Anticytomegaloviral activity and safety of cidofovir in patients with human immunodeficiency virus infection and cytomegalovirus viruria

Mpox and HIV: a Narrative Review

PURPOSE OF REVIEW

We reviewed the available literature on mpox in People with HIV (PWH). We highlight special considerations of mpox infection related to epidemiology, clinical presentation, diagnostic and treatment considerations, prevention, and public health messaging in PWH.

RECENT FINDINGS

During the 2022 mpox outbreak, PWH were disproportionally impacted worldwide. Recent reports suggest that the disease presentation, management, and prognosis of these patients, especially those with advanced HIV disease, can widely differ from those without HIV-associated immunodeficiency. Mpox can often be mild and resolve on its own in PWH with controlled viremia and higher CD4 counts. However, it can be severe, with necrotic skin lesions and protracted healing; anogenital, rectal, and other mucosal lesions; and disseminated organ systems involvement. Higher rates of healthcare utilization are seen in PWH. Supportive, symptomatic care and single or combination mpox-directed antiviral drugs are commonly used in PWH with severe mpox disease. Data from randomized clinical control trials on the efficacy of therapeutic and preventive tools against mpox among PWH are needed to better guide clinical decisions.

Optimizing Antiviral Dosing for HSV and CMV Treatment in Immunocompromised Patients

Herpes simplex virus (HSV) and cytomegalovirus (CMV) are DNA viruses that are common among humans. Severely immunocompromised patients are at increased risk of developing HSV or CMV disease due to a weakened immune system. Antiviral therapy can be challenging because these drugs have a narrow therapeutic window and show significant pharmacokinetic variability. Above that, immunocompromised patients have various comorbidities like impaired renal function and are exposed to polypharmacy. This scoping review discusses the current pharmacokinetic (PK) and pharmacodynamic (PD) knowledge of antiviral drugs for HSV and CMV treatment in immunocompromised patients. HSV and CMV treatment guidelines are discussed, and multiple treatment interventions are proposed: early detection of drug resistance; optimization of dose to target concentration by therapeutic drug monitoring (TDM) of nucleoside analogs; the introduction of new antiviral drugs; alternation between compounds with different toxicity profiles; and combinations of synergistic antiviral drugs. This research will also serve as guidance for future research, which should focus on prospective evaluation of the benefit of each of these interventions in randomized controlled trials.

Fumaric acid ester-induced renal Fanconi syndrome: evidence of mitochondrial toxicity

Background

Fumaric acid esters (FAEs) are used to treat chronic plaque psoriasis. Fumarate is a crucial component of the Krebs cycle and mitochondrial function. Proximal tubule cells have high energy demands and rely on aerobic respiration. Proximal tubular dysfunction can cause renal Fanconi syndrome and acute kidney injury. We sought to better understand the mechanism for this in the context of FAE therapy.

Methods

We describe a case series of 10 patients with FAE-associated Fanconi syndrome. Patients were diagnosed and managed at a tertiary renal tubular disorder clinic, with examination of serum and urine biochemistry. Five patients had a renal biopsy with examination of the specimens by electron microscopy.

Results

The median age was 36.5 years [interquartile range (IQR) 32.25-54.25]. The median dose of FAE was 720 mg/day (IQR 390-720). There was low molecular weight proteinuria: the median urinary retinol-binding protein (RBP) at presentation was 8385 μg/mL (IQR 2793-14 600) and the RBP:creatinine ratio was 710 (IQR 390-2415). All patients had hyperphosphaturia [median fractional excretion of phosphate 24.2% (IQR 20.8-26.9), normal range <20%] as well as relative hypophosphataemia, with a median serum phosphate concentration of 0.93 mmol/L (IQR 0.83-0.97). Renal histology showed proximal tubular damage and abnormal mitochondrial morphology. Two patients had a favourable biochemical response to treatment with probenecid.

Conclusions

We document for the first time that FAE-associated renal Fanconi syndrome is associated with mitochondrial damage visible on electron microscopy. This effect may be ameliorated by antagonism of the organic anion transporter with probenecid.

Transporter-Mediated Drug-Drug Interactions and Their Significance

Drug transporters are considered to be determinants of drug disposition and effects/toxicities by affecting the absorption, distribution, and excretion of drugs. Drug transporters are generally divided into solute carrier (SLC) family and ATP binding cassette (ABC) family. Widely studied ABC family transporters include P-glycoprotein (P-GP), breast cancer resistance protein (BCRP), and multidrug resistance proteins (MRPs). SLC family transporters related to drug transport mainly include organic anion-transporting polypeptides (OATPs), organic anion transporters (OATs), organic cation transporters (OCTs), organic cation/carnitine transporters (OCTNs), peptide transporters (PEPTs), and multidrug/toxin extrusions (MATEs). These transporters are often expressed in tissues related to drug disposition, such as the small intestine, liver, and kidney, implicating intestinal absorption of drugs, uptake of drugs into hepatocytes, and renal/bile excretion of drugs. Most of therapeutic drugs are their substrates or inhibitors. When they are comedicated, serious drug-drug interactions (DDIs) may occur due to alterations in intestinal absorption, hepatic uptake, or renal/bile secretion of drugs, leading to enhancement of their activities or toxicities or therapeutic failure. This chapter will illustrate transporter-mediated DDIs (including food drug interaction) in human and their clinical significances.

Releasing the concept of HLA-allele specific peptide anchors in viral infections: A non-canonical naturally presented human cytomegalovirus-derived HLA-A*24:02 restricted peptide drives exquisite immunogenicity

T‐cell receptors possess the unique ability to survey and respond to their permanently modified ligands, self HLA‐I molecules bound to non‐self peptides of various origin. This highly specific immune function is impaired following hematopoietic stem cell transplantation (HSCT) for a timespan of several months needed for the maturation of T‐cells. Especially, the progression of HCMV disease in immunocompromised patients induces life‐threatening situations. Therefore, the need for a new immune system that delivers vital and potent CD8+ T‐cells carrying TCRs that recognize even one human cytomegalovirus (HCMV) peptide/HLA molecule and clear the viral infection long term becomes obvious. The transcription and translation of HCMV proteins in the lytic cycle is a precisely regulated cascade of processes, therefore, it is a highly sensitive challenge to adjust the exact time point of HCMV‐peptide recruitment over self‐peptides. We utilized soluble HLA technology in HCMV‐infected fibroblasts and sequenced naturally sHLA‐A*24:02 presented HCMV‐derived peptides. One peptide of 14 AAs length derived from the IE2 antigen induced the strongest T‐cell responses; this peptide can be detected with a low ranking score in general peptide prediction databanks. These results highlight the need for elaborate and HLA‐allele specific peptide selection.

Antiviral Therapies for Herpesviruses: Current Agents and New Directions

PURPOSE

The objective of this review was to summarize the recent literature describing the current burden of disease due to herpesviruses in the antiviral and transplant era; describe mechanisms of action of antiviral agents and the development of resistance; summarize the literature of recent antiviral agents brought to market as well as agents under development; and to present literature on future strategies for herpesvirus therapeutics.

METHODS

An extensive search of the medical literature related to antiherpesviral therapy was conducted to compose this narrative review. Literature searches were performed via PubMed and ultimately 137 articles were included as most relevant to the scope of this article.

FINDINGS

Herpesviruses are a family of DNA viruses that are ubiquitous throughout human populations and share the feature of establishing lifelong infections in a latent phase with the potential of periodic reactivation. With the exception of herpes simplex virus, varicella zoster virus, and Epstein-Barr virus, which have a significant disease burden in individuals with normal immune function, the morbidity and mortality of the remaining viruses are primarily associated with the immunocompromised host. Over the last half-century, several agents have been tested in large randomized, placebo-controlled trials that have resulted in safe and effective antiviral agents for the treatment of many of these infections.

IMPLICATIONS

With increasing use of antiherpesviral agents for extended periods, particularly in immunocompromised hosts, the emergence of resistant viruses has necessitated the development of newer agents with novel targets and better side-effect profiles.

Brincidofovir Is Not a Substrate for the Human Organic Anion Transporter 1: A Mechanistic Explanation for the Lack of Nephrotoxicity Observed in Clinical Studies

BACKGROUND

Brincidofovir (BCV) is an orally bioavailable lipid conjugate of cidofovir (CDV) with increased in vitro potency relative to CDV against all 5 families of double-stranded DNA viruses that cause human disease. After intravenous (IV) administration of CDV, the organic anion transporter 1 (OAT1) transports CDV from the blood into the renal proximal tubule epithelial cells with resulting dose-limiting nephrotoxicity.

OBJECTIVE

To study whether OAT1 transports BCV and to evaluate the pharmacokinetic and renal safety profile of oral BCV compared with IV CDV.

METHODS

The cellular uptake of BCV and its major metabolites was assessed in vitro. Renal function at baseline and during and after treatment in subjects in BCV clinical studies was examined.

RESULTS

In OAT1-expressing cells, uptake of BCV and its 2 major metabolites (CMX103 and CMX064) was the same as in mock-transfected control cells and was not inhibited by the OAT inhibitor probenecid. In human pharmacokinetic studies, BCV administration at therapeutic doses resulted in detection of CDV as a circulating metabolite; peak CDV plasma concentrations after oral BCV administration in humans were <1% of those observed after IV CDV administration at therapeutic doses. Analysis of renal function and adverse events from 3 BCV clinical studies in immunocompromised adult and pediatric subjects indicated little to no evidence of associated nephrotoxicity. Over 80% of subjects who switched from CDV or foscarnet to BCV experienced an improvement in renal function as measured by maximum on-treatment estimated glomerular filtration rate.

CONCLUSIONS

The lack of BCV uptake through OAT1, together with lower CDV concentrations after oral BCV compared with IV CDV administration, likely explains the superior renal safety profile observed in immunocompromised subjects receiving BCV compared with CDV.

HPMPC (cidofovir), PMEA (adefovir) and Related Acyclic Nucleoside Phosphonate Analogues: A Review of their Pharmacology and Clinical Potential in the Treatment of Viral Infections

The acyclic nucleoside phosphonate (ANP) analogues are broad-spectrum antiviral agents, with potent and selective antiviral activity in vitro and in vivo. The prototype compounds are: ( S)-1-(3-hydroxy-2-phosphonylmethoxypropyl)cytosine (HPMPC, cidofovir), which is active against a wide variety of DNA viruses; 9-(2-phosphonylmethoxyethyl)adenine (PMEA, adefovir), which is active against retro-, herpes- and hepadnaviruses, and ( R)-9-(2-phosphonylmethoxypropyl) adenine (PMPA), which is active against retro- and hepadnaviruses. The antiviral action of the ANP analogues is based on a specific interaction of the active diphosphorylated metabolite with the viral DNA polymerase. The long intracellular half-life of the active metabolite accounts for the optimal efficacy in infrequent dosing schedules. The potential of HPMPC as a broad-spectrum anti-DNA virus agent, as originally observed in vitro and in vivo, has been confirmed in clinical trials. HPMPC has recently been commercially released in the USA for the treatment of cytomegalovirus retinitis in AIDS patients. In addition, topical systemic HPMPC is being (or will be) explored for use against other herpesviruses (i.e. herpes simplex virus, Epstein-Barr virus, or varicella-zoster virus), by adenoviruses, or by human papilloma- or polyomaviruses. Intravenous HPMPC is associated with dose-dependent nephrotoxicity, that should be counteracted by prehydration and concomitant administration of probenecid, and by the application of an infrequent dosing schedule. The oral prodrug of PMEA, bis(pivaloyloxymethyl)-PMEA, is currently being evaluated in patients infected with human immunodeficiency virus (HIV) or hepatitis B virus. Finally, preclinical data on the efficacy of PMPA in animal retrovirus models point to its potential usefulness against HIV infections, when given either prophylactically or therapeutically in the treatment of established HIV infections.

Cidofovir, a New Agent with Potent Anti-Herpesvirus Activity

Cidofovir is a potent, broad spectrum antiviral agent with activity in vitro and in vivo against cytomegalovirus and other members of the herpesvirus family, as well as certain other DNA viruses. After uptake into cells it is converted enzymatically to cidofovir diphosphate, a structural analogue of deoxycytidine triphosphate, which selectively inhibits viral DNA polymerases relative to host cell polymerases. Cross-resistance to cidofovir is not usually seen with human cytomegalovirus isolates that are foscarnet-resistant, or isolates that are ganciclovir-resistant due to a deficiency in ganciclovir phosphorylation. Cross-resistance is seen, however, with isolates that are ganciclovir resistant due to polymerase mutations. A prolonged elimination phase seen in vivo, correlates with a long intracellular half-life seen in vitro and allows for efficacy in animal models of virus infection with infrequent dosing or prophylaxis. Clinical studies of intravenous cidofovir in cytomegalovirus retinitis in patients with AIDS are claimed to show delay of retinitis progression with maintenance doses given once every 2 weeks.

Enhanced efficacy of cidofovir combined with vaccinia immune globulin in treating progressive cutaneous vaccinia virus infections in immunosuppressed hairless mice

The treatment of progressive vaccinia in individuals has involved antiviral drugs, such as cidofovir (CDV), brincidofovir, and/or tecovirimat, combined with vaccinia immune globulin (VIG). VIG is costly, and its supply is limited, so sparing the use of VIG during treatment is an important objective. VIG sparing was modeled in immunosuppressed mice by maximizing the treatment benefits of CDV combined with VIG to determine the effective treatments that delayed the time to death, reduced cutaneous lesion severity, and/or decreased tissue viral titers. SKH-1 hairless mice immunosuppressed with cyclophosphamide and hairless SCID mice (SHO strain) were infected cutaneously with vaccinia virus. Monotherapy, dual combinations (CDV plus VIG), or triple therapy (topical CDV, parenteral CDV, and VIG) were initiated 2 days postinfection and were given every 3 to 4 days through day 11. The efficacy assessment included survival rate, cutaneous lesion severity, and viral titers. Delays in the time to death and the reduction in lesion severity occurred in the following order of efficacy: triple therapy had greater efficacy than double combinations (CDV plus VIG or topical plus parenteral CDV), which had greater efficacy than VIG alone. Parenteral administration of CDV or VIG was necessary to suppress virus titers in internal organs (liver, lung, and spleen). The skin viral titers were significantly reduced by triple therapy only. The greatest efficacy was achieved by triple therapy. In humans, this regimen should translate to a faster cure rate, thus sparing the amount of VIG used for treatment.

Potential of acyclic nucleoside phosphonates in the treatment of DNA virus and retrovirus infections

The acyclic nucleoside phosphonates [HPMPC: cidofovir, Vistide; PMEA: adefovir dipivoxil, Hepsera; and PMPA: tenofovir, Viread] have proven to be effective in vitro (cell culture systems) and in vivo (animal models and clinical studies) against a wide variety of DNA virus and retrovirus infections, for example, cidofovir against herpesvirus [herpes simplex virus type 1 and 2, varicella-zoster virus, cytomegalovirus, Epstein-Barr virus, human herpesvirus type 6, 7 and 8), polyoma-, papilloma-, adeno- and poxvirus (variola virus, cowpox virus, vaccinia virus, molluscum contagiosum virus and orf) infections; adefovir against herpesvirus, hepadnavirus [human hepatitis B virus] and retrovirus [HIV type-1 and 2, simian immunodeficiency virus and feline immunodeficiency virus] infections; and tenofovir against both hepadna- and retrovirus infections. Cidofovir has been officially approved for the treatment of cytomegalovirus retinitis in AIDS patients, tenofovir disoproxil fumarate (Viread) for the treatment of HIV infections (i.e., AIDS) and adefovir dipivoxil for the treatment of chronic hepatitis B.

Histopathologic resolution of adult liver transplantation adenovirus hepatitis with cidofovir and intravenous immunoglobulin: a case report

Adenovirus (ADV) infections in adult solid organ transplant recipients, although rare, are associated with high mortality. There are no randomized controlled trials establishing the efficacy of specific treatment modalities. To our knowledge apparent response to treatment with combination therapy with intravenous cidofovir (CDV) and immunoglobulin (IVIG) has only been demonstrated in 2 adult renal transplant recipients in whom ADV was documented in body fluids only. We describe an adult liver transplant recipient diagnosed with ADV hepatitis based on positive immunohistochemical staining of a liver biopsy specimen, positive blood ADV DNA polymerase chain reaction (PCR), and treated with the combination of CDV and IVIG. We demonstrated both clearance of viremia and histopathologic resolution of the hepatitis despite the patient's fatal outcome. To our knowledge this is the only case documenting eradication of tissue-invasive ADV disease in any solid organ transplant recipient using CDV and IVIG. This case provides evidence to support the use of this drug combination, which has many potential toxicities that might discourage its use otherwise.

Combination of probenecid-sulphadoxine-pyrimethamine for intermittent preventive treatment in pregnancy

The antifolate sulphadoxine-pyrimethamine (SP) has been used in the intermittent prevention of malaria in pregnancy (IPTp). SP is an ideal choice for IPTp, however, as resistance of Plasmodium falciparum to SP increases, data are accumulating that SP may no longer provide benefit in areas of high-level resistance. Probenecid was initially used as an adjunctive therapy to increase the blood concentration of penicillin; it has since been used to augment concentrations of other drugs, including antifolates. The addition of probenecid has been shown to increase the treatment efficacy of SP against malaria, suggesting that the combination of probenecid plus SP may prolong the useful lifespan of SP as an effective agent for IPTp. Here, the literature on the pharmacokinetics, adverse reactions, interactions and available data on the use of these drugs in pregnancy is reviewed, and the possible utility of an SP-probenecid combination is discussed. This article concludes by calling for further research into this potentially useful combination.

Evaluation of imiquimod for topical treatment of vaccinia virus cutaneous infections in immunosuppressed hairless mice

Imiquimod is an immune response modifier prescribed as a topical medication for a number of viral and neoplastic conditions. We evaluated the antiviral activity of imiquimod against vaccinia virus (WR strain) cutaneous infections in immunosuppressed (with cyclophosphamide) hairless mice when administered after virus exposure. Primary lesions progressed in severity, satellite lesions developed, and infection eventually killed the mice. Once daily topical treatment with 1% imiquimod cream for 3, 4, or 5 days were compared to twice daily topical treatment with 1% cidofovir cream for 7 days. Survival time of mice in all treated groups was significantly prolonged compared to placebo controls. The mean day of death for the placebo group, 3-day imiquimod, 4-day imiquimod, 5-day imiquimod, and cidofovir groups were 15.5, 20.0, 20.5, 19.5, and 20.5 days post-infection, respectively. All treatment groups showed significant reductions in primary lesion size and in the number of satellite lesions. The cidofovir and 4-day imiquimod treatments delayed the appearance of lung virus titers by 3 and 6 days, respectively, although cutaneous lesion and snout virus titers were not as affected by treatment. Benefits in survival and lesion reduction were observed when imiquimod treatment was delayed from 24, 48, and 72 h post-infection. However, increasing the treatment dose of imiquimod from 1% to 5% led to a significant decrease in antiviral efficacy. These results demonstrate the protective effects of topically administered imiquimod against a disseminated vaccinia virus infection in this mouse model.

Cidofovir Activity against Poxvirus Infections

Cidofovir [(S)-1-(3-hydroxy-2-phosphonylmethoxypropyl)cytosine, HPMPC] is an acyclic nucleoside analog approved since 1996 for clinical use in the treatment of cytomegalovirus (CMV) retinitis in AIDS patients. Cidofovir (CDV) has broad-spectrum activity against DNA viruses, including herpes-, adeno-, polyoma-, papilloma- and poxviruses. Among poxviruses, cidofovir has shown in vitro activity against orthopox [vaccinia, variola (smallpox), cowpox, monkeypox, camelpox, ectromelia], molluscipox [molluscum contagiosum] and parapox [orf] viruses. The anti-poxvirus activity of cidofovir in vivo has been shown in different models of infection when the compound was administered either intraperitoneal, intranasal (aerosolized) or topically. In humans, cidofovir has been successfully used for the treatment of recalcitrant molluscum contagiosum virus and orf virus in immunocompromised patients. CDV remains a reference compound against poxviruses and holds potential for the therapy and short-term prophylaxis of not only orthopox- but also parapox- and molluscipoxvirus infections.

Adenovirus infections in solid organ transplant recipients

PURPOSE OF REVIEW

Adenoviruses are emerging as important viral pathogens in solid organ transplant recipients, impacting morbidity, graft survival and even mortality. This review will discuss the current understanding of the epidemiology, diagnosis and therapy of adenovirus infection in transplant recipients.

RECENT FINDINGS

Advances in the field include the use of polymerase chain reaction in the diagnosis of adenoviral infection, a better understanding of the epidemiology, immune response and potential new therapies, including preemptive and adoptive immunotherapy strategies. Adenoviral infections appear to be common, especially in pediatric solid organ transplant. Generally well tolerated, some high-risk patients may develop disseminated disease causing graft failure, which may lead to retransplant and/or death. Antiviral therapy and immunotherapy may play a role in these patients, although prospective controlled data are not available at this time.

SUMMARY

Although new tools and a better understanding of the epidemiology, risk factors and therapies for adenovirus are beginning to materialize, prospective, controlled trials, using careful definitions, and standardized methodologies need to be performed to more fully clarify these issues in solid organ transplant recipients.

Antiretroviral medications: adverse effects on the kidney

The widespread introduction of highly active antiretroviral therapy (HAART) in the mid-1990s dramatically altered the course of human immunodeficiency virus (HIV) infection, with improvements in survival and reductions in the incidence of AIDS-defining illnesses. Although antiretroviral therapy has been shown to reduce the incidence of both AIDS-defining and non-AIDS conditions, long-term exposure to HAART may also be associated with significant toxicity. This article reviews the potential nephrotoxicity of specific antiretroviral agents and the impact of antiretroviral therapy on related metabolic disorders. The antiretroviral agents most strongly associated with direct nephrotoxicity include the nucleotide reverse transcriptase inhibitor, tenofovir, and the protease inhibitor indinavir, although other agents have been implicated less frequently. Tenofovir and related nucleotide analogs have primarily been associated with proximal tubular dysfunction and acute kidney injury, whereas indinavir is known to cause nephrolithiasis, obstructive nephropathy, and interstitial nephritis. Kidney damage related to antiretroviral therapy is typically reversible with early recognition and timely discontinuation of the offending agent, and nephrologists should be familiar with the potential toxicity of these agents to avoid delays in diagnosis.

Hypophosphataemia: An Easy Strategy for Diagnosis and Treatment in HIV Patients

Because HIV infection has become a chronic disease, it is crucial that metabolic complications secondary to HIV infection or prolonged therapy be diagnosed and managed appropriately over time. Therefore the optimal follow-up becomes complex and time consuming. Our review aimed to provide physicians in charge of HIV-infected patients with key data helping them to diagnose and understand hypophosphataemia in HIV patients. Hypophosphataemia is frequent and sometimes secondary to renal phosphate wasting. It is very rarely a component of a complex proximal tubular disorder, such as Fanconi syndrome. When isolated, hypophosphataemia is easy to rule out and treat. In rare cases, prolonged hypophosphataemia, when related to renal phosphate wasting and tubular dysfunction, might have potential consequences on bone outcome, however, more studies are needed. HIV infection by itself might be a risk factor for bone metabolism abnormalities; antiretroviral drugs might also be involved. Therefore, it seems valuable for patients that the minimal screening should be performed routinely, in order to prevent long-term disabilities.

Pivotal role of animal models in the development of new therapies for cytomegalovirus infections

Since human cytomegalovirus (CMV) is extremely species specific and does not replicate in experimental animal tissues, animal models for the evaluation of antiviral agents for these infections have utilized surrogate animal viruses including murine CMV, rat CMV and guinea pig CMV. Murine CMV and rat CMV infections in normal and immunocompromised animals provide models of disseminated infection and are ideal for screening of new agents. While guinea pig CMV infection in immunocompromised animals also provides a model for disseminated disease, the model for congenital CMV is unique among all the experimental models. While these models have played a major role in the development of ganciclovir, foscarnet and cidofovir, they do not provide information directly related to human CMV, nor are they useful for evaluation of agents that are active only against human CMV. The SCID-hu mouse models in which human tissue is infected with human CMV has been very useful in the development of new antiviral agents such as maribavir and cyclopropavir. Collectively these experimental CMV infections provide a variety of models representing various aspects of CMV infection in humans that are highly predictive for antiviral efficacy in humans.

Antiretroviral therapy and the kidney: balancing benefit and risk in patients with HIV infection

The widespread introduction of highly active antiretroviral therapy (HAART) has revolutionised the treatment and course of HIV infection, with complications of chronic HIV infection and HAART playing an increasingly important role in morbidity and mortality. Both HIV infection and HAART have been associated with the development of acute and chronic kidney disease. The incidence of HIV-associated nephropathy, the classic kidney disease of HIV, reached a plateau following the introduction of HAART, consistent with the pathogenic role of direct viral infection of the kidney. At the same time, antiretroviral agents and related therapies have demonstrated a range of nephrotoxic effects, including crystal-induced obstruction, lactic acidosis, tubular toxicity, interstitial nephritis and electrolyte abnormalities. This article reviews the impact of HAART on the epidemiology of HIV-related kidney disease, the potential nephrotoxicity of specific antiretroviral agents and related medications, and guidelines for monitoring kidney function in HAART-treated patients.

Adenoviral disease in pediatric solid organ transplant recipients

Adenoviral disease in pediatric SOT recipients is emerging as an important viral pathogen, with serious consequences impacting morbidity, mortality and graft survival. The optimal diagnostic techniques, as well as therapy have yet to be established. This article reviews the current epidemiology of AdV in orthotopic liver, intestinal, cardiothoracic and renal transplant recipients. Issues related to diagnosis, notably the use of newer non-culture based viral detection methods and therapy, including anti-adenoviral agents and adoptive immunotherapy are discussed.

Synthesis and Antiviral Evaluation of Polyhalogenated Imidazole Nucleosides: Dimensional Analogues of 2,5,6-Trichloro-1-(β-d-ribofuranosyl)benzimidazole

A series of polyhalogenated imidazole nucleosides were designed and synthesized as ring-contracted analogues of 2,5,6-trichloro-1-(beta-D-ribofuranosyl)benzimidazole (TCRB) and its 2-bromo analogue (BDCRB) in an effort to explore the spatial limitation of the active pocket(s) in the target protein(s). 2,4,5-Trichloro-, 2-bromo-4,5-dichloro-, and 2,4,5-tribromoimidazole nucleosides were prepared by a condensation of the preformed heterocycles with the appropriate sugar precursors. The ribofuranosyl and xylofuranosyl analogues were prepared by a direct glycosylation using the Vorbruggen's silylation method and provided exclusively the beta-anomers. The arabinofuranosyl analogues were prepared by the sodium salt method to give both the alpha- and beta-anomers. The absolute configurations were established by 1H NMR spectroscopy. Alkylation of the polyhalogenated imidazoles with the appropriate bromomethyl ethers gave the acyclic acyclovir and ganciclovir analogues. In general, the parent polyhalogenated imidazoles showed some activity against human cytomegalovirus (HCMV) (IC50 approximately 35 microM). However, with the exception of two tribromo analogues (7c, 13c-beta), most of their nucleoside derivatives were inactive against both HCMV and herpes simplex virus type-1 (HSV-1) and were not cytotoxic. The results suggest that the ring-contracted nucleoside analogues of TCRB and BDCRB interacted weakly or not at all with viral and cellular targets.

Rhesus cytomegalovirus is similar to human cytomegalovirus in susceptibility to benzimidazole nucleosides

Rhesus and human cytomegalovirus (RhCMV and HCMV, respectively) exhibit comparable inhibition by benzimidazole nucleosides, including 2,5,6-trichloro-(1-beta-d-ribofuranosyl)benzimidazole (TCRB), and pyrrolo[2,3-d]pyrimidines. The two HCMV protein targets of TCRB, UL89 and UL56, are highly conserved with their RhCMV homologues. These data indicate that infection of rhesus macaques with RhCMV represents a useful model to test novel anti-HCMV drugs.

Clinical potential of the acyclic nucleoside phosphonates cidofovir, adefovir, and tenofovir in treatment of DNA virus and retrovirus infections

The acyclic nucleoside phosphonates HPMPC (cidofovir), PMEA (adefovir), and PMPA (tenofovir) have proved to be effective in vitro (cell culture systems) and in vivo (animal models and clinical studies) against a wide variety of DNA virus and retrovirus infections: cidofovir against herpesvirus (herpes simplex virus types 1 and 2 varicella-zoster virus, cytomegalovirus [CMV], Epstein-Barr virus, and human herpesviruses 6, 7, and 8), polyomavirus, papillomavirus, adenovirus, and poxvirus (variola virus, cowpox virus, vaccinia virus, molluscum contagiosum virus, and orf virus) infections; adefovir against herpesvirus, hepadnavirus (human hepatitis B virus), and retrovirus (human immunodeficiency virus types 1 [HIV-1] and 2 [HIV-2], simian immunodeficiency virus, and feline immunodeficiency virus) infections; and tenofovir against both hepadnavirus and retrovirus infections. Cidofovir (Vistide) has been officially approved for the treatment of CMV retinitis in AIDS patients, tenofovir disoproxil fumarate (Viread) has been approved for the treatment of HIV infections (i.e., AIDS), and adefovir dipivoxil (Hepsera) has been approved for the treatment of chronic hepatitis B. Nephrotoxicity is the dose-limiting side effect for cidofovir (Vistide) when used intravenously (5 mg/kg); no toxic side effects have been described for adefovir dipivoxil and tenofovir disoproxil fumarate, at the approved doses (Hepsera at 10 mg orally daily and Viread at 300 mg orally daily).

Comparison of HSV-1 thymidine kinase-dependent and -independent inhibition of replication-competent adenoviral vectors by a panel of drugs

Replication-competent adenoviral vectors hold the promise to be more efficient gene delivery vehicles than their replication-deficient counterparts, but they are also associated with a higher risk for adverse effects, especially in light of the fact that there is no established effective therapy for serious, disseminated adenovirus infection. To assess whether the therapeutic options to inhibit adenoviral replication can be enhanced by expressing a suicide gene, we examined the antiadenoviral effects of 15 drugs against wild-type adenovirus type 5 (Ad5) and an Ad5-based replication-competent vector expressing herpes simplex virus-1 thymidine kinase (HSV-tk) (Ad.OW34) using a real-time polymerase chain reaction -based assay and flow cytometry. Ad5 and Ad.OW34 were highly susceptible to the fluorinated pyrimidine analogs 5-fluoro-2'-deoxyuridine (FUdR), 5-fluorouridine (FUR), and trifluorothymidine (TFT), with a mean 50% inhibitory concentration (IC(50)) ranging from 0.12 to 0.32 microM. The mean IC(50) of ribavirin and cidofovir (CDV) for Ad5, the most frequently used drugs to treat adenovirus disease, was 6.87 and 3.19 microM, respectively. In contrast to Ad5, the Ad.OW34 vector was susceptible to (E)-5-(2-bromovinyl)-2'-deoxyuridine (BVdU, IC(50) 0.09 microM), ganciclovir (GCV, IC(50) 0.19 microM), and acyclovir (ACV, IC(50) 32.04 microM). Additionally, we demonstrated in an animal model that Ad.OW34 vector replication can be inhibited significantly by GCV, CDV, and TFT by 35.2, 7.7, and 3.7-fold, respectively, compared to untreated animals. The observed antiadenoviral effects were primarily not through cell killing, since the in vitro 50% cytotoxic concentrations (CC(50)) were more than 1000 times higher than the antiadenoviral IC(50) of the drugs examined, even in cells stably expressing HSV-tk. Since for HSV-tk-dependent inhibition of adenoviral vectors, stability of HSV-tk expression is crucial, we examined Ad.OW34 vector stability, by passaging the vector 10 times serially in the presence of 10 microM GCV. The HSV-tk/GCV system neither changed the susceptibility of Ad.OW34 to GCV significantly nor detectable vector rearrangements occurred, suggesting that the system might be suitable as a fail-safe mechanism to stop adenoviral vector replication.

Current and potential therapies for the treatment of herpes-virus infections

Human herpesviruses are found worldwide and are among the most frequent causes of viral infections in immunocompetent as well as in immunocompromised patients. During the past decade and a half a better understanding of the replication and disease-causing state of herpes simplex virus types 1 and 2 (HSV-1 and HSV-2), varicella zoster virus (VZV), and human cytomegalovirus (HCMV) has been achieved due in part to the development of potent antiviral compounds that target these viruses. While some of these antiviral therapies are considered safe and efficacious (acyclovir, penciclovir), some have toxicities associated with them (ganciclovir and foscarnet). In addition, the increased and prolonged use of these compounds in the clinical setting, especially for the treatment of immunocompromised patients, has led to the emergence of viral resistance against most of these drugs. While resistance is not a serious issue for immunocompetent individuals, it is a real concern for immunocompromised patients, especially those with AIDS and the ones that have undergone organ transplantation. All the currently approved treatments target the viral DNA polymerase. It is clear that new drugs that are more efficacious than the present ones, are not toxic, and target a different viral function would be of great use especially for immunocompromised patients. Here, an overview is provided of the diseases caused by the herpesviruses as well as the replication strategy of the better studied members of this family for which treatments are available. We also discuss the various drugs that have been approved for the treatment of some herpesviruses in terms of structure, mechanism of action, and development of resistance. Finally, we present a discussion of viral targets other than the DNA polymerase, for which new antiviral compounds are being considered.

The human cytomegalovirus

Human cytomegalovirus (HCMV), a betaherpesvirus, represents the major infectious cause of birth defects, as well as an important pathogen for immunocompromised individuals. The viral nucleocapsid containing a linear double-stranded DNA of 230 kb is surrounded by a proteinaceous tegument, which is itself enclosed by a loosely applied lipid bilayer. Expression of the HCMV genome is controlled by a cascade of transcriptional events that leads to the synthesis of three categories of viral proteins designated as immediate-early, early, and late. Clinical manifestations can be seen following primary infection, reinfection, or reactivation. About 10% of infants are infected by the age of 6 months following transmission from their mothers via the placenta, during delivery, or by breastfeeding. HCMV is a significant post-allograft pathogen and contributes to graft loss independently from graft rejection. Histopathologic examination of necropsy tissues demonstrates that the virus enters via the epithelium of the upper alimentary, respiratory, or genitourinary tracts. Hematogenous spreading is typically followed by infection of ductal epithelial cells. Infections are kept under control by the immune system. However, total HCMV clearance is rarely achieved, and the viral genome remains at selected sites in a latent state. Virological and molecular detection of HCMV, as well as serological demonstration of a specific immune response, are used for diagnosis. Treatment of HCMV infections is difficult because there are few options. The presently available drugs produced a significant clinical improvement, but suffer from poor oral bioavailability, low potency, development of resistance in clinical practice, and dose-limiting toxicities.

Pharmacokinetics and renal effects of cidofovir with a reduced dose of probenecid in HIV-infected patients with cytomegalovirus retinitis

To reduce possible nephrotoxicity, intravenous prehydration with normal saline and administration of probenecid must be used with each infusing of the antiviral cidofovir. The recommended standard-dose probenecid (SDP) regimen is 2 g at 3 hours before cidofovir, then 1 g at 2 and 8 hours after cidofovir (total 4 g). A new regimen of reduced-dose probenecid (RDP), 2 g at 1 hour before cidofovir without additional probenecid administrations after infusion (total 2 g), was compared with SDP using a randomized, open-label, parallel design. A single dose of cidofovir (5 mg/kg) was given as a 1-hour infusion after saline prehydration to 24 HIV-infected patients (11 males, 13 females) with cytomegalovirus retinitis and good renal function. Blood was sampled for 48 hours and urine for 24 hours after the start of the cidofovir infusion. Cidofovir pharmacokinetics did not differ significantly between groups. Average key pharmacokinetic parameters (Cmax, tmax, lambda z, AUC0-infinity, Vss, CL, CLR, fe, ER) for RDP differed by less than 17% from SDP and were consistent with previously reported SDP data. Renal function parameters, other safety endpoints, and adverse events were similar between the groups. Therefore, the reduced-dose regimen of probenecid provided renal protection after a single dose of cidofovir and did not alter the pharmacokinetics of cidofovir in patients with moderately good renal function. Although the overall pharmacokinetic results do not show a significant difference in cidofovir exposure with the new probenecid regimen, the main issue of safety of the new dose regimen, both relating to renal toxicity and probenecid-related adverse events, is not adequately addressed in a small study.

Antiviral therapy for cytomegalovirus infections in pediatric patients

Appreciation of the spectrum of illness caused by cytomegalovirus (CMV) infections has increased markedly during the past 2 decades. The number of immunosuppressed patients also has increased during the same time period, reflecting the central tenet that CMV disease is most severe in this patient population. Fortunately, antiviral therapies with activity against CMV also have been identified during this same time course, and they include ganciclovir, foscamet, and cidofovir. Although all 3 of these therapies can have significant toxicities associated with them, nonetheless they are employed with relative frequency to treat potentially life-threatening CMV disease. Ganciclovir is the first-line compound used, followed by foscarnet and cidofovir. This article summarizes those CMV infections that require antiviral therapy and outlines therapeutic options for each.

Inhibition of ganciclovir-susceptible and -resistant human cytomegalovirus clinical isolates by the benzimidazole L-riboside 1263W94

The average 50% inhibitory concentration (IC(50)) values for AD169 were 0.22 +/- 0.09 microM 1263W94 and 5.36 +/- 0.12 microM ganciclovir. For 35 human cytomegalovirus (HCMV) clinical isolates the average IC(50) was 0.42 +/- 0.09 microM 1263W94, and for 26 ganciclovir-susceptible HCMV clinical isolates the average IC(50) was 3.78 +/- 1.62 microM ganciclovir. Nine HCMV clinical isolates that were resistant to ganciclovir were completely susceptible to 1263W94.

Susceptibilities of human cytomegalovirus clinical isolates to BAY38-4766, BAY43-9695, and ganciclovir

BAY38-4766 and BAY43-9695 are nonnucleosidic compounds with activities against human cytomegalovirus (HCMV). Two phenotypic assays were used to determine the drug susceptibilities of 36 HCMV clinical isolates to the BAY compounds and ganciclovir. Using either assay, both BAY compounds at a concentration of approximately 1 microM inhibited the replication of all 36 HCMV clinical isolates, including 11 ganciclovir-resistant clinical isolates, by 50%.

Current and potential therapies for the treatment of herpesvirus infections

Human herpesviruses are found worldwide and are among the most frequent causes of viral infections in immunocompetent as well as in immunocompromised patients. During the past decade and a half a better understanding of the replication and disease causing state of herpes simplex virus types 1 and 2 (HSV-1 and HSV-2), varicella-zoster virus (VZV), and human cytomegalovirus (HCMV) has been achieved due in part to the development of potent antiviral compounds that target these viruses. While some of these antiviral therapies are considered safe and efficacious (acyclovir, penciclovir), some have toxicities associated with them (ganciclovir and foscarnet). In addition, the increased and prolonged use of these compounds in the clinical setting, especially for the treatment of immunocompromised patients, has led to the emergence of viral resistance against most of these drugs. While resistance is not a serious issue for immunocompetent individuals, it is a real concern for immunocompromised patients, especially those with AIDS and the ones that have undergone organ transplantation. All the currently approved treatments target the viral DNA polymerase. It is clear that new drugs that are more efficacious than the present ones, are not toxic, and target a different viral function would be of great use especially for immunocompromised patients. Here, we provide an overview of the diseases caused by the herpesviruses as well as the replication strategy of the better studiedmembers of this family for which treatments are available. We also discuss the various drugs that have been approved for the treatment of some herpesviruses in terms of structure, mechanism of action, and development of resistance. Finally, we present a discussion of viral targets other than the DNA polymerase, for which new antiviral compounds are being considered.

Synthesis of N-alkyl substituted indolocarbazoles as potent inhibitors of human cytomegalovirus replication

The synthesis and antiviral evaluation of unsymmetrical indolocarbazole derivatives of Arcyriaflavin A, substituted with a range of alkyl groups at the indole nitrogen, is described. Structure-activity relationships in this series against human cytomegalovirus (HCMV) replication in cell culture are reported. Compound 4b was identified as potent inhibitor of HCMV (IC(50)=19 nM), which retained activity against a range of HCMV strains including ganciclovir resistant isolates.

Cytomegalovirus treatment options in immunocompromised patients

Cytomegalovirus (CMV) infection was recognised in congenitally infected infants in the first half of the 20th century. Following the increased use of immunosuppressive regimens for bone marrow and solid organ transplantation, various manifestations of CMV disease were recognised. Milder symptoms included fever, anorexia and malaise but severe symptoms included pneumonitis, hepatitis, gastrointestinal ulceration, choreoretinitis and encephalopathy, all with a high morbidity or mortality. With the onset of the AIDS epidemic, manifestations of CMV became evident, predominantly retinitis. Ganciclovir used intravenously has been the principal anti-CMV agent investigated. However, ganciclovir has problems with suboptimal efficacy, toxicity, poor oral bioavailability and evolution of resistant strains. Additional studies have been performed on foscarnet and cidofovir, although the use of both have been limited by their nephrotoxicity. Combination therapy with ganciclovir and foscarnet for resistant strains has been used. There are promising newer drugs like the methylenecyclopropane nucleoside analogues and benzimidazole. The most novel compound is the antisense oligonucleotide fomivirsen that has been evaluated principally in CMV retinitis. The role of immunotherapy with either immunoglobulin prophylaxis or the novel adoptive immunotherapy needs further evaluation.

Current and potential therapies for the treatment of herpesvirus infections

Human herpesviruses are found worldwide and are among the most frequent causes of viral infections in immunocompetent as well as in immunocompromised patients. During the past decade and a half a better understanding of the replication and disease causing state of herpes simplex virus types 1 and 2 (HSV-1 and HSV-2), varicella-zoster virus (VZV), and human cytomegalovirus (HCMV) has been achieved due in part to the development of potent antiviral compounds that target these viruses. While some of these antiviral therapies are considered safe and efficacious (acyclovir, penciclovir), some have toxicities associated with them (ganciclovir and foscarnet). In addition, the increased and prolonged use of these compounds in the clinical setting, especially for the treatment of immunocompromised patients, has led to the emergence of viral resistance against most of these drugs. While resistance is not a serious issue for immunocompetent individuals, it is a real concern for immunocompromised patients, especially those with AIDS and the ones that have undergone organ transplantation. All the currently approved treatments target the viral DNA polymerase. It is clear that new drugs that are more efficacious than the present ones, are not toxic, and target a different viral function would be of great use especially for immunocompromised patients. Here, we provide an overview of the diseases caused by the herpesviruses as well as the replication strategy of the better studied members of this family for which treatments are available. We also discuss the various drugs that have been approved for the treatment of some herpesviruses in terms of structure, mechanism of action, and development of resistance. Finally, we present a discussion of viral targets other than the DNA polymerase, for which new antiviral compounds are being considered.

Cyclic HPMPC is safe and effective against systemic guinea pig cytomegalovirus infection in immune compromised animals

Cidofovir (HPMPC) is licensed for the treatment of cytomegalovirus (CMV) retinitis in patients with AIDS but its use is limited by nephrotoxicity. We evaluated the safety and efficacy of 1-[((s)-2-hydroxy-2-oxo-1,4,2-dioxaphosphorinan-5-yl)methyl]cytosi ne dihydrate (CHPMPC) the cyclic congener of cidofovir. Treatment was well tolerated both in normal guinea pigs and in animals immune compromised with cyclophosphamide. Further, blood chemistry analysis showed no adverse effects of CHPMPC treatment on kidney or liver function. In efficacy studies in immune compromised guinea pigs challenged with a virulent salivary gland passaged guinea pig CMV, CHPMPC treatment significantly reduced mortality resulting from disseminated virus infection. Quantitative culture showed that treatment also significantly reduced virus replication in the liver and spleen, but not the lungs of infected animals. The efficacy of CHPMPC combined with its improved safety profile appear to make it an attractive alternative to cidofovir for the treatment of herpesvirus infections. Further evaluation is warranted.

Treatment of cowpox virus respiratory infections in mice with ribavirin as a single agent or followed sequentially by cidofovir

To better understand the potential of ribavirin in the treatment of orthopoxvirus infections (such as those acquired through bioterrorist activities), the efficacy of the drug was studied in a cowpox respiratory infection model in mice under varying disease severity. Mice did not survive a high intranasal cowpox virus challenge [3 x 10(6) plaque forming units (pfu)/animal] treated with subcutaneous ribavirin (100 mg/kg/day for 5 days), but lived 3.9 days longer than placebos. In contrast, 100% of animals receiving the same dose of drug survived a 3 x 10(5) pfu challenge compared with 0% survival of those that received placebo. Survival rates of 50 and 30% occurred with ribavirin doses of 50 and 25 mg/kg/day, respectively. At the 100 mg/kg/day dose, ribavirin reduced lung virus titres 40-fold on day 6 of the infection relative to titres in the placebo group. Weight loss resulting from illness and mean lung weights of mice treated with ribavirin were also significantly reduced. Mice were infected intranasally with the high 3 x 10(6) pfu virus challenge dose and treated with 100 mg/kg/day ribavirin for 5 days, followed by single injections of 75 mg/kg cidofovir on day 6, 7, 8 or 9. Cidofovir alone (without ribavirin) administered on day 6 had no beneficial effect on disease outcome. Ribavirin alone increased the mean time to death by 3.7 days. Ribavirin treatment for 5 days followed by cidofovir treatment on days 6 and 7 significantly increased the mean time to death beyond that achieved with ribavirin alone by 8.2 and 4.4 days, respectively, with 30 and 40% of mice surviving the infection. These results suggest that many individuals infected with an orthopoxvirus by aerosol route would benefit by a course of ribavirin therapy. Later, the fewer number of very sick individuals could be treated with intravenous cidofovir.

Recombinant green fluorescent protein-expressing human cytomegalovirus as a tool for screening antiviral agents

A recombinant human cytomegalovirus (AD169-GFP) expressing green fluorescent protein was generated by homologous recombination. Infection of human fibroblast cultures with AD169-GFP virus produced stable and readily detectable amounts of GFP signals which were quantitated by automated fluorometry. Hereby, high levels of sensitivity and reproducibility could be achieved, compared to those with the conventional plaque reduction assay. Antiviral activities were determined for four reference compounds as well as a set of putative novel cytomegalovirus inhibitors. The results obtained were exactly in line with the known characteristics of reference compounds and furthermore revealed distinct antiviral activities of novel in vitro inhibitors. The fluorometric data could be confirmed by GFP-based flow cytometry and fluorescence microscopy. In addition, laboratory virus variants derived from the recombinant AD169-GFP virus provided further possibilities for study of the characteristics of drug resistance. The GFP-based antiviral assay appeared to be very reliable for measuring virus-inhibitory effects in concentration- and time-dependent fashions and might also be adaptable for high-throughput screenings of cytomegalovirus-specific antiviral agents.

Cidofovir: a review of its use in cytomegalovirus retinitis in patients with AIDS

Cidofovir is an antiviral nucleotide analogue with significant activity against cytomegalovirus (CMV) and other herpesviruses. The drug is indicated for the treatment of CMV retinitis, a sight-threatening condition, in patients with AIDS. Cidofovir has a long intracellular half-life which allows for a prolonged interval (2 weeks) between maintenance doses. In contrast, other intravenous treatment options for patients with CMV retinitis (i.e. ganciclovir and foscarnet) must be administered on a daily basis. The efficacy of intravenous cidofovir has been demonstrated in patients with AIDS and previously untreated CMV retinitis in multicentre randomised trials, and in a dose-finding study of cidofovir in patients with AIDS and previously treated relapsing CMV retinitis. Clinical trials have been relatively small (n < or = 100 patients) and no studies have been conducted directly comparing intravenous cidofovir with the more established intravenous agents, ganciclovir or foscarnet. Indirect comparisons of clinical trial data suggest that intravenous cidofovir may have similar efficacy to intravenous ganciclovir or foscarnet in delaying progression of CMV retinitis. However, such comparisons must be made with caution because of potential differences in patient populations, data analysis techniques and interobserver variability in the masked assessment of retinal photographs. Nevertheless, intravenous cidofovir offers a less intrusive administration regimen than intravenous ganciclovir or foscarnet because of its prolonged dosage interval. Since therapy is life-long, patients receiving daily intravenous ganciclovir or foscarnet (but not cidofovir) usually require an indwelling central venous catheter and are therefore at increased risk of serious infection. The relatively long dosage interval for cidofovir may also have favourable implications in terms of overall treatment costs and patient quality of life, although specific data are very limited. Potentially irreversible nephrotoxicity is the major treatment-limiting adverse event associated with intravenous cidofovir in patients with AIDS-related CMV retinitis. Anterior uveitis/iritis has been reported frequently with intravenous cidofovir in postmarketing reports and a small number of patients have developed hypotony. Other treatment options for CMV retinitis are also associated with serious adverse events, and selection of pharmacotherapy will depend on a number of factors including retinitis lesion characteristics, patient quality-of-life issues and efficacy and tolerability profiles of available therapies.

CONCLUSION

Although the extent of its use may be limited by its adverse event profile, cidofovir offers a useful addition to the limited number of drugs available for the treatment of CMV retinitis in patients with AIDS.

Antiviral drug susceptibility assays: going with the flow

This review describes the procedures for the use of fluorochrome labeled monoclonal antibodies and flow cytometry for the detection and quantification of virus infected cells. The application of this technology for (1) identifying virus infected cells in clinical specimens obtained from human cytomegalovirus (HCMV) and human immunodeficiency virus (HIV) infected individuals; (2) screening antiviral compounds active against HCMV, HDSV and HIV; and (3) performing drug susceptibility testing for HCMV, HSV and HIV clinical isolates are reviewed. The flow cytometry drug susceptibility assay is rapid, quantitative, and easily performed. It should be considered by anyone interested in performing drug susceptibility testing for any virus for which there are reliable monoclonal antibodies.

Indolocarbazoles: potent, selective inhibitors of human cytomegalovirus replication

In our search for new, safer anti-HCMV agents, we discovered that the natural product Arcyriaflavin A (la) was a potent inhibitor of HCMV replication in cell culture. A series of analogues (symmetrical indolocarbazoles) was synthesised to investigate structure activity relationships in this series against a range of herpes viruses (HCMV, VZV, HSV1, and 2). This identified a number of novel, selective and potent inhibitors of HCMV, 12,13-dihydro-2,10-difluoro-5H-indolo[2,3-a]pyrrolo[3,4-c]carbazol e-5,7-(6H)-dione (1d) being the best example (IC50=40 nM, therapeutic index > 1450). Compounds described in this series were generally poor inhibitors of protein kinase C betaII, and no correlation was found between the ability to inhibit HCMV and the enzyme PKC.