Resistance to intranasal infection with Balamuthia mandrillaris amebae is T-cell dependent.

T and B cell-deficient BALB/c SCID mice become severely ill and die of amebic encephalitis after intranasal infection with Balamuthia mandrillaris, while adult immunocompetent BALB/c wild-type (WT) mice are resistant. To further investigate the role of lymphocytes in protection from Balamuthia amebic encephalitis (BAE), SCID mice were reconstituted with and WT mice selectively depleted of lymphocytes before infection. Reconstitution of SCID mice with whole spleen cells from WT mice rendered the recipients as resistant to BAE as WT mice. SCID mice that had received spleen cells depleted of CD4(+) T cells remained susceptible. When adult WT mice were depleted of both CD4(+) and CD8(+) T cells or of CD4(+) T cells alone, these mice also became susceptible to BAE. Depletion of CD8(+) T cells alone increased susceptibility only marginally. All morbidity and mortality data were underpinned by histological analysis of the brain.

Presence of occult cytomegalovirus infection in the brain after orthotopic liver transplantation. An autopsy study of 83 cases.

Cytomegalovirus (CMV) infection remains a highly prevalent systemic complication following orthotopic liver transplantation (LT), accounting for a significant increase in morbidity and affiliated costs. However, unlike other immunosuppressed groups of population, CMV infection of the central nervous system in LT is rarely diagnosed, either clinically or postmortem. Furthermore, in 20% of the LT patients who develop preterminal neurological complications, the etiology remains undetermined. With the hypothesis that at least some of these cases could be related to an occult CMV infection, we examined brain tissue from 83 unselected autopsies of LT patients by morphological, immunohistochemical (IHC), in situ hybridization (ISH), and nested polymerase chain reaction (nested PCR) techniques. Microglial nodules were observed in 17 brains of the LT group (20.4%) but in none of the 36 controls. Isolated positive cells by either IHC, ISH, or both techniques, were identified in 11 LT patients (13.2%) and in 2 controls (5.5%). CMV DNA amplification was obtained from paraffin-embedded tissues in 41 of 81 LT cases (50.6%), and in 5 controls (13.8%) (P=0.00017). Viral inclusion bodies, inflammatory infiltrates, or necrotizing changes were not identified in any case. Our findings indicate an increased susceptibility of the brain of LT patients to occult infection by CMV and suggest that a latent or low-grade infection of the central nervous system could operate as a reservoir of the CMV and play a role in some of the unexplained neurological symptoms that appear in the postoperative period.

Microdissection genotyping of mixed glial and primitive neuroectodermal central nervous system neoplasm.

A 22-year-old man with previous radiation treatment for childhood astrocytoma underwent resection of a right parietooccipital lesion. Histopathology revealed a malignant neoplasm with areas of astrocytic and primitive neuroectodermal components. To resolve the relationship and cellular origin, representative tissue was microdissected from several targets, obtaining a balanced mixture of each element. Nonneoplastic brain parenchyma was separately microdissected to determine polymorphic marker informativeness and to serve as an internal negative control. Despite the relatively small quantity of tissue removed for each microdissection target, sufficient material was available for reliable, balanced, polymerase chain reaction-format genotyping encompassing a panel of tumor suppressor genes and genetic loci associated with these forms of neoplasia. The findings revealed distinct discordant genotypic profiles for each of the neoplastic components. The efficacy of the approach used for molecular analysis of this complex neoplasm and the implication of the genotypic findings are discussed.

Environmental isolation of Balamuthia mandrillaris associated with a case of amebic encephalitis.

This report describes the first isolation of the ameba Balamuthia mandrillaris from an environmental soil sample associated with a fatal case of amebic encephalitis in a northern California child. Isolation of the ameba into culture from autopsied brain tissue confirmed the presence of Balamuthia: In trying to locate a possible source of infection, soil and water samples from the child's home and play areas were examined for the presence of Balamuthia: The environmental samples (plated onto nonnutrient agar with Escherichia coli as a food source) contained, in addition to the ameba, a variety of soil organisms, including other amebas, ciliates, fungi, and nematodes, as contaminants. Presumptive Balamuthia amebas were recognized only after cultures had been kept for several weeks, after they had burrowed into the agar. These were transferred through a succession of nonnutrient agar plates to eliminate fungal and other contaminants. In subsequent transfers, axenic Naegleria amebas and, later, tissue cultures (monkey kidney cells) served as the food source. Finally, the amebas were transferred to cell-free axenic medium. In vitro, the Balamuthia isolate is a slow-growing organism with a generation time of approximately 30 h and produces populations of approximately 2 x 10(5) amebas per ml. It was confirmed as Balamuthia by indirect immunofluorescence staining with rabbit anti-Balamuthia serum and human anti-Balamuthia antibody-containing serum from the amebic encephalitis patient. The environmental isolate is similar in its antimicrobial sensitivities and identical in its 16S ribosomal DNA sequences to the Balamuthia isolate from the deceased patient.