Host Genetics of Cytomegalovirus Pathogenesis

Abstract

Human cytomegalovirus (HCMV) is a ubiquitous herpes virus (human herpes virus 5) with the highest morbidity and mortality rates compared to other herpes viruses. Risk groups include very young, elderly, transplant recipient, and immunocompromised individuals. HCMV may cause retinitis, encephalitis, hepatitis, esophagitis, colitis, pneumonia, neonatal infection sequelae, inflammatory, and age-related diseases. With an arsenal of genes in its large genome dedicated to host immune evasion, HCMV can block intrinsic cellular defenses and interfere with cellular immune responses. HCMV also encodes chemokines, chemokine receptors, and cytokines. Therefore, genes involved in human viral defense mechanisms and those encoding proteins targeted by the CMV proteins are candidates for host control of CMV infection and reactivation. Although still few in number, host genetic studies are producing valuable insights into biological processes involved in HCMV pathogenesis and HCMV-related diseases. For example, genetic variants in the immunoglobulin GM light chain can influence the antibody responsiveness to CMV glycoprotein B and modify risk of HCMV-related diseases. Moreover, CMV infection following organ transplantation has been associated with variants in genes encoding toll-like receptors (TLRs), programmed death-1 ( PD-1 ), and interleukin-12p40 ( IL-12B ). A KIR haplotype (2DS4+) is proposed to be protective for CMV activation among hematopoietic stem cell transplant patients. Polymorphisms in the interferon lambda 3/4 ( IFNL3/4 ) region are shown to influence susceptibility to CMV replication among solid organ transplant patients. Interestingly, the IFNL3/4 region is also associated with AIDS-related CMV retinitis susceptibility in HIV-infected patients. Likewise, interleukin-10 receptor 1 ( IL-10R1 ) variants are shown to influence CMV retinitis development in patients with AIDS. Results from genome-wide association studies suggest a possible role for microtubule network and retinol metabolism in anti-CMV antibody response. Nevertheless, further genetic epidemiological studies with large cohorts, functional studies on the numerous HCMV genes, and immune response to chronic and latent states of infection that contribute to HCMV persistence are clearly necessary to elucidate the genetic mechanisms of CMV infection, reactivation, and pathogenesis.

Herpesviral Latency—Common Themes

“…Similarly, also in the case of HCMV the role of host genetics in immune response to the virus was revealed and a large collection of associated genes was identified eg. TLRs, NKG2D, PD-1, IFNG, IL-6 just to name a few (reviewed in [262]). The clinical course of HSV-1 infection can be modified by MHC class I allotypes (B*18, C*15, and the group of alleles encoding A19), the high-affinity receptor/ligand pair KIR2DL2/HLA-C1, and the CD16A-158V/F dimorphism.…”

The Interferon-Gamma +874 A/T Polymorphism Is Not Associated With CMV Infection After Kidney Transplantation

“…In order to clarify the implications of the virus on transplant outcome, the genetic risk factors of CMV infection have been considered. Thus, some polymorphisms located in genes involved in immune response have been studied (22)(23)(24)(25), including the interferon gamma (IFNG) gene (26,27). IFN-γ is a cytokine of the Th1 subset, which has been associated with the inflammatory process and kidney injury, and it plays a critical role in the immune response against viral infection (28)(29)(30).…”

Genetic and Functional Characterization of Toll-Like Receptor Responses in Immunocompetent Patients With CMV Mononucleosis

“…The genes encoding TLRs are extremely polymorphic and several studies have reported the association between single nucleotide polymorphisms (SNPs) in the TLRs and enhanced susceptibility and severity to systemic infections (Schroder and Schumann, 2005;Netea et al, 2012;Sezgin et al, 2019).…”