Contribution of the Epstein Barr virus to the molecular pathogenesis of Hodgkin lymphoma

Although the morphology of the pathognomonic Reed-Sternberg cells of Hodgkin lymphoma (HL) was described over a century ago, it was not until recently that their origin from B lymphocytes was recognised. The demonstration that a proportion of cases of HL harbour the Epstein-Barr virus (EBV) and that its genome is monoclonal in these tumours suggests that the virus contributes to the development of HL in some cases. This review summarises current knowledge of the pathogenesis of HL with particular emphasis on the association with EBV.

Gene expression profiling identifies different sub-types of retinoblastoma

Background:

Mutation of the RB1 gene is necessary but not sufficient for the development of retinoblastoma. The nature of events occurring subsequent to RB1 mutation is unclear, as is the retinal cell-of-origin of this tumour.

Methods:

Gene expression profiling of 21 retinoblastomas was carried out to identify genetic events that contribute to tumorigenesis and to obtain information about tumour histogenesis.

Results:

Expression analysis showed a clear separation of retinoblastomas into two groups. Group 1 retinoblastomas express genes associated with a range of different retinal cell types, suggesting derivation from a retinal progenitor cell type. Recurrent chromosomal alterations typical of retinoblastoma, for example, chromosome 1q and 6p gain and 16q loss were also a feature of this group, and clinically they were characterised by an invasive pattern of tumour growth. In contrast, group 2 retinoblastomas were found to retain many characteristics of cone photoreceptor cells and appear to exploit the high metabolic capacity of this cell type in order to promote tumour proliferation.

Conclusion:

Retinoblastoma is a heterogeneous tumour with variable biology and clinical characteristics.

The chaperonins: perspectives from the Archaea

Heat-shock protein (Hsp) 60 chaperones are almost ubiquitous and almost always essential. They can be divided on the basis of sequence homology into two broad types: group I (found in bacteria, mitochondria and chloroplasts) and group II (found in Archaea and the eukaryotic cytosol). Of the two, the group I chaperones are the better understood. Data on their structure, mechanism of action and cellular role will be briefly presented. The group II chaperones are less well studied. In eukaryotes they form large complexes with 8-fold symmetry containing eight different subunits, all of which are essential. They appear to have a major role in the folding of actin and tubulin, although they may also act on other substrates. No crystal structures are available for these complexes. The situation in the Archaea is simpler, with organisms containing between one and three genes for these chaperones. A 2.6 A structure exists for one archaeal group II chaperone complex. Some progress has been made in defining the reaction cycle of the archaeal group II chaperones and this has shown that they have some properties distinct from the group I chaperones. To date, the in vivo role and importance of the archaeal group II Hsp60 chaperones has not been determined. We have now shown that in the halophilic archaeon Haloferax volcanii not all the genes for these proteins are essential. Further analysis of these proteins in the Archaea should be very productive in yielding more information about these important chaperones and their cellular functions.

A protracted iGAS outbreak in a long-term care facility 2014-2015: control measures and the use of whole-genome sequencing

BACKGROUND

In 2014, two residents of a long-term care facility (LTCF) developed invasive group A streptococcal (iGAS) infections with identical typing (emm 11), resulting in one death. The second resident recovered but had a subsequent episode of emm 11 iGAS infection 10 months later. This second episode was linked to a third case, within 12 days, leading to a further outbreak investigation.

AIM

To combine different techniques to establish whether this was a protracted outbreak, understand transmission pathways and inform appropriate control measures.

METHODS

Following a routine response to the first cluster, the second investigation included a care record review. This informed network analysis of case interactions with staff and visitors during 10 days prior to infection. These data were combined with post-outbreak whole-genome sequencing (WGS) using isolates from cases, and staff and resident screening (44 GAS isolates: 11 outbreak-related and 33 sporadic isolates).

FINDINGS

Two of the three confirmed iGAS cases died (one suffered two episodes). All iGAS cases, and six non-invasive isolates from 2015, were emm 11 (monophylogenetic WGS clade). Network analysis highlighted only indirect contact through staff-visitor interactions between iGAS cases in 2015. This suggested a common source and transmission propagation through carriage and/or environmental contamination over an 11-month period.

CONCLUSIONS

This outbreak highlighted benefits of staff/resident screening and typing as part of routine response. Network analysis and highly discriminatory WGS clarified the protracted nature of the outbreak, supporting findings of hygiene and infection control issues and adding to our understanding of the epidemiology.