Determinants of residual viraemia during combination HIV treatment: Impacts of baseline HIV RNA levels and treatment choice

OBJECTIVES

Effective HIV therapy reflects suppression of plasma HIV RNA levels below assay detection thresholds, although lower levels of "residual viraemia" have also been demonstrated over extended periods of effective antiretroviral treatment. Here we examine the determinants of HIV RNA suppression below the standard assay threshold (40 HIV-1 RNA copies/mL) as well as factors associated with detectable HIV RNA below this reported detection limit.

METHODS

Between 2007 and 2010, 11 575 consecutive viral load (VL) tests were obtained from 1540 patients, including 356 on effective antiretroviral therapy followed since initiation (1996-2001: n = 165; 2002-2009: n = 191). Analyses modelled the probability of an undetectable VL given successful suppression to < 200 copies/mL, and the probability of residual viraemia given an undetectable result.

RESULTS

Detectable HIV RNA amplification was demonstrated in 20% of samples with a VL result < 40 copies/mL. Longitudinal analyses from 356 patients revealed that the likelihood of achieving results < 40 copies/mL was increased with current nonnucleoside reverse transcriptase inhibitor (NNRTI) therapy [odds ratio (OR) 2.0; P < 0.05] and reduced with prior virological rebound (OR 0.5; P < 0.05). In contrast, the presence of detectable HIV RNA < 40 copies/mL was strongly associated with pretreatment HIV RNA levels among those on current protease inhibitor (PI) treatment (OR 1.5 per log10 copies/mL increase; P = 0.02) as well as those on NNRTIs (OR 1.7; P = 0.002).

CONCLUSIONS

While HIV treatment history was associated with plasma HIV RNA levels below the detection limit, residual viraemia results were dominantly determined by pretreatment VL. These findings support the concept of a stable, long-lived reservoir of latently infected cells as a source of residual viraemia despite effective HIV treatment.

Association between 25-OH vitamin D and insulin is independent of lipoatrophy in HIV

OBJECTIVE

Vitamin D deficiency (VDD) is prevalent in HIV, and following antiretroviral therapy (ART), increased rates of lipoatrophy and metabolic abnormalities are described. We investigated the relationships between 25-hydroxyvitamin D [25(OH)D] and other metabolic parameters in a group of HIV patients with and without lipoatrophy to examine whether lipoatrophy could explain the high prevalence of VDD and metabolic abnormalities.

BACKGROUND

Vitamin D receptors are expressed in adipose tissue implicating vitamin D, through paracrine/autocrine mechanism, in exerting effects on fat metabolism. HIV patients frequently suffer from VDD, and those treated with thymidine analogues frequently suffer from lipoatrophy so we investigated whether lipoatrophy could explain these associations.

DESIGN AND PATIENTS

Cross-sectional study of HIV-infected male patients (n = 107; 39 with lipoatrophy) from the West Australian cohort with measurements of 25(OH)D, adiponectin, insulin, lipids and leg fat as a percentage of mass.

RESULTS

Reduced 25(OH)D levels were common and significantly associated with higher serum insulin in the entire cohort (P = 0·006), but there was no difference in 25(OH)D between untreated and antiretroviral-treated patients with or without lipoatrophy. Treated patients with lipoatrophy were more likely to take thymidine analogue therapy, were older and on therapy longer than treated patients without lipoatrophy. Adiponectin levels did not correlate with 25(OH)D, but lipoatrophic-treated patients had lower levels of adiponectin compared with nonlipoatrophic-treated patients.

CONCLUSIONS

Lower 25(OH)D is associated with higher serum insulin but not lipoatrophy or hypoadiponectinemia in HIV-infected patients. The association between VDD and insulin resistance is likely to be mediated by independent mechanisms.

Evaluation of IL12B as a candidate type I diabetes susceptibility gene using data from the Type I Diabetes Genetics Consortium

As part of its efforts to identify genes affecting the risk of type I diabetes (T1D), the Type I Diabetes Genetics Consortium commissioned an extensive survey of variants associated with genes reported earlier to have an association with disease susceptibility. In this report, we present the analysis of a set of single-nucleotide polymorphisms (SNPs) within and flanking the IL12B gene, which encodes the p40 subunit of the cytokines interleukin (IL)-12 and IL-23. No SNP showed individually significant association in the population as a whole. Nevertheless, subjects stratified according to genotype at the earlier reported SNP in the IL12B 3'UTR, rs3212227, confirmed small, but significant, differences in age of disease onset with a relative hazard=0.88 (P=0.005). The protective effect of rs3212227 allele 2 was gender specific (P=0.004 overall and P=0.0003 when unaffected siblings were considered). Among females, the 2.2 genotype was more protective, with relative hazard=0.75. We conclude that while there was no major effect of IL12B polymorphisms on T1D susceptibility in the entire study group, they have an impact on a subset of at-risk individuals.

Effect of linkage status of affected sib-pairs on the search for novel type 1 diabetes susceptibility genes in the HLA complex

AIM

Type 1 diabetes susceptibility is influenced by a number of genes, of which those with the strongest effects map to the human leucocyte antigen (HLA) complex. Evidence for linkage of non-HLA genes in several affected sib-pair analyses was increased if the HLA or gender status of the sibs was considered independently. We investigated whether linkage status at the HLA complex differentially affected transmission of alleles to sibs depending on their HLA or gender linkage status.

METHODS

Genotypes of 2437 markers typed on 11 279 individuals from 2363 families, stratified according to HLA and gender, were examined using the transmission disequilibrium test.

RESULTS

Several significant single nucleotide polymorphisms (SNPs) loci were found near the class II genes; no significant SNPs were found by these analyses near the class I or class II genes. Other significant effects were found when the gender of the sibs or the parents was considered. There was not a significant difference in HLA-DRB genotypes between the stratified sets.

CONCLUSIONS

These results suggest the presence of novel recessive susceptibility gene(s) within the HLA complex.

Association of MHC SNP genotype with susceptibility to type 1 diabetes: a modified survival approach

AIM

The Major Histocompatibility Complex (MHC) is a highly polymorphic region on chromosome 6 encompassing the human leucocyte antigen (HLA)-DQ/DR loci most predictive of susceptibility to type 1 diabetes (T1D). To assess the contribution of other MHC genes, in this exploratory analysis of Type 1 Diabetes Genetics Consortium (T1DGC) family data we characterize association between susceptibility and MHC single nucleotide polymorphism (SNP) genotype, with an emphasis on effects of genetic variation additional to carriage of predisposing or protective MHC haplotypes.

METHODS

We use Cox regression analyses of age of onset, stratified by family, to jointly test both linkage and association. Analysis is restricted to children from families having both affected and unaffected siblings and is conducted with and without adjustment for known HLA class I and II effects. Model fits provide scores for each individual that are based on estimates of the probability of being affected by the age of 35, given the individual's SNP genotype. The mean within-family variation in these scores provides a measure that closely reflects the relative size of the likelihood ratio test statistics, and their covariation provides a means of mapping patterns of association that incorporate both effect size and commonality of effect that is attributable to the strong linkage disequilibrium (LD) extending across the region.

RESULTS

Univariate analyses yielded strong associations with T1D susceptibility that are dominated by SNPs in the class II HLA-DR/DQ region but extend across the MHC. Similar effects are frequently observed across SNPs within multiple genes, sometimes spanning hundreds of kilobases. SNPs within a region at the telomeric end of the class II gene HLA-DRA yielded significant associations with and without adjustment for carriage of the predictive DR3, DR4, DR2 and DR7 HLA haplotypes, and remained highly prominent in a secondary analysis that was restricted to 66 families in whom at least one of the affected siblings carried neither the DR3 nor DR4 haplotype.

CONCLUSIONS

While many of the associations can be attributed to LD between the SNPs and the dominant HLA-DRB/DQA/DQB loci, there is also evidence of additional modifying effects.

Missingness in the T1DGC MHC fine-mapping SNP data: association with HLA genotype and potential influence on genetic association studies

AIM

The absence or 'missingness' of single nucleotide polymorphism (SNP) assay values because of genotype or related factors of interest may bias association and other studies. Missingness was determined for the Type 1 Diabetes Genetics Consortium (T1DGC) Major Histocompatibility Complex (MHC) data and was found to vary across the region, ranging up to 11.1% of the non-null proband SNPs, with a median of 0.3%. We consider factors related to missingness in the T1DGC data and briefly assess its possible influence on association studies.

METHODS

We assessed associations of missingness in the SNP assay data with human leucocyte antigen (HLA) genotype of the individual and with SNP genotypes of the parents. Within-cohort analyses were combined (over all cohorts) using (i) Mantel-Haenszel tests for two-by-two tables or (ii) by combining test statistics for larger tables and regression models. Mixed effect regression models were used to assess association of the SNP genotypes with affected status of the offspring after adjustment for parental SNP genotypes, cohort membership and HLA genotypes. Log-linear models were used to assess association of missingness in the unaffected sib assays with SNP genotypes of the probands.

RESULTS

Missingness of SNP values near the HLA class I (A, B and C) and class II (DR, DQ and DP) loci is strongly associated with carriage of corresponding HLA genotypes within these groups. Similar associations pertain to missing values among the microsatellite data. In at least some of these cases, regions of missingness coincided with known deletion regions corresponding to the associated HLA haplotype. We conjecture that other regions of associated missingness may point to similar haplotypic deletions. Analysis of association patterns of SNP genotypes with affected status of offspring does not indicate strong informative missingness. However, association of missingness in proband data with parental SNP genotypes may impact transmission disequilibrium test (TDT)-type analyses. Comparisons of affected and unaffected siblings point to possible susceptibility regions additional to the classical HLA-DR3/4 alleles near BAT4-LY6G5B-BAT5 and NOTCH4.

CONCLUSIONS

Potentially informative missingness in SNP assay values in the MHC region may impact on association and related analyses based on the T1DGC data. These results suggest that it would be prudent to assess the degree to which missingness may abrogate assessed SNP disease markers in such studies. Initial analyses based on comparison of affected and unaffected status in offspring suggest that at least these may be little affected.

Evidence-based, multifactorial approach to addressing non-adherence to antiretroviral therapy and improving standards of care

BACKGROUND

Near-perfect adherence to antiretroviral therapy over time is critical to achieve viral suppression and recovery of functional immunity in individuals infected with HIV. The concept of adherence as a dynamic behaviour influenced by multiple biopsychosocial factors motivated us to implement an integrated, multifactorial programme in our hospital-based setting. The aims of this study were to survey the scope and determinants of non-adherence in patients attending the Ambulatory HIV Service at Royal Perth Hospital, to develop a method for longitudinal monitoring and to implement measures tailored to support individuals.

METHODS

The US Adult AIDS Clinical Trials Group self-report baseline adherence, follow-up and side-effect questionnaires were used to survey 247 patients at two time-points between September 2002 and February 2003. A longitudinal monitoring method was developed and the WA HIV Cohort Study database used to collate results with clinical markers up to December 2005.

RESULTS

Adherence was associated with viral suppression and CD4 T-cell recovery and improved over the 3-year period under observation (all P < 0.001). Diminishing adherence was associated with younger age (P = 0.002), substance use (P < 0.01), perceived stress (P = 0.04) and indicators of depression (P = 0.03). The analyses showed relationships between personal experience of side-effects and the depression indicator scale in patients on antiretroviral therapy.

CONCLUSION

The programme resulted in an improvement in adherence in our cohort even after adjusting for pill burden, dosing frequency and highly active antiretroviral therapy regimen and has enhanced focus on patients vulnerable to non-adherence while supporting those not currently at risk.

Influence of inhibitory killer immunoglobulin-like receptors and their HLA-C ligands on resolving hepatitis C virus infection

An estimated 2%-3% of the world's population is chronically infected with hepatitis C virus (HCV) and this is a major cause of liver disease worldwide. Following acute infection, outcome is variable with acute HCV successfully resolved in some individuals (20%-30%), but in the majority of cases the virus is able to persist. Co-infection with human immunodeficiency virus has been associated with a negative impact on the course of HCV infection. The host's immune response is an important correlate of HCV infection outcome and disease progression. Natural killer (NK) cells provide a major component of the antiviral immune response by recognising and killing virally infected cells. NK cells modulate their activity through a combination of inhibitory and activatory receptors such as the killer immunoglobulin-like receptors (KIRs) that bind to human leukocyte antigen (HLA) Class I molecules. In this workshop component, we addressed the influence of KIR genotypes and their HLA ligands on resolving HCV infection and we discuss the implications of the results of the study of Lopez-Vazquez et al. on KIR and HCV disease progression.

Prospective genetic screening decreases the incidence of abacavir hypersensitivity reactions in the Western Australian HIV cohort study

Abacavir therapy is associated with significant drug hypersensitivity in approximately 8% of recipients, with retrospective studies indicating a strong genetic association with the HLA-B*5701 allele. In this prospective study, involving 260 abacavir-naive individuals (7.7% of whom were positive for HLA-B*5701), we confirm the usefulness of genetic risk stratification, with no cases of abacavir hypersensitivity among 148 HLA-B*5701-negative recipients.

Killer immunoglobulin-like receptors and HLA act both independently and synergistically to modify HIV disease progression

Variation in the host response to infection by pathogens including HIV-1 may be conferred by polymorphic genetic factors such as HLA and killer immunoglobulin-like receptors (KIR) genes. Here, we examined KIR and HLA genotype effects on pretreatment viral load, rate of CD4(+) T-cell decline and progression to AIDS among adult HIV-1-infected patients within the Western Australian HIV Study Cohort. In this study, carriage of KIR genes within the 'B' haplotype (eg KIR2DS2) was specifically associated with a more rapid CD4(+) T-cell decline over time and progression to AIDS. In contrast, KIR gene repertoire had no effect on pretreatment viral load while selected HLA alleles (eg HLA-B*5701, HLA-B*2705) demonstrated significant protective effects on viremia. Furthermore, interactions between specific HLA and KIR genes did appear to influence HIV disease progression. The results suggest that host genetic variation within the HLA and KIR gene complexes have clinically relevant effects on the course of HIV-1/AIDS, acting independently as well as synergistically to modify disease progression at multiple levels.

The effect of granulocyte-macrophage colony-stimulating factor (GM-CSF) on primitive hematopoietic stem cell (PHSC) function and numbers, after chemotherapy

OBJECTIVE

Primitive hematopoietic stem cell function was assessed after cyclophosphamide with granulocyte-macrophage colony-stimulating factor (GM-CSF), with or without preadministration of interleukin-1, using competitive repopulation.

METHODS

C57B6/J mice injected with one or four biweekly intravenous injections of cyclophosphamide, 200 mg/kg, received granulocyte-macrophage colony-stimulating factor, 1 microg, subcutaneously for 5 days, beginning 24 hours after cyclophosphamide. Alternatively, mice were injected with interleukin-1, 1 microg, 20 hours before administration of drug or drug and cytokine. Marrow obtained from mice sacrificed 4 weeks after the last dose of drug or drug and cytokine was used in competitive repopulation.

RESULTS

Significant reductions in marrow repopulating ability occurred after a single dose of cyclophosphamide or multiple injections. Repopulating units (RU) were calculated, and both binomial and Poisson models for estimation of primitive hematopoietic stem cell (PHSC) numbers were used. RU were significantly diminished for all treatment groups when compared to controls. PHSC numbers were not significantly affected by either regimen of cyclophosphamide given alone. Addition of GM-CSF to cyclophosphamide, whether the latter was given in single or multiple doses, led to further, although insignificant, declines in repopulating ability, as well as PHSC and RU numbers. Interleukin-1 usage exacerbated the observed repopulating defect. There was evidence of replicative failure in individual cells, indicating a qualitative defect also.

SUMMARY

Additive stem cell depletion and qualitative replicative defect occur after chemotherapy-cytokine usage. However, the replicative defect of PHSC seen after addition of GM-CSF is not significantly worse than that seen with cytotoxic drug use alone.

Stable or increasing bone mineral density in HIV-infected patients treated with nelfinavir or indinavir

BACKGROUND AND OBJECTIVES

To determine the factors contributing to changes in bone mineral density (BMD) over time in HIV-infected patients receiving highly active antiretroviral therapy (HAART).

METHODS

Analyses of lumbar spine BMD in 183 male Caucasian participants in the Western Australian HIV Cohort study, comprising a longitudinal analysis of data from 54 patients on stable HAART regimens, and a cross-sectional analysis comparing data from 131 protease inhibitor (PI)-treated patients and 52 PI-naive (including 28 antiretroviral treatment-naive) patients.

RESULTS

Average lumbar spine BMD remained stable or increased over the time frame considered. Although there was no evidence of a change of average BMD over time in patients receiving nelfinavir (P = 0.92), there was evidence of increasing bone density in the indinavir group (average increase, 0.31 z-score per year; P < 0.001). Lower initial z-scores in the longitudinal analysis were significantly associated with lower pre-HAART BMI (P = 0.003), consistent with results of the cross-sectional analysis in which lowest BMI prior to initial dual X-ray absorptiometry scan was associated with decreased BMD (P = 0.02, overall group). Although PI therapy was also associated with decreased BMD in a univariate analysis of the cross-sectional data (P = 0.04), this effect was abrogated in a multiple linear regression analysis (P = 0.11) with lowest BMI remaining significant (P = 0.04).

CONCLUSIONS

We found no evidence, overall, of accelerated bone loss in patients treated with nelfinavir- or indinavir-containing HAART regimens, and propose that indinavir therapy may be associated with an increase in bone mineral density over time. Pre-HAART BMI was an independent and powerful determinant of an individual's initial z-score in the longitudinal analysis, and adjustment for this effect in a cross-sectional analysis abrogated the association between PI therapy and decreased lumbar spine z-score.

Analysis of the stem cell sparing properties of cyclophosphamide

OBJECTIVES

Cyclophosphamide was examined for its ability to spare the most primitive hematopoietic stem cell (PHSC).

METHODS

C57BL6/J mice (Groups A and B) were sacrificed 24 h and 4-6 wk, respectively, after a single or second injection of low-dose cyclophosphamide (90 mg/kg) on days 1, 3, 7, or 15. A competitive repopulation assay was then performed, using B6-HbbdGpi-1a competitor cells, to determine the repopulating ability of exposed PHSC.

RESULTS AND CONCLUSIONS

PHSC function was preserved after a single injection of cyclophosphamide and after a second injection on days 7 and 15 in both groups. In Group A, PHSC repopulating ability declined after a second injection on days 1 and 3 (p<0.05 only for day 1), as did repopulating units [RU]; PHSC numbers did not. In Group B, an insignificant decrease in repopulating ability and RU numbers was observed after a second injection on days 1 and 3, suggesting different etiologies for losses in the 2 groups, or correction of drug-induced defects within 1 month of cyclophosphamide administration. Total RU increased in single, day 1, 7 and 15 treatment groups. A significant number of marrow cells entered the S phase after cyclophosphamide dosing on day 3, and it is possible that a relationship exists between cell cycling and replicative damage. DNA damage was also increased 1 and 3 d after cyclophosphamide administration, although the significance of differences from controls was not definitive.

CONCLUSION

Low-dose cyclophosphamide can spare stem cells, depending upon the timing of subsequent doses.

Language proficiency and the prediction of spontaneous rehearsal in children who are deaf

This study was an investigation of the role of language proficiency and automatization of language skills in the use of spontaneous rehearsal strategies by children who are deaf. Thirty-one profoundly deaf children, 7 to 13 years old, were given a serial recall task, a test of language proficiency (the Language Proficiency Profile-I), and a rapid automatized naming (RAN) task. Similar to previous studies, when the data were examined by age, an apparent developmental lag was observed in the children's spontaneous use of a cumulative rehearsal strategy. Logistic regression analyses further demonstrated that age was actually a nonsignificant predictor of rehearsal use, but that both language proficiency and the automatization of language skills were highly significant predictors. In subsequent hierarchical analyses, automatized language was a partial mediator of the language proficiency --> rehearsal use relation. These results provided support for the view that automatization of language skills is an important and perhaps necessary contribution to the relation between language proficiency and rehearsal use, but that other additional aspects of language proficiency also affect the child's use of a strategy. These findings were discussed in relation to Cummins' (1984) model of language proficiency.

Glutamine cycle enzymes in the crayfish giant nerve fiber: implications for axon-to-glia signaling

Two of the key enzymes involved in glutamate metabolism, glutaminase and glutamine synthetase, were quantitatively localized to axons and glia of the crayfish giant nerve fiber by immunocytochemistry and electron microscopy of antibody-linked gold microspheres. In Western blots, rabbit antisera for glutamine synthetase and glutaminase specifically recognized crayfish polypeptides corresponding approximately in size to subunits of purified mammalian brain enzymes. Glutamine synthetase immunoreactivity was found to be 11 times greater in the adaxonal glial cells than in the axon. Glutaminase immunoreactivity was found in somewhat greater concentration (2.5:1) in glia as compared to axoplasm. Glutamate immunoreactivity also was evaluated and found to be present in high concentration in both glia and axons, as might be expected for an important substrate of cellular metabolism. Using radiolabeled substrates it was demonstrated that glutamine and glutamate were interconverted by the native enzymes in the intact crayfish giant nerve fiber and that the formation of glutamine from glutamate occurred in the axoplasm-free nerve fiber, the cellular component of which is primarily periaxonal glia. The results of this investigation provide immunocytochemical and metabolic evidence consistent with an intercellular glutamine cycle that modulates the concentration of periaxonal glutamate and glutamine in a manner similar to that described for perisynaptic regions of the vertebrate central nervous system. These findings further corroborate previous electrophysiological evidence that glutamate serves as the axon-to-glial cell neurochemical signal that activates glial cell mechanisms responsible for periaxonal ion homeostasis.

Unknown extra cardiac echo-free space: diagnosis of a left ventricular pseudoaneurysm by color flow echocardiography

At times, visualization of a ventricular pseudoaneurysm by two-dimensional echocardiography can be difficult. This case report describes the unique diagnostic potential of color flow echocardiography in the diagnosis of an unknown extra cardiac echo-free space, a left ventricular pseudoaneurysm. Using color Doppler echocardiography flow can be seen communicating between the left ventricle and the pseudoaneurysm.