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Results for “mutation load”

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PubMed2000

High viral eradication with a daily 12-week natural interferon-beta treatment regimen in chronic hepatitis C patients with low viral load. IFN-beta Research Group.

Virological sustained response (SR) is achieved in 31-49% of patients with chronic hepatitis C with combination therapy using interferon (IFN)-alpha and ribavirin for 24-48 weeks. However, as a period of 24-48 weeks is a burden for patients, we investigated the effect of daily intravenous administration of natural IFN-beta for 12 weeks in this study. In all, 112 patients were enrolled and received a daily administration of 6 MU of natural IFN-beta intravenously for 12 weeks. Serum HCV-RNA before treatment was assessed by the competitive reverse-transcription polymerase chain reaction assay. The patients were divided into two groups according to pretreatment viral load: the low viral load group (N = 25, <6.3 x 10(5) copies/ml), and the high viral load group (N = 87, > or =6.3 x 10(5) copies/ml) who were additionally administered IFN-beta thrice weekly for subsequent 14 weeks at the patients' request. Virological SR was obtained in 37% (41/112) of all the patients; 88% of those with a low viral load, and 22% of patients with a high viral load. Virological SR was attained in 21% of patients with HCV subtype 1, and in 67% of those with subtype 2a. In patients with HCV subtype 1b, virological SR was obtained in patients with the mutant-type (> or =4 amino acid mutations in the NSSA2209-48) having a low viral load (4/4), but not in those having a high viral load (0/3). The results suggest that a daily intravenous administration of natural IFN-beta for 12 weeks showed high therapeutic efficacy in patients with a low viral load despite the shorter treatment period and that the therapeutic efficacy depends on viral load rather than on the number of NS5A2209-48 amino acid mutations.

Adolescent↗

PubMed1997

Correlation between antiretroviral resistance mutations, biological parameters, and clinical evolution in zidovudine-treated patients infected with human immunodeficiency virus type 1.

To evaluate the correlation between zidovudine (ZDV) resistance mutations of human immunodeficiency virus type 1 (HIV-1), biological parameters, and clinical evolution, 111 HIV-1-infected patients treated with ZDV were studied. Specific mutations at codons 70, 215, and 41 in the HIV-1 reverse transcriptase coding region conferring resistance to ZDV were detected using a selective polymerase chain reaction. The appearance of ZDV resistance mutations was significantly correlated with baseline clinical stage, CD4+ cell count, and viral load, but not with duration of ZDV therapy or p24 antigen level. In univariate analysis, results showed a prognostic role of mutations at codons 215 and 41 for clinical progression to the acquired immune deficiency syndrome (AIDS) or death. In multivariate analysis after controlling for viral load, CD4+ cell count, and clinical stage, the presence of the mutation at codon 215 (but not at codon 41) remained an independent predictor of subsequent clinical evolution.

Adult↗

PubMed2005

[Effect of CCR5delta32, CCR5m303, CCR2-64I and SDF1-3'A gene polymorphism on the prognosis of Chinese HIV-1 carriers].

OBJECTIVE: To study how CCR5delta32, CCR5m303, CCR2-64I, SDF1-3'A gene polymorphisms affect the prognosis of Chinese HIV-1 carrier. METHODS: Epidemiologic survey was done to the HIV-1 carriers who were found in Shenzhen area. PCR/RFLP technology was applied to analyze CCR5delta32, CCR5m303, CCR2-64I, SDF1-3'A gene polymorphisms of the HIV-1 carriers. The plasma virus load and CD4+ cell counting was assayed. The incubation period of some carriers was estimated. SPSS11.0 software was used to analyze the data. RESULTS: No persons with CCR5delta32 and CCR5m303 mutation genotype were found from 189 HIV-1 carriers. SDF1-3'A allele frequency was 26.14% and CCR2-64I allele 19.82%. The carriers were divided into high virus load group (virus load < 20,000 copies/ml) and low virus load group (virus load > or =20,000 copies/ml). It was found by one-way ANOVA analysis on the logarithm of virus load that there was no significant difference between CCR2-64I wild genotype and cross bred genotype (P=0.272). One-way ANOVA analysis on delitescence of some carriers showed that there was not significant difference between CCR2-64I wild genotype and cross bred genotype (P=0.662). One-way ANOVA analysis on the logarithm of virus load showed that there was significant difference among SDF1-3'A wild genotype, cross bred genotype and pure mutation genotype (P=0.001). CONCLUSION: CCR2-64I gene mutation may not significantly affect virus load of Chinese HIV-1 carriers, nor it affect the incubation period of HIV-1 carriers. SDF1-3'A gene mutation can decrease virus load, but it may not prolong the incubation period of HIV-1 carriers.

Acquired Immunodeficiency Syndrome↗

PubMed2000

Simian immunodeficiency virus containing mutations in N-terminal tyrosine residues and in the PxxP motif in Nef replicates efficiently in rhesus macaques.

SIVmac Nef contains two N-terminal tyrosines that were proposed to be part of an SH2-ligand domain and/or a tyrosine-based endocytosis signal and a putative SH3-ligand domain (P(104)xxP(107)). In the present study, we investigated the effects of combined mutations in these tyrosine and proline residues on simian immunodeficiency virus (SIV) Nef interactions with the cellular signal transduction and endocytic machinery. We found that mutation of Y(28)F, Y(39)F, P(104)A, and P(107)A (FFAA-Nef) had little effect on Nef functions such as the association with the cellular tyrosine kinase Src, downregulation of cell surface expression of CD4 and class I major histocompatibility complex, and enhancement of virion infectivity. However, mutations in the PxxP sequence reduced the ability of Nef to stimulate viral replication in primary lymphocytes. Three macaques infected with the SIVmac239 FFAA-Nef variant showed high viral loads during the acute phase of infection. Reversions in the mutated prolines were observed between 12 and 20 weeks postinfection. Importantly, reversion of A(107)-->P, which restored the ability of Nef to coprecipitate a 62-kDa phosphoprotein in in vitro kinase assays, did not precede the development of a high viral load. The Y(28)/Y(39)-->F(28)/F(39) substitutions did not revert. In conclusion, mutations in both the tyrosine residues and the putative SH3 ligand domain apparently do not disrupt major aspects of SIV Nef function in vivo.

Animals↗

PubMed2001

Interferon responsiveness in patients infected with hepatitis C virus 1b differs depending on viral subtype.

BACKGROUND: Genotype 1b of hepatitis C virus (HCV) comprises mainly three subtypes, each named for its geographic prevalence (worldwide, W; Japan, J; and not in Japan, NJ). AIM: To characterise the newly identified subtypes of genotype 1b and to review factors associated with response to interferon (IFN) for each subtype. PATIENTS: Chronic hepatitis patients (80 men and 41 women; mean age 48.5 years, range 20.7--69.3) with HCV genotype 1b (W type, n=41; J type, n=38) or genotype 2a (n=42) were treated according to the same IFN protocol. Forty four patients (36.4%) negative for serum HCV RNA six months after cessation of treatment were considered complete responders. METHODS: Factors associated with complete response were investigated. RESULTS: Genotype 2a patients had lower viral loads (odds ratio 0.11 (95% confidence intervals (CI) 0.049--0.256)) and a better IFN response (odds ratio 0.25 (95% CI 0.117--0.552)) than genotype 1b patients whereas W type and J type patients had similar viral loads and responses to IFN. IFN response in W type patients was associated with female sex (odds ratio 0.23 (95% CI 0.055--0.983)) and low viral load (odds ratio 84.00 (95% CI 14.04--502.6)) whereas response in J type patients was related to transfusion history (odds ratio 7.20 (95% CI 1.443--35.91)), low viral load (odds ratio 117.0 (95% CI 17.82--768.3)), and genetic mutation in the interferon sensitivity determining region of the virus (odds ratio 0.08 (95% CI 0.013--0.553)). Multivariate analysis found low viral load (odds ratio 64.19 (95% CI 14.66--281.06)) to be the only significant independent factor associated with IFN response. CONCLUSIONS: Factors associated with IFN responsiveness in HCV infection differ with viral subtype.

Adult↗

PubMed2005

HBV NAT positive [corrected] blood donors in the early and late stages of HBV infection: analyses of the window period and kinetics of HBV DNA.

BACKGROUND AND OBJECTIVES: The Japanese Red Cross (JRC) carries out nucleic acid amplification testing (NAT) for hepatitis B virus (HBV), hepatitis C virus (HCV) and human immunodeficiency virus-1 (HIV-1) by using a multiplex (MPX) reagent. Screening is undertaken on serologically negative units. In this study we characterized HBV NAT-positive donations individually and analysed the window period and kinetics of HBV DNA, during acute infection, in follow-up studies. MATERIALS AND METHODS: Two hundred and seventy-seven HBV DNA-positive donations have been identified in Japan since the introduction of NAT screening of 50-donation minipools. The viral loads and genotypes of these HBV DNA-positive donations were characterized. The doubling time and half-life of HBV was estimated from the data of 123 follow-up donors. The sensitivity of the NAT system (based on 50-donation minipools) was compared with the sensitivities of the enzyme immunoassay (EIA) and the chemiluminescence immunoassay (CLIA). Samples that were CLIA negative, but with > 10(4) copies/ml of HBV DNA, were analysed by sequencing the hepatitis B surface antigen (HBsAg) region. RESULTS: Out of 277 HBV NAT-positive samples, 125 (45%) were found to have an increasing viral load and 45 (16%) a decreasing viral load. Forty per cent of HBV NAT-positive samples with an increasing viral load, and 33% of those with a decreasing viral load, were negative when tested by using the CLIA. No mutations related to escape mutants were found in the samples that were CLIA negative but with HBV DNA loads of > 10(4) copies/ml. The median HBV doubling time was 2.6 days (n = 93, 1.3-15.2 days) and the half-life was 1.6 days (n = 55, 0.9-6.3 days). Some kinetic difference was observed between genotypes A and B. CONCLUSIONS: HBV NAT screening detected HBV DNA in both early (the so-called serological window period) and late stages of acute HBV infection.

Blood Donors↗

PubMed2006

Molecular epidemiology of hepatitis B virus in Dakar, Sénégal.

Using DNA chip technology and real-time quantitative PCR, molecular profile of HBV strains infecting blood donors and patients in Dakar, Sénégal was studied. All HBsAg-positive blood donors (n = 175) and all patients who presented with chronic hepatitis B (n = 29) between 1st June 2003 and 31st July 2003 were studied. One patient, a blood donor, was coinfected by HCV, and nine patients had anti-HDV antibodies. Few persons in either group were HBeAg-positive. Viral load values were relatively low but correlated with biochemical abnormalities. Patients were infected mainly by genotype E (72%). Patients infected by genotype A (28%) tended to be younger than other patients. There was no significant difference between the blood donors and the patients with hepatitis B as regards virological markers, including viral load, when the HBV genotype was taken into account. The BCP A1762T and G1764A mutations were found in four patients and one patient, respectively; the two mutations were never found in the same patient. The W28* mutation at position 1896 of the core was detected in 19 of the 32 genotyped patients, 18 (83%) of whom had genotype E infection. ALT levels were not influenced by HBV mutations. This study shows a low frequency of clinical signs in HBsAg-positive blood donors, a relatively low level of viral replication, and a high frequency of pre-core mutants in this West African population. These results underline the importance of molecular characterization of HBV infection as specific treatments become available in this region.

Adult↗

PubMed2006

Heterosis in an isolated, effectively small, and self-fertilizing population of the flowering plant Leavenworthia alabamica.

Mildly deleterious mutations are thought to play a major role in the extinction of natural populations, especially those that are small, isolated, or inbred. Self-fertilization should reduce the effective size of populations and simultaneously reduce migration between populations. A history of self-fertilization should therefore cause a population to harbor a substantial "local drift load" caused by the fixation of mildly deleterious mutations. This hypothesis was tested in Leavenworthia alabamica, which contains large, self-incompatible populations and smaller self-compatible populations with adaptations for self-fertilization. The fitness of offspring from within- and between-population crosses was compared to quantify heterosis caused by the masking of deleterious alleles in the heterozygous state. Little heterosis was observed in crosses between five large, self-incompatible populations and two of the three small, self-fertilizing populations of L. alabamica. However, the most geographically isolated and genetically divergent self-fertilizing population (Tuscumbia) exhibited a 110.2% increase in germination and a 73.6% increase in fitness, which is consistent with a sizeable local drift load. The finding of substantial heterosis for fitness supports the idea that small effective size, reproductive isolation, and self-fertilization can make populations particularly vulnerable to mutation accumulation.

Biological Evolution↗

PubMed2000

Human immunodeficiency virus type 1 mutations selected in patients failing efavirenz combination therapy.

Efavirenz is a potent and selective nonnucleoside inhibitor of human immunodeficiency virus type 1 (HIV-1) reverse transcriptase (RT). Nucleotide sequence analyses of the protease and RT genes (coding region for amino acids 1 to 229) of multiple cloned HIV-1 genomes from virus found in the plasma of patients in phase II clinical studies of efavirenz combination therapy were undertaken in order to identify the spectrum of mutations in plasma-borne HIV-1 associated with virological treatment failure. A K103N substitution was the HIV-1 RT gene mutation most frequently observed among plasma samples from patients for whom combination therapy including efavirenz failed, occurring in at least 90% of cases of efavirenz-indinavir or efavirenz-zidovudine (ZDV)-lamivudine (3TC) treatment failure. V108I and P225H mutations were observed frequently, predominantly in viral genomes that also contained other nonnucleoside RT inhibitor (NNRTI) resistance mutations. L100I, K101E, K101Q, Y188H, Y188L, G190S, G190A, and G190E mutations were also observed. V106A, Y181C, and Y188C mutations, which have been associated with high levels of resistance to other NNRTIs, were rare in the patient samples in this study, both before and after exposure to efavirenz. The spectrum of mutations observed in cases of virological treatment failure was similar for patients initially dosed with efavirenz at 200, 400, or 600 mg once a day and for patients treated with efavirenz in combination with indinavir, stavudine, or ZDV-3TC. The proportion of patients carrying NNRTI resistance mutations, usually K103N, increased dramatically at the time of initial viral load rebound in cases of treatment failure after exposure to efavirenz. Viruses with multiple, linked NNRTI mutations, especially K103N-V108I and K103N-P225H double mutants, accumulated more slowly following the emergence of K103N mutant viruses.

Alkynes↗

PubMed2004

Development of anti-retroviral resistance of HIV-1 infected individuals on therapy: is it inevitable?

Highly active antiretroviral therapy directed against HIV-1 has dramatically modified morbidity and mortality in infected individuals. Enthusiasm for the success of these medications have been tempered by an inability to clear virus from the infected host leaving a virus poised to leverage any advantage into one of productive survival. One mechanism used to accomplish escape from suppression secondary to antiretroviral therapy is by developing mutations. The goal of therapy has been to diminish viral replication, thereby effectively abrogating the development of these resistance-bearing mutations. This strategy has met with significant success but numerous host-viral factors impact on the ability of the clinician to persistently suppress viral load, thereby providing a window of opportunity for the virus to mutate. In particular we review evidence for ongoing viral replication in the face of suppressive antiretroviral therapy and viral replication in tissue compartments. We discuss whether viral resistance can develop during transient elevations in viral load (viral blips) or as a function of the rate of viral load decay while on therapy. Finally, we touch on the therapeutic strategy that diminished viral replication capacity of mutational species can maintain host immunity.

Anti-HIV Agents↗

PubMed2005

Suppression of virus load by highly active antiretroviral therapy in rhesus macaques infected with a recombinant simian immunodeficiency virus containing reverse transcriptase from human immunodeficiency virus type 1.

We have modeled highly active antiretroviral therapy (HAART) for AIDS in rhesus macaques infected with a chimera (RT-SHIV) of simian immunodeficiency virus containing reverse transcriptase from human immunodeficiency virus type-1 (HIV-1). Seven RT-SHIV-infected macaques were treated with a combination of efavirenz (200 mg orally once daily), lamivudine (8 mg/kg subcutaneously once daily), and tenofovir (30 mg/kg subcutaneously once daily). Plasma viral RNA levels in all animals were reduced by more than 1,000-fold after 4 weeks and, in six of the seven animals, were reduced to undetectable levels after 10 weeks. Virus loads increased slightly between 12 and 16 weeks of treatment, associated with problems with the administration of efavirenz. After a change in the method of efavirenz administration, virus loads declined again and remained undetectable in the majority of animals for the duration of therapy. Treatment was stopped for three animals after 36 weeks of therapy, and virus loads increased rapidly. Posttreatment RT-SHIV isolates had no mutations associated with resistance to any of the three drugs. Efavirenz treatment was stopped, but lamivudine and tenofovir treatment for two other macaques was continued. The virus load in one of these two animals rebounded; virus from this animal was initially free of drug-resistance mutations but acquired the K65R mutation in reverse transcriptase at 11 weeks after efavirenz treatment was withdrawn. These results mimic HAART of HIV-1-infected humans. The RT-SHIV/rhesus macaque model should be useful for studies of tissue reservoirs and sites of residual replication that are not possible or practical with humans.

Animals↗

PubMed2002

Intrapatient diversity and its correlation with viral setpoint in human immunodeficiency virus type 1 CRF02_A/G-IbNG infection.

The human immunodeficiency virus type 1 (HIV-1) viral setpoint during the disease-free interval has been strongly associated with future risk of disease progression. An awareness of the correlation between viral setpoint and HIV-1 genetic evolution over time is important in the understanding of viral dynamics and infection. We examined genetic diversity in HIV-1 CRF02_A/G-IbNG-infected seroincident women in Dakar, Senegal; determined whether a viral setpoint kinetic pattern existed for CRF02_A/G-IbNG during the disease-free interval; and correlated viral load level and diversity. Samples were drawn during the disease-free interval from consenting CRF02_A/G-IbNG-infected, antiretroviral therapy-naïve female commercial sex workers in Dakar, Senegal. Based on sequential plasma RNA values, low and high viral setpoint groups were established. Intrapatient diversity and divergence over time was determined from earlier and later time point DNA samples from each person. Most individuals followed the viral setpoint paradigm. For each 1/-/log(10) copy/ml of plasma increase in viral load, intrapatient diversity increased by 1.4% (P = 0.028). A greater diversification rate was observed in the high viral setpoint group than in the low viral setpoint group (P = 0.01). Greater nucleotide (P = 0.015) and amino acid (P = 0.048) divergences and a greater nucleotide divergence rate (P = 0.03) were found in the high viral setpoint group. There was no difference between the groups in the ratio of the number of nonsynonymous substitutions per nonsynonymous site to the number of synonymous substitutions per synonymous site. The greater intrapatient diversity, divergence, and diversification rates observed in the high viral setpoint group supports the notion that diversity is driven by cycles of viral replication resulting in accumulated mutations. Recognizing diversity potential based on viral load levels in individuals may inform the design of vaccines and therapies.

Base Sequence↗

PubMed2006

Dynamics of proviral HIV-1 184M/V in circulating CD4+ T-cells: a 90 days follow-up study after initiation/switch of HAART.

HIV-1 viral load falls rapidly on initiation of HAART. This phase of decreasing yet substantial viral production in the presence of antiretroviral drugs could generate resistant HIV-1. Whether switching a drug from a failing regime changes the demography of the mutations associated with it in the CD4+ T-cell compartment is not well-defined. We investigated the presence/absence and quantity of 184M and 184V in the CD4+ T-cell compartment of naïve patients initiated to HAART (group I), and patients who shifted to a non-lamivudine therapy (group II). We initiated a prospective 90 d follow-up study of 11 patients to detect and quantity proviral HIV-1 184M and 184V in the CD4+ T-cell compartment with a sensitive real time PCR assay. Results showed that the 184V was not detected in the CD4+ T-cell compartment of any of the 7 naïve patients who started on HAART. Three out of the 4 patients in group II experienced a fall in the percentage of 184V, with reduction to below detection limits in 2 patients. It can be concluded that initiation of HAART does not allow the archiving of the lamivudine associated mutation, 184V, in the CD4+ T-cell compartment. Reduction in the quantity of 184V when therapy is switched to an effective non-lamivudine regime indicates that the mutation in this compartment is dynamic.

Anti-HIV Agents↗

PubMed2004

A dnaC mutation in Escherichia coli that affects copy number of ColE1-like plasmids and the PriA-PriB (but not Rep-PriC) pathway of chromosomal replication restart.

Escherichia coli nusG and rho mutants, which are defective in transcription termination, are killed following transformation with several ColE1-like plasmids that lack the plasmid-encoded copy-number regulator gene rom because of uncontrolled plasmid replication within the cells. In this study, a mutation [dnaC1331(A84T)] in the dnaC gene encoding the replicative helicase-loading protein was characterized as a suppressor of this plasmid-mediated lethality phenotype. The mutation also reduced the copy number of the plasmids in otherwise wild-type strains. In comparison with the isogenic dnaC(+) strain, the dnaC mutant was largely unaffected for (i) growth on rich or minimal medium, (ii) tolerance to UV irradiation, or (iii) survival in the absence of the PriA, RecA, or RecB proteins. However, it was moderately SOS-induced and was absolutely dependent on both the Rep helicase and the PriC protein for its viability. A dnaC1331(A84T) dam mutant, but not its mutH derivative, exhibited sensitivity to growth on rich medium, suggestive of a reduced capacity in the dnaC1331(A84T) strains to survive chromosomal double-strand breaks. We propose that DnaC-A84T is proficient in the assembly of replication forks for both initiation of chromosome replication (at oriC) and replication restart via the Rep-PriC pathway, but that it is specifically defective for replication restart via the PriA-PriB pathway (and consequently also for replication of the Rom(-) ColE1-like plasmids).

Bacterial Proteins↗

PubMed1997

Expression of mutated glucocerebrosidase alleles in human cells.

Gaucher disease is a heterogeneous disease characterized by impaired activity of the lysosomal enzyme glucocerebrosidase. This heterogeneity is attributed to a large number of mutations in the corresponding gene. In order to test the biochemical properties of some mutations prevalent among Israeli populations, the normal human glucocerebrosidase cDNA and cDNAs carrying mutations N370S, L444P, D409H, recTL, recNcil, P415R and 84GG were coupled to the T7 RNA polymerase promoter in a vaccinia virus-derived expression vector (pTM-1). Recombinant viruses were produced and used to infect human tissue culture cells. RNA and protein stability, recognition by anti-glucocerebrosidase monoclonal antibodies and intracellular enzymatic activity were measured. The results demonstrated that the D409H allele directed synthesis of cytoplasmic RNA with decreased stability compared with its normal counterpart or other mutated forms. The D409H and L444P mutated proteins had lower stability than that of their normal counterpart, while the recNcil-mutated protein was more stable. Only glucocerebrosidase forms harboring leucine at position 444 were recognized by the anti-glucocerebrosidase monoclonal antibodies used (8E4 and 2C7). Measurements of enzymatic activity of the recombinant proteins in cells loaded with a fluorescent glucosylceramide demonstrated that the N370S mutated enzyme had activity similar to that of the normal enzyme. The other mutated enzymes exhibited varying degrees of activities, generally corresponding to the phenotypes with which they are associated. The results presented demonstrate the use of the vaccinia virus-derived expression system and of loading living cells with fluorescent substrate as efficient tools for studying mutants in Gaucher disease and in other lysosomal diseases.

Alleles↗

PubMed2005

Mutations at codons 54 and 82 of HIV protease predict virological response of HIV-infected children on salvage lopinavir/ritonavir therapy.

BACKGROUND: Lopinavir/ritonavir is a protease inhibitor (PI) that has shown great effectiveness as salvage therapy in PI-experienced HIV-infected children. OBJECTIVES: To study whether mutations in the HIV-1 protease gene can reliably predict virological responses to salvage therapy with lopinavir/ritonavir in HIV-infected children. PATIENTS AND METHODS: We carried out a prospective study in 56 HIV-infected children. PI-associated resistance mutations were determined by genotypic testing and were scored according to the IAS-USA guidelines 2005. RESULTS: Children with a 'lopinavir mutation score' (LMS) > or = 6 had a negative association for achieving viral load (VL) control [undetectable viral load (uVL) < or = 400 copies/mL] and maintaining uVL for at least 6 months. Moreover, children with protease-associated mutations (PRAMs) > or = 2 had a negative association for achieving VL control but not for maintaining uVL for at least 6 months. The relative proportion (RP) to uVL was 0.32 (CI95%: 0.16; 0.33; P = 0.002) in children with I54V (46% of total) and 0.48 (CI95%: 0.24; 0.97; P = 0.041) in children with V82A/F (52% of total). Children with I54V and V82A/F had higher prevalence of lopinavir-associated resistance mutations and showed RP of 0.36 (CI95%: 0.17; 0.76; P = 0.007) for achieving uVL. CONCLUSIONS: LMS and PRAMs in HIV-infected children were associated with virological failure in pre-treated HIV-infected children on salvage therapy with lopinavir/ritonavir. Moreover, I54V and V82A/F led to the poorest virological response.

Adolescent↗

PubMedDate not supplied

Tetrahydrobiopterin responsiveness: results of the BH4 loading test in 31 Spanish PKU patients and correlation with their genotype.

Tetrahydrobiopterin (BH4) responsiveness in patients with mutations in the phenylalanine hydroxylase (PAH) gene is a recently recognized subtype of hyperphenylalaninemia characterized by a positive BH4 loading test. According to recent estimates, this phenotype may be quite common, suggesting that a large group of individuals may benefit from BH4 substitution, eliminating the need of life-long dietary restrictions. This underscores the importance of identifying BH4-responsive patients in each population, establishing the association with specific PAH mutations. In this work, we describe the results of a pilot study performed with 31 Spanish PAH-deficient patients subjected to a BH4 loading test. Overall, 11/31 (37%) showed a positive response with a 30% decrease in blood Phe levels 8 h after the BH4 challenge, and three additional patients, considered slow responders, showed this decrease only after 12-16 h. We report for the first time a patient homozygous for a splicing mutation with a slow response, suggesting an effect of BH4 supplementation on PAH gene expression. Most of the responsive patients belong to the mild hyperphenylalaninemia (MHP) or mild phenylketonuria phenotypic groups. In MHP patients we report for the first time the results of parallel single Phe doses confirming the utility of these analyses for a better evaluation of the response. Genotype analysis confirms the involvement in the response of specific mutations (D415N, S87R, R176L, E390G, and A309V) present in hemizygous patients, and provide relevant information for the discussion of the potential mechanisms underlying BH4 responsiveness.

Adolescent↗

PubMed2004

Iron trafficking in the mitochondrion: novel pathways revealed by disease.

It is well known that iron (Fe) is transported to the mitochondrion for heme synthesis. However, only recently has the importance of this organelle for many other facets of Fe metabolism become widely appreciated. Indeed, this was stimulated by the description of human disease states that implicate mitochondrial Fe metabolism. In particular, studies assessing various diseases leading to mitochondrial Fe loading have produced intriguing findings. For instance, the disease X-linked sideroblastic anemia with ataxia (XLSA/A) is due to a mutation in the ATP-binding cassette protein B7 (ABCB7) transporter that is thought to transfer [Fe-S] clusters from the mitochondrion to the cytoplasm. This and numerous other findings suggest the mitochondrion is a dynamo of Fe metabolism, being vital not only for heme synthesis but also for playing a critical role in the genesis of [Fe-S] clusters. Studies examining the disease Friedreich ataxia have suggested that a mutation in the gene encoding frataxin leads to mitochondrial Fe loading. Apart from these findings, the recently discovered mitochondrial ferritin that may store Fe in ring sideroblasts could also regulate the level of Fe needed for heme and [Fe-S] cluster synthesis. In this review, we suggest a model of mitochondrial Fe processing that may account for the pathology observed in these disease states.

Animals↗