Comparison of rectal swabs and fecal samples for the detection of Clostridioides difficile infections with a new in-house PCR assay

The detection of Clostridioides difficile infections (CDI) relies on testing the stool of patients by toxin antigen detection or PCR methods. Although PCR and antigenic methods have significantly reduced the time to results, delays in stool collection can significantly add to the turnaround time. The use of rectal swabs to detect C. difficile could considerably reduce the time to diagnosis of CDI. We developed a new rapid PCR assay for the detection of C. difficile and evaluated this PCR assay on both stool and rectal swab specimens. We recruited a total of 623 patients suspected of C. difficile infection. Stool samples and rectal swabs were collected from each patient and tested by our PCR assay. Stool samples were also tested by the cell cytotoxicity neutralization assay (CCNA) as a reference. The PCR assay detected C. difficile in 60 stool specimens and 61 rectal swabs for the 64 patients whose stool samples were positive for C. difficile by CCNA. The PCR assay detected an additional 35 and 36 stool and rectal swab specimens positive for C. difficile, respectively, for sensitivity with stools and rectal swabs of 93.8% and 95.3%, specificity of 93.7% and 93.6%, positive predictive values of 63.2% and 62.9%, and negative predictive values of 99.2% and 99.4%. Detection of C. difficile using PCR on stools or rectal swabs yielded reliable and similar results. The use of PCR tests on rectal swabs could reduce turnaround time for CDI detection, thus improving CDI management and control of C. difficile transmission.

IMPORTANCE

Clostridioides difficile infection (CDI) is the leading cause of healthcare-associated diarrhea, resulting in high morbidity, mortality, and economic burden. In clinical laboratories, CDI testing is currently performed on stool samples collected from patients with diarrhea. However, the diagnosis of CDI can be delayed by the time required to collect stool samples. Barriers to sample collection could be overcome by using a rectal swab instead of a stool sample. Our study showed that CDI can be identified rapidly and reliably by a new PCR assay developed in our laboratory on both stool and rectal swab specimens. The use of PCR tests on rectal swabs could reduce the time for the detection of CDI and improve the management of this infection. It should also provide a useful alternative for infection-control practitioners to better control the spread of C. difficile.

Alterations in Th17 Cells and Non-Classical Monocytes as a Signature of Subclinical Coronary Artery Atherosclerosis during ART-Treated HIV-1 Infection

Cardiovascular disease (CVD) remains an important comorbidity in people living with HIV-1 (PLWH) receiving antiretroviral therapy (ART). Our previous studies performed in the Canadian HIV/Aging Cohort Study (CHACS) (>40 years-old; Framingham Risk Score (FRS) > 5%) revealed a 2-3-fold increase in non-calcified coronary artery atherosclerosis (CAA) plaque burden, measured by computed tomography angiography scan (CTAScan) as the total (TPV) and low attenuated plaque volume (LAPV), in ART-treated PLWH (HIV+) versus uninfected controls (HIV-). In an effort to identify novel correlates of subclinical CAA, markers of intestinal damage (sCD14, LBP, FABP2); cell trafficking/inflammation (CCL20, CX3CL1, MIF, CCL25); subsets of Th17-polarized and regulatory (Tregs) CD4+ T-cells, classical/intermediate/non-classical monocytes, and myeloid/plasmacytoid dendritic cells were studied in relationship with HIV and TPV/LAPV status. The TPV detection/values coincided with higher plasma sCD14, FABP2, CCL20, MIF, CX3CL1, and triglyceride levels; lower Th17/Treg ratios; and classical monocyte expansion. Among HIV+, TPV+ versus TPV- exhibited lower Th17 frequencies, reduced Th17/Treg ratios, higher frequencies of non-classical CCR9lowHLADRhigh monocytes, and increased plasma fibrinogen levels. Finally, Th17/Treg ratios and non-classical CCR9lowHLADRhigh monocyte frequencies remained associated with TPV/LAPV after adjusting for FRS and HIV/ART duration in a logistic regression model. These findings point to Th17 paucity and non-classical monocyte abundance as novel immunological correlates of subclinical CAA that may fuel the CVD risk in ART-treated PLWH.

A Blood Immunological Signature of Subclinical Coronary Artery Atherosclerosis in People Living with HIV-1 Receiving Antiretroviral Therapy

Cardiovascular disease (CVD) remains an important co-morbidity in people living with HIV-1 (PLWH) receiving antiretroviral therapy (ART). Our previous studies performed on the Canadian HIV/Aging Cohort Study (CHACS) (>40 years-old; Framingham Risk Score (FRS) >5%), revealed a 2-3-fold increase in non-calcified coronary artery atherosclerosis (CAA) plaque burden, measured by Computed tomography angiography scan (CTAScan) as total (TPV) and low attenuated plaque volume (LAPV) in ART-treated PLWH (HIV+) versus uninfected controls (HIV-). In an effort to identify novel correlates of subclinical CAA, markers of intestinal damage (sCD14, LBP, FABP2); cell trafficking/inflammation (CCL20, CX3CL1, MIF, CCL25); subsets of Th17-polarized and regulatory (Tregs) CD4 + T-cells, classical/intermediate/non-classical monocytes, and myeloid/plasmacytoid dendritic cells, were studied in relationship with HIV and TPV/LAPV status. The TPV detection/values coincided with higher plasma sCD14, FABP2, CCL20, MIF, CX3CL1 and triglyceride levels, lower Th17/Treg ratios, and classical monocyte expansion. Among HIV + , TPV + versus TPV - exhibited lower Th17 frequencies, reduced Th17/Treg ratios, higher frequencies of non-classical CCR9 low HLADR high monocyte, and increased plasma fibrinogen levels. Finally, Th17/Treg ratios and non-classical CCR9 low HLADR high monocyte frequencies remained associated with TPV/LAPV after adjusting for FRS and HIV/ART duration in a logistic regression model. These findings point to Th17 paucity and non-classical monocyte abundance as novel immunological correlates of subclinical CAA that may fuel the CVD risk in ART-treated PLWH.

Association Between the Development of Subclinical Cardiovascular Disease and Human Immunodeficiency Virus (HIV) Reservoir Markers in People With HIV on Suppressive Antiretroviral Therapy

We report that people with human immunodeficiency virus (HIV) diagnosed with coronary artery atherosclerotic plaques display higher levels of HIV DNA compared with those without atherosclerotic plaques. In a multivariable prediction model that included 27 traditional and HIV-related risk factors, measures of HIV DNA were among the most important predictors of atherosclerotic plaque formation.

Oral vitamin D supplemental therapy to attain a desired serum 25-hydroxyvitamin D concentration in essential healthcare teams

BACKGROUND

The study objectives were to ascertain the efficacy of vitamin D supplementation in rapidly increasing serum vitamin D and of implementation of a hybrid (virtual and in-person) trial.

METHODS

In a randomized triple-blind controlled trial, healthcare workers were allocated to receive an oral bolus of 100,000 IU with 10,000 IU/week of vitamin D₃ or placebo. The co-primary outcomes were the change from baseline in serum 25-hydroxyvitamin D [(Δ) 25(OH)D] and proportion with vitamin D sufficiency (25(OH)D ≥ 75 nmol/L), at endpoint. Adherence to supplements and procedures as well as adverse event rates were documented.

RESULTS

Thirty-four (19 intervention, 15 control) subjects were randomized, with 28 (41%) virtual visits. After 44.78 ± 11.00 days from baseline, a significant adjusted group difference of 44.2 (34.7, 53.8) nmol/L was observed in the Δ 25(OH)D (95% CI) in favor of supplementation; 77.8% of intervention, and 13.3% of control, patients were vitamin D sufficient (OR:6.11, 95% CI:1.6, 22.9). The adherence to intervention was 94.7% in the intervention and 100% in the control groups. Irrespective of visit type, high adherence was observed in sampling procedures and completion of fortnightly online questionnaire. No adverse events attributable to vitamin D were reported.

CONCLUSION

The vitamin D supplementation rapidly and safely raised 25(OH)D levels to sufficient levels for a biological effect. Similarly high adherence to study procedures was observed with virtual and in-person participation.

TRIAL REGISTRATION

This trial was registered at https://clinicaltrials.gov on July 23, 2020 (# NCT04483635 ).

MiRNA-103 downmodulates CCR5 expression reducing HIV-1 entry and impacting latency establishment in CD4+ T cells

Activated-to-memory transitioning CD4⁺ T cells display elevated expression of the HIV-1 co-receptor CCR5 and are more prone to HIV-1 latent infection. Here, we show that p53-regulated miRNA-103 downmodulates CCR5 levels in CD4⁺ T lymphocytes. We reveal that miRNA-103 mimics, as well as Nutlin-3, an inhibitor of Mdm2-mediated p53 degradation, decrease CCR5-dependent HIV-1 infection. Using a dual-reporter virus, we subsequently validate that in transitioning CD4⁺ T cells, Nutlin-3 treatment decreases the frequency of both productively and latently infected cells via upregulation of miRNA-103. Importantly, we provide evidence that CD4⁺ T cells from HIV-1 elite controllers express less CCR5 than those from antiretroviral therapy-naïve progressors, an effect linked to a significant increase in miRNA-103 levels. By contributing to the control of CCR5 expression in CD4⁺ T cells, miRNA-103 is likely to play a key role in countering the establishment of latent HIV-1 reservoirs in vivo.

•

p53-regulated miRNA-103 reduces CCR5 in primary CD4⁺ T cells

•

HIV-1 latent infection-prone activated-to-memory transitioning T cells reduce p53

•

Stabilizing p53 reduces CCR5 in CD4⁺ T cells via upregulation of miRNA-103

•

Decreased CCR5 in CD4⁺ T cells is associated with an increase in miRNA-103 in vivo

Brief Report: Subclinical Carotid Artery Atherosclerosis Is Associated With Increased Expression of Peripheral Blood IL-32 Isoforms Among Women Living With HIV

BACKGROUND

Persistent inflammation in HIV infection is associated with elevated cardiovascular disease (CVD) risk, even with viral suppression. Identification of novel surrogate biomarkers can enhance CVD risk stratification and suggest novel therapies. We investigated the potential of interleukin 32 (IL-32), a proinflammatory multi-isoform cytokine, as a biomarker for subclinical carotid artery atherosclerosis in virologically suppressed women living with HIV (WLWH).

METHODS AND RESULTS

Nested within the Women's Interagency HIV Study, we conducted a cross-sectional comparison of IL-32 between 399 WLWH and 100 women without HIV, followed by a case-control study of 72 WLWH (36 carotid artery plaque cases vs. 36 age-matched controls without plaque). Plasma IL-32 protein was measured by ELISA, and mRNA of IL-32 isoforms (IL-32α, β, γ, D, ε, and θ) was quantified by reverse transcription polymerase chain reaction from peripheral blood mononuclear cells. Plasma IL-32 protein levels were higher in WLWH compared with women without HIV (P = 0.02). Among WLWH, although plasma IL-32 levels did not differ significantly between plaque cases and controls, expression of IL-32 isoforms α, β, and ε mRNA was significantly higher in peripheral blood mononuclear cells from cases (P = 0.01, P = 0.005, and P = 0.018, respectively). Upregulation of IL-32β and IL-32ε among WLWH with carotid artery plaque persisted after adjustment for age, race/ethnicity, smoking, systolic blood pressure, body mass index, and history of hepatitis C virus (P = 0.04 and P = 0.045); the adjusted association for IL-32α was marginally significant (P = 0.07).

CONCLUSIONS

IL-32 isoforms should be studied further as potential CVD biomarkers. This is of particular interest in WLWH by virtue of altered IL-32 levels in this population.

Overt IL-32 isoform expression at intestinal level during HIV-1 infection is negatively regulated by IL-17A

OBJECTIVES

Untreated HIV infection was previously associated with IL-32 overexpression in gut/intestinal epithelial cells (IEC). Here, we explored IL-32 isoform expression in the colon of people with HIV (PWH) receiving antiretroviral therapy (ART) and IL-32 triggers/modulators in IEC.

DESIGN

Sigmoid colon biopsies (SCB) and blood were collected from ART-treated PWH (HIV + ART; n = 17; mean age: 56 years; CD4+ cell counts: 679 cells/μl; time on ART: 72 months) and age-matched HIV-uninfected controls (HIVneg; n = 5). The IEC line HT-29 was used for mechanistic studies.

METHODS

Cells from SCB and blood were isolated by enzymatic digestion and/or gradient centrifugation. HT-29 cells were exposed to TLR1-9 agonists, TNF-α, IL-17A and HIV. IL-32α/β/γ/D/ε/θ and IL-17A mRNA levels were quantified by real-time RT-PCR. IL-32 protein levels were quantified by ELISA.

RESULTS

IL-32β/γ/ε isoform transcripts were detectable in the blood and SCB, with IL-32β mRNA levels being predominantly expressed in both compartments and at significantly higher levels in HIV + ART compared to HIVneg. IL-17A transcripts were only detectable in SCB, with increased IL-17A levels in HIVneg compared with HIV + ART and negatively correlated with IL-32β mRNA levels. IL-32β/γ/ε isoform mRNA were detected in HT-29 cells upon exposure to TNF-α, Poly I:C (TLR3 agonist), Flagellin (TLR-5 agonist) and HIV. IL-17A significantly decreased both IL-32 β/γ/ε mRNA and cell-associated IL-32 protein levels induced upon TNF-α and Poly I:C triggering.

CONCLUSION

We document IL-32 isoforms abundant in the colon of ART-treated PWH and reveal the capacity of the Th17 hallmark cytokine IL-17A to attenuate IL-32 overexpression in a model of inflamed IEC.

Loss of CD96 Expression as a Marker of HIV-Specific CD8+ T-Cell Differentiation and Dysfunction

Persistent immune activation and inflammation in people living with HIV (PLWH) are associated with immunosenescence, premature aging and increased risk of non-AIDS comorbidities, with the underlying mechanisms not fully understood. In this study, we show that downregulation of the T-cell immunoglobulin receptor CD96 on CD8⁺ T cells from PLWH is associated with decreased expression of the co-stimulatory receptors CD27 and CD28, higher expression of the senescence marker CD57 and accumulation of a terminally differentiated T-cell memory phenotype. In addition, we show that CD96-low CD8⁺ T-cells display lower proliferative potential compared to their CD96-high counterparts and that loss of CD96 expression by HIV-specific CD8⁺ T-cells is associated with a suboptimal response to HIV antigens. In conclusion, our results suggest that CD96 marks CD8⁺ T-cells with competent responses to HIV and the loss of its expression might be used as a biomarker for CD8⁺ T-cell senescence and dysfunction in PLWH.

Upregulated IL-32 Expression And Reduced Gut Short Chain Fatty Acid Caproic Acid in People Living With HIV With Subclinical Atherosclerosis

Despite the success of antiretroviral therapy (ART), people living with HIV (PLWH) are still at higher risk for cardiovascular diseases (CVDs) that are mediated by chronic inflammation. Identification of novel inflammatory mediators with the inherent potential to be used as CVD biomarkers and also as therapeutic targets is critically needed for better risk stratification and disease management in PLWH. Here, we investigated the expression and potential role of the multi-isoform proinflammatory cytokine IL-32 in subclinical atherosclerosis in PLWH (n=49 with subclinical atherosclerosis and n=30 without) and HIV- controls (n=25 with subclinical atherosclerosis and n=24 without). While expression of all tested IL-32 isoforms (α, β, γ, D, ϵ, and θ) was significantly higher in peripheral blood from PLWH compared to HIV- controls, IL-32D and IL-32θ isoforms were further upregulated in HIV+ individuals with coronary artery atherosclerosis compared to their counterparts without. Upregulation of these two isoforms was associated with increased plasma levels of IL-18 and IL-1β and downregulation of the atheroprotective protein TRAIL, which together composed a unique atherosclerotic inflammatory signature specific for PLWH compared to HIV- controls. Logistic regression analysis demonstrated that modulation of these inflammatory variables was independent of age, smoking, and statin treatment. Furthermore, our in vitro functional data linked IL-32 to macrophage activation and production of IL-18 and downregulation of TRAIL, a mechanism previously shown to be associated with impaired cholesterol metabolism and atherosclerosis. Finally, increased expression of IL-32 isoforms in PLWH with subclinical atherosclerosis was associated with altered gut microbiome (increased pathogenic bacteria; Rothia and Eggerthella species) and lower abundance of the gut metabolite short-chain fatty acid (SCFA) caproic acid, measured in fecal samples from the study participants. Importantly, caproic acid diminished the production of IL-32, IL-18, and IL-1β in human PBMCs in response to bacterial LPS stimulation. In conclusion, our studies identified an HIV-specific atherosclerotic inflammatory signature including specific IL-32 isoforms, which is regulated by the SCFA caproic acid and that may lead to new potential therapies to prevent CVD in ART-treated PLWH.

A Short-Term Assessment of Nascent HIV-1 Transmission Clusters Among Newly Diagnosed Individuals Using Envelope Sequence-Based Phylogenetic Analyses

The identification of transmission clusters (TCs) of HIV-1 using phylogenetic analyses can provide insights into viral transmission network and help improve prevention strategies. We compared the use of partial HIV-1 envelope fragment of 1,070 bp with its loop 3 (108 bp) to determine its utility in inferring HIV-1 transmission clustering. Serum samples of recently (n = 106) and chronically (n = 156) HIV-1-infected patients with status confirmed were sequenced. HIV-1 envelope nucleotide-based phylogenetic analyses were used to infer HIV-1 TCs. Those were constructed using ClusterPickerGUI_1.2.3 considering a pairwise genetic distance of ≤10% threshold. Logistic regression analyses were used to examine the relationship between the demographic factors that were likely associated with HIV-1 clustering. Ninety-eight distinct consensus envelope sequences were subjected to phylogenetic analyses. Using a partial envelope fragment sequence, 42 sequences were grouped into 15 distinct small TCs while the V3 loop reproduces 10 clusters. The agreement between the partial envelope and the V3 loop fragments was significantly moderate with a Cohen's kappa (κ) coefficient of 0.59, p < .00001. The mean age (<38.8 years) and HIV-1 B subtype are two factors identified that were significantly associated with HIV-1 transmission clustering in the cohort, odds ratio (OR) = 0.25, 95% confidence interval (CI, 0.04–0.66), p = .002 and OR: 0.17, 95% CI (0.10–0.61), p = .011, respectively. The present study confirms that a partial fragment of the HIV-1 envelope sequence is a better predictor of transmission clustering. However, the loop 3 segment may be useful in screening purposes and may be more amenable to integration in surveillance programs.

HIV-1 envelope sequence-based diversity measures for identifying recent infections

Identifying recent HIV-1 infections is crucial for monitoring HIV-1 incidence and optimizing public health prevention efforts. To identify recent HIV-1 infections, we evaluated and compared the performance of 4 sequence-based diversity measures including percent diversity, percent complexity, Shannon entropy and number of haplotypes targeting 13 genetic segments within the env gene of HIV-1. A total of 597 diagnostic samples obtained in 2013 and 2015 from recently and chronically HIV-1 infected individuals were selected. From the selected samples, 249 (134 from recent versus 115 from chronic infections) env coding regions, including V1-C5 of gp120 and the gp41 ectodomain of HIV-1, were successfully amplified and sequenced by next generation sequencing (NGS) using the Illumina MiSeq platform. The ability of the four sequence-based diversity measures to correctly identify recent HIV infections was evaluated using the frequency distribution curves, median and interquartile range and area under the curve (AUC) of the receiver operating characteristic (ROC). Comparing the median and interquartile range and evaluating the frequency distribution curves associated with the 4 sequence-based diversity measures, we observed that the percent diversity, number of haplotypes and Shannon entropy demonstrated significant potential to discriminate recent from chronic infections (p<0.0001). Using the AUC of ROC analysis, only the Shannon entropy measure within three HIV-1 env segments could accurately identify recent infections at a satisfactory level. The env segments were gp120 C2_1 (AUC = 0.806), gp120 C2_3 (AUC = 0.805) and gp120 V3 (AUC = 0.812). Our results clearly indicate that the Shannon entropy measure represents a useful tool for predicting HIV-1 infection recency.

The Canadian HIV and aging cohort study - determinants of increased risk of cardio-vascular diseases in HIV-infected individuals: rationale and study protocol

Background

With potent antiretroviral drugs, HIV infection is becoming a chronic disease. Emergence of comorbidities, particularly cardiovascular disease (CVD) has become a leading concern for patients living with the infection. We hypothesized that the chronic and persistent inflammation and immune activation associated with HIV disease leads to accelerated aging, characterized by CVD. This will translate into higher incidence rates of CVD in HIV infected participants, when compared to HIV negative participants, after adjustment for traditional CVD risk factors. When characterized further using cardiovascular imaging, biomarkers, immunological and genetic profiles, CVD associated with HIV will show different characteristics compared to CVD in HIV-negative individuals.

Methods/design

The Canadian HIV and Aging cohort is a prospective, controlled cohort study funded by the Canadian Institutes of Health Research. It will recruit patients living with HIV who are aged 40 years or older or have lived with HIV for 15 years or more. A control population, frequency matched for age, sex, and smoking status, will be recruited from the general population. Patients will attend study visits at baseline, year 1, 2, 5 and 8. At each study visit, data on complete medical and pharmaceutical history will be captured, along with anthropometric measures, a complete physical examination, routine blood tests and electrocardiogram. Consenting participants will also contribute blood samples to a research biobank. The primary outcome is incidence of a composite of: myocardial infarction, coronary revascularization, stroke, hospitalization for angina or congestive heart failure, revascularization or amputation for peripheral artery disease, or cardiovascular death. Preplanned secondary outcomes are all-cause mortality, incidence of the metabolic syndrome, incidence of type 2 diabetes, incidence of renal failure, incidence of abnormal bone mineral density and body fat distribution. Patients participating to the cohort will be eligible to be enrolled in four pre-planned sub-studies of cardiovascular imaging, glucose metabolism, immunological and genetic risk profile.

Discussion

The Canadian HIV and Aging Cohort will provide insights on pathophysiological pathways leading to premature CVD for patients living with HIV.

Electronic supplementary material

The online version of this article (10.1186/s12879-017-2692-2) contains supplementary material, which is available to authorized users.

Identification of novel HIV-1 dependency factors in primary CCR4(+)CCR6(+)Th17 cells via a genome-wide transcriptional approach

BACKGROUND

The HIV-1 infection is characterized by profound CD4(+) T cell destruction and a marked Th17 dysfunction at the mucosal level. Viral suppressive antiretroviral therapy restores Th1 but not Th17 cells. Although several key HIV dependency factors (HDF) were identified in the past years via genome-wide siRNA screens in cell lines, molecular determinants of HIV permissiveness in primary Th17 cells remain to be elucidated.

RESULTS

In an effort to orient Th17-targeted reconstitution strategies, we investigated molecular mechanisms of HIV permissiveness in Th17 cells. Genome-wide transcriptional profiling in memory CD4(+) T-cell subsets enriched in cells exhibiting Th17 (CCR4(+)CCR6(+)), Th1 (CXCR3(+)CCR6(-)), Th2 (CCR4(+)CCR6(-)), and Th1Th17 (CXCR3(+)CCR6(+)) features revealed remarkable transcriptional differences between Th17 and Th1 subsets. The HIV-DNA integration was superior in Th17 versus Th1 upon exposure to both wild-type and VSV-G-pseudotyped HIV; this indicates that post-entry mechanisms contribute to viral replication in Th17. Transcripts significantly enriched in Th17 versus Th1 were previously associated with the regulation of TCR signaling (ZAP-70, Lck, and CD96) and Th17 polarization (RORγt, ARNTL, PTPN13, and RUNX1). A meta-analysis using the NCBI HIV Interaction Database revealed a set of Th17-specific HIV dependency factors (HDFs): PARG, PAK2, KLF2, ITGB7, PTEN, ATG16L1, Alix/AIP1/PDCD6IP, LGALS3, JAK1, TRIM8, MALT1, FOXO3, ARNTL/BMAL1, ABCB1/MDR1, TNFSF13B/BAFF, and CDKN1B. Functional studies demonstrated an increased ability of Th17 versus Th1 cells to respond to TCR triggering in terms of NF-κB nuclear translocation/DNA-binding activity and proliferation. Finally, RNA interference studies identified MAP3K4 and PTPN13 as two novel Th17-specific HDFs.

CONCLUSIONS

The transcriptional program of Th17 cells includes molecules regulating HIV replication at multiple post-entry steps that may represent potential targets for novel therapies aimed at protecting Th17 cells from infection and subsequent depletion in HIV-infected subjects.

Diagnostic accuracy of algorithms to identify hepatitis C status, AIDS status, alcohol consumption and illicit drug use among patients living with HIV in an administrative healthcare database

PURPOSE

This study aims to develop and evaluate diagnostic algorithms for AIDS, hepatitis C status, alcohol abuse and illicit drug use in the administrative healthcare database of the Province of Quebec, Canada (Régie de l'assurance-maladie du Québec (RAMQ)).

METHODS

We selected HIV-positive patients contributing to both the RAMQ database and a local clinical database, which was used as gold standard. We developed algorithms to identify the diagnoses of interest in RAMQ using data from hospital discharge summaries and medical and pharmaceutical claims databases. We estimated and compared sensitivity, specificity, positive predictive and negative predictive values and area under receiver operating curve for each algorithm.

RESULTS

Four hundred twenty patients contributed to both databases. Prevalence of conditions of interest in the clinical database was as follows: AIDS 233 (55%), hepatitis C infection 105 (25%), alcohol abuse 106 (25%), illicit drug use 144 (34%) and intravenous drug use 107 (25%). Sensitivity to detect AIDS, hepatitis C, alcohol abuse, illicit drug use and intravenous drug use was 46% [95%CI: 39-53], 26% [18-35], 50% [37-57], 64% [55-72] and 70% [61-79], respectively. Specificity to detect these conditions was 91% [86-95], 97% [94-98], 92% [88-95], 95% [92-97] and 90% [87-93], respectively. Positive predictive values were 87% [80-92], 71% [54-85], 68% [56-78], 87% [79-93] and 72% [62-80], respectively. Area under receiver operating curve varied from 0.62 [0.57-0.65] for hepatitis C to 0.80 [0.76-0.85] for intravenous drug use.

CONCLUSIONS

Sensitivity was low to detect AIDS, alcohol abuse, illicit drug use and especially hepatitis C in RAMQ. Researchers must be aware of the potential for residual confounding and must consider additional methods to control for confounding.

Hepatitis C virus genotype 7, a new genotype originating from central Africa

We report a new hepatitis C virus (HCV) genotype identified in patients originating from the Democratic Republic of Congo. The prototype QC69 virus is shown to be a new lineage distinct from genotypes 1 to 6. Three additional patients were also found to be infected by a virus from this lineage, confirming its circulation in humans. We propose that these viruses be classified into HCV genotype 7.

Cost effectiveness of 'on demand' HIV pre-exposure prophylaxis for non-injection drug-using men who have sex with men in Canada

BACKGROUND

Recent trials report the efficacy of continuous tenofovir-based pre-exposure prophylaxis (PrEP) for prevention of HIV infection. The cost effectiveness of 'on demand' PrEP for non-injection drug-using men who have sex with men at high risk of HIV acquisition has not been evaluated.

OBJECTIVE

To conduct an economic evaluation of the societal costs of HIV in Canada and evaluate the potential benefits of this PrEP strategy.

METHODS

Direct HIV costs comprised outpatient, inpatient and emergency department costs, psychosocial costs and antiretroviral costs. Resource consumption estimates were derived from the Centre Hospitalier de l'Université de Montréal HIV cohort. Estimates of indirect costs included employment rate and work absenteeism. Costs for 'on demand' PrEP were modelled after an ongoing clinical trial. Cost-effectiveness analysis compared costs of 'on demand' PrEP to prevent one infection with lifetime costs of one HIV infection. Benefits were presented in terms of life-years and quality-adjusted life-years.

RESULTS

The average annual direct cost of one HIV infection was $16,109 in the least expensive antiretroviral regimen scenario and $24,056 in the most expensive scenario. The total indirect cost was $11,550 per year. Total costs for the first year of HIV infection ranged from $27,410 to $35,358. Undiscounted lifetime costs ranged from $1,439,984 ($662,295 discounted at 3% and $448,901 at 5%) to $1,482,502 ($690,075 at 3% and $485,806 at 5%). The annual cost of PrEP was $12,001 per participant, and $621,390 per infection prevented. The PrEP strategy was cost-saving in all scenarios for undiscounted and 3% discounting rates. At 5% discounting rates, the strategy is largely cost-effective: according to least and most expensive scenarios, incremental cost-effectiveness ratios ranged from $60,311 to $47,407 per quality-adjusted life-year.

CONCLUSION

This 'on demand' PrEP strategy ranges from cost-saving to largely cost-effective. The authors believe it represents an important public health strategy for the prevention of HIV transmission.

Performance of a clonal-based HIV-1 tropism phenotypic assay

Adequate determination of HIV-1 tropism is important in clinical and research settings. Genotypic and phenotypic approaches to evaluate tropism have been described. Phenotypic assays are widely used to determine HIV-1 tropism because of their sensitivity to detect minor CXCR4-using variants (X4). However they cannot differentiate mixed quasi-species of R5 and X4 viruses from dual-tropic viruses. We describe here a clonal-based HIV-1 tropism phenotypic assay. Env-pseudo-typed viruses were produced by co-transfection of the env expression plasmid pcDNA3.1/V5HisTOPO and a backbone vector pNL4-3.Luc.E-R- that expresses the entire HIV-1 genome except for env and vpr in 293T cell cultures. Co-receptor use was tested by infecting U87.CD4.CCR5+ and U87.CD4.CXCR4+ cells in the presence or absence of co-receptor inhibitors, using 10 clones from each sample. The ability of the assay to detect minor variants in a viral population was assessed by mixing X4 and R5 clones using different ratios. Both R5 and X4 minority variants were detected when present at greater than 0.4% in a mixture of envelope populations. This assay can be useful in both clinical and research laboratories.

Mutations in variable domains of the HIV-1 envelope gene can have a significant impact on maraviroc and vicriviroc resistance

Background

Resistance to CCR5 inhibitors, such as maraviroc and vicriviroc is characterized by reduction of maximal percent inhibition which indicates the use of an inhibitor-bound conformation of CCR5 for human immunodeficiency virus-1(HIV-1) entry. It is accompanied by substitutions in gp120 and gp41. Variable domain 3 (V3) plays the most important role, but substitutions outside V3 could also be involved in phenotype resistance. In this work, we investigated how mutations in variable regions of the viral envelope protein gp120 can contribute to CCR5 inhibitor resistance.

Methods

Resistant isolates were selected by passaging CC1/85 and BaL viruses with sub-inhibitory MVC and VCV concentrations. Mutations in gp160 were identified and mutants containing V2 (V169M), V3 (L317W) and V4 (I408T) were constructed.

Results

MVC and VCV susceptibility and viral tropism were assessed by single cycle assay. Mutant I408T showed 4-fold change (FC) increase in the half maximal inhibitory concentration (IC₅₀) to MVC, followed by L317W (1.52-FC), V169M (1.23-FC), V169M/I408T (4-FC) L317W/I408T (3-FC), V169M/L317W (1.30-FC), and V169M/L317W/I408T (3.31-FC). MPI reduction was observed for mutants I408T (85%), L317W (95%), V169M/I408T (84%), L317W/I408T (85%) and V169M/L317W/I408T (83%). For VCV, I408T increased the IC₅₀ by 2-FC and few mutants showed MPI reduction less than 95%: I408T (94%), L317W/I408T (94%) and V169M/L317W/I408T (94%). All mutants remained R5-tropic and presented decreased infectivity.

Conclusions

These results suggest that mutations in the V4 loop of HIV-1 may contribute to MVC and VCV resistance alone or combined with mutations in V2 and V3 loops.

Short communication: antibody responses to human immunodeficiency virus envelope from infections with multiple subtypes utilize the 1F7-idiotypic repertoire

A common idiotype of anti-HIV antibodies (Abs), designated as 1F7, was recently observed on anti-HIV broadly neutralizing Abs (BnAbs). The presence of the 1F7-idiotype on BnAbs suggests that continuous selection of 1F7-idiotypic Abs may allow these clones to achieve the somatic hypermutation necessary for broad neutralization. As the selection of type-specific BnAbs occurs in the setting of infections with a wide array of HIV subtypes, we investigated Abs from subjects infected with diverse subtypes for the selection of 1F7-idiotypic Abs. We observed the 1F7-idiotype on antiviral Abs in infections with various HIV subtypes. Furthermore, gp140-specific 1F7-idiotypic Abs recognized the gp140 antigens from several HIV subtypes. These results demonstrate that the 1F7-idiotype is a common characteristic of Abs from infections with diverse HIV subtypes, and suggests that early cross-reactivity of 1F7-idiotypic clones may act in conjunction with somatic hypermutation to produce BnAbs.

Design and implementation of a randomized crossover study of valproic acid and antiretroviral therapy to reduce the HIV reservoir

BACKGROUND

HIV reservoirs represent the major obstacles for eradication and are defined as a cell type that allows persistence of replication-competent HIV in patients on optimal long-term antiretroviral therapy (HAART). Several pilot clinical trials have been implemented to assess the value of experimental therapy to reduce reservoir size or eradicate HIV. In order to eradicate HIV, valproic acid was used as a new strategy to increase viral gene expression in the nucleus of infected cells with the expectation of generating a direct cell death or destruction by nearby cytotoxic cells. Previous pilot studies using VPA have showed conflicting results on the ability of VPA to reduce the size of HIV reservoirs.

PURPOSE

As the role of VPA on HIV reservoirs remains unclear, we conducted a multicenter clinical trial with a specific study design to obtain optimal information on reservoir changes while exposing the smallest number of individuals to the experimental medication.

METHOD

To this aim, a randomized, crossover design with 2 different treatment durations was implemented. By doubling the therapeutic period in one study arm, we were in a position to assess the impact of an extended duration of VPA on the size of the HIV reservoir and to evaluate the duration of treatment effects upon VPA withdrawal in the other arm. However, limitations for this type of study design included the logistical complexity of 2 uneven study arms and longer study duration.

CONCLUSION

Despite the absence of demonstrable impact of VPA on reservoir size, such crossover study design should be considered in the early stage testing of novel HIV therapeutics targeted to reduce reservoir size or eradicate HIV.

Antiviral drug resistance and the need for development of new HIV-1 reverse transcriptase inhibitors

Highly active antiretroviral therapy (HAART) consists of a combination of drugs to achieve maximal virological response and reduce the potential for the emergence of antiviral resistance. Despite being the first antivirals described to be effective against HIV, reverse transcriptase inhibitors remain the cornerstone of HAART. There are two broad classes of reverse transcriptase inhibitor, the nucleoside reverse transcriptase inhibitors (NRTIs) and nonnucleoside reverse transcriptase inhibitors (NNRTIs). Since the first such compounds were developed, viral resistance to them has inevitably been described; this necessitates the continuous development of novel compounds within each class. In this review, we consider the NRTIs and NNRTIs currently in both preclinical and clinical development or approved for second-line therapy and describe the patterns of resistance associated with their use as well as the underlying mechanisms that have been described. Due to reasons of both affordability and availability, some reverse transcriptase inhibitors with a low genetic barrier are more commonly used in resource-limited settings. Their use results in the emergence of specific patterns of antiviral resistance and so may require specific actions to preserve therapeutic options for patients in such settings.

Risk of spontaneous intracranial hemorrhage in HIV-infected individuals: a population-based cohort study

BACKGROUND

We studied the association between HIV infection, antiretroviral medications, and the risk of spontaneous intracranial hemorrhage.

METHODS

We performed a cohort and nested case control study in an administrative database. We selected all HIV-positive individuals presenting between 1985 and 2007. Each HIV-positive subject was matched with 4 HIV-negative individuals. We used a Poisson regression model to calculate rates of intracranial hemorrhage according to HIV status. We conducted a case -control study nested within the cohort of HIV-positive individuals to look at the effect of antiretroviral medications. Odds ratios for antiretroviral exposure were obtained using conditional logistic regression.

RESULTS

There were 7,053 HIV-positive and 27,681 HIV-negative subjects, representing 138,704 person-years. There were 49 incident intracranial hemorrhages, 29 in HIV-positive and 20 in HIV-negative individuals. The adjusted hazard ratio for intracranial hemorrhage in HIV-positive compared to HIV-negative patients was 3.28 (95% confidence interval [CI] 1.75-6.12). The effect was reduced to 1.99 (95% CI 0.92-4.31) in the absence of AIDS-defining conditions, and increased to 7.64 (95% CI 3.78-15.43) in subjects with AIDS-defining conditions. Hepatitis C infection, illicit drug or alcohol abuse, intracranial lesions, and coagulopathy were all strongly associated with intracranial hemorrhage (all P < .001). In the case control study, 29 cases of ICH in HIV-positive individuals were matched to 228 HIV-positive controls. None of the antiretroviral classes were associated with an increase in the odds ratio of intracranial hemorrhage.

CONCLUSIONS

The risk of intracranial hemorrhage in HIV-positive individuals seems to be mostly associated with AIDS-defining conditions, other comorbidities, or lifestyle factors. No association was found between use of antiretroviral medications and intracranial hemorrhage.

Valproic acid in association with highly active antiretroviral therapy for reducing systemic HIV-1 reservoirs: results from a multicentre randomized clinical study

OBJECTIVES

Conflicting results have been reported regarding the ability of valproic acid (VPA) to reduce the size of HIV reservoirs in patients receiving suppressive highly active antiretroviral therapy (HAART). In a randomized multicentre, cross-over study, we assessed whether adding VPA to stable HAART could potentially reduce the size of the latent viral reservoir in CD4 T cells of chronically infected patients.

METHODS

A total of 56 virologically suppressed patients were randomly assigned either to receive VPA plus HAART for 16 weeks followed by HAART alone for 32 weeks (arm 1; n  = 27) or to receive HAART alone for 16 weeks and then VPA plus HAART for 32 weeks (arm 2; n  = 29). VPA was administered at a dose of 500  mg twice a day (bid) and was adjusted to the therapeutic range. A quantitative culture assay was used to assess HIV reservoirs in CD4 T cells at baseline and at weeks 16 and 48.

RESULTS

No significant reductions in the frequency of CD4 T cells harbouring replication-competent HIV after 16 and 32 weeks of VPA therapy were observed. In arm 1, median (range) values of IU per log(10) billion (IUPB) cells were 2.55 (range 1.20-4.20), 1.80 (range 1.0-4.70) and 2.70 (range 1.0-3.90; P = 0.87) for baseline, week 16 and week 48, respectively. In arm 2, median values of IUPB were 2.55 (range 1.20-4.65), 1.64 (range 1.0-3.94) and 2.51 (range 1.0-4.48; P = 0.50) for baseline, week 16 and week 48, respectively.

CONCLUSIONS

Our study demonstrates that adding VPA to stable HAART does not reduce the latent HIV reservoir in virally suppressed patients.

Combating HIV resistance - focus on darunavir

Darunavir is a second-generation protease inhibitor designed to have antiviral efficacy against HIV-1 isolates harboring multiple resistance mutations to protease inhibitors. Pivotal trials conducted in treatment-experienced HIV-infected individuals have demonstrated significantly greater virological suppression when darunavir was added to an optimized background treatment compared with a control protease inhibitor. This virological suppression was associated with an increase in CD4 counts and was sustained over time. Darunavir resistance-associated mutations have been defined as V11I, V32I, L33F, I47V, I50V, I54L/M, G73S, L76V, I84V, and L89V. In clinical trials, baseline darunavir susceptibility was a strong predictor of virological response. Prior use of fosamprenavir was associated with darunavir resistance mutations. Darunavir has a high genetic barrier and has a distinct resistance profile. Although some cross-resistance exists with other second-generation protease inhibitors such as tipranavir, different resistance mutation patterns have been observed upon failure to these regimens. It was found that mutations at 47V, 54M, 85V, and 73T were most prevalent in isolates resistant to both PIs. Mutations 48V, 50V, and 54L were associated with resistance to darunavir but not to tipranavir. 82S and 82T were associated with resistance to tipranavir but not to darunavir. Therefore, darunavir provides potent virological efficacy as well as high genetic barrier that can be useful to preserve treatment options in HIV-infected, treatment-experienced individuals.

Immunogenicity and tolerability of an inactivated and adjuvanted pandemic H1N1 influenza vaccine, in HIV-1-infected patients

We evaluated the efficacy and tolerability of a single dose of the split virion AS03-adjuvanted pandemic H1N1 influenza vaccine (A/California/7/2009) in 84 HIV-1 infected individuals. Antibody titers were determined by hemagglutination inhibition assay and by microneutralization. Vaccine was well tolerated. At 21 days post vaccination, 56 (67%) patients had seroconverted. There was no correlation between baseline CD4 cell count (p=0.539) or HIV viral load (p=0.381) and immune response. Other vaccine strategies should be evaluated in this HIV population, to improve response rates.

Challenges in initiating antiretroviral therapy in 2010

Many clinical trials have shown that initiating antiretroviral therapy (ART) at higher rather than lower CD4 T cell-positive counts results in survival benefit. Early treatment can help prevent end-organ damage associated with HIV replication and can decrease infectivity. The mainstay of treatment is either a non-nucleoside reverse transcriptase inhibitor or a ritonavir-boosted protease inhibitor in combination with two nucleoside reverse transcriptase inhibitors. While effective at combating HIV, ART can produce adverse alterations of lipid parameters, with some studies suggesting a relationship between some anti-retroviral agents and cardiovascular disease. As the HIV-positive population ages, issues such as hypertension and diabetes must be taken into account when initiating ART. Adhering to ART can be difficult; however, nonoptimal adherence to ART can result in the development of resistance; thus, drug characteristics and the patient's preparedness to begin therapy must be considered. Reducing the pill burden through the use of fixed-dose antiretroviral drug combinations can facilitate adherence.

Characterization of drug Resistance in Antiretroviral-Treated Patients Infected with HIV-1 CRF02_AG and AGK Subtypes in Mali and Burkina Faso

Background

In a multicentred cohort of patients on antiretroviral therapy (ART) in Burkina Faso and Mali, we analysed the prevalence of HIV drug resistance mutations in patients failing a modified directly observed therapy (mDOT) protocol.

Methods

Patients on ART >6 months and with viral load (VL) >500 copies/ml were enrolled in a mDOT protocol. Genotypic resistance testing was performed on pre- and post-mDOT plasma samples of patients who still had VL >500 copies/ml after mDOT.

Results

Eight hundred and one patients from seven sites participated in the study. One hundred and thirteen patients (14.1%) had VL >500 copies/ml. Most patients were treated with lamivudine along with zidovudine or stavudine and efavirenz or nevirapine. Genotypes were available for 46 patients. The predominant HIV-1 subtypes were CRF02_AG in 26 (56.5%) and AGK/K/AK in 12 (26.1%) patients. The prevalence of drug resistance mutations by class were as follows for nucleoside reverse transcriptase inhibitors: 184I/V (82.6%), 215Y/F (32.6%), 219E/Q (19.6%), 70R (19.6%), 67N (21.7%), 41L (15.2%) and 151M(2.2%). For non-nucleoside reverse transcriptase inhibitors the prevalence was: 103N (50%) and 181C/I (19.6%). Phylogenetic analysis showed that, although the genetic distances were small among isolates, there was no clustering of a particular subtype in a specific region and that the high prevalence of AGK subtype in our drug-resistant population was not due to a circulating resistant strain.

Conclusion

Although CRF02_AG is the dominant clade in the Burkina Faso/Mali region, isolates with subtype K reverse transcriptase were frequent in our cohort. Drug resistance mutation pathways in subtype K reverse transcriptase need to be further evaluated in a larger cohort of non-B HIV-infected individuals.

Characterization of drug resistance in antiretroviral-treated patients infected with HIV-1 CRF02_AG and AGK subtypes in Mali and Burkina Faso

BACKGROUND

In a multicentred cohort of patients on antiretroviral therapy (ART) in Burkina Faso and Mali, we analysed the prevalence of HIV drug resistance mutations in patients failing a modified directly observed therapy (mDOT) protocol.

METHODS

Patients on ART >6 months and with viral load (VL) >500 copies/ml were enrolled in a mDOT protocol. Genotypic resistance testing was performed on pre- and post-mDOT plasma samples of patients who still had VL >500 copies/ml after mDOT.

RESULTS

Eight hundred and one patients from seven sites participated in the study. One hundred and thirteen patients (14.1%) had VL >500 copies/ml. Most patients were treated with lamivudine along with zidovudine or stavudine and efavirenz or nevirapine. Genotypes were available for 46 patients. The predominant HIV-1 subtypes were CRFO2_AG in 26 (56.5%) and AGK/K/AK in 12 (26.1%) patients. The prevalence of drug resistance mutations by class were as follows for nucleoside reverse transcriptase inhibitors: 1841/V (82.6%), 215Y/F (32.6%), 219E/Q (19.6%), 70R (19.6%), 67N (21.7%), 41L (15.2%) and 151M(2.2%). For non-nucleoside reverse transcriptase inhibitors the prevalence was: 103N (50%) and 181C/I (19.6%). Phylogenetic analysis showed that, although the genetic distances were small among isolates, there was no clustering of a particular subtype in a specific region and that the high prevalence of AGK subtype in our drug-resistant population was not due to a circulating resistant strain.

CONCLUSION

Although CRFO2_AG is the dominant clade in the Burkina Faso/Mali region, isolates with subtype K reverse transcriptase were frequent in our cohort. Drug resistance mutation pathways in subtype K reverse transcriptase need to be further evaluated in a larger cohort of non-B HIV-infected individuals.

TAK-220, a novel small-molecule CCR5 antagonist, has favorable anti-human immunodeficiency virus interactions with other antiretrovirals in vitro

TAK-220 is a CCR5 antagonist, part of the new class of anti-human immunodeficiency virus type 1 (anti-HIV-1) entry inhibitors. We evaluated the anti-HIV-1 interactions between TAK-220 and various antiretrovirals in vitro. Synergy was observed with all drugs at the 90 and 95% inhibitory concentrations. The favorable drug interactions observed suggest that further clinical evaluation is warranted.

Factors associated with a decrease in the prevalence of drug resistance in newly HIV-1 infected individuals in Montreal

OBJECTIVE

A decrease in the prevalence of drug resistance (DR) has been observed among recently infected (RI) individuals in Montreal. A study of chronically infected (CI) patients, who represent potential HIV-1 transmitters, was carried out in order to ascertain biological factors associated with this trend change.

DESIGN AND METHODS

Retrospective analysis of CI patients was performed for the period 1996-2003. Changes in mean viral load and DR prevalence were assessed in CI patients (n = 2328) and compared to those in RI patients (n = 180) living in the same geographic area.

RESULTS

A decrease was observed in the prevalence of DR among RI patients, from 13.0% in 1997-2000 to 4.0% in 2001-2003 (P = 0.04). From 1996 to 2000, the mean viral load in the CI patients decreased by 1.34 log10, to remain steady thereafter. The proportion of CI patients who interrupt treatment increased steadily over 1997-2003 from 3.1% to 16.5% (P < 0.0001). Since 1999, when genotyping analysis became available, we have observed a 0.9 log10 decrease in mean viral load among 602 genotyped CI patients harbouring any major mutations.

CONCLUSION

The decrease in transmission of DR documented in Montreal since 2000 coincides with the drop in mean viral load observed in CI patients. Factors that contribute to the decrease in viral load include routine access to genotyping and availability of more potent antiretroviral drugs. Plasma viral load seems to represent the main predictor for the transmission of DR.

Favorable interactions between enfuvirtide and 1-beta-D-2,6-diaminopurine dioxolane in vitro

We evaluated the in vitro anti-human immunodeficiency virus type 1 (HIV-1) interactions between 1-beta-D-2,6-diaminopurine dioxolane (DAPD) and enfuvirtide (T-20) against clinical isolates sensitive and resistant to reverse transcriptase and protease inhibitors. Interactions between T-20 and DAPD were synergistic to nearly additive, with combination index values ranging from 0.53 to 1.06 at 95% inhibitory concentrations. These studies suggest that a combination of T-20 and DAPD might be useful in the treatment of antiretroviral drug-experienced patients.

Anti-human immunodeficiency virus interactions of SCH-C (SCH 351125), a CCR5 antagonist, with other antiretroviral agents in vitro

SCH-C (SCH 351125) is a small-molecule antagonist of the human immunodeficiency virus type 1(HIV-1) coreceptor CCR5. It has in vitro activity against R5 viruses with 50% inhibitory concentrations ranging from 1.0 to 30.9 nM. We have studied anti-HIV-1 interactions of SCH-C with other antiretroviral agents in vitro. Synergistic interactions were seen with nucleoside reverse transcriptase inhibitors (zidovudine and lamivudine), nonnucleoside reverse transcriptase inhibitors (efavirenz), and protease inhibitors (indinavir) at all inhibitory concentrations evaluated. We have also studied antiviral interactions between the HIV-1 fusion inhibitor T-20 and SCH-C against a panel of R5 HIV-1 isolates. We found synergistic interactions against all the viruses tested, some of which harbored resistance mutations to reverse transcriptase and protease inhibitors. Anti-HIV-1 synergy was also observed between SCH-C and another R5 virus inhibitor, aminooxypentane-RANTES. These findings suggest that SCH-C may be a useful anti-HIV drug in combination regimens and that a combination of chemokine coreceptor/fusion inhibitors may be useful in the treatment of multidrug-resistant viruses.

Marked differences in quantity of infectious human immunodeficiency virus type 1 detected in persons with controlled plasma viremia by a simple enhanced culture method

Culture of autologous CD4 lymphocytes from peripheral blood mononuclear cells compared favorably with two other methods for the measurement of cell-associated human immunodeficiency virus type 1 (HIV-1). For subjects with undetectable HIV-1 RNA levels in plasma, there was a 10,000-fold range of cell-associated virus detected. This method provides a simple and reproducible means for monitoring cell-associated HIV-1.

Strong in vitro synergy between the fusion inhibitor T-20 and the CXCR4 blocker AMD-3100

Attachment and entry of HIV-1 into CD4 cells involve a series of events in which different viral envelope proteins interact with specific cell receptors, culminating in fusion of viral and cell membranes. AMD-3100 is a small molecule inhibitor of HIV-1 attachment to the CXCR4 chemokine receptor, and T-20 is a synthetic peptide corresponding to a region of HIV-1 gp41 that blocks fusion to cell membranes. To evaluate the interaction between agents acting at two different steps of the entry process, we conducted in vitro studies of the combination of T-20 and AMD-3100 against an X4 HIV-1 isolate. Single drugs or multiply diluted fixed ratio combinations of drugs were added to peripheral blood mononuclear cells infected with a clinical isolate, 14aPre. Drug interactions were evaluated using the median-effect principle and the combination index technique. The 50% inhibitory concentration (IC50) for T-20 was 0.10 microg/ml and for AMD-3100 was 0.19 microg/ml. Synergy was observed between T-20 and AMD-3100 and this increased with higher inhibitory concentrations, with combination indices ranging from 0.62 at IC50 to 0.02 at IC95. Whether these synergistic interactions translate into clinical benefit will need to be addressed in the context of clinical trials.