Kaposi's sarcoma and malignant lymphomas in Tanzania during the AIDS epidemic

Abstract

Kaposi s sarcoma (KS) studies Kaposi´s sarcoma (KS) is the most frequent AIDS tumor (AKS) and associated with HHV-8, but controversial whether a clonal tumor or mostly a reactive proliferation of endothelial spindle cells (SC). In the present studies AKS and endemic KS (EKS) biopsies were compared for expression of HHV-8-LANA, the lymphatic endothelial (LEC) markers LYVE-1 and Ki-67 (proliferation).

The study material is archival, formalin-fixed and paraffin-embedded (FFPE) surgical KS biopsies and sera from the Muhimbili National Hospital (MNH, Dar es Salaam, Tanzania) at early and late tumor stages of African AKS and EKS cases with cutaneous and oral (OKS) lesions from male, female, adult and juvenile KS patients.

KS histopathological and immunohistochemical (IHC) studies (papers I-III) by single, double and/or triple antibody immunofluorescence (IFA) showed that: a) LANA+/CD34- cells were more frequent in early as compared to late KS and most of them expressed LEC markers LYVE-1, D2-40 and VEGFR-3, suggesting that the resident LECs represent an early target of primary HHV-8 infection; b) LANA+/CD34-/LYVE-1+ cells decreased from early (25%) to late (4%) KS while LANA+/CD34+ SC increased suggesting a phenotype switch from LEC to VEC; c) LANA appeared better correlated to LYVE-1 (LEC) than to CD34 (VEC) expression suggesting heterogeneous SC permissiveness to HHV-8 (paper I); d) the number of HHV-8 infected (LANA+) SC (CD34+) cells as well as LANA+ granules per SC nucleus was significantly higher in male vs. female, juvenile vs. adult and oral AKS [OAKS] vs. cutaneous KS lesions; e) similarly, tumor cell proliferation (Ki-67 immunoreactivity) in adult OAKS was significantly higher for male vs. female, juvenile vs. adult and OAKS vs. cutaneous KS lesions respectively; f) a positive correlation was apparently found between LANA+ SC and Ki-67 immunoreactivity (paper II).

Together these findings suggest that tumor proliferation correlates with increasing HHV-8 LANA expression supporting the notion of viral (LANA)-driven cell proliferation during KS oncogenesis (paper II); g) a significantly higher viral load was also seen by quantitative RT-PCR in late nodular OAKS compared with cutaneous AKS lesions corroborating IHC results and indicating that the oral cavity is important for entry and/or reservoir for HHV-8 infection (papers II & III); h) the frequency of LANA+ SC in the tumor increases during the evolution of both cutaneous and oral KS lesions, suggesting a correlation between tumor growth and viral replication in the lesions, however, by RT-PCR, we observed that serum viral loads appeared to decrease in the corresponding patients whereas (paper III) all sera from early stage (patch-plaque) KS were positive for anti-HHV-8 antibodies while all HHV-8 negative sera were from late-stage nodular KS patients (paper IV). This supports our novel notion of a stage-dependent tissue-serum discrepancy in viral loads and HHV-8 antigen expression probably due to virus tissue retention, immune-segregation and/or selective clearance.

Thus serum HHV-8 viral loads may not be sufficient for clinical and therapeutic prognostication (papers III & IV); i) the frequency of HHV-8 infection was high among the studied MNH cases and as expected, HHV-8 and HIV infection was more associated with KS compared to non-KS tumors and non-neoplastic conditions; j) the findings by IFA and ELISA had a high HHV-8 diagnostic concordance although ELISA seemed to have higher positive predictive value (PPV), specificity as well as a high sensitivity allowing more affordable HHV-8 screening in a resource-constrained country like Tanzania (paper IV). These findings also indicate the importance of routine HHV-8 screening among blood/organ donors to prevent transmission as well as in prospective transplant recipients to predict and possibly prevent iatrogenic KS (IKS) development (paper IV).

Malignant lymphoma (ML) studies ML are second to KS as AIDS-related malignancies and have been reported to increase steadily with the HIV pandemic particularly in sub-Saharan Africa including Tanzania. The WHO classification, HIV and EBV association as well as ploidy and heterogeneity of diffuse large B-cell lymphoma (DLBCL) in Tanzania is not well documented. Our current study (paper V) has established that the WHO classification of lymphoid neoplasms can apparently be applied for the diagnosis of Tanzanian ML. Extranodal presentation of ML was frequent particularly for T-cell lymphomas (TCL). Diffuse large B-cell lymphoma (DLBCL) phenotype heterogeneity and frequency at MNH (Tanzania) was similar to that observed in Western countries suggesting applicability of similar, diagnostic, prognostic and therapeutic approaches (paper V). The attended ML at MNH had frequent aneuploidy, EBV infection as well as high DNA indices and cell proliferation (Ki-67). HIV infection was apparently associated with increased ML cell proliferation (paper V).