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The presence and reactivation of chronic viral infections such as Epstein-Barr virus (EBV), cytomegalovirus (CMV) and human immunodeficiency virus (HIV) have been proposed as potential contributors to Long COVID (LC), but studies in well-characterized post-acute cohorts of individuals with COVID-19 over a longer time course consistent with current case definitions of LC are limited.In a cohort of 280 adults with prior SARS-CoV-2 infection, we assessed the presence and types of LC symptoms and prior medical history (including COVID-19 history and HIV status), and performed serological testing for EBV and CMV using a commercial laboratory. We used covariate-adjusted binary logistic regression models to identify independent associations between variables and LC symptoms.We observed that LC symptoms such as fatigue and neurocognitive dysfunction at a median of 4months following initial diagnosis were independently associated with serological evidence suggesting recent EBV reactivation (early antigen-D [EA-D] IgG positivity) or high nuclear antigen (EBNA) IgG levels, but not with ongoing EBV viremia. Serological evidence suggesting recent EBV reactivation (EA-D IgG) was most strongly associated with fatigue (OR 2.12). Underlying HIV infection was also independently associated with neurocognitive LC (OR 2.5). Interestingly, participants who had serologic evidence of prior CMV infection were less likely to develop neurocognitive LC (OR 0.52).Overall, these findings suggest differential effects of chronic viral co-infections on the likelihood of developing LC and predicted distinct syndromic patterns. Further assessment during the acute phase of COVID-19 is warranted.Long-term Impact of Infection with Novel Coronavirus (LIINC); NCT04362150FUNDING. This work was supported by the National Institute of Allergy and Infectious Diseases NIH/NIAID 3R01AI141003-03S1 to TJ Henrich, R01AI158013 to M Gandhi and M Spinelli, K24AI145806 to P Hunt, and by the Zuckerberg San Francisco Hospital Department of Medicine and Division of HIV, Infectious Diseases, and Global Medicine. MJP is supported on K23 A137522 and received support from the UCSFBay Area Center for AIDS Research (P30-AI027763).

Background To mitigate increased risk of premature cardiovascular disease in antiretroviral therapy (ART) suppressed adults living with HIV (PWH), low-dose methotrexate (LDMTX) was evaluated in a multicenter randomized placebo controlled clinical trial of 176 PWH taking various ART regimens (ACTG A5314). Given shared methotrexate (MTX) and tenofovir (TFV) pharmacokinetic (PK) pathways, a substudy was conducted to investigate whether LDMTX alters TFV exposure. Methods Adults virally suppressed on ART for >24 weeks were randomized to LDMTX or placebo. The first 66 participants taking a tenofovir disoproxil fumarate-containing regimen underwent intensive PK sampling over 24 hours after the second dose of LDMTX 10 mg or placebo. TFV and MTX levels were quantified using validated mass spectrometry methods. TFV PK between LDMTX and placebo groups were compared and MTX PK was characterized. Results Forty-eight participants completed this substudy (n = 20 on LDMTX and 28 on placebo). Baseline characteristics were balanced except for protease inhibitor (PI)-use (25% in LDMTX and 43% in placebo groups). For TFV, AUC6 (primary endpoint), and AUC24,imputed, Cmax, and Cmin (secondary endpoints) were on average 22%, and 24%, 27%, and 31% less in the LDMTX versus placebo groups, with reductions in secondary endpoints reaching statistical significance. Additional analyses suggested a greater reduction in the absence of PI although not significant. Conclusion Lower TFV AUC24,imputed and Cmax indicates that LDMTX reduces TFV exposure in PWH. However, this change was modest, not warranting a change in TFV dosing at this time. Further studies of TFV PK with LDMTX, especially without PI co-administration, are warranted.

We report a patient with connective tissue disease who developed modest severe acute respiratory syndrome coronavirus 2 receptor binding domain–specific antibody levels and a lack of neutralization capacity, despite having received 3 mRNA coronavirus disease 2019 vaccines and holding anti-B-cell therapy for >7 months before vaccination. The patient developed virus-specific T-cell responses.

A major obstacle to achieving long-term antiretroviral (ART) free remission or functional cure of HIV infection is the presence of persistently infected cells that establish a long-lived viral reservoir. HIV largely resides in anatomical regions that are inaccessible to routine sampling, however, and non-invasive methods to understand the longitudinal tissue-wide burden of HIV persistence are urgently needed. Positron emission tomography (PET) imaging is a promising strategy to identify and characterize the tissue-wide burden of HIV. Here, we assess the efficacy of using immunoPET imaging to characterize HIV reservoirs and identify anatomical foci of persistent viral transcriptional activity using a radiolabeled HIV Env-specific broadly neutralizing antibody

Pharmacologic inhibition of the mammalian target of rapamycin (mTOR) in the setting of renal transplantation has previously been associated with lower human immunodeficiency virus 1 (HIV-1) DNA burden, and in vitro studies suggest that mTOR inhibition may lead to HIV transcriptional silencing. Because prospective clinical trials are lacking, we conducted an open-label, single-arm study to determine the impact of the broad mTOR inhibitor, everolimus, on residual HIV burden, transcriptional gene expression profiles, and immune responses in HIV-infected adult solid organ transplant (SOT) recipients on antiretroviral therapy. Whereas everolimus therapy did not have an overall effect on cell-associated HIV-1 DNA and RNA levels in the entire cohort, participants who maintained everolimus time-averaged trough levels >5ng/mL during the first 2months of therapy had significantly lower RNA levels up to 6months after the cessation of study drug. Time-averaged everolimus trough levels significantly correlated with greater inhibition of mTOR gene pathway transcriptional activity. Everolimus treatment also led to decreased PD-1 expression on certain T cell subsets. These data support the rationale for further study of the effects of mTOR inhibition on HIV transcriptional silencing in non-SOT populations, either alone or in combination with other strategies. Trial Registration: ClinicalTrials.gov NCT02429869.

A detailed understanding of long-term SARS-CoV-2-specific T cell responses and their relationship to humoral immunity and markers of inflammation in diverse groups of individuals representing the spectrum of COVID-19 illness and recovery is urgently needed. Data are also lacking as to whether and how adaptive immune and inflammatory responses differ in individuals that experience persistent symptomatic sequelae months following acute infection compared to those with complete, rapid recovery. We measured SARS-CoV-2-specific T cell responses, soluble markers of inflammation, and antibody levels and neutralization capacity longitudinally up to 9 months following infection in a diverse group of 70 individuals with PCR-confirmed SARS-CoV-2 infection. The participants had varying degrees of initial disease severity and were enrolled in the northern California Long-term Impact of Infection with Novel Coronavirus (LIINC) cohort. Adaptive T cell responses remained remarkably stable in all participants across disease severity during the entire study interval. Whereas the magnitude of the early CD4+ T cell immune response is determined by the severity of initial infection (participants requiring hospitalization or intensive care), pre-existing lung disease was significantly associated with higher long-term SARS-CoV2-specific CD8+ T cell responses, independent of initial disease severity or age. Neutralizing antibody levels were strongly correlated with SARS-CoV-2-specific CD4+ T but not CD8+ T cell responses. Importantly, we did not identify substantial differences in long-term virus-specific T cell or antibody responses between participants with and without COVID-19-related symptoms that persist months after initial infection.

We describe severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-specific T cell responses, soluble markers of inflammation, and antibody levels and neutralization capacity longitudinally in 70 individuals with PCR-confirmed SARS-CoV-2 infection. Participants represent a spectrum of illness and recovery, including some with persistent viral shedding in saliva and many experiencing post-acute sequelae of SARS-CoV-2 infection (PASC). T cell responses remain stable for up to 9 months. Whereas the magnitude of early CD4+ T cell immune responses correlates with severity of initial infection, pre-existing lung disease is independently associated with higher long-term SARS-CoV-2-specific CD8+ T cell responses. Among participants with PASC 4 months following coronavirus disease 2019 (COVID-19) symptom onset, we observe a lower frequency of CD8+ T cells expressing CD107a, a marker of degranulation, in response to Nucleocapsid (N) peptide pool stimulation, and a more rapid decline in the frequency of N-specific interferon-γ-producing CD8+ T cells. Neutralizing antibody levels strongly correlate with SARS-CoV-2-specific CD4+ T cell responses., Graphical abstract, CD4+ and CD8+ T cell responses following natural infection with COVID-19 are stable over 8 months. Individuals with PASC demonstrate a lower frequency of CD8+ T cells expressing CD107a, a marker of degranulation, and a more rapid decline in the frequency of N-specific interferon-γ-producing CD8+ T cells.

Tigecycline is highly active against various drug-resistant bacteria. The US Food and Drug Administration (FDA) recently issued a black box warning for tigecycline owing to an associated increase in all-cause mortality. Clinical breakpoints of antibiotics are vital in susceptibility testing of pathogens for the selection of antibiotic therapy; however, no consensus exists between different committees on the clinical breakpoints of tigecycline. Of note, tigecycline exhibits atypical non-linear plasma protein binding (PPB) behaviour, and the pivotal probability of target attainment (PTA) analysis for the determination of clinical breakpoints did not account for the PPB of tigecycline. In this work, the PTA analysis was performed with consideration of atypical non-linear PPB behaviour of tigecycline. A model describing atypical non-linear PPB was developed and validated. Monte Carlo simulations were performed to determine the target ratio of area under the free drug concentration-time curve to minimum inhibitory concentration (fAUC/MIC) for Escherichia coli and, subsequently, PTA analyses were performed. The target fAUC/MIC ratio for E. coli was determined as 2.05, whilst the target AUC/MIC ratio was 6.96. The PTA analyses suggest a lower clinical breakpoint of tigecycline against E. coli. This finding suggests that there is a need to revisit the current clinical breakpoints of tigecycline.

Background Linezolid (LZD) is bactericidal against Mycobacterium tuberculosis, but it has treatment-limiting toxicities. A better understanding of exposure-response relationships governing LZD efficacy and toxicity will inform dosing strategies. Because in vitro monotherapy studies yielded conflicting results, we explored LZD pharmacokinetic/pharmacodynamic (PK/PD) relationships in vivo against actively and nonactively multiplying bacteria, including in combination with pretomanid. Methods Linezolid multidose pharmacokinetics were modeled in mice. Dose-fractionation studies were performed in acute (net bacterial growth) and chronic (no net growth) infection models. In acute models, LZD was administered alone or with bacteriostatic or bactericidal pretomanid doses. Correlations between PK/PD parameters and lung colony-forming units (CFUs) and complete blood counts were assessed. Results Overall, time above minimum inhibitory concentration (T>MIC) correlated best with CFU decline. However, in growth-constrained models (ie, chronic infection, coadministration with pretomanid 50 mg/kg per day), area under the concentration-time curve over MIC (AUC/MIC) had similar explanatory power. Red blood cell counts correlated strongly with LZD minimum concentration (Cmin). Conclusions Although T>MIC was the most consistent correlate of efficacy, AUC/MIC was equally predictive when bacterial multiplication was constrained by host immunity or pretomanid. In effective combination regimens, administering the same total LZD dose less frequently may be equally effective and cause less Cmin-dependent toxicity., Linezolid is an efficacious TB drug that exhibits dose- and duration-dependent toxicity. Using animal models, we show that decreasing dosing frequency while maintaining the same total weekly dose may be a viable strategy to maintain efficacy while decreasing toxicity.

Nonlinear protein binding is traditionally thought of as an increasing fraction unbound with increasing total drug concentration. In the past several years, research into the protein binding of several tetracyclines has shown that an unexpected and counterintuitive phenomenon has been observed, specifically that of decreasing unbound drug fraction with increasing total concentrations of drug over certain concentration ranges. Although several studies of tigecycline have shown the importance calcium and its chelation may play in the protein-drug interaction, the potential clinical implications and relevance have not been explored. Here, we define typical and atypical nonlinear protein binding, overview protein binding theory, and discuss theoretical implications on pharmacokinetics. Using tigecycline as an example, in silico simulations and calculations show how when atypical nonlinear protein binding is not accounted for free drug exposure, and drug tissue penetration may be overestimated. It is important to revisit the impacts of nonlinearity in protein binding on clinical pharmacokinetics and pharmacodynamics, and ultimately, clinical efficacy. Although this phenomenon could potentially warrant clinical dose adjustment for certain compounds, it also presents a potential opportunity to exploit underlying mechanisms to develop new therapies and better understand molecular interactions of xenobiotics within the physiological system.

The lack of availability of novel antibiotic agents and the rise of resistance to existing therapies has led clinicians to utilise combination therapy to adequately treat bacterial infections. Here we examined how chelators may impact the in vitro activity of tigecycline (TIG) against Pseudomonas aeruginosa , Escherichia coli and Klebsiella pneumoniae . Minimum inhibitory concentrations (MICs) were determined by broth dilution with and without various combinations of chelators (EDTA and other tetracyclines) and metal ions (i.e. calcium, magnesium). Trimethoprim (TMP) was used as a non-chelating control. Addition of metal ions led to increases in MICs, whilst addition of EDTA led to decreases in MICs. The chelating effects of EDTA were reversed by addition of magnesium and most profoundly calcium. Similar effects of EDTA and calcium were observed for tetracycline (TET) and TMP. When other tetracyclines (TET, oxytetracycline (OXY) and chlortetracycline (CHL)) were used as chelators at concentrations below their MICs, TIG MICs decreased for P. aeruginosa but not for E. coli . Some decreases in TIG MICs were observed for K. pneumoniae when TET and CHL were added. A dose-dependent decrease in TIG MIC was observed for TET and was reversed by the addition of calcium. The presence of effects of EDTA and calcium on TMP MICs indicates that mechanisms outside of TIG chelation likely play a role in enhanced activity. Full characterisation of an unexpected interaction such as TIG–TET with different microorganisms could provide valuable insights into the underlying mechanisms and design of physiologically viable chelators as candidates for future combinations regimens.

Background: Plasma renin is an important regulator of blood pressure (BP). Plasma renin activity (PRA) has been shown to correlate with variability in BP response to antihypertensive agents. We conducted a genome-wide association study to identify single-nucleotide polymorphisms (SNPs) associated with baseline PRA using data from the PEAR study (Pharmacogenomic Evaluation of Antihypertensive Responses). Methods: Multiple linear regression analysis was performed in 461 whites and 297 blacks using an additive model, adjusting for age, sex, and ancestry-specific principal components. Top SNPs were prioritized by testing the expected direction of association for BP response to atenolol and hydrochlorothiazide. Top regions from the BP response prioritization were tested for functional evidence through differences in gene expression by genotype using RNA sequencing data. Regions with functional evidence were assessed for replication with baseline PRA in an independent study (PEAR-2). Results: Our top SNP rs3784921 was in the SNN-TXNDC11 gene region. The G allele of rs3784921 was associated with higher baseline PRA (β=0.47; P =2.09×10 −6 ) and smaller systolic BP reduction in response to hydrochlorothiazide (β=2.97; 1-sided P =0.006). In addition, TXNDC11 expression differed by rs3784921 genotype ( P =0.007), and rs1802409, a proxy SNP for rs3784921 ( r 2 =0.98–1.00), replicated in PEAR-2 (β=0.15; 1-sided P =0.038). Additional SNPs associated with baseline PRA that passed BP response prioritization were in/near the genes CHD9, XIRP2, and GHR. Conclusions: We identified multiple regions associated with baseline PRA that were prioritized through BP response signals to 2 mechanistically different antihypertensive drugs. Clinical Trial Registration: URL: https://www.clinicaltrials.gov . Unique identifier: NCT00246519.

Critically ill patients often present with a combination of disease states and comorbid conditions that progress over a clinical course. This can manifest in physiological changes, such as fluid shifts, alterations in protein binding, and acid-base balance issues, which may in turn alter a drug's distribution, potentially towards or away from its site of action. It's vital that these factors are examined for drugs used in critical illness in varying disease states, acute and chronic in nature. Several methods have been used to study the variations in target site penetration, but few provide a feasible option to reliably measure active drug concentrations at the site of action over time. This review examines these techniques, their merits and shortcomings, generally and as they relate to use in critically ill.

Adequate drug penetration to a site of infection is absolutely imperative to ensure sufficient antimicrobial treatment. Microdialysis is a minimally invasive, versatile technique, which can be used to study the penetration of an antiinfective agent in virtually any tissue of interest. It has been used to investigate drug distribution and pharmacokinetics in variable patient populations, as a tool in dose optimization, a potential utility in therapeutic drug management, and in the study of biomarkers of disease progression. While all of these applications have not been fully explored in the field of antiinfectives, this review provides an overview of how microdialysis has been applied in various phases of drug development, a focus on the specific applications in the subspecialties of infectious disease (treatment of bacterial, fungal, viral, parasitic, and mycobacterial infections), and developing applications (biomarkers and therapeutic drug management).

With resistance of S. aureus, the most prevalent identified pathogen in skin and soft tissue infections, on the rise, the need for safe, effective, and well-tolerated antibiotics is crucial. Ceftobiprole medocaril (BAL-5788), ceftobiprole's parenteral prodrug, is a bactericidal cephalosporin with broad Gram-positive and Gram-negative activity that has shown to be well-tolerated and noninferior to vancomycin and vancomycin plus ceftazidime in the treatment of MRSA complicated skin and skin structure infections (cSSSIs) in clinical trials. Areas Covered: This article overviews ceftobiprole medocaril's use for cSSSI, with specific focus on clinical efficacy and safety data in addition to summary information on its basic chemistry, microbiological profile, and pharmacokinetic/pharmacodynamic relationships supporting its use in cSSSIs. Information sources include peer-reviewed scientific literature, conference proceedings, publically available regulatory reports, as well as information from the drug sponsor's website. Expert Commentary: With increasing antibiotic resistance, safe, effective antibiotics agents are a welcome sight. There has been clinical evidence in support of using ceftobiprole for treatment of Gram-positive and -negative infections, including MRSA and susceptible P. aeruginosa. This broad antimicrobial activity might allow ceftobiprole to be an alternative to dual therapy combinations when potential drug toxicities, drug-drug or drug-disease interactions are concerns for other agents.

In typical nonlinear plasma protein binding (PPB) behavior, the free fraction increases with increasing total concentrations. In contrast, when a drug exhibits atypical nonlinear PPB behavior, the free fraction decreases with increasing total concentrations. Tigecycline, a novel glycylcycline, exhibits atypical nonlinear PPB behavior, but the mechanism of such behavior is currently unknown. Because tigecycline can form complexes with metal ions, an interaction between metal ion, tigecycline, and plasma proteins was hypothesized but not further investigated. The current work explores the role of metal ions in the atypical nonlinear PPB behavior of tigecycline and proposes a plausible mechanism of atypical nonlinear PPB behavior. The addition of ethylenediaminetetraacetic acid resulted in 10- to 30-fold higher unbound fractions, and the atypical behavior was nullified. The saturation of ethylenediaminetetraacetic acid chelation, by addition of excessive divalent metal ions, such as calcium and magnesium, led to the return of the atypical nonlinear PPB behavior. Different possible mechanisms were evaluated by simulation, and a plausible mechanism was proposed.