Pacemaker Channels and the Chronotropic Response in Health and Disease

Loss or dysregulation of the normally precise control of heart rate via the autonomic nervous system plays a critical role during the development and progression of cardiovascular disease-including ischemic heart disease, heart failure, and arrhythmias. While the clinical significance of regulating changes in heart rate, known as the chronotropic effect, is undeniable, the mechanisms controlling these changes remain not fully understood. Heart rate acceleration and deceleration are mediated by increasing or decreasing the spontaneous firing rate of pacemaker cells in the sinoatrial node. During the transition from rest to activity, sympathetic neurons stimulate these cells by activating β-adrenergic receptors and increasing intracellular cyclic adenosine monophosphate. The same signal transduction pathway is targeted by positive chronotropic drugs such as norepinephrine and dobutamine, which are used in the treatment of cardiogenic shock and severe heart failure. The cyclic adenosine monophosphate-sensitive hyperpolarization-activated current (If) in pacemaker cells is passed by hyperpolarization-activated cyclic nucleotide-gated cation channels and is critical for generating the autonomous heartbeat. In addition, this current has been suggested to play a central role in the chronotropic effect. Recent studies demonstrate that cyclic adenosine monophosphate-dependent regulation of HCN4 (hyperpolarization-activated cyclic nucleotide-gated cation channel isoform 4) acts to stabilize the heart rate, particularly during rapid rate transitions induced by the autonomic nervous system. The mechanism is based on creating a balance between firing and recently discovered nonfiring pacemaker cells in the sinoatrial node. In this way, hyperpolarization-activated cyclic nucleotide-gated cation channels may protect the heart from sinoatrial node dysfunction, secondary arrhythmia of the atria, and potentially fatal tachyarrhythmia of the ventricles. Here, we review the latest findings on sinoatrial node automaticity and discuss the physiological and pathophysiological role of HCN pacemaker channels in the chronotropic response and beyond.

Missing Heritability in Albinism: Deep Characterization of a Hungarian Albinism Cohort Raises the Possibility of the Digenic Genetic Background of the Disease

Albinism is characterized by a variable degree of hypopigmentation affecting the skin and the hair, and causing ophthalmologic abnormalities. Its oculocutaneous, ocular and syndromic forms follow an autosomal or X-linked recessive mode of inheritance, and 22 disease-causing genes are implicated in their development. Our aim was to clarify the genetic background of a Hungarian albinism cohort. Using a 22-gene albinism panel, the genetic background of 11 of the 17 Hungarian patients was elucidated. In patients with unidentified genetic backgrounds (n = 6), whole exome sequencing was performed. Our investigations revealed a novel, previously unreported rare variant (N687S) of the two-pore channel two gene (TPCN2). The N687S variant of the encoded TPC2 protein is carried by a 15-year-old Hungarian male albinism patient and his clinically unaffected mother. Our segregational analysis and in vitro functional experiments suggest that the detected novel rare TPCN2 variant alone is not a disease-causing variant in albinism. Deep genetic analyses of the family revealed that the patient also carries a phenotype-modifying R305W variant of the OCA2 protein, and he is the only family member harboring this genotype. Our results raise the possibility that this digenic combination might contribute to the observed differences between the patient and the mother, and found the genetic background of the disease in his case.

Hyperpolarization-activated cyclic nucleotide-gated cation channel 3 promotes HCC development in a female-biased manner

Sex differences in hepatocellular carcinoma (HCC) development are regulated by sex and non-sex chromosomes, sex hormones, and environmental factors. We previously reported that Ncoa5+/- mice develop HCC in a male-biased manner. Here we show that NCOA5 expression is reduced in male patient HCCs while the expression of an NCOA5-interacting tumor suppressor, TIP30, is lower in female HCCs. Tip30 heterozygous deletion does not change HCC incidence in Ncoa5+/- male mice but dramatically increases HCC incidence in Ncoa5+/- female mice, accompanied by hepatic hyperpolarization-activated cyclic nucleotide-gated cation channel 3 (HCN3) overexpression. HCN3 overexpression cooperates with MYC to promote mouse HCC development, whereas Hcn3 knockout preferentially hinders HCC development in female mice. Furthermore, HCN3 amplification and overexpression occur in human HCCs and correlate with a poorer prognosis of patients in a female-biased manner. Our results suggest that TIP30 and NCOA5 protect against female liver oncogenesis and that HCN3 is a female-biased HCC driver.

mRNA trans-splicing dual AAV vectors for (epi)genome editing and gene therapy

Large genes including several CRISPR-Cas modules like gene activators (CRISPRa) require dual adeno-associated viral (AAV) vectors for an efficient in vivo delivery and expression. Current dual AAV vector approaches have important limitations, e.g., low reconstitution efficiency, production of alien proteins, or low flexibility in split site selection. Here, we present a dual AAV vector technology based on reconstitution via mRNA trans-splicing (REVeRT). REVeRT is flexible in split site selection and can efficiently reconstitute different split genes in numerous in vitro models, in human organoids, and in vivo. Furthermore, REVeRT can functionally reconstitute a CRISPRa module targeting genes in various mouse tissues and organs in single or multiplexed approaches upon different routes of administration. Finally, REVeRT enabled the reconstitution of full-length ABCA4 after intravitreal injection in a mouse model of Stargardt disease. Due to its flexibility and efficiency REVeRT harbors great potential for basic research and clinical applications.

The Concise Guide to PHARMACOLOGY 2023/24: Ion channels

The Concise Guide to PHARMACOLOGY 2023/24 is the sixth in this series of biennial publications. The Concise Guide provides concise overviews, mostly in tabular format, of the key properties of approximately 1800 drug targets, and over 6000 interactions with about 3900 ligands. There is an emphasis on selective pharmacology (where available), plus links to the open access knowledgebase source of drug targets and their ligands (https://www.guidetopharmacology.org/), which provides more detailed views of target and ligand properties. Although the Concise Guide constitutes almost 500 pages, the material presented is substantially reduced compared to information and links presented on the website. It provides a permanent, citable, point-in-time record that will survive database updates. The full contents of this section can be found at http://onlinelibrary.wiley.com/doi/10.1111/bph.16178. Ion channels are one of the six major pharmacological targets into which the Guide is divided, with the others being: G protein-coupled receptors, nuclear hormone receptors, catalytic receptors, enzymes and transporters. These are presented with nomenclature guidance and summary information on the best available pharmacological tools, alongside key references and suggestions for further reading. The landscape format of the Concise Guide is designed to facilitate comparison of related targets from material contemporary to mid-2023, and supersedes data presented in the 2021/22, 2019/20, 2017/18, 2015/16 and 2013/14 Concise Guides and previous Guides to Receptors and Channels. It is produced in close conjunction with the Nomenclature and Standards Committee of the International Union of Basic and Clinical Pharmacology (NC-IUPHAR), therefore, providing official IUPHAR classification and nomenclature for human drug targets, where appropriate.

In vivo and ex vivo electrophysiological study of the mouse heart to characterize the cardiac conduction system, including atrial and ventricular vulnerability

The mouse is a common and cost-effective animal model for basic research, and the number of genetically engineered mouse models with cardiac phenotype is increasing. In vivo electrophysiological study in mice is similar to that performed in humans. It is indispensable for acquiring intracardiac electrocardiogram recordings and determining baseline cardiac cycle intervals. Furthermore, the use of programmed electrical stimulation enables determination of parameters such as sinoatrial conduction time, sinus node recovery time, atrioventricular-nodal conduction properties, Wenckebach periodicity, refractory periods and arrhythmia vulnerability. This protocol describes specific procedures for determining these parameters that were adapted from analogous human protocols for use in mice. We include details of ex vivo electrophysiological study, which provides detailed insights into intrinsic cardiac electrophysiology without external influences from humoral and neural factors. In addition, we describe a heart preparation with intact innervation by the vagus nerve that can be used as an ex vivo model for vagal control of the cardiac conduction system. Data acquisition for in vivo and ex vivo electrophysiological study takes ~1 h per mouse, depending on the number of stimulation protocols applied during the procedure. The technique yields highly reliable results and can be used for phenotyping of cardiac disease models, elucidating disease mechanisms and confirming functional improvements in gene therapy approaches as well as for drug and toxicity testing.

THE CONCISE GUIDE TO PHARMACOLOGY 2021/22: Ion channels

The Concise Guide to PHARMACOLOGY 2021/22 is the fifth in this series of biennial publications. The Concise Guide provides concise overviews, mostly in tabular format, of the key properties of nearly 1900 human drug targets with an emphasis on selective pharmacology (where available), plus links to the open access knowledgebase source of drug targets and their ligands (www.guidetopharmacology.org), which provides more detailed views of target and ligand properties. Although the Concise Guide constitutes over 500 pages, the material presented is substantially reduced compared to information and links presented on the website. It provides a permanent, citable, point-in-time record that will survive database updates. The full contents of this section can be found at http://onlinelibrary.wiley.com/doi/bph.15539. Ion channels are one of the six major pharmacological targets into which the Guide is divided, with the others being: G protein-coupled receptors, nuclear hormone receptors, catalytic receptors, enzymes and transporters. These are presented with nomenclature guidance and summary information on the best available pharmacological tools, alongside key references and suggestions for further reading. The landscape format of the Concise Guide is designed to facilitate comparison of related targets from material contemporary to mid-2021, and supersedes data presented in the 2019/20, 2017/18, 2015/16 and 2013/14 Concise Guides and previous Guides to Receptors and Channels. It is produced in close conjunction with the Nomenclature and Standards Committee of the International Union of Basic and Clinical Pharmacology (NC-IUPHAR), therefore, providing official IUPHAR classification and nomenclature for human drug targets, where appropriate.

Speeding Up the Heart? Traditional and New Perspectives on HCN4 Function

The sinoatrial node (SAN) is the primary pacemaker of the heart and is responsible for generating the intrinsic heartbeat. Within the SAN, spontaneously active pacemaker cells initiate the electrical activity that causes the contraction of all cardiomyocytes. The firing rate of pacemaker cells depends on the slow diastolic depolarization (SDD) and determines the intrinsic heart rate (HR). To adapt cardiac output to varying physical demands, HR is regulated by the autonomic nervous system (ANS). The sympathetic and parasympathetic branches of the ANS innervate the SAN and regulate the firing rate of pacemaker cells by accelerating or decelerating SDD-a process well-known as the chronotropic effect. Although this process is of fundamental physiological relevance, it is still incompletely understood how it is mediated at the subcellular level. Over the past 20 years, most of the work to resolve the underlying cellular mechanisms has made use of genetically engineered mouse models. In this review, we focus on the findings from these mouse studies regarding the cellular mechanisms involved in the generation and regulation of the heartbeat, with particular focus on the highly debated role of the hyperpolarization-activated cyclic nucleotide-gated cation channel HCN4 in mediating the chronotropic effect. By focusing on experimental data obtained in mice and humans, but not in other species, we outline how findings obtained in mice relate to human physiology and pathophysiology and provide specific information on how dysfunction or loss of HCN4 channels leads to human SAN disease.

Beyond pacemaking: HCN channels in sinoatrial node function

Hyperpolarization-activated cyclic nucleotide-gated (HCN) channels are key proteins involved in the initiation and regulation of the heartbeat. Pacemaker cells within the sinoatrial node generate the electrical impulse that underlies the contraction of all atrial and ventricular cardiomyocytes. To generate a stable heart rhythm, it is necessary that the spontaneous activity of pacemaker cells is synchronized. Entrainment processes in the sinoatrial node create synchrony and also mediate heart rate regulation. In the past years it has become clear that the role of HCN channels goes beyond just pacemaking and that the channels play pivotal roles in these entrainment processes that coordinate and balance sinoatrial node network activity. Here, we review the role of HCN channels in the central pacemaker process and highlight new aspects of the contribution of HCN channels to stabilizing the electrical activity of the sinoatrial node network, especially during heart rate regulation by the autonomic nervous system.

Implantation of Combined Telemetric ECG and Blood Pressure Transmitters to Determine Spontaneous Baroreflex Sensitivity in Conscious Mice

Blood pressure (BP) and heart rate (HR) are both controlled by the autonomic nervous system (ANS) and are closely intertwined due to reflex mechanisms. The baroreflex is a key homeostatic mechanism to counteract acute, short-term changes in arterial BP and to maintain BP in a relatively narrow physiological range. BP is sensed by baroreceptors located in the aortic arch and carotid sinus. When BP changes, signals are transmitted to the central nervous system and are then communicated to the parasympathetic and sympathetic branches of the autonomic nervous system to adjust HR. A rise in BP causes a reflex decrease in HR, a drop in BP causes a reflex increase in HR. Baroreflex sensitivity (BRS) is the quantitative relationship between changes in arterial BP and corresponding changes in HR. Cardiovascular diseases are often associated with impaired baroreflex function. In various studies reduced BRS has been reported in e.g., heart failure, myocardial infarction, or coronary artery disease. Determination of BRS requires information from both BP and HR, which can be recorded simultaneously using telemetric devices. The surgical procedure is described beginning with the insertion of the pressure sensor into the left carotid artery and positioning of its tip in the aortic arch to monitor arterial pressure followed by the subcutaneous placement of the transmitter and ECG electrodes. We also describe postoperative intensive care and analgesic management. After a two-week period of post-surgery recovery long-term ECG and BP recordings are performed in conscious and unrestrained mice. Finally, we include examples of high-quality recordings and the analysis of spontaneous baroreceptor sensitivity using the sequence method.

A gene therapy for inherited blindness using dCas9-VPR-mediated transcriptional activation

Catalytically inactive dCas9 fused to transcriptional activators (dCas9-VPR) enables activation of silent genes. Many disease genes have counterparts, which serve similar functions but are expressed in distinct cell types. One attractive option to compensate for the missing function of a defective gene could be to transcriptionally activate its functionally equivalent counterpart via dCas9-VPR. Key challenges of this approach include the delivery of dCas9-VPR, activation efficiency, long-term expression of the target gene, and adverse effects in vivo. Using dual adeno-associated viral vectors expressing split dCas9-VPR, we show efficient transcriptional activation and long-term expression of cone photoreceptor-specific M-opsin (Opn1mw) in a rhodopsin-deficient mouse model for retinitis pigmentosa. One year after treatment, this approach yields improved retinal function and attenuated retinal degeneration with no apparent adverse effects. Our study demonstrates that dCas9-VPR-mediated transcriptional activation of functionally equivalent genes has great potential for the treatment of genetic disorders.

Abolishing cAMP sensitivity in HCN2 pacemaker channels induces generalized seizures

Hyperpolarization-activated cyclic nucleotide-gated (HCN) channels are dually gated channels that are operated by voltage and by neurotransmitters via the cAMP system. cAMP-dependent HCN regulation has been proposed to play a key role in regulating circuit behavior in the thalamus. By analyzing a knockin mouse model (HCN2EA), in which binding of cAMP to HCN2 was abolished by 2 amino acid exchanges (R591E, T592A), we found that cAMP gating of HCN2 is essential for regulating the transition between the burst and tonic modes of firing in thalamic dorsal-lateral geniculate (dLGN) and ventrobasal (VB) nuclei. HCN2EA mice display impaired visual learning, generalized seizures of thalamic origin, and altered NREM sleep properties. VB-specific deletion of HCN2, but not of HCN4, also induced these generalized seizures of the absence type, corroborating a key role of HCN2 in this particular nucleus for controlling consciousness. Together, our data define distinct pathological phenotypes resulting from the loss of cAMP-mediated gating of a neuronal HCN channel.

Disturbed Processing of Contextual Information in HCN3 Channel Deficient Mice

Hyperpolarization-activated cyclic nucleotide-gated channels (HCNs) in the nervous system are implicated in a variety of neuronal functions including learning and memory, regulation of vigilance states and pain. Dysfunctions or genetic loss of these channels have been shown to cause human diseases such as epilepsy, depression, schizophrenia, and Parkinson's disease. The physiological functions of HCN1 and HCN2 channels in the nervous system have been analyzed using genetic knockout mouse models. By contrast, there are no such genetic studies for HCN3 channels so far. Here, we use a HCN3-deficient (HCN3^−/−) mouse line, which has been previously generated in our group to examine the expression and function of this channel in the CNS. Specifically, we investigate the role of HCN3 channels for the regulation of circadian rhythm and for the determination of behavior. Contrary to previous suggestions we find that HCN3^−/− mice show normal visual, photic, and non-photic circadian function. In addition, HCN3^−/− mice are impaired in processing contextual information, which is characterized by attenuated long-term extinction of contextual fear and increased fear to a neutral context upon repeated exposure.

KCNMA1 encoded cardiac BK channels afford protection against ischemia-reperfusion injury

Mitochondrial potassium channels have been implicated in myocardial protection mediated through pre-/postconditioning. Compounds that open the Ca2+- and voltage-activated potassium channel of big-conductance (BK) have a pre-conditioning-like effect on survival of cardiomyocytes after ischemia/reperfusion injury. Recently, mitochondrial BK channels (mitoBKs) in cardiomyocytes were implicated as infarct-limiting factors that derive directly from the KCNMA1 gene encoding for canonical BKs usually present at the plasma membrane of cells. However, some studies challenged these cardio-protective roles of mitoBKs. Herein, we present electrophysiological evidence for paxilline- and NS11021-sensitive BK-mediated currents of 190 pS conductance in mitoplasts from wild-type but not BK-/- cardiomyocytes. Transmission electron microscopy of BK-/- ventricular muscles fibres showed normal ultra-structures and matrix dimension, but oxidative phosphorylation capacities at normoxia and upon re-oxygenation after anoxia were significantly attenuated in BK-/- permeabilized cardiomyocytes. In the absence of BK, post-anoxic reactive oxygen species (ROS) production from cardiomyocyte mitochondria was elevated indicating that mitoBK fine-tune the oxidative state at hypoxia and re-oxygenation. Because ROS and the capacity of the myocardium for oxidative metabolism are important determinants of cellular survival, we tested BK-/- hearts for their response in an ex-vivo model of ischemia/reperfusion (I/R) injury. Infarct areas, coronary flow and heart rates were not different between wild-type and BK-/- hearts upon I/R injury in the absence of ischemic pre-conditioning (IP), but differed upon IP. While the area of infarction comprised 28±3% of the area at risk in wild-type, it was increased to 58±5% in BK-/- hearts suggesting that BK mediates the beneficial effects of IP. These findings suggest that cardiac BK channels are important for proper oxidative energy supply of cardiomyocytes at normoxia and upon re-oxygenation after prolonged anoxia and that IP might indeed favor survival of the myocardium upon I/R injury in a BK-dependent mode stemming from both mitochondrial post-anoxic ROS modulation and non-mitochondrial localizations.

Sick sinus syndrome in HCN1-deficient mice

BACKGROUND

Sinus node dysfunction (SND) is a major clinically relevant disease that is associated with sudden cardiac death and requires surgical implantation of electric pacemaker devices. Frequently, SND occurs in heart failure and hypertension, conditions that lead to electric instability of the heart. Although the pathologies of acquired SND have been studied extensively, little is known about the molecular and cellular mechanisms that cause congenital SND.

METHODS AND RESULTS

Here, we show that the HCN1 protein is highly expressed in the sinoatrial node and is colocalized with HCN4, the main sinoatrial pacemaker channel isoform. To characterize the cardiac phenotype of HCN1-deficient mice, a detailed functional characterization of pacemaker mechanisms in single isolated sinoatrial node cells, explanted beating sinoatrial node preparation, telemetric in vivo electrocardiography, echocardiography, and in vivo electrophysiology was performed. On the basis of these experiments we demonstrate that mice lacking the pacemaker channel HCN1 display congenital SND characterized by bradycardia, sinus dysrhythmia, prolonged sinoatrial node recovery time, increased sinoatrial conduction time, and recurrent sinus pauses. As a consequence of SND, HCN1-deficient mice display a severely reduced cardiac output.

CONCLUSIONS

We propose that HCN1 stabilizes the leading pacemaker region within the sinoatrial node and hence is crucial for stable heart rate and regular beat-to-beat variation. Furthermore, we suggest that HCN1-deficient mice may be a valuable genetic disease model for human SND.

Up-regulation of hyperpolarization-activated cyclic nucleotide-gated channel 3 (HCN3) by specific interaction with K+ channel tetramerization domain-containing protein 3 (KCTD3)

Most ion channels consist of the principal ion-permeating core subunit(s) and accessory proteins that are assembled with the channel core. The biological functions of the latter proteins are diverse and include the regulation of the biophysical properties of the ion channel, its connection to signaling pathways and the control of its cell surface expression. There is recent evidence that native hyperpolarization-activated cyclic nucleotide-gated channel complexes (HCN1-4) also contain accessory subunits, among which TRIP8b (tetratricopeptide repeat-containing Rab8b-interacting protein) has been most extensively studied. Here, we identify KCTD3, a so far uncharacterized member of the potassium channel tetramerization-domain containing (KCTD) protein family as an HCN3-interacting protein. KCTD3 is widely expressed in brain and some non-neuronal tissues and colocalizes with HCN3 in specific regions of the brain including hypothalamus. Within the HCN channel family, KCTD3 specifically binds to HCN3 and leads to a profound up-regulation of cell surface expression and current density of this channel. HCN3 can also functionally interact with TRIP8b; however, we found no evidence for channel complexes containing both TRIP8b and KCTD3. The C terminus of HCN3 is crucially required for functional interaction with KCTD3. Replacement of the cytosolic C terminus of HCN2 by the corresponding domain of HCN3 renders HCN2 sensitive to regulation by KCTD3. The C-terminal-half of KCTD3 is sufficient for binding to HCN3. However, the complete protein including the N-terminal tetramerization domain is needed for HCN3 current up-regulation. Together, our experiments indicate that KCTD3 is an accessory subunit of native HCN3 complexes.

The role of HCN channels in ventricular repolarization

Hyperpolarization-activated cyclic nucleotide gated (HCN) channels pass a cationic current (I(h)/I(f)) that crucially contributes to the slow diastolic depolarization (SDD) of sinoatrial pacemaker cells and, hence, is a key determinant of cardiac automaticity and the generation of the heartbeat. However, there is growing evidence that HCN channels are not restricted to the spontaneously active cells of the sinoatrial node and the conduction system but are also present in ventricular cardiomyocytes that produce an action potential lacking SDD. This observation raises the question of the principal function(s) of HCN channels in working myocardium. Our recent analysis of an HCN3-deficient (HCN3-/-) mouse line has shed new light on this central question. We propose that HCN channels contribute to the ventricular action potential waveform, specifically during late repolarization. In this review, we outline this new concept.

Complex regulation of voltage-dependent activation and inactivation properties of retinal voltage-gated Cav1.4 L-type Ca2+ channels by Ca2+-binding protein 4 (CaBP4)

Cav1.4 L-type Ca(2+) channels are crucial for synaptic transmission in retinal photoreceptors and bipolar neurons. Recent studies suggest that the activity of this channel is regulated by the Ca(2+)-binding protein 4 (CaBP4). In the present study, we explored this issue by examining functional effects of CaBP4 on heterologously expressed Cav1.4. We show that CaBP4 dramatically increases Cav1.4 channel availability. This effect crucially depends on the presence of the C-terminal ICDI (inhibitor of Ca(2+)-dependent inactivation) domain of Cav1.4 and is absent in a Cav1.4 mutant lacking the ICDI. Using FRET experiments, we demonstrate that CaBP4 interacts with the IQ motif of Cav1.4 and that it interferes with the binding of the ICDI domain. Based on these findings, we suggest that CaBP4 increases Cav1.4 channel availability by relieving the inhibitory effects of the ICDI domain on voltage-dependent Cav1.4 channel gating. We also functionally characterized two CaBP4 mutants that are associated with a congenital variant of human night blindness and other closely related nonstationary retinal diseases. Although both mutants interact with Cav1.4 channels, the functional effects of CaBP4 mutants are only partially preserved, leading to a reduction of Cav1.4 channel availability and loss of function. In conclusion, our study sheds new light on the functional interaction between CaBP4 and Cav1.4. Moreover, it provides insights into the mechanism by which CaBP4 mutants lead to loss of Cav1.4 function and to retinal disease.

Regulation of hyperpolarization-activated cyclic nucleotide-gated (HCN) channel activity by cCMP

Activation of hyperpolarization-activated cyclic nucleotide-gated (HCN) channels is facilitated in vivo by direct binding of the second messenger cAMP. This process plays a fundamental role in the fine-tuning of HCN channel activity and is critical for the modulation of cardiac and neuronal rhythmicity. Here, we identify the pyrimidine cyclic nucleotide cCMP as another regulator of HCN channels. We demonstrate that cCMP shifts the activation curves of two members of the HCN channel family, HCN2 and HCN4, to more depolarized voltages. Moreover, cCMP speeds up activation and slows down deactivation kinetics of these channels. The two other members of the HCN channel family, HCN1 and HCN3, are not sensitive to cCMP. The modulatory effect of cCMP is reversible and requires the presence of a functional cyclic nucleotide-binding domain. We determined an EC(50) value of ∼30 μm for cCMP compared with 1 μm for cAMP. Notably, cCMP is a partial agonist of HCN channels, displaying an efficacy of ∼0.6. cCMP increases the frequency of pacemaker potentials from isolated sinoatrial pacemaker cells in the presence of endogenous cAMP concentrations. Electrophysiological recordings indicated that this increase is caused by a depolarizing shift in the activation curve of the native HCN current, which in turn leads to an enhancement of the slope of the diastolic depolarization of sinoatrial node cells. In conclusion, our findings establish cCMP as a gating regulator of HCN channels and indicate that this cyclic nucleotide has to be considered in HCN channel-regulated processes.

HCN3 contributes to the ventricular action potential waveform in the murine heart

RATIONALE

The hyperpolarization-activated current I(h) that is generated by hyperpolarization-activated cyclic nucleotide-gated channels (HCNs) plays a key role in the control of pacemaker activity in sinoatrial node cells of the heart. By contrast, it is unclear whether I(h) is also relevant for normal function of cardiac ventricles.

OBJECTIVE

To study the role of the HCN3-mediated component of ventricular I(h) in normal ventricular function.

METHODS AND RESULTS

To test the hypothesis that HCN3 regulates the ventricular action potential waveform, we have generated and analyzed a HCN3-deficient mouse line. At basal heart rate, mice deficient for HCN3 displayed a profound increase in the T-wave amplitude in telemetric electrocardiographic measurements. Action potential recordings on isolated ventricular myocytes indicate that this effect was caused by an acceleration of the late repolarization phase in epicardial myocytes. Furthermore, the resting membrane potential was shifted to more hyperpolarized potentials in HCN3-deficient mice. Cardiomyocytes of HCN3-deficient mice displayed approximately 30% reduction of total I(h). At physiological ionic conditions, the HCN3-mediated current had a reversal potential of approximately -35 mV and displayed ultraslow deactivation kinetics.

CONCLUSIONS

We propose that HCN3 together with other members of the HCN channel family confer a depolarizing background current that regulates ventricular resting potential and counteracts the action of hyperpolarizing potassium currents in late repolarization. In conclusion, our data indicate that HCN3 plays an important role in shaping the cardiac action potential waveform.

The influence of HAART on the efficacy and safety of pegylated interferon and ribavirin therapy for the treatment of chronic HCV infection in HIV-positive Individuals

Objective

This study was performed to investigate the impact of HAART versus no HAART and nucleoside free versus nucleoside containing HAART on the efficacy and safety of pegylated interferon and ribavirin therapy for the treatment of chronic HCV infection in HIV/HCV co-infected patients. In addition a control group of HCV mono-infected patients undergoing anti-HCV therapy was evaluated.

Methods

Multicenter, partially randomized, controlled clinical trial. HIV-negative and -positive patients with chronic HCV infection were treated with pegylated interferon alfa-2a and ribavirin (800 - 1200 mg/day) for 24 - 48 weeks in one of four treatment arms: HIV-negative (A), HIV-positive without HAART (B) and HIV-positive on HAART (C). Patients within arm C were randomized to receive open label either a nucleoside containing (C1) or a nucleoside free HAART (C2).

Results

168 patients were available for analysis. By intent-to-treat analysis similar sustained virological response rates (SVR, negative HCV-RNA 24 weeks after the end of therapy) were observed comparing HIV-negative and -positive patients (54% vs. 54%, p = 1.000). Among HIV-positive patients SVR rates were similar between patients off and on HAART (57% vs. 52%, p = 0.708). Higher SVR rates were observed in patients on a nucleoside free HAART compared to patients on a nucleoside containing HAART, though confounding could not be ruled out and in the intent-to-treat analysis the difference was not statistically significant (64% vs. 46%, p = 0.209).

Conclusions

Similar response rates for HCV therapy can be achieved in HIV-positive and -negative patients. Patients on nucleoside free HAART reached at least equal rates of sustained virological response compared to patients on standard HAART.

Epidemiological composition, clinical and treatment characteristics of the patient cohort of the German Competence Network for HIV/AIDS

Objective

As its central basis for research, the Competence Network for HIV/AIDS (KompNet) established a nationwide cohort study on HIV-positive patients being in medical care in Germany. In this paper, we describe the epidemiological composition, and clinical as well as treatment characteristics of the KompNet cohort over time.

Methods

The KompNet cohort is an open, retrospective and prospective, multi-center, disease-specific and nationwide cohort study that started gathering data in June 2004. Semiannually, follow up visits of the patients are documented, covering a wide range of clinical and sociodemographic data. At enrolment and three years afterwards, an EDTA-sample is taken; a serum-sample is taken at every follow up.

Results

As of 20.10.2008, a total of 15,541 patients were enrolled by 44 documenting sites. In September 2007, the cohort size was reduced to ten outpatient clinics and fifteen private practitioners, covering a total of 9,410 patients. The documentation of these patients comprised 24,117 years of follow up-time since enrolment (mean: 2.6 years), 62,862 person years inclusive data documented retrospectively on course of HIV-infection and antiretroviral therapy (ART, mean: 6.7 years). Due to the short period of recruitment till now, rates of death (0.3%-0.8%) and losses to follow up (1.1%-5.5%) were low.

84.9% of patients were men. Main risk of transmission was sex between men (MSM: 62.9%). Mean age was 45 years. About two third of patients were classified as CDC-stage B or C. Therapy regimens of currently treated patients complied with recent guidelines. Trends of mean CD4 cell count/μl regarding the initial therapy and concerning the population under treatment reflected the developments and the changing standards of antiretroviral therapy over time.

Conclusion

The KompNet cohort covers about a quarter of all patients estimated as being under treatment in Germany. Its composition can be accounted approximately representative for the situation of clinical care and treatment in the scope of HIV/AIDS in Germany. Therefore, it is an important instrument for measuring the course of HIV/AIDS, the reality of use of antiretroviral therapy and its clinical and psychosocial outcomes in Germany.

Treatment during primary HIV infection does not lower viral set point but improves CD4 lymphocytes in an observational cohort

Objective

To investigate if early treatment of primary HIV-1 infection (PHI) reduces viral set point and/or increases CD4 lymphocytes.

Methods

Analysis of two prospective multi-centre PHI cohorts. HIV-1 RNA and CD4 lymphocytes in patients with transient treatment were compared to those in untreated patients. Time to CD4 lymphocyte decrease below 350/μl after treatment stop or seroconversion was calculated using Kaplan-Meier and Cox-PH-regression analyses.

Results

156 cases of PHI were included, of which 100 had received transient HAART (median treatment time 9.5 months) and 56 remained untreated. Median viral load (563000 cop/ml vs 240000 cop/ml; p < 0.001) and median CD4 lymphocyte (449/μl vs. 613/μl; p < 0.01) differed significantly between treated and untreated patients. Median viral load was 38056 copies/ml in treated patients (12 months after treatment stop) and 52880 copies/ml in untreated patients (12 months after seroconversion; ns). Median CD4 lymphocyte change was +60/μl vs. -86/μl (p = 0.01). Median time until CD4 lymphocytes decreased to < 350/μl (including all patients with CD4 lymphocytes < 500/μl during seroconversion) was 20.7 months in treated patients after treatment stop and 8.3 months in untreated patents after seroconversion (p < 0.01). Cox-PH analyses adjusting for baseline VL, CD4 lymphocytes, stage of early infection and symptoms confirmed these differences.

Conclusions

Treatment during PHI did not lower viral set point. However, patients treated during seroconversion had an increase in CD4 lymphocytes, whereas untreated patients experienced a decrease in CD4 lymphocytes. Time until reaching CD4 lymphocytes < 350/μl was significantly shorter in untreated than in treated patients including patients with CD4 lymphocytes < 500/μl during seroconversion.

Switch from a ZDV/3TC-based regimen to a completely once daily (QD) regimen of emtricitabine/tenofovir DF fixed dose combination plus a third QD agent (SONETT)

Objectives

To assess the efficacy and safety of a treatment switch from a twice-daily (BID) regimen containing zidovudine (ZDV) and lamivudine (3TC) plus a third agent to a once daily (QD) regimen containing the fixed-dose combination of tenofovir DF/emtricitabine (TDF/FTC, Truvada^®) plus a divergent third QD agent in HIV-1 infected patients.

Methods

Prospective, 48-week, non-randomised, single-group, open-label, study. Fifty-one patients on stable ZDV/3TC-containing HAART, with HIV-1 RNA < 50 copies/ml and CD4+ T-cell count > 50 cells/μl, were switched to TDF/FTC plus a third agent. Plasma HIV-1 RNA, CD4+ and CD8+ T-cell counts were assessed at baseline and weeks 4, 12, 24, 36 and 48 post-switch.

Results

During the 48-week study, 10 patients discontinued prematurely, including three due to adverse events (AEs). At week 48, plasma HIV-1 RNA was < 50 copies/ml in 40 patients (78.4%). No patient experienced virological failure (defined as HIV-1 RNA ≥50 copies/ml at two consecutive post-baseline measurements) during the study. Immunologic control was maintained, with no significant changes in CD4+ or CD8+ T-cell counts. A statistically significant improvement from baseline in haemoglobin level was observed at week 48 (median change 0.8 g/dl; p < 0.001). There was also a statistically significant decrease in total cholesterol concentration at week 48 (-26.0 mg/dl; p = 0.001) in a subset of patients (n = 22) entering the study with elevated total cholesterol. Treatment was well tolerated and no treatment-related grade 3 or 4 AEs were seen.

Conclusions

Results from this study support switching from a ZDV/3TC-containing HAART regimen to a completely QD regimen of TDF/FTC plus a third agent. Virologic and immunologic control are maintained, with apparent benefits in haemoglobin.

The two-pore channel TPCN2 mediates NAADP-dependent Ca(2+)-release from lysosomal stores

Second messenger-induced Ca²⁺-release from intracellular stores plays a key role in a multitude of physiological processes. In addition to 1,4,5-inositol trisphosphate (IP₃), Ca²⁺, and cyclic ADP ribose (cADPR) that trigger Ca²⁺-release from the endoplasmatic reticulum (ER), nicotinic acid adenine dinucleotide phosphate (NAADP) has been identified as a cellular metabolite that mediates Ca²⁺-release from lysosomal stores. While NAADP-induced Ca²⁺-release has been found in many tissues and cell types, the molecular identity of the channel(s) conferring this release remained elusive so far. Here, we show that TPCN2, a novel member of the two-pore cation channel family, displays the basic properties of native NAADP-dependent Ca²⁺-release channels. TPCN2 transcripts are widely expressed in the body and encode a lysosomal protein forming homomers. TPCN2 mediates intracellular Ca²⁺-release after activation with low-nanomolar concentrations of NAADP while it is desensitized by micromolar concentrations of this second messenger and is insensitive to the NAADP analog nicotinamide adenine dinucleotide phosphate (NADP). Furthermore, TPCN2-mediated Ca²⁺-release is almost completely abolished when the capacity of lysosomes for storing Ca²⁺ is pharmacologically blocked. By contrast, TPCN2-specific Ca²⁺-release is unaffected by emptying ER-based Ca²⁺ stores. In conclusion, these findings indicate that TPCN2 is a major component of the long-sought lysosomal NAADP-dependent Ca²⁺-release channel.

TRIZAL study: switching from successful HAART to Trizivir (abacavir-lamivudine-zidovudine combination tablet): 48 weeks efficacy, safety and adherence results

OBJECTIVE

To assess the antiviral efficacy, safety, and adherence in subjects who switched to Trizivir following long-term HIV-1 RNA suppression.

STUDY DESIGN

A randomized, open-label, multicentre, 48-week comparative study in subjects who have received two nucleoside reverse transcriptase inhibitors plus a protease inhibitor or an nonnucleoside reverse transcriptase inhibitor or three nucleoside reverse transcriptase inhibitors for at least 6 months, with a history of undetectable plasma HIV-1 RNA since initiation of therapy and plasma viral load of < 50 HIV-1 RNA copies/mL at screening.

METHODS

Subjects were randomized 1:1 to continue their current treatment or to switch to a simplified treatment with Trizivir administered twice daily. Assessments included plasma HIV-1 RNA, lymphocyte counts, clinical laboratory evaluations, adverse events, and adherence to treatment (obtained via subject self-report). Treatment failure was defined as a plasma viral load of >/= 400 HIV-1 RNA copies/mL on two consecutive occasions or premature discontinuation of randomized treatment.

RESULTS

At week 48, the proportion of treatment failures in Trizivir arm (23/106, 22%) was noninferior to that observed in continued arm (23/103, 22%) with a treatment difference stratified by prior ART of 1.2%[-10.1; 12.5]. Incidence of adverse events was similar in both treatment groups. The incidence of possible hypersensitivity reaction in the Trizivir trade mark arm was 10%. Significant reductions in cholesterol and triglyceride plasma levels were observed in the Trizivir arm (P < 0.001 and P = 0.006, respectively).

CONCLUSION

Switching to Trizivir offers a potent and simplified regimen with equivalent efficacy and significant improvement in lipid abnormalities compared to continued triple therapy.

Long-term efficacy and safety of ritonavir/indinavir at 400/400 mg twice a day in combination with two nucleoside reverse transcriptase inhibitors as first line antiretroviral therapy

OBJECTIVE

To determine the long-term antiretroviral efficacy and tolerability of dual protease inhibitor (PI) therapy with indinavir (IDV)/ritonavir (RTV) at 400/400 mg twice a day (BID) in combination with two nucleoside reverse trancriptase inhibitors (NRTIs).

DESIGN AND METHODS

In an open-label, uncontrolled multicentre clinical trial, antiretroviral therapy naive patients (n = 93) with a high median baseline HIV-1 RNA level of 210 000 copies/mL (range 17 000-2 943 000) and a median CD4 cell count of 195 copies/microL (range 4-656 copies/microL) were started on a regimen of either zidovudine (ZDV)/lamivudine (3TC) (49%), stavudine (d4T)/3TC (38%) or d4T/didanosine (ddI) (14%) plus RTV and IDV, each at 400 mg BID. CD4 cell counts and HIV RNA were determined at 4-week intervals for a duration of 72 weeks. Statistical analysis was performed on treatment as well as by intent to treat, where missing values were counted as failures.

RESULTS

HIV RNA levels below the limit of detection were achieved in 59.5% (< 80 copies/mL) and 63% (< 500 copies/mL) of patients according to the intent to treat analysis at week 72. In the on treatment analysis, the proportion of patients reaching an undetectable viral load was 94.5% (< 80 copies/mL) and 100% (< 500 copies/mL), respectively. Apart from diarrhoea and nausea, serum lipid abnormalities were identified as the most prominent adverse reaction. No cases of nephrotoxicity occurred during the entire observation period of 72 weeks.

CONCLUSIONS

Our results demonstrate that quadruple therapy with RTV/IDV and two NRTIs induces potent, durable and safe HIV suppression and might be particularly beneficial as a first line therapy for patients with a high baseline viral load.

Efficacy and safety of twice daily first-line ritonavir/indinavir plus double nucleoside combination therapy in HIV-infected individuals. German Ritonavir/Indinavir Study Group

OBJECTIVE

To evaluate the virological efficacy and safety of quadruple therapy with two nucleoside analogues and ritonavir (400 mg twice daily) plus indinavir (400 mg twice daily) combination in antiretroviral therapy-naive patients.

DESIGN AND METHODS

An open-label, uncontrolled multicentre trial. Antiretroviral therapy-naive patients (n = 90) with high median baseline HIV RNA levels of 220,000 copies/ml (range, 36,000-2,943,000 copies/ml) and median CD4 cell count of 189 x 10(6)/l (range, 4-656 x 10(6)/l) were started on a twice daily regimen of either zidovudine/lamivudine (49%), stavudine/lamivudine (38%) or stavudine/didanosine (13%) plus ritonavir 400 mg twice daily and indinavir 400 mg twice daily combination therapy. CD4 cell counts and HIV RNA were determined at weeks 0, 4, 8, 12, 16, 20, and 24. Statistical analysis was performed on treatment as well as intent-to-treat, where missing values were accounted for as failure.

RESULTS

In the intent-to-treat analysis at week 24, the proportion of patients with HIV RNA of < 500 copies/ml, and < 80 copies/ml was 86.7% and 71.1%, respectively. In the on-treatment analysis at week 24, 80.0% of patients had undetectable viral load in the ultrasensitive assay (< 80 copies/ml; n = 80). The quadruple therapy was well tolerated except for mild diarrhoea, initial nausea and increased triglyceride levels. Treatment was stopped in seven (7.7%) patients because of adverse events and three (3.3%) were lost to follow-up.

CONCLUSIONS

Our preliminary data suggest that the protease inhibitor combination ritonavir/indinavir plus double nucleoside therapy appears to be effective and safe in short-term treatment (up to 24 weeks).

Detection of melanoma micrometastases in the sentinel lymph node and in nonsentinel nodes by tyrosinase polymerase chain reaction

The aim of our study was to investigate the metastatic pathways of melanoma cells in sentinel and other regional lymph nodes. The term "sentinel lymph node" means that the first lymph node of the draining site of a primary tumor is never bypassed in malignant melanoma. In this case lymph node dissection would be necessary only when melanoma cells are detected in the sentinel node. Tyrosinase reverse transcriptase-polymerase chain reaction was applied to search for metastatic melanoma in the sentinel lymph node and in further lymph nodes of a complete lymph node basin in patients who underwent lymph node dissection. In 24 patients with malignant melanoma the draining site of the tumor was marked by lymphoscintigraphy and by intraoperative injection of patent blue V in the area around the primary tumor. The lymph nodes of the affected basin were excised and prepared for histopathologic, immunohistochemical, and molecular biologic examinations. Regarding the sentinel lymph node, 10 of 24 patients showed morphologic evidence for metastases, three additional patients showed only tyrosinase transcripts. In 11 of these 13 cases we found one or more nonsentinel lymph nodes with morphologically detectable melanoma cells and/or tyrosinase mRNA. Interestingly, in seven of 24 patients a positive tyrosinase reverse transcriptase-polymerase chain reaction was received in nonsentinel lymph nodes, whereas the sentinel lymph node was negative, not only for all histologic examinations but also by tyrosinase reverse transcriptase-polymerase chain reaction. In five of seven patients of the latter group, gp100 reverse transcriptase-polymerase chain reaction was carried out, showing also gp100 mRNA in nonsentinel lymph nodes only. Our data indicate that the concept of the sentinel lymph node may miss micrometastases. Whether such micrometastases cause a recurrence or a metastasis of malignant melanoma, or can be destroyed by the immune system, remains to be clarified.

Successful treatment of Toxoplasma gondii myocarditis in an AIDS patient

Central nervous system disease due to Toxoplasma gondii is a common cause of morbidity and mortality in patients with the acquired immunodeficiency syndrome. Cardiac toxoplasmosis, however, has been described in only a limited number of cases. In a 45-year-old patient with symptoms suggestive of myocarditis, Toxoplasma gondii was detected in myocardial tissue obtained by biopsy. After the institution of appropriate antiprotozoal therapy, the patient recovered. This patient is believed to be the first patient to survive biopsy-proven myocarditis caused by Toxoplasma gondii. Cardiac toxoplasmosis should be ruled out in HIV-infected patients presenting with high fever and/or cardiorespiratory symptoms and exhibiting serologic evidence of prior exposure to Toxoplasma gondii as determined by a positive IgG EIA, especially if the CD4+ count is low and no systemic Pneumocystis carinii pneumonia prophylaxis has been administered. A high index of clinical suspicion and, if necessary, invasive diagnostic tests, including myocardial biopsies, are most important in making the correct diagnosis.

[Double infection of the lung with Pneumocystis carinii and Cryptococcus neoformans in an AIDS patient]

A 25-year old HIV-1-positive hemophiliac was admitted with fever, cough, exertional dyspnea and pleuritic chest pain. Chest x-ray showed diffuse bilateral infiltrates with a left sided nodular consolidation. Pneumocystis-carinii-pneumonia was suspected and diagnosed by broncho-alveolar lavage. With therapy the diffuse infiltrates improved, but the nodule and the symptoms failed to resolve. A fine-needle aspiration of the nodule revealed concurrent cryptococcosis. Treatment with fluconazole resulted in complete resolution of symptoms. Details of the case are presented and clinical implications are discussed.

Risk factors for severe disease due to Toxoplasma gondii in HIV-positive patients

The objective of this study was to assess the risk of toxoplasmosis in HIV-positive subjects as a basis for primary prophylaxis. A retrospective chart review of 400 consecutive patients was carried out and clinical and laboratory markers at first presentation and follow-up data on the occurrence of toxoplasmosis were recorded. Independent variables were identified, laboratory parameters were stratified, and estimates for the risk of toxoplasmosis and the impact of different variables on its occurrence were made using conventional statistical methods. An increased risk of toxoplasmosis was strongly associated with a positive Toxoplasma gondii IgG EIA in conjunction with a CD4+ cell cont below 0.15/nl (the estimated risk of toxoplasmosis was 20% and 35% after 12 and 24 months, respectively) or a history of one or more opportunistic infections (the estimated risk was 12% and 30% after 12 and 24 months, respectively). Toxoplasma gondii-seropositive patients with CD4+ cell counts below 0.15/nl and those with antecedent opportunistic infections are most likely to develop toxoplasmosis and thus might benefit from primary prophylaxis. The risk of disease probably outweighs the risk of medication in these subjects. Prospective clinical trials are needed to define the optimal choice of drugs.

Antiviral and immunological effects of escalating low doses of zidovudine in HIV-positive patients

Twenty-eight patients with different stages of HIV infection who had not undergone antiretroviral pretreatment were treated with an escalating dose regimen of zidovudine (4 weeks 2 x 50 mg, 4 weeks 2 x 100 mg, 4 weeks 2 x 250 mg). CD4+ cell counts and p24 antigen levels were monitored every four weeks. Twenty-one patients were evaluable. p24 antigen levels showed a significant decrease after four weeks (p < 0.01, Sign test, Wilcoxon matched pairs test) that was sustained until week 12 without a further significant decrease. CD4+ cell counts increased significantly within the first four weeks (p < 0.01, Sign test, Wilcoxon matched pairs test). This increase was sustained until week 12 but no further significant increase was noted. Mean corpuscular erythrocyte volume values increased significantly after week 4 and continued to rise until week 12. These results demonstrate antiretroviral activity of a very low zidovudine dose, however low doses should not be used for treatment unless the clinical efficacy is shown to be equivalent to that of standard doses.

A novel variety of atypical Pneumocystis carinii infection after long-term prophylactic pentamidine inhalation in an AIDS patient: large lower lobe pneumocystoma

Atypical pulmonary manifestations of Pneumocystis carinii infection and fair numbers of extrapulmonary and disseminated infections have lately been documented in patients with human immunodeficiency virus infection treated prophylactically with inhalative pentamidine. We report the case of a 32-year-old homosexual patient who was assessed for complaints of night sweats, weight loss, and progressive malaise. The patient denied any respiratory tract symptoms such as cough, sputum production, pleuritic chest pain, or shortness of breath. Chest X-ray revealed two large round noncavitating lesions in the lower lobe of the right lung. Pneumocystomas were diagnosed by fine-needle aspiration. A 3-week course of intravenous high-dose cotrimoxazole resulted in amelioration of symptoms but no change in the radiographic appearance of the pulmonary lesions. Four months later the patient is alive and stable and is being treated with pentamidine inhalation of 300 mg per 2 weeks and two tablets of pyrimethamine sulfadoxine per week.

Rotavirus antigen detection in patients with HIV infection and diarrhea

A wide variety of bacterial, viral, and parasitic pathogens can cause severe diarrhea in patients with advanced human immunodeficiency virus (HIV) infection. The role of enteric viruses, especially rotaviruses, in HIV-related diarrhea is still unclear. One hundred and six stool samples from 66 HIV-infected patients with otherwise unexplained diarrhea and 35 samples from 35 patients with advanced HIV infection but without diarrhea were tested for the presence of rotavirus antigen. Rotavirus was detected in 13 samples from 9 patients with diarrhea and in none of the samples from patients without diarrhea. Two patients had recurrence of rotavirus infection more than 6 months after the first episode. Rotavirus was associated with prolonged diarrhea, often accompanied by abdominal cramping. Symptoms were readily controlled with anti-diarrheal and pain-relieving measures. Illness was self-limited and did not require hospitalization. A seasonal variation, typical of infantile rotavirus infection, was not observed in this setting. While rotavirus infection has been infrequently detected in American HIV-infected patients, the prevalence in Australia and Europe appears to be considerably higher.

Visceral leishmaniasis in an HIV-infected patient: clinical features and response to treatment

We report the case of 43-year-old homosexual patient with HIV infection and a history of travel to the Far East in whom visceral leishmaniasis was the first infectious complication. Symptoms were fever, malaise, weight loss, hepatosplenomegaly, generalized lymphadenopathy, and oral thrush. Laboratory abnormalities included a slight elevation of liver enzymes, impairment of liver function tests, leukocytopenia, anemia, hypergammaglobulinemia, and markedly depressed CD4(+)-cell counts. Despite initially successful treatment with pentavalent antimony, a relapse of leishmaniasis occurred after 7 months. Eradication of the infection was not achieved. Treatment was continued as a palliative chronic suppressive treatment with fortnightly pentamidine infusions. The clinical course was complicated by legionella pneumonia and the development of rapidly progressing Kaposi's sarcoma. The case is presented in detail, and the influence of HIV infection on the course of leishmaniasis is discussed.