CXCL10 Inhibits Viral Replication Through Recruitment of Natural Killer Cells in Coxsackievirus B3-Induced Myocarditis

Abstract

Abstract-Coxsackievirus (CV)B3 is the primary cause of viral myocarditis. We previously observed CXC chemokine ligand 10 (CXCL10) upregulation in the myocardium early in infection. However, the impact of CXCL10 in CVB3-induced myocarditis is unknown. Using isolated primary mouse cardiomyocytes we demonstrated for the first time that cardiomyocytes can express CXCL10 on interferon-␥ stimulation. To explore the role of CXCL10 in CVB3-induced myocarditis, both CXCL10 transgenic and knockout mice were used. Following CVB3 challenges, the viral titer in the hearts inversely correlated with the levels of CXCL10 at early phase of infection before visible immune infiltration. Furthermore, as compared with the control mice, the decreased virus titers in the CXCL10 transgenic mouse hearts led to less cardiac damage and better cardiac function and vice verse in the knockout mice. This antiviral ability of CXCL10 might be through recruitment of natural killer (NK) cells to the heart and increased interferon-␥ expression early in infection. At day 7 postinfection, with massive influx of mononuclear cells the expression of CXCL10 enhanced the infiltration of CXCR3 ϩ cells, CD4ϩ , and CD8 ϩ T cells, as well as the expression of associated inflammatory cytokines. However, the augmented accumulation of these immune cells and associated cytokines failed to alter the viral clearance and mice survival. These results suggest the protective role of CXCL10 during the early course of CVB3 infection, which is attributed to the recruitment of NK cells. Nonetheless, CXCL10-directed chemoattractant effect is not sufficient for host to clear the virus in the heart. (Circ Res. 2009;104:628-638.) Key Words: cardiomyocytes Ⅲ chemokine CXCL 10 Ⅲ coxsackievirus Ⅲ myocarditis Ⅲ natural killer cells C oxsackievirus (CV)B3 has been recognized as the predominant cause of viral myocarditis in humans. 1 This disease is composed of three distinct stages including viremic injury, immune infiltration, and reclamation. 2 Earlier studies have suggested that mechanisms of viral myocarditis include direct myocyte injury by CVB3 and subsequent immune-mediated damage of the heart. 3,4 The essential role of the immune response in combating viral myocarditis has been demonstrated by recent studies using a series of knockout (KO) mice. Conversely, others have argued that the robust protective response can also be deleterious to host tissue to some extent. For instance, mice lacking T cells or T cell subsets developed less severe disease following CVB3 inoculation. 5 However, general immunosuppressive therapy did not benefit patients with myocarditis, 6 raising the need for better understanding the role of major immune mediators in disease cascade of CVB-induced myocarditis.During the process of leukocyte trafficking, it is well known that chemokines are the principle chemotactic factors to mediate leukocyte migration to the site of infection. 7 CXC chemokines, including interferon (IFN)-inducible protein 10 (IP10/CXCL10), monokine induced by IFN-␥ (Mig/CXCL9), an...

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“…Viral titers were determined as described previously. 58 Briefly, HeLa cells were seeded into 6-well plates (8 × 10 5 cells per well) and incubated at 37°C for 20 h to a confluence of~0%, then washed with PBS and overlaid with 500 μl of virus serially diluted in cell culture medium. Virus was obtained by centrifugation (4000 × g) of freeze-thawed cell suspensions as described above.…”

Quantitative Trait Locus Analysis, Pathway Analysis, and Consomic Mapping Show Genetic Variants of Tnni3k, Fpgt, or H28 Control Susceptibility to Viral Myocarditis

“…These data strongly suggest a protective role for type I IFN, particularly IFNb, during coxsackieviral infection. Recently, the constitutive expression of CXCL10 in the heart has been shown to attract NK cells to the heart, reducing overall viral replication (12). Though much progress has been made, there is still a need to account for differential susceptibility to viral myocarditis among otherwise normal individuals due to natural variation.…”

The Key Players of Coxsackievirus-Induced Myocarditis

“…By interacting with its receptor CXCR3, CXCL10 manipulates natural killer cell trafficking and their production of IFN-. Yuan et al recently found CXCL10 levels in the heart to be inversely related to viral titers after coxsackievirus B3 infection and a massive infiltration of CXCR3 + , CD4 + , and CD8 + cells (Yuan et al 2009). The production of associated inflammatory cytokines followed with the infiltration of leukocytes though the anti-viral response was not effective in clearing the virus or ensuring survival in coxsackievirus B3-infected CXCL10 transgenic mice (Yuan et al 2009).…”

“…Yuan et al recently found CXCL10 levels in the heart to be inversely related to viral titers after coxsackievirus B3 infection and a massive infiltration of CXCR3 + , CD4 + , and CD8 + cells (Yuan et al 2009). The production of associated inflammatory cytokines followed with the infiltration of leukocytes though the anti-viral response was not effective in clearing the virus or ensuring survival in coxsackievirus B3-infected CXCL10 transgenic mice (Yuan et al 2009). CXCL10 did assist viral clearance and protect myocytes from damage in the early stages of infection by robustly attracting NK cells and enhancing IFN-production to infection sites (Yuan et al 2009).…”

“…The production of associated inflammatory cytokines followed with the infiltration of leukocytes though the anti-viral response was not effective in clearing the virus or ensuring survival in coxsackievirus B3-infected CXCL10 transgenic mice (Yuan et al 2009). CXCL10 did assist viral clearance and protect myocytes from damage in the early stages of infection by robustly attracting NK cells and enhancing IFN-production to infection sites (Yuan et al 2009). Though CXCL10 appears to improve cardiac pathology and reduce viral persistence during initial infection stages, the caveat with using this chemokine as a potential coxsackievirus B3-induced myocarditis therapy lies with its inherent actions as a Th1-type chemeokine.…”