Opening the door for hepatitis C virus infection in genetically humanized mice

Low LDL cholesterol and risk of bacterial and viral infections: observational and Mendelian randomization studies

Aims

Low levels of LDL cholesterol may be associated with risk of infectious disease. We tested the hypothesis that low LDL cholesterol due to genetic variation in the LDLR, PCSK9, and HMGCR genes and a polygenic LDL cholesterol score is associated with risk of infectious diseases in the general population.

Methods and results

Using observational and Mendelian randomization designs, we examined associations of low plasma LDL cholesterol with risk of bacterial and viral infections in 119 805 individuals from the Copenhagen General Population Study/Copenhagen City Heart Study, 468 701 from the UK Biobank, and up to 376 773 from the FinnGen Research Project. Observationally, low LDL cholesterol concentrations were associated with risk of hospitalization for both bacterial and viral infections. In genetic analyses, a 1 mmol/L lower LDL cholesterol was associated with lower plasma PCSK9 {-0.55 nmol/L [95% confidence interval (CI): -1.06 to -0.05]; P = 0.03}, leucocyte count [-0.42 × 109/L (-0.61 to -0.24); P < 0.001], and high-sensitivity C-reactive protein [-0.44 mg/L (-0.79 to -0.09); P = 0.014]. Using an LDLR, HMGCR, and PCSK9 score, a 1 mmol/L lower LDL cholesterol was associated with risk ratios of 0.91 (95% CI: 0.86-0.97; P = 0.002) for unspecified bacterial infection, of 0.92 (0.87-0.97; P = 0.004) for diarrhoeal disease, and of 1.15 (1.03-1.29; P = 0.012) for unspecified viral infections and 1.64 (1.13-2.39; P = 0.009) for HIV/AIDS. Using a polygenic LDL cholesterol score largely showed similar results and in addition a lower risk of 0.85 (0.76-0.96; P = 0.006) for bacterial pneumonia and 0.91 (0.82-0.99; P = 0.035) for sepsis.

Conclusion

Genetically low LDL cholesterol concentrations were associated with lower concentration of markers of inflammation; lower risk of hospitalization for unspecified bacterial infections, infectious diarrhoeal diseases, bacterial pneumonia, and sepsis; and higher risk of viral infections and HIV/AIDS.

Viral Interactions with Adaptor-Protein Complexes: A Ubiquitous Trait among Viral Species

Numerous viruses hijack cellular protein trafficking pathways to mediate cell entry or to rearrange membrane structures thereby promoting viral replication and antagonizing the immune response. Adaptor protein complexes (AP), which mediate protein sorting in endocytic and secretory transport pathways, are one of the conserved viral targets with many viruses possessing AP-interacting motifs. We present here different mechanisms of viral interference with AP complexes and the functional consequences that allow for efficient viral propagation and evasion of host immune defense. The ubiquity of this phenomenon is evidenced by the fact that there are representatives for AP interference in all major viral families, covered in this review. The best described examples are interactions of human immunodeficiency virus and human herpesviruses with AP complexes. Several other viruses, like Ebola, Nipah, and SARS-CoV-2, are pointed out as high priority disease-causative agents supporting the need for deeper understanding of virus-AP interplay which can be exploited in the design of novel antiviral therapies.

Host specificity of bacterial pathogens

Most pathogens are able to infect multiple hosts but some are highly adapted to a single-host species. A detailed understanding of the basis of host specificity can provide important insights into molecular pathogenesis, the evolution of pathogenic microbes, and the potential for pathogens to cross the species barrier to infect new hosts. Comparative genomics and the development of humanized mouse models have provided important new tools with which to explore the basis of generalism and specialism. This review will examine host specificity of bacterial pathogens with a focus on generalist and specialist serovars of Salmonella enterica.

Hepatitis C virus, cholesterol and lipoproteins--impact for the viral life cycle and pathogenesis of liver disease

Hepatitis C virus (HCV) is a leading cause of chronic liver disease, including chronic hepatitis, fibrosis, cirrhosis, and hepatocellular carcinoma. Hepatitis C infection associates with lipid and lipoprotein metabolism disorders such as hepatic steatosis, hypobetalipoproteinemia, and hypocholesterolemia. Furthermore, virus production is dependent on hepatic very-low-density lipoprotein (VLDL) assembly, and circulating virions are physically associated with lipoproteins in complexes termed lipoviral particles. Evidence has indicated several functional roles for the formation of these complexes, including co-opting of lipoprotein receptors for attachment and entry, concealing epitopes to facilitate immune escape, and hijacking host factors for HCV maturation and secretion. Here, we review the evidence surrounding pathogenesis of the hepatitis C infection regarding lipoprotein engagement, cholesterol and triglyceride regulation, and the molecular mechanisms underlying these effects.