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Glutamine and Leucine Provide Enhanced Protective Immunity Against Mucosal Infection with Herpes Simplex Virus Type 1

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Glutamine and Leucine Provide Enhanced Protective Immunity Against Mucosal Infection with Herpes Simplex Virus Type 1 http://dx.doi.org/10.4110/in.2012.12.5.196 ORIGINAL ARTICLE pISSN 1598-2629 eISSN 2092-6685 Glutamine and Leucine Provide Enhanced Protective Immunity Against Mucosal Infection with Herpes Simplex Virus Type 1 Erdenebileg Uyangaa1, Hern-Ku Lee2 and Seong Kug Eo1* 1College of Veterinary Medicine and Bio-Safety Research Institute, Chonbuk National University, 2Department of Immunology, Chonbuk National University Medical School, Jeonju 561-756, Korea Besides their role as building blocks of protein, there are [Immune Network 2012;12(5):196-206] growing evidences that some amino acids have roles in regu- lating key metabolic pathways that are necessary for main- tenance, growth, reproduction, and immunity. Here, we eval- INTRODUCTION uated the modulatory functions of several amino acids in pro- tective immunity against mucosal infection of herpes simplex There is growing evidence that as well as being the building virus type 1 (HSV-1). We found that glutamine (Gln) and leu- blocks of proteins and polypeptides, some amino acids have cine (Leu) showed enhanced protective immunity to HSV-1 roles in regulating key metabolic pathways that are necessary mucosal infection when two administration of Gln and single for maintenance, growth, reproduction, and immunity (1). administration of Leu per day, but not when administered in combinations. Ameliorated clinical signs of HSV-1 challenged They are called functional amino acids, which include argi- mice by the intraperitoneal administration of Gln and Leu nine (Arg), cystein (Cys), glutamine (Gln), leucine (Leu), pro- were closely associated with viral burden and IFN-γ pro- line (Pro), and tryptophan (Try). Dietary supplementation duction in the vaginal tract at 2 and 4 days post-infection. In with one or a mixture of these amino acids may be beneficial addition, the enhanced production of vaginal IFN-γ appeared for ameliorating health problems at various stages of the life to be caused by NK and HSV-1 antigen-specific Th1-type cycle, and for optimizing the efficiency of metabolic functions CD4+ T cells recruited into vaginal tract of mice treated with to enhance muscle growth, milk production, and athletic per- Gln and Leu, which indicates that IFN-γ, produced by NK formance (1-5). Indeed, microarray analysis indicates that di- and Th1-type CD4+ T cells, may be critical to control the etary supplementation with Gln or Arg increases the ex- outcome of diseases caused by HSV-1 mucosal infection. pression of anti-oxidative genes, and reduces the expression Collectively, our results indicate that intraperitoneal admin- of pro-inflammatory genes in the small intestine and adipose istration of Gln and Leu following HSV-1 mucosal infection tissues (6-8). In addition, some amino acids, such as Gln, Arg, could provide beneficial effects for the modulation of pro- tective immunity, but dosage and frequency of administration and Leu are known to stimulate the phosphorylation of should be carefully considered, because higher frequency mTOR1 in a cell-specific manner, thereby regulating intra- and overdose of Gln and Leu, or their combined treatment, cellular protein turnover (9-12). showed detrimental effects to protective immunity. Protein deficiency has long been known to impair immune Received on August 29, 2012. Revised on September 13, 2012. Accepted on September 14, 2012. CC This is an open access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0) which permits unrestricted non-commercial use, distribu- tion, and reproduction in any medium, provided the original work is properly cited. *Corresponding Author. Tel: 82-63-270-3882; Fax: 82-63-270-3780; E-mail: [email protected] Keywords: Glutamine, Leucine, Mucosal infection, Herpes simplex virus, Protective immunity Abbreviations: Asp, asparagine; Cys, cystein; Gln, glutamine; HSV-1, herpes simplex virus type 1; Arg, arginine; IDO, in- dole amine 2,3-dioxygenase; Leu, leucine; Lys, lysine; Phe, phenylalanine; Pro, proline; Try, tryptophan 196 IMMUNE NETWORK www.immunenetwork.org Volume 12 Number 5 October 2012 Modulation of HSV-1 Protective Immunity by Gln and Leu Erdenebileg Uyangaa, et al. function and increase the susceptibility of animals to disease. and cause mucocutaneous lesion, as manifested in orofacial Some amino acids, including Gln, Arg, methionine (Met), have and genital herpes (32,33). Importantly, HSV-1 is also neuro- been recognized as playing a role in the enhancement of im- tropic viruses, and establish latent infection in neurons, which mune function (13-15). The underlying mechanism may in- can be reservoirs of virus during subsequent events of volve mTOR activation, NO and glutathione synthesis, H2S sig- reactivation. The morbidity and socioeconomic burden asso- naling, and cellular redox state. In particular, catabolism of ciated with genital herpes as well as the alarming relationship Try via indoleamine 2,3-dioxygenase (IDO) appears to be crit- between genital herpes and the increased risk of acquiring ical for functions of both macrophages and lymphocytes (16). a HIV infection emphasize the need for development of an Thus, anthranilic acid (a metabolite of tryptophan via the IDO effective vaccine and/or therapeutics (32,33). Based on the pathway) inhibits production of proinflammatory cytokines accumulated results of biological functions of amino acid, we and prevents autoimmune inflammation (17). Gln is a non-es- evaluated the antiviral effect of several amino acids against sential amino acid which is also considered as an essential mucosal infection of HSV-1 in the present study. We found nutrient during multiple injury, trauma, and tumor (18-22). that Gln and Leu have specific roles in regulating protective Cell culture studies demonstrate that failure to supplement immunity against mucosal infection of HSV-1. culture media with Gln impairs the ability of lymphocytes to respond to mitogenic stimulation (23). In terminally differ- MATERIALS AND METHODS entiated macrophages, Gln may be required for the synthesis of mRNA for producing secretory proteins in immune chal- Mice, cells and viruses lenge during pinocytosis or phagocytosis (24). In addition, Female 5-to 6 week old BALB/c (H-2d) mice were purchased Gln has been shown to be beneficial in the prevention of in- from Samtako (O-San, Korea), and were maintained under fectious morbidity and mortality in seriously ill patients, due standard conditions at the animal facility of Chonbuk National to its ability to maintain the integrity of the intestinal mucosal University, according to the Institutional Guidelines. All ex- epithelium (25). It has also been suggested that Gln influences periments were conducted according to the guidelines of the the growth of immune cells, T helper function and responsive- committee on the Care of Laboratory Animal Resources. ness, and synthesis of immunoglobulin A (IgA) (21,22,26). In HSV-1 McKrae strain was propagated in Vero cells (CCL81, support, inadequate concentrations of Gln have been shown ATCC, Manassas, VA) using DMEM supplemented with 2.5% to compromise lymphocyte proliferation (27), IL-2 and IFN-γ FBS, penicillin (100 U/ml) and streptomycin (100 U/ml). The production (27,28), the expression of surface activation mark- Vero cells were infected with HSV-1 at a multiplicity of in- ers (CD25, CD45RO, and CD71) (28), and lymphokine-acti- fection (MOI) of 0.01, and were incubated in a CO2 incubator vated killer cell activity (29), and to decrease the proportion for 1 h at 37oC with shaking at 15 min intervals. After absorp- of CD4+ lymphocytes and the CD4+/CD8+ ratio (30). Leu, tion, the inoculum was removed, and 5 ml of maintenance one of branched chain amino acids, which also include iso- medium containing 2% was added. Approximately 2∼3 days leucine and valine, is an essential amino acid, and its concen- post-infection, cultures of the host cells showing an 80∼90% tration increases in skeletal muscle but decreases in plasma. cytopathic effect were harvested, and were titrated by con- It was assumed that Leu is a possible regulator of protein ventional plaque assay using Vero cells. The virus stocks turnover in muscle and the perfused liver. Also, Leu stim- were stored in aliquots at −80oC until use. ulates muscle protein synthesis under both in vitro and in vivo experimental conditions (31). The underlying mecha- Vaginal challenge nisms may involve activation of mTOR signaling to enhance The mice were pre-treated with progesterone to synchronize translation initiation and to inhibit autophagy in liver and their estrous cycles, as previously described (34). Briefly, muscle (25). Interestingly, other branched amino acids, iso- mice were subcutaneously injected with Depo-provera (DP) leucine and valine, have no effect on mTOR phosphorylation at 2 mg per mouse. Five days following the injection of DP, or muscle protein turnover (9,10), indicating a structural spe- the mice were challenged intravaginally with 106 pfu of HSV-1 cificity of Leu in cell signaling and function. McKrae strain per mouse, followed by intraperitoneal treat- Herpes simplex virus type 1 (HSV-1) is human pathogenic ment of the indicated amino acid solution daily. The mice viruses, which can replicate in cells of the epithelial lineage, were examined daily for vaginal inflammation, neurological IMMUNE NETWORK www.immunenetwork.org Volume 12 Number 5 October 2012 197 Modulation of HSV-1 Protective Immunity by Gln and Leu Erdenebileg Uyangaa, et al. illness, and
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