Revisiting the Effect of Acute P. falciparum Malaria on Epstein-Barr Virus: Host Balance in the Setting of Reduced Malaria Endemicity

Burkitt's lymphoma (BL), an EBV-associated tumour, occurs at high incidence in populations where malaria is holoendemic. Previous studies in one such population suggested that acute P.falciparum infection impairs EBV-specific T-cell surveillance, allowing expansion of EBV infected B-cells from which BL derives. We re-examined the situation in the same area, The Gambia, after a reduction in malaria endemicity. Cellular immune responses to EBV were measured in children with uncomplicated malaria before (day 0) and after treatment (day 28), comparing EBV genome loads in blood and EBV-specific CD8+ T-cell numbers (assayed by MHC Class I tetramers and IFNγ ELISPOTS) with those seen in age- and sex-matched healthy controls. No significant changes were seen in EBV genome loads, percentage of EBV-specific CD8+ T-cells and IFNγ producing T-cells in acute versus convalescent samples, nor any difference versus controls. Regression assays performed also no longer detected any impairment of EBV-specific T-cell surveillance. Acute uncomplicated malaria infection no longer alters EBV-specific immune responses in children in The Gambia. Given the recent decline in malaria incidence in that country, we hypothesise that gross disturbance of the EBV-host balance may be a specific effect of acute malaria only in children with a history of chronic/recurrent malaria challenge

The WiggleZ Dark Energy Survey: galaxy evolution at 0.25 ≤ z ≤ 0.75 using the second red-sequence cluster survey

We study the evolution of galaxy populations around the spectroscopic WiggleZ sample of star-forming galaxies at 0.2

Different patterns of Epstein-Barr virus latency in endemic Burkitt lymphoma (BL) lead to distinct variants within the BL-associated gene expression signature

Epstein-Barr virus (EBV) is present in all cases of endemic Burkitt lymphoma (BL) but in few European/North American sporadic BLs. Gene expression arrays of sporadic tumors have defined a consensus BL profile within which tumors are classifiable as "molecular BL" (mBL). Where endemic BLs fall relative to this profile remains unclear, since they not only carry EBV but also display one of two different forms of virus latency. Here, we use early-passage BL cell lines from different tumors, and BL subclones from a single tumor, to compare EBV-negative cells with EBV-positive cells displaying either classical latency I EBV infection (where EBNA1 is the only EBV antigen expressed from the wild-type EBV genome) or Wp-restricted latency (where an EBNA2 gene-deleted virus genome broadens antigen expression to include the EBNA3A, -3B, and -3C proteins and BHRF1). Expression arrays show that both types of endemic BL fall within the mBL classification. However, while EBV-negative and latency I BLs show overlapping profiles, Wp-restricted BLs form a distinct subgroup, characterized by a detectable downregulation of the germinal center (GC)-associated marker Bcl6 and upregulation of genes marking early plasmacytoid differentiation, notably IRF4 and BLIMP1. Importantly, these same changes can be induced in EBV-negative or latency I BL cells by infection with an EBNA2-knockout virus. Thus, we infer that the distinct gene profile of Wp-restricted BLs does not reflect differences in the identity of the tumor progenitor cell per se but differences imposed on a common progenitor by broadened EBV gene expression

Upregulation of bcl-2 by the Epstein-Barr virus latent membrane protein LMP1: a B-cell-specific response that is delayed relative to NF-kappa B activation and to induction of cell surface markers.

An ability of the Epstein-Barr virus latent membrane protein LMP1 to enhance the survival of infected B cells through upregulation of the bcl-2 oncogene was first suggested by experiments involving gene transfection and the selection of stable LMP1+ clones (S. Henderson, M. Rowe, C. Gregory, F. Wang, E. Kieff, and A. Rickinson, Cell 65:1107-1115, 1991). However, it was not possible to ascertain whether Bcl-2 upregulation was a specific consequence of LMP1 expression or an artifact of the selection procedure whereby rare Bcl-2+ cells already present in the starting population might best be able to tolerate the potentially toxic effects of LMP1. We therefore reexamined this issue by using two different experimental approaches that allowed LMP1-induced effects to be monitored immediately following expression of the viral protein and in the absence of selective pressures; activation of the NF-kappa B transcription factor and upregulation of the cell adhesion molecule ICAM-1 were used as early indices of LMP1 function. In the first approach, stable clones of two B-cell lines carrying an LMP1 gene under the control of an inducible metallothionein promoter were induced to express LMP1 in all cells. Activation of NK-kappa B and upregulation of ICAM-1 occurred within 24 h and were followed at 48 to 72 h by upregulation of Bcl-2. In the second approach, we tested the generality of this phenomenon by transiently expressing LMP1 from a strong constitutively active promoter in a range of different cell types. All six B-cell lines tested showed NF-kappa B activation in response to LMP1 expression, and this was followed in five of six lines by expression of ICAM-1 and Bcl-2. In the same experiments, all three non-B-cell lines showed NF-kappa B activation and ICAM-1 upregulation but never any effect upon Bcl-2. We therefore conclude that Bcl-2 upregulation is part of the panoply of cellular changes induced by LMP1 but that the effect is cell type specific. Our data also suggest that whilst NF-kappa B may be an essential component of LMP1 signal transduction, other cell-specific factors may be required to effect some functions of the viral protein

Frequency of multiple Epstein-Barr virus infections in T-cell-immunocompromised individuals

The Epstein-Barr virus (EBV) carrier state is characterized by latent infection of the general B-cell pool and by chronic virus replication at oropharyngeal sites. In Caucasian populations, most healthy carriers seem to harbor one dominant transforming virus strain, usually of type I rather than type 2, which persists over time and is detectable both in the blood and in the throat. This finding implies that once the virus carrier state is established, both viral reservoirs are largely if not completely protected from infection with additional strains. However, it is not known which facets of the immune response offer that protection. Here we address this question by a detailed study of EBV carriage in patients T-cell immunocompromised as a result of chronic human immunodeficiency virus (HIV) infection. Resident EBV strains were rescued from blood and from throat washings by using an in vitro transformation assay which aims to minimize bias toward faster-growing transformants; in this way, a mean of 16 independent isolations were made from each of 35 HIV-positive (predominantly male homosexual) patients. These virus isolates were characterized first at the DNA level by PCR amplification across type-specific polymorphisms in the EBNA2 and EBNA3C genes and across the 30-bp deletion and 33-bp repeat loci in the LMP1 gene and then at the protein level by immunoblotting for the strain-specific "EBNAprint" of EBNA1, -2, and -3C molecular weights. By these criteria, 18 of 35 patients harbored only one detectable EBV strain, usually of type 1, as do healthy carriers. However, the other 17 patients showed clear evidence of multiple infection with different EBV strains. In eight cases these strains were of the same type, again usually type 1, and were more often found coresident in throat washings than in the blood. By contrast, a further nine patients gave evidence of coinfection with type 1 and type 2 strains, and in these cases both virus types were detectable in the blood as well as in the throat. Immunological assays on these HIV-positive patients as a group showed a marked impairment of T-cell responses, reflected in reduced levels of EBV-specific cytotoxic T-cell memory, but an elevation of humoral responses, reflected in raised antibody titers to the EBV envelope glycoprotein gp340 and by the maintenance of virus neutralizing antibodies in serum. We infer that selective impairment of the T-cell system predisposes the host to infection with additional exogenously transmitted EBV strains

Isolation of intertypic recombinants of Epstein-Barr virus from T-cell-immunocompromised individuals

All wild-type isolates of Epstein-Barr virus (EBV) analyzed to date for allelic polymorphisms of the nuclear antigen EBNA2 gene (in the BamHI YH region of the genome) and of the EBNA3A,-3B, -3C genes (tandemly arranged in the BamHI E region) have proved either uniformly type 1 or uniformly type 2 at all four loci. The absence of detectable intertypic recombination in the wild probably reflects the rarity with which individual carriers, and certainly individual target cells, become coinfected with both virus types. Studying a group of human immunodeficiency virus-positive T-cell-immunocompromised patients known to be at enhanced risk of multiple EBV infections, we have isolated intertypic EBV recombinants from 2 of 40 patients analyzed. These recombinants, whose in vitro transforming capacity appeared at least equal to that of type 1 strains, carried a type 1 EBNA2 allele and type 2 EBNA3A,-3B, and -3C alleles. This was clearly demonstrable at the DNA level by PCR amplification using type-specific primer-probe combinations and was confirmed at the protein level (for EBNA2 and EBNA3C) by immunoblotting with type-specific antibodies. In one patient, the recombinant appeared to be the predominant strain, being the virus most commonly rescued by in vitro transformation both from the blood and from the throat washings on two separate occasions 20 months apart. A regular type 1 virus strain was also present in this individual, but this was not related to the recombinant since the two viruses carried type 1 EBNA2 genes with different patterns of variance from the B95.8 prototype sequence. In the other patient, recombinants were isolated on one occasion from the blood and on a separate occasion, 21 months later, from the throat; these recombinants were almost certainly related, being identical at several genomic polymorphisms and differing only in one facet of the "EBNAprint," the size of the EBNA1 protein. Three different type 1 viruses were also isolated from this patient, two of which carried EBNA2 genes with the same pattern of sequence variation from B95.8 as the recombinant; however, since this is a fairly common pattern of variance, the relationship of these viruses to the recombinant remains an open question. We infer that intertypic recombinants of EBV are not uncommon in HIV-positive T-cell-immunocompromised patients, that they arise in such individuals as a consequence of their increased frequency of mixed-type infections, and that they will prove capable of efficient transmission in the human population

HLA-A11-Restricted Epitope Polymorphism among Epstein-Barr Virus Strains in the Highly HLA-A11-Positive Chinese Population: Incidence and Immunogenicity of Variant Epitope Sequences

An individual's CD8(+)-cytotoxic-T-lymphocyte (CTL) response to Epstein-Barr virus (EBV) latent cycle antigens focuses on a small number of immunodominant epitopes often presented by just one of the available HLA class I alleles; for example, HLA-A11-positive Caucasians frequently respond to two immunodominant HLA A11 epitopes, IVTDFSVIK (IVT) and AVFDRKSDAK (AVF), within the nuclear antigen EBNA3B. Here, we reexamine the spectrum of EBV strains present in the highly HLA-A11-positive Chinese population for sequence changes in these epitopes relative to the Caucasian type 1 prototype strain B95.8. The IVT epitope was altered in 61 of 64 Chinese type 1 viruses, with four different sequence variants being observed, and the AVF epitope was altered in 46 cases with six different sequence variants; by contrast, all 10 Chinese type 2 viruses retained the prototype 2 epitope sequences. All but one of the type 1 epitope variants were poorly recognized by IVT- or AVF-specific CTLs in pulse-chase assays of peptide-mediated target cell lysis. More importantly, we screened HLA-A11-positive Chinese donors carrying viruses with known epitope mutations for evidence of epitope-specific CTL memory by enzyme-linked immunospot assays: none of the type 1 variants tested, nor the type 2 prototype, appeared to be immunogenic in vivo. The data remain consistent with the possibility that, during virus-host coevolution, pressure from the host CTL-mediated immune response has given A11 epitope-loss viruses a selective advantage