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PubMed2004

Primary drug-resistance in HIV-positive patients on initiation of first-line antiretroviral therapy in Germany.

BACKGROUND: Resistance against antiretroviral drugs in previously untreated HIV-infected persons is of growing relevance. The aim of the study is to determine the prevalence of resistance-associated mutations in this patient group. METHODS: In a prospective multicenter-study in Nordrhein-Westfalen, Germany, genotypic resistance testing was performed in untreated HIV-positive patients before administration of first-line highly active antiretroviral therapy (HAART). RESULTS: Between January 2001 and August 2002 resistance testing was performed in 184 therapy-naive individuals. HAART was initiated in 143 patients, who were included into the study. 70.6 % were males, mean age was 39 years, mean duration of diagnosis of HIV-infection was 1.5 years. The proportion of cases at CDC stage C was 45.4%, mean CD4-cell count was 199 /ml, mean viral load was 206,855 copies/ml. Resistance-associated mutations were detected in 20 patients (14.0%). 10.5% showed mutations indicating nucleoside reverse transcriptase inhibitor- (NRTI) resistance (M41L, E44D, D67N, T69D/N, L74V, V118I, M184V, L210W, K219Q), 2.8% showed non-nucleoside reverse transcriptase inhibitor (NNRTI) resistance (K103N, V108I, Y181C), and 2.1% showed protease-inhibitor- (PI) associated resistance (V82A, L90M), respectively. Multi-class-resistance was found in 2.1%, mutations indicating revertant variants of resistant strains were found in 4.2% (T215C/E/L/S). 86.7% of the isolates showed secondary mutations in the protease gene. No significant difference in the distribution of the parameters age, sex, duration of HIV diagnosis, CDC stage, CD4-cell count, and viral load, between groups with and without resistance was identified. CONCLUSION: The prevalence of primary resistant virus strains can be estimated at 14% in chronically infected HAART-naive HIV-patients in Germany. The majority of these cases show NRTI-associated resistance. Resistance against NNRTI or PI as well as multi-class-resistance is of low prevalence. No risk factor of predictive value can be identified for the diagnosis of resistance mutations in the individual. In conclusion, routine genotypic resistance testing in untreated HIV-positive patients should be performed before administration of first-line HAART in this region.

Adult↗

PubMed1998

The effect of putative nucleation sites on the loading and stability of iron in ferritin.

The L chain of the iron storage protein ferritin contains more putative nucleation sites in the core (Glu53, 56, 57, 60, and 63) than does the H chain (Glu61, 64, and 67). Recombinant DNA techniques were used to investigate the role of these putative nucleation sites on iron loading by ceruloplasmin and on the stability of the iron core. Recombinant rat liver ferritin H chain homopolymer and the two mutants (E61A and E61A-E64A), containing three, two and one nucleation sites, respectively, loaded up to 2010 +/- 50, 2010 +/- 40, and 1950 +/- 40 atoms of iron per ferritin, respectively. However, the mutations resulted in a 50% decrease in the rate of iron loading by ceruloplasmin. The ferritin variants incorporated the same amount of phosphate after iron loading (410 +/- 20, 400 +/- 30, and 420 +/- 20 atoms per ferritin, respectively). The stability of the iron cores prior to phosphate incorporation, assessed by the rate of iron release by 10 mM EDTA and the paraquat cation radical, corresponded to numbers of proposed nucleation sites. The subsequent incorporation of phosphate seemed to stabilize the iron core and minimized the effect of numbers of putative nucleation sites in ferritin on the rate of iron release by EDTA and the paraquat cation radical. After incorporation of phosphate the ferritins behaved similarly to the native rat liver ferritin with respect to the rate of iron release by the paraquat cation radical.

Animals↗

PubMedDate not supplied

Improved conditions for extraction and amplification of human immunodeficiency virus type 1 RNA from plasma samples with low viral load.

OBJECTIVES: We attempted to define optimal conditions for amplification of low copy number HIV-1 RNA sequences in plasma samples, applying improved conditions for nucleic acid extraction and amplification. METHODS: Several methodologic parameters were evaluated, including methods of RNA extraction, volumes of plasma samples, proportion of extracted RNA used as a template for amplification, and reverse transcriptase-DNA polymerase enzyme combination employed in cDNA synthesis and polymerase chain reaction amplification. RESULTS: With this improved assay, we were able to obtain sufficient amounts of amplified material for direct sequencing in 97% of all plasma samples in our study, including 88% of samples with viral loads <80 copies/mL, 78% of samples with viral loads <50 copies/mL, and even 2 (67%) of 3 samples with <20 copies/mL. CONCLUSIONS: This procedure could be useful for testing resistance mutations in patients undergoing highly active antiretroviral therapy, in which the viral load is commonly <400 copies/mL, and even if it is <20 RNA copies/mL.

DNA Primers↗

PubMed1998

Genotypic and phenotypic characterization of human immunodeficiency virus type 1 variants isolated from AIDS patients after prolonged adefovir dipivoxil therapy.

Adefovir dipivoxil [bis(pivaloyloxymethyl)-ester prodrug], an orally bioavailable prodrug of adefovir [9-(2-phosphonylmethoxyethyl)adenine], is currently in phase III clinical trials for the treatment of human immunodeficiency virus (HIV). In vitro experiments demonstrated that either a K65R or a K70E mutation in HIV reverse transcriptase (RT) was selected in the presence of adefovir, conferring a 16- or 9-fold decrease in susceptibility to adefovir, respectively. Previous data demonstrated that patients receiving adefovir dipivoxil monotherapy (125 mg daily) for 12 weeks experienced a median decrease in HIV RNA levels of 0.5 log10 copies/ml and that resistance to adefovir dipivoxil did not arise during that period. In the present investigation, a further study was undertaken to investigate whether RT mutations developed among viruses from patients who completed the 12-week study and who opted to enroll in a maintenance phase of prolonged (6- to 12-month) adefovir dipivoxil therapy (120 mg daily). Concomitant treatment with antiretroviral agents was permitted during the maintenance phase. The median decreases in HIV RNA levels for patients who completed 6 or 12 months of maintenance-phase dosing were 0.6 and 1.14 log10 copies/ml, respectively. The reductions in the HIV RNA levels were similar among patients who received adefovir dipivoxil with or without concomitant treatment with antiretroviral agents. Viruses from 8 of 29 patients dosed for up to 12 months developed RT mutations that were not present at baseline; these mutations may have been related to adefovir dipivoxil therapy. Viruses from two of the eight patients developed the K70E mutation while the patients were on therapy, but none of the viruses from patients developed the K65R RT substitution. Despite the development of RT mutations, sustained reductions (6 to 12 months) in viral load (> or = 0.7 log10 copies/ml decrease from baseline) were observed in all eight patients.

Acquired Immunodeficiency Syndrome↗

PubMed2004

On the rate and linearity of viability declines in Drosophila mutation-accumulation experiments: genomic mutation rates and synergistic epistasis revisited.

High rates of deleterious mutations could severely reduce the fitness of populations, even endangering their persistence; these effects would be mitigated if mutations synergize each others' effects. An experiment by Mukai in the 1960s gave evidence that in Drosophila melanogaster, viability-depressing mutations occur at the surprisingly high rate of around one per zygote and that the mutations interact synergistically. A later experiment by Ohnishi seemed to support the high mutation rate, but gave no evidence for synergistic epistasis. Both of these studies, however, were flawed by the lack of suitable controls for assessing viability declines of the mutation-accumulation (MA) lines. By comparing homozygous viability of the MA lines to simultaneously estimated heterozygous viability and using estimates of the dominance of mutations in the experiments, I estimate the viability declines relative to an appropriate control. This approach yields two unexpected conclusions. First, in Ohnishi's experiment as well as in Mukai's, MA lines showed faster-than-linear declines in viability, indicative of synergistic epistasis. Second, while Mukai's estimate of the genomic mutation rate is supported, that from Ohnishi's experiment is an order of magnitude lower. The different results of the experiments most likely resulted from differences in the starting genotypes; even within Mukai's experiment, a subset of MA lines, which I argue probably resulted from a contamination event, showed much slower viability declines than did the majority of lines. Because different genotypes may show very different mutational behavior, only studies using many founding genotypes can determine the average rate and distribution of effects of mutations relevant to natural populations.

Animals↗

PubMed2002

Plasma drug levels, genotypic resistance, and virological response to a nelfinavir plus saquinavir-containing regimen.

OBJECTIVE: To determine the importance of resistance and drug levels in the response to a dual-protease inhibitor (PI) combination. METHODS: Prospective study of 62 HIV-positive patients who switched to a salvage regimen including nelfinavir plus saquinavir. Virological response was defined as a decrease in viraemia > 0.5 log10 after 24 weeks. Optimal PI levels were defined as those above the protein binding-corrected 95% inhibitory concentration (IC95), as estimated in the presence of 50% human serum. RESULTS: Baseline median HIV load was 4.78 log10 copies/ml. The median number of mutations in the protease gene was nine (range, 2-25), predominantly at residues 82 (52%), and 90 (40%). After 24 weeks, 45% of patients had responded and 19% were < 50 copies/ml. A higher number of mutations in the protease gene (12 versus 8;P = 0.001), and the L90M mutation (36% versus 67%; P = 0.001) were associated with treatment failure. Trough levels of nelfinavir and saquinavir were two- and fivefold, respectively, greater than those reached when used as the only PI (2480 and 260 ng/ml, respectively), and they were above the estimated protein-corrected IC95 in 96% and 32% of cases. Thus, the Cmin : IC95 ratio ranged from 0.1 to 10 for nelfinavir and from 0.12 to 3.24 for saquinavir. Suboptimal PI levels were associated with a poorer response, but there was no correlation between optimal drug levels and a better response. CONCLUSION: Genotypic resistance predicts the virological response to a nelfinavir-saquinavir salvage regimen. Our data suggest that higher than optimal drug levels could be necessary to control the replication of many PI-resistant viruses.

Adult↗

PubMed1998

Functional analyses of troponin T mutations that cause hypertrophic cardiomyopathy: insights into disease pathogenesis and troponin function.

Mutations in a number of cardiac sarcomeric protein genes cause hypertrophic cardiomyopathy (HCM). Previous findings indicate that HCM-causing mutations associated with a truncated cardiac troponin T (TnT) and missense mutations in the beta-myosin heavy chain share abnormalities in common, acting as dominant negative alleles that impair contractile performance. In contrast, Lin et al. [Lin, D., Bobkova, A., Homsher, E. & Tobacman, L. S. (1996) J. Clin. Invest. 97, 2842-2848] characterized a TnT point mutation (Ile79Asn) and concluded that it might lead to hypercontractility and, thus, potentially a different mechanism for HCM pathogenesis. In this study, three HCM-causing cardiac TnT mutations (Ile79Asn, Arg92Gln, and DeltaGlu160) were studied in a myotube expression system. Functional studies of wild-type and mutant transfected myotubes revealed that all three mutants decreased the calcium sensitivity of force production and that the two missense mutations (Ile79Asn and Arg92Gln) increased the unloaded shortening velocity nearly 2-fold. The data demonstrate that TnT can alter the rate of myosin cross-bridge detachment, and thus the troponin complex plays a greater role in modulating muscle contractile performance than was recognized previously. Furthermore, these data suggest that these TnT mutations may cause disease via an increased energetic load on the heart. This would represent a second paradigm for HCM pathogenesis.

Animals↗

PubMed2004

Virological, intracellular and plasma pharmacological parameters predicting response to lopinavir/ritonavir (KALEPHAR study).

OBJECTIVES: To assess the impact of HIV-1 protease mutations and intracellular and plasma lopinavir minimum concentrations (Cmin) on virological success or failure on lopinavir/ritonavir-containing highly active antiretroviral therapy (HAART). DESIGN: HIV-1-infected HAART-experienced patients included in an observational study, received lopinavir/ritonavir (400/100 mg twice a day) plus two to three nucleoside reverse transcriptase inhibitors (NRTI) or one NRTI plus one non-NRTI. A viral load less than 50 copies/ml at month 6 defined virological success. METHODS: Intracellular and plasma lopinavir concentrations were determined by high-pressure liquid chromatography with mass-spectrometry detection. Reverse transcriptase and protease genes were sequenced at baseline and the time of virological failure. RESULTS: When the 38 patients started the lopinavir/ritonavir-based regimen, baseline median (25-75th percentile) values were: CD4 cell count 218 cells/microl (133-477); plasma HIV-1-RNA load 5.3 log10 copies/ml (3.8-5.1); number of lopinavir mutations four per protease gene (two to six). Univariate analysis associated virological success or failure at month 6 (21/38 patients) with the number of baseline lopinavir mutations, intracellular and plasma lopinavir Cmin, and the genotype inhibitory quotient (GIQ) at months 1 and 6. Multivariate analysis showed that the number of baseline lopinavir mutations and intracellular and plasma lopinavir Cmin were independently associated with virological success or failure. We defined the most discriminating intracellular and plasma lopinavir Cmin efficacy thresholds (8 and 4 microg/ml, respectively) and GIQ thresholds (1 and 3, respectively). CONCLUSION: The monitoring of lopinavir/rironavir-based HAART efficacy should include the number of baseline lopinavir/ritonavir mutations, intracellular and plasma lopinavir Cmin and GIQ calculation.

Adult↗

PubMed2003

The hepatitis B virus and common mutants.

Most biological systems have developed complex mechanisms to maintain the stability of their genetic information. Exceptions to this include viruses that can undergo rapid and substantial genetic sequence changes and alterations. The hepatitis B virus (HBV) has evolved a unique life cycle resulting in the production of enormous viral loads during active replication without actually directly killing the infected cell. Because the virus uses reverse transcription to copy its DNA genome, mutant viral genomes are frequently found. Particular selection pressures, both endogenous (host immune clearance) and exogenous (vaccines and antivirals), readily select out these escape mutants. It is still not known which particular viral mutations or combination of mutations directly affects the clinical presentation of the liver disease, the nature of the viral persistence, or the course and outcome of chronic infection. Further studies are needed to identify the pathogenic basis for the selection of these mutants. Such research should help improve the basic understanding of this unique virus-host relationship and provide new strategies for complete control of HBV infections.

DNA, Viral↗

PubMed2006

Antiviral treatment of chronic hepatitis B with lamivudine in pediatric renal transplantation.

Renal transplantation in patients with chronic hepatitis B virus (HBV) infection is known to be associated with an increased risk for exacerbation of liver dysfunction. Lamivudine has been proven to be a potent inhibitor of hepatitis B virus replication in adults after kidney transplantation. Little is known about its efficacy and safety in pediatric renal transplant recipients. Three cases serve for the discussion to demonstrate the complexity of the clinical course and effective treatment of chronic hepatitis B in pediatric patients awaiting renal transplantation. Two patients on dialysis with a high HBV replication rate were treated with lamivudine before transplantation. After the viral load had decreased below the detection limit, they underwent transplantation successfully. Despite intensified immunosuppression to treat a rejection episode in one and a relapse of the nephrotic syndrome in the other patient, the viral load remained <2.5 pg/mL. Both patients developed a mutation in the YMDD motif of the HBV genome associated with an increase in the HBV replication rate >10,000 pg/mL without deterioration of the liver function. In a third patient with a chronic HBV infection with a low replication rate, lamivudine was started about nine months after kidney transplantation due to an increasing viral load after treatment of an acute rejection episode. Six months later, the HBV DNA was no longer detectable. The patient had no signs of liver dysfunction. Lamivudine in the treatment of chronic HBV infection in pediatric renal recipients seems to be safe and effective in preventing acute liver deterioration. Three clinical cases are discussed with regard to current options in monitoring and antiviral treatment of chronic HBV in pediatric renal transplant recipients.

Adolescent↗

PubMed2002

Iron toxicity and chelation therapy.

Iron is an essential mineral for normal cellular physiology, but an excess can result in cell injury. Iron in low-molecular-weight forms may play a catalytic role in the initiation of free radical reactions. The resulting oxyradicals have the potential to damage cellular lipids, nucleic acids, proteins, and carbohydrates; the result is wide-ranging impairment in cellular function and integrity. The rate of free radical production must overwhelm the cytoprotective defenses of cells before injury occurs. There is substantial evidence that iron overload in experimental animals can result in oxidative damage to lipids in vivo, once the concentration of iron exceeds a threshold level. In the liver, this lipid peroxidation is associated with impairment of membrane-dependent functions of mitochondria and lysosomes. Iron overload impairs hepatic mitochondrial respiration primarily through a decrease in cytochrome C oxidase activity, and hepatocellular calcium homeostasis may be compromised through damage to mitochondrial and microsomal calcium sequestration. DNA has also been reported to be a target of iron-induced damage, and this may have consequences in regard to malignant transformation. Mitochondrial respiratory enzymes and plasma membrane enzymes such as sodium-potassium-adenosine triphosphatase (Na(+) + K(+)-ATPase) may be key targets of damage by non-transferrin-bound iron in cardiac myocytes. Levels of some antioxidants are decreased during iron overload, a finding suggestive of ongoing oxidative stress. Reduced cellular levels of ATP, lysosomal fragility, impaired cellular calcium homeostasis, and damage to DNA all may contribute to cellular injury in iron overload. Evidence is accumulating that free-radical production is increased in patients with iron overload. Iron-loaded patients have elevated plasma levels of thiobarbituric acid reactants and increased hepatic levels of aldehyde-protein adducts, indicating lipid peroxidation. Hepatic DNA of iron-loaded patients shows evidence of damage, including mutations of the tumor suppressor gene p53. Although phlebotomy therapy is effective in removing excess iron in hereditary hemochromatosis, chelation therapy is required in the treatment of many patients who have combined secondary and transfusional iron overload due to disorders in erythropoiesis. In patients with beta-thalassemia who undergo regular transfusions, deferoxamine treatment has been shown to be effective in preventing iron-induced tissue injury and in prolonging life expectancy. The use of the oral chelator deferiprone remains controversial, and work is continuing on the development of new orally effective iron chelators.

Cell Membrane↗

PubMed1999

No association of HIV type 1 long terminal repeat sequence pattern with long-term nonprogression and in vivo viral replication levels in European subjects.

The HIV-1 long terminal repeat (LTR) promotes and modulates proviral transcription in the infected cell. It has been suggested that truncations and even point mutations in functional sites of the LTR are associated with low viral replication and attenuated pathogenesis in HIV-1-infected long-term nonprogressors (LTNPs). We performed a detailed analysis of LTR sequences from proviral DNA of 21 Italian and Swedish, well-characterized LTNPs and of 15 progressor patients. No truncation was found and no correlation was identified between specific LTR mutations and disease progression. We also failed to find a significant correlation between phylogenetic distance and clinical status. Although HIV-1 LTR interpatient heterogeneity among LTNPs and subjects with HIV-1 RNA levels <500 copies/ml tended to be lower, no sequence mutation was correlated with in vivo viral loads. Our results suggest that HIV-1 LTR defects are rare among Italian and Swedish LTNPs.

Adolescent↗

PubMed2004

Elevated amyloid beta protein (Abeta42) and late onset Alzheimer's disease are associated with single nucleotide polymorphisms in the urokinase-type plasminogen activator gene.

Plasma amyloid beta protein (Abeta42) levels and late onset Alzheimer's disease (LOAD) have been linked to the same region on chromosome 10q. The PLAU gene within this region encodes urokinase-type plasminogen activator, which converts plasminogen to plasmin. Abeta aggregates induce PLAU expression thereby increasing plasmin, which degrades both aggregated and non-aggregated forms of Abeta. We evaluated single nucleotide polymorphisms (SNPs) in PLAU for association with Abeta42 and LOAD. PLAU SNP compound genotypes composed of haplotype pairs showed significant association with AD in three independent case-control series. PLAU SNP haplotypes associated significantly with plasma Abeta42 in 10 extended LOAD families. One of the SNPs analyzed was a missense C/T polymorphism in exon 6 of PLAU (PLAU_1=rs2227564), which causes a proline to leucine change (P141L). We analyzed PLAU_1 for association with AD in six case-control series and 24 extended LOAD families. The CT and TT PLAU_1 genotypes showed association (P=0.05) with an overall estimated odds ratio of 1.2 (1.0-1.5). The CT and TT genotypes of PLAU_1 were also associated with significant age-dependent elevation of plasma Abeta42 in 24 extended LOAD families (P=0.0006). In knockout mice lacking the PLAU gene, plasma--but not brain--Abeta42 as well as Abeta40 was significantly elevated, also in an age-dependent manner. The PLAU_1 associations were independent of the associations we found among plasma Abeta42, LOAD and variants in the IDE or VR22 region. These results provide strong evidence that PLAU or a nearby gene is involved in the development of LOAD. PLAU_1 is a plausible pathogenic mutation that could act by increasing Abeta42, but additional biological experiments are required to show this definitively.

Age Factors↗

PubMed1977

Colchester revisited: a genetic study of mental defect.

This reanalysis of a classic survey leads to inferences about design of genetic studies, resolution of heterogeneity, and the role of autosomal and sex-linked genes in mental retardation, which is no longer refractory to segregation analysis. By discriminating between sociofamilial and biological types we estimate that at least 351 autosomal loci can produce mental retardation, with an inbred load of 0.83 detrimental equivalents and a mutation rate of 0.008 per gamete, or less than 2.4 X 10(-5) per locus. The distribution of probands was estimated as: 7 per cent medical, 60 per cent sociofamilial, and 33 per cent biological. Simple genetic mechanisms account for virtually all the biological category. Within the sociofamilial group cultural inheritance and polygenes could not be resolved.

Consanguinity↗

PubMed2004

Phosphorylation of RNA polymerase II in cardiac hypertrophy: cell enlargement signals converge on cyclin T/Cdk9.

Cardiac myocyte enlargement is the eponymous characteristic of cardiac hypertrophy, regardless of the instigating signal. Such triggers include biomechanical stress (e.g., work load, compensation for ischemic damage), sarcomeric protein mutations, cytoskeletal protein mutations, abnormal energetics, G protein-coupled receptors for ligands (including angiotensin II and endothelin-1), or their signal transducers within cells. In turn, increased myocyte size reflects increased RNA and protein content per cell as responses to these stimuli. In eukaryotic cells, the large subunit of RNA polymerase II (RNAPII) becomes extensively phosphorylated in its serine-rich C-terminal domain (CTD) during the transition from transcript initiation to transcript elongation - that is, "escape" of RNAPII from the promoter-proximal region into the open reading frame. Although this process is believed to be crucial to productive synthesis of mRNA and is known to be governed by two atypical cyclin-dependent kinases, Cdk7 and Cdk9, surprisingly little is understood of how regulatory pathways within cells intersect these RNAPII-directed protein kinases. Investigations of the CTD kinase module in cardiac hypertrophy provide a tentative initial map of a molecular circuit controlling cell size through regulated phosphorylation of RNAPII.

Animals↗

PubMed2026

Cohesin promotes genomic stability by suppressing unequal sister chromatid exchange.

The protein complex cohesin plays critical roles in genomic stability by tethering together sister chromatids at their pericentric regions and along their arms from S phase until anaphase. Cohesin-mediated pericentric cohesion prevents aneuploidy by ensuring bipolar attachment of sister kinetochores. Arm cohesion prevents loss of heterozygosity by biasing DNA repair via recombination between sister chromatids rather than between homologs. Here, we investigate in yeast whether cohesin also enhances genomic stability by suppressing unequal sister chromatid exchange (USCE) between repetitive sequences. In wild-type cells, the USCE rate between repeats 4kb apart (proximal) was 15X higher than repeats 68kb apart (distal). The USCE between distal repeats but not proximal repeats increased 4 to 7-fold in mutants with altered cohesin subunits or auxiliary factors. The level of increased distal USCE corresponded with reduced arm cohesion, reduced density of cohesion arm sites, and higher sister loci mobility. Our results suggest that high density of arm cohesion sites confines repair of DNA damage to local sequences. When the density of cohesion sites decreases, sister chromatid sequences are less confined, thereby enhancing distal repeat interactions and USCE. Another set of mutations disrupted both DNA replication and cohesin loading at the replication fork during S phase. Remarkably, distal USCE in these mutants increased approximately 100-fold and was 6-fold more likely than proximal USCE. This preferential hyperdistal USCE can be explained by an aberrant sister-chromatid structure that is normally prevented by proper coupling of cohesin function and replication.

Journal Article↗

PubMed1999

Persistent HIV-1-specific CTL clonal expansion despite high viral burden post in utero HIV-1 infection.

To address the issue of clonal exhaustion in humans, we monitored HLA class I-restricted, epitope-specific CTL responses in an in utero HIV-1-infected infant from 3 mo through 5 years of age. Serial functional CTL precursor assays demonstrated persistent, vigorous, and broadly directed HIV-1 specific CTL activity with a dominant response against an epitope in HIV-1 Gag-p17 (SLYNTVATL, aa 77-85). A clonal CTL response directed against the immunodominant, HLA-A*0201-restricted epitope was found to persist over the entire observation period, as shown by TCR analysis of cDNA libraries generated from PBMC. The analysis of autologous viral sequences did not reveal any escape mutations within the targeted epitope, and viral load measurement indicated ongoing viral replication. Furthermore, inhibition of viral replication assays indicated that the epitope was properly processed from autologous viral protein. These data demonstrate that persistent exposure to high levels of viral Ag does not necessarily lead to clonal exhaustion and that epitope-specific clonal CTL responses induced within the first weeks of life can persist for years without inducing detectable viral escape variants.

Child, Preschool↗

PubMed1993

Beta A4 protein deposition in familial Alzheimer's disease with the mutation in codon 717 of the beta A4 amyloid precursor protein gene and sporadic Alzheimer's disease.

Beta A4 protein immunoreactivity in the neocortex and hippocampus of familial Alzheimer's disease (AD) including the case with the beta A4 amyloid precursor protein (APP) gene mutation in codon 717 (APP717 Val-->Ile) and sporadic cases of AD is described. A semi-automatic image analysis system was used to quantify beta A4 protein load in the isocortex of the frontal and temporal lobes and in subfields of the hippocampus. Immunoreactivity was measured in ten cases of sporadic AD and in five cases of familial AD including one in which the APP717 Val-->Ile mutation was present. Beta A4 protein load, as measured by square microns of immunoreactivity per square millimetre of cortex, was similar in the frontal and temporal isocortex in both sporadic and familial AD. There was greater variation in beta A4 protein load in subfields of the hippocampus but these differences were not significant between sporadic and familial cases. In the case with the APP717 Val-->Ile mutation. Beta A4 protein load in isocortex was greater than the mean for familial and sporadic cases of AD but less than the most severe cases of beta A4 protein deposition which were found in sporadic AD. In addition, the case with the APP717 Val-->Ile mutation has the same cytoskeletal pathology as sporadic cases of AD. The mechanism by which normal and mutant APP is processed to produce amyloidogenic fragments remains to be determined.

Aged↗