Positive effects of combined antiretroviral therapy on CD4+ T cell homeostasis and function in advanced HIV disease

Highly active antiretroviral therapy (HAART) increases CD4(+) cell numbers, but its ability to correct the human immunodeficiency virus (HIV)-induced immune deficiency remains unknown. A three-phase T cell reconstitution was demonstrated after HAART, with: (i) an early rise of memory CD4(+) cells, (ii) a reduction in T cell activation correlated to the decreasing retroviral activity together with an improved CD4(+) T cell reactivity to recall antigens, and (iii) a late rise of "naïve" CD4(+) lymphocytes while CD8(+) T cells declined, however, without complete normalization of these parameters. Thus, decreasing the HIV load can reverse HIV-driven activation and CD4(+) T cell defects in advanced HIV-infected patients.

Diversity of the cytotoxic melanoma-specific immune response: some CTL clones recognize autologous fresh tumor cells and not tumor cell lines

In the present work, to analyze the heterogeneity of the tumor-specific cytotoxic immune response, a large number of T cell clones were generated from the infiltrate of a tumor-proximal invaded lymph node, and two kinds of melanoma-specific CD8+ CTL clones were derived. The majority of T cell clones (about a hundred) are characterized by a specific lysis of the autologous tumor cell lines. Among 34 of the latter clones, HLA-A2 molecule and MART-1(27-35) peptide have been shown to play a predominant role in tumor recognition. However, no significant amplification at the tumor site was observed for 3 of these CTL. The other kind of tumor-specific CTL (1 oligoclonal and 2 clonal cell lines) did not lyse the autologous melanoma cell lines but lysed the "fresh" autologous tumor cells in a MHC class I-dependent manner. Functional analysis of the two different CTL clones have shown that they did not lyse NK targets, autologous peripheral monocytes, activated T cells, and transformed B cells or any of the few allogeneic cultured and uncultured melanoma cells we tested. TCR repertoire analysis has shown that one of these CTL clones was significantly detectable "in situ" among tumor-infiltrating lymphocytes, while not detectable among PBMC. Such melanoma-specific lymphocytes, which could not have been picked out through conventional screening procedures using tumor cell lines, could potentially play a role in tumor rejection. These results suggest that the immune response analyzed toward melanoma cell lines does not totally reflect the in situ immune status.

Diversity of the cytotoxic melanoma-specific immune response: some CTL clones recognize autologous fresh tumor cells and not tumor cell lines

In the present work, to analyze the heterogeneity of the tumor-specific cytotoxic immune response, a large number of T cell clones were generated from the infiltrate of a tumor-proximal invaded lymph node, and two kinds of melanoma-specific CD8+ CTL clones were derived. The majority of T cell clones (about a hundred) are characterized by a specific lysis of the autologous tumor cell lines. Among 34 of the latter clones, HLA-A2 molecule and MART-1(27-35) peptide have been shown to play a predominant role in tumor recognition. However, no significant amplification at the tumor site was observed for 3 of these CTL. The other kind of tumor-specific CTL (1 oligoclonal and 2 clonal cell lines) did not lyse the autologous melanoma cell lines but lysed the "fresh" autologous tumor cells in a MHC class I-dependent manner. Functional analysis of the two different CTL clones have shown that they did not lyse NK targets, autologous peripheral monocytes, activated T cells, and transformed B cells or any of the few allogeneic cultured and uncultured melanoma cells we tested. TCR repertoire analysis has shown that one of these CTL clones was significantly detectable "in situ" among tumor-infiltrating lymphocytes, while not detectable among PBMC. Such melanoma-specific lymphocytes, which could not have been picked out through conventional screening procedures using tumor cell lines, could potentially play a role in tumor rejection. These results suggest that the immune response analyzed toward melanoma cell lines does not totally reflect the in situ immune status.

T-cell receptor repertoire in neuroblastoma patients

Spontaneous regression of widespread lesions is a characteristic feature of neuroblastoma. One may postulate that the immune response contributes to these clinical regressions. Accordingly, we studied the T-cell receptor (TCR) repertoire of tumor-infiltrating lymphocytes in eight neuroblastoma tumors. The expression of 29 V alpha and 24 V beta gene segment subfamily specificities was analyzed by PCR and compared by computerized densitometry of Southern blots to values obtained in the blood. Overall, the TCR repertoire of these eight patients was diverse, with virtually all V alpha and V beta specificities expressed. Nonetheless, four of these patients showed V beta 2 gene segment subfamily overexpression in the tumor corresponding to local expansion of polyclonal T-cell subpopulations. In one patient, this expansion could be due to local secretion of superantigenic activity, as suggested by the specific stimulation of murine T cells expressing a human V beta 2 chain by supernatant of the corresponding neuroblastoma cell line. In addition, high-resolution analysis of the TCR beta transcript complementarity-determining region 3 sizes identified three patients (of six studied) with marked clonal T-cell expansion in the tumor not seen in the blood. The specific expression of several dominant clono-types in the tumor may be related to the recognition of neuroblastoma-specific antigens in these patients. Together, these results on the TCR repertoire expressed in vivo may lead to the characterization of putative immune response mechanisms (i.e., antigen- or superantigen-driven stimulation) which participate in tumor regression.

[Comparative analysis of the immune response in a case of primary regressive melanoma followed by gastric metastasis]

The theory of immunosurveillance against cancer has been an extensively debated question over the last decades. Multiple indirect arguments have supported the view that the immune system may control, at least in certain cases, malignant cell growth while direct demonstration is still lacking in the human. In an attempt to address this issue, we have selected a study model, namely spontaneously regressive melanoma. A primary cutaneous lesion was investigated. T cell repertoire analysis showed the in situ amplification of at least two tumor infiltrating lymphocyte (TILs) expressing the V beta 13 and V beta 16 variable TCR gene segments respectively. The two clones were precisely characterized by sequence of the TCR beta chain junctional region. Further functional study demonstrated that both lymphocytes displayed a selective cytotoxic activity against autologous tumor cells. The V beta 16+ cells, predominant in vivo, were shown to be closely opposed to the melanoma cells. Together, these studies demonstrated the existence of a local adaptative immune response associated to tumor regression, thus strongly supporting the validity of the immunosurveillance concept. A gastric metastasis which occurred three years after the primary lesion has been studied here. Overexpression of the V beta 13 and V beta 16 TCR segments was no longer detected by direct PCR analysis in situ. Sequencing transcripts from V beta 13+ and V beta 16+ TILs confirmed that the two CTLs, identified in the primary lesions, were not represented with high frequency. The V beta 13+ cell was however shown to be present while the V beta 16+ CTL was not detected. Yet, characterization of a tumor cell line derived from the gastric site indicated that the peptidic antigen(s) which induced the initially successfully immune response was still expressed. The present data illustrate that it has become possible to perform very precise analysis of local immune responses during cancer development. Such an improvement together with the recently initiated molecular characterization of tumor associated peptidic antigens, should provide the basis for improved strategies of cancer immunotherapy.

Direct evidence to support the immunosurveillance concept in a human regressive melanoma

The concept of immunosurveillance against cancer has been an extensively debated question over the last decades. Multiple indirect arguments have supported the view that the immune system may control, at least in certain cases, malignant cell growth while direct demonstration is still lacking in the human. In an attempt to address this issue, we have selected a study model, namely spontaneously regressive melanoma. In previous series of experiments, the variability of T cell receptors (TCRs) in the lymphocytes infiltrating a regressive tumor lesion was investigated. Results demonstrated that clonal T cell populations, precisely defined through their V-D-J junctional sequences, were amplified in situ. One clone was predominant, expressing the V beta 16 variable gene segment. A specific anti-V beta 16 TCR mAb was generated here to purify and functionally characterize the corresponding cells. A tumor-infiltrating lymphocyte-derived V beta 16+ T cell line was developed using this reagent. These in vitro cultured cells were found to express the in vivo predominant TCR sequence exclusively and to display an HLA-B14-restricted cytotoxic activity against the autologous tumor cells. Immunohistochemical experiments, performed with the anti-V beta 16 mAb, showed that the corresponding CTLs are present in the tumor area, some of them being closely opposed to the melanoma cells. Together, these studies demonstrate the existence of a local adaptive immune response clinically associated to tumor regression, thus strongly supporting the validity of the immunosurveillance concept in certain human tumors.

Evidence for in situ amplification of cytotoxic T-lymphocytes with antitumor activity in a human regressive melanoma

We have derived from lymphocytes infiltrating a human regressive melanoma lesion a series of T-cell receptor alpha/beta-dependent, HLA-B14-restricted cytotoxic T-lymphocyte clones reactive against the autologous tumor. Analysis of the T-cell receptor gene expression revealed that all the clones represented a unique cell expressing a V beta 13.1/J beta 1.1 gene segment. T-cell receptor transcripts expressed in the cloned cells were compared to those present in the uncultured tumor tissue. This analysis demonstrated that the specific cytotoxic T-lymphocyte clones characterized in vitro was actually selected and amplified in vivo at the lesion site. These results provide strong evidence that effector T-cells have contributed to tumor regression.

Simple method for quantifying alpha-tocopherol in low-density+very-low-density lipoproteins and in high-density lipoproteins

We assessed the distribution of alpha-tocopherol in serum lipoprotein samples after separating the lipoprotein fractions by either sequential ultracentrifugation or selective precipitation with sodium phosphotungstate-magnesium chloride reagent. alpha-Tocopherol concentrations were determined by reversed-phase high-performance liquid chromatography. After ultracentrifugation, we found that in men, low- and very-low-density serum lipoproteins (LDL-VLDL) contained 53.6% of alpha-tocopherol vs 46.4% in high-density lipoproteins (HDL). In women, serum LDL-VLDL contained 45.6% alpha-tocopherol after ultracentrifugation vs 54.4% in HDL. After selective precipitation, the proportions of alpha-tocopherol in men were 56.1% in LDL-VLDL vs 43.9% in HDL, and in women, 45.4% in LDL-VLDL vs 54.6% in HDL. After selective precipitation, alpha-tocopherol recovery from whole lipoprotein fractions was 97% to 100% vs 80% after ultracentrifugation, thus allowing more accurate alpha-tocopherol quantification than after separation by ultracentrifugation.