Nanoparticle targeting of neutrophil glycolysis prevents lung ischemia-reperfusion injury

Neutrophils exacerbate pulmonary ischemia-reperfusion injury (IRI) resulting in poor short and long-term outcomes for lung transplant recipients. Glycolysis powers neutrophil activation, but it remains unclear if neutrophil-specific targeting of this pathway will inhibit IRI. Lipid nanoparticles containing the glycolysis flux inhibitor 2-deoxyglucose (2-DG) were conjugated to neutrophil-specific Ly6G antibodies (NP-Ly6G[2-DG]). Intravenously administered NP-Ly6G(2-DG) to mice exhibited high specificity for circulating neutrophils. NP-Ly6G(2-DG)-treated neutrophils were unable to adapt to hypoglycemic conditions of the lung airspace environment as evident by the loss of demand-induced glycolysis, reductions in glycogen and ATP content, and an increased vulnerability to apoptosis. NP-Ly6G(2-DG) treatment inhibited pulmonary IRI following hilar occlusion and orthotopic lung transplantation. IRI protection was associated with less airspace neutrophil extracellular trap generation, reduced intragraft neutrophilia, and enhanced alveolar macrophage efferocytotic clearance of neutrophils. Collectively, our data show that pharmacologically targeting glycolysis in neutrophils inhibits their activation and survival leading to reduced pulmonary IRI.

Defects in vein valve PROX1/FOXC2 antithrombotic pathway in endothelial cells drive the hypercoagulable state induced by trauma and critical illness

OBJECTIVES

Deep venous thrombosis (DVT) causes significant morbidity and mortality after trauma. Recently, we have shown that blood flow patterns at vein valves induce oscillatory stress genes, which maintain an anticoagulant endothelial phenotype that inhibits spontaneous clotting at vein valves and sinuses, is lost in the presence of DVT in human pathological samples, and is dependent on expression of the transcription factor FOXC2. We describe an assay, modifying our mouse multiple injury system, which shows evidence of clinically relevant microthrombosis and hypercoagulability applicable to the study of spontaneous DVT in trauma without requiring direct vascular injury or ligation. Finally, we investigated whether these model findings are relevant to a human model of critical illness by examining gene expression changes by quantitative polymerase chain reaction and immunofluorescence in veins collected from critically ill.

METHODS

C57/Bl6 mice were subjected to a modified mouse multiple injury model with liver crush injury, crush and pseudofracture of a single lower extremity, and 15% total blood volume hemorrhage. Serum was assayed for d-dimer at 2, 6, 24, and 48 hours after injury by enzyme-linked immunosorbent assay. For the thrombin clotting assay, veins of the leg were exposed, 100 μL of 1 mM rhodamine (6 g) was injected retro-orbitally, and 450 μg/mL thrombin was then applied to the surface of the vein with examination of real-time clot formation via in vivo immunofluorescence microscopy. Images were then examined for percentage area of clot coverage of visible mouse saphenous and common femoral vein. Vein valve specific knockout of FOXC2 was induced with tamoxifen treatment in PROX1 Ert2Cre FOXC2 fl/fl mice as previously described. Animals were then subjected to a modified mouse multiple injury model with liver crush injury, crush and pseudofracture of a single lower extremity, and 15% total blood volume hemorrhage. Twenty-four hours after injury, we examined the valve phenotype in naive versus multiple injury animals, with and without loss of the FOXC2 gene from the vein valve (FOXC2 del ) via the thrombin assay. Images were then examined for proximity of clot formation to the valve present at the junction of the mouse saphenous, tibial, and superficial femoral vein and presence of spontaneous microthrombi present in the veins before exposure to thrombin. Human vein samples were obtained from excess tissue preserved after harvest for elective cardiac surgery and from organ donors after organ procurement. Sections were submitted for paraffin embedding and then assayed by immunofluorescence for PROX1, FOXC2, thrombomodulin, endothelial protein C receptor, and von Willebrand's factor. All animal studies were reviewed and approved by the Institutional Animal Care and Use Committee, and all human studies reviewed and approved by the institutional review board.

RESULTS

After mouse multiple injuries, enzyme-linked immunosorbent assay for d-dimer showed evidence of products of fibrin breakdown consistent with formation of clot related to injury, fibrinolysis, and/or microthrombosis. The thrombin clotting assay demonstrated higher percentage area of vein covered with clot when exposed to thrombin in the multiple injury animals compared with uninjured (45% vs. 27% p = 0.0002) consistent with a phenotype of hypercoagulable state after trauma in our model system. Unmanipulated FoxC2 knockout mice manifest increased clotting at the vein valve as compared with unmanipulated wild type animals. After multiple injuries, wild type mice manifest increase clotting at the vein after thrombin exposure ( p = 0.0033), and equivalent to that of valvular knockout of FoxC2 (FoxC2del), recapitulating the phenotype seen in FoxC2 knockout animals. The combination of multiple injuries and FoxC2 knockout resulted in spontaneous microthrombi in 50% of the animals, a phenotype not observed with either multiple injuries or FoxC2 deficiency alone (χ 2 , p = 0.017). Finally, human vein samples demonstrated the protective vein valve phenotype of increased FOXC2 and PROX1 and showed decreased expression in the critically ill organ donor population by immunofluorescence imaging in organ donor samples.

CONCLUSION

We have established a novel model of posttrauma hypercoagulation that does not require direct restriction of venous flow or direct injury to the vessel endothelium to assay for hypercoagulability and can generate spontaneous microthrombosis when combined with valve-specific FOXC2 knockout. We find that multiple injuries induce a procoagulant phenotype that recapitulates the valvular hypercoagulability seen in FOXC2 knockout and, in critically ill human specimens, find evidence for loss of oscillatory shear stress-induced gene expression of FOXC2 and PROX1 in the valvular endothelium consistent with potential loss of DVT-protective valvular phenotype.

Defining the Microbiome Components (Bacteria, Viruses, Fungi) and Microbiome Geodiversity

The recognition that a resident community of microbes contributes substantially to human health and disease is one of the emerging great discoveries in modern medicine. This collection of bacteria, archaea, fungi, viruses, and eukaryotes are referred to as microbiota, which together with the individual tissues they inhabit is defined as our individual microbiome. Recent advances in modern DNA sequencing technologies permit the identification, description, and characterization of these microbial communities as well as their variations within and between individuals and groups. This complex understanding of the human microbiome is supported by a rapidly expanding field of inquiry and offers the potential to significantly impact the treatment of a wide variety of disease states. This review explores the recent findings associated with the various components of the human microbiome, and the geodiversity of microbial communities between different tissue types, individuals, and clinical conditions.

Dysbiome and Its Role in Surgically Relevant Medical Disease

Several surgically relevant conditions are directly or indirectly influenced by the human microbiome. Different microbiomes may be found within, or along, specific organs and intra-organ variation is common. Such variations include those found along the course of the gastrointestinal tract as well as those on different regions of the skin. A variety of physiologic stressors and care interventions may derange the native microbiome. A deranged microbiome is termed a dysbiome and is characterized by decreased diversity and an increase in the proportion of potentially pathogenic organisms; the elaboration of virulence factors coupled with clinical consequences defines a pathobiome. Specific conditions such as Clostridium difficile colitis, inflammatory bowel disease, obesity, and diabetes mellitus are tightly linked to a dysbiome or pathobiome. Additionally, massive transfusion after injury appears to derange the gastrointestinal microbiome as well. This review explores what is known about these surgically relevant clinical conditions to chart how non-surgical interventions may support surgical undertakings or potentially reduce the need for operation.

Dysregulation of the leukocyte signaling landscape during acute COVID-19

The global COVID-19 pandemic has claimed the lives of more than 750,000 US citizens. Dysregulation of the immune system underlies the pathogenesis of COVID-19, with inflammation mediated tissue injury to the lung in the setting of suppressed systemic immune function. To define the molecular mechanisms of immune dysfunction in COVID-19 we utilized a systems immunology approach centered on the circulating leukocyte phosphoproteome measured by mass cytometry. We find that although COVID-19 is associated with wholesale activation of a broad set of signaling pathways across myeloid and lymphoid cell populations, STAT3 phosphorylation predominated in both monocytes and T cells. STAT3 phosphorylation was tightly correlated with circulating IL-6 levels and high levels of phospho-STAT3 was associated with decreased markers of myeloid cell maturation/activation and decreased ex-vivo T cell IFN-γ production, demonstrating that during COVID-19 dysregulated cellular activation is associated with suppression of immune effector cell function. Collectively, these data reconcile the systemic inflammatory response and functional immunosuppression induced by COVID-19 and suggest STAT3 signaling may be the central pathophysiologic mechanism driving immune dysfunction in COVID-19.

Extrathoracic multiple trauma dysregulates neutrophil function and exacerbates pneumonia-induced lung injury

BACKGROUND

Forty percent of critically ill trauma patients will develop an infectious complication. Pneumonia is the most common cause of death of trauma patients surviving their initial insult. We previously demonstrated that polytrauma (PT), defined as two or more severe injuries in at least two areas of the body, induces emergency hematopoiesis characterized by accelerated myelopoiesis in the bone marrow and increased myeloid cell frequency in the peripheral tissues. We hypothesized that PT alone induces priming of neutrophils, resulting in hyperactivation upon secondary exposure to bacteria and causing acute lung injury and increased susceptibility to secondary exposure to Pseudomonas aeruginosa pneumonia.

METHODS

C57BL/6 mice were subjected to PT consisting of a lower extremity pseudofracture, liver crush injury, and 15% blood-volume hemorrhage. Pneumonia was induced by intratracheal injection of 5 × 106 CFU live P. aeruginosa or 1 × 107 of heat-killed P. aeruginosa (HKPA). For reactive oxygen species (ROS), studies polymorphonuclear neutrophils (PMNs) were isolated by immunomagnetic bead negative selection and stimulated ex-vivo with HKPA. Reactive oxygen species production was measured by immunofluorescence. For histology, lung sections were stained by hematoxylin-eosin and analyzed by a blinded grader.

RESULTS

Polytrauma induced persistent changes in immune function at baseline and to secondary infection. Pneumonia after injury resulted in increased mortality (60% vs. 5% p < 0.01). Blood neutrophils from PT mice had higher resting (unstimulated) ROS production than in naive animals (p < 0.02) demonstrating priming of the neutrophils following PT. After intratracheal HKPA injection, bronchoalveolar lavage PMNs from injured mice had higher ROS production compared with naive mice (p < 0.01), demonstrating an overexuberant immunopathologic response of neutrophils following PT.

CONCLUSION

Polytrauma primes neutrophils and causes immunopathologic PMN ROS production, increased lung injury and susceptibility to secondary bacterial pneumonia. These results suggest that trauma-induced immune dysfunction can cause immunopathologic response to secondary infection and suggests neutrophil-mediated pulmonary damage as a therapeutic target for posttrauma pneumonia.

IL-7 Immunotherapy in a Nonimmunocompromised Patient With Intractable Fungal Wound Sepsis

A nonimmunocompromised patient developed life-threatening soft tissue infection with Trichosporon asahii, Fusarium, and Saksenaea that progressed despite maximum antifungal therapies and aggressive debridement. Interleukin-7 immunotherapy resulted in clinical improvement, fungal clearance, reversal of lymphopenia, and improved T-cell function. Immunoadjuvant therapies to boost host immunity may be efficacious in life-threatening fungal infections.

Fatal COVID-19 infection in a patient with long-chain 3-hydroxyacyl-CoA dehydrogenase deficiency: A case report

Long-chain fatty-acyl CoA dehydrogenase deficiency (LCHADD) is an inborn error of long chain fatty acid oxidation with various features including hypoketotic hypoglycemia, recurrent rhabdomyolysis, pigmentary retinopathy, peripheral neuropathy, cardiomyopathy, and arrhythmias. Various stresses trigger metabolic decompensation. Coronavirus disease 2019 (COVID-19) is a pandemic caused by the RNA virus SARS-CoV-2 with diverse presentations ranging from respiratory symptoms to myocarditis. We report a case of a patient with LCHADD who initially presented with typical metabolic decompensation symptoms including nausea, vomiting, and rhabdomyolysis in addition to mild cough, and was found to have COVID-19. She developed acute respiratory failure and refractory hypotension from severe cardiomyopathy which progressed to multiple organ failure and death. Our case illustrates the need for close monitoring of cardiac function in patients with a long-chain fatty acid oxidation disorder.

Heterogeneous mass distribution of the rubble-pile asteroid (101955) Bennu

The gravity field of a small body provides insight into its internal mass distribution. We used two approaches to measure the gravity field of the rubble-pile asteroid (101955) Bennu: (i) tracking and modeling the spacecraft in orbit about the asteroid and (ii) tracking and modeling pebble-sized particles naturally ejected from Bennu's surface into sustained orbits. These approaches yield statistically consistent results up to degree and order 3, with the particle-based field being statistically significant up to degree and order 9. Comparisons with a constant-density shape model show that Bennu has a heterogeneous mass distribution. These deviations can be modeled with lower densities at Bennu's equatorial bulge and center. The lower-density equator is consistent with recent migration and redistribution of material. The lower-density center is consistent with a past period of rapid rotation, either from a previous Yarkovsky-O'Keefe-Radzievskii-Paddack cycle or arising during Bennu's accretion following the disruption of its parent body.

Hemispherical differences in the shape and topography of asteroid (101955) Bennu

We investigate the shape of near-Earth asteroid (101955) Bennu by constructing a high-resolution (20 cm) global digital terrain model from laser altimeter data. By modeling the northern and southern hemispheres separately, we find that longitudinal ridges previously identified in the north extend into the south but are obscured there by surface material. In the south, more numerous large boulders effectively retain surface materials and imply a higher average strength at depth to support them. The north has fewer large boulders and more evidence of boulder dynamics (toppling and downslope movement) and surface flow. These factors result in Bennu's southern hemisphere being rounder and smoother, whereas its northern hemisphere has higher slopes and a less regular shape. We infer an originally asymmetric distribution of large boulders followed by a partial disruption, leading to wedge formation in Bennu's history.

Multi-Disciplinary Trauma Evaluation and Management Simulation (MD-TEAMS) training for emergency medicine and general surgery residents

BACKGROUND

Successful trauma resuscitation relies on multi-disciplinary collaboration. In most academic programs, general surgery (GS) and emergency medicine (EM) residents rarely train together before functioning as a team.

METHODS

In our Multi-Disciplinary Trauma Evaluation and Management Simulation (MD-TEAMS), EM and GS residents completed manikin-based trauma scenarios and were evaluated on resuscitation and communication skills. Residents were surveyed on confidence surrounding training objectives.

RESULTS

Residents showed improved confidence running trauma scenarios in multi-disciplinary teams. Residents received lower communication scores from same-discipline vs cross-discipline faculty. EM residents scored higher in evaluation and planning domains; GS residents scored higher in action processes; groups scored equally in team management. Strong correlation existed between team leader communication and resuscitative skill completion.

CONCLUSION

MD-TEAMS demonstrated correlation between communication and resuscitation checklist item completion and communication differences by resident specialty. In the future, we plan to evaluate training-related resident behavior changes and specialty-specific communication differences by residents.

Episodes of particle ejection from the surface of the active asteroid (101955) Bennu

Active asteroids are those that show evidence of ongoing mass loss. We report repeated instances of particle ejection from the surface of (101955) Bennu, demonstrating that it is an active asteroid. The ejection events were imaged by the OSIRIS-REx (Origins, Spectral Interpretation, Resource Identification, and Security-Regolith Explorer) spacecraft. For the three largest observed events, we estimated the ejected particle velocities and sizes, event times, source regions, and energies. We also determined the trajectories and photometric properties of several gravitationally bound particles that orbited temporarily in the Bennu environment. We consider multiple hypotheses for the mechanisms that lead to particle ejection for the largest events, including rotational disruption, electrostatic lofting, ice sublimation, phyllosilicate dehydration, meteoroid impacts, thermal stress fracturing, and secondary impacts.

Temporary Abdominal Closure Is Associated with Increased Risk for Fungal Intra-Abdominal Infections in Trauma Patients

Background: Fungal infections are associated with increased morbidity and death. Few studies have examined risk factors associated with post-operative fungal intra-abdominal infections (FIAIs) in trauma patients after exploratory laparotomy. In this study, we evaluated potential risk factors for acquiring post-operative FIAIs and their impact on clinical outcomes. Methods: This was a retrospective analysis of trauma patients admitted from 2005 to 2018 who underwent exploratory laparotomy and subsequently had development of intra-abdominal infection (IAI). Demographics, comorbidities, culture data, antimicrobial usage, Injury Severity Scores (ISS), and clinical outcomes were abstracted. All post-operative IAIs were evaluated and stratified as either bacterial, fungal, combined, and with or without colonization. All groups were compared. Risk factors for the development of post-operative IAI and clinical outcomes were analyzed by Student t test and chi-square test. Multi-variable logistic regression was used to determine independent predictors of post-operative FIAIs. Results: There were 1675 patients identified as having undergone exploratory laparotomy in the setting of traumatic injury, 161 of whom were suspected of having IAI. A total of 105 (6.2%) patients had a diagnosis of IAI. Of these patients, 40 (38%) received a diagnosis of FIAI. The most common fungal pathogens were unspeciated yeast (48.3%), followed by Candida albicans (42.7%), C. glabrata (4.5%), C. dubliniensis (2.25%), and C. tropicalis (2.25%). There were no significant differences in demographics, comorbidities, and percentage of gastric perforations between FIAI and bacterial IAI (BIAI) groups. Patients with FIAIs, however, had a 75% temporary abdominal closure (TAC) rate compared with 51% in BIAIs (p = 0.01). The FIAI group had higher ISS (27 vs. 22, p = 0.03), longer hospital days (34 vs. 25, p = 0.02), and longer intensive care unit (ICU) days (17 vs. 9, p = 0.006) when compared with BIAI. The FIAI group also had a five-fold greater mortality rate. Logistic regression identified TAC as an independent risk factor for the development of post-operative FIAIs (odds ratio [OR] 6.16, confidence interval [CI] 1.14-28.0, p = 0.02). Conclusions: An FIAI after exploratory laparotomy was associated with greater morbidity and death. A TAC was associated independently with increased risk of FIAI after exploratory laparotomy in the setting of traumatic injury. Clinicians should suspect fungal infections in trauma patients in whom post-operative IAI develops after undergoing exploratory laparotomy using TAC techniques.

The dynamic geophysical environment of (101955) Bennu based on OSIRIS-REx measurements

The top-shape morphology of asteroid (101955) Bennu is commonly found among fast-spinning asteroids and binary asteroid primaries, and might have contributed significantly to binary asteroid formation. Yet a detailed geophysical analysis of this morphology for a fast-spinning asteroid has not been possible prior to the Origins, Spectral Interpretation, Resource Identification, and Security-Regolith Explorer (OSIRIS-REx) mission. Combining the measured Bennu mass and shape obtained during the Preliminary Survey phase of OSIRIS-REx, we find a significant transition in Bennu's surface slopes within its rotational Roche lobe, defined as the region where material is energetically trapped to the surface. As the intersection of the rotational Roche lobe with Bennu's surface has been most recently migrating towards its equator (given Bennu's increasing spin rate), we infer that Bennu's surface slopes have been changing across its surface within the last million years. We also find evidence for substantial density heterogeneity within this body, suggesting that its interior has a distribution of voids and boulders. The presence of such heterogeneity and Bennu's top-shape is consistent with spin-induced failure at some point in its past, although the manner of its failure cannot be determined yet. Future measurements by the OSIRIS-REx spacecraft will give additional insights and may resolve questions regarding the formation and evolution of Bennu's top-shape morphology and its link to the formation of binary asteroids.

Undertriage after severe injury among United States trauma centers and the impact on mortality

INTRODUCTION

Severely injured patients should receive definitive care at high acuity trauma centers. The purposes of this study were to determine the undertriage (UT) rate within a national sample of trauma centers and to identify characteristics of UT patients.

METHODS

Severely injured adults ≥16 years were identified from the 2010-2012 NTDB. UT was defined as those who received definitive care or died at hospitals without state or ACS level I or II verification. Risk factors for UTT and the impact of UT on mortality were determined.

RESULTS

Of 348,394 severely injured patients, 11,578 (3.3%) were UT. Older, less severely injured, and certain minority patients were most likely to be UT. After risk adjustment, predictors of UT included increased age and minority race. Increased injury severity and comorbidity were protective (all p < .05). Mortality was greater in UT patients regardless of ISS (OR = 1.32, p < .001).

CONCLUSION

The low UT rate in this study demonstrates the effectiveness of triage practices amongst ACS and state verified centers however age, race, and insurance disparities in UT should be improved.

Pseudohypoaldosteronism presenting with thrombocytosis and bilateral pneumothoraces in an infant

Pseudohypoaldosteronism type 1 (PHA-1) is a rare salt-wasting syndrome caused by a peripheral resistance to aldosterone. Here, we describe an unusual presentation of the autosomal dominant PHA-1 featuring bilateral pneumothoraces at birth, thrombocytosis in infancy, and hypercalcemia in addition to the well-described findings of hyponatremia, hyperkalemia, and failure to thrive. These findings contribute to the limited case descriptions of PHA-1 and may suggest additional diagnostic considerations in a neonate presenting with hyperkalemia, hyponatremia, and failure to thrive.

A method to produce radiation hybrids for the D-genome chromosomes of wheat (Triticum aestivum L.)

Radiation hybrid (RH) mapping is based on radiation-induced chromosome breakage rather than meiotic recombination, as a means to induce marker segregation for mapping. To date, the implementation of this mapping approach in hexaploid (Triticum aestivum L.; 2n = 6x = 42; AABBDD) and tetraploid (T. turgidum L.; 2n = 4x = 28; AABB) wheat has concentrated on the production of mapping panels for individual chromosomes. In order to extend the usefulness of this approach, we have devised a method to produce panels for the simultaneous mapping of all chromosomes of the D subgenome of hexaploid wheat. In this approach, seeds of hexaploid wheat (AABBDD) are irradiated and the surviving plants are crossed to tetraploid wheat (AABB) to produce a mapping panel based on quasi-pentaploids (AABBD). Chromosome lesions in the A and B genomes are largely masked in the quasi-pentaploids due to the presence of A- and B-genome chromosomes from the tetraploid parent. On the other hand, the chromosomes from the D-genome are present in one copy (hemizygous) and allow radiation hybrid mapping of all D-genome chromosomes simultaneously. Our analyses showed that transmission of D-genome chromosomes was apparently normal and that radiation-induced chromosome breakage along D-genome chromosomes was homogeneous. Chromosome breakage levels between D-genome chromosomes were comparable except for chromosome 6D which suffered greater chromosome breakage. These results demonstrate the feasibility of constructing D-genome radiation hybrids (DGRHs) in wheat.

The role of varicocele in male fertility

In summary, seventeen infertile men with varicocele in whom no other cause for infertility could be identified, were studied before and following varicocele repair. Morphologic alterations were the most common abnormality noted in the seminal fluid with all subjects demonstrating increased numbers of tapered or amorphous spermatozoa. Ligation of the varicocele resulted in improvement in one or more of the seminal fluid abnormalities in thirteen of the seventeen patients. Seven patients achieved a pregnancy. No single seminal fluid parameter was identified which was of predictive value in determining those subjects who would demonstrate improvement following varicocele repair.

Sonic Hedgehog signaling impairs ionizing radiation-induced checkpoint activation and induces genomic instability

The Sonic Hedgehog (Shh) pathway plays important roles in embryogenesis, stem cell maintenance, tissue repair, and tumorigenesis. Haploinsufficiency of Patched-1, a gene that encodes a repressor of the Shh pathway, dysregulates the Shh pathway and increases genomic instability and the development of spontaneous and ionizing radiation (IR)–induced tumors by an unknown mechanism. Here we show that Ptc1^+/− mice have a defect in the IR-induced activation of the ATR–Chk1 checkpoint signaling pathway. Likewise, transient expression of Gli1, a downstream target of Shh signaling, disrupts Chk1 activation in human cells by preventing the interaction of Chk1 with Claspin, a Chk1 adaptor protein that is required for Chk1 activation. These results suggest that inappropriate Shh pathway activation promotes tumorigenesis by disabling a key signaling pathway that helps maintain genomic stability and inhibits tumorigenesis.

Sirolimus for angiomyolipoma in tuberous sclerosis complex or lymphangioleiomyomatosis

BACKGROUND

Angiomyolipomas in patients with the tuberous sclerosis complex or sporadic lymphangioleiomyomatosis are associated with mutations in tuberous sclerosis genes resulting in constitutive activation of the mammalian target of rapamycin (mTOR). The drug sirolimus suppresses mTOR signaling.

METHODS

We conducted a 24-month, nonrandomized, open-label trial to determine whether sirolimus reduces the angiomyolipoma volume in patients with the tuberous sclerosis complex or sporadic lymphangioleiomyomatosis. Sirolimus was administered for the first 12 months only. Serial magnetic resonance imaging of angiomyolipomas and brain lesions, computed tomography of lung cysts, and pulmonary-function tests were performed.

RESULTS

Of the 25 patients enrolled, 20 completed the 12-month evaluation, and 18 completed the 24-month evaluation. The mean (+/-SD) angiomyolipoma volume at 12 months was 53.2+/-26.6% of the baseline value (P<0.001) and at 24 months was 85.9+/-28.5% of the baseline value (P=0.005). At 24 months, five patients had a persistent reduction in the angiomyolipoma volume of 30% or more. During the period of sirolimus therapy, among patients with lymphangioleiomyomatosis, the mean forced expiratory volume in 1 second (FEV1) increased by 118+/-330 ml (P=0.06), the forced vital capacity (FVC) increased by 390+/-570 ml (P<0.001), and the residual volume decreased by 439+/-493 ml (P=0.02), as compared with baseline values. One year after sirolimus was discontinued, the FEV1 was 62+/-411 ml above the baseline value, the FVC was 346+/-712 ml above the baseline value, and the residual volume was 333+/-570 ml below the baseline value; cerebral lesions were unchanged. Five patients had six serious adverse events while receiving sirolimus, including diarrhea, pyelonephritis, stomatitis, and respiratory infections.

CONCLUSIONS

Angiomyolipomas regressed somewhat during sirolimus therapy but tended to increase in volume after the therapy was stopped. Some patients with lymphangioleiomyomatosis had improvement in spirometric measurements and gas trapping that persisted after treatment. Suppression of mTOR signaling might constitute an ameliorative treatment in patients with the tuberous sclerosis complex or sporadic lymphangioleiomyomatosis. (ClinicalTrials.gov number, NCT00457808.)

Levetiracetam as adjunctive antiepileptic therapy for patients with tuberous sclerosis complex: a retrospective open-label trial

Seizures are a common neurologic symptom of tuberous sclerosis complex. The use of levetiracetam as adjunctive antiepileptic therapy was assessed in 20 patients with tuberous sclerosis complex aged 2 to 19 years. In this retrospective evaluation, 40% of patients treated with levetiracetam achieved a seizure reduction of more than 50%. Levetiracetam was generally well tolerated, and adverse events were relatively uncommon in patients who responded to treatment. The most commonly reported adverse events were behavioral problems. Unstable gait, insomnia, poor appetite, and increased seizure frequency were also reported. Based on these results, the use of levetiracetam as adjunctive antiepileptic therapy can reduce seizure frequency in patients with tuberous sclerosis complex. (J Child Neurol 2006;21:53-57).

Effect of highly active antiretroviral therapy and thymic transplantation on immunoreconstitution in HIV infection

The purpose of this study was to determine whether thymic transplantation in addition to highly active antiretroviral therapy (HAART) will restore T cell function in HIV infection. Eight treatment-naive HIV-infected patients with CD4+ T cell counts of 200-500/mm3 were randomized into thymic transplantation and control arms. All patients received HAART (zidovudine, lamivudine, and ritonavir) for 6 weeks prior to transplantation. Thymic transplantation was done without immunosuppression, using postnatal HLA-unmatched cultured allogeneic thymus tissue. Patients were immunized every 6 months with the neoantigen keyhole limpet hemocyanin (KLH) and the recall antigen tetanus toxoid (TT). T cell phenotype and function and T cell receptor rearrangement excision circles (TRECs) were assessed. Thymic allografts were biopsied at 2 months. Six HIV-infected patients completed the study. Four patients received cultured allogeneic postnatal thymic grafts, two others were controls. CD4+ T cell counts increased and T cell-proliferative responses to Candida antigen and TT normalized in all patients. Proliferative responses to KLH developed in three of four transplant recipients and one of two controls. Patients responding to KLH after secondary immunization had greater TREC increases compared with the patients who did not respond. All thymic allografts were rejected within 2 months. In summary, four of six patients developed T cell-proliferative responses to the neoantigen KLH over the first 2 years of HAART. The transplanted thymus tissue, however, was rejected. There was no clear difference in restoration of T cell function in the transplant recipients compared with the controls. Increases in TRECs after initiation of HAART may correlate with improved immune function.

Effect of ritonavir on lipids and post-heparin lipase activities in normal subjects

BACKGROUND

Intensive therapy of HIV infection with highly active antiretroviral therapy (HAART) dramatically reduces viral loads and improves immune status. Abnormalities of lipid levels, body fat distribution, and insulin resistance have been commonly reported after starting HAART. Whether the lipid abnormalities result from changes in metabolism after an improvement in HIV status or are partly attributable to the effects of protease inhibitor use is unknown.

METHODS

Twenty-one healthy volunteers participated in a 2 week double-blind, placebo-controlled study on the effect of the protease inhibitor ritonavir on total lipids, apolipoproteins, and post-heparin plasma lipase activities.

RESULTS

Those taking ritonavir (n = 11) had significantly higher levels of plasma triglyceride, VLDL cholesterol, IDL cholesterol, apolipoprotein B, and lipoprotein (a) compared with placebo (n = 8). HDL cholesterol was lower with therapy as a result of a reduction in HDL3 cholesterol. Post-heparin lipoprotein lipase (LpL) activity did not change but hepatic lipase activity decreased 20% (P < 0.01) in those taking ritonavir-compared with placebo. Although all lipoprotein subfractions became triglyceride enriched, most of the increase in triglyceride was in VLDL and not in IDL particles.

CONCLUSION

Treatment with ritonavir in the absence of HIV infection or changes in body composition results in hypertriglyceridemia that is apparently not mediated by impaired LpL activity or the defective removal of remnant lipoproteins, but could be caused by enhanced formation of VLDL. Long-term studies of patients with HIV infection receiving HAART will be necessary to determine the impact of these drugs and associated dyslipidemia on the risk of coronary artery disease.

Immune reconstitution in the first year of potent antiretroviral therapy and its relationship to virologic response

The effects of 1 year of zidovudine, lamivudine, and ritonavir treatment on immune reconstitution were evaluated in 34 human immunodeficiency virus (HIV)-infected individuals. After 48 weeks of therapy, 20 (59%) subjects had <100 copies HIV RNA/mL. CD4+ T cells increased from a median of 192/mm3 at baseline to 362/mm3 at week 48. Lymphocyte proliferative responses to Candida normalized within 12 weeks, but responses to HIV and tetanus remained depressed throughout therapy. Alloantigen responses increased within 12 weeks and then declined to baseline levels. Recovery of delayed-type hypersensitivity responses occurred after 12 weeks for Candida and after 48 weeks for mumps. The magnitude of virologic suppression was correlated with numeric increases in CD4+ T cells, but not with measures of functional immune reconstitution. Plasma virus suppression <100 copies/mL was not significantly correlated with increases in CD4+ T cells or functional immune reconstitution.

A simple relationship between viral load and survival time in HIV-1 infection

Despite important recent insights into the short-term dynamics of HIV-1 infection, our understanding of the long-term pathogenesis of AIDS remains unclear. Using an approach that places rapid progressors, typical progressors, and nonprogressors on a single clinical spectrum of disease progression, we quantitate the previously reported relationship between viral load and survival time. We introduce the concept of viral constant, present evidence that this quantity is conserved across patients, and explore the immunopathological implications of this finding. We conclude with a quantitative approach for assessing the benefits of a given regime of antiviral therapy.

Characterization of viral dynamics in human immunodeficiency virus type 1-infected patients treated with combination antiretroviral therapy: relationships to host factors, cellular restoration, and virologic end points

Biphasic plasma viral decays were modeled in 48 patients treated with ritonavir, zidovudine, and lamivudine. Estimated first- and second-phase decay rates were d1 as 0.47/day and d2 as 0.04/day. Interpatient differences in both decay rates were significant. The d1 was directly correlated with baseline CD4+, CD4+CD28+, and CD8+CD28+ T lymphocyte counts (P<.05) and inversely correlated with baseline virus load (P=.044) and the magnitude of CD4+ and CD8+ T lymphocyte recovery (P<.01). The d2 was directly correlated with baseline percentage of CD8+ T lymphocytes (P=.023), the CD8+CD38+ cell number (P=.024), and the level of IgG that binds to human immunodeficiency virus (HIV) type 1 gp120 (P=.02). Viral decay rates were not predictive of treatment failure or durability of viral suppression. These exploratory findings are consistent with a model in which immunologic factors contribute to elimination of HIV-infected cells and suggest a dynamic interplay between regulation of HIV expression and lymphocyte activation and recovery.

The effect of commencing combination antiretroviral therapy soon after human immunodeficiency virus type 1 infection on viral replication and antiviral immune responses

Twelve subjects were treated with zidovudine, lamivudine, and ritonavir within 90 days of onset of symptoms of acute infection to determine whether human immunodeficiency virus type 1 (HIV-1) infection could be eradicated from an infected host. In adherent subjects, with or without modifications due to intolerance, viral replication was suppressed during the 24-month treatment period. Durable suppression reduced levels of HIV-1-specific antibodies and cytotoxic T lymphocyte responses in selected subjects. Proviral DNA in mononuclear cells uniformly persisted. The persistence of HIV-1 RNA expression in lymphoid tissues and peripheral blood mononuclear cells suggests that elimination of this residual pool of virus should be achieved before considering adjustments in antiretroviral therapeutic regimens. In addition, given the reduction in levels of virus-specific immune responses, it would seem prudent to consider enhancing these responses using vaccine strategies prior to the withdrawal of antiviral therapy.

Ritonavir and saquinavir combination therapy for the treatment of HIV infection

OBJECTIVE

To evaluate the safety and antiretroviral activity of ritonavir (Norvir) and saquinavir (Invirase) combination therapy in patients with HIV infection.

DESIGN

A multicenter, randomized, open-label clinical trial.

SETTING

Seven HIV research units in the USA and Canada.

PATIENTS

A group of 141 adults with HIV infection, CD4 T lymphocyte counts of 100-500 x 10(6) cells/l, whether treated previously or not with reverse transcriptase inhibitor therapy, but without previous HIV protease inhibitor drug therapy.

INTERVENTIONS

After discontinuation of prior therapy for 2 weeks, group I patients were randomized to receive either combination (A) ritonavir 400 mg and saquinavir 400 mg twice daily or (B) ritonavir 600 mg and saquinavir 400 mg twice daily. After an initial safety assessment of group I patients, group II patients were randomized to receive either (C) ritonavir 400 mg and saquinavir 400 mg three times daily or (D) ritonavir 600 mg and saquinavir 600 mg twice daily. Investigators were allowed to add up to two reverse transcriptase inhibitors (including at least one with which the patient had not been previously treated) to a patient's regimen after week 12 for failure to achieve or maintain an HIV RNA level < or = 200 copies/ml documented on two consecutive occasions.

MEASUREMENTS

Plasma HIV RNA levels and CD4+ T-lymphocyte counts were measured at baseline, every 2 weeks for 2 months, and monthly thereafter. Safety was assessed through the reporting of adverse events, physical examinations, and the monitoring of routine laboratory tests.

RESULTS

The 48 weeks of study treatment was completed by 75% (106/141) of the patients. Over 80% of the patients on treatment at week 48 had an HIV RNA level < or = 200 copies/ml. In addition, intent-to-treat and on-treatment analyses revealed comparable results. Suppression of plasma HIV RNA levels was similar for all treatment arms (mean areas under the curve minus baseline through 48 weeks were-1.9, -2.0, -1.6, -1.8 log10 copies/ml in ritonavir-saquinavir 400-400 mg twice daily, 600-400 mg twice daily, 400-400 mg three times daily, and 600-600 mg twice daily, respectively). Median CD4 T-lymphocyte count rose by 128 x 10(6) cells/l from baseline, with an interquartile range (IQR) of 82-221 x 10(6) cells/l. The most common adverse events were diarrhea, circumoral paresthesia, asthenia, and nausea. Reversible elevation of serum transaminases (> 5 x upper limit of normal) occurred in 10% (14/141) of the patients enrolled in this study and was associated with baseline abnormalities in liver function tests, baseline hepatitis B surface antigen positivity, or hepatitis C antibody positivity (relative risk, 5.0; 95% confidence interval 1.5-16.9). Most moderate or severe elevations in liver function tests occurred in patients treated with ritonavir-saquinavir 600-600 mg twice daily.

CONCLUSIONS

Ritonavir 400 mg combined with saquinavir 400 mg twice daily with the selective addition of reverse transcriptase inhibitors was the best-tolerated regimen of four dose-ranging regimens and was equally as active as the higher dose combinations in HIV-positive patients without previous protease inhibitor treatment.

Effect of fluoxetine on pharmacokinetics of ritonavir

The potential interaction between fluoxetine, a known inhibitor of cytochrome P-450 isoform 2D6 (CYP2D6), and ritonavir, a human immunodeficiency virus type 1 protease inhibitor, was evaluated in this open-label study. Sixteen male and female subjects ranging in age from 18 to 40 years completed the study. Subjects received single doses of 600 mg of ritonavir on days 1 and 10. On study days 3 to 10, all subjects received 30 mg of fluoxetine every 12 h for a total of 16 consecutive doses. Serial blood samples for determination of ritonavir concentrations in plasma were collected after the administration of ritonavir on days 1 and 10. A limited number of blood samples for determination of fluoxetine and norfluoxetine concentrations were collected after administration of the morning dose on day 10. A statistically significant increase (19%) in the ritonavir area under the concentration-time curve (AUC) was observed with concomitant fluoxetine administration, with individual changes ranging from -12 to +56%. The change in the ritonavir AUC with concomitant fluoxetine administration was positively correlated with the norfluoxetine 24-h AUC (AUC24) (r2 = 0.42), the norfluoxetine/fluoxetine AUC24 ratio (r2 = 0.53), and the fluoxetine elimination rate constant (r2 = 0.65), with larger increases in the ritonavir AUC tending to occur with higher norfluoxetine concentrations and higher fluoxetine elimination rate constants. The effect of fluoxetine appeared to be larger in subjects with the CYP2D6 wt/wt genotype. There was little or no effect on the time to maximum drug concentration (Cmax) in serum, Cmax, and the elimination rate constant of ritonavir with concomitant fluoxetine administration. Considering the magnitude of the change observed, no ritonavir dose adjustment is recommended during concomitant fluoxetine administration.

ABT-378, a highly potent inhibitor of the human immunodeficiency virus protease

The valine at position 82 (Val 82) in the active site of the human immunodeficiency virus (HIV) protease mutates in response to therapy with the protease inhibitor ritonavir. By using the X-ray crystal structure of the complex of HIV protease and ritonavir, the potent protease inhibitor ABT-378, which has a diminished interaction with Val 82, was designed. ABT-378 potently inhibited wild-type and mutant HIV protease (Ki = 1.3 to 3.6 pM), blocked the replication of laboratory and clinical strains of HIV type 1 (50% effective concentration [EC50], 0.006 to 0.017 microM), and maintained high potency against mutant HIV selected by ritonavir in vivo (EC50, 50-fold after 8 h. In healthy human volunteers, coadministration of a single 400-mg dose of ABT-378 with 50 mg of ritonavir enhanced the area under the concentration curve of ABT-378 in plasma by 77-fold over that observed after dosing with ABT-378 alone, and mean concentrations of ABT-378 exceeded the EC50 for >24 h. These results demonstrate the potential utility of ABT-378 as a therapeutic intervention against AIDS.

Pharmacokinetic interaction between ritonavir and indinavir in healthy volunteers

The pharmacokinetic interaction between indinavir and ritonavir was evaluated in five groups of healthy adult volunteers to explore the potential for twice-daily (b.i.d.) dosing of this combination. All subjects received 800 mg of indinavir every 8 h (q8h) on day 2. In addition, subjects in group I received one dose of 800 mg of indinavir on day 1 and 800 mg of indinavir q8h on day 17. Subjects in Groups II and IV each received one dose of 600 mg of indinavir on days 1 and 17, and subjects in groups III and V each received one dose of 400 mg of indinavir on days 1 and 17. During days 3 to 17, ritonavir placebo or ritonavir at 200, 300, 300, or 400 mg q12h was given to groups I, II, III, IV, and V, respectively. Ritonavir at steady state probably inhibited the cytochrome P-450 3A metabolism of indinavir and substantially increased plasma indinavir concentrations, with the area under the plasma concentration-time curve (AUC) increasing up to 475% and the peak concentration in serum (Cmax) increasing up to 110%. The Cmax/trough concentration ratio decreased from 50 in standard q8h regimens to less than 14 when indinavir was administered with ritonavir. For a constant indinavir dose, an increase in the ritonavir dose yielded similar indinavir AUCs, Cmaxs, and concentrations at 12 h (C12s). For a constant ritonavir dose, an increase in the indinavir dose resulted in approximately proportional increases in the indinavir AUC, less than proportional increases in Cmax, and slightly more than proportional increases in C12. Ritonavir reduced between-subject variability in the indinavir AUC and trough concentrations and did not affect indinavir renal clearance. With the altered pharmacokinetic profile, indinavir likely could be given as a b.i.d. combination regimen with ritonavir. This could potentially improve patient compliance and thereby reduce treatment failures.

Human serum attenuates the activity of protease inhibitors toward wild-type and mutant human immunodeficiency virus

The potency of therapeutic regimens containing human immunodeficiency virus (HIV) protease inhibitors is related to the ability to maintain concentrations of drug in the plasma of patients that are sufficient for blocking viral replication. The estimation of concentrations required for in vivo activity using in vitro assays is complicated by the fact that extensive binding of many protease inhibitors to serum proteins attenuates their antiviral potency. To provide insight into the relative in vivo potency of current protease inhibitors, we assayed their in vitro activity against wild-type and mutant HIV in the presence of human serum (HS). Using this assay, ABT-378, a new protease inhibitor with trough levels in humans far in excess of the EC50 in the presence of 50% HS, was identified. The antiviral activity of ABT-378 was only modestly attenuated by HS, in contrast to ritonavir, saquinavir, and nelfinavir. Examination of the effect of individual serum components suggested that the activity of ABT-378 is affected predominantly by binding to alpha1-acid glycoprotein (AGP) while the activity of ritonavir is modulated by both AGP and albumin. The method described here may provide insight into the in vivo potency of protease inhibitors and be useful for the preclinical evaluation and selection of new protease inhibitors for clinical studies.

Pharmacokinetic interaction between ritonavir and clarithromycin

BACKGROUND

Because ritonavir, a human immunodeficiency virus (HIV) protease inhibitor, and clarithromycin, a macrolide antibiotic used in the treatment of disseminated infection caused by Mycobacterium avium complex, are likely to be administered concurrently for treatment of patients with HIV and acquired immunodeficiency syndrome (AIDS), the drug interaction potential of these 2 agents was evaluated. Both clarithromycin and ritonavir are metabolized to a significant extent through cytochrome P450-mediated biotransformation and are potential inhibitors of these enzymes.

OBJECTIVE

To evaluate the pharmacokinetic effects of concomitant administration of multiple doses of ritonavir and clarithromycin.

METHODS

This was an open-label, randomized, 3-period crossover study. Ritonavir alone (200 mg every 8 hours), clarithromycin alone (500 mg every 12 hours), and ritonavir and clarithromycin in combination were administered to 22 healthy volunteers. Blood samples were collected on day 4 for determination of ritonavir, clarithromycin, and its metabolite 14-(R)-hydroxyclarithromycin.

RESULTS

Ritonavir practically completely inhibited the formation of 14-(R)-hydroxyclarithromycin. The mean area under the plasma concentration-time curve (AUC) for clarithromycin increased by 77% with concomitant ritonavir, and the harmonic mean terminal half-life increased from 5 hours to 14 hours. Statistically significant increases in peak plasma concentration (31%) and minimum plasma concentration (182%) were also observed. The effect of concomitant clarithromycin administration on ritonavir pharmacokinetics was statistically significant but small, with a 12.5% increase in mean AUC and a 15.3% increase in peak plasma concentration. The terminal half-life increased from 3.47 to 3.87 hours with concomitant clarithromycin.

CONCLUSIONS

No adjustment of the ritonavir dose is necessary when administered with clarithromycin. In addition, no changes in clarithromycin dose are warranted in patients with normal renal function.

In vitro selection and characterization of human immunodeficiency virus type 1 variants with increased resistance to ABT-378, a novel protease inhibitor

ABT-378, a new human immunodeficiency virus type 1 (HIV-1) protease inhibitor which is significantly more active than ritonavir in cell culture, is currently under investigation for the treatment of AIDS. Development of viral resistance to ABT-378 in vitro was studied by serial passage of HIV-1 (pNL4-3) in MT-4 cells. Selection of viral variants with increasing concentrations of ABT-378 revealed a sequential appearance of mutations in the protease gene: I84V-L10F-M46I-T91S-V32I-I47V. Further selection at a 3.0 microM inhibitor concentration resulted in an additional change at residue 47 (V47A), as well as reversion at residue 32 back to the wild-type sequence. The 50% effective concentration of ABT-378 against passaged virus containing these additional changes was 338-fold higher than that against wild-type virus. In addition to changes in the protease gene, sequence analysis of passaged virus revealed mutations in the p1/p6 (P1' residue Leu to Phe) and p7/p1 (P2 residue Ala to Val) gag proteolytic processing sites. The p1/p6 mutation appeared in several clones derived from early passages and was present in all clones obtained from passage P11 (0.42 microM ABT-378) onward. The p7/p1 mutation appeared very late during the selection process and was strongly associated with the emergence of the additional change at residue 47 (V47A) and the reversion at residue 32 back to the wild-type sequence. Furthermore, this p7/p1 mutation was present in all clones obtained from passage P17 (3.0 microM ABT-378) onward and always occurred in conjunction with the p1/p6 mutation. Full-length molecular clones containing protease mutations observed very late during the selection process were constructed and found to be viable only in the presence of both the p7/p1 and p1/p6 cleavage-site mutations. This suggests that mutation of these gag proteolytic cleavage sites is required for the growth of highly resistant HIV-1 selected by ABT-378 and supports recent work demonstrating that mutations in the p7/p1/p6 region play an important role in conferring resistance to protease inhibitors (L. Doyon et al., J. Virol. 70:3763-3769, 1996; Y. M. Zhang et al., J. Virol. 71:6662-6670, 1997).

Effect of ritonavir on the pharmacokinetics of ethinyl oestradiol in healthy female volunteers

AIMS

To assess the effects of the protease inhibitor ritonavir on the pharmacokinetics of ethinyl oestradiol in healthy female volunteers.

METHODS

This was an open-label, single centre study in 23 subjects who received two single doses of oral contraceptive containing 50 microg ethinyl oestradiol on Day 1 (alone) and on Day 29 during concomitant ritonavir. Each subject received 16 days of every 12 h doses of ritonavir from Day 15 through Day 30. Blood samples were collected for serum ethinyl oestradiol concentrations for 48 h after each dose and for plasma ritonavir on Day 29 at 0 and 4 h postdose.

RESULTS

Statistically significant decreases in ethinyl oestradiol mean Cmax (-32%) and mean AUC (-41%), and a statistically significant increase in the mean terminal elimination rate constant (+31%) were observed during concomitant ritonavir. The harmonic mean terminal half-life decreased from 17 h to 13 h during concomitant ritonavir. No statistically significant change was noted in tmax. The ratios of means (95% confidence intervals) for Cmax and AUC were 0.682 (0.612-0.758) and 0.595 (0.506-0.694), respectively. The changes in ethinyl oestradiol pharmacokinetics were consistent with an increase in clearance from enzymatic induction of glucuronidation and/or cytochrome P450 hydroxylation. Mean steady-state ritonavir concentrations of 6.5 and 13.4 microg ml(-1) were observed at 0 and 4 h postdose, respectively.

CONCLUSIONS

Considering the extent of the decrease in ethinyl oestradiol concentrations, the use of alternate contraceptive measures should be considered when ritonavir is being administered.

Immunologic responses associated with 12 weeks of combination antiretroviral therapy consisting of zidovudine, lamivudine, and ritonavir: results of AIDS Clinical Trials Group Protocol 315

Human immunodeficiency virus (HIV)-1 infection is associated with progressive cell-mediated immune deficiency and abnormal immune activation. Although highly active antiretroviral therapy regimens can increase circulating CD4 T lymphocyte counts and decrease the risk of opportunistic complications, the effects of these treatments on immune reconstitution are not well understood. In 44 persons with moderately advanced HIV-1 infection, after 12 weeks of treatment with zidovudine, lamivudine, and ritonavir, plasma HIV-1 RNA fell a median of 2.3 logs (P < .0001). Circulating numbers of naive and memory CD4 T lymphocytes (P < .001), naive CD8 T lymphocytes (P < .004), and B lymphocytes (P < .001) increased. Improved lymphocyte proliferation to certain antigens and a tendency to improvement in delayed-type hypersensitivity also were seen. Dysregulated immune activation was partially corrected by this regimen; however, the perturbed expression of T cell receptor V regions in the CD4 and CD8 T lymphocyte populations was not significantly affected. Ongoing studies will ascertain if longer durations of virus suppression will permit more complete immune restoration.

Genotypic changes in human immunodeficiency virus type 1 associated with loss of suppression of plasma viral RNA levels in subjects treated with ritonavir (Norvir) monotherapy

Ten subjects received 600 to 1,200 mg of the human immunodeficiency virus type 1 (HIV-1) protease inhibitor ritonavir per day. Following 2 weeks of therapy, plasma HIV RNA levels decreased by a mean of 1. 57 (range, 0.89 to 1.96) log units. With continued therapy, HIV RNA levels began to rise in eight subjects. The initial rise in plasma RNA levels was temporally associated with the development and quantitative increase in the V82 resistance mutation. Doubling times of the V82A mutant virus were estimated to be 2.4 to 4.8 days. An L63P/A mutation was commonly present at baseline even in subjects with a durable virologic response. The concomitant acquisition of an L63P/A mutation with the V82A/F mutation at the time when plasma RNA levels rebounded suggests a role for the L63P/A mutation in improving the fitness of the V82A/F mutation. Subsequent additional genotypic changes at codons 54 and 84 were often associated with further increases in plasma RNA levels. Ongoing viral replication in the presence of drugs resulted in the appearance of additional genotypic changes, including the L90M saquinavir resistance mutation, and decreased phenotypic susceptibility. The relative fitness of the protease V82A ritonavir resistance mutation and reverse transcriptase T215Y/F zidovudine resistance mutation following drug withdrawal were estimated to be 96 to 98% that of the wild type. Durability of the virologic response was associated with plasma RNA levels at the nadir. A virologic response beyond 60 days was not observed unless plasma HIV RNA levels were suppressed below 2,000 copies/ml, consistent with estimates from V82A doubling times for selection of a single resistance mutation to dominate the replicating population.

Pharmacokinetic interactions between two human immunodeficiency virus protease inhibitors, ritonavir and saquinavir

OBJECTIVE

To assess the pharmacokinetic interaction between ritonavir and saquinavir.

METHODS

Ritonavir and saquinavir were administered in single doses to six groups of healthy volunteers in a two-way (saquinavir alone and ritonavir plus saquinavir for groups I through V) and a three-way (ritonavir alone, saquinavir alone, and ritonavir plus saquinavir for group VI) crossover manner with the following doses: group I, 200 mg saquinavir and 300 mg ritonavir; group II, 200 mg saquinavir and 600 mg ritonavir; group III, 400 mg saquinavir and 300 mg ritonavir; group IV, 400 mg saquinavir and 600 mg ritonavir; group V; 600 mg saquinavir and 200 mg ritonavir; group VI, 600 mg saquinavir and 600 mg ritonavir.

RESULTS

Coadministration of ritonavir markedly increased the area under the plasma concentration-time curve (AUC) and peak concentration of saquinavir (> 50-fold and 22-fold, respectively). For a constant ritonavir dose, the pharmacokinetics of saquinavir were relatively proportional to dose. For a constant saquinavir dose, the increase in saquinavir concentration tended to be less than proportional to ritonavir dose. Ritonavir reduced intersubject variability in the saquinavir AUC from 60% to 28%. The in vivo inhibition constant was 0.025 +/- 0.020 micrograms/ml with noncompartmental estimation and 0.0164 +/- 0.0004 micrograms/ml with nonlinear mixed-effects model compartmental analysis. Saquinavir showed no clinically significant effect on the pharmacokinetics of ritonavir (+6.4% in AUC). The regimens were well tolerated.

CONCLUSIONS

The large effect of ritonavir on the pharmacokinetics of saquinavir is consistent with a large reduction of saquinavir first-pass metabolism and postabsorptive clearance. Given the limited bioavailability of saquinavir given in the hard gelatin capsule formulation, this drug interaction is expected to have implications in the use of protease inhibitors in the management of human immunodeficiency virus infection.

Improvement in cell-mediated immune function during potent anti-human immunodeficiency virus therapy with ritonavir plus saquinavir

Inhibiting human immunodeficiency virus (HIV) replication with potent antiretroviral therapy may result in improved immune function, and this may lead to favorable outcomes, independent of changes in CD4+ lymphocyte count. The effect of combination protease inhibitor therapy (ritonavir plus saquinavir) on functional measures of cell-mediated immunity in 41 HIV-infected patients from one center of a multicenter trial was investigated. After 24 weeks, median plasma virus load decreased from 4.74 log10 copies/mL to below the detection limit of the assay (2.30 log10), and mean CD4+ lymphocyte count increased from 284 cells/microL to 413 cells/microL. Proliferative responses to phytohemagglutinin developed in 21 of 34 patients in whom responses were absent at baseline. Increases were observed in interleukin-2, -12, and -10 production and in the expression of CD28 on CD8+ lymphocytes. Initiation of potent anti-HIV therapy results in a degree of immune restoration, suggesting that HIV-induced immune suppression is a dynamic and potentially reversible process.

The duration of viral suppression during protease inhibitor therapy for HIV-1 infection is predicted by plasma HIV-1 RNA at the nadir

OBJECTIVE

To determine markers that are associated with the durability of virologic response to therapy with HIV protease inhibitors in HIV-infected individuals.

DESIGN

This study encompassed two retrospective analyses of the duration of virologic response to protease inhibitor therapy. The first analysis included 29 patients receiving either monotherapy or combination therapy with the protease inhibitor ritonavir whose plasma HIV RNA levels rebounded from the point of greatest decline with mutations associated with resistance to ritonavir. The second analysis included a cohort of 102 patients who initially responded to randomized treatment with either monotherapy with ritonavir or combination therapy with ritonavir and zidovudine.

METHODS

Durability of response was defined as the time from the initiation of therapy to the point at which plasma HIV RNA displayed a sustained increase of at least 0.6 log10 copies/ml from the nadir value. In the first analysis, durability of response was analyzed with respect to baseline HIV RNA, HIV RNA at the nadir, and the drop in HIV RNA from baseline to the nadir. In the second analysis, time to rebound was examined using Kaplan-Meier analysis, stratifying by either baseline HIV RNA or HIV RNA at the nadir.

RESULTS

In both analyses, the durability of response was not highly associated with either baseline RNA or the magnitude of RNA decline from baseline. Instead, a strong relationship was observed between the durability of response and the nadir plasma HIV-1 RNA value (P < 0.01). The nadir in viral load was generally reached after 12 weeks of randomized therapy.

CONCLUSIONS

Viral RNA determinations at intermediate timepoints may be prognostic of impending virologic failure of protease inhibitor therapy. Therapeutic strategies that allow intensification of initial antiretroviral regimens in the subset of patients with incomplete virological response before the emergence of high level resistance should be investigated.

Condensing enzymes from Cuphea wrightii associated with medium chain fatty acid biosynthesis

Seed oils of most Cuphea species contain > 90% medium chain (C8-C14) fatty acids. Thioesterases with specificity for these substrates are important determinants of the medium chain phenotype. The role of condensing enzymes, however, has not been investigated. cDNA clones encoding beta-ketoacyl-acyl carrier protein (ACP) synthase (KAS) were isolated from C. wrightii, a C10/C12-producing species. Deduced amino acid sequences of four unique clones were approximately 60% identical to plant KAS I sequences and approximately 75% identical to a distinct class of KAS sequences recently identified in castor and barley. A 46 kDa protein that was observed only in developing and mature seed was detected using antiserum directed against recombinant Cuphea KAS protein. The 46 kDa protein was abundant in developing seeds of six medium chain-producing Cuphea species but barely detected in one long chain-producing species. A 48 kDa protein identified immunologically as KAS I was expressed in both medium and long chain-producing Cuphea species and was detected in all tissues tested. In in vitro assays, extracts from C. wrightii and C. viscosissima developing embryos were unable to extend fatty acid chains beyond C10 following treatment with 10 microns cerulenin, a potent inhibitor of KAS I. However, a C. viscosissima mutant, cpr-1, whose seed oils are deficient in caprate relative to wild type, was impaired in extension of C8 to C10 in this assay and Western analysis revealed a specific deficiency in 46 kDa KAS in cpr-1 embryos. These results implicate cerulenin-resistant condensing activity in production of medium chain fatty acids in Cuphea.

A Cuphea beta-ketoacyl-ACP synthase shifts the synthesis of fatty acids towards shorter chains in Arabidopsis seeds expressing Cuphea FatB thioesterases

Acyl-acyl carrier protein (ACP) thioesterases with specificities on medium chain substrates (C8-C14) are requisite enzymes in plants that produce 8:0, 10:0, 12:0 and 14:0 seed oils, but they may not be the sole enzymatic determinants of chain length. The contribution to chain length regulation of a beta-ketoacyl-ACP synthase, Cw KAS A1, derived from Cuphea wrightii, a species that accumulates 30% 10:0 and 54% 12:0 in seed oils, was investigated. Expression of Cw KAS A1 in Arabidopsis seeds reduced 16:0 from 8.2 to 6.2 mol%, suggesting a KAS II-type activity. In the presence of the KAS I inhibitor cerulenin, however, transgenic seed extracts extended 6:0- and 8:0-ACP at a rate four- to fivefold greater than extracts from untransformed plants, whereas no difference was observed in extension of 14:0- and 16:0-ACP. The effect of KAS A1 on seed oils was tested by combining it with the C. wrightii medium chain-specific thioesterases, Cw FatB1 and Cw FatB2, in crosses of transformed plants. Fatty acid synthesis thesis shifted towards shorter chains in progeny expressing both classes of enzymes. KasA1/FatB1 homozygotes produced threefold more 12:0 than the FatB1 parent while 14:0 and 16:0 were reduced by one-third and one-half, respectively. F2 progeny expressing KasA1 and FatB2 produced twofold more 10:0 and 1.4-fold more 12:0 than the FatB2 parent, and the double-transgenic progeny produced one-quarter less 14:0 and one-half less 16:0 than the FatB2 parent. It is hypothesized that the shift towards production of shorter chains resulted from increased pools of medium chain acyl-ACP resulting from KAS A1 activity. The combined activities of KAS A1 and FatB thioesterases appear to determine the C. wrightii phenotype.

Biphasic kinetics of peripheral blood T cells after triple combination therapy in HIV-1 infection: a composite of redistribution and proliferation

The origin of CD4+ T cells reappearing in the blood following antiretroviral therapy in human immunodeficiency virus type-1 (HIV-1) infection is still controversial. Here we show, using mathematical modeling, that redistribution of T cells to the blood can explain the striking correlation between the initial CD4+ and CD8+ memory T-cell repopulation and the observation that 3 weeks after the start of treatment memory CD4+ T-cell numbers reach a plateau. The increase in CD4+ T cells following therapy most likely is a composite of initial redistribution, accompanied by a continuous slow repopulation with newly produced naive T cells.

Decrease of HIV-1 RNA levels in lymphoid tissue and peripheral blood during treatment with ritonavir, lamivudine and zidovudine. Ritonavir/3TC/ZDV Study Group

OBJECTIVES

Triple combination treatment of HIV-1 infection using two reverse transcriptase inhibitors and a protease inhibitor can result in significant and sustained decreases in the quantity of viral RNA in peripheral blood. Lymphoid tissue, however, constitutes the major reservoir of HIV in infected patients. Study of the viral burden in these tissues has provided additional insight in the efficacy of antiretroviral treatment.

DESIGN

Patients were randomized into two groups in order to study differences in the development of resistance to reverse transcriptase inhibitors. Group I started treatment with all three drugs simultaneously. Group II started with ritonavir monotherapy, aiming at initial reduction in virus production before the addition of lamivudine and zidovudine 3 weeks later.

METHODS

Changes in the amount of HIV in plasma and tonsillar lymphoid tissue during 24 weeks of treatment with ritonavir, lamivudine and zidovudine were studied by reverse transcriptase polymerase chain reaction.

RESULTS

Thirty-three antiretroviral-naive HIV-infected patients were included for analysis. After 24 weeks, median CD4+ cell count increased by 152 x 10(6)/l and median plasma viral RNA levels decreased by at least 2.87 log10 copies/ml. In 88% of the patients remaining on treatment, plasma RNA levels were below the quantification limit of the assay used (mean, 2.4 log10 copies/ml). The lymphoid tissue viral burden, ranging from 9.16 to 8.52 log10 copies/g at baseline, was markedly reduced with at least 2.1 log10 copies/g by week 24 in the five patients analysed. Eight patients (24%) withdrew because of side-effects. In one patient in group II, ritonavir and lamivudine resistance-associated mutations developed.

CONCLUSIONS

Treatment with this triple antiretroviral drug combination produced a durable and strong decrease of HIV-1 RNA burden in both plasma and lymphoid tissue.

Cuphea wrightii thioesterases have unexpected broad specificities on saturated fatty acids

Cuphea wrightii A. Gray is an herbaceous annual that accumulates 30% caprate (10:0) and 54% laurate (12:0) in seed storage lipids. We investigated the role of acyl-acyl carrier protein (ACP) thioesterases (TE) in acyl chain-length regulation in C. wrightii. Two embryo-derived cDNAs, encoding the TEs Cw FatB1 and Cw FatB2, were isolated. Both proteins were detected in developing embryos and mature seeds but not in other tissues, suggesting involvement in seed oil synthesis. Although expected to be 10:0/12:0-ACP-specific, these genes produced a broad range of fatty acids (12:0, 14:0, and 16:0) in transgenic Arabidopsis with the greatest accumulation at 14:0. Cw FatB2 transformants also accumulated small amounts of 10:0. Because C. wrightii accumulates only ca. 5% 14:0 and ca. 2% 16:0, we tested the possibility that gene dosage effects might significantly alter the overall kinetics of the pathway. Phenotypic comparisons of progeny segregating for the transgenes individually and in a hybrid population demonstrated that increased enzyme pools in vivo had a minor effect on diverting fatty acid production to shorter chains. We propose that Cw FatB1 and Cw FatB2 may be necessary but not sufficient determinants of the C. wrightii phenotype.

Multiple-dose pharmacokinetics of ritonavir in human immunodeficiency virus-infected subjects

The multiple-dose pharmacokinetics of ritonavir were investigated in four groups of human immunodeficiency virus-positive male subjects (with 16 subjects per group) under nonfasting conditions; a 3:1 ritonavir:placebo ratio was used. Ritonavir was given at 200 (group I), 300 (group II), 400 (group III), or 500 (group IV) mg every 12 h for 2 weeks. The multiple-dose pharmacokinetics of ritonavir were moderately dose dependent, with the clearance for group IV (6.8 +/- 2.7 liters/h) being an average of 32% lower than that for group I (10.0 +/- 3.2 liters/h). First-pass metabolism should be minimal for ritonavir. The functional half-life, estimated from peak and trough concentrations, were similar among the dosage groups, averaging 3.1 and 5.7 h after the morning and evening doses, respectively. The area under the concentration-time curve at 24 h (AUC24) and apparent terminal-phase elimination rate constant remained relatively time invariant, but predose concentrations decreased 30 to 70% over time. Concentration-dependent autoinduction is the most likely mechanism for the time-dependent pharmacokinetics. The Km and initial maximum rate of metabolism (Vmax) values estimated from population pharmacokinetic modeling (nonlinear mixed-effects models) were 3.43 microg/ml and 46.9 mg/h, respectively. The group IV Vmax increased to 68 mg/h after 2 weeks. The maximum concentration of ritonavir in serum (Cmax) and AUC after the evening doses were an average of 30 to 40% lower than the values after the morning doses, while the concentration at 12 h was an average of 32% lower than the predose concentration, probably due to protracted absorption. Less than 2% of the dose was eliminated unchanged in the urine. Triglyceride levels increased from the levels at the baseline, and the levels were correlated with baseline triglyceride levels and AUC, Cmax, or predose concentrations.

Pharmacokinetic enhancement of inhibitors of the human immunodeficiency virus protease by coadministration with ritonavir

Coadministration with the human immunodeficiency virus (HIV) protease inhibitor ritonavir was investigated as a method for enhancing the levels of other peptidomimetic HIV protease inhibitors in plasma. In rat and human liver microsomes, ritonavir potently inhibited the cytochrome P450 (CYP)-mediated metabolism of saquinavir, indinavir, nelfinavir, and VX-478. The structural features of ritonavir responsible for CYP binding and inhibition were examined. Coadministration of other protease inhibitors with ritonavir in rats and dogs produced elevated and sustained plasma drug levels 8 to 12 h after a single dose. Drug exposure in rats was elevated by 8- to 46-fold. A > 50-fold enhancement of the concentrations of saquinavir in plasma was observed in humans following a single codose of ritonavir (600 mg) and saquinavir (200 mg). These results indicate that ritonavir can favorably alter the pharmacokinetic profiles of other protease inhibitors. Combination regimens of ritonavir and other protease inhibitors may thus play a role in the treatment of HIV infection. Because of potentially substantial drug level increases, however, such combinations require further investigation to establish safe regimens for clinical use.