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

Objective-To determine the effects of varies 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 FH V-1 strain 727. Procedure-Uninfected CRFK cells or CRFK cells infected with FHV-1 were cult ured in Dulbecco's modified Eagle's medium or in 1 of 7 test media containi ng various concentrations of lysine and arginine. Viral titer and CRFK grow th rate were assessed in each medium. Results-Media depleted of arginine almost completely inhibited viral replic ation, whereas 2.5 or 5.0 mug of arginine/ml of media was associated with a significant increase in FHV-1 replication. In media with 2.5 mug of argini ne/ml, supplementation with 200 or 300 mug of lysine/ml reduced viral repli cation by 34.2 and 53.9%, respectively. This effect was not seen in media c ontaining 5.0 mug of arginine/ml. Growth rates of CRFK cells also were supp ressed in media containing these concentrations of amino acids, but they we re not significantly different from each other. Conclusions and Clinical Relevance-Arginine exerts a substantial growth-pro moting effect on FHV-1, Supplementation of viral culture medium with lysine attenuates this growth-promoting effect in media containing low concentrat ions of arginine. Analysis of data from this study indicates that high conc entrations of lysine reduce in vitro replication of FHV-1 but only in media containing low concentrations of arginine. Clinical trials will be necessa ry to determine whether supplemental administration of lysine, with or with out arginine restriction, will be useful in the management of cats with FHV -1 infections.