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PubMed2006

Genotype, phylogenetic analysis, and transmission pattern of occult hepatitis B virus (HBV) infection in families of asymptomatic HBsAg carriers.

Occult hepatitis B is defined by the presence of hepatitis B virus (HBV) DNA in the serum in absence of hepatitis B surface antigen (HBsAg). Studies were conducted to screen for occult HBV infection among family members of HBV carriers, incidentally detected positive for HBV infection with a view to assess the pattern of virus transmission among them. Nested PCR assay, employing independent sets of primers to surface and core genes, was used for detection of HBV DNA in serum samples from 28 index cases with asymptomatic HBV infection, and in serum samples from 72 HBsAg negative/anti-HBc positive family members. HBV DNA was detected in 15 HBsAg negative family members of 10 HBsAg positive index patients and was studied in detail. Direct sequencing of S gene region of 25 isolates (10 index cases and 15 contacts) and phylogenetic analysis with data base sequences revealed that genotypes A, C, and D and subtype adw2, adr, and ayw3 were present among them. Evidence of transmission from outside family sources was found in addition to intrafamilial transmission among individuals with occult infection. Mutations in the major hydrophilic loop (MHL) of the S gene region were also detected, including the 'vaccine escape' mutation G145R in three cases. Although majority of the occult infection was associated with low viral load, 3/15 (20%) cases were with higher viral load and potential infectivity. These cases are especially notable in diagnostic, blood banking, and transplantation services.

Adolescent↗

PubMed2003

Interruption of nonnucleoside reverse transcriptase inhibitor (NNRTI) therapy for 2 months has no effect on levels of human immunodeficiency virus type 1 in plasma of patients harboring viruses with mutations associated with resistance to NNRTIs.

A 2-month interruption of only nonnucleoside reverse transcriptase inhibitors (NNRTIs) for patients carrying mutations associated with resistance to NNRTIs was followed by no change in either viral load or CD4 cell counts. These data suggest that these compounds have lost all of their in vivo antiviral activity in such cases.

Alkynes↗

PubMed2001

Prevalence of multiple dideoxynucleoside analogue resistance (MddNR) in a cohort of Italian HIV-1 seropositive patients extensively treated with antiretroviral drugs.

As the emergence of highly resistant virus might compromise antiretroviral regimens in HIV-1 infected patients, a constant analysis of genotypic mutations should be performed to establish the magnitude of mutation prevalence and gauge their impact in patients treated extensively with combination therapy. The frequency of multiple dideoxynucleoside analogue resistance (MddNR) was evaluated in a group of Italian HIV-1 seropositive patients who failed to respond to therapy despite a long-lasting drug treatment. Results showed the presence of one or more mutations (A62V, V75I, F77L, F116Y and Q151M) able to confer resistance to all NRTIs in a relatively high percentage (7.9%) of patients enrolled in the study. Moreover, a significantly lower HIV-1 viral replication in patients with MddNR, suggested the importance of monitoring HIV-1 subjects not only by viral load, but also by drug resistance testing, so that a correct drug regimen may be chosen.

Adult↗

PubMed2002

Response to changes in antiretroviral therapy after genotyping in human immunodeficiency virus-infected children.

BACKGROUND: HIV genotyping has been beneficial when choosing salvage regimens in adults failing highly active antiretroviral therapy (HAART). Our objectives were to evaluate the usefulness of genotyping in HIVinfected children failing HAART and to determine whether the presence of resistance mutations was associated with previous antiretroviral therapy. METHODS: We followed the progress of pediatric patients who had HIV genotyping performed after HAART failure. Charts were reviewed at 3-month intervals for 1 year after genotyping for changes in viral load and CD4+ cell percentage. Patients whose antiretroviral therapy was changed after genotyping were compared with those whose medications were not changed. We also compared the proportion of patients with genotypic mutations according to antiretroviral exposure at time of genotyping. RESULTS: Eighteen pediatric patients were eligible for inclusion. None of 10 patients who had antiretroviral therapy changed after genotyping had a decrease in viral load atmonths after genotyping. One of 8 patients who had no changes in antiretroviral therapy had a sustained decrease in viral load at 12 months. Two-thirds of patients had resistance mutations to antiretrovirals without prior exposure to that drug. CONCLUSIONS: This study did not demonstrate substantial clinical benefit to HIV genotyping in antiretroviral agent-experienced pediatric patients with high viral loads. These results contrast with favorable short term clinical and virologic responses to therapeutic changes after genotyping in HIV-infected adults. However, medication history alone does not appear to be an adequate alternative to genotyping in choosing salvage regimens in antiretroviral agent-experienced children.

Adolescent↗

PubMed2001

HIV-1 drug resistance profiles in children and adults with viral load of <50 copies/ml receiving combination therapy.

CONTEXT: The continued release of human immunodeficiency virus type 1 (HIV-1) into plasma at very low levels during highly active antiretroviral therapy (HAART) can be detected using specialized techniques, but the nature and significance of this low-level viremia, especially as related to acquisition of drug resistance mutations, are unclear. OBJECTIVE: To determine genetic resistance profiles of low-level plasma HIV-1 in patients with prolonged viral suppression (<50 copies/mL of plasma HIV-1 RNA) while receiving HAART. DESIGN AND SETTING: Cross-sectional study conducted at a US academic hospital from November 1999 to February 2001 using a novel method for amplification of low levels of viral genomes in plasma. PATIENTS: Eighteen HIV-1-infected patients (7 children and 11 adults), enrolled in a longitudinal study of HIV-1 reservoirs, who had suppression of viral replication while receiving protease inhibitor-containing combination therapy. Two patients (1 adult and 1 child) with less optimal suppression of viral replication were included to assess virus predominating when plasma HIV-1 RNA levels are low but detectable (<1000 copies/mL). Follow-up analyses were conducted in 3 patients. MAIN OUTCOME MEASURE: Detection of drug resistance mutations in clones amplified from low-level plasma virus. RESULTS: Viral sequences were amplified from 8 of the 18 patients with simultaneous plasma HIV-1 measurements of less than 50 copies/mL and from 2 patients with 231 and 50 copies/mL. Clones from 3 treatment-naive patients with less than 50 copies/mL of plasma HIV-1 RNA showed continued release, for as long as 42 months, of wild-type drug-sensitive virus. The 7 patients with prior nonsuppressive therapy, with viral loads below 50 copies/mL and during "blips" to 231 and 64 copies/mL, had only resistance mutations consistent with pre-HAART therapy (although reverse transcriptase inhibitor mutations may have continued to occur). New HAART-related mutations were seen in a control patient with prior viral load levels of about 400 to 1000 copies/mL. For phylogenetic analysis, sequences were available for both resting CD4(+) T cells and plasma HIV for 7 of 10 patients and showed patient-specific clustering of sequences and a close relationship between virus in the plasma and the latent reservoir. CONCLUSIONS: Based on the samples that could be amplified, low-level viremia in children and adults receiving HAART with prolonged suppression of viremia to less than 50 copies/mL of HIV-1 RNA may result primarily from archival, pre-HAART virus, reflecting earlier treatment conditions, and does not appear to require development of new, HAART-selected mutations reflecting partial resistance to therapy. Low-level viremia below 50 copies/mL may represent less of a concern regarding impending drug failure of current HAART regimens. However, the archival drug-resistant virus may be relevant regarding future treatment strategies.

Adult↗

PubMed2004

Occult hepatitis B virus infection in a North American adult hemodialysis patient population.

Hepatitis B virus (HBV) infections continue to occur in adult hemodialysis units. A possible contributing factor is the presence of occult HBV (serum hepatitis B surface antigen [HBsAg] negative but HBV DNA positive). Two hundred forty-one adult hemodialysis patients were screened for occult HBV. HBV DNA testing was performed by real-time polymerase chain reaction (PCR) with 2 independent primer sets (core promoter and surface). Two (0.8%) of the 241 patients were HBsAg positive. Of the remaining 239 HBsAg-negative patients, 9 (3.8%) were HBV DNA positive. Viral loads in these individuals were low (10(2)-10(4) viral copies/mL). Seven of the 9 (78%) were nt 587 mutation (sG145R mutant) positive. Demographic, biochemical, and HBV serological testing did not help to identify those with occult HBV. In conclusion, the prevalence of occult HBV in adult hemodialysis patients in this North American urban center is approximately 4 to 5 times higher than standard HBsAg testing would suggest. The majority of these infections are associated with low viral loads and a high prevalence of the sG145R mutant. Finally, the demographic, biochemical, and/or serological features of HBV DNA-positive subjects do not distinguish these individuals from the remainder of the dialysis patient population.

Adult↗

PubMed1999

Hyperhomocysteinemia and hypofibrinolysis in young adults with ischemic stroke.

BACKGROUND AND PURPOSE: Data from epidemiological and case-control studies suggest that increased total homocysteine (tHcy) levels are associated with increased risk for thromboembolic disease. The mechanisms by which hyperhomocysteinemia contributes to thrombogenesis are incompletely understood. The main objectives of this study of young ischemic stroke patients were (1) to examine fasting and post-methionine load levels of tHcy, (2) to ascertain the genotype frequency of the C677CT mutation in the methylenetetrahydrofolate reductase gene (TT genotype), and (3) to study the possible interaction between plasma tHcy levels and fibrinolytic factors. METHODS: This case-control study was based on 80 consecutive patients aged 18 to 44 years admitted between January 1992 and May 1996 as a result of a first-ever ischemic stroke. Forty-one healthy control subjects were recruited. Measurement of fasting tHcy and post-methionine load levels and evaluation of the fibrinolytic system were undertaken at least 3 months (mean, 5.1+/-1. 9 months) after admission. Genotyping of the methylenetetrahydrofolate reductase gene was performed. RESULTS: Although the increase after methionine loading (ie, postload tHcy minus fasting-level tHcy) was significantly higher among patients, there was no difference in fasting and postload tHcy levels. After adjustment for conventional risk factors, elevated postload increase tHcy levels were associated with a 4.8-fold increased risk of ischemic stroke. There was no difference between patients and control subjects in either TT genotype frequency or T allele frequency. Abnormal response to methionine loading was associated with higher tissue plasminogen activator (tPA) mass concentration, higher plasminogen activator inhibitor-1 levels, and lower tPA activity. After adjustment for age, sex, body mass index, serum cholesterol, and triglycerides, an abnormal increase in postload tHcy levels remained significantly associated with tPA mass concentration levels (P=0.03). CONCLUSIONS: A moderately elevated increase in tHcy levels after methionine loading was associated with an increased risk for ischemic stroke in young adults. In contrast, fasting tHcy levels did not differ between patients and controls. A moderately elevated increase in tHcy after methionine loading may provide a additional thrombogenic risk mediated in part by interactions with the fibrinolytic system. In young stroke patients, a methionine loading test to detect hyperhomocysteinemia should always be considered in the convalescent phase of the disease.

Adolescent↗

PubMed2001

Quantification of human immunodeficiency virus type 1 proviral load by a TaqMan real-time PCR assay.

Proviral human immunodeficiency virus type 1 (HIV-1) DNA could be a useful marker for exploring viral reservoirs and monitoring antiretroviral treatment, particularly when HIV-1 RNA is undetectable in plasma. A new technique was developed to quantify proviral HIV-1 using a TaqMan real-time PCR assay. One copy of proviral HIV-1 DNA could be detected with 100% sensitivity for five copies and the assay had a range of 6 log(10). Reproducibility was evaluated in intra- and interassays using independent extractions of the 8E5 cell line harboring the HIV-1 proviral genome (coefficients of variation [CV], 13 and 27%, respectively) and peripheral blood mononuclear cells (PBMC) from a patient with a mean proviral load of 26 copies per 10(6) PBMC (CV, 46 and 56%, respectively). The median PBMC proviral load of 21 patients, measured in a cross-sectional study, was determined to be 215 copies per 10(6) PBMC (range, <10 to 8,381). In a longitudinal study, the proviral load of 15 out of 16 patients with primary infection fell significantly during 1 year of antiretroviral therapy (P = 0.004). In the remaining patient, proviral HIV-1 DNA was detectable but not quantifiable due to a point mutation at the 5' end of the TaqMan probe. No correlation was observed between proviral load and levels of CD4(+) cells or HIV-1 RNA in plasma. TaqMan PCR is sensitive and adaptable to a large series of samples. The full interest of monitoring proviral HIV-1 DNA can now be ascertained by its application to the routine monitoring of patients.

Anti-HIV Agents↗

PubMed2000

Loss control of Mcm5 interaction with chromatin in cdc6-1 mutated in CDC-NTP motif.

Saccharomyces cerevisiae Cdc6 plays an essential role in establishing and maintaining the prereplicative complex (pre-RC) by interacting with the origin recognition complex (ORC) and associating with chromatin origins. These interactions are required to load minichromosome maintenance proteins (MCMs) and other initiator proteins onto replication origins. Although the temperature-sensitive cdc6 mutant, cdc6-1, has been widely used for these studies, the molecular mechanism of the cdc6-1 mutation has been unclear. In this study, we have identified a base substitution at Gly260-->Asp, near the CDC-NTP motif. Using a chromatin immunoprecipitation assay (CHIP), we found that cdc6-1 fails to load Mcm5 onto the replication origins. Chromatin fractions were used to study Mcm5 binding in both the wildtype and mutant background. These studies indicated that Cdc6 is also involved in unloading Mcm5 from chromatin. Specifically, the cdc6-1 mutation protein, cdc6(G260D), which failed to load Mcm5 onto replication origins, also failed to unload the Mcm5 protein. Furthermore, the overexpression of wildtype CDC6 accelerated the unloading of Mcm5 from chromatin fractions. In the absence of functional Cdc6, the Mcm5 protein showed nonorigin binding to chromatin with the cell cycle arrested at the G1S phase transition. Our results suggested that the cdc6(G260D) mutant protein fails to assemble an operational replicative complex and that wildtype Cdc6 plays a role in preventing re-replication by controlling the unloading the MCMs from chromatin origins.

Amino Acid Substitution↗

PubMed2004

A human immunodeficiency virus type 1-infected individual with low viral load harbors a virus variant that exhibits an in vitro RNA dimerization defect.

We investigated the in vitro RNA dimerization properties of the untranslated leader RNA derived from human immunodeficiency virus type 1 variants circulating in an individual with a low viral load and slow disease progression. The leader sequences of these viruses contain highly unusual polymorphisms within the dimerization initiation site (DIS): an insert that abolishes dimerization and a compensatory substitution. The dimerization of leader RNA from late stages of infection is further improved by additional mutations outside the DIS motif that facilitate a secondary structure switch from a dimerization-incompetent to a dimerization-competent RNA conformation.

Base Sequence↗

PubMed1999

Anti-HIV effect of saquinavir combined with ritonavir is limited by previous long-term therapy with protease inhibitors.

Combination therapy of saquinavir (SQV) and ritonavir (RTV) seems to have a strong antiretroviral effect pharmacokinetically. The purpose of this study was to examine the effectiveness of combined therapy using SQV and RTV in patients previously treated with protease inhibitors (PIs) and to identify the factors compromising the response to such combination therapy. Nineteen HIV-infected Japanese patients participated in this trial between June 1997 and July 1998, and were monitored until November 1998. Patients were treated with SQV (400 mg twice daily) and RTV (300 or 400 mg twice daily). Among the 17 patients who continued such therapy for longer than 3 months, 6 were responders. Among nonresponders, the duration of PI therapy was longer and a higher frequency of preexisting PI resistance viral mutations was detected than in responders. No significant differences were found in previous use of reverse transcriptase inhibitor therapy, CD4+ and CD8+ T cell counts, viral load at baseline, and plasma concentrations of SQV and RTV between responders and nonresponders. Our results suggest that the response to SQV combined with RTV therapy is complicated by previous long-term treatment with PIs, probably owing to multiple PI resistance mutations. Even in patients with a PI-sensitive HIV genotype, however, resistance mutations can develop during therapy and abrogate the effect of high plasma SQV concentrations.

Adolescent↗

PubMed2004

Genotypic resistance and HIV-1 subtype in Brazilian children on dual and triple combination therapy.

BACKGROUND: Antiretroviral therapy is provided by the Brazilian Ministry of Health to eligible HIV-infected individuals. Based on clinical and immunological classification, the Brazilian guidelines recommend dual or triple therapy for children. However, the development of drug-resistant strains or poor adherence to therapy could impact the efficacy of this approach. OBJECTIVES: We examined relationships between RNA levels, CD4+ T-cell counts, treatment history, and the prevalence of drug-resistant variants in a cohort of HIV-1-infected children in Rio de Janeiro, Brazil. STUDY DESIGN: Direct sequencing of reverse transcriptase and protease genes from plasma was performed. Virologic and CD4+ T-cell counts responses to therapy were assessed by changes in HIV-1 RNA levels and CD4+ T-cell counts from baseline. RESULTS: Thirty-seven patients were receiving dual therapy and 38 were on triple therapy at enrollment, segregated by antiretroviral history. Both groups had a higher increase in CD4+ T cell counts and a lower viral load in pre-treatment antiretroviral-naïve subjects. Notably, there was a direct correlation between the higher frequencies of drug-resistance mutations and cross-resistance with previous usage of antiretroviral (ARV) therapy in both groups. Non-B subtypes isolates were found in 21.3% of samples. A smaller increase in CD4+ T cell counts was found between non-B subtypes when compared to B-subtypes. CONCLUSIONS: These results suggest that less immunological recovery and a higher number of mutations related to drug resistance were associated with previous usage of ARV and consequent higher time under drug selective pressure in these HIV-infected Brazilian children. These facts suggest the preferential use of triple drug combination as first line regimen in children.

Adolescent↗

PubMed1999

HIV-1 rebound during interruption of highly active antiretroviral therapy has no deleterious effect on reinitiated treatment. Comet Study Group.

BACKGROUND: Potent antiretroviral therapy (ART) with a protease inhibitor-based regimen is commonly used to treat HIV-1-infected patients. Transient treatment interruptions because of drug intolerance or other reasons are not uncommon. HIV-1 dynamics during therapy interruption and its consequences for the subsequent reinitiation of therapy have not been properly studied. METHODS: Ten antiretroviral-naive, HIV-1-infected subjects (mean baseline CD4 cell count of 414 cells/mm3 and plasma viral load of 4.8 log10 copies/ml) were treated with the triple drug ART regimen indinavir/zidovudine/lamivudine for 28 days. Therapy was then interrupted for 28 days, after which the same ART regimen was re-started. RESULTS: HIV-1 in plasma declined during the first 7 days of therapy with T1/2 of 1.5 days, and during days 7-28 with T1/2 of 8.9 days. Once therapy was interrupted, a delay of 4-7 days was observed in all subjects, preceding a rapid viral rebound with a mean doubling time of 1.6 days. Mean viral load after 28 days of interruption was 96% of baseline. Upon reinitiation of the same ART regimen, viral load declined at rates similar to those observed during the initial therapy (T1/2 of 1.6 and 8.0 days, respectively). No resistance-conferring mutations were observed in the HIV-1 reverse transcriptase (RT) and protease regions after the interruption of therapy. Plasma viral loads were maintained below 200 copies/ml in subjects continuing therapy for 4 (n = 9) to 12 (n = 5) months, with a mean CD4 cell count increase of 145 cells/mm3. CONCLUSIONS: The reintroduction of efficient ART therapy after a 1 month interruption shows viral kinetics similar to that of naive patients, and is not associated with the development of resistance. No deleterious effect on the reinitiated therapy was observed in patients who temporarily discontinued ART therapy. Nevertheless, because viral load rebounds back to baseline during treatment interruption, viral suppression is in effect put off by that period of time.

Anti-HIV Agents↗

PubMed2002

Prevalence of primary and secondary resistant mutations to antiretroviral drug in a population of Puerto Rican infected with HIV.

INTRODUCTION: Several studies have reported increasing number of therapeutic failures with HAART in HIV-infected individuals. In order to assess the impact HIV antiretroviral resistance could have on treatment, we decided to determine the prevalence of primary and secondary antiretroviral resistant genotypes in a population of HIV-infected Puerto Ricans and compare the mutational distribution pattern with that reported in Europe and US. METHOD: In a total of 80 plasma samples from patients with detectable viral load of over 1,000 RNA copies/ml, the Trugene Visible Genetics HIV sequencing method was used to detect antiretroviral resistance mutations. RESULTS: We found 55 subjects (69%) with high level of resistance to ZDV in the reverse transcriptase gene and 46 subjects (58%) with high level of resistance to NFV in the protease gene. Mutation frequencies to the NRTI ranged in appearance from as high as 54% (i.e., M184V) in the studied subjects to a low of less than 5% (i.e., M184I and V75T). For the NNRTI the most common mutation was K103N in 40% of the subjects and found to confer cross resistance to NVP, DLV and EFV. Another concerning finding is the increasing trend of the frequency of primary and secondary resistant mutations from year 2000 to 20001. Nine (23%) of the total detected primary mutations, to either RTI or PI, showed an increase of at least 5% from one year to the other. Similarly, there were 6 (11%) secondary resistant mutations showing an increase of at least 5% during the two years studied. CONCLUSIONS: In two year period we detected a tendency to increase in primary and secondary HIV-resistant mutation in a population of HIV-infected Puerto Ricans.

Anti-HIV Agents↗

PubMed2006

Mutations in carboxy-terminal part of E2 including PKR/eIF2alpha phosphorylation homology domain and interferon sensitivity determining region of nonstructural 5A of hepatitis C virus 1b: their correlation with response to interferon monotherapy and viral load.

AIM: To study the amino acid substitutions in the carboxy (C)-terminal part of E2 protein and in the interferon (IFN) sensitivity determining region (ISDR) and their correlation with response to IFN and viral load in 85 hepatitis C virus (HCV)-1b-infected patients treated with IFN. METHODS: The C-terminal part of E2 (codons 617-711) including PKR/eIF2alpha phosphorylation homology domain (PePHD) and ISDR was sequenced in 85 HCV-1b-infected patients treated by IFN monotherapy. RESULTS: The amino acid substitutions in PePHD detected only in 4 of 85 patients were not correlated either with response to IFN or with viral load. The presence of substitutions in a N-terminal variable region (codons 617-641) in the C-terminal part of E2 was significantly correlated with both small viral load (33.9% vs 13.8%, P = 0.0394) and sustained response to IFN (25.0% vs 6.9%, P = 0.0429). Four or more substitutions in ISDR were significantly correlated with both small viral load (78.6% vs 16.2%, P < 0.0001) and sustained response to IFN (85.7% vs 2.9%, P < 0.0001). In multivariate analysis, ISDR in nonstructural (NS) 5A (OR = 0.39, P < 0.0001) and N-terminal variable region (OR = 0.51, P = 0.039) was selected as the independent predictors for small viral load, and ISDR (OR = 39.0, P < 0.0001) was selected as the only independent predictor for sustained response. CONCLUSION: The N-terminal variable region in the C-terminal part of E2 correlates with both response to IFN monotherapy and viral load and is one of the factors independently associated with a small viral load.

Adult↗

PubMed2002

Extent and importance of cross-resistance to efavirenz after nevirapine failure.

The objective of this study was to evaluate the activity of efavirenz after the failure of a nevirapine-containing regimen. This prospective study included 47 patients with plasma HIV loads >1000 copies/ml, and who had received nevirapine for at least 16 weeks, included in an efavirenz-based salvage regimen. The main outcome measure was virological response, defined as an HIV RNA level decrease of at least 1 log(10) copies/ml after 24 weeks, according to genotypic and phenotypic resistance to efavirenz. Phenotypic resistance was defined as a >10-fold increase in the IC(50). The median CD4(+) cell count was 236 x 10(6)/liter and the median HIV RNA level was 4.5 log(10) copies/ml. Mutations known to decrease susceptibility to nonnucleoside reverse transcriptase inhibitors were observed in 79% of patients, predominantly at residues 181 (49%), 103 (40%), and 106 (19%), but phenotypic resistance to efavirenz was seen in 62% of cases. All the strains with the K103N mutation showed high-level resistance to efavirenz, in contrast with 20% of those carrying exclusively the Y181C mutation. By week 24, 38% of patients had responded and 19% had achieved an undetectable HIV load. Virological failure was observed in patients with phenotypic resistance to efavirenz (67 vs. 11%; relative risk [RR], 4; 95% confidence interval [CI], 1.07-14.89; p = 0.04), or in presence of the K103N mutation (52 vs. 17%; RR, 1.77; 95% CI, 1.12-2.79; p = 0.02), and these results remained unchanged after adjusting for HIV load, or by resistance to the accompanying drugs in the salvage regimen. A previous longer period of nevirapine therapy was significantly associated with the emergence of efavirenz resistance (288 vs. 170 days, p < 0.01). We conclude that genotypic and/or phenotypic resistance assays permit the sequential use of nonnucleoside reverse transcriptase inhibitors in the clinical setting. Our data suggest that an early change after nevirapine failure could avoid the emergence of efavirenz resistance.

Alkynes↗

PubMed2005

Maternal mutation 677C > T in the methylenetetrahydrofolate reductase gene associated with severe brain injury in offspring.

A frequent polymorphism in the gene coding for 5,10-methylenetetrahydrofolate reductase is the substitution 677C > T which produces a thermolabile and inefficient enzyme. Homozygosity for the 677C > T allele is the most important determinant of hyperhomocys-teinemia, when folic acid intake is reduced. Most studies on the relationship between the 677C > T variant in the mother and defects in the offspring have focused on neural-tube defects. This study is a retrospective case-control investigation of hypoxic-ischemic encephalopathy of the newborn (HIEN) with reference to the 677C > T polymorphism as a genetic risk for this condition. The prevalence of the 677C > T allele was studied in 11 children with HIEN, their respective mothers, and 85 healthy individuals. Plasma homocysteine levels after fasting and methionine loading were determined in both mothers and controls. Ten of 11 patients were evaluated using magnetic resonance (MR) imaging, and all showed multicystic encephalomalacia and severe brain vasculopathy. Seven mothers were homozygous and four heterozygous for the 677C > T allele. Five of the children were homozygous and six heterozygous for this polymorphism. The variant allele frequency was higher in the group of mothers with affected children than in the controls and was associated with an increase in plasma homocysteine after methionine loading, in the group of mothers than in controls. The 677C > T mutation in mothers, either in a homozygous or heterozygous state, together with poor nutritional status (probable folate deficiency) may represent a risk factor for irreversible HIEN in the offspring.

Brain Damage, Chronic↗

PubMed2006

Phenotypic susceptibility to didanosine is associated with antiviral activity in treatment-experienced patients with HIV-1 infection.

OBJECTIVE: We investigated the relationship between human immunodeficiency virus (HIV) phenotypic susceptibility to didanosine and the antiviral activity of didanosine (ddI) in the JAGUAR study. METHODS: Baseline plasma HIV phenotypic susceptibility to ddI was assessed using a phenotype assay of patients randomized to receive ddI or placebo for 4 weeks in addition to their current regimen. Phenotypic susceptibility scores (PSSs) were then calculated for each sample. Associations between PSS and week 4 reductions in plasma HIV-1 RNA load or virologic response were assessed using linear regression and Jonckherre's test and the Wilcoxon and Cochran-Armitage tests, respectively. RESULTS: In the ddI arm, a significant association between reduction in viral load and continuous PSS was observed (P<.0001). Using distinct categories, an increasing fold change (FC) in susceptibility to ddI was strongly associated with smaller reductions in plasma HIV-1 RNA load (P<.0001). The proportion of virologic responders was 83% (15/18) for patients with a ddI FC < or =1.3, 50% (33/66) for patients with an FC of 1.3-2.2, and 29% (4/14) for patients with an FC > or =2.2 (P=.0008). After we determined these findings, 3 ddI FC categories were defined using 1.3 and 2.2 as thresholds. CONCLUSIONS: The relationship between phenotypic susceptibility to ddI and reduction in plasma HIV-1 RNA load describes a continuum. The establishment of a lower clinical cutoff at 1.3 and an upper clinical cutoff at 2.2 are clinically relevant.

Anti-HIV Agents↗