combination treatment of intracranial Semliki Forest virus infection eliminates detectable viremia and reduces virus load in the brain over the course of the infection. These data show that when combined, specific antibody and an interferon inducer can interact synergistically to protect mice from alphavirus infections of the central nervous system even when given after the virus is replicating in the target organ.

Alphavirus Infections↗

PubMed1994

Ultraviolet-light-inactivated Cas-Br-M murine leukemia virus induces a protective CD8+ cytotoxic T lymphocyte response in newborn mice.

Newborn NFS/N mice are susceptible to the neurological disease induced by infection with Cas-Br-M murine leukemia virus (Cas), and do not develop a protective cytotoxic T cell (CTL)-mediated response to Cas infection. Here we demonstrate that whole UV light-inactivated Cas (UV-Cas), inoculated in newborn NFS/N mice, induced a strong, Cas-specific CTL response detectable 2 weeks postinoculation and persisting in vivo for > or = 36 weeks. The magnitude of the UV-Cas-induced splenic CTL response, mediated by CD8+ T cells, inversely correlated with the level of proviral cas env sequences detectable in the spleen of the UV-Cas-inoculated mice, as revealed by PCR amplification of tissue DNA. The transfer of UV-Cas-primed splenocytes, with Cas-specific CTL activity, protected 100% of recipient newborn mice from the development of neurological disease induced by infection with live Cas, for more than 28 weeks, and reduced the level of viral replication in the recipients.

Animals↗

PubMed1993

IFN-gamma production in response to neuropathogenic Cas-Br-M murine leukemia virus infection.

T cell-mediated production of IFN-gamma followed infection of adult, but not neonatal NFS/N mice with Cas-Br-M murine leukemia virus (Cas). The IFN-gamma response was associated with the appearance of CTL specific for Cas and with age-dependent resistance to neurologic disease. While both immune responses were mediated by a CD8-enriched population of T cells, IFN-gamma did not play a role in the activation of the Cas-specific CTL response. However, when given exogenously, IFN-gamma delayed the onset and reduced the incidence of Cas-induced neurologic disease. These data suggest that the IFN-gamma response to Cas infection may be an important host defense mechanism whose effects on virus replication and neurologic disease expression are independent of its effect on Cas-specific CTL.

3T3 Cells↗

PubMed1991

Cloning of murine splenic T lymphocytes and natural killer (NK) cells on filter paper discs: detection of a novel NK/T phenotype.

Discrete colonies of splenocytes were grown on filter paper discs in the presence of concanavalin A and interleukin 2. Phenotypic analysis of the colonies indicated that the majority expressed the Thy-1.2 marker and 72% of these co-expressed the CD3 molecule. Of the colonies 20%-25% were NK 1.1+ and they developed regardless of the presence of Con A in the culture medium, a property of the NK lineage. In addition, Thy-1.2+ colonies developed when splenocytes from scid mice, which lack mature T and B cells, were grown both in the presence and absence of concanavalin A. These results demonstrate that colonies of murine splenic T lymphocytes and NK cells could be successfully grown on filter paper discs and phenotypically characterized. With this colonies technique, it was possible to identify a novel subset of NK 1.1+ colonies that co-expresses CD3 and shares growth properties with T cell colonies.

Animals↗

PubMed1989

The in vivo antiviral effect of CL246,738 is mediated by the independent induction of interferon-alpha and interferon-beta.

An interferon (IFN) inducer and immunomodulator, CL246,738 [3,6-bis(2-piperidinoethoxy)acridine trihydrochloride], protected mice from lethal infection with Semliki Forest (SFV) and Banzi (BZV) viruses. A single oral dose of CL246,738 (5-150 mg/kg) administered 24 h before intraperitoneal challenge with SFV or BZV fully protected mice from lethal infection. Dose-dependent levels of circulating IFN peaked at 24 h in the serum and peritoneal fluid of CL246,738-treated mice. The circulating IFN of CL246,738-treated mice consisted of IFN-alpha and was produced by spleen cells. Peritoneal exudate cells (PEC) obtained from CL246,738-treated mice produced IFN-beta. Treatment in vivo with anti-IFN-alpha/beta and anti-IFN-beta reversed the protective effect of CL246,738 against lethal SFV encephalitis.

Acridines↗

PubMed1989

Postinfection therapy of arbovirus infections in mice.

Most antiviral agents are efficacious prophylactically in vivo, and a few are efficacious for postinfection (p.i.) therapy. To explore possibilities for p.i. therapy of encephalogenic Banzi virus (BZV) and Semliki Forest virus infections in mice, we evaluated candidate antiviral therapies after development of the first clinical signs of infection. The earliest clinical indication of BZV viremia in mice is a rise in core body temperature beginning on day 3 p.i. BZV-infected mice showing elevated core body temperatures (greater than or equal to 37.3 degrees C) on days 3 and 4 p.i. were treated intraperitoneally with the interferon inducer poly(ICLC) (80 micrograms per mouse) and/or specific antiserum. Combined therapy on day 3 of a BZV infection protected over 75% of mice showing clinical evidence of viral disease before treatment. Protection against early brain infection must occur on day 4 p.i., since by that day BZV has started multiplying in the brains of the mice. Significant protection occurred with antiserum alone and increased with poly(ICLC). Similar protection was obtained during Semliki Forest virus viremia, but this infection is so rapid that the first clinical signs are reliably detectable only after viremia.

Animals↗

PubMed1989

Long-term killing of natural killer-resistant target cells by interferon-alpha-, interferon-gamma-, and interleukin-2-activated natural killer cells.

The sensitivity of target cells to natural killer (NK) cell-mediated cytotoxicity was investigated. Five target cell lines were examined for susceptibility to killing by activated NK cells in a 4-hour cytotoxicity assay: one of them (K562) was highly sensitive, while the other four were resistant. However, the four NK-resistant target cell lines were fully susceptible to lysis when the assay was extended to 24 h. The cytotoxic cells that killed the NK-resistant target cells in a 24-hour assay were plastic- and nylon wool-nonadherent human peripheral blood mononuclear cells (PBMC) and their cytotoxicity was increased by interferon-alpha, interferon-gamma, and interleukin-2. Further, the cytotoxic activity of PBMC in the long-term assay was associated with large granular lymphocytes purified on a Percoll gradient, that killed the NK-sensitive cell line K562 in a 4-hour assay. All of the above are general criteria to qualify the cytotoxic cells as NK cells. Thus, the NK-resistant phenotype may not reflect absolute immunity to NK-mediated lysis, but it may reflect the different rates at which various target cell lines can be killed.

Cell Line↗

PubMed1989

Protection of mice from Semliki Forest virus infection by lymphocytes treated with low levels of interferon.

These studies provide the first evidence that adoptive transfer of syngeneic mouse (BALB/c) lymphocytes treated with low levels of mouse interferon (IFN)-alpha/beta can result in sufficient protection to protect mice from Semliki Forest virus (SFV) infection. Specifically, intraperitoneal inoculation of noncytotoxic lymphocytes treated exogenously with IFN (3 to 50 U/ml), washed exhaustively, and mixed with antibody to IFN-alpha/beta to neutralize any residual or early produced IFN, resulted (after repeated studies) in a 35% to 40% reduction in mortality of mice challenged with SFV (P less than or equal to .01), while inoculation of control lymphocytes had no effect. Direct administration of relatively high levels of IFN-alpha/beta (2,000 U/d) only moderately reduced the mortality (by 20%) in mice. Passive transfer of IFN-treated BALB/c mouse embryo cells also did not protect. The protection could not be attributed to carryover of IFN by the lymphocytes, endogenous IFN induction, enhanced cytotoxicity of endogenous splenocytes or peritoneal leukocytes, or early appearance of antiviral neutralizing antibody. Thus, the most likely cause of the observed protection is consistent with a unique mechanism that can be activated by the IFN-treated lymphocytes.

Animals↗

PubMed1987

EL-4 metastases in spleen and bone marrow suppress the NK activity generated in these organs.

The relationship between metastatic cells in the spleen and bone marrow of tumor-bearing mice and the NK activity generated in vitro by cells obtained from these organs was investigated. EL-4 lymphoma and B16 melanoma cells injected intraperitoneally into syngeneic mice (10(6) cells/animal) killed the recipients in 16 days. These tumors had a different metastatic profile: EL-4 metastasized to the spleen and bone marrow while B16 did not. The number of metastatic cells was evaluated by plating spleen or bone-marrow cells of tumor-bearing mice in agarose cultures; in parallel, the ability of spleen and bone-marrow cells to generate NK activity in vitro was assessed. The presence of 10(5) EL-4 cells/10(6) spleen or bone-marrow cells correlated with a total lack of NK activity in these organs; in contrast, no decrease in NK activity was evident in the spleen or bone marrow of B16-bearing mice. The removal of metastatic EL-4 cells (by antibody and complement) from the spleen or bone marrow did not rescue the NK activity. The lack of NK activity in spleen and bone marrow colonized by metastatic cells was not due to induction of a suppressor cell in the host. Metastatic EL-4 cells appeared to have a direct and irreversible suppressive effect on the generation of NK activity by spleen or bone marrow. A possible cause-effect relationship between metastatic colonization of lymphoid organs and suppression of local NK activity is considered.

Animals↗

PubMed1986

Interferon-mediated protection of B16 melanoma cells from cytotoxicity by activated macrophages.

Corynebacterium parvum-activated macrophages (M phi), purified by adherence, were cytotoxic for B16 melanoma cells maintained in vitro. Pretreatment of the melanoma cells for 18 hr with interferon-alpha/beta or -gamma (IFN-alpha/beta or -gamma) caused a reduced susceptibility of the B16 cells to M phi-mediated cytotoxicity. The IFN-induced protective effect of B16 cells from cytotoxic M phi was found to be dose dependent. In addition, IFN-gamma was more protective than IFN-alpha/beta. The protective effect observed with partially purified IFN was reproduced by using highly purified IFN-alpha/beta or recombinant IFN-gamma. Monoclonal antibodies to IFN-gamma neutralized the protective effect provided by IFN-gamma. These results show that the susceptibility of a tumor cell line to killing by activated M phi can be altered by IFN pretreatment.

Animals↗

PubMed1985

Characterization of cytotoxic cells generated from in vitro cultures of murine bone marrow cells.

Bone marrow cells cultured for 5-6 days generate cytotoxic activity against a number of natural killer (NK)-susceptible tumor cells. In this study, these bone marrow cytotoxic cells were compared to cells with NK activity obtained either from spleen cells activated in vitro with interferon (IFN-alpha/beta) or mitogen or from peritoneal exudate cells (PEC) obtained 4 days after bacillus Calmette-Guerin (BCG) infection. Splenic and PEC cytotoxic cells were shown to be Thy 1.2+, NK 1.1+, Asialo GM+1, Lyt 1.2-, Lyt 2.2-. In contrast, bone marrow cytotoxic cells were Thy 1.2+, NK 1.1-, Lyt 1.2-, Lyt 2.2- and expressed low levels of Asialo GM1 antigen (Asialo GM +/- 1). Precursor cells for bone marrow cytotoxic activity were shown to be Thy 1.2-, NK 1.1-, Lyt 1.2-, Lyt 2.2- but also expressed low levels of Asialo GM1 antigen (Asialo GM +/- 1). Cytotoxic activity for both bone marrow and spleen cells peaked in the low-density fractions of discontinuous Percoll density gradients. The cytotoxic activity of these bone marrow cells was augmented by pretreatment with IFN (-alpha/beta, -gamma) or soluble factors (IFN free) from activated EL-4 thymoma cells. Surprisingly, the ability of bone marrow cells to generate high levels of cytotoxic activity following in vitro culture appeared to be associated primarily with mice which were of the H-2b haplotype.

Animals↗

PubMed1983

Rous sarcoma virus-induced tumours in mice. II. Contribution of H-2 and non-H-2 alloantigen barriers to tumour immunogenicity in vivo.

The features of the immune recognition of a murine fibrosarcoma induced by Rous sarcoma virus were tested in histocompatible and histoincompatible mice. No evidence of a genetic regulation of spontaneous reactivity to tumour-associated antigens was found in various histocompatible F1 hybrids. Incompatibility in multiple minor histocompatibility antigens triggers a host reaction incapable of causing tumour rejection in some cases. The growth rate of incipient tumours is unaffected, whereas that of already visible tumour masses is significantly delayed. Admixture to the challenge of inactivated leukocytes bearing the same minor histocompatibility antigens as the tumour triggers a significantly stronger reaction. The reaction of hosts incompatible in the H-2K or H-2DL regions is quite efficient. However, the intensity of the immune reaction of H-2DLs antigens displayed by tumour cells is markedly dependent on the alleles of genes located in the central regions of the H-2 complex.

Animals↗

PubMed1983

Immune (gamma) interferon production by a murine T cell lymphoma: requirements for macromolecular synthesis and lack of relationship with cell cycle.

Macromolecular synthesis of immune interferon (IFN-gamma) by the L12-R4 T cell lymphoma, stimulated by phorbol myristic acetate, was studied by using reversible inhibitors of protein synthesis, puromycin and cycloheximide, and an irreversible inhibitor of RNA synthesis, actinomycin D. Reversible inhibition of protein synthesis during the first 3 h of stimulation had no effect on IFN-gamma production. The same treatment, performed 4 h after stimulation and maintained for an additional 5 h, decreased significantly the capability of L12-R4 cells to produce IFN-gamma. When the inhibitors of protein synthesis were left in the cultures, a complete block of IFN-gamma production was observed. Irreversible inhibitors of RNA synthesis at the beginning of stimulation did block IFN-gamma production by L12-R4 cells, but the same treatment was ineffective if performed 6 h after stimulation. These data suggest that continued protein synthesis is needed for IFN-gamma production, whereas the RNA seems to be completely synthesized within 4 to 6 h of stimulation. The relationship between IFN-gamma production and cell cycle phases was studied with the aid of a reversible drug, aphidicolin, that arrests cells at the G1/S border. Phorbol myristic acetate stimulation of L12-R4 cells after aphidicolin removal induced comparable levels of IFN-gamma at each different point of stimulation, indicating that IFN-gamma production by stimulated cells is not related to a particular phase but is continuously inducible during the cell cycle.

Animals↗