Age related changes in T cell mediated immune response and effector memory to Respiratory Syncytial Virus (RSV) in healthy subjects.

Respiratory syncytial virus (RSV) is the major pathogen causing respiratory disease in young infants and it is an important cause of serious illness in the elderly since the infection provides limited immune protection against reinfection. In order to explain this phenomenon, we investigated whether healthy adults of different age (20-40; 41-60 and > 60 years), have differences in central and effector memory, RSV-specific CD8+ T cell memory immune response and regulatory T cell expression status. In the peripheral blood of these donors, we were unable to detect any age related difference in term of central (CD45RA-CCR7+) and effector (CD45RA-CCR7-) memory T cell frequency. On the contrary, we found a significant increase in immunosuppressive regulatory (CD4+25+FoxP3+) T cells (Treg) in the elderly. An immunocytofluorimetric RSV pentamer analysis performed on these donors' peripheral blood mononuclear cells (PBMCs), in vitro sensitized against RSV antigen, revealed a marked decline in long-lasting RSV specific CD8+ memory T cell precursors expressing interleukin 7 receptor α (IL-7Rα), in the elderly. This effect was paralleled by a progressive switch from a Th1 (IFN-γ and TNF-α) to a Th2 (IL-10) functional phenotype. On the contrary, an increase in Treg was observed with aging. The finding of Treg over-expression status, a prominent Th2 response and an inefficient RSV-specific effector memory CD8+ T cell expansion in older donors could explain the poor protection against RSV reinfection and the increased risk to develop an RSV-related severe illness in this population. Our finding also lays the basis for new therapeutic perspectives that could limit or prevent severe RSV infection in elderly.

Anti-angiogenetic effects of immune-reconstituted influenza virosomes assembled with parathyroid hormone-related protein derived peptide vaccine.

BACKGROUND: C-IRIV/PTR-4 is a novel anticancer vaccine construct composed of immune-reconstituted influenza virosomes (IRIV) assembled with the PTH-rP derived peptide (PTR)-4, a synthetic CTL epitope with HLA-A(*)02.01 amino acid binding motifs. This peptide is able to generate a human PTH-rP specific CTL response with anti-tumor activity in vitro and in mice. MATERIALS AND METHODS: We have investigated the immunological and preventive anti-tumor activity of C-IRIV/PTR-4 compared with the soluble PTR-4 peptide, in HHD mice inoculated with autologous PTH-rP+ tumor cells. RESULTS: Peptide vaccination with either a soluble and an IRIV formulation showed similar immunological activity and the ability to purge the tumor tissue of tumor cell clones able to produce the target antigen (PTR-rP). The most efficient protection from tumor growth was however observed in animals vaccinated with C-IRIV/PTR-4 in which an additional IRIV related anti-angiogenetic effect was detected in the tumor tissue. CONCLUSIONS: These results confirm the immunological activity of PTR-4 vaccination and suggest a more efficacious therapeutic potential of C-IRIV/PTR-4 against bone metastases and malignancies like breast, prostate and lung which very often over-express PTH-rP.

Immunological characterization of respiratory syncytial virus N protein epitopes recognized by human cytotoxic T lymphocytes.

Virus-specific cytotoxic T lymphocytes (CTLs) are crucial for the control of respiratory syncytial virus (RSV) infection. This study has identified CTL epitopes of the RSV N protein in healthy subjects. We screened the primary structure of the N protein for HLA-A 0201-binding amino acid consensus motifs, identifying three peptides designated as N-RSV1, N-RSV2, and N-RSV3. These peptides were used to generate CTL lines by stimulating human HLA-A 02.01 peripheral blood mononuclear cells (PBMCs) in vitro. These CTL lines were then characterized by performing CTL chromium release assays and IFN-gamma secretion detection by intracellular cytokine staining. N-RSV1 and N-RSV3 peptides elicited the strongest cytolytic activity against RSV-infected cells and they could be useful epitopes for the analysis of CTL responses to RSV and for understanding immune-induced disease pathogenesis.

Immunization with Toscana virus N-Gc proteins protects mice against virus challenge.

Toscana virus (TOSV) is an emerging virus, circulating in the Mediterranean area, that is responsible for aseptic meningitis, meningoencephalitis, and encephalitis. The development of a vaccine that could provide complete protection from TOSV infection is needed. In this study we investigated the capacity of TOSV structural proteins, nucleocapsid protein N and the two Gc and Gn glycoproteins, produced as recombinant proteins, in an animal model. In particular, we investigated their role in inducing specific and protective immune responses against virus infection. Mice were immunized intraperitoneally using TOSV antigens singly or in combination. The results show that only the N-Gc combination was able to protect 100% of animals from a lethal challenge with a neurovirulent strain of TOSV. This potential vaccine induces high serum antibody titres with neutralizing activity and it is safe for animals. Moreover, immunization induces a virus specific cell-mediated immune response, in particular a CD8+ T cell response associated with a marked expression of interferon gamma. These results indicate that the N+Gc viral antigen combination could be useful for future development of a vaccine controlling the spread of this emerging virus that could pose a new threat for humans.

Chemotherapeutic drugs may be used to enhance the killing efficacy of human tumor antigen peptide-specific CTLs.

The effects of anticancer chemotherapy on antigen-specific cytotoxic T lymphocytes (CTLs) are mostly unknown. We tested the effects of cytotoxic drugs such as 5-fluorouracil, gemcitabine, and oxaliplatin on the functional activity of antigen-specific CTL cultures derived from the peripheral blood mononuclear cells of human donors. We found that a biweekly drug-exposure of human HLA-A(*)02.01+ CTLs derived from bulk cultures led to completely different effects if occurring early (day second) or late (day thirteenth) after the in vitro stimulations with the cognate peptides. In the first case, there was a significant CTL inhibition, whereas in the second, there was a marked enhancement of the antigen-specific cytolytic activity. Results of immunocytofluorimetric studies and CTL/natural killer inhibition assays suggested that the latter effect could be related to a more selective drug-mediated inhibition of cohabitant T regulatory (reg) cells. These results were translated in an in vivo therapeutic mouse model where humanized HLA-A(*)02.01 transgenic mice inoculated with EL-4/humanized HLA-A(*)02.01 transgenic mice showed a prolonged survival and the greatest rate of cure when receiving a combined treatment with a thymidylate synthase-specific peptide vaccine and a multidrug chemotherapy regimen administered late after immunization. Tumor samples derived from this group of mice showed a reduced expression of the target thymidylate synthase antigen, a marked reduction of T(reg)s, and a noteworthy infiltration of C8+ T cells. These results may have clinical implications for the design of new translational anticancer regimens aimed at combining chemotherapy and immunotherapy.

Development of a mouse model for the study of Toscana virus pathogenesis.

Toscana virus (TOSV) has recently been recognized as an emerging virus transmitted by phlebotomus vectors, responsible for acute neurological diseases in Mediterranean countries. In our study, we demonstrated that adult Balb/c mice were susceptible to TOSV when infected intracerebrally (i.c.) or subcutaneously (s.c.) with a neuroadapted strain of the virus. We have shown that by performing serial passages of a wild type human isolate of TOSV in mouse brains, selection occurs for a highly virulent variant which replicates efficiently in the central nervous system (CNS) of i.c.-injected mice, causing acute encephalitis and death. Immunohistochemical analysis and TUNEL assay of post-mortem organs showed that TOSV replication was highly restricted to neurons in which it induced apoptotic death; however, virus antigen-positivity was also observed in the spleen and lymph nodes. In s.c.-injected mice, virus was detectable in the spleen and lymph nodes, whereas only few meningeal cells and neurons were affected, allowing for the mouse survival the infection. The presence of TOSV in spleen and lymph node cells in both s.c.- and i.c.-treated mice suggests their possible involvement in the diffusion of the infection. This animal model may be helpful for the development of prophylactic measures against TOSV infections.

5-fluorouracil-based chemotherapy enhances the antitumor activity of a thymidylate synthase-directed polyepitopic peptide vaccine.

BACKGROUND: Thymidylate synthase (TS), a key enzyme in DNA synthesis, is often overexpressed in cancer cells. Some chemotherapeutic agents, such as 5-fluorouracil (5-FU), act by inhibiting TS expression. We evaluated whether a novel 28-amino acid multiepitope peptide, TS/PP, that contains the sequences of three TS-derived epitopes with binding motifs for HLA-A(*)02.01 could induce a TS-directed cytotoxic T-lymphocyte (CTL) response with antitumor activity. METHODS: TS/PP peptide immunologic activity in CTL lines derived from human leukocyte antigen (HLA)-A(*)02.01+ peripheral blood mononuclear cells (PBMCs) was tested in the presence of interleukin-2 and autologous TS/PP peptide-loaded dendritic cells. Immunologic and antitumor activities of TS/PP and its toxicity were also evaluated in vivo in HLA-A(*)02.01 transgenic (HHD) mice that were vaccinated with TS/PP, control, or TS-peptide cocktail and treated with or without 5-FU chemotherapy. The mice were also inoculated subcutaneously with TS-expressing EL-4/HHD lymphoma cells to assess immune response against these tumor cells. RESULTS: TS/PP-specific CTL lines showed a TS-multiepitopic specificity and were able to kill TS+/HLA-A(*)02.01+ breast and colon carcinoma cells. The killing ability against target cells previously exposed to sublethal doses of 5-FU was statistically significantly greater than against untreated target cells (43.5% versus 26.5% at 25/1 effector to target ratio [Difference {diff} = 17.0]; 95% confidence interval [CI] = 12.6 to 20.4) for MDA-MB-231 breast carcinoma cells and 73.5 versus 48.5 (diff = 25.0; 95% CI = 16.2 to 33.8) for the SW-1463 colon carcinoma cells. HHD mice vaccinated with TS/PP manifested a TS-peptide-specific CTL response with no sign of autoimmunity or toxicity. Furthermore, treatment of these mice with 5-FU delayed or prevented the occurrence of tumors formed by inoculation with autologous (TS+)EL-4/HHD lymphoma cells. CONCLUSIONS: The multiepitopic TS/PP vaccine induces a tumor-specific immune response in mice and is especially potent when used in combination with 5-FU-based chemotherapy.

Immune-reconstituted influenza virosome containing CD40L gene enhances the immunological and protective activity of a carcinoembryonic antigen anticancer vaccine.

The correct interaction of a costimulatory molecule such as CD40L with its contrareceptor CD40 expressed on the membrane of professional APCs, provides transmembrane signaling that leads to APC activation. This process can be exploited to significantly improve the efficacy of cancer vaccines and the outcome of a possible cancer vaccine-induced, Ag-specific CTL response. Therefore, we investigated whether a novel intranasal delivery of immune-reconstituted influenza virosomes (IRIV), assembled with the CD40L gene (CD40L/IRIV), could be used to improve protective immunity and the Ag-specific CTL response against carcinoembryonic Ag (CEA) generated with a novel vaccine constituted of IRIV assembled with the CEA gene (CEA/IRIV). Our results suggest that CD40L/IRIV was able to augment CEA-specific CTL activity and CEA-specific protective immunity induced by CEA/IRIV most likely through the induction of a CTL response associated with a Th1 phenotype. In conclusion, we provide evidence that CD40L/IRIV, by acting through the CD40L/CD40 signaling pathway, acts as an immune-adjuvant that could increase the efficacy of a CEA-specific cancer vaccine, which could provide an efficacious new strategy for cancer therapy.

Efficient delivery of DNA to dendritic cells mediated by influenza virosomes.

In an attempt to enhance the immunological efficacy of DNA-based vaccines, we have investigated a new biological means for delivering target gene DNA directly to professional antigen presenting cells (APC), such as the dendritic cells (DC), which are ultimately responsible for the antigen presentation and the primary activation of the immune system. For this purpose we investigated influenza virosomes (IRIV) with assembled DNA as a possible biological carrier for targeting the APC in vivo and in vitro. By cytofluorimetric analysis of the draining lymph nodes of Balb/c mice which had received (by intranasal (in.) administration) FITC-labeled DNA assembled with IRIV, we detected a significant labeled DNA uptake in a subset of lymph node deriving cells expressing DC surface markers. Subsequent mRNA analysis of these lymph nodes showed that the trans-gene delivered by the virosomes was effectively expressed as mRNA. Finally, a further cytofluorimetric analysis performed on human DC-enriched-PMBC, infected in vitro with labeled DNA/IRIV lead to the conclusion that the majority of APC (DC, B lymphocytes and CD16+ cells) are able to incorporate the labeled DNA transported by the construct. These findings suggest that the virosome is an efficient delivery system for testing infectious, as well as anti-cancer, DNA-based vaccine research.