Common Virus Suppresses Immune Response Through IL10/STAT3 Pathway

Jenn Hoskins
7th May, 2025

Common Virus Suppresses Immune Response Through IL10/STAT3 Pathway

The human cytomegalovirus IE2 protein impairs key macrophage functions essential for an immune response, promoting a shift toward an anti-inflammatory M2 phenotype (a, b), reducing phagocytic activity against Escherichia coli (c, d), and increasing cell migration (e, f).

Image adapted from: Zhang et al. / CC BY (Source)

Key Findings

  • Researchers at Qingdao University discovered that a protein from the common virus HCMV, called IE2, weakens the immune system by targeting key immune cells
  • The IE2 protein prevents immune cells known as macrophages from effectively identifying and destroying the virus, hindering the body's defense
  • These findings could lead to new treatments that help the immune system better fight HCMV, especially in individuals with weakened immunity
Human cytomegalovirus (HCMV) is a common virus that remains in the body for life after infection. While it usually stays dormant without causing symptoms in healthy individuals, it can reactivate and lead to serious health issues, especially in people with weakened immune systems[2]. Understanding how HCMV evades the immune system is crucial for developing better treatments and diagnostic tools. A recent study conducted by researchers at the Affiliated Hospital of Qingdao University[1] has shed new light on one of the virus's key strategies for immune evasion. The study focuses on a protein produced by HCMV called intermediate-early protein 2 (IE2). This protein plays a significant role in how the virus manipulates the body’s immune response to ensure its survival and persistence. Macrophages, a type of immune cell, are among the first cells to encounter HCMV during infection. These cells are essential for defending the body against infections and play a critical role in initiating and regulating immune responses[3]. However, HCMV targets these macrophages to disrupt their normal functions. The research team used a transgenic mouse model to investigate how the IE2 protein affects macrophages' ability to present antigens, which are substances that trigger immune responses. Antigen presentation is a vital process where immune cells display pieces of pathogens to T cells, activating them to fight the infection[4]. By interfering with this process, HCMV can prevent the immune system from effectively recognizing and eliminating infected cells. The study found that IE2 alters the function of macrophages in several ways. Firstly, it prevents macrophages from performing phagocytosis, the process by which they engulf and destroy pathogens[2]. This inhibition allows the virus to evade being cleared by the immune system. Furthermore, IE2 affects the polarization of macrophages. Macrophages can adopt different states, known as M1 and M2, which are involved in initiating and resolving immune responses, respectively[3]. The study revealed that IE2 inhibits the normal activation of these macrophages, preventing them from fully engaging in their protective roles. This disruption leads to an overproduction of the anti-inflammatory cytokine IL-10 and the activation of a signaling molecule called STAT3. Elevated levels of IL-10 and activated STAT3 diminish the immune system's ability to respond effectively by promoting a type of T cell response known as T helper 2 (Th2)[3]. Th2 responses are generally associated with antibody production and are less effective in clearing viral infections compared to other types of immune responses. Previous research has shown that HCMV has multiple strategies to evade the immune system, including interfering with the presentation of viral antigens by major histocompatibility complex (MHC) molecules[4]. The current study builds on these findings by demonstrating that IE2 not only affects antigen presentation but also modulates the overall behavior of macrophages, further compromising the immune response. In addition to its impact on macrophages, the IE2 protein also interacts with other components of the immune system. For example, another study identified that HCMV can degrade STING, a crucial molecule in the innate immune response against DNA viruses, through the action of the IE86 protein, another viral factor[5]. This degradation prevents the activation of important antiviral pathways, highlighting the virus's multifaceted approach to immune evasion. The findings from the Affiliated Hospital of Qingdao University provide valuable insights into the molecular mechanisms by which HCMV evades the immune system. By understanding how IE2 impairs macrophage function and antigen presentation, scientists can explore new therapeutic strategies aimed at restoring proper immune function. Potential approaches could include developing drugs that inhibit the interaction between IE2 and macrophages or enhancing the immune system's ability to recognize and respond to HCMV-infected cells. Moreover, the study’s use of a transgenic mouse model offers a robust platform for further research into HCMV’s interactions with the immune system. Animal models are essential for studying the complex dynamics of viral infections and testing potential treatments before they are used in humans. Overall, this research highlights the sophisticated methods HCMV employs to persist in the human body and underscores the importance of continued investigation into viral immune evasion strategies. Advances in this area could lead to more effective treatments and preventive measures for those affected by HCMV, particularly individuals with compromised immune systems who are at higher risk for severe disease. By integrating these new findings with previous studies on HCMV’s immune evasion tactics[2][3][4][5], scientists are piecing together a comprehensive picture of how this virus maintains its presence in the host. This holistic understanding is essential for developing targeted therapies that can disrupt the virus’s ability to manipulate the immune system, ultimately improving patient outcomes and managing HCMV-associated diseases more effectively.

HealthGeneticsBiochem

References

Main Study

1) Human cytomegalovirus-IE2 suppresses antigen presentation of macrophage through the IL10/STAT3 signalling pathway in transgenic mouse

Published 5th May, 2025

https://doi.org/10.1371/journal.pone.0322334

Related Studies

2) Immunobiology of human cytomegalovirus: from bench to bedside.

https://doi.org/10.1128/CMR.00034-08

3) Human cytomegalovirus infection of M1 and M2 macrophages triggers inflammation and autologous T-cell proliferation.

https://doi.org/10.1128/JVI.01585-12

4) Diverse immune evasion strategies by human cytomegalovirus.

https://doi.org/10.1007/s12026-012-8304-8

5) Human Cytomegalovirus IE2 86 kDa Protein Induces STING Degradation and Inhibits cGAMP-Mediated IFN-β Induction.

https://doi.org/10.3389/fmicb.2017.01854


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