Synthesis of herpes simplex virus structural proteins in arginine deprived cells

Eutrophication and the dietary promotion of sea turtle tumors

The tumor-forming disease fibropapillomatosis (FP) has afflicted sea turtle populations for decades with no clear cause. A lineage of α-herpesviruses associated with these tumors has existed for millennia, suggesting environmental factors are responsible for its recent epidemiology. In previous work, we described how herpesviruses could cause FP tumors through a metabolic influx of arginine. We demonstrated the disease prevails in chronically eutrophied coastal waters, and that turtles foraging in these sites might consume arginine-enriched macroalgae. Here, we test the idea using High-Performance Liquid Chromatography (HPLC) to describe the amino acid profiles of green turtle (Chelonia mydas) tumors and five common forage species of macroalgae from a range of eutrophic states. Tumors were notably elevated in glycine, proline, alanine, arginine, and serine and depleted in lysine when compared to baseline samples. All macroalgae from eutrophic locations had elevated arginine, and all species preferentially stored environmental nitrogen as arginine even at oligotrophic sites. From these results, we estimate adult turtles foraging at eutrophied sites increase their arginine intake 17-26 g daily, up to 14 times the background level. Arginine nitrogen increased with total macroalgae nitrogen and watershed nitrogen, and the invasive rhodophyte Hypnea musciformis significantly outperformed all other species in this respect. Our results confirm that eutrophication substantially increases the arginine content of macroalgae, which may metabolically promote latent herpesviruses and cause FP tumors in green turtles.

Land use, macroalgae, and a tumor-forming disease in marine turtles

Wildlife diseases are an increasing concern for endangered species conservation, but their occurrence, causes, and human influences are often unknown. We analyzed 3,939 records of stranded Hawaiian green sea turtles (Chelonia mydas) over 28 years to understand fibropapillomatosis, a tumor-forming disease linked to a herpesvirus. Turtle size is a consistent risk factor and size-standardized models revealed considerable spatial and temporal variability. The disease peaked in some areas in the 1990s, in some regions rates remained constant, and elsewhere rates increased. Land use, onshore of where the turtles feed, may play a role. Elevated disease rates were clustered in watersheds with high nitrogen-footprints; an index of natural and anthropogenic factors that affect coastal eutrophication. Further analysis shows strong epidemiological links between disease rates, nitrogen-footprints, and invasive macroalgae and points to foraging ecology. These turtles now forage on invasive macroalgae, which can dominate nutrient rich waters and sequester environmental N in the amino acid arginine. Arginine is known to regulate immune activity, promote herpesviruses, and contribute to tumor formation. Our results have implications for understanding diseases in aquatic organisms, eutrophication, herpesviruses, and tumor formation.

Effects of L-lysine and L-arginine on in vitro replication of feline herpesvirus type-1

OBJECTIVE

To determine the effects of various concentrations of L-lysine and L-arginine on in vitro replication of feline herpesvirus type-1 (FHV-1).

SAMPLE POPULATION

Cultured Crandell-Reese feline kidney (CRFK) cells and FHV-1 strain 727.

PROCEDURE

Uninfected CRFK cells or CRFK cells infected with FHV-1 were cultured in Dulbecco's modified Eagle's medium or in 1 of 7 test media containing various concentrations of lysine and arginine. Viral titer and CRFK growth rate were assessed in each medium.

RESULTS

Media depleted of arginine almost completely inhibited viral replication, whereas 2.5 or 5.0 microg of arginine/ml of media was associated with a significant increase in FHV-1 replication. In media with 2.5 microg of arginine/ml, supplementation with 200 or 300 microg of lysine/ml reduced viral replication by 34.2 and 53.9%, respectively. This effect was not seen in media containing 5.0 microg of arginine/ml. Growth rates of CRFK cells also were suppressed in media containing these concentrations of amino acids, but they were not significantly different from each other.

CONCLUSIONS AND CLINICAL RELEVANCE

Arginine exerts a substantial growth-promoting effect on FHV-1. Supplementation of viral culture medium with lysine attenuates this growth-promoting effect in media containing low concentrations of arginine. Analysis of data from this study indicates that high concentrations of lysine reduce in vitro replication of FHV-1 but only in media containing low concentrations of arginine. Clinical trials will be necessary to determine whether supplemental administration of lysine, with or without arginine restriction, will be useful in the management of cats with FHV-1 infections.

Restriction of herpes simplex virus by Ama 1 cells. An analysis of viral macromolecule synthesis

Ama 1 cells, and alpha-amanitin-resistant subline of CHO cells, restricted herpes simplex virus-1 and -2 replication. The infection was characterized by i) induction of typical cytopathology; ii) appearance of all the major virus proteins, glycoproteins and DNA earlier than in HEp-2 cells, followed by shut off of virus macromolecule synthesis; iii) defective maturation of viral particles, i.e. scarce assembly and lack of envelopment. The early shut off of viral DNA and protein synthesis, and the altered glycoprotein pattern may account for herpes simplex virus restriction.

The significance of the arginine and arginase of tears in experimentally-induced herpes simplex corneae

Experimental corneal herpes is always accompanied by the accumulation of arginine, the substrate of arginase, in tears, ensuring the multiplication of the herpes hominis virus. The main source of the large amount of arginine is the desquamating corneal epithelium, since after the epithelium of the cornea is abraded the arginine content of the tears again equals that of healthy tears. The low arginase content of rabbit tears can be supplemented by arginase applied as eyedrops, and this results in the cure of the herpetic process.