Proximal-type epithelioid sarcoma: case report of an unusual presentation.

Epithelioid sarcoma, first described by Enzinger in 1970, classically presents in young adults and usually arises in the distal extremities. The proximal-type variant, first described in 1997 as a rare aggressive form of sarcoma, usually arises more proximally. It carries a higher mortality rate than classical limb epithelioid sarcoma and is often resistant to multimodal treatment. We report the case of a 27-year old male who had a delayed diagnosis of proximal-type epithelioid sarcoma of the forearm. This was originally thought to be a necrotising soft tissue infection and was unfortunately metastatic at the time of eventual diagnosis. The clinical and histopathological features of this challenging tumour are discussed and the relevant literature is reviewed.

Genomic deletion marking an emerging subclone of Francisella tularensis subsp. holarctica in France and the Iberian Peninsula.

Francisella tularensis subsp. holarctica is widely disseminated in North America and the boreal and temperate regions of the Eurasian continent. Comparative genomic analyses identified a 1.59-kb genomic deletion specific to F. tularensis subsp. holarctica isolates from Spain and France. Phylogenetic analysis of strains carrying this deletion by multiple-locus variable-number tandem repeat analysis showed that the strains comprise a highly related set of genotypes, implying that these strains were recently introduced or recently emerged by clonal expansion in France and the Iberian Peninsula.

Are paediatric burns more common in asylum seekers? An analysis of paediatric burn admissions.

The number of asylum seekers in Ireland has increased dramatically over the last 10 years. Based on our impression that the number of children admitted to our burn unit was disproportionately represented by children of asylum seekers we performed an audit to establish (1) what proportion of admissions are from this subgroup and (2) the characteristics of their burns. All paediatric burn admissions from May 2003 to April 2004 were reviewed. Data collected from a retrospective chart review included patient demographics and details of the burn injuries. The National Census of 2002 and the Office of the Refugee Applications Commissioner were consulted for population statistics. Total burn admissions for the period were 126: Irish nationals (n=107), non-national residents (n=2), asylum seekers (n=14) and patients of unknown asylum status (n=3, excluded from study). In the asylum seeker group, the median age was 18.6 months (range 10 months-5.3 years) with the majority less than 2 years (n=11). All burns occurred in the domestic setting. Scalds accounted for 13 cases, one contact burn occurred from a hot grill. The median total body surface area burned was 5.7% (range 1.5-26%). The National Census of 2002 recorded a population of 3,917,203. With less than 12,000 asylum seekers in the country, they comprise only approximately 0.3% of the population yet they account for 11.4% of the burn patients admitted to our unit, p<0.0001. Children of asylum seekers are over-represented in our series of paediatric admissions for burns and are more likely than Irish children to sustain a burn at a younger age and in the domestic setting. This may indicate an increased risk of injury and warrants further investigation.

Detection of West Nile virus in mosquitoes by RT-PCR.

A reverse transcriptase-polymerase chain reaction (RT-PCR) assay employing <> detection technology was developed to identify West Nile virus in experimentally infected mosquitoes. The specificity of the assay was evaluated with the following viruses: eastern equine encephalitis, Ilheus, West Nile and yellow fever viruses. The limits of detection were determined using West Nile viral RNA extracted from serial dilutions of virus culture in infected mosquitoes. Limit of detection was 5 PFU from extracted mosquitoes. We were able to detect the presence of one infected mosquito in a pool of 50 repeatedly. When the RT-PCR was used with coded samples of intrathoracically-infected and uninfected mosquitoes, the assay detected the virus in all infected mosquitoes. Analytic sensitivity and specificity were 100%. This assay offers an efficient and rapid method of identifying West Nile virus in infected mosquitoes or cell culture.

Reduced nuclear import of human immunodeficiency virus type 1 preintegration complexes in the presence of a prototypic nuclear targeting signal.

Nuclear import of the retroviral preintegration complex and integration of retroviral with host cell DNA are essential steps for completion of the virus life cycle. The preintegration complex of the lentivirus human immunodeficiency virus type 1 (HIV-1) displays karyophilic properties and, as a consequence, is rapidly directed to the host cell nucleus by an energy-dependent transport pathway. The karyophilic properties of nuclear proteins are governed by a nuclear localization sequence, the targeting function of which can be inhibited in the presence of excess targeting signals. Here we present evidence that the nuclear import of a large karyophile--the preintegration complex of HIV-1--is inhibited in the presence of a prototypic nuclear targeting signal of simian virus 40 T antigen. This points to a novel strategy which prevents establishment of the provirus by interrupting nuclear localization of HIV-1 DNA.

A nuclear localization signal within HIV-1 matrix protein that governs infection of non-dividing cells.

Permissiveness of the host cell to productive infection by oncoretroviruses is cell-cycle dependent, and nuclear localization of viral nucleoprotein preintegration complexes will occur only after cells have passed through mitosis. In contrast, establishment of an integrated provirus after infection by the lentivirus HIV-1 is independent of host cell proliferation. The ability of HIV-1 to replicate in non-dividing cells is partly accounted for by the karyophilic properties of the viral preintegration complex which, after virus infection, is actively transported to the host cell nucleus. Here we report that the gag matrix protein of HIV-1 contains a nuclear localization sequence which, when conjugated to a heterologous protein, directs its nuclear import. In addition, HIV-1 mutants containing amino-acid substitutions in this nuclear localization signal integrate and replicate within dividing but not growth-arrested cells, and thus display a phenotype more representative of an oncoretrovirus.

Active nuclear import of human immunodeficiency virus type 1 preintegration complexes.

After cell infection by the human immunodeficiency virus type 1 (HIV-1), nascent viral DNA in the form of a high molecular weight nucleoprotein preintegration complex must be transported to the nucleus of the host cell prior to integration of viral DNA with the host genome. The mechanism used by retroviruses for nuclear targeting of preintegration complexes and dependence on cell division has not been established. Our studies show that, after infection, the preintegration complex of HIV-1 was rapidly transported to the nucleus of the host cell by a process that required ATP but was independent of cell division. Functional HIV-1 integrase, an essential component of the preintegration complex, was not required for nuclear import of these complexes. The ability of HIV-1 to use host cell active transport processes for nuclear import of the viral preintegration complex obviates the requirement for host cell division in establishment of the integrated provirus. These findings are pertinent to our understanding of early events in the life cycle of HIV-1 and to the mode of HIV-1 replication in terminally differentiated nondividing cells such as macrophages (monocytes, tissue macrophages, follicular dendritic cells, and microglial cells).

Quiescent T lymphocytes as an inducible virus reservoir in HIV-1 infection.

To better understand the basis for human immunodeficiency virus type 1 (HIV-1) persistence and latency, the form in which viral DNA exists in the peripheral T lymphocyte reservoir of infected individuals was investigated. In asymptomatic individuals, HIV-1 was harbored predominantly as full-length, unintegrated complementary DNA. These extrachromosomal DNA forms retained the ability to integrate upon T cell activation in vitro. In patients with acquired immunodeficiency syndrome (AIDS), there was an increase in integrated relative to extrachromosomal DNA forms. By analysis of DNA from patient lymphocyte subpopulations depleted of human lymphocyte antigen-Dr receptor-positive cells, quiescent T cells were identified as the source of extrachromosomal HIV-1 DNA. Thus quiescent T lymphocytes may be a major and inducible HIV-1 reservoir in infected individuals.

Posttranslational modifications within the HIV-1 envelope glycoprotein which restrict virus assembly and CD4-dependent infection.

Alterations in two highly conserved N-linked glycosylation sites within the gp120 envelope glycoprotein of human immunodeficiency virus type I (HIV-1) implicated in the phenotype of a noncytopathic HIV-1 variant were introduced independently and in combination into a cytopathic, infectious HIV-1 clone by site-specific mutagenesis. Neither mutation affected the synthesis of HIV-1 envelope glycoproteins. However, one of the mutations restricted the ability of HIV-1 envelope to localize on the cell membrane and thus markedly impaired virus assembly. The HIV-1 assembly defect could be overcome in trans if site-specific mutants were packaged in HeLa cells constitutively producing wild-type HIV-1 envelope glycoprotein. In addition to inefficient virus assembly, this mutation impaired the ability of the virus to infect CD4+ T cells, but did not affect CD4-independent infection of muscle cells. These results suggest additional functions of posttranslational modification in virus replication (i.e., envelope glycoprotein transport). Given that such modifications can restrict CD4-mediated uptake without affecting CD4-independent uptake, variations in posttranslational env processing between different HIV-1 genotypes may affect virus tropism in vivo.

HIV-1 replication is controlled at the level of T cell activation and proviral integration.

During progression of the Acquired Immune Deficiency Syndrome (AIDS), the human immunodeficiency virus type 1 (HIV-1) is harbored in CD4+ T cells, which act as the primary reservoir for the virus. In vitro, HIV-1 requires activated T cells for a productive infection; however, in vivo, the number of circulating T cells in the activated state that are potential targets for HIV-1 infection is low. We have investigated the ability of HIV-1 to infect resting T cells, and the consequences of such an infection. T cell activation was not required for HIV-1 infection; however, viral DNA was unable to integrate in resting T cells and was maintained extrachromosomally. Subsequent T cell activation allowed integration of extrachromosomal forms and led to a productive viral life cycle. Extrachromosomal forms of viral DNA were found to persist for several weeks after infection of resting T cells and, following T cell activation, these forms maintained their ability to integrate and act as a template for infectious virus. Several lines of evidence, including temporal analysis of HIV-1 replication and analysis of an HIV-1 integrase deletion mutant, indicated that extra-chromosomal HIV-1 DNA genomes were transcriptionally active. These results are compatible with a model whereby HIV-1 can persist in a non-productive extra-chromosomal state in resting T cells until subsequent antigen-induced or mitogen-induced T cell activation, virus integration and release. Thus agents that induce T cell activation may control the rate of HIV-1 replication and spread during AIDS progression.