Targeting noncoding RNAs in disease

Many RNA species have been identified as important players in the development of chronic diseases, including cancer. Over the past decade, numerous studies have highlighted how regulatory RNAs such as microRNAs (miRNAs) and long noncoding RNAs (lncRNAs) play crucial roles in the development of a disease state. It is clear that the aberrant expression of miRNAs promotes tumor initiation and progression, is linked with cardiac dysfunction, allows for the improper physiological response in maintaining glucose and insulin levels, and can prevent the appropriate integration of neuronal networks, resulting in neurodegenerative disorders. Because of this, there has been a major effort to therapeutically target these noncoding RNAs. In just the past 5 years, over 100 antisense oligonucleotide-based therapies have been tested in phase I clinical trials, a quarter of which have reached phase II/III. Most notable are fomivirsen and mipomersen, which have received FDA approval to treat cytomegalovirus retinitis and high blood cholesterol, respectively. The continued improvement of innovative RNA modifications and delivery entities, such as nanoparticles, will aid in the development of future RNA-based therapeutics for a broader range of chronic diseases. Here we summarize the latest promises and challenges of targeting noncoding RNAs in disease.

Cytomegalovirus retinitis associated with acquired immunodeficiency syndrome

BACKGROUND

Cytomegalovirus (CMV) retinitis is the most severe intraocular complication that results in total retinal destruction and loss of visual acuity in patients with acquired immunodeficiency syndrome (AIDS). This study aimed to investigate the fundus characteristics, systemic manifestations and therapeutic outcomes of CMV retinitis associated with AIDS.

METHODS

It was a retrospective case series. CMV retinitis was present in 39 eyes (25 patients). Best corrected visual acuities, anterior segment, fundus features, fundus fluorescence angiography (FFA) and CD4(+) T-lymphocyte counts of the patients with CMV retinitis associated with AIDS were analyzed. Intravitreal injections of ganciclovir (400 µg) were performed in 4 eyes (2 patients).

RESULTS

Retinal vasculitis, dense, full-thickness, yellow-white lesions along vascular distribution with irregular granules at the border, and hemorrhage on the retinal surface were present in 28 eyes. The vitreous was clear or mildly opaque. Late stage of the retinopathy was demonstrated in 8 eyes characterized as atrophic retina, sclerotic and attenuated vessels, retinal pigment epithelium (RPE) atrophy, and optic nerve atrophy. Retinal detachment was found in 3 eyes. The average CD4(+) T-lymphocyte count in peripheral blood of the patients with CMV retinitis was (30.6 ± 25.3) × 10(6)/L (range, (0 - 85) × 10(6)/L). After intravitreal injections of ganciclovir, visual acuity was improved and fundus lesions regressed.

CONCLUSIONS

CMV retinitis is the most severe and the most common intraocular complication in patients with AIDS. For the patients with yellow-white retinal lesions, hemorrhage and retinal vasculitis without clear cause, human immunodeficiency virus (HIV) serology should be performed. Routine eye examination is also indicated in HIV positive patients.

The immediate early 2 protein of human cytomegalovirus (HCMV) mediates the apoptotic control in HCMV retinitis through up-regulation of the cellular FLICE-inhibitory protein expression

Human CMV (HCMV) is a widespread human pathogen that causes blindness by inducing retinitis in AIDS patients. Previously, we showed that viral immediate early 2 (IE2) protein may allow HCMV to evade the immune control by killing the Fas receptor-positive T lymphocytes attracted to the infected retina with increased secretion of Fas ligand (FasL). In this study, we further demonstrate that the secreted FasL also kills uninfected Fas-rich bystander retinal cells and that IE2 simultaneously protects the infected cells from undergoing apoptotic death, in part, by activating the expression of cellular FLIP (c-FLIP), an antiapoptotic molecule that blocks the direct downstream executer caspase 8 of the FasL/Fas pathway. c-FLIP induction requires the N-terminal 98 residues of IE2 and the c-FLIP promoter region spanning nucleotides -978 to -696. In vivo association of IE2 to this region, IE2-specific c-FLIP activation, and decrease of FasL-up-regulated activities of caspases 8 and 3 were all demonstrated in HCMV-infected human retinal cells. Moreover, c-FLIP up-regulation by IE2 appeared to involve PI3K and might also render cells resistant to TRAIL-mediated death. Finally, enhanced c-FLIP signals were immunohistochemically detected in IE-positive cells in the HCMV-infected lesions of the human retina. Taken together, these data demonstrate specific activation of c-FLIP by HCMV IE2 and indicate a novel role for c-FLIP in the pathogenesis of HCMV retinitis.

Human cytomegalovirus retinitis: pathogenicity, immune evasion and persistence

Human cytomegalovirus (HCMV) retinitis frequently occurs in severely naturally and iatrogenically immunocompromised patients. It has been shown that the immune-privileged retinal pigment epithelium (RPE) is a major site of persistent HCMV. Recently, evidence has accumulated to show that HCMV immediate early (IE) gene expression in RPE cells deviates ocular antiviral inflammation via FasL. Moreover, unlike in other cell types, the HCMV major IE1/2 enhancer promoter (MIEP) resists activation by proinflammatory stimuli mediated by the transcription factor NF-kappaB. However, tumor necrosis factor-alpha (TNF-alpha) and interferon-gamma (IFN-gamma) found at elevated levels in transplant recipients and AIDS patients with retinitis sensitize RPE cells and other retinal cells to FasL-mediated apoptosis, thus contributing to retina destruction and necrosis rather than inflammation. These specific features of RPE cells in conjunction with deregulated immune responses of immunocompromised patients seem to contribute to virus persistence and pathogenesis within the immune-privileged ocular retina.

Murine cytomegalovirus retinitis during MAIDS: Susceptibility correlates with elevated intraocular levels of interleukin-4 mRNA

PURPOSE

To determine if murine cytomegalovirus (MCMV)-infected eyes of mice with murine acquired immunodeficiency syndrome (MAIDS) that are destined to develop MCMV retinitis display elevated intraocular levels of interleukin-4 (IL-4) mRNA when compared with uninfected eyes of mice with MAIDS and unmanipulated, uninfected, eyes of normal healthy mice.

METHODS

Groups of C57BL/6 mice with MAIDS and normal C57BL/6 mice were infected uniocularly with MCMV by subretinal MCMV injection. IL-4 levels in individual spleens collected five days later from groups of MAIDS mice and normal mice were assessed by quantitative ELISA. MCMV-infected eyes and uninfected contralateral eyes from another group of mice with MAIDS were also collected at five days postinfection and individually subjected to competitive RT-PCR assay and real-time RT-PCR assay for detection and quantification of IL-4 mRNA. Unmanipulated eyes from normal C57BL/6 mice served as controls.

RESULTS

IL-4 mRNA was detected at a level of 9.7 +/- 3.4 pg mRNA per 1000 ng total RNA in 100% of MCMV-infected eyes of mice with MAIDS by competitive RT-PCR assay, but could not be detected in any of the uninfected eyes of MAIDS mice. In comparison, the more sensitive technique of real-time RT-PCR assay detected copies of IL-4 cDNA in both MCMV-infected eyes and uninfected eyes of MAIDS mice. MCMV-infected eyes showed a 16-fold increase in the number of IL-4 cDNA copies when compared with uninfected eyes. Neither technique detected IL-4 mRNA in unmanipulated eyes of normal mice. As expected, spleen cells from mice with MAIDS expressed significantly greater levels of IL-4 when compared with spleen cells from normal mice.

CONCLUSIONS

MCMV-infected mice with MAIDS exhibited an expected preferential activation of Th2 cells as determined by increased levels of IL-4 in spleen cells when compared with spleen cells of normal mice. MCMV-infected eyes destined to develop retinitis during MAIDS also showed increased levels of detectable IL-4 mRNA when compared with uninfected eyes of mice with MAIDS. It is therefore possible that IL-4 synthesis by Th2 CD4+ T cells during retrovirus-induced immunosuppression serves to inhibit the perforin cytotoxic pathway that subsequently allows susceptibility to MCMV retinitis during MAIDS.

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.

Fomivirsen: clinical pharmacology and potential drug interactions

Fomivirsen sodium is a 21-base phosphorothioate oligodeoxynucleotide complementary to the messenger RNA of the major immediate-early region proteins of human cytomegalovirus, and is a potent and selective antiviral agent for cytomegalovirus retinitis. Following intravitreal administration, fomivirsen is slowly cleared from vitreous with a half-life of approximately 55 hours in humans. Preclinical studies show that fomivirsen distributes to retina and is slowly metabolised by exonuclease digestion. Clearance from retina was shown to be similarly slow following loading from the vitreous. The estimated half-life for clearance of fomivirsen from retina was 78 hours in monkeys following a 115-microg dose. Because of the low doses coupled with slow disposition from the eye, measurable concentrations of drug are not detected in the systemic circulation following intravitreal administration. Systemically administered phosphorothioate oligodeoxynucleotides are highly bound to albumin and alpha2-macroglobulin in blood plasma. Because fomivirsen does not compete for oxidative metabolic processes involved in clearance of many xenobiotics, the most likely mechanism for drug interactions may be altered protein binding of a coadministered drug. The extremely low systemic exposure to this oligodeoxynucleotide following intravitreal administration largely negates its potential ability to interact with systemically administered drugs. Even if fomivirsen were able to access the blood, protein binding assays indicate that drugs that are site I and site II binders of albumin (warfarin, ibuprofen, salicylic acid) are not displaced in the presence of phosphorothioate oligodeoxynucleotides of various sequences at concentrations orders of magnitude higher than that seen for fomivirsen. Administration of fomivirsen with numerous systemically administered antiretrovirals (for example zidovudine and zalcitabine) as well as systemically administered anticytomegalovirus agents such as foscarnet and ganciclovir has been reported to be well tolerated. The only reported warning is a recommendation against administration within 2 to 4 weeks of cidofovir treatment due to an increased risk of ocular inflammation.

Apoptosis of human retina and retinal pigment cells induced by human cytomegalovirus infection

Human cytomegalovirus (HCMV) retinitis is the most common ocular opportunistic infection in immunocompromised patients and AIDS. It often leads to blindness if left untreated. The question as to how HCMV infection causes retinal pathogenesis and visual destruction in AIDS patients remains unresolved. To answer the question, by using terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end labeling assay, we detected the significant signals of apoptotic cells at the same sites in the HCMV-infected retina of AIDS patients as compared to AIDS patients without HCMV retinitis. In vitro study also revealed apoptosis induced by HCMV infection in human retinal pigment epithelium cells, mediated by activation of caspase 3 and poly(ADP-ribose) polymerase pathway. These results strongly suggest the fundamental role of HCMV-induced apoptosis in mediating cell death in infected human retina and retinal pigment epithelium cells to make severe visual impairment.

High dose oral ganciclovir treatment for cytomegalovirus retinitis

BACKGROUND

The oral formulation of ganciclovir is approved at a dose of 3.0 g/day for maintenance treatment of cytomegalovirus (CMV) retinitis following an initial induction course of intravenous (IV) anti-CMV therapy. Median time to progression of CMV retinitis is 12-20 days shorter with oral compared to IV ganciclovir maintenance, likely due to the limited oral bioavailability of ganciclovir.

OBJECTIVES

We hypothesized that higher systemic drug exposures associated with increased doses of oral ganciclovir would be associated with increased efficacy.

STUDY DESIGN

Maintenance treatment of CMV retinitis with higher than standard doses of oral ganciclovir (>3.0 g/day) was studied in 281 AIDS patients with previously treated, stable retinitis randomized to 3.0, 4.5 or 6.0 g/day oral, or 5 m/kg/day IV ganciclovir. Graders unaware of treatment assignments determined retinitis progression using fundus photographs. Vision, other ophthalmic measures and safety were assessed open-label.

RESULTS

Median days to photographic progression were 41, 50, 57 and 70, respectively (P=0.052; 3.0 g vs. IV). Hazard ratios for progression relative to IV were 1.66, 1.28 and 1.19 (P=0.016 for 3.0 g). NONMEM-modeled estimates of average serum ganciclovir concentration area under the curve (AUC(0-24)) correlated best with time to progression (P=0.0019). Six grams per day oral ganciclovir was most similar in efficacy to IV, although broad confidence intervals prevented a conclusive comparison. Patients receiving oral ganciclovir had a lower frequency of sepsis and IV catheter events.

CONCLUSIONS

This study suggests that the efficacy of ganciclovir for the maintenance treatment of CMV retinitis improves with increasing total drug exposure (measured as average serum concentration AUC(0-24)). All four regimens of ganciclovir were reasonably well tolerated, with safety profiles similar to what has been reported in prior work.

Up-regulation of Fas ligand expression by human cytomegalovirus immediate-early gene product 2: a novel mechanism in cytomegalovirus-induced apoptosis in human retina

Human CMV (HCMV) is an important pathogen that causes widespread diseases in immunocompromised individuals. Among the opportunistic HCMV infections, HCMV retinitis is most common in transplant recipients and AIDS patients. It often leads to blindness if left untreated. The question as to how HCMV infection causes retinal pathogenesis remains unresolved. Here, we report that viral immediate-early gene product 2 (IE2), but not IE1, up-regulates the Fas ligand (FasL) expression in HCMV-infected human retinal pigment epithelium cells. Increased secretion of FasL from virally infected cells into cultured medium was observed upon HCMV infection. The capability of such cell-free medium to induce apoptosis of Fas (CD95)-expressing Jurkat cells further implies that Fas-FasL interaction might mediate cell death in the lesion of HCMV retinitis. To support this idea, we observed augmented soluble FasL levels in vitreous from AIDS patients with HCMV retinitis as compared with that from AIDS patients without HCMV infection. In addition, by in situ hybridization and immunohistochemistry, we detected enhanced signals of FasL, the existence of viral IE Ags and apoptotic cells at the same sites in the lesion of HCMV-infected retina. These results strongly suggest that IE2 induction of FasL expression in human retina might be an important event that takes place in the early stage of infection and finally leads to visual loss in individuals affiliated with HCMV retinitis.

[Anterior uveitis and cidofovir]

PURPOSE

This retrospective study was designed to determine the different parameters involved in the occurrence of uveitis during treatment with codofovir.

PATIENTS AND METHODS

This study included 10 patients out of 13 treated with cidofovir for cytomegalovirus (CMV) disease. Ocular examination, CD4+ lymphocyte count, and creatinine clearance were performed for each case of uveitis.

RESULTS

During the 17-month study, 20 uveitis cases were analyzed. The first attack occurred after a median interval of 7.6 doses. At the time of ocular inflammation, 65% of the cases had a CD4+ lymphocyte count >=100x10(6)/L, the patients thus had an improved immune function. Half of the patients had a normal creatinine clearance. The patients with a CD4+ lymphocyte count<100x10(6)/L who presented one or more incidents of uveitis had an abnormal clearance, thus probably inducing intraocular storage of the drug.

CONCLUSION

The occurrence of anterior uveitis during treatment with cidofovir is induced by the association of several parameters: a previous history of CMV retinitis, improvement of the immune function state, and intraocular storage of the drug.

Cytomegalovirus infection decreases expression of thrombospondin-1 and -2 in cultured human retinal glial cells: effects of antiviral agents

In fibroblasts, infection with human cytomegalovirus (HCMV) inhibits expression of the extracellular matrix proteins thrombospondin-1 and -2 (TSP-1 and TSP-2). These effects may depend on expression of HCMV immediate-early (IE) genes, which are activated by cellular transcription factor NF-kappaB. The influence of HCMV infection on TSP-1 and TSP-2 expression and the ability of different antiviral drugs to prevent these cellular changes in permissive cultures of human retinal glial cells were observed. Ganciclovir inhibited only HCMV late antigen (LA) expression, whereas antisense oligonucleotide ISIS 2922 and peptide SN50, inhibitors of HCMV IE expression and NF-kappaB activity, respectively, inhibited both IE and LA expression. ISIS 2922 and SN50, but not ganciclovir, prevented down-modulation of TSP-1 and TSP-2. The results showed that HCMV-induced down-modulation of TSP-1 and TSP-2 in retinal glial cells is prevented by inhibition of HCMV IE expression. These findings may be relevant to pathogenesis and treatment of HCMV retinitis.

Ganciclovir delivery through an intravitreal microdialysis probe in rabbit

The treatment of cytomegalovirus retinitis has during the last years been done mainly with sustained release ganciclovir devices implanted in the vitreous. In the present study it is shown that ganciclovir can be administered into the rabbit vitreous by microdialysis. A concentration of about 10(-6) M, which is considered within the therapeutic range, is achieved in the vitreous after a microdialysis perfusion. The method offers possibility of variation in the drug delivery that is not possible with the ganciclovir implants.

The pharmacokinetics and safety profile of oral ganciclovir combined with zalcitabine or stavudine in asymptomatic HIV- and CMV-seropositive patients

Two open-label, randomized, multiple-dose, three-way crossover studies were performed to assess the pharmacokinetics and safety of oral ganciclovir 1000 mg q8h in asymptomatic patients seropositive for human immunodeficiency virus and cytomegalovirus. Ganciclovir was administered alone and in combination with zalcitabine 0.75 mg q8h (study 1) or stavudine 40 mg q12h (study 2). In the presence of zalcitabine, the only statistically significant change in the pharmacokinetic parameters of ganciclovir was a 22.2% mean increase in AUC0-8. However, there was no significant change in the renal clearance of ganciclovir when coadministered with zalcitabine, suggesting that the increase in serum ganciclovir concentration cannot be attributed to competition for active renal tubular secretion. No change in zalcitabine pharmacokinetics was observed in combination with ganciclovir. There were no significant changes in the pharmacokinetics of ganciclovir or stavudine when coadministered. Ganciclovir was well tolerated when given alone and in combination with either zalcitabine or stavudine.

Fluorophotometry in patients with human immunodeficiency virus with and without cytomegalovirus retinitis

OBJECTIVE

To study the aqueous humor dynamics in subjects with human immunodeficiency virus (HIV) with and without cytomegalovirus (CMV) retinitis.

DESIGN

Prospective cross-sectional study.

PARTICIPANTS

Fourteen HIV-positive subjects (27 eyes, 19 with CMV retinitis and 8 without CMV retinitis), and a control group of 9 HIV-negative subjects (17 eyes).

TESTING

Fluorophotometry.

MAIN OUTCOME MEASURES

Aqueous flow rates as measured by fluorophotometry and intraocular pressure (IOP).

RESULTS

Analysis of variance of the mean corrected aqueous flow rate revealed that both HIV-positive groups had significantly lower aqueous flow rates than did the control group (P < 0.03). No difference in mean aqueous flow rates was found between the HIV-positive eyes with or without CMV retinitis. Comparison of mean IOP revealed that HIV-positive eyes with CMV retinitis had significantly lower IOP than did the HIV-positive eyes without CMV retinitis (P = 0.03) and HIV-negative subjects (P = 0.002). There was no correlation between aqueous flow rate and IOP in HIV-positive subjects (P > 0.5).

CONCLUSION

The lack of correlation between the aqueous flow rate and IOP suggests that there may be some disassociation between these parameters in HIV-positive patients. Further studies are needed to better understand the mechanism of aqueous formation and in the management of disorders affecting IOP in this population.

Fomivirsen

Fomivirsen (ISIS 2922) is an antisense oligonucleotide which specifically inhibits replication of human cytomegalovirus. It achieves this by binding to complementary sequences on messenger RNA transcribed from the major immediate-early transcriptional unit of the virus. It is being developed for the treatment of cytomegalovirus retinitis. Mean maximum retinal concentrations of fomivirsen occurred approximately 2 days after a single intravitreal injection in monkeys. The elimination half-life of fomivirsen (after a single 115 microg dose) in monkey retina was 78 hours. Fomivirsen, administered as an intravitreal injection, significantly delayed progression of cytomegalovirus retinitis in patients with AIDS in preliminary clinical trials. In 18 patients with newly diagnosed, unilateral, peripheral cytomegalovirus retinitis treated with fomivirsen 165 microg once weekly for 3 weeks, then 165 microg every second week, the median time to disease progression was significantly longer than in 10 patients in whom fomivirsen treatment was deferred until early disease progression (71 vs 14 days). In patients with advanced, refractory, sight-threatening disease, treatment with fomivirsen 330 microg once weekly for 3 weeks and then 330 microg every 2 weeks (n = 34) or 330 microg on days 1 and 15 and then monthly (n = 20) significantly delayed disease progression. The interpolated median time to disease progression was 90 days in both treatment groups. The most common adverse events reported in clinical trials of fomivirsen were increased intraocular pressure and mild to moderate intraocular inflammation. These events were generally transient or reversible with topical steroid treatment.

Triple viral retinitis diagnosed by polymerase chain reaction of the vitreous biopsy in a patient with Richter syndrome

PURPOSE

To report the evaluation and identification of herpes viruses associated with retinitis in a patient with Richter syndrome.

METHODS

Diagnostic vitrectomy was performed on a patient with systemic leukemia and retinitis. The vitreous sample was evaluated by cytology, analysis of cytokines by ELISA, and detection of virus by polymerase chain reaction.

RESULTS

The vitreous biopsy specimen showed no malignant cells but predominant CD8+ lymphocyte infiltration with elevated interferon gamma and interleukin-6. DNA amplification and Southern blot analysis demonstrated DNA of herpes simplex, varicella-zoster, and cytomegalovirus.

CONCLUSION

Retinitis associated with multiple viruses in the vitreous biopsy may mimic leukemic infiltration in the eye.

Immunohistochemical localization of ganciclovir in the human retina

PURPOSE

To localize ganciclovir in the retina of human eyes treated with intravenous or intravitreal ganciclovir for cytomegalovirus (CMV) retinitis.

METHODS

Paraffin-embedded five-micron sections of autopsy eyes were obtained from seven patients as follows: two patients with CMV retinitis treated with intravenous ganciclovir; two patients with CMV retinitis treated with an intravitreal sustained-release ganciclovir device; one patient with CMV retinitis treated with intravenous foscarnet; and two patients with AIDS without CMV retinitis who did not receive any anti-CMV therapy. The paraffin was removed from the sections, and indirect immunofluorescent staining was performed, using an antiserum to ganciclovir.

RESULTS

Bright fluorescent staining was noted in the retinal pigment epithelium (RPE) and photoreceptor outer segments of eyes treated with intravenous or intravitreal ganciclovir, but not in eyes treated with foscarnet or without CMV retinitis. In addition, patches of bright fluorescent staining of the internal limiting membrane was noted in eyes treated with intravitreal ganciclovir.

CONCLUSIONS

Ganciclovir is detected in the outer retina of patients with CMV retinitis treated with intravenous or intravitreal therapy. The drug is detected also in the internal limiting membrane in eyes treated with the intravitreal sustained-release ganciclovir device.

An immunohistochemical study of TNF-alpha in optic nerves from AIDS patients

PURPOSE

Both in vitro and in vivo studies have implicated a role for tumor necrosis factor (TNF-alpha) in the pathology of demyelinating diseases. The purpose of this study was to address the hypothesis that TNF-alpha is a mediator of AIDS-related optic nerve injury and to determine the cell types involved in the proliferation of TNF-alpha in the AIDS optic nerve.

METHODS

Ten optic nerves from seven patients with AIDS, and three from persons who were HIV negative were stained, using the indirect immunoperoxidase method. Six of the ten AIDS optic nerves were positive for cytomegalovirus (CMV), but the remainder did not have abnormal fundus findings.

RESULTS

In all the optic nerves from AIDS patients with or without CMV retinitis, the vast majority of astrocytes stained strongly for TNF-alpha. Microglial cells (MPS-derived macrophages) varied from not staining to staining strongly positive for TNF-alpha. However, oligodendrocytes were not labeled positively for TNF-alpha. Some endothelial cells also stained for TNF-alpha. Examination of normal optic nerves and controls did not reveal any cell type that stained positively for TNF-alpha.

CONCLUSIONS

The present study supports the contention that TNF-alpha is a major mediator of AIDS-associated optic neuropathy. HIV infection induces the production of TNF-alpha in macrophages and astrocytes, which probably causes demyelination and other neuronal damage.

Comparison of pharmacokinetics and dynamics of two dosage regimens of foscarnet in AIDS patients with Cytomegalovirus retinitis

OBJECTIVE

To compare the pharmacokinetics of foscarnet administered as an infusion twice daily (BID) or thrice daily (TID), and to compare the effects on the electrolyte balance, cardiac and renal functions over a 3-week induction treatment of Cytomegalovirus (CMV) retinitis.

METHODS

Pharmacokinetics/dynamics of foscarnet were investigated on treatment days 1, 14 and 21. Twelve AIDS patients with CMV retinitis completed the investigation period. Concentrations of foscarnet and electrolytes were assayed by high-performance liquid chromatography (HPLC) and by an ion-selective analyser, respectively.

RESULTS

The pharmacokinetics of the two regimens were essentially similar. Foscarnet plasma and creatinine clearances were 2.0 and 1.6 ml.min-1.kg-1, respectively, in the BID group at steady state (day 21). In the TID group the corresponding values were 1.8 and 1.7 ml.min-1.kg-1, respectively. In both regimens the elimination half-life of foscarnet was 2-3 h. Ionized calcium concentrations were transiently decreased and strongly inversely correlated to foscarnet plasma concentrations in both regimens with no significant differences between groups. A trend towards prolongation of the QTc interval was seen when data from both treatments were analysed together.

CONCLUSION

Our data suggest comparable pharmacokinetics of foscarnet after intermittent administration BID or TID during a 3-week induction period.

Nonparametric expectation maximization population modeling of ganciclovir

The use of the nonparametric expectation maximization (NPEM2) program to estimate pharmacokinetic parameters of ganciclovir in a group of patients with human immunodeficiency virus (HIV) and cytomegalovirus (CMV) infection was evaluated. A 10-point data set per patient obtained over 8 hours was analyzed. Mean pharmacokinetic parameters obtained included rate constant from the central to the peripheral compartment (KCP,3.1 hr-1), rate constant from the peripheral to the central compartment (KPC, 0.824 hr-1), slope of the volume of distribution to body weight (VS, 0.246 L/kg), and slope of clearance to creatinine clearance (Cl(cr)) and body weight (CLS,0.222L/hr/kg/100 mL/ min Cl(cr). Use of NPEM2 led to identification of a subset of patients with CMV retinitis who had a more rapid clearance of ganciclovir of 0.51 to 0.54 L/hr/kg/100 mL/min Cl(cr). Use of smaller, optimally timed samples of five, four, and three data points per patient produced mean pharmacokinetic parameter results consistent with the full ten-point data set. When Bayesian-derived parameter estimates using a five-point data set were compared with a traditional, nonlinear, least-square analysis of the entire ten-point data set, estimates of clearance were determined to be relatively unbiased and precise. The ability of NPEM2 to estimate pharmacokinetic parameters and to determine the population distribution of the parameters was demonstrated. By using points in the analysis chosen by D-optimal design theory, NPEM2 was able to give consistent parameter estimates with as few as three data points. Determination of the distribution appeared to have been dependent on the time points used, however. The approach of MAP-Bayesian analysis to derive patient-specific estimates using optimal samples and prior estimates from a previous population pharmacokinetic analysis for inclusion in subsequent pharmacodynamic analyses of drug exposure (area under the concentration-time curve) may enable development of exposure-response and exposure-toxicity relationships.

High dose intravitreal ganciclovir injection provides a prolonged therapeutic intraocular concentration

BACKGROUND

Although intravitreal high dose ganciclovir has previously been found to provide excellent control of cytomegalovirus (CMV) retinitis, little was known about the vitreous concentrations of ganciclovir after a 2 mg intravitreal injection.

METHODS

Eleven vitreous samples were taken from seven patients with CMV retinitis at 24 and 72 hours after a 2 mg intravitreal injection of ganciclovir and the concentration of ganciclovir was measured by high performance liquid chromatography.

RESULTS

The mean concentration of ganciclovir at 24 hours was 143.8 mg/l (95% confidence interval 97.8-190) and at 72 hours was 23.4 mg/l (95% CI 0-49.7). The half life ranged from 11.9 to 26.3 (mean 18.8) hours in the four patients who had two samples taken. The mean half life calculated from the mean concentrations at 24 and 72 hours was 18.3 hours, so the calculated mean concentration at 7 days was 0.6 mg/l.

CONCLUSIONS

This suggests that it takes about 7 days to eliminate the intravitreal ganciclovir, and that it is not likely to accumulate with weekly injections. The intravitreal concentrations achieved with high dose therapy remained above the ID50 for CMV (0.25-1.22 mg/l) for up to 7 days.

Effect of foscarnet induction treatment on quantitation of human cytomegalovirus (HCMV) DNA in peripheral blood polymorphonuclear leukocytes and aqueous humor of AIDS patients with HCMV retinitis. The Italian Foscarnet Study Group

The aim of this study was to investigate peripheral blood polymorphonuclear leukocytes and, whenever possible, aqueous humor from 65 AIDS patients with ophthalmoscopically diagnosed human cytomegalovirus (HCMV) retinitis to determine (i) whether patients consistently carry viral DNA and (ii) to what extent foscarnet induction treatment decreases viral DNA levels. HCMV DNA was quantified by PCR using densitometric analysis of hybridization products obtained from external standards and a standard curve from which the number of genome equivalents of test samples, normalized by using an internal amplification control, was interpolated. Results showed that 56 of 65 patients (86.1%) were positive for HCMV DNA prior to induction treatment. Of 41 of the 56 patients (73.2%) whose blood had become DNA negative after induction, only 5 had a high viral load (> 5,000 genome equivalents per 2 x 10(5) polymorphonuclear leukocytes) prior to induction, whereas as many as 13 of the 15 (26.8%) patients remaining DNA positive after induction had a high viral load prior to induction. Finally, of the nine patients (13.8%) with DNA-negative blood prior to induction treatment, three were shifted to foscarnet from ganciclovir, while six were erroneously enrolled in the study. Pre- and postinduction aqueous humor samples were obtained from 12 patients; all of these were DNA positive prior to induction, whereas after induction, 4 became negative, 6 showed a marked decrease in viral DNA, and 2 had nearly stable low DNA levels. In conclusion, PCR is a valuable tool for etiologic diagnosis and monitoring of HCMV retinitis treatment in AIDS patients. HCMV DNA is consistently present in the blood and aqueous humor of all patients with HCMV retinitis. Foscarnet induction treatment is highly effective in suppressing or reducing DNA levels in both blood leukocytes and aqueous humor.