ACV-resistant Strains Research Articles

Amentoflavone Inhibits HSV-1 and ACV-Resistant Strain Infection by Suppressing Viral Early Infection.

Infection of Herpes simplex virus 1 (HSV-1) induces severe clinical disorders, such as herpes simplex encephalitis and keratitis. Acyclovir (ACV) is the current therapeutic drug against viral infection and ACV-resistant strains have gradually emerged, leading to the requirement for novel antiviral agents. In this study, we exhibited the antiviral activity of amentoflavone, a naturally occurring biflavonoid, toward HSV-1 and ACV-resistant strains. Amentoflavone significantly inhibited infection of HSV-1 (F strain), as well as several ACV-resistant strains including HSV-1/106, HSV-1/153 and HSV-1/Blue at high concentrations. Time-of-drug-addition assay further revealed that amentoflavone mainly impaired HSV-1 early infection. More detailed study demonstrated that amentoflavone affected cofilin-mediated F-actin reorganization and reduced the intracellular transportation of HSV-1 from the cell membrane to the nucleus. In addition, amentoflavone substantially decreased transcription of viral immediate early genes. Collectively, amentoflavone showed strong antiviral activity against HSV-1 and ACV-resistant strains, and amentoflavone could be a promising therapeutic candidate for HSV-1 pathogenesis.

Preparation of a monoPEGylated derivative of cyanovirin-N and its virucidal effect on acyclovir-resistant strains of herpes simplex virus type 1.

The long-term administration of acyclovir (ACV) for therapy against herpes simplex virus type 1 (HSV-1) infections can result in the emergence of ACV-resistant HSV strains. It is therefore urgent to develop new anti-herpetic compounds with mechanisms that differ from that of ACV. Cyanovirin-N (CV-N) is an antiviral agent that has an inhibitory effect on HSV-1 infections, and PEGylation of CV-N is potentially useful for pharmaceutical applications. Here, a (Gly4Ser)3 linker molecule was attached to the N-terminus of CV-N, and the resulting compound, linker-CV-N (LCV-N), was produced on a pilot scale with purity up to 95%. Then, PEG10k-LCV-N was synthesized by modifying at the α-amine group of the N-terminus of LCV-N with 10-kDa polyethylene glycol propionaldehyde (mPEG-ALD). CV-N, LCV-N and PEG10k-LCV-N were all found to have potent inhibitory activity against ACV-resistant HSV strains with IC50 values in the nM range. LCV-N was the most potent of these three compounds against both normal and ACV-resistant HSV strains. Although PEG10k-LCV-N showed less antiviral activity than CV-N and LCV-N, it still exhibited significant and universal virucidal activity against drug-resistant viruses. The toxicity and immunogenicity of PEG10k-LCV-N were dramatically lower than those of CV-N and LCV-N. In conclusion, we suggest that LCV-N and PEG10k-LCV-N are promising and safe microbicides for the control and/or treatment of ACV-resistant HSV infection.

R430: A potent inhibitor of DNA and RNA viruses

Acyclovir (ACV) is an effective antiviral agent for treating lytic Herpes Simplex virus, type 1 (HSV-1) infections, and it has dramatically reduced the mortality rate of herpes simplex encephalitis. However, HSV-1 resistance to ACV and its derivatives is being increasingly documented, particularly among immunocompromised individuals. The burgeoning drug resistance compels the search for a new generation of more efficacious anti-herpetic drugs. We have previously shown that trans-dihydrolycoricidine (R430), a lycorane-type alkaloid derivative, effectively inhibits HSV-1 infections in cultured cells. We now report that R430 also inhibits ACV-resistant HSV-1 strains, accompanied by global inhibition of viral gene transcription and enrichment of H3K27me3 methylation on viral gene promoters. Furthermore, we demonstrate that R430 prevents HSV-1 reactivation from latency in an ex vivo rodent model. Finally, among a panel of DNA viruses and RNA viruses, R430 inhibited Zika virus with high therapeutic index. Its therapeutic index is comparable to standard antiviral drugs, though it has greater toxicity in non-neuronal cells than in neuronal cells. Synthesis of additional derivatives could enable more efficacious antivirals and the identification of active pharmacophores.

Traditional Chinese Medicine as a Potential Source for HSV-1 Therapy by Acting on Virus or the Susceptibility of Host.

Herpes simplex virus type 1 (HSV-1) is the most common virus, with an estimated infection rate of 60–95% among the adult population. Once infected, HSV-1 can remain latent in the host for a lifetime and be reactivated in patients with a compromised immune system. Reactivation of latent HSV-1 can also be achieved by other stimuli. Though acyclovir (ACV) is a classic drug for HSV-1 infection, ACV-resistant strains have been found in immune-compromised patients and drug toxicity has also been commonly reported. Therefore, there is an urge to search for new anti-HSV-1 agents. Natural products with potential anti-HSV-1 activity have the advantages of minimal side effects, reduced toxicity, and they exert their effect by various mechanisms. This paper will not only provide a reference for the safe dose of these agents if they are to be used in humans, referring to the interrelated data obtained from in vitro experiments, but also introduce the main pharmacodynamic mechanisms of traditional Chinese medicine (TCM) against HSV-1. Taken together, TCM functions as a potential source for HSV-1 therapy by direct (blocking viral attachment/absorption/penetration/replication) or indirect (reducing the susceptibility to HSV-1 or regulating autophagy) antiviral activities. The potential of these active components in the development of anti-HSV-1 drugs will also be described.

Antiherpetic Plants: A Review of Active Extracts, Isolated Compounds, and Bioassays

Herpes simplex is a disease that is widely distributed throughout the world. It is caused by herpes simplex virus type 1 (HSV-1) and simplex virus type 2 (HSV-2). The drugs of choice for treatment are acyclovir (ACV), Penciclovir (PCV) and other guanine analogues, which have the same mechanism of action. However, due to the constant increase of ACV-resistant strains in immunocompromised patients, it is necessary to find new treatment alternatives. It has been shown that natural products are a good alternative for the treatment of these diseases as well as being an excellent source of compounds with anti-herpetic activity, which may be useful for the development of new drugs and act through a mechanism of action different from ACV and PCV. This paper compiles reports on extracts and compounds isolated from plants that have anti-herpetic activity. We present an analysis of the solvents most widely used for extraction from plants as well as cells and commonly used methods for evaluating cytotoxic and anti-herpetic activity. Families that have a higher number of plants with anti-herpetic activity are evaluated, and we also highlight the importance of studies of mechanisms of action of extracts and compounds with anti-herpetic activity.

Study of Antiherpetic Efficiency of Phosphite of Acycloguanosine Ableto Over come the Barrier of Resistance to Acyclovir

As has been shown previously, phosphite of acycloguanosine (Hp-ACG) exhibits equal efficacy against ACV-sensitive and ACV-resistant HSV-1 strains in cell culture. Intraperitoneal administration of Hp-ACG to model mice with herpetic encephalitis caused by HSV-1 infection was shown to be effective in protecting against death. In the present work, we continue the study of the antiviral efficiency of Hp-ACG against HSV administered non-invasively; namely in vivo, orally and in the form of ointment formulations. It has been first shown that oral administration of Hp-ACG twice daily for five days prevents systemic infection in mice caused by HSV-1. Mortality in the control group of animals was 57%. Administration of Hp-ACG at doses of 600, 800 and 1,000 mg/kg per day significantly increased the survival and median day of death of the animals compared to the placebo-treated control group. A comparative evaluation of the therapeutic efficacy parameters of polyethylene glycol-based ACV ointment and Hp-ACG ointment was carried out after a 5-day course in the model of an experimental cutaneous infection of HSV-1 in guinea pigs. It was found that Hp-ACG has a significant therapeutic effect resulting in a statistically significant reduction in the lesion's surface area and the amount of vesicular structures. The exhibited therapeutic effect of 10% Hp-ACG in ointment form compares well with that of 5% ACG ointment.

In vitro and in vivo antiherpetic effects of (1R,2R)-1-(5'-methylful-3'-yl)propane-1,2,3-triol.

In this study, we demonstrated the in vitro and in vivo antiherpetic activities of a stable furan derivative, (1R,2R)-1-(5'-methylful-3'-yl)propane-1,2,3-triol (MFPT), which had originally been isolated from Streptomyces sp. strain FV60. In the present study, we synthesized MFPT from (5-methylfuran-3-yl)methanol in 6 steps for use in the experiments. MFPT showed potent in vitro antiviral activities against two acyclovir (ACV)-sensitive (KOS and HF) strains and an ACV-resistant (A4-3) strain of herpes simplex virus type 1 (HSV-1) and an ACV-sensitive HSV type 2 (HSV-2) UW 268 strain, their selectivity indices ranging from 310 to 530. By intravaginal application of MFPT to mice, the virus yields decreased dose-dependently against the three strains of HSV-1 and HSV-2. When MFPT was applied at a dose of 1.0 mg/day, the lesion scores, as clinical signs manifested by viral infection, were extensively suppressed in HSV-1-infected mice, whereas the lesion scores in HSV-2-infected mice were not markedly decreased. Interestingly, MFPT exerted an inhibitory effect against ACV-resistant HSV-1 in mice to a similar degree as in ACV-sensitive HSV-1-infected mice. Therefore, the compound might have potential for developing a topical antiviral agent that could be also applied to the infections caused by ACV-resistant viruses.

Synthetic pregnenolone derivatives as antiviral agents against acyclovir-resistant isolates of Herpes Simplex Virus Type 1

The conventional therapy for the management of Herpes Simplex Virus Type 1 (HSV-1) infections mainly comprises acyclovir (ACV) and other nucleoside analogues. A common outcome of this treatment is the emergence of resistant viral strains, principally when immunosuppressed patients are involved. Thus, the development of new antiherpetic compounds remains as a central challenge. In this work we describe the synthesis and the in vitro antiherpetic activity of a new family of steroidal compounds derived from the endogenous hormone pregnenolone. Some of these derivatives showed a remarkable inhibitory effect on HSV-1 spread both on wild type and ACV-resistant strains. The results also show that these compounds seem to interfere with the late steps of the viral cycle.

Sequence Analysis of Herpes Simplex Virus 1 Thymidine Kinase and DNA Polymerase Genes from over 300 Clinical Isolates from 1973 to 2014 Finds Novel Mutations That May Be Relevant for Development of Antiviral Resistance.

A total of 302 clinical herpes simplex virus 1 (HSV-1) strains, collected over 4 decades from 1973 to 2014, were characterized retrospectively for drug resistance. All HSV-1 isolates were analyzed genotypically for nonsynonymous mutations in the thymidine kinase (TK) and DNA polymerase (Pol) genes. The resistance phenotype against acyclovir (ACV) and/or foscarnet (FOS) was examined in the case of novel, unclear, or resistance-related mutations. Twenty-six novel natural polymorphisms could be detected in the TK gene and 69 in the DNA Pol gene. Furthermore, three novel resistance-associated mutations (two in the TK gene and one in the DNA Pol gene) were analyzed, and eight known but hitherto unclear amino acid substitutions (two encoded in TK and six in the DNA Pol gene) could be clarified. Between 1973 and 2014, the distribution of amino acid changes related to the natural gene polymorphisms of TK and DNA Pol remained largely stable. Resistance to ACV was confirmed phenotypically for 16 isolates, and resistance to ACV plus FOS was confirmed for 1 isolate. Acyclovir-resistant strains were observed from the year 1995 onwards, predominantly in immunosuppressed patients, especially those with stem cell transplantation, and the number of ACV-resistant strains increased during the last 2 decades. The data confirm the strong genetic variability among HIV-1 isolates, which is more pronounced in the DNA Pol gene than in the TK gene, and will facilitate considerably the rapid genotypic diagnosis of HSV-1 resistance.

Ellagitannins as synergists of ACV on the replication of ACV-resistant strains of HSV 1 and 2

The plant-derived polyphenolic compounds castalagin, vescalagin and grandinin (C-glucosidic ellagitannins containing nonahydroxyterphenoyl) manifested a strong inhibitory effect on the replication of acyclovir-resistant strains of herpes simplex viruses (HSV) type 1 and 2 in MDBK cells in focus forming units (i.e., microscopically registered microplaques) reduction assay and in two variants of cytopathic effect inhibition test. The effect on the acyclovir (ACV)-resistant herpes simplex virus type 1 (HSV-1) strain was markedly higher compared to that on the ACV-resistant herpes simplex virus type 2 (HSV-2). The three compounds showed comparable levels of antiviral activity against ACV-resistant HSV strains, in contrast with previous results where castalagin exerted the highest degree of activity against wild type HSV strains (Vilhelmova et al., 2011). Combinations of ellagitannins and ACV were tested on the ACV-resistant strains of both HSV-1 and 2 and produced synergistic effects that were revealed by applying the three-dimensional approach of Prichard and Shipman (1990). The ellagitannin(s)-ACV combination applied against ACV-resistant HSV-1 produced a much stronger synergistic effect compared to the effect observed against ACV-resistant HSV-2. The study of the effects of the combination ellagitannin(s)-ACF on intact cell monolayers did not show any toxicity resulting from interaction between the two substances. Altogether, the results obtained in this study demonstrate the highly promising potential of these plant polyphenols as antiherpetic agents.

Recalcitrant Pseudotumoral Anogenital Herpes Simplex Virus Type 2 in HIV-Infected Patients: Evidence for Predominant B-Lymphoplasmocytic Infiltration and Immunomodulators as Effective Therapeutic Strategy

In patients with human immunodeficiency virus (HIV) infection, genital herpetic lesions may be extensive and tend to persist for longer periods; in addition, atypical hypertrophic, ulcerative, or pseudotumor forms have been reported, frequently showing resistance to acyclovir (ACV) treatment. Between 2003 and 2011, 10 HIV-1-infected patients presenting with chronic pseudotumoral anogenital herpes simplex type 2 (HSV-2) infections were studied. All patients developed chronic, hypertrophic HSV-2 anogenital lesions with multilesional presentation in 7 cases and involvement of 2 anatomical sites in 6 of them. At the time of diagnosis, the median CD3(+)CD4(+) absolute blood count was 480.5 cells/µL (range, 165-632 cells/µL), whereas the plasma HIV load was undetectable in all cases. Histopathologic analysis of lesion biopsies showed a moderately dense dermal polytypic plasma cell infiltrate. Detection of HSV-2 by culture and/or polymerase chain reaction was positive for all patients, with evidence for ACV-resistant strains in 6 of 8 cases. In addition, viral resistance to ACV was found only in HSV-2 isolated from ulcerative lesions, whereas purely pseudotumoral ones harbored sensitive strains. Durable control was observed with HSV DNA polymerase inhibitors in only 2 cases, and the immunomodulators imiquimod and thalidomide allowed 5 patients to reach sustained complete response. HSV-2-related pseudolymphoma in HIV-infected patients is characterized by a predominant polyclonal lymphoplasmacytic infiltration, and is frequently refractory to antiherpetic drugs. Immunomodulatory therapeutic strategies using thalidomide showed consistent efficacy, and should be considered early during the course of disease.

In vitro and in vivo evaluation of a novel antiherpetic flavonoid, 4′-phenylflavone, and its synergistic actions with acyclovir

The development of therapeutic agents for preventing herpes simplex virus (HSV) infections has become urgently necessary because of the increasing incidence of this virus and its role as a cofactor in the transmission of human immunodeficiency virus infection. We have evaluated the antiviral activities of a series of natural and synthetic flavonoids and found that a synthetic flavonoid, 4'-phenylflavone, showed the highest activity against acyclovir (ACV)-sensitive and ACV-resistant strains of HSV-1, as well as HSV-2, with a selectivity index of 213, 35 and 55, respectively. Although the attachment and penetration of HSV-1 to host cells and the synthesis of viral proteins were not inhibited, the infectivity of the virus and the amount of progeny virus released were reduced by 4'-phenylflavone treatment in a dose-dependent manner. 4'-Phenylflavone plus ACV synergistically inhibited the replication of HSV-1. This flavonoid also showed efficacy in vivo and potentiated the antiherpetic effect of ACV in a mouse model of genital herpes. Our results suggest that 4'-phenylflavone might be useful as a candidate for the development of novel antiherpetic therapeutics.

Novel Resistance-Associated Mutations of Thymidine Kinase and Dna Polymerase Genes of Herpes Simplex Virus Type 1 and Type 2

Studies to verify correlations between phenotypes and genotypes of herpes simplex virus (HSV) are an important tool to establish a database of resistance-associated mutations. In this study, 32 acyclovir (ACV)-resistant clinical HSV-1 and 4 ACV-resistant clinical HSV-2 isolates were examined in parallel by both phenotypic and genotypic resistance testing. Additionally, five non-viable HSV-1 strains and two non-viable HSV-2 strains with clinical resistance were included in genotypic resistance analysis. All ACV-resistant HSV isolates showed cross-resistance to brivudin and penciclovir, and were sensitive to foscarnet and cidofovir. Acyclovir resistance was assigned to frameshift and single non-synonymous mutations of the thymidine kinase (TK) gene in 32 out of 37 HSV-1 strains and in 4 out of 6 HSV-2 strains. In three HSV-1 isolates, there were resistance-associated amino acid substitutions of the DNA polymerase (pol). Six substitutions in the TK and two in the DNA pol gene could not be attributed without doubt to either ACV resistance or natural gene polymorphism. Altogether, 10 resistance-related mutations in the TK and 1 in the DNA pol gene have not been reported previously. The novel non-synonymous mutations found in this study enrich the knowledge about the genetic alterations of TK and DNA pol genes in ACV-resistant clinical HSV strains. Together with data from the literature, the findings justify the generation of a HSV database that contains resistance mutations associated with ACV resistance phenotype.

Reporter cell line-based screening for anti-varicella-zoster virus compounds

Objective To establish a novel method to screen for anti-varicella-zoster virus (VZV) compounds with our previously generated reporter cell line for VZV, MV9G. Methods MV9G cells were directly infected with cell-free virus of Oka vaccine strain (vOka) for 2 hours( CFV direct-infection) or cocultured with vOka-infected MeWo cells containing cell-associated virus for 48 hours (CAV co-culture) to promote expression of the reporter gene firefly luciferase. Antiviral compounds including heparin, mannose-6-phosphate( M-6-P), acyclovir( ACV ), resveratrol and roscovitine were added in the medium before or after the virus infection. Inhibitory effects( IC50 ) of the antiviral compounds were analyzed by comparing firefly luciferase activities of MV9G cells in the presence of antiviral compounds with those in the absence. Results Antiviral compounds inhibited luciferase activities of MV9G cells activated by CFV direct-infection and/or CAV co-culture in different levels. The reductions of luciferase activities statistically correlated with those of viral foci shown by immunostaining with a monoclonal antibody against VZV immediate early 62 antigens (IE62) in controls. Among these compounds, heparin, M-6-P, and 2.5 μmol/L of roscovitine inhibited CFV-activated more strongly than CAV-activated luciferase activities, whereas ACV and resveratrol inhibited CAV-activated more strongly than CFV-activated luciferase activities. Cell-associated ACV-resistant strains,Kanno and rOka YSR, activated luciferase activities of MV9G cells, too. However, the inhibitory concentrations (IC50) of ACV to the ACV-resistant strains were much higher than those to the ACV-sensitive strains,pOka and CaGu. Conclusion The CFV direct-infection and CAV co-culture assays were useful to screen for antiviral compounds targeting the early and late phases of VZV infection, respectively. The VZV reporter cell-based assays may provide a simple, rapid, sensitive, and high-throughput method to screen for anti-VZV compounds. Key words: Varicella-zoster virus; Reporter cell line; Mannose-6-phosphate; Resveratrol; Roscovitine

Phenotypic and genotypic characterization of acyclovir-resistant clinical isolates of herpes simplex virus

Sixteen herpes simplex virus type 1 (HSV-1) and four type 2 (HSV-2) isolates resistant to acyclovir (ACV) were characterized retrospectively for drug resistance. Phenotypic testing was performed by means of tetrazolium reduction assay and genotypic analysis was carried out by sequencing of thymidine kinase (TK) and DNA-polymerase (pol) genes. All strains were characterized as cross-resistant to penciclovir, brivudin and susceptible to cidofovir. In addition, three strains were resistant to foscarnet. Genotypic analysis revealed two to seven non-synonymous mutations in the TK gene of HSV-1 and one to seven non-synonymous mutations in the DNA pol gene of HSV-1 and 2 associated with the gene polymorphism. Seventeen strains contained at least one non-synonymous resistant-related mutation in the TK gene and three strains, which were additionally foscarnet-resistant, revealed one resistance-associated mutation in the DNA pol gene. In most strains, resistant-related mutations in TK gene represented frameshift mutations and single non-synonymous nucleotide substitutions of conserved gene regions. However, numerous amino acid changes could not be interpreted clearly as accounting for resistance. In conclusion, further studies, e.g. site-directed mutagenesis experiments are required to characterize mutations of the TK and DNA pol genes in ACV-resistant viral strains as part of viral gene polymorphism or as cause of drug resistance.

Phenoxazine Derivatives Suppress the Infections Caused by Herpes Simplex Virus Type-1 and Herpes Simplex Virus Type-2 Intravaginally Inoculated Into Mice

We examined the in vivo antiviral activities of 2-amino-4,4α-dihydro-4α-7-dimethyl-3H-phenoxazine-3-one (Phx-1), 3-amino-1,4α-dihydro-4α-8-dimethyl-2H-phenoxazine-2-one (Phx-2), and 2-aminophenoxazine-3-one (Phx-3) against herpes viruses. The virus yield three days after administration, changes in the 6-degree’s lesion scores, and the morbidity were assessed after herpes simplex virus type-1 (HSV-1) [acyclovir (ACV)-sensitive KOS strain or ACV-resistant A4-3 strain] or HSV-2 (ACV-sensitive UW 268 strain) was inoculated intravaginally to mice with administration of Phx-1, Phx-2, Phx-3, or ACV (0.2 mg per administration, 3 times daily) for 8 days starting from 1 day before virus inoculation to 7 days after infection. Phx-1, Phx-2, and Phx-3 extensively suppressed the virus yield of HSV-1. Only Phx-2 exerted moderate inhibitory effects against HSV-2 in mice. The lesion scores, as clinical signs manifested by infection of the KOS strain of HSV-1, were extensively suppressed by intravaginal application of Phx-1, Phx-2, or Phx-3. The lesion scores in HSV-2–infected mice indicated moderate suppression, when Phx-1, Phx-2, or Phx-3 was applied. Without treatment by one of the compounds, none of the HSV-1– infected mice died, but all the HSV-2–infected ones did. However, by the administration of Phx-1, Phx-2, or Phx-3 fairly improved the survival rates of the HSV-2–infected mice. Phx-2 showed dose-dependent anti-HSV-2 efficacy when administered at doses of 0.2 and 1 mg per administration. The present in vivo data suggest that the Phx-1, Phx-2, and Phx-3 are attractive candidates for agents to prevent both replication of HSV and aggravation of lesions caused by these viruses.

Successful kinase bypass with new acyclovir phosphoramidate prodrugs

Novel phosphoramidates of acyclovir have been prepared and evaluated in vitro against acyclovir-sensitive and -resistant herpes simplex virus (HSV) types 1 and 2 and varicella-zoster virus (VZV). Unlike the parent nucleoside these novel phosphate prodrugs retain antiviral potency versus the ACV-resistant virus strain, suggesting an efficient bypass of the viral thymidine kinase.

In vitro Antiviral Activity of Distamycin A against Clinical Isolates of Herpes Simplex Virus 1 and 2 from Transplanted Patients

Objective(s): Herpes simplex virus (HSV) infections in immunocompromised individuals may require prolonged antiviral therapy resulting in the emergence of viral strains resistant to the currently employed antiviral drugs. Distamycin A (DA), a basic antibiotic belonging to the lexitropsin DNA minor groove binding drugs, exhibits antiviral properties. In this study we evaluated the in vitro cytotoxicity and antiviral activity of DA against HSV type 1 and HSV type 2 clinical isolates from transplanted patients and compared them with those of acyclovir (ACV) in search of alternative antiviral drugs. Methods: Viral detection and typing was performed by multiplex PCR and immunofluorescence assay; the in vitro cytotoxicity of DA and the antiviral activity of ACV and DA was evaluated respectively by neutral red uptake assay and plaque reduction assay for HSV2 isolates and fluorescence reduction assay for HSV1 isolates. Results: Tissue culture 50% cytotoxic concentration of DA was 58 µM. Tissue culture 50% inhibitory concentration values ranged from 0.16 to 7.4 µM for the ACV-sensitive and from 5.4 to 32 µM for the ACV-resistant viral strains. Conclusions: In spite of the lower activity against ACV-resistant strains, DA may be used as an antiherpetic drug.

Frequency of acyclovir‐resistant herpes simplex viruses isolated from the general immunocompetent population and patients with acquired immunodeficiency syndrome

Herpes simplex virus (HSV) infections are usually chronically recurrent in the normal population and represent a significant cause of morbidity in immunocompromised patients. Acyclovir (ACV) is widely used for the treatment and prophylaxis of HSV infections. The emergence of ACV-resistant strains has been frequently reported as a result of long-term ACV therapy. Despite the widespread use of ACV, there are no data available in our area on the frequency of ACV-resistant HSVs. The purpose of this study was to evaluate the susceptibility of HSV isolated from normal subjects and patients with acquired immunodeficiency syndrome (AIDS) to ACV. HSVs were isolated from the orofacial region of normal individuals and patients with AIDS. The susceptibility of isolated HSV strains to various concentrations of ACV was determined by plaque reduction assay. The sensitivity of the viral strains was expressed as IC(50) (the concentration of drug reducing the viral plaque by 50%). One hundred and thirty-three isolates from 102 normal subjects and 31 patients with AIDS were tested. One HSV-1 isolate from normal individuals had intermediate susceptibility. Two ACV-resistant isolates (one HSV-1 and one HSV-2), with IC(50) > or = 2 to < or = 3 microg/mL, and one highly resistant HSV-2 isolate, with IC(50) > or = 5 microg/mL, were detected in patients with AIDS. Our data show that the prevalence of ACV-resistant strains is very low in the general immunocompetent population; however, in patients with AIDS, the prevalence of ACV-resistant strains is remarkable (P = 0.001). Alternative antiherpetic agents should be employed to control and reduce the emergence of ACV-resistant strains in patients with AIDS.

Antiviral Activity of Esterified α-Lactalbumin and β-Lactoglobulin against Herpes Simplex Virus Type 1. Comparison with the Effect of Acyclovir and l-Polylysines

The antiviral activity of methylated alpha-lactalbumin (Met-ALA), methylated and ethylated beta-lactoglobulins (Met- and Et-BLG) was evaluated against acyclovir (ACV)-sensitive and -resistant strains of herpes simplex virus type 1 (HSV-1) and compared to that of ACV and L-polylysines (4-15 kDa) using fixed or suspended Vero cell lines. Esterified whey proteins and their peptic hydrolyzates displayed protective action against HSV-1, which was relatively lower than that induced by ACV or L-polylysines. The higher activity of L-polylysines was maintained against an ACV-resistant strain of HSV-1, whereas ACV lost much of its activity. The mean 50% inhibitory concentration (IC50) was about 0.8-0.9 microg/mL for L-polylysines against ACV-sensitive and -resistant strains of HSV-1 when using two concentrations of virus (50% and 100% cytopathic effect, CPE). The IC50 values of ACV against the sensitive strain of HSV-1 were 3 and 15 microg/mL when using the low and high concentrations of virus, respectively. When using 50% CPE, IC50 values for esterified whey proteins ranged from 20 to 95 microg/mL, depending on the nature of the ester group, the degree of esterification, and the nature of the protein. Using the real-time PCR technique, it was shown that Met-ALA inhibited HSV-1 replication.