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Background: Reconstitution of cytomegalovirus-specific CD3+CD8+ T cells (CMV-CTLs) after allogeneic hematopoietic stem cell transplantation (HSCT) is necessary to bring cytomegalovirus (CMV) reactivation under control. However, the parameters determining protective CMV-CTL reconstitution remain unclear to date.
Design and Methods: In a prospective tri-center study, CMV-CTL reconstitution was analyzed in the peripheral blood from 278 patients during the year following HSCT using 7 commercially available tetrameric HLA-CMV epitope complexes. All patients included could be monitored with at least CMV-specific tetramer.
Results: CMV-CTL reconstitution was detected in 198 patients (71%) after allogeneic HSCT. Most importantly, reconstitution with 1 CMV-CTL per µl blood between day +50 and day +75 post-HSCT discriminated between patients with and without CMV reactivation in the R+/D+ patient group, independent of the CMV-epitope recognized. In addition, CMV-CTLs expanded more daramtaically in patients experiencing only one CMV-reactivation than those without or those with multiple CMV reactivations. Monitoring using at least 2 tetramers was possible in 63% (n = 176) of the patients. The combinations of particular HLA molecules influenced the numbers of CMV-CTLs detected. The highest CMV-CTL count obtained for an individual tetramer also changed over time in 11% of these patients (n = 19) resulting in higher levels of HLA-B*0801 (IE-1) recognizing CMV-CTLs in 14 patients.
Conclusions: Our results indicate that 1 CMV-CTL per µl blood between day +50 to +75 marks the beginning of an immune response against CMV in the R+/D+ group. Detection of CMV-CTL expansion thereafter indicates successful resolution of the CMV reactivation. Thus, sequential monitoring of CMV-CTL reconstitution can be used to predict patients at risk for recurrent CMV reactivation.
Background and Purpose: The cyclic nucleotides cAMP and cGMP are ubiquitous second messengers regulating numerous biological processes. Malfunctional cNMP signalling is linked to diseases and thus is an important target in pharmaceutical research. The existing optogenetic toolbox in Caenorhabditis elegans is restricted to soluble adenylyl cyclases, the membrane-bound Blastocladiella emersonii CyclOp and hyperpolarizing rhodopsins; yet missing are membrane-bound photoactivatable adenylyl cyclases and hyperpolarizers based on K+ currents.
Experimental Approach: For the characterization of photoactivatable nucleotidyl cyclases, we expressed the proteins alone or in combination with cyclic nucleotide-gated channels in muscle cells and cholinergic motor neurons. To investigate the extent of optogenetic cNMP production and the ability of the systems to depolarize or hyperpolarize cells, we performed behavioural analyses, measured cNMP content in vitro, and compared in vivo expression levels.
Key Results: We implemented Catenaria CyclOp as a new tool for cGMP production, allowing fine-control of cGMP levels. We established photoactivatable membrane-bound adenylyl cyclases, based on mutated versions (“A-2x”) of Blastocladiella and Catenaria (“Be,” “Ca”) CyclOp, as N-terminal YFP fusions, enabling more efficient and specific cAMP signalling compared to soluble bPAC, despite lower overall cAMP production. For hyperpolarization of excitable cells by two-component optogenetics, we introduced the cAMP-gated K+-channel SthK from Spirochaeta thermophila and combined it with bPAC, BeCyclOp(A-2x), or YFP-BeCyclOp(A-2x). As an alternative, we implemented the B. emersonii cGMP-gated K+-channel BeCNG1 together with BeCyclOp.
Conclusion and Implications: We established a comprehensive suite of optogenetic tools for cNMP manipulation, applicable in many cell types, including sensory neurons, and for potent hyperpolarization.
The genetic make-up of an individual contributes to the susceptibility and response to viral infection. Although environmental, clinical and social factors have a role in the chance of exposure to SARS-CoV-2 and the severity of COVID-191,2, host genetics may also be important. Identifying host-specific genetic factors may reveal biological mechanisms of therapeutic relevance and clarify causal relationships of modifiable environmental risk factors for SARS-CoV-2 infection and outcomes. We formed a global network of researchers to investigate the role of human genetics in SARS-CoV-2 infection and COVID-19 severity. Here we describe the results of three genome-wide association meta-analyses that consist of up to 49,562 patients with COVID-19 from 46 studies across 19 countries. We report 13 genome-wide significant loci that are associated with SARS-CoV-2 infection or severe manifestations of COVID-19. Several of these loci correspond to previously documented associations to lung or autoimmune and inflammatory diseases3,4,5,6,7. They also represent potentially actionable mechanisms in response to infection. Mendelian randomization analyses support a causal role for smoking and body-mass index for severe COVID-19 although not for type II diabetes. The identification of novel host genetic factors associated with COVID-19 was made possible by the community of human genetics researchers coming together to prioritize the sharing of data, results, resources and analytical frameworks. This working model of international collaboration underscores what is possible for future genetic discoveries in emerging pandemics, or indeed for any complex human disease.