Productive HIV-2 infection in the brain is restricted to macrophages/microglia.

OBJECTIVES: HIV-2 can use a broader range of co-receptors than HIV-1 in vitro, and is less dependent on CD4 for infection. The aim of this study was to detect productive HIV-2 infection in the brain and investigate whether HIV-2 has an expanded tropism for brain cells in vivo, in comparison with HIV-1, which productively infects macrophages/microglia. DESIGN: Brain samples taken at autopsy from eight patients who died from AIDS, six HIV-2 and two HIV-1/HIV-2 dually seropositive, with HIV encephalitis (HIVE), collected in Abidjan, Côte d'Ivoire in 1991, were examined for the presence and localization of productive HIV-2 infection. METHODS: Using immunohistochemistry, the presence of HIV-2 p26 in formalin-fixed, wax-embedded brain tissue sections was investigated. Double-staining with glial fibrillary acidic protein (GFAP), CD45- and CD68-specific antibodies was performed to identify infected cell types. RESULTS: HIV-2 p26 was detected in brain tissue from four of the HIV-2 cases and one of the dually infected individuals. The productively infected cells were either microglia or infiltrating macrophages. CONCLUSIONS: The productively infected cells in the brains of HIV-2 infected individuals are macrophages/microglia. No evidence was found for productive infection of astrocytes, neurons or oligodendrocytes. Thus, the broader in vitro cell tropism, promiscuous coreceptor usage and relative independence of CD4 by HIV-2 compared to HIV-1 does not broaden its range of target cells in the brain.

Risk of lymphoid neoplasia after cardiothoracic transplantation: the influence of underlying disease and human leukocyte antigen type and matching.

BACKGROUND: It has been known for more than 20 years that there is an increased risk of lymphoid neoplasia after cardiothoracic transplantation. Recent studies have demonstrated the importance of primary Epstein-Barr virus (EBV) infection and type of immunosuppressive therapy to the cause of these neoplasms, but the contribution of other factors remains equivocal. METHODS: The authors followed 1,562 patients undergoing cardiothoracic transplantation at Harefield Hospital, United Kingdom, and used standard cohort methods of analysis to examine whether posttransplant lymphoma risk was related to the underlying disease requiring transplantation or the human leukocyte antigen (HLA) type and matching. Lymphomas were categorized into EBV-associated lymphoproliferative disease (LPD) and EBV-negative non-Hodgkin's lymphoma (NHL), and the authors carried out separate analyses of these. RESULTS: The authors found no significant association between the underlying disease necessitating transplantation and the risk of lymphoid neoplasia. There was also no evidence of a relation of lymphoma risk with the presence or absence of any particular HLA antigen, although significant protective effects of HLA-B14 and -B57 were found when analyses were conducted without adjustment for multiple testing. Risk of LPD was not associated with degree of HLA mismatching, but there was a significant effect of mismatching on risk of EBV-negative tumors. CONCLUSIONS: The differential effect of HLA mismatching on the risks of LPD and EBV-negative NHL provides further evidence that these two tumors are distinct etiologic entities. The authors' results suggest that the immunologic cause of EBV-negative NHL may be different from that of LPD. Investigation of the relation of risk of EBV-negative NHL to degree of immunosuppression is needed.

Persistent Epstein-Barr virus infection: unrestricted latent and lytic viral gene expression in healthy immunosuppressed transplant recipients.

BACKGROUND: Posttransplant lymphoproliferative disease (PTLD) is a common Epstein-Barr virus (EBV)-associated complication of transplantation which, despite treatment, is often fatal. This study was undertaken to monitor persistent EBV infection in transplant recipients, to compare EBV load and gene expression in healthy individuals and EBV-associated diseases, and to highlight differences in PTLD that could be used to define those at risk of the disease. METHODS: A cohort of 96 cardiothoracic transplant recipients was monitored posttransplant for up to 1110 days (median 268 days). Levels of EBV DNA and viral mRNA transcripts in peripheral blood mononuclear cells (PBMs) were measured at regular intervals and compared with those found in healthy individuals, infectious mononucleosis (IM) patients, and 12 PTLD patients bled at the time of diagnosis. Overall posttransplant levels were significantly higher than pretransplant and healthy subjects, and correlate with dose of immunosuppression. EBV DNA levels in both IM and PTLD were significantly higher than in healthy recipients, with the highest levels in PTLD patients. Individual measurements in 12 healthy transplant recipients reached levels seen in PTLD, and thus single estimations are not of predictive significance for PTLD development. RESULTS: Analysis of viral gene expression in peripheral blood mononuclear cells showed a restricted (LMP 2 only) pattern in healthy subjects, and an unrestricted (latency 3) pattern with lytic replication in 14% of IM blood and 45% of cases of PTLD. A total of 55% of healthy transplant recipients had additional transcripts in one or more blood samples, and this finding correlated with high viral load. Analysis of the 12 samples from healthy recipients with viral loads equivalent to those seen in PTLD showed additional transcripts in all cases and latency 3 with lytic replication in 33%. Thus, an isolated finding of high viral load and/or unrestricted latent and lytic gene expression is not indicative of PTLD.

Biogenesis of secretory organelles during B cell differentiation.

The differentiation of B cells into Ig-secreting plasma cells requires the expansion of secretory organelles to cope with the increased cargo load. To evaluate the timeline of this process, we have quantitated the kinetics of secretory organelle expansion relative to Ig secretion and examined regulatory components of secretory transport following in vitro activation of human B lymphocytes. Unstimulated B cells contain minimal endomembranes. After activation, ER membrane induction appears as tightly packed spherical structures of 0.5-1 mum diameter concentrated in a juxtanuclear position. When the cells differentiate into plasmablasts, there is dramatic cell-size increase, but the ER remains concentrated close to the nucleus and only later fills the entire cell. In sharp contrast, previous studies in other cell types have found that the ER expands in synchrony with increasing cell size during interphase, by extension of ER tubules under the PM. In this study, the Golgi remains consistently as a single juxtanuclear structure but linearly expands sixfold in volume during B cell activation. Furthermore, following active cell proliferation, ER exit sites proliferate rapidly, increasing almost fourfold in number, in parallel with a sharp increase in Ig secretion. These findings demonstrate that the control of organelle biogenesis and expansion in primary human B cells are differentially regulated by cargo flux caused by Ig synthesis.

Expansion in scid mice of Epstein-Barr virus-associated post-transplantation lymphoproliferative disease biopsy material.

Post-transplant lymphoproliferative disease (PTLD) biopsy material is rarely available in adequate quantity for research. Therefore, the present study was designed to expand biopsy material in scid mice. Epstein-Barr virus (EBV)+ve PTLD samples from five transplant patients were established in scid mice. PCR analysis of immunoglobulin gene rearrangements demonstrated that four of the five biopsies (80%) gave rise to scid tumours which represented the original tumour cell clones. Immunophenotyping showed that these four biopsies (and all scid tumours) expressed all EBV latent genes and a B lymphoblast phenotype;