Hepatitis C virus (HCV) and lymphomagenesis

Detailed analysis of the E2-IgM complex in hepatitis C-related type II mixed cryoglobulinaemia

Hepatitis C virus (HCV) plays a major role in the induction of type II mixed cryoglobulinaemia (MCII). The role of HCV proteins and virus-host interaction in the pathogenesis of MC remains to be defined. To address this issue, we have characterized, in detail, the monoclonal IgM and the viral component of circulating immune complexes in eight patients with HCV-associated MCII. The proportion of HCV-RNA compartmentalized in the cryoprecipitate (CP) varied greatly (10-80% of total HCV-RNA). The complementary determining region (CDR)3 sequences of monoclonal immunoglobulin M (IgM) VH and VK genes were highly homologous to rheumatoid factor and to antibodies against HCV-E2. Furthermore, the CDR3 sequences in some of our MCII patients were highly similar to those described in HCV-positive patients with non-Hodgkin's lymphoma (NHL). From these results, it appears that, as in the case of NHL, the IgM-rheumatoid factor (RF) production in MCII patients is antigen driven, namely by E2. However, the limited number of mutations in VH and VK genes with respect to the germline and their distribution showed that the B-cell response in these cases was prevented from undergoing affinity maturation. Furthermore, in patients with monoclonal IgM and definite compartmentalization of HCV in either CP or supernatant, a highly homogeneous E2-hypervariable region (HVR)1 sequence distribution was found (90-100% identical clones), a feature of the quasispecies frequently associated with an impaired humoral immune response to HCV. These findings suggest that in patients with HCV-associated MCII, maturation of monoclonal B lymphocytes may be blocked in a primitive stage preventing serious damaging effects because of the auto-reactivity of their secreted immunoglobulins.

Clinicopathologic and genetic profile of intracranial marginal zone lymphoma: a primary low-grade CNS lymphoma that mimics meningioma

PURPOSE

Although rare overall, marginal zone B-cell lymphoma (MZBCL) is the most common primary low-grade CNS lymphoma reported in the literature. The aim of this study is to elucidate the biology and genetic features of this unusual tumor.

PATIENTS AND METHODS

Fifteen CNS MZBCLs were studied clinically, pathologically, and genetically, including fluorescent in situ hybridization analyses with commercially available MALT1 and IgH break-apart and centromere 3, 7, 12, and 18 probes.

RESULTS

CNS MZBCLs preferentially affect middle-aged women (female-to-male ratio, 4:1), with 93% presenting as dural-based masses mimicking meningioma. Ten patients with 1 to 7.6 years of follow-up after diagnosis showed no evidence of disease after radiation and/or chemotherapy. Like MZBCLs outside of the CNS, they consisted of CD20+, CD3- small B lymphocytes with varying degrees of plasmacytic differentiation and predominantly kappa light-chain restriction (78%). Lymphoid follicles with follicular colonization were seen in three patients and deposition of amyloid was noted in samples from two patients, one of which was tumefactive. Neither Bcl-6 protein nor Epstein-Barr virus-encoded RNA was expressed. Trisomy 3 was detected in six of 12 patients, with no rearrangements of MALT1 or IgH and no trisomies of 7, 12, or 18 detected.

CONCLUSION

Our data suggest that intracranial MZBCL is an indolent primary CNS lymphoma that typically presents as a meningioma-like dural-based mass. Trisomy 3, but not MALT1 or IgH translocation, is a common genetic abnormality that may contribute to the pathogenesis of this CNS lymphoma.

Hepatic B-cell non-Hodgkin's lymphoma of MALT type in the liver explant of a patient with chronic hepatitis C infection

B-cell non-Hodgkin's lymphoma (B-NHL) is a well-documented complication of hepatitis C virus (HCV) infection. Marginal zone (mucosa-associated lymphoid tissue; MALT) lymphomas constitute a less common type of B-NHL. In this article, we report a case of liver MALT in a cirrhotic patient, incidentally discovered after liver transplantation (LT). We discuss pertinent diagnostic and management strategies in this clinical setting.

Distinct roles of enhancer nuclear factor 1 (NF1) sites in plasmacytoma and osteopetrosis induction by Akv1-99 murine leukemia virus

Murine leukemia viruses (MLVs) can be lymphomagenic and bone pathogenic. In this work, the possible roles of two distinct proviral enhancer nuclear factor 1 (NF1) binding sites in osteopetrosis and tumor induction by B-lymphomagenic Akv1-99 MLV were investigated. Akv1-99 and mutants either with NF1 site 1, NF1 site 2 or both sites disrupted induced tumors (plasma cell proliferations by histopathology) with remarkably similar incidence and mean latency in inbred NMRI mice. Clonal immunoglobulin gene rearrangement detection, by Southern analysis, confirmed approximately half of the tumors induced by each virus to be plasmacytomas while the remaining lacked detectable clonally rearranged Ig genes and were considered polyclonal; a demonstration that enhancer NF1 sites are dispensable for plasmacytoma induction by Akv1-99. In contrast, X-ray analysis revealed significant differences in osteopetrosis induction by the four viruses strongly indicating that NF1 site 2 is critical for viral bone pathogenicity, whereas NF1 site 1 is neutral or moderately inhibitory. In conclusion, enhancer NF1 sites are major determinants of osteopetrosis induction by Akv1-99 without significant influence on viral oncogenicity.

Diminished expression of CD19 in B-cell lymphomas

BACKGROUND

CD19 is expressed on most B-cell lymphomas; however, the frequency and types of B-cell lymphomas with low-level expression of CD19 are not well characterized.

METHODS

We reviewed flow cytometric histograms specifically for decreased CD19 expression on 349 cases analyzed by the Flow Cytometry Laboratory at University Hospitals of Cleveland (Cleveland, Ohio). Results of flow cytometry were correlated with the morphologic diagnosis.

RESULTS

Of the cases reviewed, 125 (36%) showed a visible decrease in CD19 expression compared with normal B lymphocytes. Decreased CD19 expression was noted in 79% of follicular lymphomas (27 of 34), 36% of small lymphocytic lymphomas/chronic lymphocytic leukemias (82 of 228), 31% of mantle cell lymphomas (4 of 13), 24% of diffuse large B-cell lymphomas (8 of 33), and 13% of marginal zone B-cell lymphomas/lymphoplasmacytoid lymphomas (4 of 30) and was not observed in any Burkitt lymphoma (0 of 5) or hairy cell leukemia (0 of 6). Decreased CD19 expression was significantly more frequent in follicular lymphomas than in other lymphoma subtypes (P < 0.001). No significant difference was observed in the frequency of decreased CD19 expression based on histologic grade of follicular lymphoma.

CONCLUSIONS

Diminished expression of CD19 expression occurs frequently in B-cell lymphomas, in particular follicular lymphoma, and may be helpful in identifying B-cell lymphoma cells in complex cell mixtures such as bone marrow specimens.

Kinetics of HCV envelope proteins' interaction with CD81 large extracellular loop

We used BIAcore to analyze the kinetics of interactions between CD81 and hepatitis C virus (HCV) envelope proteins. We immobilized different forms of HCV envelope proteins (E1E2, E2, and E2(661)) on the sensor and monitored their interaction with injected fusion proteins of CD81 large extracellular loop (CD81LEL) and glutathione-S-transferase (CD81LEL-GST) or maltose binding protein (CD81LEL-MBP). The difference between the GST and MBP fusion proteins was their multimeric and monomeric forms, respectively. The association rate constants between CD81LEL-GST or CD81LEL-MBP and the E1E2, E2 or E2(661) HCV envelope proteins were similar. However, the dissociation rate constants of CD81LEL-MBP were higher than those of CD81LEL-GST. Interestingly, the dissociation rate constant of CD81LEL-GST from E1E2 was much lower than from E2 or E2(661). The interaction between both forms of the CD81LEL fusion proteins and the HCV envelope proteins best-fitted the "heterogeneous ligand" model. This model implies that two kinds of interactions occur between envelope proteins and CD81LEL: one is strong, the other is weak. It also implies that the heterogeneity is likely due to the HCV envelope proteins, which are known to form non-covalently linked heterodimers and disulfide-linked aggregate.

The tetraspanin web modulates immune-signalling complexes

The tetraspanin web represents a new concept of molecular interactions in the immune system. Whereas most surface immune-modulating molecules involve receptor-ligand interactions, tetraspanins associate with partner proteins and facilitate their lateral positioning in the membrane. Moreover, the same tetraspanin molecule can associate with different proteins depending on the cell type. Most importantly, members of this family tend to associate with each other, together with their partners, in membrane microdomains that provide a scaffold for the transmission of external stimuli to intracellular-signalling components.

Evolution of B-cell clonal expansions with age

B-cell clonal expansions (BCE) in young mice are transient, detectable for less than 4 weeks. In contrast, BCE in old mice persist more than 2 months. The greater persistence of BCE in old mice does not appear to be due to the age of the host as the survival of phenyloxazolone chicken serum albumin-induced BCE in most old mice was shorter than in young mice. This raises the possibility that persistent BCE seen in old mice develop over time from transient BCE present earlier in life. To test this hypothesis, young C57BL/6 mice were immunized with hen egg lysozyme (HEL) during the first year of life. By 28 months of age, the majority of these mice had developed a benign, persistent BCE associated with a HEL-specific serum mIg. We also investigated whether benign, persistent BCE, present in 18-month-old mice, can evolve into B-cell lymphomas. We observed that four of eight C57BL/6 mice that survived to 29 months of age had developed diffuse large cell lymphomas. In three of these mice, this diagnosis was made by microscopic analysis of the lymphoid organs. In one mouse, a macroscopic lymphoma was present that permitted us to demonstrate that the IgH mRNA CDR3 length and sequence in the malignant lymphoma was derived from a persistent BCE present 11 months earlier. Together these observations are consistent with the hypothesis that stepwise accumulation of genetic alterations combined with Darwinian selection underlies the evolution of B cells from transient BCE in young mice into persistent BCE, serum mIg, and B-cell lymphomas observed in older mice.

Clinicopathologic Features of Waldenström's Macroglobulinemia and Marginal Zone Lymphoma: Are They Distinct or the Same Entity?

Waldenstrom's macroglobulinemia (WM) is considered in the World Health Organization classification as a clinical syndrome associated with monoclonal immunoglobulin (Ig) M secretion, mainly observed in patients with lymphoplasmacytic lymphoma (LPL) and occasionally with other small B-cell lymphomas. Some authors consider it a rare distinct lymphoproliferative disorder with primary bone marrow infiltration and IgM monoclonal gammopathy. As LPL shares important morphologic and immunophenotypic overlaps with marginal zone B-cell lymphomas (MZLs) in cases showing plasmacytic maturation, it remains unclear if they constitute unique or distinct entities. Both diseases are composed of lymphocytes, lymphoplasmacytoid cells, and tumoral plasma cells with a surface (s) IgM-positive sIgD+/ cytoplasmic IgMpositive CD19+ CD20+ CD27+/ CD5 CD10 CD23 phenotype, without a specific marker. Extranodal mucosa-associated lymphoid tissue (MALT) lymphoma, nodal MZL (NMZL), and splenic MZL (SMZL) are distinct entities displaying common morphologic, immunophenotypic, and genetic characteristics. MALT lymphoma is clearly distinct from LPL, although bone marrow infiltration and IgM paraprotein are not rare. Splenic MZL and NMZL are incompletely characterized, but a plasmacytoid/plasmacytic differentiation, autoimmune manifestations, and monoclonal component are frequent in both diseases. Bone marrow involvement is constant in SMZL and present in 60% of NMZLs. Molecular IgVH gene analysis has confirmed this heterogeneity, particularly within SMZL, with mutated and unmutated cases. Further studies are needed to clarify the pathogenesis of these MZLs and their relationship with LPL.

Non-Hodgkin's lymphoma and other nonhepatic malignancies in Swedish patients with hepatitis C virus infection

The aim of this study was to evaluate the association between hepatitis C virus (HCV) infection and non-Hodgkin's lymphoma (NHL), multiple myeloma (MM), thyroid cancer (TC), chronic lymphatic leukemia (CLL), acute lymphatic leukemia (ALL), and Hodgkin's lymphoma (HL). A Swedish cohort of 27,150 HCV-infected persons notified during 1990-2000 was included in the study. The database was linked to other national registers to calculate the observation time, expressed as person-years, and to identify all incident malignancies in the cohort. The patients were stratified according to assumed time of previous HCV infection. The relative risk of malignancy was expressed as a standardized incidence ratio (SIR)-the observed number compared to the expected number. During 1990-2000 there were 50 NHL, 15 MM, 14 ALL, 8 TC, 6 CLL, and 4 HL diagnoses in the cohort. Altogether, 20 NHL, 7 MM, 5 TC, 4 CLL, 1 ALL, and 1 HL patient fulfilled the criteria to be included in the statistical analysis. The observation time was 122,272 person-years. The risk of NHL and MM was significantly increased in the stratum with more than 15 years of infection (SIR 1.89 [95% CI, 1.10-3.03] and 2.54 [95% CI, 1.11-5.69], respectively). The association was not significant in TC or CLL. In conclusion, we report the incidence of several malignancies in a nationwide cohort of HCV-infected persons. Although the delayed diagnosis of HCV probably has resulted in an underestimation of the risk, this study showed a significantly increased risk of NHL and MM.

Evidence for selective transformation of autoreactive immature plasma cells in mice deficient in Fasl

Germline mutations in Fas and Fasl induce nonmalignant T cell hyperplasia and systemic autoimmunity and also greatly increase the risk of B cell neoplasms. B lymphomas occurring in Fasl mutant (gld) mice usually are immunoglobulin (Ig) isotype switched, secrete Ig, and are plasmacytoid in appearance but lack Myc translocations characteristic of other plasma cell (PC) neoplasms. Here, we explore the relationship between B cell autoreactivity and transformation and use gene expression profiling to further classify gld plasmacytoid lymphomas (PLs) and to identify genes of potential importance in transformation. We found that the majority of PLs derive from antigen-experienced autoreactive B cells producing antinuclear antibody or rheumatoid factor and exhibit the skewed Ig V gene repertoire and Ig gene rearrangement patterns associated with these specificities. Gene expression profiling revealed that both primary and transplanted PLs share a transcriptional profile that places them at an early stage in PC differentiation and distinguishes them from other B cell neoplasms. In addition, genes were identified whose altered expression might be relevant in lymphomagenesis. Our findings provide a strong case for targeted transformation of autoreactive B cells in gld mice and establish a valuable model for understanding the relationship between systemic autoimmunity and B cell neoplasia.

Effect of hepatitis C virus infection on the risk of non-Hodgkin's lymphoma: a meta-analysis of epidemiological studies

Although a high prevalence of hepatitis C virus (HCV) infection among non-Hodgkin's lymphoma (NHL) patients had been reported, subsequent epidemiological studies conducted to examine a causal association between HCV and NHL have provided inconsistent results across studies. A strikingly positive association has been reported primarily from Italy and Japan, while no association was found in other regions of the world. To clarify the association between HCV and NHL, we conducted a systematic literature review. Eligible study designs were nested case-control studies, population-based case-control studies, and hospital-based case-control studies using non-cancer subjects as controls. The studies published through January 1991 to August 2003 were searched through Medline. Ultimately, 23 studies with 4049 NHL patients and 1,813,480 controls were identified. Summary statistics were crude odds ratios (ORs) comparing the anti-HCV seropositive and seronegative subjects. As we identified heterogeneity between studies, summary statistics were calculated based on a random-effect model. We did not find any evidence of publication bias. The major sources of variation were the use of blood donor controls and year of publication. The summary OR for NHL was 5.70 (95% confidence interval (CI), 4.09-7.96, P < 0.001). The subgroup analysis by phenotype showed a similar trend for B-cell (5.04, 95% CI: 3.59-7.06) and T-NHL (2.51, 95% CI: 1.39-4.56). In conclusion, we found a strongly positive association between anti-HCV seropositive test subjects and risk of NHL. Further biological studies examining this association are warranted.

CD81-dependent binding of hepatitis C virus E1E2 heterodimers

Hepatitis C virus (HCV) is the leading cause of chronic liver disease worldwide. HCV is also the major cause of mixed cryoglobulinemia, a B-lymphocyte proliferative disorder. Direct experimentation with native viral proteins is not feasible. Truncated versions of recombinant E2 envelope proteins, used as surrogates for viral particles, were shown to bind specifically to human CD81. However, truncated E2 may not fully mimic the surface of HCV virions because the virus encodes two envelope glycoproteins that associate with each other as E1E2 heterodimers. Here we show that E1E2 complexes efficiently bind to CD81 whereas truncated E2 is a weak binder, suggesting that truncated E2 is probably not the best tool with which to study cellular interactions. To gain better insight into virus-cell interactions, we developed a method by which to isolate E1E2 complexes that are properly folded. We demonstrate that purified E1E2 heterodimers bind to cells in a CD81-dependent manner. Furthermore, engagement of B cells by purified E1E2 heterodimers results in their aggregation and in protein tyrosine phosphorylation, a hallmark of B-cell activation. These studies provide a possible clue to the etiology of HCV-associated B-cell lymphoproliferative diseases. They also delineate a method by which to isolate biologically functional E1E2 complexes for the study of virus-host cell interaction in other cell types.