Chemical sympathectomy alters cytotoxic T lymphocyte responses to herpes simplex virus infection

Norepinephrine and Epinephrine Enhanced the Infectivity of Enterovirus 71

Background

Enterovirus 71 (EV71) infections may be associated with neurological complications, including brainstem encephalitis (BE). Severe EV71 BE may be complicated with autonomic nervous system (ANS) dysregulation and/or pulmonary edema (PE). ANS dysregulation is related to the overactivation of the sympathetic nervous system, which results from catecholamine release.

Objective

The aims of this study were to explore the effects of catecholamines on severe EV71 infection and to investigate the changes in the percentages of EV71-infected cells, virus titer, and cytokine production on the involvement of catecholamines.

Study Design

Plasma levels of norepinephrine (NE) and epinephrine (EP) in EV71-infected patients were measured using an enzyme-linked immunoassay. The expression of adrenergic receptors (ADRs) on RD, A549, SK-N-SH, THP-1, Jurkat and human peripheral blood mononuclear cells (hPBMCs) were detected using flow cytometry. The percentages of EV71-infected cells, virus titer, and cytokine production were investigated after treatment with NE and EP.

Results

The plasma levels of NE and EP were significantly higher in EV71-infected patients with ANS dysregulation and PE than in controls. Both α_1A- and β₂-ADRs were expressed on A549, RD, SK-N-SH, HL-60, THP-1, Jurkat cells and hPBMCs. NE treatment elevated the percentages of EV71-infected cells to 62.9% and 22.7% in THP-1 and Jurkat cells, respectively. Via treatment with EP, the percentages of EV71-infected cells were increased to 64.6% and 26.9% in THP-1 and Jurkat cells. The percentage of EV71-infected cells increased upon NE or EP treatment while the α- and β-blockers reduced the percentages of EV71-infected cells with NE or EP treatment. At least two-fold increase in virus titer was observed in EV71-infected A549, SK-N-SH and hPBMCs after treatment with NE or EP. IL-6 production was enhanced in EV71-infected hPBMCs at a concentration of 10² pg/mL NE.

Conclusion

The plasma levels of NE and EP elevated in EV71-infected patients with ANS dysregulation and PE. Both NE and EP enhanced the percentages of infected cells and virus titers in EV71 infection in vitro. NE and EP may play a role in the pathogenesis of EV71 BE complicated with ANS dysregulation and PE.

Chemical sympathectomy increases neutrophil-to-lymphocyte ratio in tumor-bearing rats but does not influence cancer progression

The sympathetic nervous system regulates many immune functions and modulates the anti-tumor immune defense response, too. Therefore, we studied the effect of 6-hydroxydopamine induced sympathectomy on selected hematological parameters and inflammatory markers in rats with Yoshida AH130 ascites hepatoma. We found that chemically sympathectomized tumor-bearing rats had significantly increased neutrophil-to-lymphocyte ratio, leukocyte-to-lymphocyte ratio, and plasma levels of tumor necrosis factor alpha. Although our findings showed that sympathetic denervation in tumor-bearing rats led to increased neutrophil-to-lymphocyte ratio, that is an indicator of the disease progression, we found no significant changes in tumor growth and survival of sympathectomized tumor-bearing rats.

Elevated maternal corticosterone during lactation hinders the neonatal adaptive immune response to herpes simplex virus (HSV) infection

The neonate's immune system is relatively immature. For short-term protection against pathogens the neonate is reliant primarily on maternally derived antibodies delivered via the mother's milk. However, neonates soon acquire the ability to generate adaptive immune responses for long-term protection. Products of the nervous and endocrine systems that are elicited by psychological stress are known to modulate a variety of immune responses. Additionally, psychological stressors are well recognized for their ability to increase corticosterone levels. The studies described herein examined the effects of increases in maternally derived corticosterone on the neonatal cell-mediated immune response to, and pathogenicity of, herpes simplex virus (HSV) infection. Water containing corticosterone was made available to nursing mothers for a period of 6 consecutive days beginning on either the day of or 6 days post-delivery. At 12 days of age, neonates were infected with HSV-1 in the rear footpads. These neonates exhibited a decrease in the proliferative ability of splenic-derived cells due to the reduction of IL-2 production and IL-2 receptor alpha subunit (IL-2R alpha) expression by these cells. These neonates also exhibited a decrease in the number and function of popliteal lymph node-resident HSV-1 gB(498-505) peptide-specific CD8(+) T cells as measured by tetramer analysis, CTL lytic activity, expression of CD107a, cytokine production, and proliferation. Additionally, these HSV-infected neonates exhibited increased morbidity and mortality. Together, these studies indicate that exposure of neonates to maternally derived corticosterone via the milk hinders their ability to generate an adaptive cell-mediated immune response to a viral infection and illustrate the potential importance of maternal stress in neonatal resistance to infectious pathogens.

Corticosterone impairs MHC class I antigen presentation by dendritic cells via reduction of peptide generation

The presentation of viral peptide-MHC class I complexes by antigen presenting cells, such as dendritic cells (DCs), is obligatory for the generation of antiviral effector and memory CD8(+) cytotoxic T lymphocyte (CTL) responses. Prolonged psychological stress is immunosuppressive and undermines primary and memory CTL-mediated antiviral immunity; however, the mechanisms involved are unknown. Using a panel of novel reagents and techniques, we quantitatively measured the effect of the stress-induced hormone corticosterone (CORT) on the efficiency of DCs to process and present virally expressed antigen, characterized the conditions for this CORT-mediated effect, and delineated the components of the MHC class I pathway that were affected. We found that physiologically relevant levels of CORT, prior to infection and acting via the glucocorticoid receptor, suppressed the formation of peptide-MHC class I complexes on the surface of infected DCs. We further showed that this suppression of peptide-MHC class I complexes is via the action of CORT on elements of the class I pathway upstream from TAP that are involved in the generation of antigenic peptides. This CORT-mediated suppression of peptide-class I complexes on DCs also resulted in a marked reduction of their ability to activate a specific T cell hybridoma. These findings offer a mechanism contributing to the stress-induced suppression of host defenses against viral diseases and have implications for the efficacy of antiviral vaccines. At the most fundamental cellular level, this impairment of antigen processing has implications for the regulation of protein degradation in all cells, which is critical to many aspects of immune function.

Mechanisms underlying chemical sympathectomy-induced suppression of herpes simplex virus-specific cytotoxic T lymphocyte activation and function

Lymphoid tissues are extensively innervated by noradrenergic fibers of the sympathetic nervous system. 6-hydroxydopamine (6-OHDA)-induced chemical sympathectomy is commonly used to assess the impact of this innervation on immune function. Using the glucocorticoid receptor antagonist RU486, the mineralocorticoid receptor antagonist spironolactone, and the beta-adrenergic receptor antagonist nadolol, the roles of corticosterone and norepinephrine in sympathectomy-mediated modulation of both the primary and memory cellular immune responses to herpes simplex virus type 1 (HSV-1) infection was investigated. We demonstrated that both of these immunomodulators play a role in mediating sympathectomy-induced suppression of the generation of HSV-specific primary cytotoxic T lymphocytes (CTL) and the activation of HSV-specific memory CTL (CTLm). Furthermore, we demonstrated a role for both Type I and Type II corticosteroid receptors in the regulation of HSV-specific immunity. Overall, these findings not only further support a role for neuroendocrine-mediated modulation of immune function, but also a need to exercise caution in attributing the effects of chemical sympathectomy to solely the absence of sympathetic innervation of lymphoid tissues.