CD34+ cord blood cell-transplanted Rag2-/- gamma(c)-/- mice as a model for Epstein-Barr virus infection.

Recent studies suggest that Epstein-Barr virus (EBV) can infect naïve B cells, driving them to differentiate into resting memory B cells via the germinal center reaction. This hypothesis has been inferred from parallels with the biology of normal B cells but has never been proven experimentally. Rag2(-/-) gamma(c)(-/-) mice that were transplanted with human CD34(+) cord blood cells as newborns were recently shown to develop human B, T, and dendritic cells, constituting lymphoid organs in situ. Here we used this model to better define the strategy of EBV infection of human B cells in vivo and to compare this model system with different conditions of EBV infection in humans. Our results support the model of EBV persistence in vivo in cases that were characterized by follicular hyperplasia and a relatively normal CD4(+) and CD8(+) T-cell distribution. Intriguingly, in cases that were characterized by nodular and diffuse proliferation with a preponderance of CD8(+) T cells, similar to infectious mononucleosis, EBV still infects naïve B cells but also induces clonal expansion and ongoing somatic mutations without germinal center reactions. Our results reveal different strategies of EBV infection in B cells that possibly result from variations in the host immune response. Future experiments might allow understanding of the mechanisms responsible for persistent EBV infection and provide targets for more highly tailored therapeutic interventions.

Kaposi's sarcoma-associated herpesvirus/human herpesvirus 8 infection in reactive lymphoid tissues: a model for KSHV/HHV-8-related lymphomas?

We set out to analyze the presence of Kaposi's sarcoma-associated herpesvirus (KSHV)/human herpesvirus 8 (HHV-8) in different neoplasms occurring in East Africa, a region characterized by a high KSHV/HHV-8 seroprevalence rate and endemic Kaposi's sarcoma (KS). Our results suggest that, in endemic regions of Africa, KSHV/HHV-8 is predominantly associated with KS, independently of HIV status. During the course of this study, other important information came to light. We found the presence of KSHV/HHV-8 in 2 cases of lymph nodes partially involved by Burkitt's lymphoma and KS and in 1 case of multicentric Castleman disease. Our immunophenotypic and molecular data seem to suggest 2 different mechanisms of viral infection are at work in lymphoid cells. On one hand, when B cells show a latent phase infection with KSHV/HHV-8, after the germinal center reaction, naive B cells become resting memory B cells, similarly to Epstein-Barr virus-infected B cells. On the other hand, when lytic genes such as vIL6 are expressed in naive B cells, they may be driven to differentiate into plasmablasts without undergoing germinal center reaction. Interestingly, among KSHV/HHV-8-positive cases, in those in which there was also lymphoma, the neoplastic cells were negative for KSHV/HHV-8. This further confirms that KSHV/HHV-8 is involved in the neoplastic transformation of only certain types of lymphoma, probably in relation to their precursor infected cell. In conclusion, the maturation stage of KSHV/HHV-8-positive B cells as well as the type of viral infection may well determine the morphological, phenotypic, and clinical characteristics of KSHV/HHV-8-associated lymphomas.

Telomere length in neoplastic and nonneoplastic tissues of patients with familial and sporadic papillary thyroid cancer.

INTRODUCTION: Many studies have found an association between altered telomere length (TL), both attrition or elongation, and cancer phenotype. Recently, we have reported that patients with the familial form of papillary thyroid cancer (FPTC) have short telomeres in blood leucocytes. AIM: To evaluate relative TL (RTL) at somatic level in neoplastic and nonneoplastic tissues of patients with FPTC (n = 30) and sporadic PTC (n = 46). METHODS: RTL was measured by quantitative PCR in neoplastic thyroid tissues, in the corresponding nontumor thyroid tissues (normal contralateral thyroid), and in other extrathyroidal tissues (lymph nodes, muscles, or buccal mucosa). RTL was also measured in adenomas and hyperplastic nodules. In a subset of samples, telomerase expression was measured by quantitative PCR. RESULTS: Mean ± SD RTL of FPTC patients was short in neoplastic thyroid tissues (0.87 ± 0.2) with no difference from the normal contralateral thyroid tissues (0.85 ± 0.11) and extrathyroidal tissues (0.85 ± 0.31). On the contrary, in patients with sporadic PTC, the mean ± SD RTL in the neoplastic tissues (1.73 ± 0.63) was significantly shorter than that found in normal contralateral tissues (2.58 ± 0.89) and extrathyroidal tissues (2.5 ± 0.86). For all tissue samples (cancer, normal thyroid, and nonthyroidal tissues) the mean ± SD RTL of familial cases was shorter (P < 0.0001) than that found in tissues from sporadic PTC. RTL of FPTC was also lower (P < 0.0001) than that of 23 follicular adenomas (1.6 ± 0.7) and 24 hyperplastic nodules (2.2 ± 0.9). CONCLUSIONS: Our results demonstrate that short telomeres are a consistent feature of PTC, which in familial cases, is not restricted to the tumor tissue. This finding suggests that FPTC has a distinct, heritable, genetic background.

Immunoglobulin gene analysis reveals 2 distinct cells of origin for EBV-positive and EBV-negative Burkitt lymphomas.

The normal counterpart of the neoplastic B cells in Burkitt lymphoma (BL) is still unclear. Based on immunoglobulin gene rearrangement studies, some authors suggest an origin from germinal center cells and others from memory B cells. However, most of these studies rely on cell lines or on a small series of cases. To help clarify the cell of origin of BL, semi-nested polymerase chain reaction (PCR) was performed to amplify the VDJ rearrangements of the immunoglobulin heavy chain (V(H)) genes, and the resultant amplificates were sequenced for comparison with known germline V(H) segments. The results of this approach revealed that all cases (15 endemic BL [eBL], 10 sporadic BL [sBL], and 6 AIDS-related BL) harbor mutated V(H) genes, with different mutation ranges among the 3 types of BL. The eBL and AIDS-related forms showed considerably higher mutation rates than the sBL form (5.1%, 5.4%, and 1.5%, respectively). The mutations in eBL and AIDS-related BL also showed signs of antigen selection, whereas no signs of antigen selection were found in sBL. Finally, after subcloning the amplificates, sequence analysis revealed no signs of ongoing mutations in any of the cases analyzed. Given that one of the main differences between eBL and AIDS-related BL on the one hand and sBL on the other hand is the association with Epstein-Barr virus (EBV), we compared EBV-positive and EBV-negative BLs independently of their geographic origin and HIV status. The differences in the number of somatic mutations and antigen selection were even more evident when this approach was used. According to our molecular results, it appears that EBV-positive and EBV-negative BL may originate from 2 distinct subsets of B cells, pointing to a particular role for the germinal-center reaction in the pathogenesis of these tumors. The different types of C-MYC translocation reported in BL may also be related to the different stages of B-cell maturation.

Benign lymphoepithelial lesion associated with squamous cell carcinoma of the skin: an immunohistochemical and molecular genetic study.

BACKGROUND: Benign lymphoepithelial lesions (BLEL) are usually found in salivary glands in autoimmune disorders. Some LEL are recognized to already be, or may progress to become, lymphomas. Skin lesions similar to LEL have been described in lymphomas, and are caused by neoplastic lymphocytes which infiltrate adnexal structures. To date, BLEL have not widely been recognized in the skin. METHODS: We describe skin lesions similar to BLELs, at the periphery of squamous cell carcinomas (SCC) in 8 healthy patients, in one of whom the lesion recurred. Immunocharacterization of both epithelial and lymphocytic components and molecular genetic investigation was performed. Polymerase chain reaction (PCR) analysis was done to detect IgH chain gene, and T-cell receptor beta and gamma gene rearrangements. Association with Epstein-Barr virus (EBV) was also tested by in situ hybridization (ISH) for EBV-encoded RNAs (EBERs). RESULTS: Epithelial cells showed the immunophenotype of eccrine sweat gland ducts. Infiltrating lymphocytes expressed overwhelming B antigens and CD5. Neither clonal B and/or T proliferations nor EBERs signals were demonstrable. CONCLUSIONS: We observed skin lesions similar to BLELs, showing modifications of sweat gland duct and CD5+, B lymphocytic expansion. In our cases there were no associated autoimmune disorders; the local immunoresponse to SCC might have caused BLEL.