Factors Associated with Mortality and Graft Failure in Liver Transplants: A Hierarchical Approach

Background

Liver transplantation has received increased attention in the medical field since the 1980s following the introduction of new immunosuppressants and improved surgical techniques. Currently, transplantation is the treatment of choice for patients with end-stage liver disease, and it has been expanded for other indications. Liver transplantation outcomes depend on donor factors, operating conditions, and the disease stage of the recipient. A retrospective cohort was studied to identify mortality and graft failure rates and their associated factors. All adult liver transplants performed in the state of São Paulo, Brazil, between 2006 and 2012 were studied.

Methods and Findings

A hierarchical Poisson multiple regression model was used to analyze factors related to mortality and graft failure in liver transplants. A total of 2,666 patients, 18 years or older, (1,482 males; 1,184 females) were investigated. Outcome variables included mortality and graft failure rates, which were grouped into a single binary variable called negative outcome rate. Additionally, donor clinical, laboratory, intensive care, and organ characteristics and recipient clinical data were analyzed. The mortality rate was 16.2 per 100 person-years (py) (95% CI: 15.1–17.3), and the graft failure rate was 1.8 per 100 py (95% CI: 1.5–2.2). Thus, the negative outcome rate was 18.0 per 100 py (95% CI: 16.9–19.2). The best risk model demonstrated that recipient creatinine ≥ 2.11 mg/dl [RR = 1.80 (95% CI: 1.56–2.08)], total bilirubin ≥ 2.11 mg/dl [RR = 1.48 (95% CI: 1.27–1.72)], Na⁺ ≥ 141.01 mg/dl [RR = 1.70 (95% CI: 1.47–1.97)], RNI ≥ 2.71 [RR = 1.64 (95% CI: 1.41–1.90)], body surface ≥ 1.98 [RR = 0.81 (95% CI: 0.68–0.97)] and donor age ≥ 54 years [RR = 1.28 (95% CI: 1.11–1.48)], male gender [RR = 1.19(95% CI: 1.03–1.37)], dobutamine use [RR = 0.54 (95% CI: 0.36–0.82)] and intubation ≥ 6 days [RR = 1.16 (95% CI: 1.10–1.34)] affected the negative outcome rate.

Conclusions

The current study confirms that both donor and recipient characteristics must be considered in post-transplant outcomes and prognostic scores. Our data demonstrated that recipient characteristics have a greater impact on post-transplant outcomes than donor characteristics. This new concept makes liver transplant teams to rethink about the limits in a MELD allocation system, with many teams competing with each other. The results suggest that although we have some concerns about the donors features, the recipient factors were heaviest predictors for bad outcomes.     

Intranasal gene therapy to prevent infection by SARS-CoV-2 variants

SARS-CoV-2 variants have emerged with enhanced pathogenicity and transmissibility, and escape from pre-existing immunity, suggesting first-generation vaccines and monoclonal antibodies may now be less effective. Here we present an approach for preventing clinical sequelae and the spread of SARS-CoV-2 variants. First, we affinity matured an angiotensin-converting enzyme 2 (ACE2) decoy protein, achieving 1000-fold binding improvements that extend across a wide range of SARS-CoV-2 variants and distantly related, ACE2-dependent coronaviruses. Next, we demonstrated the expression of this decoy in proximal airway when delivered via intranasal administration of an AAV vector. This intervention significantly diminished clinical and pathologic consequences of SARS-CoV-2 challenge in a mouse model and achieved therapeutic levels of decoy expression at the surface of proximal airways when delivered intranasally to nonhuman primates. Importantly, this long-lasting, passive protection approach is applicable in vulnerable populations such as the elderly and immune-compromised that do not respond well to traditional vaccination. This approach could be useful in combating COVID-19 surges caused by SARS-CoV-2 variants and should be considered as a countermeasure to future pandemics caused by one of the many pre-emergent, ACE2-dependent CoVs that are poised for zoonosis.     

Recognition of Smac-mimetic compounds by the BIR domain of cIAP1

Inhibitor of apoptosis proteins (IAPs) are negative regulators of apoptosis. As IAPs are overexpressed in many tumors, where they confer chemoresistance, small molecules inactivating IAPs have been proposed as anticancer agents. Accordingly, a number of IAP-binding pro-apoptotic compounds that mimic the sequence corresponding to the N-terminal tetrapeptide of Smac/DIABLO, the natural endogenous IAPs inhibitor, have been developed. Here, we report the crystal structures of the BIR3 domain of cIAP1 in complex with Smac037, a Smac-mimetic known to bind potently to the XIAP-BIR3 domain and to induce degradation of cIAP1, and in complex with the novel Smac-mimetic compound Smac066. Thermal stability and fluorescence polarization assays show the stabilizing effect and the high affinity of both Smac037 and Smac066 for cIAP1- and cIAP2-BIR3 domains.     

Probing the active site of the sugar isomerase domain from E. coli arabinose-5-phosphate isomerase via X-ray crystallography

Lipopolysaccharide (LPS) biosynthesis represents an underexploited target pathway for novel antimicrobial development to combat the emergence of multidrug‐resistant bacteria. A key player in LPS synthesis is the enzyme D ‐arabinose‐5‐phosphate isomerase (API), which catalyzes the reversible isomerization of D ‐ribulose‐5‐phosphate to D ‐arabinose‐5‐phosphate, a precursor of 3‐deoxy‐D ‐manno‐octulosonate that is an essential residue of the LPS inner core. API is composed of two main domains: an N‐terminal sugar isomerase domain (SIS) and a pair of cystathionine‐β‐synthase domains of unknown function. As the three‐dimensional structure of an enzyme is a prerequisite for the rational development of novel inhibitors, we present here the crystal structure of the SIS domain of a catalytic mutant (K59A) of E. coli D ‐arabinose‐5‐phosphate isomerase at 2.6‐Å resolution. Our structural analyses and comparisons made with other SIS domains highlight several potentially important active site residues. In particular, the crystal structure allowed us to identify a previously unpredicted His residue (H88) located at the mouth of the active site cavity as a possible catalytic residue. On the basis of such structural data, subsequently supported by biochemical and mutational experiments, we confirm the catalytic role of H88, which appears to be a generally conserved residue among two‐domain isomerases.     

Protein folding and chain collapse

It is currently assumed that the folded structure of a globular protein is controlled in a highly deterministic way by its amino acid sequence. We show here that a very different although not necessarily contrasting viewpoint can be adopted. From statistical treatment of x-ray results, we suggest that the folding pattern essentially follows the collapse to be expected on statistical-mechanical grounds for an ideal chain effectively experiencing self-attraction and comprising identical units, whose conformational properties are obtained as an average over the actual amino acid units. The local details of folding of each protein, obviously dictated byits amino acid sequence, can be regarded as statistical fluctuations. We consider 31 globular fragments belonging to 21 different water-soluble, nonmembrane proteins. By the theory of chain collapse proposed by two of us [G. Allegra and F. Ganazzoli (1985) J. Chem. Phys. 83 , 397], all the average intramolecular distances may be obtained. Accordingly, first an average plot of the mean-square distances between kth neighboring amino acid units is constructed, starting from the observed crystallographic coordinates. Then the plot is basically reproduced with a wormlike chain model undergoing collapse as a result of intramolecular attractive forces. Agreement is especially good for short amino acid sequences (k ? 30), in which case the statistical sampling is more accurate, enabling us to determine the model parameters. The resulting mean-square radius of gyration is also in good agreement with the experimental average, whereas the unperturbed characteristic ratio is roughly consistent with results from conformational calculations by W. L. Mattice [(1977) Macromolecules 10 , 516], based on the rotational isomeric state approach.     

Central memory Vgamma9Vdelta2 T lymphocytes primed and expanded by bacillus Calmette-Guérin-infected dendritic cells kill mycobacterial-infected monocytes

In humans, innate immune recognition of mycobacteria, including Mycobacterium tuberculosis and bacillus Calmette-Guérin (BCG), is a feature of cells as dendritic cells (DC) and gammadelta T cells. In this study, we show that BCG infection of human monocyte-derived DC induces a rapid activation of Vgamma9Vdelta2 T cells (the major subset of gammadelta T cell pool in human peripheral blood). Indeed, in the presence of BCG-infected DC, Vgamma9Vdelta2 T cells increase both their expression of CD69 and CD25 and the production of TNF-alpha and IFN-gamma, in contrast to DC treated with Vgamma9Vdelta2 T cell-specific Ags. Without further exogenous stimuli, BCG-infected DC expand a functionally cytotoxic central memory Vgamma9Vdelta2 T cell population. This subset does not display lymph node homing receptors, but express a high amount of perforin. They are highly efficient in the killing of mycobacterial-infected primary monocytes or human monocytic THP-1 cells preserving the viability of cocultured, infected DC. This study provides further evidences about the complex relationship between important players of innate immunity and suggests an immunoregulatory role of Vgamma9Vdelta2 T cells in the control of mycobacterial infection.