Impaired uptake of apoptotic cells into tingible body macrophages in germinal centers of patients with systemic lupus erythematosus

OBJECTIVE: To investigate the fate of apoptotic cells in the germinal centers (GCs) of patients with systemic lupus erythematosus (SLE). METHODS: Lymph node biopsy specimens obtained from 7 SLE patients with benign follicular hyperplasia, 5 non-SLE patients with benign follicular hyperplasia (non-SLE), 5 patients with malignant follicular lymphoma, and 3 patients with dermatopathic lymphadenitis were stained with monoclonal antibodies against macrophages (CD68) and follicular dendritic cells (CR2/CD21). TUNEL staining and transmission electron microscopy were performed to detect apoptotic cells. Confocal microscopy was used to evaluate the in vivo capacity of tingible body macrophages to remove apoptotic cell material. RESULTS: In a subgroup of patients with SLE, apoptotic cells accumulated in the GCs of the lymph nodes. The number of tingible body macrophages, which usually contained engulfed apoptotic nuclei, was significantly reduced in these patients. In contrast to what was observed in all controls, TUNEL-positive apoptotic material from SLE patients was observed to be directly associated with the surfaces of follicular dendritic cells (FDCs). CONCLUSION: Our findings suggest that in a sub-group of SLE patients, apoptotic cells are not properly cleared by tingible body macrophages of the GCs. Consequently, nuclear autoantigens bind to FDCs and may thus provide survival signals for autoreactive B cells. This action may override an important control mechanism for B cell development, resulting in the loss of tolerance for nuclear antigens.     

Development of resistance in wild-type and hypermutable Pseudomonas aeruginosa strains exposed to clinical pharmacokinetic profiles of meropenem and ceftazidime simulated in vitro

In this study we investigated the interplay of antibiotic pharmacokinetic profiles and the development of mutation-mediated resistance in wild-type and hypermutable Pseudomonas aeruginosa strains. We used in vitro models simulating profiles of the commonly used therapeutic drugs meropenem and ceftazidime, two agents with high levels of antipseudomonal activity said to have different potentials for stimulating resistance development. During ceftazidime treatment of the wild-type strain (PAO1), fully resistant mutants overproducing AmpC were selected rapidly and they completely replaced wild-type cells in the population. During treatment with meropenem, mutants of PAO1 were not selected as rapidly and showed only intermediate resistance due to the loss of OprD. These mutants also replaced the parent strain in the population. During the treatment of the mutator P. aeruginosa strain with meropenem, the slowly selected mutants did not accumulate several resistance mechanisms but only lost OprD and did not completely replace the parent strain in the population. Our results indicate that the commonly used dosing regimens for meropenem and ceftazidime cannot avoid the selection of mutants of wild-type and hypermutable P. aeruginosa strains. For the treatment outcome, including the prevention of resistance development, it would be beneficial for the antibiotic concentration to remain above the mutant prevention concentration for a longer period of time than it does in present regimens.     

Trajectories of PrEP use among men who have sex with men: a pooled analysis of two prospective,observational cohort studies

Introduction

Daily and event-driven oral pre-exposure prophylaxis (PrEP) reduce the risk of HIV acquisition. PrEP use can vary over time, yet little is known about the trajectories of PrEP use irrespective of the chosen PrEP regimens among men who have sex with men (MSM).

Methods

Using data from a mobile, web-based diary application collected daily from 17 August 2015 until 6 May 2018, we analysed PrEP use and sexual behaviour in two large cohorts, AMPrEP (Amsterdam, the Netherlands) and Be-PrEP-ared (Antwerp, Belgium). In both cohorts, participants could choose between daily and event-driven oral PrEP every 3 months. We used group-based trajectory modelling to identify trajectories of PrEP use over time and their determinants. In addition, we estimated the incidence rate of chlamydia, gonorrhoea and syphilis within these trajectories.

Results

We included 516 MSM (n = 322 AMPrEP; n = 194 Be-PrEP-ared), of whom 24% chose event-driven PrEP at PrEP initiation. Participants contributed 225,015 days of follow-up (median = 508 days [IQR = 429−511]). Four distinct PrEP use trajectories were identified: ≤2 tablets per week (“low frequency,” 12% of the total population), 4 tablets per week (“variable,” 17%), “almost daily” (31%) and “always daily” (41%). Compared to participants with “low frequency” PrEP use, participants with “variable” (odds ratio [OR] = 2.18, 95% confidence interval [CI] = 1.04−4.60) and “almost daily” PrEP use were more often AMPrEP participants (OR = 2.64, 95% CI = 1.27−5.49). “Almost daily” PrEP users were more often employed (OR = 6.76, 95% CI = 2.10−21.75) and were younger compared to participants with “low frequency” PrEP use. In addition, the number of days on which anal sex occurred was lower among participants with “low frequency” PrEP use compared to the other groups (all p<0.001). Compared to “low frequency” PrEP users, the incidence rates of chlamydia and gonorrhoea were higher for participants with “almost daily” and “always daily” PrEP use.

Conclusions

We uncovered four distinct PrEP use trajectories, pointing to different patterns of PrEP use in practice beyond the two-regimen dichotomy. These trajectories were related to sexual behaviour and rates of sexually transmitted infection. Tailoring PrEP care according to different PrEP use patterns could be an important strategy to improve efficient PrEP delivery.