Characteristics and functions of Sendai virus-specific T-cell clones

Viral recombinant vaccines to the E6 and E7 antigens of HPV-16

Most cancerous lesions of the uterine cervix are linked to persistent infections with human papillomaviruses (HPV), most notably HPV-16 or -18. Vaccine-induced immune responses to the HPV early antigens E6 and E7, which contribute to cell transformation and are thus expressed in these cervical cancers, could potentially eradicate malignant cells. We generated recombinant vaccines based on E1-deleted adenovirus human strain 5 or on vaccinia virus strain Copenhagen expressing either the E6 or E7 oncoproteins of HPV-16. The different vaccines were compared in two experimental mouse tumor models employing Balb/c or C57Bl/6 mice. Data presented here demonstrate that depending on the model either CD4(+) or CD8(+) T cells provide protection to tumor cell challenge, resulting in striking differences in the efficacy of the four vaccines under investigation.

Immunization of cats against feline infectious peritonitis with anti-idiotypic antibodies

Anti-idiotypic antibodies (Ab2s) generated against neutralizing antibodies (Ab1s) specific for feline infectious peritonitis virus (FIPV) were shown to be specific for paratope-associated idiotopes of the Ab1s and not against isotypic determinants. In a study to determine the efficacy of an anti-idiotypic vaccine against feline infectious peritonitis (FIP), cats that were immunized with a pool of monoclonal Ab2s developed Ab3s that recognized the variable regions of the Ab2s as well as the natural antigen. In cats challenged with a lethal dose of virus the control group followed a predictable course of infection ultimately succumbing to FIP. Two immunized cats survived virus challenge and a third cat lived twice as long as the controls. The fourth immunized cat showed no evidence of protection. The ability to induce levels of protection against FIP lends support to the concept of using anti-idiotypic antibodies as a prophylactic vaccine.

IL-1, IL-2 and IFN-gamma production by Theiler's virus-induced encephalomyelitic SJL/J mice

Interleukins have been postulated to exert an important modulatory and recruiting role in the Theiler's murine encephalomyelitis virus (TMEV)-induced demyelination of the central nervous system (CNS) in SJL/J mice. Using bio- and radioimmunoassays, we have detected and quantified some of the interleukins suspected to play a role in this immune-mediated process. The interleukins 1 and 2 (IL-1, IL-2) and interferon-gamma (IFN-gamma) have been measured in homogenates from the CNS and sera from infected animals, as well as in supernatants from antigen-specific in vitro-stimulated spleen and meningeal cells. IL-1 was detected both in CNS tissue homogenates (approximately 20-40 fmol/ml) and in splenic cultures (200 U/ml). IL-2 was detected only after TMEV-specific antigenic stimulation in spleen cultures (approximately 120 U/ml). In vitro, IL-2 and IL-1 synthesis appear in a dose- and time-dependent manner. IFN-gamma could not be found in any case. The precise nature of IL-1 and IL-2 activity was further assessed by HPLC. The above results strongly indicate the presence of functionally active macrophages in the CNS infiltrates of cells triggering this autoaggressive immune process. In addition, we propose a central role for IL-1 in augmenting the intracerebral immune response leading to the inflammatory demyelination induced by TMEV.

Amelioration of established Sendai viral pneumonia in the nude mouse using a monoclonal antibody to the virus fusion protein

The pathological effect of parainfluenza type I (Sendai virus) is known to be a bronchopneumonia, which becomes a chronic pneumonia in the immunodeficient athymic (nude) mouse. The severity of this established chronic pneumonia can be dramatically altered by providing the nude mouse with humoral monoclonal antibodies which are neutralizing, and are directed against the fusion protein, of the virus. The alveolitis, which is a significant part of the pathology, is suppressed due to a reduction (greater than 90%) in the number of virus-infected alveolar macrophages present in the alveoli. This clearly identifies the infected alveolar macrophage as the primary effector cell in the pathogenesis of alveolitis caused by parainfluenza virus type I. The implications of using virus-neutralizing monoclonal antibodies, which have little immunomodulatory toxicity, in the treatment of viral pneumonias are discussed.

Cooperation between humoral factor(s) and Lyt-2+ T cells in effective clearance of Sendai virus from infected mouse lungs

The mechanism of cooperation between the L3T4+ and Lyt-2+ T cell subsets in effective clearance of Sendai virus from infected mouse lungs was studied by adoptive cell transfer using nude mice. Simultaneous transfer of a long-term-cultured Sendai virus-specific L3T4+ T cell line with L3T4+ cell-depleted immune spleen cell (L3T4-) fraction to infected nude mice could result in viral clearance, although single injection with either of these cells was not effective. Instead of the L3T4+ T cells, culture supernatants of the L3T4- T cell line or concanavalin A-stimulated mouse spleen cells and mouse serum immunized with the virus were also active in the cooperative viral clearance with L3T4- fraction. The role of the Sendai virus-sensitized L3T4- cell fraction in cooperative viral clearance with humoral factors could be replaced by neither T cell-deprived immune spleen cell fraction nor normal spleen cells. The 1,500 units of recombinant mouse interleukin 2 (IL-2), which was more than 12 times the IL-2 activity present in the supernatants of the T cell line or concanavalin A-stimulated spleen cells, failed to clear the virus in combination with the L3T4- fraction. Monoclonal antibodies to Sendai or mouse hepatitis viruses were also effective in the cooperative antiviral activity. IL-2 activity was not detected in these monoclonal antibodies and the mouse immune serum. Single injection of any humoral factors failed to clear the virus. These results indicate that Sendai virus-sensitized Lyt-2+ subset of T cells acts cooperatively with humoral factor(s) other than IL-2 or Sendai virus-specific antibody present in supernatants of the T cell line, of concanavalin A-stimulated spleen cells or hybridomas, and in mouse serum immunized with the virus.

Spontaneous production of interleukin-2 and interleukin-3 by spleen cells from mice infected with mouse hepatitis virus type 4

Spleen cells from mice, 4 to 60 days after infection with mouse hepatitis virus type 4, produced interleukin-2, as well as interleukin-3, in the absence of exogenous stimulants in vitro. This unique lymphokine production by mouse hepatitis virus type 4 infection was controlled by host genes.

Cell-mediated immunity induced in mice after vaccination with a protease activation mutant, TR-2, of Sendai virus

Our previous study has shown that, although a trypsin-resistant mutant of Sendai virus, TR-2, replicates only in a single cycle in mouse lung with a negligible lesion, the animal acquires a strong immunity against lethal infection with wild-type Sendai virus, suggesting that TR-2 could be used as a new type of live vaccine (M. Tashiro and M. Homma, J. Virol. 53:228-234, 1985). In the present study, we investigated the immunological response elicited in TR-2-infected mice, particularly with respect to cell-mediated immunity. Analyses of cytotoxic activities of spleen cells with 51Cr release assays revealed that Sendai virus-specific T lymphocytes (CTL), in addition to natural killer activity and antiviral antibodies, were induced in DBA/2 and C3H/He mice infected intranasally with TR-2. Proteolytic activation of the fusion glycoprotein F was required for the primary induction of CTL, though not necessarily for stimulation of natural killer and antibody responses. Memory of the CTL induced by TR-2 was long-lasting and was recalled in vivo immediately after challenge with wild-type Sendai virus. In contrast to TR-2, immunization with inactive split vaccine failed to induce the CTL response, but it elicited a high titer of serum antibody and a low level of natural killer activity.

T4+ T helper cell function in vivo: differential requirement for induction of antiviral cytotoxic T-cell and antibody responses

This study documents the differential requirements of T4+ T helper cells in the induction of virus-specific cytotoxic T-lymphocyte (CTL) and antibody responses during acute lymphocytic choriomeningitis virus infection. Two monoclonal antibodies (GK1.5 and RL172.4) directed against the L3T4 (T4) molecule were used for depleting T helper cells from mice. Depletion of T4+ cells caused a pronounced suppression of antiviral antibody response (20-fold decrease) but had minimal effect on virus-specific CTL response (less than 2-fold reduction). Despite the elimination of greater than 90% of T helper cells, anti-L3T4-treated mice were able to generate a CTL response of sufficient magnitude to control the viral infection. In contrast, depletion of Lyt2+ T cells abrogated the CTL response and the ability to eliminate virus. Thus, our results underscore the importance of the Lyt2+ T-cell subset in controlling infection with this virus and show that a deficiency of T4+ T cells is likely to have a more severe effect on antibody production than on CTL responses.

T cells subsets responsible for clearance of Sendai virus from infected mouse lungs

T cell subsets responsible for clearance of Sendai virus from mouse lungs determined by adoptive transfer of immune spleen cell fractions to infected nude mice. T cells with antiviral activity developed in spleens by 7 days after intranasal infection. Spleen cell fractions depleted of Lyt-2+, Lyt-1+, or L3T4+ cells showed antiviral activity in vivo, although the degree of the activity was lower than that of control whole spleen cells. The antiviral activity of the Lyt-2+ cell-depleted fraction was consistently higher than that of L3T4+ (Lyt-1+)-depleted cells. In vitro cytotoxic activity against Sendai virus-associated, syngeneic lipopolysaccharide-blast cells was detected in stimulated cells from intraperitoneally immunized mice but was lost after depletion of Lyt-2+ cells. Multiple injection of anti-Sendai virus antibody into infected nude mice had no effect on lung virus titer. These results indicate that L3T4+ (Lyt-1+) and Lyt-2+ subsets are cooperatively responsible for efficient clearance of Sendai virus from the mouse lung.

Lymphokines induce specificity degradation in virus-induced cytolytic T-cell clones

The target cell specificity of antiviral cytolytic T-lymphocyte (CTL) clones is influenced by in vitro tissue culture conditions. We have demonstrated that high concentrations of lymphokines such as recombinant interleukin-2 (rIL-2) induce killer T cells to lose virus specificity. Our experiments do not indicate that the cells become like natural killer (NK) cells. The loss of specificity is more general and can be reversed upon culture in more physiological concentrations of lymphokines. The implications of these observations for the pathogenesis of viral infection is discussed.

Murine and human T11 (CD2) cDNA sequences suggest a common signal transduction mechanism

The murine equivalent of the cDNA encoding the human T11 (CD2) sheep erythrocyte-binding protein has been cloned. It codes for a putative transmembrane protein which is homologous to human T11. In contrast to immunoglobulins whose domains consist of anti-parallel beta sheets, we predict that mouse and human T11 external domains probably belong to the alpha/beta protein folding class. The cytoplasmic region of T11 is a lengthy, proline-rich segment; secondary structural analysis predicts it to have a nonglobular conformation. This elongated tail could allow for interaction with multiple other intracellular proteins and may contain a cation-binding site involved in T lineage activation.

A phosphorylated, disulfide-linked membrane protein in murine cytotoxic T lymphocytes

The previously determined sequence of the murine T-cell gamma gene and its transcription in cloned T lymphocytes suggests that the polypeptide encoded by this gene is generally present in cytotoxic T cells as a 33-kDa monomer in a disulfide-bonded dimer. The gamma chain is also expected to be phosphorylated because a sequence in its cytoplasmic domain is homologous to an active site for serine phosphorylation in the regulatory subunit of cAMP-dependent protein kinase. We describe here a cytotoxic-T-cell-associated phosphorylated protein, many of whose properties suggest that it may be the product of the T-cell gamma gene. Its phosphorylation is greatly enhanced by interleukin 2 stimulation.

Characterization of gP85gag as an antigen recognized by Moloney leukemia virus-specific cytolytic T cell clones that function in vivo

The gag membrane protein gP85gag, encoded by Moloney murine leukemia virus (M-MLV), was identified as a target molecule recognized by Moloney murine sarcoma virus--M-MLV (M-MSV--M-MLV)-specific cytolytic T lymphocyte (CTL) clones. Target cells infected with Ab-X-MLV, an M-MLV-derived mutant virus not encoding gP85gag, were not lysed by the CTL clones. The same CTL clones were shown previously to induce the destruction of M-MLV-induced tumor cells in the peritoneal cavity. We have now characterized CTL-resistant antigen-loss tumor cell variants that have lost the surface antigen, but which retain transcriptionally silent M-MLV genomes. A cloned antigen-loss variant that reverted in vitro to the CTL-susceptible phenotype reexpressed M-MLV genomes that had undergone an insertion event in the region of the viral DNA coding for the gag membrane protein. Intravenous injection of virus-specific CTL clones inhibited tumor formation in mice injected subcutaneously with M-MSV--M-MLV.