The molecular and antigenic properties of a Sabin-like type 2 poliovirus, isolated from the stool samples of a 2-year-old agammaglobulinaemic child who developed paralysis 1 year after receiving the third dose of oral poliovirus vaccine, were analysed. The virus revealed 0?88 % genome variation in the VP1 region compared with the standard reference strain, compatible with replication of the virus in the intestine over approximately 1 year. The typical mutations in the 59NCR and VP1 associated with reversion to neurovirulence for Sabin type 2 poliovirus were found. Despite this, the virus was characterized by both PCR and ELISA tests as Sabin-like and showed temperature sensitivity and neurovirulence in transgenic mice typical of the Sabin type 2 vaccine strain. Gammaglobulin replacement therapy led rapidly to virus clearance, which, when combined with treatment with the antiviral drug pleconaril, stopped virus excretion; no further virus shedding occurred. This is the first case of poliomyelitis and long-term excretion from an immunodeficient patient to be reported in Italy through the active 'Acute Flaccid Paralysis' surveillance system.

No abstract

We report here that HLA-DRbeta4*01 restricted MAGE-A3(161-175 )specific CD4(+) T cells from a healthy donor recognize a naturally processed epitope formed through the exogenous but not the endogenous pathway. However, the intensity of recognition of the native epitope by MAGE-A3(161-175 )specific CD4(+) T cells strongly depends on the antigen presenting cells and the amount of protein available for processing. EBV-transformed lymphoblastoid cells (LCLs) and melanoma cells engineered to express MAGE-A3 in the endosomal/lysosomal compartment were strongly recognized while autologous dendritic cells loaded with lysate from MAGE-A3 expressing cells were, although significantly, poorly recognized. To prove that the amount of antigen available for processing was a key factor determining the different response LCLs were sorted by MAGE-A3 expression. The response intensity correlated with the amount of MAGE-A3 expressed by the cells. Collectively, these results suggest that different antigen presenting cells with different amount of antigen available for processing as well as protease activity are important factors in determining the epitope repertoire produced in vivo, and therefore reliable tools should be used when testing recognition of native epitopes by peptide specific CD4(+) T cells.

Little is known about the repertoire of MAGE-A3 CD4 + T-cell epitopes recognized in vivo by neoplastic patients and how antigen processing influences epitope formation. Here, we first show that MAGE-A3-specific CD4 + T cells are present in the blood of advanced melanoma patients. MAGE-A3 111-125 , , and MAGE-A3 281-300 were recognized by 7, 6, and 5 of the 11 patients tested, respectively. MAGE-A3 146-160 and MAGE-A3 171-185 were also recognized in two and one cases, whereas no recognition of MAGE-A3 161-175 and MAGE-A3 243-258 was observed. Cytokines produced were mainly interleukin 5 and/or granulocyte macrophage colony-stimulating factor, suggesting impairment of productive polarized Th1 responses. Secondly, proteases inhibitors were used to modulate in vitro the recognition by CD4 + T-cells clones of dendritic cells loaded with MAGE-A3-expressing cell lysates. We found that formation of MAGE-A3 111-125 depended on both leupeptin-sensitive and pepstatin-sensitive proteases. In contrast, we found that MAGE-A3 161-175 , which was never recognized ex vivo, was formed by leupeptin but destroyed by pepstatin-sensitive proteases. Collectively, our results show that (a) anti-MAGE-A3 CD4 + T-cell immunity develops in vivo in neoplastic patients and is focused toward immunodominant epitopes, (b) the response in advanced disease is skewed toward a Th2 type, and (c) endosomal/lysosomal proteases in dendritic cells influence the repertoire of the epitopes recognized. [Cancer Res 2008; 68(5):1555-62]