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Biomedical subjects

R J Whitley

Publications and source records attributed to R J Whitley.

At least 73 records · Page 4Linked to original sources
PubMed1996

Sorivudine: a potent inhibitor of varicella zoster virus replication.

Sorivudine provides a unique nucleoside analog with significantly enhanced both in vitro as in vitro activity toward VZV and enhanced oral bioavailability, as compared with existing antivirals. Early indications from controlled studies, while not peer reviewed, indicate that sorivudine therapy is superior to acyclovir for the treatment of localized zoster in individuals with HIV infection and chicken pox in adults. These studies await peer evaluation. One might question, as these data unfold, the relative clinical value of antivirals with such enhanced in vitro activity and oral bioavailability as compared to standard compounds. Should these drugs induce accelerated healing, but not as dramatically as would have been anticipated from the in vitro data, new approaches to the management of herpes zoster will need to be developed if further improvement is desired. Despite this provision, sorivudine therapy does appear to result in significantly accelerated healing of cutaneous zoster as compared to acyclovir, and sorivudine can be administered once daily in a dose that is one-hundredth that of acyclovir, and less than one tenth of the doses of valacuyclovir or famciclovir. These findings in and of themselves should allow for licensure of the compound in developed societies.

Adult↗
PubMed1996

Differential effect of recombinant human and mouse interferons on replication of herpes simplex virus type 1 in mouse cells.

Pretreatment of murine (BALB/3T3) cells with either murine or recombinant hybrid human B/D interferon (IFN) blocked the release of infectious herpes simplex virus type 1 (HSV-1) from treated cells. The block in replication was not due to an effect on attachment of HSV-1 to the target cells or to toxic effects of IFN. Immunoblot analyses showed that murine IFN significantly reduced the expression of virus-specific proteins in IFN-treated cells. In contrast, B/D IFN had no major effect on the expression of viral proteins in treated cells. In support of the above observation, electron microscopy of virus-infected cells displayed formation of nucleocapsids within the nucleus of IFN-treated cells. However, the expression of glycoproteins B and D was reduced in B/D IFN-treated cells. These results suggested that murine IFN blocked HSV-1 replication at an early stage whereas B/D IFN inhibited HSV-1 replication at a late stage in virus morphogenesis.

3T3 Cells↗
PubMed1996

Summary of the International Consensus Symposium on Advances in the Diagnosis, Treatment and Prophylaxis and Cytomegalovirus Infection.

CMV infection and CMV disease can be difficult to differentiate and the diagnosis is usually based on a compatible clinical picture and the results of a diagnostic test for CMV. The only exception to this rule is in HIV-infected patients where fundoscopy is sufficient to diagnose CMV retinitis. Of the current diagnostic tests, qualitative and quantitative PCR, branched DNA and Hybrid Capture, are the most promising. The pp65 antigenemia assay has the disadvantage of being more labor-intensive than the DNA based tests. Preliminary data show that a positive qualitative PCR in a HIV-infected patient has a predictive value for the development of CMV retinitis. However, of the patients positive by qualitative PCR, those with high viral loads in quantitative PCR were at the greatest risk of CMV disease. This might make it possible to identify with great certainty the patients who will go on to develop CMV retinitis, thereby decreasing the number of patients eligible for preemptive or prophylactic therapy and increasing the cost-benefit of this therapeutic measure. Quantitative test might also be useful in monitoring response to therapy, but randomized trials comparing the test are needed. Prophylactic antiviral agents should not be used in seronegative transplant recipients receiving organs from seronegative donors. In high-risk transplant recipients, ganciclovir should be used. CMV vaccines are useful for the protection of babies from CMV seronegative mothers against congenital CMV disease. It also may be useful in seronegative transplant recipients receiving a seropositive donor organ, although the benefit of chemo prophylaxis may surpass that of vaccine. HIV-infected patients with CMV retinitis who relapse under either ganciclovir or foscarnet benefit from subsequent combination therapy, rather than switching to the other drug. However, the cost is high in terms of quality of life. Intravitreal therapy for CMV retinitis is very efficacious, suggesting that drug delivery is a problem in systemic therapy. However, intravitreal therapy does not protect against the development of CMV retinitis in the contralateral eye or from CMV disease elsewhere. Therefore, systemic therapy should be added. CMV disease of the CNS should be diagnosed early and treated agressively, possible with combination therapy. A diagnosis of CMV disease should be based on a compatible clinical picture and the demonstration of CMV in CSF by DNA or antigen assays which are more sensitive than culture.

Animals↗
PubMed1996

Oral acyclovir therapy accelerates pain resolution in patients with herpes zoster: a meta-analysis of placebo-controlled trials.

Meta-analysis of four double-blind, randomized, placebo-controlled trials of oral acyclovir (800 mg five times daily) for the treatment of herpes zoster was conducted to provide definitive assessments of the effect of acyclovir on the resolution of zoster-associated pain. The studies involved a total of 691 patients, and the analysis was performed on an intent-to-treat basis. A range of milestones of pain cessation were evaluated by means of Cox regression models with adjustment for relevant prognostic factors. The proportion of patients with postherpetic neuralgia at 3 and 6 months was also determined. Advancing age and more severe pain at presentation were associated with more prolonged pain. Acyclovir was clearly shown to accelerate pain resolution by all of the measures employed. Benefit was especially evident in patients 50 years of age or older. Fewer acyclovir recipients had postherpetic neuralgia at 3 or 6 months. Overall, the reductions of pain duration and prevalence were approximately twofold.

Acyclovir↗
PubMed1996

Application of the polymerase chain reaction to the diagnosis and management of neonatal herpes simplex virus disease. National Institute of Allergy and Infectious Diseases Collaborative Antiviral Study Group.

Cerebrospinal fluid (CSF) specimens from 77 neonates with herpes simplex virus (HSV) disease were evaluated retrospectively by polymerase chain reaction (PCR). Samples were collected from 202 infants enrolled in a National Institute of Allergy and Infectious Diseases Collaborative Antiviral Study Group trial that compared vidarabine with acyclovir for the treatment of neonatal HSV infection. HSV DNA was detected in the CSF of 26 (76%) of 34 infants with CNS disease, in 13 (93%) of 14 infants with disseminated infection, and in 7 (24%) of 29 with skin, eye, or mouth (SEM) involvement. One of the 7 PCR-positive SEM patients subsequently developed severe neurologic impairment. Eighteen (95%) of 19 infants with positive CSF PCR results after the completion of 10 days of antiviral therapy experienced significant morbidity or mortality. Application of PCR to neonatal HSV disease may provide additional information on which clinical decisions may be based, although its diagnostic utility outside the research setting is unproven.

Brain↗
PubMed1996

Antiviral resistance: mechanisms, clinical significance, and future implications.

The increased awareness of antiviral resistance over the past decade has paralleled the development of new antiviral agents. While such resistant viral isolates are of clinical significance primarily in immunocompromised individuals, the development and transmission of such mutants have been reported in immunocompetent persons as well. As antiviral agents are increasingly utilised by the clinician, the incidence of such occurrences is likely to increase. Issues relating to mechanisms of antiviral resistance, clinical manifestations and significance of resistance, and implications for future antiviral development and utilisation are reviewed in this article. Viruses that are discussed include herpes simplex virus, varicella-zoster virus, cytomegalovirus, influenza A virus, and human immunodeficiency virus.

Antiviral Agents↗
PubMed1996

Drug discovery for human immunodeficiency virus infection: conquests and hurdles.

Drug development for the treatment of human immunodeficiency virus infection arena has been characterised by both successes and failures. The nucleoside reverse transcriptase inhibitors have been the major development for the management of the Acquired Immune Deficiency Disease Syndrome (AIDS); there has been a notable lack of licensed compounds directed at sites other than reverse transcriptase. In the development of drugs for the treatment of HIV infection, numerous tensions can be identified which need to be addressed to permit successful drug development in the future. These tensions include inherent conflicts between industry, government, regulatory authorities, academicians, and patients and as such need to be identified, discussed, and constructive solutions developed.

Anti-HIV Agents↗
PubMed1996

Population pharmacokinetics of ganciclovir in newborns with congenital cytomegalovirus infections. NIAID Collaborative Antiviral Study Group.

The population pharmacokinetics of ganciclovir was investigated in a group of 27 newborns with symptomatic congenital cytomegalovirus infection by nonlinear mixed-effects modeling analysis. Individual characteristics including approximated creatinine clearance from serum (ASCC) and body weight (WGE) were identified to significantly influence total clearance from plasma (CL) and the apparent total volume of distribution (V) of ganciclovir, respectively. The regression equations used to model these relationships were expressed as CL (in liters per hour) = 0.262 + (0.00271 x ASCC) and V (in liters) = 0.627 + (0.437 x WGE). By using this model, typical values of the pharmacokinetic parameter CL and V were 0.428 +/- 0.079 liters/h and 1.773 +/- 0.320 liters, respectively. Upon validation with a larger number of newborns, this model should allow for the definition of possible relationships between the pharmacokinetic disposition of ganciclovir and pharmacodynamic events in neonates.

Antiviral Agents↗
PubMed1996

The past as prelude to the future: history, status, and future of antiviral drugs.

OBJECTIVE: To review the first generation of antiviral agents (e.g., idoxuridine, amantadine, vidarabine) that paralleled discovery of antineoplastic agents. DATA SOURCES: A MEDLINE search (1962 to 1996) of the English-language literature pertaining to antiviral agents was performed. DATA EXTRACTION: All articles were considered for this review. Pertinent references on antiviral therapy, as judged by the author, were selected. DATA SYNTHESIS: Acyclovir, the first second-generation antiviral agent, has a known selective mechanism of action and provides the model for development of future antiviral therapies. Despite the safety and clinical value of acyclovir, therapy does not prevent establishment of latency or decrease frequency of occurrences, resistance has been documented, and outcome is frequently poor. With the emergence of the HIV/AIDS epidemic, several antiretroviral agents have been developed and approved. However, none of the four available nucleoside analogs provides a cure. CONCLUSIONS: Viral resistance has emerged as an important component of antiviral therapy. Improved therapies for cytomegalovirus are needed. Several new therapies for herpes zoster, including prodrugs, are licensed or in Phase III clinical trials. Future directions include the use of molecular biologic techniques to identify enzymes unique to viral replication and to accelerate diagnosis of viral diseases.

Acyclovir↗
PubMed1995

Comparison of genetically engineered herpes simplex viruses for the treatment of brain tumors in a scid mouse model of human malignant glioma.

Genetically engineered viruses and viral genes inserted into retroviral vectors are increasingly being considered for experimental therapy of brain tumors. A primary target of these viruses and vectors is human gliomas, the most frequently occurring primary human brain tumor. To investigate the potential of genetically engineered herpes simplex viruses (HSVs) in the therapy of these tumors, we compared the attributes of two viruses, a recombinant from which the gamma 1(34.5) gene had been deleted (R3616) and a recombinant in which the gamma 1(34.5) gene had been interrupted by a stop codon (R4009). Previous studies have shown that these recombinants were completely devoid of the ability to multiply in the central nervous system of rodents. To pursue these studies, we developed a scid mouse glioma model. Tumor cell response (survival) for 10(3), 10(4), and 10(5) implanted MT539MG glioma cells was 38, 23, and 15 days, respectively. The results were as follows: (i) both R3616 and R4009 replicate and cause cytolysis in diverse glioma cell lines of murine and human origin in vitro, and (ii) Winn-type assays 10(5) MT539MG cells coinoculated with R3616 or R4009 as compared to saline significantly prolonged survival in a dose-dependent fashion. Mice that received only tumor cells or the wild-type parent strain of the recombinants, HSV-1(F), died within 15 days. Survival was greatest with R4009. These experiments define both a model for screening oncolytic viruses and a genetically engineered virus of significant potential use as an oncolytic agent.

Animals↗