Paul MacPherson

Interleukin-7 receptor expression on CD8(+) T cells is reduced in HIV infection and partially restored with effective antiretroviral therapy.

Interleukin (IL)-7 enhances CD8 T-cell proliferation and cytolytic activity. The expression of its receptor, CD127 (IL-7R alpha), may therefore be important in the immunopathogenesis of HIV disease. CD127 expression on CD8(+) T cells from HIV seronegative controls, untreated HIV-seropositive patients, and HIV-positive patients receiving antiretroviral therapy with sustained viral suppression was analyzed by flow cytometry in a cross-sectional study. Among healthy controls, 65% of CD8 cells expressed CD127 ( n = 7). This dropped to 21.6% among untreated HIV-positive patients ( n = 16), and approached normal levels (47.7%) in HIV-positive individuals on effective therapy ( n = 20). The same pattern was observed for naïve (CD45RA(+) ) and memory (CD45RO(+) ) CD8(+) T cells but changes were more extreme within the memory cell population. Duration of viral suppression was the only parameter evaluated that correlated with extent of CD127 expression in treated patients. Impairment of CTL activity in HIV disease may be caused, in part, by downregulation of IL-7 receptor expression. Improved immune function with effective antiretroviral therapy is associated with recovery of this molecule. The correlation between virologic suppression and apparent CD127 recovery suggests that essential cytokine signaling pathways may be restored with sustained inhibition of viral replication.

Interleukin-7 receptor expression on CD8 T-cells is downregulated by the HIV Tat protein.

We have previously shown decreased expression of the interleukin (IL)-7 receptor α-chain (CD127) on CD8 T-cells in HIV-infected patients and an apparent recovery of this receptor in those receiving antiretroviral therapy with sustained viral suppression. Here, we demonstrate that the HIV Tat protein specifically downregulates cell surface expression of CD127 on human CD8 T-cells in a dose- and time-dependent manner. The effects of Tat on CD127 expression could be blocked with anti-Tat monoclonal antibodies or by preincubating Tat with heparin. Tat had no effect on the expression of other cell surface proteins examined, including CD132, or on cell viability over 72 hours. Further, CD127 expression was not altered by other HIV proteins, including gp160 or Nef. Preincubation of purified CD8 T-cells with Tat protein inhibited CD8 T-cell proliferation and perforin synthesis after stimulation with IL-7. Because IL-7 signaling is essential for optimal CD8 T-cell proliferation and function, the downregulation of CD127 and apparent inhibition of cytotoxic activity by Tat may play an important role in HIV-induced immune dysregulation and impaired cell-mediated immunity.

Soluble HIV Tat Protein Removes the IL-7 Receptor α-Chain from the Surface of Resting CD8 T Cells and Targets It for Degradation

IL-7 signaling is essential to CD8 T cell development, activation, and homeostasis. We have previously shown decreased expression of the IL-7R α-chain (CD127) on CD8 T cells in HIV+ patients and that this downregulation is mediated at least in part by the HIV Tat protein. We show in this study that CD127 has a prolonged t1/2 in resting CD8 T cells and continuously recycles on and off the cell membrane. We also demonstrate soluble Tat protein significantly decreases the t1/2 of CD127. Soluble Tat is taken up from the medium and accumulates in CD8 T cells with a peak of 6 h. Once inside the cell, Tat exits the endosomes during their normal acidification and enters the cytosol. Tat then translocates to the inner leaflet of the cell membrane, where it binds directly to the cytoplasmic tail of CD127, inducing receptor aggregation and internalization through a process dependent on microtubules. Tat appears to then target CD127 for degradation via the proteasome. By removing CD127 from the cell surface, the HIV Tat protein is thus able to reduce IL-7 signaling and impair CD8 T cell proliferation and function.

IL-7 downregulates IL-7Rα expression in human CD8 T cells by two independent mechanisms.

Interleukin (IL)‐7 is an essential nonredundant cytokine, and throughout the lifespan of a T‐cell signaling via the IL‐7 receptor influences cell survival, proliferation and differentiation. It is therefore no surprise that expression of the IL‐7 receptor alpha‐chain (CD127) is tightly regulated. We have previously shown that IL‐7 downregulates expression of CD127 at the cell surface and now elucidate the kinetics of that suppression and demonstrate that IL‐7 downregulates CD127 transcripts and surface protein in primary human CD8 T cells by two separate pathways. We show that IL‐7 induces the initial reduction in cell‐surface CD127 protein independent of transcriptional suppression, which is delayed by 40–60u2009min. Although IL‐7‐mediated downregulation of CD127 transcripts is dependent on Janus kinase (JAK)/STAT5, the early downregulation of surface CD127 protein is independent of JAK activity. The data further illustrate that low levels of IL‐7 induce smaller and transient decreases in CD127 transcripts and surface protein, whereas higher concentrations induce more profound and sustained suppression. Such flexibility in receptor expression likely allows for fine‐tuned immune responses in human CD8 T cells in different microenvironments and in response to different immunological challenges.

HIV knowledge among Canadian-born and sub-Saharan African-born patients living with HIV.

Research has revealed differences on scales measuring HIV knowledge between individuals from various ethnic backgrounds and cultures. Few studies have examined this knowledge with immigrant populations and persons living with HIV. This study examined HIV knowledge among persons living with HIV who were either born in Canada or in sub-Saharan Africa and, for comparison, in a sample of college students. All participants were residing in Canada. Participants completed questionnaires measuring demographic variables, sexual health behaviour, and HIV status, treatment, and knowledge. Canadian-born patients living with HIV were more likely to be older and male than the other groups. On average, patients living with HIV were diagnosed 6.4xa0years ago, and 80% reported having current or previous experience taking HIV medications. After adjusting for age and gender, significant differences were found between the groups on the Brief HIV Knowledge Questionnaire. Canadian-born persons living with HIV (nxa0=xa0110) scored higher than sub-Saharan African-born patients (nxa0=xa023) and college students (nxa0=xa081); mean percentage correct was 86, 70, and 62%, respectively (Pxa0<xa0.01). These results suggested that ongoing HIV education is needed for all groups, and that additional tailored and targeted educational interventions are needed to address important gaps in knowledge among persons living with HIV patients originating from Africa and among college students.

IL-7 induces clathrin-mediated endocytosis of CD127 and subsequent degradation by the proteasome in primary human CD8 T cells.

Interleukin‐7 (IL‐7), a key immunoregulatory cytokine, plays an essential role in peripheral T‐cell homeostasis and function. Signaling via the IL‐7 receptor is tightly regulated and we and others have shown IL‐7 provides negative feedback on its own signaling by downregulating expression of the IL‐7 receptor alpha‐chain (CD127) through both suppression of CD127 gene transcription and by internalization of existing CD127 proteins from the cell membrane. We show here for the first time in primary human CD8 T cells that upon stimulation with IL‐7, CD127 is internalized through clathrin‐coated pits, a process dependent on both lipid‐raft formation and the activity of dynamin. As visualized by confocal microscopy, CD127 shows increased co‐localization with clathrin within 5u2009min of IL‐7 stimulation and within 15–30u2009min is seen in multiple intracellular punctae co‐localizing with the early endosomal marker EEA1. By 2u2009h after addition of IL‐7, CD127 staining associates with the late endosomal marker RAB7 and with the proteasomal 20S subunit. By inducing receptor internalization and translocation from early endosomes to the proteasome, IL‐7 directly influences its receptor density on the cell surface and thus regulates the intensity of its own signaling cascades. Given the important role IL‐7 plays in T‐cell development, homeostasis and function, deciphering how expression of its receptor is controlled on the cell surface is essential in understanding how T‐cell activity can be regulated in different microenvironments and in response to different pathogens.

Pyrosequencing dried blood spots reveals differences in HIV drug resistance between treatment naïve and experienced patients.

Dried blood spots (DBS) are an alternative specimen collection format for HIV-1 genotyping. DBS produce HIV genotyping results that are robust and equivalent to plasma when using conventional sequencing methods. However, using tagged, pooled pyrosequencing, we demonstrate that concordance between plasma and DBS is not absolute and varies according to viral load (VL), duration of HIV infection and antiretroviral therapy (ART) status. The plasma/DBS concordance is the highest when VL is ≥5,000 copies/ml and/or the patient has no ART exposure and/or when the duration of HIV infection is ≤2 years. Stepwise regression analysis revealed that VL is most important independent predictor for concordance of DBS with plasma genotypes. This is the first study to use next generation sequencing to identify discordance between DBS and plasma genotypes. Consideration should be given to VL, duration of infection, and ART exposure when interpreting DBS genotypes produced using next generation sequencing. These findings are of particular significance when DBS are to be used for clinical monitoring purposes.

Canadian guideline on HIV pre-exposure prophylaxis and nonoccupational postexposure prophylaxis

KEY POINTSnNew HIV infections occur every year in Canada,[1][1] highlighting the need for integrated prevention programs. Pre-exposure prophylaxis (PrEP) and nonoccupational postexposure prophylaxis (nPEP) are two important strategies for preventing HIV that should be considered standard of care and

Overview of a gay men's STI/HIV testing clinic in Ottawa: Clinical operations and outcomes

OBJECTIVES: To 1) create a space where men who have sex with men (MSM) feel comfortable accessing sexually transmitted infection/human immunodeficiency virus (STI/HIV) testing, and 2) reduce STI/HIV incidence.PARTICIPANTS: Gay men in Ottawa and its surrounding regions.SETTING: A preponderance of diagnoses of sexually transmitted infections and HIV continue to occur among MSM. Meanwhile, other literature identifies that many MSM are reluctant to access STI/HIV testing services or to disclose their sexual practices to primary care practitioners.INTERVENTION: In Ottawa, in an effort to surmount these issues and decrease STI/HIV incidence among MSM, the local public health unit in collaboration with community partners created “GayZone”, a three-hour-per-week STI/HIV testing and STI treatment clinic for gay men. In this paper, we report on the uptake and STI/HIV diagnosis outcomes for this clinic from January 2010 through December 2013.OUTCOMES: GayZone is a well-utilized clinic that yields a number of STI/HIV diagnoses per year. Overall, the positivity rates of the STI/HIV tests at this clinic are above-average, although lower than what might be expected by local epidemiological data. While the results of this clinic validate anonymous HIV testing, they bring into question the utility of pharyngeal swabs to test for gonorrhea and chlamydia.CONCLUSION: The results of our study demonstrate the utility of a gay men’s STI/HIV testing clinic and highlight some areas for improvement. Public health practitioners, frontline clinicians, and community workers in other regions who wish to implement such an STI/HIV clinic would do well to consider our results beforehand.RésuméOBJECTIFS : 1) Offrir un endroit où les hommes ayant des relations sexuelles avec d’autres hommes (HARSAH) n’hésitent pas à se rendre pour obtenir des services de dépistage des infections transmises sexuellement (ITS) et du virus d’immunodéficience humaine (VIH); et 2) réduire l’incidence des ITS et du VIH.PARTICIPANTS : Hommes gais d’Ottawa et des environs.CONTEXTE : Alors même que les diagnostics d’ITS et de VIH demeurent nombreux pour les HARSAH, il y a différentes indications à l’effet que ces hommes sont réticents à recourir aux services de dépistage ou à divulguer leurs pratiques sexuelles aux pourvoyeurs de soins primaires.INTERVENTION : Dans le but de surmonter ces difficultés pour parvenir à diminuer la prévalence des ITS et du VIH chez les HARSAH, les services de santé publique de la ville d’Ottawa ont mis sur pied, en collaboration avec des partenaires communautaires, la Zone gaie, une clinique spécialisée où les hommes gais ont accès trois heures par semaine à des services de dépistage des ITS et du VIH et de traitement des ITS. Le présent rapport traite du taux de fréquentation de cette clinique et des diagnostics d’ITS et de VIH qui ont pu y être établis entre janvier 2010 et décembre 2013.RÉSULTATS : La Zone gaie est une clinique abondamment utilisée qui établit chaque année un bon nombre de diagnostics d’ITS et de VIH. La proportion de tests de dépistage positifs y est au-dessus de la moyenne, bien quinférieure à ce que lon pourrait attendre selon les données épidémiologiques locales. Le travail de la clinique a mis en lumière l’importance du dépistage anonyme du VIH, mais nous amène par ailleurs à nous interroger sur la pertinence des prélèvements pharyngés pour dépister la gonorrhée et la chlamydia.CONCLUSION : Non seulement les résultats obtenus témoignent-ils de l’utilité d’une clinique semblable, mais ils font également ressortir quelques points à améliorer. Les praticiens en santé publique, les cliniciens de première ligne et les travailleurs communautaires qui envisagent l’établissement d’une telle clinique spécialisée dans leur région seraient bien avisés de prendre d’abord connaissance des résultats de notre travail.

Overviewing a Nurse-Led, Community-Based HIV PEP Program: Applying the Extant Literature in Frontline Practice

This clinical concept paper overviews a program to facilitate access to postexposure prophylaxis (PEP) for gay, bisexual, and other men who have sex with men. The project, which was a collaborative initiative involving the local School of Nursing, public health unit, AIDS service organization, hospital-based HIV clinic, and an outpatient pharmacy, was implemented to circumvent common barriers to care identified in the literature. In this project, persons who present to one of the two participating clinics after having come, or likely having come, into contact with HIV within the previous 72xa0hr, are offered rapid HIV testing, also known as point-of-care (POC) testing, to rule out existing HIV infection, and provided with a follow-up appointment booked at the HIV clinic. Clients are also offered comprehensive STI testing, and HIV prevention counseling. The implementation of this collaborative community-based access-to-PEP project demonstrates the application of research to a real-world health care setting, and it is hoped that others will adapt this model to their local setting, enabling ease of access to PEP for members of groups that are disproportionately affected by HIV.