Three cases of primary cerebral lymphoma in AIDS patients: detection of Epstein-Barr virus by in situ hybridization and Southern blot technique

Morphologic and immunophenotypic characteristics of malignant lymphomas in SIV-infected rhesus macaques

Eight cases of extranodal non-Hodgkin's lymphoma in simian immunodeficiency virus (SIV)-infected rhesus macaques, aged 4-9 years, were phenotypically and immunologically characterized, using the updated Kiel classification, in order to determine both the differences and the similarities between these types of lymphoma in immunodeficient rhesus macaques (Macaca mulatta) and man. The high-grade malignant tumors were of B-cell origin, with a predilection for extranodal growth in viscera and periorbital tissues. Immunophenotypical characterization showed that the monkey lymphomas were similar in many aspects to human immunodeficiency virus-associated lymphomas. The number of Ki67 positive cells varied from case to case and ranged from 50 to 90%. A serological screening for the simian equivalent of the Epstein-Barr virus (sEBV) by immunofluorescence assay revealed a prevalence of 92% of the sEBV antibodies in our cohort. The presence of Ebstein-Barr virus nuclear antigen (EBNA-2) could be demonstrated by immunohistochemistry in four out of eight cases. In situ hybridization revealed the presence of small EBV-encoded RNAs (EBER-1, EBER-2) in six of the eight cases. Further studies should define the precise role of herpesvirus infection for lymphomagenesis in SIV-induced immunodeficiency.

Herpes simplex virus type 1 encephalitis in acquired immunodeficiency syndrome

Herpes simplex (HSV) infection of the central nervous system is uncommon in AIDS and usually has an atypical topography. This review is centred around the case of a 49-year-old homosexual patient with AIDS who died from diffuse encephalopathy. Neuropathological examination revealed necrotic and haemorrhagic changes involving both temporal lobes, insulae and cingulate gyri. Cowdry type A intranuclear inclusion bodies were abundant but inflammation was minimal. Electron microscopy confirmed characteristic herpes virus particles. Immunocyto-chemistry was positive for HSV type 1 and 2. In situ hybridization and PCR, however, were positive for HSV type 1 but excluded HSV type 2. There was associated cytomegalovirus ventriculitis but clearly separated from HSV encephalitis. There were no histological features of HIV encephalitis and HIV could not be demonstrated by immunocytochemistry or by PCR to demonstrate proviral DNA. Apoptotic neurons were numerous in areas with a severe macrophage reaction. Only two pathological cases with characteristic limbic distribution and necrotic haemorrhagic histologic have been reported previously. The rarity of these reports suggests that in advanced AIDS, the immune reaction causing a typical necrotizing encephalitis cannot be mounted. Distinction between HSV type 1 and 2 infection may be difficult by immunocytochemistry and usually requires in situ hybridization, tissue culture or PCR. In AIDS patients, HSV-1 has been identified as responsible for encephalitis whereas HSV-2 has been more responsible for myelitis. Associated productive HIV infection of the CNS was found in none of the cases. In contrast, cytomegalovirus encephalitis was found in nine of 11 cases of AIDS-associated HSV encephalitis.

Concurrent herpes simplex type 1 necrotizing encephalitis, cytomegalovirus ventriculoencephalitis and cerebral lymphoma in an AIDS patient

Unlike cytomegalovirus (CMV) ventriculoencephalitis, herpes simplex virus type 1 necrotizing encephalitis has only rarely been observed in AIDS patients. A 40-year-old bisexual man was followed for an HIV1 infection from 1987 onwards. In June 1993 he was referred for sudden confusion, left hemiparesia and fever. The blood contained less than 10 CD4 lymphocytes/mm3. The patient remained comatose and febrile, and died 4 weeks later. In coronal sections of the brain there was necrosis of the internal parts of the left temporal lobe, necrosis of certain areas of the ventricular walls and a small tumor at the top of the right frontal lobe, which proved to be a polymorphic high-grade lymphoma. CMV ventriculoencephalitis lesions were prominent in the ventricular walls of the occipital lobes and there was a strong nuclear signal for CMV using in situ hybridization. Herpes simplex virus type 1 was shown in the nuclei and cytoplasm of certain neurons and astrocytes in the borders of the necrotized temporal lobe areas by immunohistochemistry, in situ hybridization and electron microscopy, whereas in situ hybridization and immunohistochemistry for CMV were negative in such areas. Necrotizing type 1 encephalitis must not be overlooked in immunodeficient patients.

Primary central nervous system malignant non-Hodgkin's lymphomas from HIV-infected and non-infected patients: expression of cellular surface proteins and Epstein-Barr viral markers

The increased incidence of primary central nervous system malignant non-Hodgkin's lymphomas (PCNSL) in HIV- and non-HIV-infected patients and the demonstration of Epstein-Barr virus (EBV) in these tumours may indicate relationships between PCNSL and EBV. Consequently expression of EBV-induced antigens and cellular markers were studied in 11 HIV-infected and seven non-infected patients by in situ hybridization (ISH) and immunocytochemistry in monoclonal B cell PCNSL. In HIV-infected patients EBV genome was present in 9/11 cases, LMP in 11/11 cases and EBNA2 in 10/11 cases. The expression of adhesion and activation molecules was low or absent. In HIV non-infected patients, EBV genome was present in 5/7 cases, with LMP in 4/7 cases. EBNA2 was never detected. All these lymphomas expressed LFA1beta. Whatever the population, no lytic cycle EBV markers were detected. Compared with other types of EBV lymphomas, our results suggest a different EBV latency state in primary B cell lymphomas of the CNS from HIV-infected or non-infected patients.

Primary central nervous system lymphomas--an update

Primary CNS lymphomas (PCNSL), until recently representing about 1% of all brain tumors, show dramatically increased incidence both in high-risk groups (immunocompromised, AIDS) and in the general population. They are extranodal diffuse non-Hodgkin's lymphomas, the morphology and classification of which are identical to those of systemic lymphomas, although PCNSL show different biological behavior and diagnosis according to the New Working Formulation and updated Kiel classification may be difficult. The majority are large B cell variants of high-grade malignancy; low-grade subtypes and T cell lymphomas are rare. Sixty per cent occur in the supratentorial space (hemispheres, periventricular) and 12% in the posterior fossa; 30% are multiple (50%-70% in AIDS). PCNSL show a male preponderance with a peak incidence in the 5th-7th decade (3rd-4th in AIDS). The duration of diffuse or focal clinical symptoms averages 1-2 months. Computed tomography and magnetic resonance imaging scans show single or multiple or diffuse, often typical lesions. Diagnosis is achieved by evaluation of stereotactic biopsy material or cerebrospinal fluid cytology using immunocytological markers. Current therapy in immunocompetent patients, radiation plus corticosteroids and pre- or postradiation polychemotherapy, shows response rates of 85% with a median survival of 17-44 months, a prognosis similar to that for glioblastoma. Meningeal PCNSL is treated with intrathecal methotrexate or cytosine arabinoside. Transliquoral seeding of PCNSL is frequent, distant metastases occurring in 6%-8%. Therapy of AIDS-related PCNSL makes use of radiation and corticosteroids, and rarely of chemotherapy. The pathogenesis of PCNSL is unknown, but Epstein-Barr virus may be a contributory factor.