Finding a Needle in the Virus Metagenome Haystack - Micro-Metagenome Analysis Captures a Snapshot of the Diversity of a Bacteriophage Armoire

Viruses are ubiquitous in the oceans and critical components of marine microbial communities, regulating nutrient transfer to higher trophic levels or to the dissolved organic pool through lysis of host cells. Hydrothermal vent systems are oases of biological activity in the deep oceans, for which knowledge of biodiversity and its impact on global ocean biogeochemical cycling is still in its infancy. In order to gain biological insight into viral communities present in hydrothermal vent systems, we developed a method based on deep-sequencing of pulsed field gel electrophoretic bands representing key viral fractions present in seawater within and surrounding a hydrothermal plume derived from Loki's Castle vent field at the Arctic Mid-Ocean Ridge. The reduction in virus community complexity afforded by this novel approach enabled the near-complete reconstruction of a lambda-like phage genome from the virus fraction of the plume. Phylogenetic examination of distinct gene regions in this lambdoid phage genome unveiled diversity at loci encoding superinfection exclusion- and integrase-like proteins. This suggests the importance of fine-tuning lyosgenic conversion as a viral survival strategy, and provides insights into the nature of host-virus and virus-virus interactions, within hydrothermal plumes. By reducing the complexity of the viral community through targeted sequencing of prominent dsDNA viral fractions, this method has selectively mimicked virus dominance approaching that hitherto achieved only through culturing, thus enabling bioinformatic analysis to locate a lambdoid viral “needle" within the greater viral community “haystack". Such targeted analyses have great potential for accelerating the extraction of biological knowledge from diverse and poorly understood environmental viral communities

High-resolution histocompatibility testing of a group of sixteen B44-positive, ABDR serologically matched unrelated donor-recipient pairs. Analysis of serologically undisclosed incompatibilities by cellular techniques, isoelectrofocusing, and HLA oligotyping

We have characterized HLA incompatibilities in a group of 16 B44-positive patients who were serologically ABDR matched with their 23 (unrelated) potential bone marrow donors. After analysis with a combination of cellular techniques, IEF for HLA-A/B and oligotyping for class II and HLA-B44, 44% of the patients revealed one or more HLA incompatibility with at least one of their potential donors. CTL activity was detected in 12 of the 22 combinations tested. CTL incompatibility occurred more frequently in DR subtype-mismatched combinations, but CTL reactivity was always directed against class I. To characterize these incompatibilities between matched unrelated individuals, we analyzed the specificity of T-cell clones from seven primary CTL cultures. In three combinations, CTL reactivity was directed against a subtype of B44. In two combinations, the CTL reactivity was directed against a non-B44 class I subtype. In two of seven combinations, the CTLs recognized an antigen that, though unconditionally associated with B4403, was expressed by 60% of the B4403+ cells only. Because all 12 of these B4403+ targets recognized could be typed for one HLA-C allele only (Cwl-Cw8), we believe that this alloreactivity might be directed against a serologically undefined Cw antigen

Crossing borders to facilitate live donor kidney transplantation: the Czech-Austrian kidney paired donation program – a retrospective study

Kidney paired donation (KPD) is a valuable tool to overcome immunological barriers in living donor transplantation. While small national registries encounter difficulties in finding compatible matches, multi-national KPD may be a useful strategy to facilitate transplantation. The Czech (Prague) and Austrian (Vienna) KPD programs, both initiated in 2011, were merged in 2015. A bi-national algorithm allowed for ABO- and low-level HLA antibody-incompatible exchanges, including the option of altruistic donor-initiated domino chains. Between 2011 and 2019, 222 recipients and their incompatible donors were registered. Of those, 95.7% (Prague) and 67.9% (Vienna) entered into KPD registries, and 81 patients received a transplant (95% 3-year graft survival). Inclusion of ABO-incompatible pairs in the Czech program contributed to higher KPD transplant rates (42.6% vs. 23.6% in Austria). After 2015 (11 bi-national match runs), the median pool size increased to 18 pairs, yielding 33 transplants (8 via cross-border exchanges). While matching rates doubled in Austria (from 9.1% to 18.8%), rates decreased in the Czech program, partly due to implementation of more stringent HLA antibody thresholds. Our results demonstrate the feasibility of merging small national KPD programs to increase pool sizes and may encourage the implementation of multi-national registries to expand the full potential of KPD