Human IL-17 and TNF-α Additively or Synergistically Regulate the Expression of Proinflammatory Genes, Coagulation-Related Genes, and Tight Junction Genes in Porcine Aortic Endothelial Cells

How Does a Porcine Herpesvirus, PCMV/PRV, Induce a Xenozoonosis

Porcine cytomegalovirus/porcine roseolovirus (PCMV/PRV), a porcine herpesvirus, has been shown to significantly reduce the survival time of porcine xenotransplants in non-human primates. The virus was detected in all the examined organs of baboons transplanted with PCMV/PRV-positive organs and it was also transmitted to the first human recipient of a pig heart, contributing to the patient's death. PCMV/PRV induces consumptive coagulopathy and thrombocytopenia in xenotransplant recipients. Initial studies in baboons revealed that the virus triggered increased release of tumor necrosis factor α (TNFα) and interleukin 6 (IL-6), along with elevated levels of tissue plasminogen activator (tPA) and plasminogen activator inhibitor 1 (PAI-1) complexes. Since there is no evidence that PCMV/PRV infects primate cells, including human cells, the virus appears to directly interact with immune and endothelial cells, disrupting cytokine signaling and coagulation pathways. The highest viral load was detected in the explanted pig heart, suggesting active replication at this site. Additionally, cells expressing PCMV/PRV proteins were identified in all the examined baboon organs, where pig cells were also found. Since PCMV/PRV affects only xenotransplant recipients and not healthy humans, this condition should be classified as a xenozoonosis. Interestingly, antibodies against human herpesvirus 6 (HHV-6) cross-react with PCMV/PRV and may contribute to protection against infection in humans. Further research is needed to uncover the molecular mechanisms underlying this xenozoonotic disease.

Claudin-2 enhances human antibody-mediated complement-dependent cytotoxicity of porcine endothelial cells by modulating antibody binding and complement activation

Background

Immune rejection represents a significant barrier to transplantation, especially in the context of xenotransplantation. Endothelial cells (ECs) derived from pigs serve as the initial barrier against the human immune system in xenotransplantation. Tight junction proteins are essential components of endothelial cell tight junctions; however, their role in xenotransplantation has been less thoroughly investigated. Claudin-2, a key tight junction protein, was investigated here for its role in human antibody-mediated complement-dependent cytotoxicity (CDC).

Methods

Using an in vitro model of human antibody-mediated CDC, we assessed the effect of Claudin-2 on porcine aortic endothelial cells (PAECs) and porcine iliac endothelial cells (PIECs). Claudin-2 expression was either knocked down or overexpressed in these cells. A flow cytometry assay was used to evaluate C3c, C9, and the C5b-9 deposition, as well as the extent of human IgM and IgG binding to PIECs. The mRNA levels of complement regulators (CD46, CD55, CD59, Factor H, Factor I) were quantified by real-time PCR.

Results

The loss of Claudin-2 protected PAECs and PIECs from human antibody-mediated CDC, while the overexpression of Claudin-2 enhanced the cytotoxicity in PAECs and PIECs within the same model. Unexpectedly, the loss or overexpression of Claudin-2 did not influence the mRNA expression levels of complement regulators (CD46, CD55, CD59, Factor H, and Factor I). Importantly, the loss of Claudin-2 significantly decreased the deposition of the C5b-9 complex, commonly referred to as the membrane attack complex (MAC), whereas the overexpression of Claudin-2 enhanced the deposition of the C5b-9 complex, indicating that Claudin-2 facilitates complement activation. Furthermore, the loss of Claudin-2 resulted in a decrease in the deposition of C3c and C9 on PIECs. Moreover, Claudin-2 enhanced human antibody binding to porcine ECs, as evidenced by increased IgG and IgM binding.

Conclusion

Our findings indicate that Claudin-2 enhances the cytotoxicity of porcine ECs through modulating antibody binding and complement activation. The deficient of Claudin-2 in genetically modified pigs is likely to protect porcine ECs and enhance xenograft survival in pig-to-human organ or tissue xenotransplantation.

Development of a diagnostic model based on glycolysis-related genes and immune infiltration in intervertebral disc degeneration

Background

The glycolytic pathway and immune response play pivotal roles in the intervertebral disc degeneration (IDD) progression. This study aimed to develop a glycolysis-related diagnostic model and analyze its relationship with the immune response to IDD.

Methods

GSE70362, GSE23130, and GSE15227 datasets were collected and merged from the Gene Expression Omnibus, and differential expression analysis was performed. Glycolysis-related differentially expressed genes (GLRDEGs) were identified, and a machine learning-based diagnostic model was constructed and validated, followed by Gene Set Enrichment Analysis (GSEA). Gene Ontology functional enrichment and Kyoto Encyclopedia of Genes and Genomes pathway enrichment analyses were performed, and mRNA-miRNA and mRNA-transcription factor (TF) interaction networks were constructed. Immune infiltration was analyzed using single-sample GSEA (ssGSEA) and cell-type identification by estimating relative subsets of RNA transcripts (CIBERSORT) algorithm between high- and low-risk groups.

Results

In the combined dataset, samples from 31 patients with IDD and 55 normal controls were analyzed, revealing differential expression of 16 GLRDEGs between the two groups. Using advanced machine learning techniques (LASSO, support vector machine, and random forest algorithms), we identified eight common GLRDEGs (PXK, EIF3D, WSB1, ZNF185, IGFBP3, CKAP4, RPL15, and, SSR1) and developed a diagnostic model, which demonstrated high accuracy in distinguishing IDD from control samples (area under the curve, 0.935). We identified 42 mRNA-miRNA and 33 mRNA-TF interaction pairs. Using the RiskScore from the diagnostic model, the combined dataset was stratified into high- and low-risk groups. SsGSEA revealed significant differences in the infiltration abundances of the four immune cell types between the groups. The CIBERSORT algorithm revealed the strongest correlation between resting natural killer (NK) cells and ZNF185 in the low-risk group and between CD8+ T cells and SSR1 in the high-risk group.

Conclusions

Our study reveals a potential interplay between glycolysis-associated genes and immune infiltration in IDD pathogenesis. These findings contribute to our understanding of IDD and may guide development of novel diagnostic markers and therapeutic interventions.

Developments in kidney xenotransplantation

The search for kidney xenografts that are appropriate for patients with end-stage renal disease has been ongoing since the beginning of the last century. The major cause of xenograft loss is hyperacute and acute rejection, and this has almost been overcome via scientific progress. The success of two pre-clinical trials of α1,3-galactosyltransferase gene-knockout porcine kidneys in brain-dead patients in 2021 triggered research enthusiasm for kidney xenotransplantation. This minireview summarizes key issues from an immunological perspective: the discovery of key xenoantigens, investigations into key co-stimulatory signal inhibition, gene-editing technology, and immune tolerance induction. Further developments in immunology, particularly immunometabolism, might help promote the long-term outcomes of kidney xenografts.