Recombinant MVA-prime elicits neutralizing antibody responses by inducing antigen-specific B cells in the germinal center.

The RV144 HIV-1 vaccine trial has been the only clinical trial to date that has shown any degree of efficacy and associated with the presence of vaccine-elicited HIV-1 envelope-specific binding antibody and CD4+ T-cell responses. This trial also showed that a vector-prime protein boost combined vaccine strategy was better than when used alone. Here we have studied three different priming vectors-plasmid DNA, recombinant MVA, and recombinant VSV, all encoding clade C transmitted/founder Env 1086 C gp140, for priming three groups of six non-human primates each, followed by a protein boost with adjuvanted 1086 C gp120 protein. Our data showed that MVA-priming favors the development of higher antibody binding titers and neutralizing activity compared with other vectors. Analyses of the draining lymph nodes revealed that MVA-prime induced increased germinal center reactivity characterized by higher frequencies of germinal center (PNA <sup>hi</sup> ) B cells, higher frequencies of antigen-specific B-cell responses as well as an increased frequency of the highly differentiated (ICOS <sup>hi</sup> CD150 <sup>lo</sup> ) Tfh-cell subset

A prospective study demonstrates an association between JC virus-specific cytotoxic T lymphocytes and the early control of progressive multifocal leukoencephalopathy.

Progressive multifocal leukoencephalopathy (PML) is a fatal demyelinating disease of the CNS of immunosuppressed individuals caused by the polyomavirus JC (JCV). In previous studies, we showed that JCV-specific cytotoxic T lymphocytes (JCV-specific CTL) were associated with a favourable outcome in patients with PML. However, these CTL had been assessed in PML survivors more than 1 year after the onset of disease and we could not determine whether this immune response was only a surrogate marker for a general recovery of the patient's immune system or a causal factor in the patient's neurological improvement. In this study, we assessed the relationship between JCV-specific CTL detected early in the course of PML and the subsequent course of disease activity. We enrolled 26 patients with possible or proven PML, including 21 HIV+ patients, less than 10 months after the onset of their neurological symptoms (3.7 +/- 2.5 months, median +/- interquartile range). JCV-specific CTL were detected by either 51Cr release or tetramer staining assay. Patients were then followed prospectively and the clinical course of PML was determined. At the time of their first immune evaluation, we found that 15 patients had detectable JCV-specific CTL. HIV+ patients with JCV-specific CTL had a higher CD4+ T-cell count (215 +/- 103/microl) and a lower HIV viral load (144 +/- 431 copies/ml) than those without JCV-specific CTL (32 +/- 59/microl, P = 0.004 and 43 100 +/- 54 778 copies/ml, P = 0.01). Thirteen of these 15 patients with JCV-specific CTL developed clinically quiescent PML, while only two out of 11 without detectable CTL controlled their neurological disease. Therefore, the early detection of JCV-specific CTL had an 87% predictive value for subsequent control of PML, while the absence of such CTL had an 82% predictive value for subsequent active PML (P = 0.0009). Fifteen patients were evaluated less than 4 months after the onset of PML (1.9 +/- 1.3 months). Of nine patients with JCV-specific CTL, seven (78%) demonstrated subsequent control of disease, whereas six out of six (100%) without JCV-specific CTL developed progressive PML (P = 0.007). Two to ten CTL assays were performed on PBMC of 11 patients. Of these patients, one had an increase in JCV-specific CTL preceding a significant clinical improvement. In another patient with otherwise stable immune parameters, a decline in JCV-specific CTL preceded an exacerbation of PML. We conclude that JCV-specific CTL can be detected early in PML and can predict control of this disease. Fluctuations of JCV-specific CTL in the blood are associated with variation in disease manifestations. These results indicate that JCV-specific CTL are associated with the control of PML

Association of prolonged survival in HLA-A2+ progressive multifocal leukoencephalopathy patients with a CTL response specific for a commonly recognized JC virus epitope.

The role of JC virus (JCV)-specific CTL was explored in the immunopathogenesis of progressive multifocal leukoencephalopathy (PML). We identified a 9-aa epitope of the JCV capsid protein VP1, the VP1(p100) peptide ILMWEAVTL, which is recognized by CTL of HLA-A2+ HIV+/PML survivors. We then constructed an HLA-A*0201/VP1(p100) tetrameric complex that allowed us to assess by flow cytometry the PBMC of 13 PML patients and 11 control subjects for the presence of JCV-specific CTL. VP1(p100)-specific CTL were detected by tetramer binding in VP1(p100)-stimulated PBMC of five of seven (71%) PML survivors and zero of six PML progressors (p = 0.02). Two of three HIV+ patients with a leukoencephalopathy resembling PML, but with no virologic evidence of JCV infection, also had detectable VP1(p100)-specific CTL in their PBMC. PBMC of eight HIV+ patients with other neurologic diseases and healthy control subjects had no detectable JCV-specific CTL. These data suggest that the JCV-specific cellular immune response may be important in the containment of PML, and the tetramer-staining assay may provide a useful prognostic tool in the clinical management of these patients

JC virus induces a vigorous CD8+ cytotoxic T cell response in multiple sclerosis patients.

We sought to compare the ongoing CD8+ cytotoxic T lymphocytes (CTL) immune response of MS patients to self and viral antigens. Using 51Cr release and tetramer staining assays, we found that the CTL response against VP1, the major capsid protein of the polyomavirus JC (JCV), was significantly higher than the one against epitopes of MBP and PLP. The JCV-specific CTL response was also significantly stronger in MS patients than healthy control subjects. These findings may shed a new light on the recent events related to the development of progressive multifocal leukoencephalopathy in three natalizumab-treated patients

JCV-specific cellular immune response correlates with a favorable clinical outcome in HIV-infected individuals with progressive multifocal leukoencephalopathy.

Most immunosuppressed individuals who develop progressive multifocal leukoencephalopathy (PML) have a rapid fatal outcome, whereas some become long-term survivors. We explored the impact of the cellular immune response against JC virus (JCV) on the clinical outcome of 7 HIV+ and 3 HIV- individuals with PML. Of the 4 HIV+/PML survivors, all had detectable cytotoxic T lymphocytes (CTL) specific for JCV T or VP 1 proteins compared to none of the 3 HIV+/PML progressors tested. Of the 3 HIV-/PML patients, 1 was recently diagnosed with PML and showed evidence of neurologic improvement without any treatment. This patient had CTL specific for the VP1 protein of JCV. The other 2 HIV-/PML survivors were stable 3-8 years after the diagnosis of PML. They did not have any detectable CTL against JCV. These findings suggest that JCV-specific immune response is associated with favorable outcome in HIV+ individuals with PML. The lack of detectable JCV-specific CTL in 2 HIV-/PML survivors might indicate a burnt-out disease without sufficient antigenic stimulation to maintain the cellular immune response. The detection of JCV-specific CTL in an HIV- patient recently diagnosed with PML, who was showing evidence of neurological improvement without any treatment, indicates that this finding may be used as a favorable prognostic marker of disease evolution in the clinical management of patients with PML. As the quest for an effective treatment of PML continues, JCV-specific cellular immune response deserves further attention because it appears to play a crucial role in the prevention of disease progression