Immune reconstitution in HIV-1-infected children on antiretroviral therapy: role of thymic output and viral fitness

OBJECTIVE: To investigate the role of thymic output and viral fitness in immune reconstitution in HIV-1-infected children on antiretroviral therapy. METHODS: Thymic output was studied by measuring levels of T-cell receptor rearrangement excision circles (TREC) in peripheral blood lymphocytes, using a real-time quantitative PCR assay. Recombinant viruses containing pre-therapy or post-therapy HIV-1 protease domains were evaluated for viral infectivity in a quantitative single-cycle assay. RESULTS: Eighteen HIV-1-infected children who showed a significant increase in CD4 T-cell count after therapy were studied; HIV-1 plasma viraemia was substantially suppressed in 12 children (virological responders), but not in the other six (virological non-responders). TREC were quantified at baseline, and sequentially during the first 12 months of therapy. Both virological responders and non-responders showed an increase in TREC levels that was inversely correlated with baseline TREC and CD4 T cell counts. Changes in TREC positively correlated with CD4 T-cell count increases in virological responders, but not in non-responders; moreover, the ratios between TREC and CD4 T-cell count increases were higher in non-responders than in responders, suggesting a persistence of peripheral CD4 T-cell loss in the former. Drug-resistant viruses with reduced replicative capacity were documented in three out of six non-responders. CONCLUSIONS: These findings indicate that recovery of thymic function is a pivotal event in immune reconstitution, and suggest that CD4 T-cell increase despite persistent viraemia is sustained by a continuous thymic output that compensates peripheral CD4 T-cell depletion which might be slowed down by emerging viruses with reduced fitness.     

Detection of low avidity CD8(+) T cell populations with coreceptor-enhanced peptide-major histocompatibility complex class I tetramers

The development of soluble recombinant peptide-major histocompatibility complex class I (pMHCI) molecules conjugated in multimeric form to fluorescent labels has enabled the physical quantification and characterization of antigen-specific CD8(+) T cell populations by flow cytometry. Several factors determine the binding threshold that enables visualization of cognate CD8(+) T cells with these reagents; these include the affinity of the T cell receptor (TCR) for pMHCI antigen. Here, we show that multimers constructed from peptide-human leukocyte antigen (pHLA) A0201 monomers engineered in the heavy chain alpha2 domain to enhance CD8 binding (K(D) approximately 85 microM) without impacting the TCR binding platform can detect cognate CD8(+) T cells bearing low affinity TCRs that are not visible with the corresponding wildtype pHLA A0201 multimeric complexes. Mechanistically, this effect is mediated by a disproportionate enhancement of the TCR/pMHCI association rate. In direct ex vivo applications, these coreceptor-enhanced multimers exhibit faithful cognate binding properties; concomitant increases in background staining within the non-cognate CD8(+) T cell population can be resolved phenotypically using polychromatic flow cytometry as a mixture of na?ve and memory cells. These findings provide the first validation of a novel approach to the physical detection of low avidity antigen-specific CD8(+) T cell populations; such coreceptor-enhanced multimeric reagents are likely to be useful in a multitude of settings for the detection of auto-immune, tumor-specific and cross-reactive CD8(+) T cells.     

Angiographie par résonance magnétique avec produit de contraste

L'utilisation de produits de contraste paramagnétiques en angiographie par résonance magnétique a donné à cette technique la possibilité de s'opposer comme substitut à l'angiographie conventionnelle ou numérique. Cependant, en dé[it d'améliorations angiographiques spectaculaires, l'obtention de ces images nécessite une technique d'acquisition rigoureuse. Une concentration homogène et suffisante de produit de contraste est indispensable pendant l'acquisition des lignes centrales du plan de Fourier pour obtenir un rehaussement vasculaire de bonne qualité. De ce fait, la dose et le débit d'injection de produit de contraste doivent être sougneusement adaptés à l'acquisition pour produire des angiographies suffisamment concentrées par rapport aux tissus stationnaires avoisinants. La synchronisation de l'acquisition à l'injection est essentielle et plusieurs solutions ont été proposées, comme la détermination du temps d'arrivée du produit de contraste par bolus préalable, ou l'utilisation de séquences ultrarapides permettant de s'affranchir de cette information. Ces séquences ultrarapides, obtenues en six secondes environ et répétées plusieurs fois dans le temps, permettent de capter le produit de contraste lors de son premier passage, de même que la synchronisation automatisée de l'acquisition au-delà d'un certain seuil de signal dans le vaisseau, ce qui rapproche la technique d'angiographie par résonance magnétique de celle de la tomodensitométrie spiralée.     

Monitoring the response to primary medical therapy for breast cancer using three- dimensional time-resolved optical mammography

Primary medical therapy is used to reduce tumour size prior to surgery in women with locally advanced breast cancer. Optical tomography is a functional imaging technique using near- infrared light to produce three-dimensional breast images of tissue oxygen saturation and haemoglobin concentration. Its advantages include the ability to display quantitative physiological information, and to allow repeated scans without the hazards associated with exposure to ionising radiation. There is a need for a non-invasive functional imaging tool to evaluate response to treatment, so that non-responders can be given the opportunity to change their treatment regimen. Here, we evaluate the use of optical tomography for this purpose. Four women with newly diagnosed breast cancer who were about to undergo primary medical therapy gave informed and voluntary consent to take part in the study. Changes in physiological and optical properties within the tumour were evaluated during the course of neoadjuvant chemotherapy. Optical imaging was performed prior to treatment, after the first cycle of chemotherapy, halfway through, and on completion of chemotherapy. Images of light absorption and scatter at two wavelengths were produced, from which images of total haemoglobin concentration and oxygen saturation were derived. All patients that showed a good or complete response to treatment on MRI showed a corresponding recovery in the haemoglobin concentration images. Changes in mean tumour total haemoglobin concentration could be seen four weeks into treatment. The tumour oxygen saturation was low compared to background in three out of four patients, and also showed a return to baseline over treatment. Optical imaging of the breast is feasible during primary medical therapy and can be used to assess response to treatment over six months.     

Systematic review of radioguided versus wire-guided localization in the treatment of non-palpable breast cancers

One-third of breast cancers present as non-palpable lesions. The current gold standard treatment for these cancers is localized wide local excision using wire-guided localization (WGL). WGL has drawbacks including technical and scheduling issues resulting in the development of alternative radioguided techniques (RGL). A systematic review was performed to identify studies comparing RGL and WGL. The outcomes of surgical margin status, re-operation rates, surgical operative time, volume and excised specimen weight and successful sentinel lymph node biopsy (SLNB) rates were evaluated. Pooled odds ratios (ORs) and 95 % confidence intervals were estimated using fixed-effects analyses and random-effects analyses in case of statistically significant heterogeneity (p < 0.05). Seven randomized controlled trials (RCTs) matching the inclusion criteria were identified. The pooled ORs for involved surgical margin status were 0.78 (95 % CI, 0.52–1.17); for re-operations 0.74 (95 % CI, 0.49–1.11) and for successful SLNB 1.29 (95 % CI, 0.66–2.53). There was a significant difference in surgical operating time in favour of RGL (mean difference (MD), ?2.95; 95 % CI, ?4.43, ?1.47) and a significant difference in excised specimen volume, favouring WGL (MD, 6.79; 95 % CI, 0.03, 13.56). The MD for a specimen weight of ?3.00 (95 % CI, ?15.15, 9.15) showed no significant difference between RGL and WGL. RGL has a reduced operating time, but larger volume excisions compared to WGL. There is insufficient evidence to support the uptake of RGL over WGL, and larger, adequately powered, multi-centre RCTs are required.     

ROLL versus RSL: toss of a coin?

The safety and benefits of radio-guided localization (RGL) versus wire-guided localization (WGL) surgery in the treatment of non-palpable breast cancers have been confirmed through several meta-analyses. RGL has become the standard of care in several institutions, although overall uptake has been slow. In view of this evidence supporting RGL, we believe that the future discussion is not of RGL versus WGL, but rather of what form of RGL will constitute best practice of care going forward. We therefore discuss the case for radio-guided occult lesion localization versus radioactive seed localization in the treatment of non-palpable breast cancers, is it really a toss of a coin?     

What is the future of magnetic nanoparticles in the axillary management of breast cancer?

Magnetic nanoparticles (MNPs) possess unique properties, which make them highly attractive for medical applications. The use of MNPs in surgery has mainly been focused on their role in the identification of metastatic lymph node involvement. There have been developments within this field, including ongoing and newly conducted clinical trials. The current published evidence for the use of MNPs in assessing metastatic lymph node spread using sentinel lymph node biopsy and non-invasive imaging modalities is reviewed and future applications considered.