Variable processing and cross-presentation of HIV by dendritic cells and macrophages shapes CTL immunodominance and immune escape.

Dendritic cells (DCs) and macrophages (Møs) internalize and process exogenous HIV-derived antigens for cross-presentation by MHC-I to cytotoxic CD8⁺ T cells (CTL). However, how degradation patterns of HIV antigens in the cross-presentation pathways affect immunodominance and immune escape is poorly defined. Here, we studied the processing and cross-presentation of dominant and subdominant HIV-1 Gag-derived epitopes and HLA-restricted mutants by monocyte-derived DCs and Møs. The cross-presentation of HIV proteins by both DCs and Møs led to higher CTL responses specific for immunodominant epitopes. The low CTL responses to subdominant epitopes were increased by pretreatment of target cells with peptidase inhibitors, suggestive of higher intracellular degradation of the corresponding peptides. Using DC and Mø cell extracts as a source of cytosolic, endosomal or lysosomal proteases to degrade long HIV peptides, we identified by mass spectrometry cell-specific and compartment-specific degradation patterns, which favored the production of peptides containing immunodominant epitopes in all compartments. The intracellular stability of optimal HIV-1 epitopes prior to loading onto MHC was highly variable and sequence-dependent in all compartments, and followed CTL hierarchy with immunodominant epitopes presenting higher stability rates. Common HLA-associated mutations in a dominant epitope appearing during acute HIV infection modified the degradation patterns of long HIV peptides, reduced intracellular stability and epitope production in cross-presentation-competent cell compartments, showing that impaired epitope production in the cross-presentation pathway contributes to immune escape. These findings highlight the contribution of degradation patterns in the cross-presentation pathway to HIV immunodominance and provide the first demonstration of immune escape affecting epitope cross-presentation.

Different antigen-processing activities in dendritic cells, macrophages, and monocytes lead to uneven production of HIV epitopes and affect CTL recognition.

Dendritic cells (DCs), macrophages (MPs), and monocytes are permissive to HIV. Whether they similarly process and present HIV epitopes to HIV-specific CD8 T cells is unknown despite the critical role of peptide processing and presentation for recognition and clearance of infected cells. Cytosolic peptidases degrade endogenous proteins originating from self or pathogens, exogenous Ags preprocessed in endolysosomes, thus shaping the peptidome available for endoplasmic reticulum translocation, trimming, and MHC-I presentation. In this study, we compared the capacity of DCs, MPs, and monocyte cytosolic extracts to produce epitope precursors and epitopes. We showed differences in the proteolytic activities and expression levels of cytosolic proteases between monocyte-derived DCs and MPs and upon maturation with LPS, R848, and CL097, with mature MPs having the highest activities. Using cytosol as a source of proteases to degrade epitope-containing HIV peptides, we showed by mass spectrometry that the degradation patterns of long peptides and the kinetics and amount of antigenic peptides produced differed among DCs, MPs, and monocytes. Additionally, variable intracellular stability of HIV peptides prior to loading onto MHC may accentuate the differences in epitope availability for presentation by MHC-I between these subsets. Differences in peptide degradation led to 2- to 25-fold differences in the CTL responses elicited by the degradation peptides generated in DCs, MPs, and monocytes. Differences in Ag-processing activities between these subsets might lead to variations in the timing and efficiency of recognition of HIV-infected cells by CTLs and contribute to the unequal capacity of HIV-specific CTLs to control viral load.

HIV pre-exposure prophylaxis: assessment of acceptability among members of HIV serodiscordant/serostatus unknown couples.

BACKGROUND: Pre-exposure prophylaxis (PrEP) is effective in preventing HIV infection but is not yet widely available in resource-limited settings such as the Dominican Republic. We aimed to ascertain PrEP acceptability among people living with HIV in the Dominican Republic who are part of HIV serodiscordant partnerships and understand relationships between PrEP acceptability, HIV stigma, and intimate partner violence.Methods: A cross-sectional survey of people in care for HIV infection included acceptability-related questions and assessments of HIV stigma and intimate partner violence. We also explored the expected impact of PrEP on HIV disclosure rates and fertility intentions.Results: Of the 100 participants, 74% had been in their current partnership for >1 year; 38% had not disclosed to their partner; 29% reported condomless sex, and 23% reported sex with multiple partners. PrEP was highly acceptable with 84% of participants saying they were "very likely" to offer PrEP to their partner if available and 21% stating it would allow them to have more children. Of those who had not disclosed to their partner, 71% stated PrEP would help them do so. No relationship was found between PrEP acceptability, HIV stigma, and intimate partner violence. However, higher than expected rates of PrEP acceptability limited the power of these analyses.Conclusion: Pre-exposure prophylaxis was considered to be highly acceptable among people living with HIV in the Dominican Republic who are part of serodiscordant partnerships.

Design and implementation of an interactive, competency-based pilot pediatric telemedicine curriculum.

During the height of the COVID-19 pandemic, telemedicine visits surged to increase access and maintain continuity of care, while reducing transmission of disease. However, few curricula exist for training residents on how to care for patients via telemedicine, especially in pediatrics. We aimed to create and evaluate an interactive, competency-based pilot curriculum, to meet the urgent need to train residents in telemedicine. The curriculum was developed in 2020 and includes a didactic, cased-based discussions, and direct observation exercise. A model for precepting residents, adhering to new ACGME guidelines, was also created to further engage residents in telemedicine in the outpatient general pediatrics settings. To evaluate the curriculum, we assessed feasibility of a direct observation to provide feedback and we conducted pre and post surveys to assess for changes in residents' self-reported skills in performing telemedicine visits following implementation of the curriculum. 16 residents participated in the curriculum and 15 completed both the pre and post surveys (93%). Residents' self-reported efficacy in performing key components of telemedicine visits, including completion of telemedicine visit (p = 0.023), initiation of visits (p = 0.01), and documentation (p = 0.001) all improved significantly following implementation. Residents' perception of patient satisfaction with telemedicine and personal perception of ease of use of the telemedicine system increased, though neither were statistically significant. Uptake of the direct observation exercise was nearly universal, with all but one resident having a direct observation completed during their ambulatory month. This novel, interactive telemedicine pilot curriculum for residents addresses ACGME competencies and provides residents with a toolkit for engaging in telemedicine.

Managing the COVID-19 Pandemic Using Quality Improvement Principles: A New York City Pediatric Primary Care Experience.

In the setting of COVID-19, pediatric primary care in New York City faced multiple challenges, requiring large-scale practice reorganization. We used quality improvement principles to implement changes to care delivery rapidly. METHODS: Plan-do-study-act cycles were used, based on primary drivers of consolidation, reorganization of in-person and urgent care, telehealth expansion, patient outreach, mental health linkages, team communication, and safety. RESULTS: The average visit volume in pediatrics decreased from 662 per week to 370. Telehealth visits increased from 2 to 140 per week, whereas urgent in-person visits decreased from 350 to 8 per week. Adolescent visits decreased from 57 to 46 per week. Newborn Clinic visits increased from 37 per week to 54. Show rates increased significantly for pediatrics and adolescent (P = 0.003 and P = 0.038, respectively). CONCLUSIONS: Quality improvement methodology allowed for the consolidation of pediatric primary care practices during the first wave of the COVID-19 pandemic, ensuring care for patients while prioritizing safety, evidence-based practices, and available resources.

Structure of the unbound form of HIV-1 subtype A protease: comparison with unbound forms of proteases from other HIV subtypes.

The crystal structure of the unbound form of HIV-1 subtype A protease (PR) has been determined to 1.7 A resolution and refined as a homodimer in the hexagonal space group P6(1) to an R(cryst) of 20.5%. The structure is similar in overall shape and fold to the previously determined subtype B, C and F PRs. The major differences lie in the conformation of the flap region. The flaps in the crystal structures of the unbound subtype B and C PRs, which were crystallized in tetragonal space groups, are either semi-open or wide open. In the present structure of subtype A PR the flaps are found in the closed position, a conformation that would be more anticipated in the structure of HIV protease complexed with an inhibitor. The amino-acid differences between the subtypes and their respective crystal space groups are discussed in terms of the differences in the flap conformations.