AMINO ACID REQUIREMENTS OF HERPES SIMPLEX VIRUS IN HUMAN CELLS

Structural, spectroscopic, in silico, in vitro and DNA binding evaluations of tyrosyl-lysyl-threonine

The main objective of the present study is to investigate the molecular structure and DNA binding interaction of the tyrosyl-lysyl-threonine (YKT) tripeptide, which has anticancer, antioxidant and analgesic properties, using various in silico (MD, QM, molecular docking), spectroscopic (UV, FT-IR, FTIR-ATR, Raman, gel electrophoresis) and in vitro (MCF-7 and HeLa cancer cell lines and BEAS-2B cell line) methods. The optimized geometry, vibrational wavenumbers, molecular electrostatic potential (MEP), natural bond orbital (NBO) and HOMO-LUMO (highest occupied molecular orbital- lowest unoccupied molecular orbital) calculations were carried out with Density Functional Theory (DFT) using B3LYP/6-311++G(d,p) basis set to indicate conformational, vibrational and intramolecular charge transfer characteristics. The assignment of all fundamental theoretical vibration wavenumbers was performed using potential energy distribution analysis (PED). DNA is a significant pharmacological target of drugs in several diseases such as cancer. For this reason, molecular docking calculation was used to elucidate the binding and interaction between YKT tripeptide and DNA at the atomic level. Also, the dynamic behaviors of YKT and DNA was examined using MD simulations. Besides, the interaction of YKT with DNA was experimentally examined by UV titration method and agarose gel electrophoresis method. Experimental results showed that YKT was intercalatively and electrostatically bound to CT-DNA (Calf thymus DNA) and cleavage pBR322 DNA in the presence of H₂O₂. The pharmacokinetic profile of YKT was also obtained. Cytotoxic effect of YKT was evaluated on MCF-7, HeLa and BEAS-2B cell lines. Hence, these studies about YKT tripeptide may pave the way for the development of various cancer drugs. Communicated by Ramaswamy H. Sarma.

Effects of Basic Amino Acids and Their Derivatives on SARS-CoV-2 and Influenza-A Virus Infection

Amino acids have been implicated with virus infection and replication. Here, we demonstrate the effects of two basic amino acids, arginine and lysine, and their ester derivatives on infection of two enveloped viruses, SARS-CoV-2, and influenza A virus. We found that lysine and its ester derivative can efficiently block infection of both viruses in vitro. Furthermore, the arginine ester derivative caused a significant boost in virus infection. Studies on their mechanism of action revealed that the compounds potentially disturb virus uncoating rather than virus attachment and endosomal acidification. Our findings suggest that lysine supplementation and the reduction of arginine-rich food intake can be considered as prophylactic and therapeutic regimens against these viruses while also providing a paradigm for the development of broad-spectrum antivirals.

L-lysine therapy to control the clinical evolution of pityriasis rosea: Clinical case report and literature review

Pityriasis rosea (PR) is a dermatological disease with an erythemato-papulosquamous manifestation, distributed on the trunk and extremities affecting healthy people, especially children and young people between 10 and 35 years of age. The evolution is 6 to 8 weeks and may remain for 3 to 6 months. It regresses spontaneously and can leave changes in the skin color but reversibly. Acyclovir is indicated to minimize clinical manifestations with the suspected of viral association (HHV-6 and 7). Another group of the human herpesvirus family (HHV-1 and 2), causes herpes simplex that is controlled with the antivirals, including acyclovir, as well as the amino acid L-lysine, both showing positive and similar results in reducing the number of annual manifestations and the healing time of the lesions. The aim of this study is to report a case of PR in a child, to review the literature on the etiopathogenesis of the disease and on the effects of L-lysine as well as another amino acid in the treatment. An 11-year-old girl, phototype II, presented lesions diagnosed as PR. The cycle would be 6 to 8 weeks on average. A solution of L-lysine was prescribed for 30 days, on an empty stomach. After the fourth day of therapy, the cycle of new eruptions was interrupted, initial lesions regressed, accelerating the repair of larger lesions resulting in an improvement of the clinical condition. We concluded that the administration of L-lysine, in therapeutic doses, can be a safe alternative for the PR control.

Recurrent Herpes Zoster Ophthalmicus Preceded by Anabolic Steroids and High-Dose L-Arginine

PURPOSE

To report a case of a 34-year-old male with recurrent herpes zoster ophthalmicus (HZO) preceded by a 6-week cycle of anabolic steroids and high-dose amino acid supplementation. Case Presentation. A 34-year-old man presented to our institution for left eye pain for one week associated with a vesicular rash in the V1 dermatome, respecting the midline. The patient had no significant past medical or past ocular history, including systemic immunosuppressive agents or HIV. However, prior to the onset of his symptoms the patient had completed a 6-week course of anabolic steroids including trenbolone, deca-durabolin, and testosterone as well as high-dose arginine supplementation averaging more than 40 grams a day. The best-corrected vision was 20/25 OS with slit-lamp examination remarkable for punctate staining and pseudodendrites at 6 o'clock, outside the visual axis. The patient was treated with oral acyclovir 800 mg five times a day for seven days along with prednisolone QID and moxifloxacin QID which was tapered over a month. Four months after resolution, the patient developed a recurrent HZO keratitis preceded by another cycle of anabolic steroids and amino acid supplementation.

CONCLUSION

In vitro L-arginine supplementation has been associated with the proliferation and virulence of a variety of herpes viruses. Anabolic steroids have also been demonstrated by various studies to negatively affect cell-mediated immunity necessary to prevent viral infection. Thus, it is possible that anabolic steroids in conjunction with increased L-arginine intake may have precipitated a recurrent HZO in a previously healthy, immunocompetent individual.

Recurrent herpes zoster ophthalmicus in a young, healthy individual taking high doses of l-Arginine

Purpose

To report a case of a healthy, young male with recurrent herpes zoster ophthalmicus (HZO) and high-dose l-arginine supplementation.

Observations

A 39-year-old man presented to another institution with a HZO involving the right eye. He was treated with oral acyclovir with complete resolution. Four months later the patient had a recurrent HZO episode and was started again on oral acyclovir. After resolution of the episode, the patient was continued on 1 g of oral acyclovir daily as a prophylactic measure. He then presented to our institution for a second opinion. The patient was otherwise healthy, with no past medical history involving systemic immunosuppressant agents or HIV. However, the patient was an active weight lifter taking high doses of amino acids. A diet recall was performed prior to both HZO episodes, which calculated an average intake of 46.5 g of l-arginine a day. Examination revealed 20/40 best-corrected acuity, anterior stromal haze in the visual axis, and inferior superficial punctate keratitis in the right eye. The patient was treated for dry eye disease with punctual plugs and artificial tears. The patient was instructed to decrease all supplemental arginine consumption while continuing with oral acyclovir prophylaxis for one year.

Conclusions and importance

l-arginine is associated with the replication and virulence of a variety of viruses in vitro, including herpes simplex and varicella zoster. Although arginine consumption increased prior to the initial and recurrent HZO infection, further investigation needs to be performed to deem if a true association exists.

Plasma L-Carnitine and L-Lysine Concentrations in HIV-Infected Patients

Background:

Virus infections are associated with significant alterations in host cells amino acids profiles that support biosynthetic demands necessary for production of viral progeny. Amino acids play an important role in the pathogenesis of all virus-related infections both as basic substrates for protein synthesis and as regulators in many metabolic pathways.

Objective:

Our aim was to determine the changes in plasma L-carnitine levels and its amino acid precursor (L-lysine) in HIV-infected patients.

Methods:

We performed a case-control study of 430 HIV-1 infected males (non-vegetarians) without any restriction in the nourishment, before highly active antiretroviral therapy (HAART) and 125 HIV-1 subjects after the introduction of HAART who were periodically monitored in the Municipal Center of HIV/AIDS prophylaxis, Surgut, Russian Federation

Results:

The plasma total (TC) and free (FC) L-carnitine concentrations markedly decreased with the clinical stages of HIV infection. The mean plasma TC, FC and L-lysine levels were significantly lower in asymptomatic stage (A) and advanced CDC stages (B, C) HIV-infected patients compared with our reference values. The total and free L-carnitine and its amino acid precursor concentrations mild increased in HIV-infected subjects after the introduction of HAART.

Our data revealed that L-lysine amino acid and its derivative (TC) levels were negatively correlated with viral load and inversely with CD4 count lymphocytes in the total cohort.

Conclusion:

The study results show that there was evidence for an association between plasma L-carnitine, L-lysine and HIV-1 RNA levels, immunological markers and clinical stages of HIV infection. The obtained data indicate that level changes of these host essential nutritional elements can play an important role in the HIV life cycle. These findings are important for understanding the pathophysiology of HIV infection and must be considered in further research for the development of new approaches in the treatment of the disease.

Effects of dietary lysine supplementation in cats with enzootic upper respiratory disease

To determine the effectiveness of dietary lysine supplementation in cats with enzootic upper respiratory disease (URD), 50 cats were fed a ration containing 11 or 51 g lysine/kg diet for 52 days. Food intake, body weight, clinical signs, plasma amino acid concentrations and presence of Chlamydophila felis or feline herpesvirus (FHV)-1 DNA within the conjunctival fornix were assessed. Food and lysine intake of both dietary groups decreased between days 17 and 22, coinciding with peak disease and viral presence. Mean disease score for cats fed the supplemented ration (0.94) was higher than for those fed the basal diet (0.21); however, this could be attributed to a small subset of male cats which demonstrated fighting behavior that may have contributed to stress within that cage. FHV-1 DNA was detected on 12 occasions in six cats receiving the supplemented diet and on one occasion in one cat fed the basal diet. C felis DNA was never detected. Mean plasma arginine concentration was lower and plasma lysine concentration was higher in supplemented cats. Mean plasma arginine concentration declined throughout the study in both dietary groups. Data from the present study raise important questions but do not permit a definitive conclusion regarding the efficacy of dietary lysine supplementation in cats with enzootic URD.

Development and evaluation of a host-targeted antiviral that abrogates herpes simplex virus replication through modulation of arginine-associated metabolic pathways

Since their inception five decades ago, most antivirals have been engineered to disrupt a single viral protein or process that is essential for viral replication. This approach has limited the overall therapeutic effectiveness and applicability of current antivirals due to restricted viral specificity, a propensity for development of drug resistance, and an inability to control deleterious host-mediated inflammation. As obligate intracellular parasites, viruses are reliant on host metabolism and macromolecular synthesis pathways. Of these biosynthetic processes, many viruses, including Herpes simplex viruses (HSV), are absolutely dependent on the bioavailability of arginine, a non-essential amino acid that is critical for many physiological and pathophysiological processes associated with either facilitating viral replication or progression of disease. To assess if targeting host arginine-associated metabolic pathways would inhibit HSV replication, a pegylated recombinant human Arginase I (peg-ArgI) was generated and its in vitro anti-herpetic activity was evaluated. Cells continuously treated with peg-ArgI for over 48 h exhibited no signs of cytotoxicity or loss of cell viability. The antiviral activity of peg-ArgI displayed a classical dose-response curve with IC50's in the sub-nanomolar range. peg-ArgI potently inhibited HSV-1 and HSV-2 viral replication, infectious virus production, cell-to-cell spread/transmission and virus-mediated cytopathic effects. Not unexpectedly given its host-targeted mechanism of action, peg-ArgI showed similar effectiveness at controlling replication of single and multidrug resistant HSV-1 mutants. These findings illustrate that targeting host arginine-associated metabolic pathways is an effective means of controlling viral replicative processes. Further exploration into the breadth of viruses inhibited by peg-ArgI, as well as the ability of peg-ArgI to suppress arginine-associated virus-mediated pathophysiological disease processes is warranted.

A review of antiviral drugs and other compounds with activity against feline herpesvirus type 1

Feline herpesvirus type 1 (FHV-1) is a common and important cause of ocular surface disease, dermatitis, respiratory disease, and potentially intraocular disease in cats. Many antiviral drugs developed for the treatment of humans infected with herpesviruses have been used to treat cats infected with FHV-1. Translational use of drugs in this manner ideally requires methodical investigation of their in vitro efficacy against FHV-1 followed by pharmacokinetic and safety trials in normal cats. Subsequently, placebo-controlled efficacy studies in experimentally inoculated animals should be performed followed, finally, by carefully designed and monitored clinical trials in client-owned animals. This review is intended to provide a concise overview of the available literature regarding the efficacy of antiviral drugs and other compounds with proven or putative activity against FHV-1, as well as a discussion of their safety in cats.

Influence of L-lysine amino acid on the HIV-1 RNA replication in vitro

BACKGROUND

Virus replication strongly depends on host metabolic machinery and essential cellular factors, in particular, on amino acid profiles. Amino acids play an important role in the pathogenesis of all virus-related infections both as basic substrates for protein synthesis and as regulators in many metabolic pathways, including gene expression. The inhibitory effects of deficiency or excess of these essential elements on virus replication are widely appreciated. Although the same interrelationship between host cellular factors and HIV have been recognized for a long time, the effects of amino acids on HIV-1 RNA replication dynamic is not yet well documented. Our aim was to determine in this pilot study the direct effect of L-lysine amino acid on HIV-1 RNA replication in vitro in HIV-infected patients.

METHODS

A total of 100 HIV-1-infected males without highly active antiretroviral therapy (HAART) were monitored in our center. The patients were in stage A of the disease according to the 1993 Centers for Disease Control (CDC) classification system for HIV-infection. Patients with HIV were enrolled in one stage (A) of the disease with the average amount CD4 lymphocytes in the range of 200-300 cells/µL at the time of sample acquisition. For evaluation of the effects of essential L-lysine amino acid on HIV-1 RNA replication level, we used a model of amino acid-excess system in vitro following incubation of plasma samples for 24 h at 25 °C. Quantitative HIV-1 RNA assay was performed using (RT-PCR) reverse-transcriptase polymerase chain reaction (Rotor-Gene Q, QIAGEN, Germany).

RESULTS

The mean HIV-1 RNA levels were significantly higher in the enriched peripheral blood mononuclear cells plasma samples HIV-infected subjects after 24 h incubation at 25 °C temperature than in the plasma samples the same patients studied on the date of blood tests (p < 0.0001). The number of HIV-1 RNA copies increased in 1.5 times. We observed that in plasma of the same HIV-infected patients after adding L-lysine and following incubation in vitro, viral load increased significantly in comparison with standard samples (p < 0.0001). The increased viral load was found in 100/92 (92%) of HIV-infected subjects. The average number of HIV-1 RNA copies in samples had increased by 4.0 times. However, we found no difference in HIV-1 RNA levels after replacement of L-lysine for L-arginine in comparison samples in the same HIV-infected patients. It is obvious that the addition of L-arginine does not increase viral replication in vitro as L-lysine amino acid supplement does. Additionally, no increase in viral load was determined after adding L-lysine and non toxic doses of its inhibitor (L-lysine alpha-oxidase) in plasma samples.

CONCLUSIONS

The results show that L-lysine amino acid excess is characterized by significant increased of HIV-1 RNA copies in enriched peripheral blood mononuclear cells plasma samples of HIV-infected patients. There was evidence for an association between L-lysine supplementation and HIV-1 RNA replication and the level changes of this host essential nutritional element play a key role in the synthesis of the virus proteins and in transcription initiation of the retrovirus life cycle. High intake of L-lysine amino acid may increase the risk of high viral load, subsequent acceleration of immunosuppression and HIV progression. Overall results demonstrate that the simple L-lysine-related model in vitro can be widely used for practical purposes to evaluate HIV-1 RNA replication dynamic, disease prognosis and new approaches in treatment of the patients with human immunodeficiency virus. Although the impact mechanism of L-lysine amino acid on the viral load in the pathogenesis of HIV-infection is at present conjectural and requires further development, the results highlight an interesting target in antiviral therapy, and this statement remains to be proved in further research and clinical trials.

Approved health claims for amino acids in/as food supplements

Food supplements in the European Union (EU) were initially regulated by Directive 2002/46/EC, whereas in 2006, EU adopted the new Regulation on nutrition and health claims made on food – Regulation 1924/2006. Meanwhile, in the United States of America (USA), dietary supplement is defined by the congress of Dietary Supplement Health and Education Act (DSHEA, 1994). Food supplements can be beneficial to the health of consumers, but scientific reviews of the existing data should be made by competent authorities. In Europe, a scientific review is made by European Food and Safety Authority (EFSA), the Panel of Dietetic Products, Nutrition and Allergies (NDA Panel). Amino-acids have been the object of many scientific studies, with many of them showing their implication in health. Amino-acids carry out a big role in many body functions, cells structure, transport and storage of nutrition, leading us to the main aim of this article that is providing data related to amino-acids implication in health benefits, specifically health claims of Arginine (Erection, vascular system, muscle integrity and hematopoesis immune system function, spermatogenesis), Glutamine (intestinal health, supporting glycogen replenishment, increasing cell swelling, immune health, abundance in the body, muscle function), Lysine (cardiovascular system, increase metabolism, bones, body tissue, immune system function). Nevertheless, they don`t take their credit yet and are not properly recognized in medical sciences in Europe, since the health claims of food containing amino-acids are still considered to be not established in terms of cause and effect relationship.

Lysine supplementation is not effective for the prevention or treatment of feline herpesvirus 1 infection in cats: a systematic review

BACKGROUND

Feline herpesvirus 1 is a highly contagious virus that affects many cats. Virus infection presents with flu-like signs and irritation of ocular and nasal regions. While cats can recover from active infections without medical treatment, examination by a veterinarian is recommended. Lysine supplementation appears to be a popular intervention (recommended by > 90 % of veterinarians in cat hospitals). We investigated the scientific merit of lysine supplementation by systematically reviewing all relevant literature.

METHODS

NCBI's PubMed database was used to search for published work on lysine and feline herpesvirus 1, as well as lysine and human herpesvirus 1. Seven studies on lysine and feline herpesvirus 1 (two in vitro studies and 5 studies with cats), and 10 publications on lysine and human herpesvirus 1 (three in vitro studies and 7 clinical trials) were included for qualitative analysis.

RESULTS

There is evidence at multiple levels that lysine supplementation is not effective for the prevention or treatment of feline herpesvirus 1 infection in cats. Lysine does not have any antiviral properties, but is believed to act by lowering arginine levels. However, lysine does not antagonize arginine in cats, and evidence that low intracellular arginine concentrations would inhibit viral replication is lacking. Furthermore, lowering arginine levels is highly undesirable since cats cannot synthesize this amino acid themselves. Arginine deficiency will result in hyperammonemia, which may be fatal. In vitro studies with feline herpesvirus 1 showed that lysine has no effect on the replication kinetics of the virus. Finally, and most importantly, several clinical studies with cats have shown that lysine is not effective for the prevention or the treatment of feline herpesvirus 1 infection, and some even reported increased infection frequency and disease severity in cats receiving lysine supplementation.

CONCLUSION

We recommend an immediate stop of lysine supplementation because of the complete lack of any scientific evidence for its efficacy.

In vitro characteristics of cyprinid herpesvirus 2: effect of kidney extract supplementation on growth

Herpesviral hematopoietic necrosis caused by goldfish hematopoietic necrosis virus (now identified as cyprinid herpesvirus 2, CyHV-2) has contributed to economic losses in goldfish Carassius auratus culture and is becoming a major obstacle in Prussian carp C. gibelio aquaculture in China. Several reports have described difficulties in culturing the virus, with the total loss of infectivity within several passages in cell culture. We succeeded in propagating CyHV-2 with a high infectious titer in a RyuF-2 cell line newly derived from the fin of the Ryukin goldfish variety using culture medium supplemented with 0.2% healthy goldfish kidney extract. The addition of kidney extract to the medium enabled rapid virus growth, resulting in the completion of cytopathic effect (CPE) within 4 to 6 d at 25°C. The extract also enabled reproducible virus culture with a titer of 105-6 TCID50 ml-1. The virus cultured using this protocol showed pathogenicity in goldfish after intraperitoneal injection. The virus grew in RyuF-2 cells at 15, 20, 25, 30, and 32°C but not at 34°C or higher. Higher incubation temperatures allowed earlier development of CPE, but culture at 30 and 32°C yielded a lower virus titer than that obtained at other temperatures because of heat inactivation of the propagated virus during cultivation. Cell lines derived from goldfish and ginbuna C. langsdorfii showed high susceptibility to the virus; cell lines from carp were susceptible to the virus using a medium containing goldfish kidney extract, but EPC, FHM, and BF-2 cell lines did not produce any CPE, even in the presence of the extract.

Lysinuric protein intolerance in a family of Mexican ancestry with a novel SLC7A7 gene deletion. Case report and review of the literature

Lysinuric protein intolerance (LPI) is a rare autosomal recessive disorder caused by mutations in the SLC7A7 located on the chromosome 14q11.2. LPI is most prevalent in Finland (1:50,000), Northern Japan (1:60,000) and Italy. Cases have also been reported in Spain and the United States. Here we report two siblings of Mexican descent. The older child was diagnosed at the age of three with severe chronic respiratory insufficiency leading to her demise. In contrast, the younger child was diagnosed soon after birth and dietary therapy has led to a stable life. Genetic analysis revealed a previously unreported deletion in the SLC7A7 gene. Additional research is needed to clarify the role of lysine in the pathophysiology of pulmonary proteinosis and herpes infections.

Effects of physiologic concentrations of l-lysine on in vitro replication of feline herpesvirus 1

OBJECTIVE

To evaluate the effects of various concentrations of l-lysine on in vitro replication of feline herpesvirus 1 (FHV-1).

SAMPLE

Cultures of Crandell-Rees feline kidney (CRFK) cells.

PROCEDURES

CRFK cells were inoculated with FHV-1 and maintained in media with 20 combinations of l-arginine and l-lysine concentrations. Changes in cell viability were monitored by continuous measurement of electrical impedance of cultured cells and by observation of viral cytopathic effects. Viral load was determined by use of quantitative PCR assay in supernatants obtained from infected cultures at specified time points.

RESULTS

Increases in l-lysine concentration had no effect on the kinetics of cell death in FHV-1-infected cultures. There was also no significant effect (r(2) < 0.1) on viral DNA load for l-arginine concentrations ≥ 12 μg/mL There was a significant effect of increases in l-lysine concentration on viral DNA load in media supplemented with 6 μg of l-arginine/mL (mean ± SD slope, -4,641 ± 1,626 units; adjusted r(2) = 0.45). However, the difference between the lowest (1 × 10(6.28) copies/μL) and highest (1 × 10(6.86) copies/μL) FHV-1 DNA load in these media was < 1 logarithm.

CONCLUSIONS AND CLINICAL RELEVANCE

The difference in FHV-1 DNA load was unlikely to be biologically important. Various l-lysine concentrations did not inhibit in vitro replication of FHV-1 at l-arginine concentrations sufficient to maintain cell growth. This conclusion was consistent with results of other studies in which investigators have not detected a consistently beneficial effect when l-lysine is administered to FHV-1-infected cats.

New insights into male (in)fertility: the importance of NO

Infertility is a global problem that is on the rise, especially during the last decade. Currently, infertility affects approximately 10-15% of the population worldwide. The frequency and origin of different forms of infertility varies. It has been shown that reactive oxygen and nitrogen species (ROS and RNS) are involved in the aetiology of infertility, especially male infertility. Various strategies have been designed to remove or decrease the production of ROS and RNS in spermatozoa, in particular during in vitro fertilization. However, in recent years it has been shown that spermatozoa naturally produce a variety of ROS/RNS, including superoxide anion radical (O2 (⋅-)), hydrogen peroxide and NO. These reactive species, in particular NO, are essential in regulating sperm capacitation and the acrosome reaction, two processes that need to be acquired by sperm in order to achieve fertilization potential. In addition, it has recently been shown that mitochondrial function is positively correlated with human sperm fertilization potential and quality and that NO and NO precursors increase sperm motility by increasing energy production in mitochondria. We will review the new link between sperm NO-driven redox regulation and infertility herein. A special emphasis will be placed on the potential implementation of new redox-active substances that modulate the content of NO in spermatozoa to increase fertility and promote conception.

Argininosuccinate synthetase 1 depletion produces a metabolic state conducive to herpes simplex virus 1 infection

Herpes simplex virus 1 (HSV-1) infection triggers specific metabolic changes in its host cell. To explore the interactions between cellular metabolism and HSV-1 infection, we performed an siRNA screen of cellular metabolic genes, measuring their effect on viral replication. The screen identified multiple enzymes predicted to influence HSV-1 replication, including argininosuccinate synthetase 1 (AS1), which consumes aspartate as part of de novo arginine synthesis. Knockdown of AS1 robustly enhanced viral genome replication and the production of infectious virus. Using high-resolution liquid chromatography-mass spectrometry, we found that the metabolic phenotype induced by knockdown of AS1 in human fibroblasts mimicked multiple aspects of the metabolic program observed during HSV-1 infection, including an increase in multiple nucleotides and their precursors. Together with the observation that AS1 protein and mRNA levels decrease during wild-type infection, this work suggests that reduced AS1 activity is partially responsible for the metabolic program induced by infection.

Role of lysine in the replication of reovirus: I. Synthesis of complete and empty virions

Lysine is essential for the replication of infectious reovirus. Omission of lysine from the extracellular medium not only permitted the continued synthesis of structural viral proteins and viral double-stranded ribonucleic acid (RNA), but also caused an enhanced formation of viral structures which were separable by isopycnic sedimentation of CsCl into a top band consisting of empty particles with a buoyant density of 1.29 g/cm(3) and essentially free of viral RNA, and two lower bands which were difficult to resolve and had an average buoyant density of 1.37 g/cm(3). The lower bands contained most of the viral nucleic acid. The above effects were reversed when lysine was restored early after infection. In contrast, a single band with a buoyant density of 1.38 g/cm(3) was obtained from lysine-plus infected cells.

Feline herpes dermatitis treated with interferon omega

This case report describes the diagnosis, demonstration and treatment of feline herpes virus‐induced facial dermatitis in a cat. The cat was successfully treated with interferon omega (IFN‐ω).

Effect of oral administration of L-lysine on conjunctivitis caused by feline herpesvirus in cats

OBJECTIVE

To determine whether oral administration of L-lysine to cats would lessen the severity of conjunctivitis caused by feline herpesvirus (FHV-1).

ANIMALS

8 healthy young adult cats.

PROCEDURE

Cats received oral administration of lysine monohydrochloride (500 mg, q 12 h) or placebo (lactose) beginning 6 hours prior to inoculation of virus. The left conjunctival sac received a 50-microl suspension of FHV-1 grown in cell culture (1.8 X 10(8) tissue culture infective dose50) on day 1. Cats were evaluated and scores given for clinical signs each day for 21 days. Samples for virus isolation were collected from the eye and throat every third day. Plasma lysine and arginine concentrations were measured prior to the study and on days 3, 14, and 22.

RESULTS

Cats that received lysine had less severe conjunctivitis than cats that received placebo. Virus isolation results did not differ between the groups. Plasma lysine concentration was significantly higher in cats that received lysine, compared with control cats, whereas plasma arginine concentrations did not differ between groups.

CONCLUSIONS AND CLINICAL RELEVANCE

Oral administration of 500 mg of lysine to cats was well tolerated and resulted in less severe manifestations of conjunctivitis caused by FHV-1, compared with cats that received placebo. Oral administration of lysine may be helpful in early treatment for FHV-1 infection by lessening the severity of disease.

Efficacy of oral supplementation with L-lysine in cats latently infected with feline herpesvirus

OBJECTIVE

To examine the effects of orally administered L-lysine on clinical signs of feline herpesvirus type 1 (FHV-1) infection and ocular shedding of FHV-1 in latently infected cats.

ANIMALS

14 young adult, FHV-1-naive cats.

PROCEDURE

Five months after primary conjunctival inoculation with FHV-1, cats were rehoused and assigned to receive 400 mg of L-lysine in food once daily for 30 days or food only. On day 15, all cats received methylprednisolone to induce viral reactivation. Clinical signs of infection were graded, and viral shedding was assessed by a polymerase chain reaction assay throughout our study. Peak and trough plasma amino acid concentrations were assessed on day 30.

RESULTS

Fewer cats and eyes were affected by conjunctivitis, and onset of clinical signs of infection was delayed on average by 7 days in cats receiving L-lysine, compared with cats in the control group; however, significant differences between groups were not demonstrated. Significantly fewer viral shedding episodes were identified in the treatment group cats, compared with the control group cats, after rehousing but not following corticosteroid-induced viral reactivation. Mean plasma L-lysine concentration was significantly increased at 3 hours but not at 24 hours after L-lysine administration. Plasma arginine concentration was not significantly altered.

CONCLUSIONS AND CLINICAL RELEVANCE

Once daily oral administration of 400 mg of L-lysine to cats latently infected with FHV-1 was associated with reduced viral shedding following changes in housing and husbandry but not following corticosteroid administration. This dose caused a significant but short-term increase in plasma L-lysine concentration without altering plasma arginine concentration or inducing adverse clinical effects.

Down-regulation of spontaneous Epstein-Barr virus reactivation in the P3HR-1 cell line by L-arginine

We tested the hypothesis that inhibition of Epstein-Barr virus (EBV) reactivation is controlled in part by nitric oxide (NO) generated from L-arginine (Arg). The spontaneous reactivation of EBV in the Burkitt's lymphoma (BL) cell line P3HR-1 was inhibited when the cells were cultured in L-Arg-supplemented medium. The expression of EBV early antigen (EA), immediate-early BZLF1 mRNA and the protein ZEBRA, and production of infectious virus were reduced by L-Arg supplementation in a dose-dependent manner. We demonstrated that inducible NO synthase (iNOS) mRNA was constitutively expressed in P3HR-1 cells, as quantitated by the reverse transcription-polymerase chain reaction. L-Arg supplementation enhanced iNOS and NOx expression in the cells. A specific NOS inhibitor, NG-monomethyl-L-Arg enhanced the expression of ZEBRA and early BMRF1 protein EA-D in the cells. L-Arg supplementation also inhibited the spontaneous EBV reactivation in another BL cell line EB1 and a B lymphoblastoid cell line OB. These results indicated that L-Arg induces iNOS and generates NO, which inhibits EBV reactivation in EBV-positive cells.

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.

Varicella and varicella immunity in patients with lysinuric protein intolerance

Two patients with lysinuric protein intolerance (LPI) had near-fatal generalized varicella infection with severe interstitial pneumonitis, hepatitis, decreased platelet count, bleeding and hypoalbuminaemia. Active haemolysis resulted in anaemia and massive haemoglobinuria. Serum lactate dehydrogenase activity and ferritin concentration, which in patients with LPI in normal circumstances exceed the upper reference values 3-folds to 10-fold, increased to > 10,000 U/L and > 10,000 micrograms/L, respectively. The patients were treated with fresh frozen plasma, red-cell transfusions and intravenous acyclovir for 14 days, and recovered clinically in a month. Retrospectively, 3 of the 32 other known Finnish patients with LPI had had varicella infection that had been more severe than that in the other children in the family or in subjects in the neighbourhood and had led to hospital admission. Varicella antibodies were measured in 24 patients; 5 had no antibodies and 5 had very low antibody titres. Primary vaccination of three patients with living varicella vaccine increased antibody titres measurably in one patient. We suggest that patients with LPI who have no varicella zoster antibodies should be treated with acyclovir if exposed to varicella and should be (re)vaccinated against chickenpox.

The metabolic roles, pharmacology, and toxicology of lysine

L-lysine monohydrochloride (LMH) is widely available to the public as a nonprescription oral supplement. Most of the pharmaceutical-grade product is used as a suppressant of recurrent herpes simplex infections. Recent publications indicate the possibility of other therapeutic uses, e.g., in cardiovascular disease and osteoporosis. These and other potential applications are surveyed and evaluated in this review with suggestions for further study. Data on toxicity are reviewed and recommendations made regarding safety of chronic dosage levels.

Antiviral effects of 6-diazo-5-oxo-L-norleucin on replication of herpes simplex virus type 1

An L-glutamine antagonist, 6-diazo-5-oxo-L-norleucin (L-DON), inhibits replication of vesicular stomatitis virus, poliovirus and paramyxoviruses in cultured cells. We tested the antiviral activity of L-DON against different strains of herpes simplex virus type 1 (HSV-1) in Vero cells. In the presence of a physiological plasma concentration of L-glutamine (0.5mM) L-Don inhibited 50% production of virus plaques at concentrations ranging from 7.9 to 16 microM. At concentrations of 40 microM L-Don inhibited infectious virus yield by 99%. The antiviral activity of L-DON decreased with increasing L-glutamine concentrations. A concentration of 5000 microM of L-Don had no significant effects on the viability of Vero cells. Transmission electron microscopical investigations showed that L-DON prevented mainly envelopment of viral nucleocapsids in the cytoplasm. The immunoprecipitation experiments demonstrated selective inhibition of synthesis of HSV-1 glycoproteins in L-DON treated cells. The results showed that L-DON inhibits HSV-1 replication at a late stage in the virus replication cycle, probably the cytoplasmic maturation of virions and subsequent virion egress from the cells.

Viral infections in the immunocompetent patient

Human herpesviruses and human papillomaviruses are ubiquitous and may cause an array of oral disease. Herpesviruses are unique because recurrent localized disease occurs after the primary infection. Human papillomaviruses are known for their ability to produce benign epithelial proliferations and increasingly are implicated in the development of oral cancer. This article reviews the pathogenesis of common oral lesions induced by these viruses.

Effect of L-lysine monohydrochloride on cutaneous herpes simplex virus in the guinea pig

The effect of topical applications of crystalline lysine therapy on cutaneous herpes simplex virus (HSV) inoculations and subsequent dorsal root ganglia (DRG) infection was studied in male Hartley guinea pigs. Although HSV-I was recovered from the inoculated sites from all animals, the L-lysine-treated skin remained clinically normal, whereas untreated controls manifested clinical symptoms up to 3 days postinoculation (p.i.). However, cocultivation of DRG (C1-S1) indicated a selective tropism of infective particles to specific DRG in the groups treated with amino acids. In lysine-treated animals, HSV was recovered from a few DRG (T-12, T-13, and L-1) at 3 days p.i. and from DRG T-10 in leucine-treated controls; yet no HSV was recovered from DRG of untreated controls. These results suggest an immunomodulatory effect of L-lysine on inoculation site infections and the possible potentiation of subsequent DRG manifestation in amino-acid-treated animals.

Pathogenesis of herpes simplex labialis: experimental induction of lesions with UV light

To develop a model system of herpes simplex labialis which would enable the study of patients before lesion onset, five patients were exposed to various doses of UV light from a sunlamp at their usual site of lesions. Six of 10 treatments resulted in the development of herpes labialis. Three of four treatments with the highest exposure levels led to large, vesicular, virus culture-positive sores. Side effects from sunlamp exposure were minimal.

Direct inactivation of viruses by MCP-1 and MCP-2, natural peptide antibiotics from rabbit leukocytes

Six homologous peptides were purified to homogeneity from rabbit granulocytes or alveolar macrophages and tested for their ability to inactivate herpes simplex virus type 1 (HSV-1). Two of the peptides, MCP-1 and MCP-2, showed considerable in vitro neutralizing activity, whereas four structurally homologous peptides (NP-3a, NP-3b, NP-4, and NP-5) were relatively ineffective. Inactivation of HSV-1 by MCP-1 or MCP-2 depended on peptide concentration and on the time, temperature, and pH of the incubation. HSV-2, vesicular stomatitis virus, and influenza virus A/WSN were also susceptible to direct neutralization by MCP-1 or MCP-2, whereas cytomegalovirus, echovirus type 11, and reovirus type 3 were not. We speculate that MCP-1 and MCP-2, peptides that are abundant in rabbit granulocytes and lung macrophages, may contribute to antiviral defenses by mediating the direct inactivation of HSV-1 and selected other viruses.

Lysine as a prophylactic agent in the treatment of recurrent herpes simplex labialis

The amino acid lysine is an agent that has been proposed for treating the clinical symptoms of recurrent herpes simplex labialis. This study examined the efficacy of long-term prophylactic lysine supplementation. Twenty-six volunteers with a history of frequently recurring herpetic lesions completed a 12-month double-blind crossovers study. The experimental group received daily oral supplements of 1,000 mg 1-lysine. Serum samples were analyzed at scheduled intervals. In most instances, members of the lysine group reported significantly fewer lesions than the control group. Similarly, those who were taken off lysine supplementation generally showed a significant increase in lesion frequency. Quantitative hematologic measurements revealed the most clinically useful relationship. Data from this sample population indicated that when a person's serum lysine concentration exceeded 165 nmol/ml there was a corresponding significant decrease in recurrence rate. Conversely, the frequency rate increased significantly as concentration levels fell below 165 nmol/ml. These results suggest that prophylactic lysine may be useful in managing selected cases of recurrent herpes simplex labialis if serum lysine levels can be maintained at adequate concentrations.

Contribution of macrophage arginase in the intrinsic restriction of herpes simplex virus replication in permissive macrophage cultures induced by gamma-interferon containing products of activated spleen cells

Cultured peritoneal macrophages (PM) from adult mice of strain DBA/2 (but not C57BL/6) supported productive replication of HSV, as monitored by infectious virus yield and electron microscopy. In contrast, PM of DBA/2 origin, when pretreated with supernatants of Con A-stimulated spleen cells containing immune interferon (IFN-gamma) activity, manifested remarkable intrinsic restriction to HSV replication. The acquisition of this intrinsic restriction to virus replication correlated with the generation of appreciably elevated levels of arginase in supernate of treated PM. Addition of incremental doses of exogenous arginine in the culture medium led to the abrogation of induced restriction to HSV replication in DBA/2 PM, indicating the critical role of arginase in the phenomenon. Furthermore, anti-HSV activity of arginase levels released into the culture medium of IFN containing supernate-treated PM became apparent when assayed on PM, which were precultured in arginine-deficient medium for 24 hours before virus infection and exposure to arginase containing preparation. Taken together, these observations indicate that macrophage arginase can mediate intrinsic restriction to HSV replication in PM.

Inhibition of herpes simplex virus multiplication by activated macrophages: a role for arginase?

Proteose-peptone-activated mouse macrophages can prevent productive infection by herpes simplex virus in neighboring cells in vitro whether or not those cells belong to the same animal species. The effect does not require contact between the macrophages and the infected cells, may be prevented by adding extra arginine to the medium, and may be reversed when extra arginine is added 24 h after the macrophages. Arginase activity was found both intracellularly and released from the macrophages. The extracellular enzyme is quite stable; 64% activity was found after 48 h of incubation at 37 degrees C in tissue culture medium. No evidence was found that the inefficiency of virus replication in macrophages was due to self-starvation by arginase. As might be predicted macrophages can, by the same mechanism, limit productive infection by vaccinia virus.

Genital herpes simplex--concepts and treatment

Genital herpes simplex is an increasingly common venereal disease caused by either herpes simplex virus type 1 or 2. The disease can be manifested in a primary and/or recurrent form, the clinical features and complications of which are reviewed. Potential problems include psychosocial difficulties, neonatal herpes simplex infections, and the possibility of an oncogenic role in cervical cancer. Diagnostic modalities, prophylactic measures, and management technics are discussed.

Interaction of feline sarcoma virus (FeSV) and mycoplasma

A factor present in the supernatant of an established human glioma cell line U-251 MG strongly suppresses feline sarcoma virus (FeSV) focus forming activity on feline embryo fibroblasts. The factor was identified as mycoplasma arginini. The enriched mycoplasma fraction had no cytpathogenic effect on the glioma cells or on the embryonic feline indicator cells. An antiserum prepared against this strain of mycoplasma abolished the inhibition. The exact mechanism is not known but arginine depletion in the medium seems to be an important factor.

Amino acid requirements for the growth of Aedes albopictus clone C6/36 cells and for the production of dengue and Chikungunya viruses in the infected cells

Amino acid requirements for the growth of Aedes albopictus, clone C6/36, cells and for the production of dengue (DEN) and Chikungunya (CHIK) viruses were examined by growing the cells or the viruses in media which were deprived of one of the 20 amino acids. Cell growth was markedly inhibited when cystine was omitted from the medium, and to a lesser extent by arginine deprivation. On the other hand, omission of alanine, asparagine, aspartic acid, and glutamic acid at the same time did not affect cell growth. Marked accumulation of alanine was observed in the medium when the cells were grown for 8 days in complete medium, with concomitant depletion of aspartic acid and glutamic acid. The production of CHIK virus was inhibited markedly by omission of cystine from the medium after virus infection, while the production of DEN viruses was more affected by glycine deprivation, although cystine deprivation also inhibited virus production to a lesser extent. On the other hand, production of CHIK and DEN viruses was not affected when alanine, asparagine, aspartic acid, and glutamic acid were omitted from the medium at the same time.

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.

Plaque formation by African swine fever virus in chick embryo fibroblasts in the absence of CO2 atmosphere

A plaque assay method using ASFV previously adapted to growth in chick embryo fibroblasts is described. Chick embryo fibroblast monolayers under bactoagar or methylcellulose have been employed using cysteine, arginine, DEAE-Dextran and HEPES as additives. Plaque production was optimal under methylcellulose. HEPES rendered the plaques more clear when used with the overlay. Arginine enhances plaque formation with bactoagar, and DEAE-Dextran doubles the plaque size. The growth curve of ASFV in chick embryo monolayers has been studied.