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Biomedical subjects

E R Kern

Publications and source records attributed to E R Kern.

At least 55 records · Page 3Linked to original sources
PubMed1994

Efficacy of A-73209, a potent orally active agent against VZV and HSV infections.

A-73209 is a novel oxetanocin derivative with potent in vitro and in vivo activity against VZV, HSV-1, and HSV-2. A-73209 was two logs more potent than acyclovir against five thymidine kinase positive (TK+) strains of VZV in vitro (mean EC50 0.01 vs. 1.22 micrograms/ml). The activity of A-73209 was one log more potent than acyclovir against TK+ HSV-1 strains in vitro (EC50 = 0.03 vs. 0.32 micrograms/ml). A-73209 yielded a mean EC50 of 2.2 micrograms/ml compared to a mean EC50 of 0.37 micrograms/ml for acyclovir against a panel of TK+ HSV-2 strains in vitro. The in vitro activity of A-73209 against thymidine kinase negative or deficient strains of VZV, HSV-1 and HSV-2 was much lower than for the corresponding TK+ strains. A-73209 produced efficacy superior to acyclovir against lethal systemic or intracerebral HSV-1 infections in mice. The greater efficacy of A-73209 relative to acyclovir was especially apparent with oral dosing. Against HSV-2 infections in mice, the efficacy of A-73209 ranged from equal to 1.7 times less active relative to acyclovir with oral dosing. A-73209 was orally bioavailable in mice, with maximal serum concentrations well in excess of in vitro inhibitory concentrations. A-73209 appears to be a potent and selective agent against varicella-zoster virus and herpes simplex virus infections.

Acyclovir↗
PubMed1994

Estimation of skin target site acyclovir concentrations following controlled (trans)dermal drug delivery in topical and systemic treatment of cutaneous HSV-1 infections in hairless mice.

The use of controlled transdermal delivery of acyclovir (ACV) in the treatment of cutaneous herpes simplex virus type 1 infections in hairless mice was investigated. Using an in vivo animal model (A. Gonsho, et al. Int. J. Pharm. 65:183-194 (1990)) made it possible to quantify both, the topical and the systemic antiviral efficacy of ACV transdermal patches as a function of the drug delivery rate of the patches. Drug delivery rates required to attain systemic efficacy were found to be higher than the rates required to attain the same magnitude of topical efficacy. The ACV concentrations in the basal cell layer of the epidermis for 50% topical efficacy and 50% systemic efficacy were estimated. The basal epidermis layer was considered to be the site of antiviral drug activity (skin target site). Systemic plasma levels were obtained from pharmacokinetic studies and were used to estimate the ACV concentration achieved systemically in the basal epidermis layer. A computational model for drug permeation across skin was employed to estimate the ACV concentration achieved topically in the basal epidermis layer. Equal topical and systemic efficacies were found to correspond to equal drug concentrations at the site of antiviral activity. The length of the effective diffusion pathway of drug molecules in the dermis prior to entering the blood circulation was assumed to be approximately equal to 1/20 of the anatomical dermis thickness because of dermis vascularization.

Acyclovir↗
PubMed1993

Evaluation of HPMPC therapy for primary and recurrent genital herpes in mice and guinea pigs.

The nucleoside analogue (S)-1-(3-hydroxy-2-phosphonylmethoxypropyl)cytosine (HPMPC) inhibited the replication of herpes simplex virus (HSV) types 1 and 2 in tissue culture cells at about 1.0 micrograms/ml, whereas Acyclovir (ACV) had an EC50 of about 0.10-0.50 micrograms/ml. The purpose of these studies was to evaluate the efficacy of topically applied HPMPC in animal models of primary and recurrent genital HSV-2 infections. Mice treated with 5%, 1% or 0.5% HPMPC three times daily, beginning 6 or 24 h after virus inoculation had reduced vaginal viral replication regardless of time of initiation of therapy. ACV at 5% also reduced vaginal viral replication, but not as effectively as HPMPC. In primary infection of guinea pigs, therapy with 5% or 1% HPMPC beginning at 24 h but not 72 h significantly altered lesion development. However, 5% HPMPC was highly toxic to guinea pigs. Vaginal viral replication was reduced significantly with either 1% or 0.3% HPMPC initiated at 24 h. In these studies, HPMPC was also more efficacious than 5% ACV. Topical treatment with 1% HPMPC did not reduce the incidence or severity of spontaneous or UV-induced recurrent genital lesions. These results indicate that topical therapy with 1%, 0.5% or 0.3% HPMPC was more effective than 5% ACV in the treatment of primary genital HSV-2 infections of guinea pigs and mice and suggest that HPMPC should be considered for topical use in humans.

Acyclovir↗
PubMed1993

Replication, establishment of latency, and induced reactivation of herpes simplex virus gamma 1 34.5 deletion mutants in rodent models.

Previous studies have shown that a gene mapping in the inverted repeats of the L component of herpes simplex virus, type 1 DNA, designated as gamma (1) 34.5, was dispensable for growth in cells in culture but that the deletion mutant (R3616) and a mutant containing a stop codon (R4009) in each copy of the gene were incapable of replicating in the central nervous systems (CNS) of mice. Restoration of the deleted sequences restored the wild type virus phenotype. We report here that the gamma (1) 34.5 mutant viruses (R3616 and R4009) replicated in the vaginal tract of two different strains of mice and guinea pig, although both viruses were shed at lower titer and for fewer days than the wild type and restored viruses. Both R3616 and R4009 failed to replicate or cause significant pathology in the cornea of Balb/C mice or following intranasal inoculation of Swiss Webster mice. Analyses of sensory trigeminal and dorsal root ganglia innervating the site of inoculation indicated that the incidence of establishment of latency or reactivation from latency by R3616 and R4009 viruses was significantly lower than that determined for mice infected with wild type or restored virus. Thus, selective deletion of gamma (1) 34.5 gene abolished the capacity of the virus to spread from peripheral mucosal sites to the CNS or replicate in the CNS, and diminished the capacity of the virus to replicate at mucosal sites and, subsequently, establish latency, or be able to be reactivated ex vivo. The results of our studies may have direct implications for the development of genetically engineered herpes simplex virus vaccines.

Animals↗
PubMed1992

Improved synthesis and biological evaluation of an acyclic thiosangivamycin active against human cytomegalovirus.

We previously described the synthesis and in vitro antiviral activity of an acyclic thiosangivamycin analog (Gupta et al., 1989a). In order to extend these initial studies, a new, multi-gram synthesis of 4-amino-7-[(2-hydroxy- ethoxy)methyl]pyrrolo]2,3-d]pyrimidine-5-thiocarboxamide (compound 229) was achieved in 5 steps from the known 5-amino-2-bromo-3,4-dicyanopyrrole in good overall yield. In plaque reduction assays with HCMV, compound 229 had an IC50 of 7 microM; in yield reduction assays the IC90 was 25 microM. The compound was less active against MCMV, HSV-1, HSV-2, and least active against VZV. Concentrations of compound 229 up to 32 microM did not affect the growth of KB cells for incubation periods up to 72 h. At 100 microM, a prolongation in population doubling time from 21 h (untreated) to 35 h was noted. This inhibition, however, was reversible upon removal of the compound suggesting the inhibition was cytostatic rather than cytotoxic. Flow cytometric studies with compound 229 in HFF cells revealed an accumulation of cells in S phase and a concurrent loss of cells in G2/M phase, suggesting an early S phase blockage. We conclude there is adequate separation between antiviral activity and cytotoxicity to merit further work with this class of pyrrolopyrimidines.

Antiviral Agents↗
PubMed1992

Immunotoxic potential of antiviral drugs: effects of ganciclovir and (S)-1-(3-hydroxy-2-phosphonylmethoxy propyl) cytosine on lymphocyte transformation and delayed-type hypersensitivity responses.

In the present studies, we examined the in vitro and in vivo effects of ganciclovir (DHPG) and a relatively new nucleoside analogue, (S)-1-(3-hydroxy-2-phosphonylmethoxy propyl) cytosine (HPMPC), on lymphocyte responses to T cell mitogens and delayed-type hypersensitivity (DTH) responses to dinitrofluorobenzene (DNFB). Initially, responses of mouse splenic mononuclear cells and human peripheral blood mononuclear cells to PHA and con A were evaluated in vitro in the presence of each drug. Both drugs inhibited the responses to each mitogens; however, DHPG had a greater inhibitory effect on con A responses of human and mouse lymphocytes than did HPMPC. Also, spleen cells from mice treated for 7 days with DHPG responded less well to PHA stimulation than cells from untreated or HPMPC-treated mice. No effect of either drug was observed on con A responses. Treatment of mice with either drug decreased the development of DTH responses, with HPMPC having a greater inhibitory effect than DHPG. The results from the present studies suggest that both DHPG and HPMPC may have inhibitory effects on the development of certain immune functions at high dosages, but at drug concentrations that were therapeutic in animal model studies, little inhibitory effects were observed.

Animals↗
PubMed1992

Effect of (S)-1-[(3-hydroxy-2-phosphonyl methoxy) propyl] cytosine on the replication and morphogenesis of herpes simplex virus type 1.

Treatment of African green monkey kidney cells with 1 microgram/ml of (S)-1-[(3-hydroxy-2-phosphonyl methoxy) propyl] cytosine (HPMPC) inhibited the release of infectious herpes simplex virus type 1 (HSV-1) by more than 90%. Electron microscopic observations of HPMPC-treated monkey kidney cells demonstrated few intracellular or extracellular viral particles. The viral particles seen were without dense cores. In addition, HPMPC blocked cell fusion induced by HSV-1 in monkey kidney cells. Immunoblot analysis showed that HPMPC significantly blocked the expression of HSV-1-specific proteins. Furthermore, HPMPC inhibited the synthesis of viral DNA as determined by in situ hybridization. These results indicate that HPMPC inhibits the replication of HSV by blocking one of the events involved in DNA synthesis.

Animals↗
PubMed1992

Novel animal model for evaluating topical efficacy of antiviral agents: flux versus efficacy correlations in the acyclovir treatment of cutaneous herpes simplex virus type 1 (HSV-1) infections in hairless mice.

This report describes the study of a novel animal model for the topical treatment of cutaneous herpes virus infections, with a focus upon the relationship between the dermal flux of the antiviral agent and the effectiveness of the topical therapy. A recently developed (trans)dermal delivery system (TDS) for controlling acyclovir (ACV) fluxes was employed in the treatment of cutaneous herpes simplex virus type 1 (HSV-1) infections in hairless mice. The TDS's were fabricated with rate-controlling membranes to provide nearly constant fluxes of ACV for up to 3 to 4 days. At the end of each experiment an extraction procedure was used to determine the residual ACV, validating the drug delivery performance of the TDS. Virus was inoculated into the skin of the mice at a site distant from the TDS area, and the induced lesion development was evaluated to distinguish between topical and systemic effectiveness of the therapy. In the main protocol, ACV therapy was initiated 0, 1, 2, and 3 days after virus inoculation and the lesion development "scored" on Day 5. The topical efficacies of 1- and 2-day-delayed treatments were essentially the same as that of a 0-day-delayed treatment, while the topical efficacy of a 3-day-delayed treatment was much poorer. Also, in the cases of 0-, 1-, and 2-day-delayed treatments, topical efficacy increased with increasing flux in the range of 10 to 100 micrograms/cm2-day. When the ACV flux was 100 micrograms/cm2-day or greater, a maximum 100% topical efficacy was obtained. The results for systemic efficacy were shifted to higher fluxes: approximately 10-fold greater ACV fluxes were necessary to provide efficacy equal to the topical efficacy results. The animals treated with a high ACV flux (350-500 micrograms/cm2-day) lived significantly longer than those treated with a low ACV flux (10-125 micrograms/cm2-day) and those of untreated (placebo) animals. Further, their mean survival time decreased with an increase in the time delay for ACV treatment. In contrast, the mean survival time for the animals which received a low ACV flux was similar to that of the control animals and remained unaltered with an increase in the time delay for ACV treatment. The approach developed in this study should be valuable in (a) the screening of new antiviral agents for the topical treatment of cutaneous herpes virus infections and (b) in the optimization of drug delivery systems (i.e., topical formulations).

Acyclovir↗
PubMed1991

Phosphonylmethoxyalkyl purine and pyrimidine derivatives for treatment of opportunistic cytomegalovirus and herpes simplex virus infections in murine AIDS.

Murine acquired immunodeficiency syndrome (MAIDS) was induced in C57BL/6 mice following infection with the LP-BM5 retrovirus complex. Infected mice developed splenomegaly, lymphadenopathy and loss of B- and T-cell functions 100 days after virus inoculation. Mice with AIDS were highly susceptible to opportunistic murine cytomegalovirus (MCMV) and herpes simplex virus (HSV-1) infections. The therapeutic activities of two phosphonylmethoxyalkyl derivatives, 9-(2-phosphonylmethoxyethyl)adenine (PMEA) and (S)-1-(3-hydroxy-2-phosphonylmethoxy-propyl)cytosine (HPMPC), were evaluated in MAIDS immunosuppressed mice infected with MCMV or HSV-1. MCMV infection resulted in extensive viral replication in lung, liver and spleen and death occurred five to twelve days post-infection. Treatment with either HPMPC or ganciclovir (DHPG) reduced mortality and viral replication in target organs; however, HPMPC was as effective as DHPG at one-fifth the DHPG dose. Moreover, when a single dose (100 mg/kg) of HPMPC was administered 24 h prior to MCMV infection, it suppressed virus replication at seven and 14 days post-infection, thus resulting in a significant prolongation of life. PMEA was effective against opportunistic HSV-1 infections, but appeared to be less effective than HPMPC against MCMV infections. These results indicate that MAIDS can be used as a model for evaluating antivirals in an immunocompromised host, and suggest that both PMEA and HPMPC may be useful in the treatment of opportunistic CMV and HSV-1 infections.

Adenine↗
PubMed1990

Mapping of herpes simplex virus-1 neurovirulence to gamma 134.5, a gene nonessential for growth in culture.

The gene designated gamma 134.5 maps in the inverted repeats flanking the long unique sequence of herpes simplex virus-1 (HSV-1) DNA, and therefore it is present in two copies per genome. This gene is not essential for viral growth in cell culture. Four recombinant viruses were genetically engineered to test the function of this gene. These were (i) a virus from which both copies of the gene were deleted, (ii) a virus containing a stop codon in both copies of the gene, (iii) a virus containing after the first codon an insert encoding a 16-amino acid epitope known to react with a specific monoclonal antibody, and (iv) a virus in which the deleted sequences were restored. The viruses from which the gene was deleted or which carried stop codons were avirulent on intracerebral inoculation of mice. The virus with the gene tagged by the sequence encoding the epitope was moderately virulent, whereas the restored virus reacquired the phenotype of the parent virus. Significant amounts of virus were recovered only from brains of animals inoculated with virulent viruses. Inasmuch as the product of the gamma 134.5 gene extended the host range of the virus by enabling it to replicate and destroy brain cells, it is a viral neurovirulence factor.

Amino Acid Sequence↗
PubMed1990

Synthesis, antiproliferative, and antiviral activity of certain 4-substituted and 4,5-disubstituted 7-[(1,3-dihydroxy-2-propoxy)methyl]pyrrolo[2,3-d]pyrimidines.

The sodium salts of 4-chloro- and several 4-chloro-5-substituted-7H-pyrrolo[2,3-d]pyrimidines were treated with [1,3-bis(benzyloxy)-2-propoxy]methyl chloride (6) to provide the corresponding 4-chloro- and 4-chloro-5-substituted-7-[[1,3-bis(benzyloxy)-2-propoxy]methyl]pyrrolo [2,3-d]pyrimidines (7-11). Debenzylation with boron trichloride at -78 degrees C furnished 4-chloro- and several 4-chloro-5-substituted-7-[(1,3-dihydroxy-2-propoxy)methyl]pyrrolo[2,3- d]pyrimidines (12.16). Subsequent amination of 12-16 yielded the 4-amino-5-substituted-7-[(1,3-dihydroxy-2-propoxy)methyl]pyrrolo[2,3- d]pyrimidines (17-21). Treatment of 14 with methylamine and 13 and 14 with ethylamine yielded the 4-(alkylamino)-5-halo-7-[(1,3-dihydroxy-2- propoxy)methyl]pyrrolo[2,3-d]pyrimidines (22-24). Treatment of 12-15 with hydroxylamine in refluxing 2-propanol yielded the 5-substituted-4-(hydroxyamino)-7-[(1,3-dihydroxy-2-propoxy)methyl]pyrrol o [2,3-d]pyrimidines (25-28). Treatment of compound 12 with Pd/C under a hydrogen atmosphere has furnished the nebularine analogue 31. The antiproliferative activity of compounds 17-28 and 31 was studied using L1210 cells in vitro. The 4-amino- and 4-(hydroxyamino)-5-halogenated derivatives (compounds 18-20, 26-28) inhibited cell growth. Although the effect of compounds 18-20 and 27 on final growth rate was pronounced (IC50 = 2.3, 0.7, 2.8, and 3.7 microM, respectively), cells underwent at least one doubling before cell division stopped. The remaining compounds were less cytotoxic, with IC50's greater than 30 microM for 21, 23, 26, and 28, whereas no inhibition of L1210 cell growth was observed with compounds 17, 22, 24, 25, and 31 at 100 microM. The antiviral activity of these compounds also was tested. Compounds 18-20 and 26-28 were active against human cytomegalovirus and herpes simplex type 1. The 4-amino derivatives (18-20) were more active than the 4-hydroxyamino derivatives (26-28), the 4-amino-5-bromo and 4-amino-5-iodo derivatives produced more than five log reductions in virus titer at concentrations of 10-100 microM. Although some cytotoxicity was observed at these concentrations, compound 19 was active against murine cytomegalovirus in vivo. At 5.6 mg/kg, 14/15 animals survived compared to 10/15 treated with 5.6 mg/kg of ganciclovir or 1/15 treated with placebo.

Animals↗
PubMed1990

Arabinofuranosylpyrrolo[2,3-d]pyrimidines as potential agents for human cytomegalovirus infections.

Protection of the 3'- and 5'-hydroxyl groups of the nucleoside antibiotic toyocamycin (1) with 1,3-dichloro-1,1,3,3-tetraisopropyldisiloxane was followed by (trifluoromethyl)sulfonylation of the 2'-hydroxyl group. A displacement of the resulting triflate ester moiety with lithium chloride, lithium bromide, sodium iodide, and lithium azide in hexamethylphosphoramide was followed by a removal of the disilyl moiety with tetra-n-butylammonium fluoride to afford the appropriate (2'-deoxy-2'-substituted-arabinofuranosyl)toyocamycin analogues 6a-d. Hydrolysis of the carbonitrile moieties of 6a-d with hydrogen peroxide gave the corresponding sangivamycin analogues (7a-d). A reduction of the azido moiety of 6a and 7a with 1,3-propanedithiol furnished the corresponding amino derivatives (6e and 7e). The antiproliferative activity of 6a-e and 7a-e was evaluated in L1210 cell cultures. None of these compounds caused significant inhibition of cell growth. Evaluation of these compounds for antiviral activity showed that all the toyocamycin analogues were active against human CMV, but of the sangivamycin analogues, only (2'-deoxy-2'-azidoarabinosyl)sangivamycin (7a) was active against this virus. None of the compounds were active against HSV-1 or HSV-2. (2'-Deoxy-2'-aminoarabinofuranosyl)toyocamycin (6e) was studied more extensively and showed some separation between antiviral activity and cytotoxicity as measured by effects on DNA synthesis, cell growth, and cell-plating efficiency. Although 6e also was active against murine CMV in vitro, it was not active against this virus in infected mice. We conclude that arabinosylpyrrolopyrimidines have potential as antivirals, but no members of the current series are potent enough to show significant activity in vivo.

Animals↗
PubMed1988

Efficacy of recombinant glycoprotein D subunit vaccines on the development of primary, recurrent, and latent genital infections with herpes simplex virus type 2 in guinea pigs.

Vaccination of guinea pigs with recombinant glycoprotein D (subunit vaccine) from either herpes simplex virus type 1 or type 2 (HSV-1, HSV-2), before intravaginal inoculation with HSV-2, markedly altered viral replication in the vaginal tract and reduced, or completely prevented, the development and spread of external genital lesions. Vaccination with glycoprotein D from HSV-2 prevented the establishment of latent HSV-2 infections in dorsal root ganglia and reduced the frequency of recurrent episodes. For all parameters of efficacy that we tested, vaccination with glycoprotein D from HSV-2 was more effective than was vaccination with protein derived from HSV-1. Vaccination after primary infection had no effect on the frequency or duration of recurrent HSV-2 infections.

Animals↗