Fomivirsen - a phosphorothioate oligonucleotide for the treatment of CMV retinitis.

Fomivirsen is a 21-nucleotide phosphorothioate oligonucleotide which, when injected into a human eye, is capable of inhibiting CMV retinitis. Its mode of action is consistent with an antisense mechanism. Prior to human trials, fomivirsen was tested in a number of in vitro cell lines and was found to inhibit CMV replication in a dose-dependent manner with a mean 50% inhibitory concentration between 0.03 and 0.2 microM. Intravitreal drug clearance studies have revealed first-order kinetics with a half-life in the rabbit of 62 hours. In a clinical trial of patients with newly diagnosed CMV retinitis receiving 165 mg per injection, time to progression was interpolated to 71 days with 44% of the patients remaining on treatment for over one year. In patients who failed other anti-CMV treatments, the interpolated time to progression was 91 days when receiving 330 mg per injection. No systemic absorption of the drug could be detected. Reported adverse events have been for the most part mild to moderate in intensity and either resolved spontaneously or were treatable with topical medications. Locally administered fomivirsen effectively inhibits CMV retinitis using a mode of action which is complementary to existing DNA polymerase inhibitors.

Influence of highly active antiretroviral therapy on the development of CMV disease in HIV positive patients at high risk for CMV disease.

BACKGROUND/AIMS: In the pre-HAART era, HIV positive patients with CD4+ cell counts below 50 cells x10(6)/l, and those with detectable cytomegalovirus (CMV) DNA in their peripheral blood, were considered to be at high risk for the development of CMV disease. With the start of highly active antiretroviral therapy (HAART), a restoration of immune function occurred in these patients, and as a consequence patients became less vulnerable to CMV disease. Since it is not exactly known how HAART influences CMV viral load in peripheral blood and the incidence of CMV disease in high risk HIV positive patients a group of patients was followed before and after initiation of HAART. METHODS: 29 HIV positive patients, seen in the first 3 months of 1996 at the AIDS clinic of the Academic Medical Centre, at high risk for development of CMV disease (positive CMV DNA assay in blood and/or CD4+ cell count below 50 cells x10(6)/l), not receiving anti-CMV maintenance therapy, were included in a prospective cohort study. HAART was started in the second trimester of 1996. Patients were evaluated for the occurrence of CMV retinitis, or CMV disease elsewhere, comparing the incidence of CMV events before and after the start of HAART. Following the introduction of HAART, CD4+ cell counts and quantitative polymerase chain reaction (PCR) for CMV DNA in blood were monitored in all patients who remained alive and were not receiving anti-CMV maintenance therapy (n=22). Follow up was performed until August 1998; the mean follow up after the start of HAART was 14.9 months (range 8-22 months). RESULTS: In the pre-HAART period four patients developed CMV disease, and four died (without clinically manifest CMV disease). After the start of HAART no patient developed CMV disease or died. With HAART, the mean CD4+ cell counts increased from 34 cells x10(6)/l to 194 cells x10(6)/l at the end of follow up. CMV DNA could be detected in the blood of 11 patients. Quantification showed a decline in the amount of detectable DNA during follow up. At the last examination only one patient showed a positive PCR assay. This was the only patient with a CD4+ cell count remaining below 100 cells x10(6)/l. CONCLUSION: In HIV positive patients at high risk of CMV retinitis, either with a positive CMV PCR assay in blood and/or with CD4+ cell counts below 50 cell x10(6)/l, HAART causes a dramatic decrease in the occurrence of CMV disease. This decrease is paralleled by an increase in CD4+ cell count, and a decrease in the amount of CMV DNA in the blood, which was below detection levels in all patients with CD4+ cell counts above 100 cells x10(6)/l.

Cytomegalovirus (CMV) strain differences between the eye and blood in AIDS patients with CMV retinitis.

OBJECTIVE: To investigate possible differences in cytomegalovirus (CMV) strain distribution between the eye and blood in AIDS patients with CMV retinitis. METHODS: CMV DNA sequences from aqueous humour and peripheral blood leukocytes (PBL), obtained from 13 AIDS patients with CMV retinitis, were compared. DNA was isolated and the CMV IE-1 sequence (part of the immediate early-1 gene) and the a-sequence (located in the a-region) were amplified by polymerase chain reaction (PCR). The PCR products of the a-sequence were analysed by Southern blotting for amplified fragment-length polymorphisms. The level of divergence between the a-sequences of aqueous humour- and PBL-derived CMV was studied in two patients by cloning these sequences followed by sequence analysis. RESULTS: CMV DNA could be detected in all aqueous humour samples and in 10 out of 13 paired blood samples. In the 10 patients, with CMV DNA detectable in both aqueous humour and PBL, seven cases showed differences between the amplified products of both compartments. Sequence analysis in two patients revealed that the aqueous humour and PBL of the same patient can harbour both identical, similar and highly divergent CMV a-sequences. CONCLUSION: These results indicate that despite the haematogenous spread of CMV, the eye, being a relatively shielded organ, may contain CMV strains different from those found in the blood.

Optic neuritis heralding varicella zoster virus retinitis in a patient with acquired immunodeficiency syndrome.

We report on a 29-year-old severely compromised acquired immunodeficiency syndrome patient who developed retrobulbar optic neuritis 5 weeks after an episode of cutaneous herpes zoster infection. During the optic neuritis, varicella zoster virus could be demonstrated in the cerebrospinal fluid. The neuritis responded well to treatment with foscarnet, but, 3 weeks into therapy, varicella zoster retinitis developed. Additional treatment with intravenous acyclovir stopped progression of the retinitis and resulted in healing of the retinal lesions. This case suggests that retrobulbar optic neuritis can be regarded as a prodrome of imminent acute retinal necrosis. Early recognition and prompt therapy with combined antivirals may prevent the development of this devastating ocular complication of varicella zoster infection.

Effects of protease inhibitors on the course of CMV retinitis in relation to CD4+ lymphocyte responses in HIV+ patients.

AIM: To gain insight into the course of CMV retinitis (CMVR) in AIDS patients receiving protease inhibitors (PI), and to evaluate whether certain patterns of CD4 response are indicative of the clinical outcome and the risk of recurrence. METHODS: 15 consecutive AIDS patients receiving maintenance therapy for CMVR were included in a prospective observational cohort study at the university hospital between July and October 1996. Patients were evaluated for signs of CMVR activity and intraocular inflammation. CMVR recurrence was defined as the primary clinical endpoint. Follow up was performed until July 1997. No patient was lost to follow up. Clinical outcome was related to CD4+ lymphocyte counts, which were monitored every 6 weeks. Highly active antiretroviral treatment regimen including PI was started at study entry. RESULTS: All recurrences (n = 7) were in patients who failed to have a sustained increase in CD4 counts, whereas CMVR remained inactive during a follow up of 42-52 weeks in those who were able permanently to restore their CD4 values to 100 x 10(6)/l or more (n = 5). The remaining three patients died after 12, 16, and 50 weeks, respectively, without recurrences. All relapses of CMVR were seen after 6-16 weeks, and at CD4 counts well below 100 x 10(6)/l. CONCLUSIONS: The beneficial effects of PI treatment correlate with the pattern of CD4 response. Sustained increases in CD4 counts achieved in the first 16 weeks of treatment are associated with a prolonged period of CMVR quiescence. Poor initial response is associated with a high risk of CMVR recurrence.

Risk of developing CMV retinitis following non-ocular CMV end organ disease in AIDS patients.

AIM: To describe the risk of developing cytomegalovirus (CMV) retinitis after a first episode of extraocular CMV disease in AIDS patients. METHODS: A review of the clinical records of 20 AIDS patients, without CMV retinitis, with histologically confirmed extraocular CMV disease, was performed. The main outcome measures were occurrence of CMV retinitis, time to development of CMV retinitis, relation to maintenance therapy, and survival. RESULTS: A CMV retinitis was diagnosed in 17 of 20 (85%) patients with an immunohistologically confirmed diagnosis of extraocular CMV disease after a mean follow up of 6.4 months. Four patients received maintenance therapy. Three of them developed retinitis after a mean of 9.6 months (range 2-16 months). Sixteen did not receive maintenance and retinitis was diagnosed in 14 of them after a mean of 5.7 months (range 2-11 months). Mean survival was 9.9 months after the diagnosis of extraocular disease, and 4.5 months after the diagnosis of retinitis. In the four patients receiving maintenance therapy, mean survival was 11.5 months, and in the 16 other patients mean survival was 9.5 months. Patients did not receive protease inhibitors. CONCLUSION: In the preprotease inhibitor era extraocular CMV disease strongly predisposes to the subsequent development of CMV retinitis. Although maintenance therapy did not prevent the occurrence of retinitis, the time period between both events seems to lengthen considerably. In patients receiving maintenance survival is also longer.

Association of progressive outer retinal necrosis and varicella zoster encephalitis in a patient with AIDS.

BACKGROUND: A patient with AIDS who developed the clinical picture of bilateral progressive outer retinal necrosis (PORN) in combination with varicella zoster encephalitis is described. The picture developed more than 2 years after an episode of ophthalmic zoster infection, and following intermittent exposure to oral acyclovir because of recurrent episodes of cutaneous herpes simplex infection. METHODS: Aqueous humour, obtained by paracentesis of the anterior chamber, was analysed using immunofluorescence and polymerase chain reaction (PCR). Postmortem analysis of eye and brain tissue was performed by using conventional techniques and in situ hybridisation. RESULTS: While conventional techniques all failed to detect a causative agent, analysis of the aqueous humour using PCR, and histological examination of necropsy specimens from eyes and brain using in situ hybridisation were conclusive for the diagnosis varicella zoster virus (VZV) infection. CONCLUSION: This case documents the presumed association of PORN and VZV encephalitis in a severely immunocompromised AIDS patient.

Laboratory tests in uveitis. New developments in the analysis of local antibody production.

Analysis of local intraocular antibody production is a valuable tool with which to confirm a suspected clinical diagnosis in uveitis. We have analysed paired serum and aqueous samples for the presence of specific antibodies against toxoplasma, cytomegalovirus, herpes simplex virus and varicella zoster virus. Of the patients retrospectively diagnosed as having toxoplasma chorioretinitis 75% had a positive antibody coefficient indicating specific antibody production in the eye. Local antibody production in the eye directed against CMV confirmed the suspected diagnosis of CMV retinitis in 50% of the AIDS patients investigated. So far we have not been able to demonstrate local antibody production against herpes simplex virus (26 samples tested). Two of three patients with acute retinal necrosis had a positive antibody coefficient against varicella zoster virus. Both of these patients had an even higher titer in the aqueous than in serum. Since the choice of therapy, in infectious uveitis, depends on the causative organisms, it is very important to confirm a suspected clinical diagnosis by means of aqueous humor analysis.

Matching between feline left ventricle and arterial load: optimal external power or efficiency.

We tested the hypothesis that the feline left ventricle normally works at optimal external power as opposed to optimal efficiency by (re)analyzing data from five isolated, blood-perfused cat hearts and 39 open-thorax cats. In the isolated hearts, we measured pump function, external steady power, myocardial oxygen consumption, and efficiency. Optimal external power and optimal efficiency were found at different left ventricular outputs (6.94 +/- 0.33 and 8.35 +/- 0.37 ml/s, respectively; P less than 0.001). In the in situ cat hearts the working point was found at an output of 4.72 +/- 0.32 ml/s, whereas optimal external power was found at 4.84 +/- 0.26 ml/s. These values were not significantly different. Assuming that the point of optimal efficiency was located at the same fraction of the maximal unloaded left ventricular output (Fmax) as in the isolated hearts, i.e., 0.7, we found the point of optimal efficiency for the in situ heart at a flow of 5.83 +/- 0.32 ml/s, which was significantly different (P less than 0.001) from the flow in the working point. Our data therefore indicate that the left ventricle in the open-thorax cat is matched to the arterial load such that its external power output rather than efficiency is optimized.

Feline left ventricle does not always operate at optimum power output.

In a previous study we showed that under a variety of conditions the feline left ventricle operates at optimum external power. This condition was defined as matching. In the present study matching of left ventricle and systemic arterial tree has been further investigated in the open-thorax cat during control, after volume loading (n = 8), and during norepinephrine infusion (n = 8). The pump-function graph relating mean left ventricular pressure and mean flow was fitted with a parabola characterized by two parameters, the pressure axis and the flow axis intercepts (Pmax and Fmax, respectively). After volume loading, as well as during norepinephrine infusion, the pump-function graph showed an outward shift plus a clockwise rotation. Pmax and Fmax increased 27 and 8% during volume loading and 37 and 8% during norepinephrine. In the steady states the mean flows at the working point and at the point of optimum external power were determined. During control and volume loading these flow values could not be shown to differ. However, during norepinephrine infusion, flow at the working point was found to be smaller than at optimal external power. This finding implies that during norepinephrine, the left heart does not operate at optimum external power; so a mismatch of heart and periphery is obtained.

Optimal power generation by the left ventricle. A study in the anesthetized open thorax cat.

We studied the interaction of the left ventricle and the systemic arterial bed in the open thorax cat. In the steady state, the ventricle can be characterized by the pump function graph (i.e., the relationship between mean left ventricular pressure and mean outflow). From this pump function graph, the apparent source resistance of the heart is found. Apparent source resistance is defined as the ratio of the difference between maximal and actual mean left ventricular pressure, and mean outflow. The arterial system can be characterized by the ratio of mean aortic pressure and mean flow (peripheral resistance). The pressure and flow at which the heart operates is defined as the working point. We have investigated whether the ventricle in the intact cat is working optimally, i.e., that it cannot increase work output further at the end-diastolic volume, contractile state, and prevailing heart rate. This condition is considered as "matching" of ventricle and load. It could be shown that optimal power is transferred when the ratio of peripheral and apparent source resistance equals twice the ratio of mean aortic and mean left ventricular pressure (the matching principle). In four cats, we observed that mean aortic and mean left ventricular pressures are proportionally related. Mean external power (the time integral of the product of pressure and flow divided by cycle length) and steady power (the product of mean pressure and mean flow) were found to be proportional as well. These proportionalities allow for the calculation of peripheral resistance and mean external power from the pump function graph. Pump function graphs were determined in three groups: control (n = 9), atrial pacing (n = 8), and halothane (n = 5). We compared the ratio of peripheral and source resistance at the working point and at the point of optimal work output (expressed in steady ventricular power). It could be shown that, in all investigated groups, the power optimum and the working point coincide. It was concluded that circulatory control in the intact anesthetized cat keeps the ventricle at optimal work output under the conditions studied.

Interaction of heart and arterial system.

We have studied the interrelation of left ventricle and arterial system in the anesthetized open-thorax cat. The ventricle was characterized by its pump function graph, relating mean ventricular pressure (Plv) and mean aortic flow (F). The pump function graph was determined by means of an artificial periphery and on a beat-to-beat basis. The periphery was characterized by relating mean aortic pressure (Pao) and mean flow. Mean aortic and mean left ventricular pressure could be related over a wide range of values by a proportionality factor Pao = a . Plv. In a series of five separate experiments a value of a = 1.72 +/- 0.14 (mean +/- SD) was found. This simplified relation allows direct comparison of apparent source resistance (i.e., slope of pump function graph), (Rs), and peripheral resistance (Rp). It was also found experimentally that total external power (w) could be calculated from mean aortic pressure and mean flow as well as from mean left ventricular pressure and mean flow (thus from the pump function graph) by w = c . Pao . F = c . a . Plv . F. The value of c = 1.16 +/- 0.12 (mean +/- SD, n = 4). Maximum external power was predicted for Rp/Rs = Pao/Plv = a. In six different cats Rp/Rs ratio in the working point (i.e., mean left ventricular pressure and mean flow when the normal periphery loaded the heart) was found to be Rp/Rs = 2.63 +/- 0.92. This value could not be shown to differ from that in the point where maximal external power was found, i.e., Rp/Rs = 1.81 +/- 0.08 (n = 6).

The effect of common carotid artery occlusion on blood pressure in the barodenervated cat.

A 12% blood pressure elevation was found during common carotid occlusion in the barodenervated, thoracotomised cat under Nembutal anaesthesia. This rise in blood pressure appeared to be the net result of an 18% increase of total peripheral resistance and a concomitant 5% decrease of mean aortic flow. When the occlusions were repeated after ganglionic blockade similar values were found, indicating that the increase in resistance had not resulted from reflex vasoconstriction. To test if this increase of total peripheral resistance was caused by a mechanical exclusion, Ohm's law for parallel resistances was applied to the systemic tree to calculate the rise in resistance due to obstruction of the carotid flow. The results thus obtained matched the observed increase of peripheal resistance. It is concluded that common carotid artery occlusion can be used to test completeness of barodenervation in the cat, if an increase in blood pressure of about 12% is allowed for.