The pathogenesis of AIDS lymphomas: a foundation for addressing the challenges of therapy and prevention

Update on the Pathogenesis, Diagnosis, and Therapy of AIDS-related Lymphoma

AIDS-related non-Hodgkin's lymphoma (ARL) is an opportunistic malignancy that foreshortens life more than any other commonly occurring HIV-associated cancer. Treatment strategies include low-dose chemotherapy, chemotherapy given with antiretroviral therapy, and infusional chemotherapy regimens. Rituximab, an anti-CD20 monoclonal antibody, has been found to be useful in non-HIV-associated lymphomas and is of interest in ARL as well. Since the advent of highly active antiretroviral therapy, the ARL incidence and survival has changed. This paper reviews the epidemiologic, biologic, and clinical features of ARL with the aim of presenting a cohesive overview of these elements.

Aberrant and Unstable Expression of Immunoglobulin Genes in Persons Infected With Human Immunodeficiency Virus

We examined the IgM VH gene subgroup use-distribution in serial blood samples of 37 human immunodeficiency virus (HIV)-infected patients and a group of HIV-seronegative healthy adults. The IgM VH gene repertoires of healthy adults were relatively similar to one another and were stable over time. In contrast, individuals infected with HIV had IgM VH gene repertoires that were significantly more heterogeneous and unstable. Persons at early stages of HIV infection generally had abnormal expression levels of Ig VH3 genes and frequently displayed marked fluctuations in the relative expression levels of this VHgene subgroup over time. In contrast, persons with established acquired immunodeficiency syndrome (AIDS) had a significantly lower incidence of abnormalities in Ig VH3 expression levels, although continued to display abnormalities and instability in the expression levels of the smaller Ig VH gene subgroups. Moreover, the skewing and/or fluctuations in the expressed-IgM VHgene repertoire appeared greatest for persons at earlier stages of HIV infection. These studies show that persons infected with HIV have aberrant and unstable expression of immunoglobulin genes suggestive of a high degree humoral immune dysregulation and ongoing humoral immune responses to HIV-associated antigens and superantigens.

© 1998 by The American Society of Hematology.

Aberrant and Unstable Expression of Immunoglobulin Genes in Persons Infected With Human Immunodeficiency Virus

We examined the IgM VH gene subgroup use-distribution in serial blood samples of 37 human immunodeficiency virus (HIV)-infected patients and a group of HIV-seronegative healthy adults. The IgM VH gene repertoires of healthy adults were relatively similar to one another and were stable over time. In contrast, individuals infected with HIV had IgM VH gene repertoires that were significantly more heterogeneous and unstable. Persons at early stages of HIV infection generally had abnormal expression levels of Ig VH3 genes and frequently displayed marked fluctuations in the relative expression levels of this VHgene subgroup over time. In contrast, persons with established acquired immunodeficiency syndrome (AIDS) had a significantly lower incidence of abnormalities in Ig VH3 expression levels, although continued to display abnormalities and instability in the expression levels of the smaller Ig VH gene subgroups. Moreover, the skewing and/or fluctuations in the expressed-IgM VHgene repertoire appeared greatest for persons at earlier stages of HIV infection. These studies show that persons infected with HIV have aberrant and unstable expression of immunoglobulin genes suggestive of a high degree humoral immune dysregulation and ongoing humoral immune responses to HIV-associated antigens and superantigens.

© 1998 by The American Society of Hematology.

Primary central nervous system lymphomas in immunocompetent individuals: histology, Epstein-Barr virus genome, Ki-67 proliferation index, p53 and bcl-2 gene expression

Epstein-Barr virus (EBV) has been detected in the large majority of HIV-related primary central nervous system lymphomas (PCNSL) suggesting a pathogenetic role of the virus. Unlike HIV-related PCNSL, conflicting data exist with regard to the presence of EBV in non immunodeficiency-related (sporadic) PCNSL. For this reason, a population based material of 41 sporadic PCNSL was analysed for the presence of EBV genome (EBER, BHLF) using RNA in situ hybridisation (RISH). Furthermore, the expression of the gene products of the bcl-2 oncogene and the p53 tumor suppressor gene and the tumor growth fraction reactive with the monoclonal antibody Ki-67 have been evaluated. All cases but two were EBV genome negative. In the two positive cases less than 5% of tumor cells showed EBER positivity. In contrast, more than 75% of cells morphologically belonging to the tumor-cell population stained positively for EBER in two cases of HIV related PCNSL. Immunostaining for the bcl-2 oncoprotein was positive in 28 (72%) of 39 cases examined. In most cases more than 75% of tumor cells showed cytoplasmic expression. Of 37 cases investigated for p53 expression, 21 (57%) stained positively. However, in the large majority of positive cases less than 10% of the neoplastic cells stained. The percentage of Ki-67 positive cells ranged between 10% and 80% with a mean of 50%. The expression of the p53 and bcl-2 oncoproteins and the growth fraction did not have any prognostic impact. We conclude that the EBV genome is rarely detected in sporadic PCNSL, indicating that a pathogenetic role of EBV is unlikely. Like extracerebral B-cell lymphomas a large fraction of PCNSL expresses the p53 and bcl-2 oncoproteins, a feature, however, which does not seem to have prognostic implications.

EBV-positive primary central nervous system lymphomas in monozygote twins with common variable immunodeficiency and suspected multiple sclerosis

Common variable immunodeficiency represents the most frequently occurring primary immunodeficiency disorder and is usually detected sporadically in patients with no family history of immunodeficiency. We present the case stories of two monozygote twins, who following a period of decreasing serum immunoglobulins developed primary central nervous system lymphomas. One twin had clinical and paraclinical features mimicking multiple sclerosis. Immunohistochemical investigations on biopsy tissue showed expression of the bcl-2 and p53 gene products, and Epstein-Barr virus (EBV) encoded small RNA's (EBER) indicating latent infection were detected in lymphoma cells using in situ hybridisation techniques. The pathogenetic role of EBV in oncogenesis is discussed.

AIDS-related Kaposi's sarcoma. A template for the translation of molecular pathogenesis into targeted therapeutic approaches

AIDS-related Kaposi's sarcoma (KS) represents a complex interaction of host and viral factors. There are a number of fundamental questions surrounding the interplay between the disparate factors that can contribute to the pathogenesis and pathophysiology of this disease. Targets such as the enhancement of immune function, inhibition of angiogenic factors or immunostimulatory cytokines, inhibition of viral proteins such as Tat, or hormonal manipulations are now or will in the future become the focus of research to develop innovative anti-KS therapy and prevention measures. Antiviral approaches aimed at HIV or other viruses may potentially target a number of steps in KS pathogenesis. This article reviews diverse modalities--cytotoxic, antiviral, gene-directed, growth factor-targeted, and antiangiogenesis--that singly, or more likely in combination, stand to make an impact on the cure and prevention of AIDS-related KS.

Neoplastic cells of Hodgkin's disease show differences in EBV expression between Kenya and Italy

The Epstein-Barr Virus (EBV) has been implicated in the pathogenesis of Hodgkin's disease (HD). However, the association of EBV with this disease varies greatly from series to series and from country to country. Epidemiological studies have shown differences in HD occurring in different parts of the world. In particular, it has been reported that HD in developing countries differs from HD in Western countries in terms of epidemiological, pathological and clinical characteristics. These discrepancies among populations suggest an interaction with environmental factors and a direct role of different etiological agents. At present, there are no data on the frequency of association of EBV with HD in equatorial Africa. In this study, a large series of HD cases have been collected at the University of Nairobi, Kenya, and at the Universities of Bologna and Siena, Italy. The cases have been reviewed and classified according to the REAL Classification and the presence of EBV has been assessed by in situ hybridization (ISH). A statistical difference in EBV expression was found between HD from Kenya and HD from Italy. EBV-positive neoplastic cells were detected in 92% of Kenyan cases, whereas only 48% of Italian cases showed EBER1/2 positivity in the neoplastic cells. Our results suggest that, in Kenya, EBV plays a more direct role in the pathogenesis of HD, as it does for endemic Burkitt lymphoma.

Persistence of immunoglobulin heavy chain/c-myc recombination-positive lymphocyte clones in the blood of human immunodeficiency virus-infected homosexual men

We studied blood lymphocytes of human immunodeficiency virus (HIV)-seropositive and -negative homosexual men for the presence of T(8;14) translocations that recombine c-myc and immunoglobulin heavy-chain (IgH) mu/IgH alpha switch regions. Clones with T(8;14) translocations were detected in 10.5% (12/114) of the HIV-positive and in 2.0% of the 99 uninfected patients. The majority of recombinations were found at a single time point only. Four patients, however, harbored multiple (up to four) and persistent (up to 9 years) translocation-positive cell clones. No correlation between the presence of these aberrant lymphocytes and a later lymphoma could be established. The exon 1/intron 1 region of the recombined c-myc was investigated for the presence of point mutations and these were found in the nonpersistent clones. Additional alterations detected in these clones included duplications and a deletion in the c-myc gene. The pattern of base substitution indicates that they were introduced after the translocation event.

Lymphoma associated with human immunodeficiency virus infection

OBJECTIVE

To describe lymphoma associated with human immunodeficiency virus (HIV) infection.

DESIGN

A review of HIV-related lymphoma and its associated epidemiology, etiopathogenesis, and clinicopathologic characteristics is presented. Major studies of therapeutic regimens for HIV-related lymphoma are discussed. Factors that could contribute to a poor prognosis are summarized.

RESULTS

Malignant lymphoma that develops in patients with HIV infection fulfills diagnostic criteria for the acquired immunodeficiency syndrome (AIDS). The incidence is increasing and varies by subtype of lymphoma, age, sex, race, and risk factors. B-cell hyperactivation is thought to contribute to the development of lymphoma. The mechanisms that may show transformed cell hyperproliferation and clonal expansion are HIV itself or other viruses (for example, Epstein-Barr virus), growth factors, aberrant oncogene or tumor-suppressor gene expression, and factors that induce genetic instability or DNA damage or alter host or viral genome repair. Treatment of HIV-related lymphoma is associated with toxicity, infectious complications, low rate of complete response, and brief median survival time.

CONCLUSION

Persons with HIV-induced immune dysregulation have a high risk for the development of aggressive non-Hodgkin's lymphoma characterized by histologic evidence of a high-grade malignant process, B-cell phenotype, an unusual extranodal involvement, and a poor prognosis. The potential role of specific viruses, antiviral treatments, and other therapeutic strategies are future areas of investigation.

Hodgkin's disease as an indicator of AIDS

Hodgkin's disease (HD) is not currently included within the Centers for Disease Control (CDC) classification system for AIDS. Upon HD diagnosis, HIV(human immunosuppressive virus)-positive patients are generally found within Stages III or IV of the Ann Arbor HD classification system, already exacerbating the problem of treatment. In contrast, HIV-negative patients diagnosed with HD are generally found within Stages I or II. Epidemiology and the presence of secondary lymphomas, opportunistic infections, or aggressive pathologies, accompanied by low survival rate and timing of HD diagnosis suggest that HD should be included among conditions indicating AIDS manifestation.