Digital Medicine System in Veterans With Severe Mental Illness: Feasibility and Acceptability Study

BACKGROUND

Suboptimal medication adherence is a significant problem for patients with serious mental illness. Measuring medication adherence through subjective and objective measures can be challenging, time-consuming, and inaccurate.

OBJECTIVE

The primary purpose of this feasibility and acceptability study was to evaluate the impact of a digital medicine system (DMS) among Veterans (patients) with serious mental illness as compared with treatment as usual (TAU) on medication adherence.

METHODS

This open-label, 2-site, provider-randomized trial assessed aripiprazole refill adherence in Veterans with schizophrenia, schizoaffective disorder, bipolar disorder, or major depressive disorder. We randomized 26 providers such that their patients either received TAU or DMS for a period of 90 days. Semistructured interviews with patients and providers were used to examine the feasibility and acceptability of using the DMS.

RESULTS

We enrolled 46 patients across 2 Veterans Health Administration sites: 21 (46%) in DMS and 25 (54%) in TAU. There was no difference in the proportion of days covered by medication refill over 3 and 6 months (0.82, SD 0.24 and 0.75, SD 0.26 in DMS vs 0.86, SD 0.19 and 0.82, SD 0.21 in TAU, respectively). The DMS arm had 0.85 (SD 0.20) proportion of days covered during the period they were engaged with the DMS (mean 144, SD 100 days). Interviews with patients (n=14) and providers (n=5) elicited themes salient to using the DMS. Patient findings described the positive impact of the DMS on medication adherence, challenges with the DMS patch connectivity and skin irritation, and challenges with the DMS app that affected overall use. Providers described an overall interest in using a DMS as an objective measure to support medication adherence in their patients. However, providers described challenges with the DMS dashboard and integrating DMS data into their workflow, which decreased the usability of the DMS for providers.

CONCLUSIONS

There was no observed difference in refill rates. Among those who engaged in the DMS arm, the proportion of days covered by refills were relatively high (mean 0.85, SD 0.20). The qualitative analyses highlighted areas for further refinement of the DMS.

TRIAL REGISTRATION

ClinicalTrials.gov NCT03881449; https://clinicaltrials.gov/ct2/show/NCT03881449.

Continuous wave interdigital H-mode cavities for alternating phase focusing heavy ion acceleration

In the future, a new superconducting (SC) continuous wave (CW) high intensity heavy ion HElmholtz LInear ACcelerator (HELIAC) should provide ion beams with maximum beam energy above the Coulomb barrier for the Super Heavy Element program at GSI (Gesellschaft für Schwerionenforschung, in Engl.: Association for Heavy Ion Research). The HELIAC consists of a SC main accelerator supplied by a normal conducting injector, which comprises an electron cyclotron resonance ion source, a radio-frequency quadrupole, and two separate interdigital H-mode drift-tube linear accelerator cavities, based on an Alternating Phase Focusing (APF) scheme. Together, both cavities will accelerate ions from 300 to 1400 keV/u with only one external quadrupole triplet for transverse focusing in between. Due to the demanding requirements of the APF concept on the voltage distribution along the beam axis on the one hand and the CW operation on the other hand, the optimization of each cavity concerning RF, mechanical, and thermal properties is crucial for the successful operation of the HELIAC injector.

Measurement of Lepton-Jet Correlation in Deep-Inelastic Scattering with the H1 Detector Using Machine Learning for Unfolding

The first measurement of lepton-jet momentum imbalance and azimuthal correlation in lepton-proton scattering at high momentum transfer is presented. These data, taken with the H1 detector at HERA, are corrected for detector effects using an unbinned machine learning algorithm (multifold), which considers eight observables simultaneously in this first application. The unfolded cross sections are compared with calculations performed within the context of collinear or transverse-momentum-dependent factorization in quantum chromodynamics as well as Monte Carlo event generators.

A dynamic collimation and alignment system for the Helmholtz linear accelerator

The upcoming commissioning of the superconducting (SC) continuous wave Helmholtz linear accelerators first of series cryomodule is going to demand precise alignment of the four internal SC cavities and two SC solenoids. For optimal results, a beam-based alignment method is used to reduce the misalignment of the whole cryomodule, as well as its individual components. A symmetric beam of low transverse emittance is required for this method, which is to be formed by a collimation system. It consists of two separate plates with milled slits, aligned in the horizontal and vertical direction. The collimation system and alignment measurements are proposed, investigated, and realized. The complete setup of this system and its integration into the existing environment at the GSI High Charge State Injector are presented, as well as the results of the recent reference measurements.

Determination of the strong coupling constant α s ( m Z ) in next-to-next-to-leading order QCD using H1 jet cross section measurements: H1 Collaboration

The strong coupling constant α s is determined from inclusive jet and dijet cross sections in neutral-current deep-inelastic ep scattering (DIS) measured at HERA by the H1 collaboration using next-to-next-to-leading order (NNLO) QCD predictions. The dependence of the NNLO predictions and of the resulting value ofα s ( m Z ) at the Z-boson mass m Z are studied as a function of the choice of the renormalisation and factorisation scales. Using inclusive jet and dijet data together, the strong coupling constant is determined to beα s ( m Z ) = 0.1157 ( 20 ) exp ( 29 ) th . Complementary,α s ( m Z ) is determined together with parton distribution functions of the proton (PDFs) from jet and inclusive DIS data measured by the H1 experiment. The valueα s ( m Z ) = 0.1142 ( 28 ) tot obtained is consistent with the determination from jet data alone. The impact of the jet data on the PDFs is studied. The running of the strong coupling is tested at different values of the renormalisation scale and the results are found to be in agreement with expectations.

Physics at the [Formula: see text] linear collider

A comprehensive review of physics at an [Formula: see text] linear collider in the energy range of [Formula: see text] GeV-3 TeV is presented in view of recent and expected LHC results, experiments from low-energy as well as astroparticle physics. The report focusses in particular on Higgs-boson, top-quark and electroweak precision physics, but also discusses several models of beyond the standard model physics such as supersymmetry, little Higgs models and extra gauge bosons. The connection to cosmology has been analysed as well.

Yield of undetected tuberculosis and human immunodeficiency virus coinfection from active case finding in urban Uganda

OBJECTIVES

To determine the yield of undetected active tuberculosis (TB), TB and human immunodeficiency virus (HIV) coinfection and the number needed to screen (NNS) to detect a case using active case finding (ACF) in an urban community in Kampala, Uganda.

METHODS

In a door-to-door survey conducted in Rubaga community from January 2008 to June 2009, residents aged ≥15 years were screened for chronic cough (≥2 weeks) and tested for TB disease using smear microscopy and/or culture. Rapid testing was used to screen for HIV infection. The NNS to detect one case was calculated based on population screened and undetected cases found.

RESULTS

Of 5102 participants, 3868 (75.8%) were females; the median age was 24 years (IQR 20-30). Of 199 (4%) with chronic cough, 160 (80.4%) submitted sputum, of whom 39 (24.4%, 95%CI 17.4-31.5) had undetected active TB and 13 (8.1%, 95%CI 6.7-22.9) were TB-HIV co-infected. The NNS to detect one TB case was 131 in the whole study population, but only five among the subgroup with chronic cough.

CONCLUSION

ACF obtained a high yield of previously undetected active TB and TB-HIV cases. The NNS in the general population was 131, but the number needed to test in persons with chronic cough was five. These findings suggest that boosting the identification of persons with chronic cough may increase the overall efficiency of TB case detection at a community level.

Dapagliflozin a glucose-regulating drug with diuretic properties in subjects with type 2 diabetes

AIMS

Sodium-glucose co-transporter 2 (SGLT2) reabsorbs glucose and sodium in the renal proximal tubule. Dapagliflozin, an SGLT2 inhibitor, targets hyperglycaemia in type 2 diabetes by increasing renal glucose excretion. To investigate whether the parallel occurring sodium loss would have diuretic-like physiologic effects, we compared dapagliflozin and hydrochlorothiazide (HCTZ) effects on 24-h blood pressure (BP), body weight, plasma volume and glomerular filtration rate (GFR).

METHODS

In this randomized, placebo-controlled, double-blind trial, 75 subjects with type 2 diabetes were assigned placebo, dapagliflozin 10 mg/day, or HCTZ 25 mg/day. Changes from baseline BP, body weight, plasma volume and GFR were assessed after 12 weeks of treatment.

RESULTS

Subjects' mean age was 56 years, type 2 diabetes mellitus (T2DM) duration 6.3 years, and haemoglobin A1c (HbA1c) 7.5%. Treatment with placebo, dapagliflozin or HCTZ resulted in changes from baseline in 24-h ambulatory mean systolic blood pressure (SBP) of -0.9 (95%CI -4.2, +2.4), -3.3 (95%CI -6.8, +0.2), and -6.6 (95%CI -9.9, -3.2) mmHg, respectively at week 12, adjusted for baseline SBP. Body weight decreased with dapagliflozin and HCTZ. In a sub-study plasma volume appeared to decrease with dapagliflozin but did not change with placebo or HCTZ treatment. Dapagliflozin induced a greater reduction in GFR (-10.8%; 95%CI -14.6, -6.7) relative to placebo (-2.9%; 95% CI -6.9, +1.2) or HCTZ (-3.4%; 95%CI -7.3, +0.6).

CONCLUSIONS

Dapagliflozin-induced SGLT2 inhibition for 12 weeks is associated with reductions in 24-h BP, body weight, GFR and possibly plasma volume. Cumulatively, these effects suggest that dapagliflozin may have a diuretic-like capacity to lower BP in addition to beneficial effects on glycaemic control.

The effect of plasma removal from apheresis platelet concentrates on platelet function

The effect of plasma removal on platelet function has scarcely been investigated. Plasma removal from apheresis platelet concentrates was achieved by centrifugation at 5000 g for 6 min or 2000 g for 10 min. After resting for 1 h, platelet concentrates were resuspended in 0·9% NaCl. Platelet function was tested before centrifugation and after resuspension by multiple electrode impedance aggregometry (MEA) and light transmission aggregometry (LTA). Plasma removal resulted in 10-14% lower response to TRAP-6 by MEA using both washing procedures, whereas TRAP-6-inducible aggregation by LTA increased slightly (2-5%). Neither plasma removal method affected collagen-induced aggregation. Thus, platelet function did not deteriorate significantly by either method.

Dapagliflozin treatment in patients with different stages of type 2 diabetes mellitus: effects on glycaemic control and body weight

AIM

Dapagliflozin is a stable, competitive, reversible, and highly selective inhibitor of sodium-glucose co-transporter 2, the major transporter responsible for renal glucose reabsorption. With an insulin-independent mechanism of action, dapagliflozin is currently being developed for the treatment of type 2 diabetes mellitus (T2DM). This work aims to compare the efficacy of dapagliflozin, as measured by the change in hemoglobin A1c concentration (A1c) and body weight, and to determine the pharmacodynamic effects of dapagliflozin, as measured by urinary glucose excretion in early-stage and late-stage T2DM patient populations.

METHODS

A total of 151 early-stage patients and 58 late-stage patients with T2DM randomly assigned 10 or 20 mg once daily (QD) dapagliflozin treatment or placebo for 12 weeks from two phase 2 studies were included in the analysis. A1c, body weight, and urinary glucose were compared between the two patient populations.

RESULTS

Compared with the early-stage population, patients in the late-stage population had a longer duration of T2DM and higher baseline levels of A1c, body weight, fasting plasma glucose, and urinary glucose excretion. After 12 weeks of dapagliflozin treatment, A1c reduction, weight loss, and increased urinary glucose excretion from baseline were observed in both populations. Baseline A1c level impacted the A1c reduction after dapagliflozin treatment with a comparable effect in patients with early and late stage disease. Late-stage patients had greater reduction in body weight. There was no statistically significant difference in the amount of urinary glucose excretion between the early-stage and late-stage patients.

CONCLUSIONS

Dapagliflozin treatment at 10 and 20 mg QD for 12 weeks resulted in significant improvement in glycaemic control and body weight reduction in both early-stage and late-stage patients with T2DM. The findings suggest that dapagliflozin could be a promising treatment option for a wide range of patients with T2DM.

Red blood units collected from bone marrow harvests after mononuclear cell selection qualify for autologous use

BACKGROUND

After large volume bone marrow (BM) harvest, donors and patients can develop severe anaemia, because collected BM can contain up to 20% of their red cell mass. In a prospective analysis, we investigated the feasibility to recover red blood cells (RBCs) from the harvested BM and investigated whether these RBC units meet the quality requirements of the European Council.

PATIENTS AND METHODS

From 19 patients (median age 51 yrs, range 31-77) with acute myocardial infarction, who participated in the MYSTAR study, a median volume of 1299 ml (range, 700-1870 ml) BM was collected. During BM processing, mononuclear cells (MNC) were separated using the Cobe Spectra apheresis system and the residual RBCs were collected in a separate bag. The quality of the collected RBCs was assessed by measuring LDH, free haemoglobin, potassium and lactate. Haemolysis was calculated and the intracellular concentration of ATP, ADP, AMP was determined by HPLC.

RESULTS

RBC units recovered from BM after MNC separation had a mean volume of 312 +/- 95 ml with a haematocrit of 47 +/- 8.9%, a haemoglobin content of 51 +/- 15 g per unit, a haemolysis of 0.15 +/- 0.005%, a pH of 6.8 +/- 0.007 and an intracellular ATP concentration of 135 pmol/10(6) RBC +/- 41, which is comparable with freshly collected packed red blood cells (PRBCs).

CONCLUSION

RBCs, collected from bone marrow harvests, can be used for autologous blood support to minimize allogeneic blood transfusions in donors and patients after large volume BM donation.

Effect of saxagliptin monotherapy in treatment-naïve patients with type 2 diabetes

OBJECTIVE

To evaluate the efficacy and safety of once-daily saxagliptin monotherapy in treatment-naïve patients with type 2 diabetes (T2D) and inadequate glycemic control.

RESEARCH DESIGN AND METHODS

This study included a main treatment cohort (MTC) with 401 patients (HbA(1c) > or = 7% and < or =10%) randomized and treated with oral saxagliptin 2.5, 5, or 10 mg once daily or placebo for 24 weeks and a separate open-label cohort (OLC) with 66 patients (HbA(1c) > 10% and < or =12%) who received saxagliptin 10 mg once daily for 24 weeks. Primary endpoint was HbA(1c) change from baseline to week 24. Secondary endpoints included change from baseline to week 24 in fasting plasma glucose (FPG), proportion of patients achieving HbA(1c) < 7%, and changes in postprandial glucose area-under-the-curve (PPG-AUC). Efficacy analyses for continuous variables were performed using an ANCOVA model with last-observation-carried-forward methodology.

RESULTS

In the MTC, saxagliptin demonstrated statistically significant decreases in adjusted mean HbA(1c) changes from baseline (mean, 7.9%) to week 24 (-0.43%, -0.46%, -0.54%) for saxagliptin 2.5, 5, and 10 mg, respectively, vs. +0.19% for placebo (all p < 0.0001). Adjusted mean FPG was significantly reduced from baseline (-15, -9, -17 mg/dL) for saxagliptin 2.5, 5, and 10 mg, respectively, vs. +6 mg/dL for placebo (p = 0.0002, p = 0.0074, p < 0.0001, respectively). More saxagliptin-treated patients achieved HbA(1c) < 7% at week 24 (35% [p = NS], 38% [p = 0.0443], 41% [p = 0.0133]) for saxagliptin 2.5, 5, and 10 mg, respectively, than placebo (24%). PPG-AUC was reduced for saxagliptin 2.5, 5, and 10 mg (-6868, -6896, -8084 mg x min/dL, respectively) vs. placebo (-647 mg x min/dL) with statistical significance demonstrated for saxagliptin 5 mg (p = 0.0002) and 10 mg (p < 0.0001). HbA(1c), FPG, and PPG-AUC reductions were also observed in the OLC at 24 weeks. In the MTC, adverse event frequency was similar across all study arms. No cases of confirmed hypoglycemia (symptoms, with fingerstick glucose < or =50 mg/dL) were observed in either cohort. Saxagliptin was not associated with weight gain. Study limitations included the lack of a control group for the OLC and the use of prespecified rescue criteria, which limited the exposure time during which patients could remain on their originally randomized medication without the introduction of additional antihyperglycemic rescue treatment.

CONCLUSIONS

Once-daily saxagliptin monotherapy for 24 weeks was generally well tolerated and demonstrated clinically meaningful reductions in key parameters of glycemic control vs. placebo.

TRIAL REGISTRATION

Clinical Trials NCT00121641

Saxagliptin added to a submaximal dose of sulphonylurea improves glycaemic control compared with uptitration of sulphonylurea in patients with type 2 diabetes: a randomised controlled trial

AIMS

Assess the efficacy and safety of saxagliptin added to a submaximal sulphonylurea dose vs. uptitration of sulphonylurea monotherapy in patients with type 2 diabetes and inadequate glycaemic control with sulphonylurea monotherapy.

METHODS AND PATIENTS

A total of 768 patients (18-77 years; HbA(1c) screening >or= 7.5 to <or= 10.0%) were randomised and treated with saxagliptin 2.5 or 5 mg in combination with glyburide 7.5 mg vs. glyburide 10 mg for 24 weeks. Blinded uptitration glyburide was allowed in the glyburide-only arm to a maximum total daily dose of 15 mg. Efficacy analyses were performed using ANCOVA and last-observation-carried-forward methodology.

RESULTS

At week 24, 92% of glyburide-only patients were uptitrated to a total glyburide dose of 15 mg/day. Saxagliptin 2.5 and 5 mg provided statistically significant adjusted mean decreases from baseline to week 24 vs. uptitrated glyburide, respectively, in HbA(1c) (-0.54%, -0.64% vs. +0.08%; both p < 0.0001) and fasting plasma glucose (-7, -10 vs. +1 mg/dl; p = 0.0218 and p = 0.002). The proportion of patients achieving an HbA(1c) < 7% was greater for saxagliptin 2.5 and 5 mg vs. uptitrated glyburide (22.4% and 22.8% vs. 9.1%; both p < 0.0001). Postprandial glucose area under the curve was reduced for saxagliptin 2.5 and 5 mg vs. uptitrated glyburide (-4296 and -5000 vs. +1196 mg.min/dl; both p < 0.0001). Adverse event occurrence was similar across all groups. Reported hypoglycaemic events were not statistically significantly different for saxagliptin 2.5 (13.3%) and 5 mg (14.6%) vs. uptitrated glyburide (10.1%).

CONCLUSION

Saxagliptin added to submaximal glyburide therapy led to statistically significant improvements vs. uptitration of glyburide alone across key glycaemic parameters and was generally well tolerated.

Dark immunofluorescence: correlation with serum immunoglobulin abnormalities

Occasional serum samples (<0.5%) tested by indirect immunofluorescence showed less fluorescence than did negative-control serum. A retrospective review of these patients' serum immunoglobulins revealed a high percentage of abnormalities (71%, versus 22% of controls). We suggest that this observation should be reported when seen and that the clinician should be alerted to an association with immunoglobulin abnormalities.

[Microsurgery of acquired degenerative lumbar spinal stenosis. Bilateral over-the-top decompression through unilateral approach]

Degenerative lumbar spinal stenosis is diagnosed with an increasing incidence. Clinical and radiological signs of progression often result in a significant decrease in the patient's quality of life. The indication for surgical treatment follows the spectrum of clinical symptoms. In cases with "structural" spinal stenosis and predominant "leg symptoms" such as neurogenic claudication and/or radicular symptoms, decompressive types of surgery are indicated. However, due to the multimorbidity of the mostly elderly patients, the surgical risk should be as low as possible whereas the surgical efficacy should be as high as possible. We describe a microsurgical technique, which can achieve a bilateral decompression of the central and lateral lumbar spinal canal through a unilateral surgical approach. In a consecutive series of 275 patients, a significant increase in standing time and walking distance could be attained. The surgical complication rate was low. A complete decompression of the spinal canal with preservation of the "tension band" of the posterior spinal column could be achieved. Although this type of surgery is adequate for patients with "predominantly leg symptoms" only, low back pain improved as well in nearly 50% of the patients. However, in cases with dynamic spinal stenosis and/or disturbed curvature with predominant low back pain, a combination of the described procedure with stabilizing surgery (spinal fusion, dynamic fixation etc.) is recommended.

Integration of visna virus DNA occurs and may be necessary for productive infection

Proviral integration is thought to be an obligate step of the retroviral replication cycle but the lentivirus visna has been reported to replicate in sheep choroid plexus (SCP) cultures in the absence of proviral integration. Because of new evidence that visna virus has a functional integrase, we reexamined visna virus infection of SCP cultures and found that proviral integration does indeed occur in this setting. While the majority of viral DNA remains unintegrated, integrated proviruses arise early in infection and accumulate over time. The sequences of the resulting host-virus DNA junctions show that, like other retroviruses, visna loses terminal nucleotides from its DNA upon integration. However, unlike other retroviruses, in over half the host-U3 junctions analyzed only a single nucleotide was lost such that the universally conserved CA dinucleotide, two nucleotides from the end of unintegrated viral DNA, did not directly abut host sequences in the provirus. We analyzed the role of integration in visna replication by introducing a series of five mutations into the integrase gene of molecularly cloned visna virus LV1-1KS1. Each mutation abolished viral replication, suggesting that integration may be an obligatory step in replication. We also documented productive infection of SCP cultures in which cell division had been blocked by g-irradiation. The ability of visna to integrate and to replicate in nondividing cells points to the possible utility of visna-based vectors for gene transfer into differentiated cells.

Neonatal respiratory distress caused by cryptic dacryoceles

Two cases of neonatal respiratory distress responded with treatment of bilateral dacryocele. In one case, no visible or palpable external evidence of dacryocele was present until mucopurulent discharge commenced more than a week after birth. While the incidence of typical congenital nasolacrimal duct obstruction is about 6%, dacryocele is 200 times less common.

Hepatic fatty acid-binding protein mRNA is regulated by growth hormone

Hepatic fatty acid-binding protein (FABP) is one of several abundant proteins which may participate in fatty acid uptake and utilization. Using differential hybridization to screen for growth hormone-responsive gene products, a complementary deoxyribonucleic acid (cDNA) was isolated which proved to be a hepatic FABP cDNA fragment. Hypophysectomy caused a 60% reduction in hepatic FABP messenger ribonucleic acid (mRNA) levels in rat liver, and growth hormone administration to hypophysectomized rats resulted in restoration of the expression of hepatic FABP mRNA. Other pituitary hormones did not alter these changes in expression. The response to growth hormone occurred within 4 hours of administration. During development, expression of hepatic FABP mRNA in rat liver was low in late fetal life, with increases to 40% of adult values by day 2 of life. Significant increases to adult levels did not occur until after day 25, when weaning is essentially completed. Alteration of hepatic FABP mRNA expression by growth hormone in rat liver may be important in the complex regulation of fatty acid uptake and metabolism.

Cytokine responses to intraventricular injection of interleukin 2 into patients with leptomeningeal carcinomatosis: rapid induction of tumor necrosis factor alpha, interleukin 1 beta, interleukin 6, gamma-interferon, and soluble interleukin 2 receptor (Mr 55,000 protein)

Interleukin 2 (IL-2) is a potent immunostimulant that causes the release of secondary cytokines and the production of lymphokine-activated killer cells. We investigated the cellular and cytokine responses to injection of recombinant human IL-2 into the human cerebrospinal fluid of 11 patients with metastatic tumors involving the spinal or cerebral leptomeninges. After initial intraventricular IL-2 administration (1.25 x 10(5) to 2 x 10(6) Cetus units/injection), cerebrospinal fluid samples were collected at intervals from 0 to 24 h. Enzyme-linked immunosorbent assay results indicated that IL-2 levels gradually decreased during the first 24 h, with an average t1/2 between 4 and 8 h. Induction of tumor necrosis factor alpha, interleukin 1 beta, interleukin 6, gamma-interferon, and interleukin 2 receptor (p55) was also assessed by enzyme-linked immunosorbent assay. Tumor necrosis factor alpha and interleukin 6 levels peaked at 2 to 4 h and 4 to 6 h, with concentrations between 71 to 1,714 pg/ml and 942 to 10,500 pg/ml, respectively. Interleukin 1 beta, gamma-interferon, and soluble IL-2 receptor peaked later, during 6 to 12 h; the levels achieved were 234 pg/ml, 25 NIH units/ml, and 207 units/ml, respectively. All cytokine concentrations returned to near baseline between 12 and 24 h; however, the soluble IL-2 receptor levels remained elevated. Additional observations included a rapid influx of neutrophilic leukocytes, followed by a prolonged presence of lymphocytes. These data indicate a broad and complex potential of the immune response in the central nervous system, as well as further define the cytokine cascade in response to IL-2 alone.

In situ amplification of visna virus DNA in tissue sections reveals a reservoir of latently infected cells

Maedi and visna are, respectively, the pulmonary and neurological manifestations of slowly progressive infections of sheep caused by retroviruses of the lentivirus subfamily. Lentivirus infections are also persistent infections in which host defenses are generally not successful in eliminating the infectious agent because of restricted viral gene expression in many infected cells. In this report, we describe a method for amplifying and detecting viral DNA in tissue sections which has made it possible to verify experimentally the postulated existence of this reservoir of latently infected cells, as well as to estimate the actual number of cells which harbor viral genomes in infected tissues. In the discussion, we present a simple mathematical model that relates this number to the rate at which inflammatory lesions develop. This model can account for both the slow progression of natural infections and for the rapid accumulation of inflammatory foci in the high dosage experimental system analysed in our studies.