Impact of viral load and the duration of primary infection on HIV transmission

Abstract Objectives: HIV 'treatment as prevention' (TasP) describes early treatment of HIV-infected patients intended to reduce viral load and transmission. Crucial assumptions for estimating TasP's effectiveness are the underlying estimates of transmission risk. We aimed to determine transmission risk during primary infection, and of the relation of HIV transmission risk to viral load. Design: A systematic review and meta-analysis. Methods: We searched PubMed and Embase databases for studies that established a relationship between viral load and transmission risk, or primary infection and transmission risk, in serodiscordant couples. We analysed assumptions about the relationship between viral load and transmission risk, and between duration of primary infection and transmission risk. Results: We found 36 eligible articles, based on six different study populations. Studies consistently found that larger viral loads lead to higher HIV transmission rates, but assumptions about the shape of this increase varied from exponential increase to saturation. The assumed duration of primary infection ranged from 1.5 to 12 months; for each additional month, the log10 transmission rate ratio between primary and asymptomatic infection decreased by 0.40. Conclusion: Assumptions and estimates of the relationship between viral load and transmission risk, and the relationship between primary infection and transmission risk, vary substantially and predictions of TasP's effectiveness should take this uncertainty into account.

T cell lipid peroxidation induces ferroptosis and prevents immunity to infection

The selenoenzyme glutathione peroxidase 4 (Gpx4) is a major scavenger of phospholipid hydroperoxides. Although Gpx4 represents a key component of the reactive oxygen species-scavenging network, its relevance in the immune system is yet to be defined. Here, we investigated the importance of Gpx4 for physiological T cell responses by using T cell-specific Gpx4-deficient mice. Our results revealed that, despite normal thymic T cell development, CD8(+) T cells from T(ΔGpx4/ΔGpx4) mice had an intrinsic defect in maintaining homeostatic balance in the periphery. Moreover, both antigen-specific CD8(+) and CD4(+) T cells lacking Gpx4 failed to expand and to protect from acute lymphocytic choriomeningitis virus and Leishmania major parasite infections, which were rescued with diet supplementation of high dosage of vitamin E. Notably, depletion of the Gpx4 gene in the memory phase of viral infection did not affect T cell recall responses upon secondary infection. Ex vivo, Gpx4-deficient T cells rapidly accumulated membrane lipid peroxides and concomitantly underwent cell death driven by ferroptosis but not necroptosis. These studies unveil an essential role of Gpx4 for T cell immunity.

Rapid Sequestration of Leishmania mexicana by Neutrophils Contributes to the Development of Chronic Lesion.

The protozoan Leishmania mexicana parasite causes chronic non-healing cutaneous lesions in humans and mice with poor parasite control. The mechanisms preventing the development of a protective immune response against this parasite are unclear. Here we provide data demonstrating that parasite sequestration by neutrophils is responsible for disease progression in mice. Within hours of infection L. mexicana induced the local recruitment of neutrophils, which ingested parasites and formed extracellular traps without markedly impairing parasite survival. We further showed that the L. mexicana-induced recruitment of neutrophils impaired the early recruitment of dendritic cells at the site of infection as observed by intravital 2-photon microscopy and flow cytometry analysis. Indeed, infection of neutropenic Genista mice and of mice depleted of neutrophils at the onset of infection demonstrated a prominent role for neutrophils in this process. Furthermore, an increase in monocyte-derived dendritic cells was also observed in draining lymph nodes of neutropenic mice, correlating with subsequent increased frequency of IFNγ-secreting T helper cells, and better parasite control leading ultimately to complete healing of the lesion. Altogether, these findings show that L. mexicana exploits neutrophils to block the induction of a protective immune response and impairs the control of lesion development. Our data thus demonstrate an unanticipated negative role for these innate immune cells in host defense, suggesting that in certain forms of cutaneous leishmaniasis, regulating neutrophil recruitment could be a strategy to promote lesion healing.

Cytomegalovirus infection and disease reduce 10-year cardiac allograft vasculopathy-free survival in heart transplant recipients.

BACKGROUND Cytomegalovirus (CMV) is associated with an increased risk of cardiac allograft vasculopathy (CAV), the major limiting factor for long-term survival after heart transplantation (HTx). The purpose of this study was to evaluate the impact of CMV infection during long-term follow-up after HTx. METHODS A retrospective, single-centre study analyzed 226 HTx recipients (mean age 45 ± 13 years, 78 % men) who underwent transplantation between January 1988 and December 2000. The incidence and risk factors for CMV infection during the first year after transplantation were studied. Risk factors for CAV were included in an analyses of CAV-free survival within 10 years post-transplant. The effect of CMV infection on the grade of CAV was analyzed. RESULTS Survival to 10 years post-transplant was higher in patients with no CMV infection (69 %) compared with patients with CMV disease (55 %; p = 0.018) or asymptomatic CMV infection (54 %; p = 0.053). CAV-free survival time was higher in patients with no CMV infection (6.7 years; 95 % CI, 6.0-7.4) compared with CMV disease (4.2 years; CI, 3.2-5.2; p < 0.001) or asymptomatic CMV infection (5.4 years; CI, 4.3-6.4; p = 0.013). In univariate analysis, recipient age, donor age, coronary artery disease (CAD), asymptomatic CMV infection and CMV disease were significantly associated with CAV-free survival. In multivariate regression analysis, CMV disease, asymptomatic CMV infection, CAD and donor age remained independent predictors of CAV-free survival at 10 years post-transplant. CONCLUSIONS CAV-free survival was significantly reduced in patients with CMV disease and asymptomatic CMV infection compared to patients without CMV infection. These findings highlight the importance of close monitoring of CMV viral load and appropriate therapeutic strategies for preventing asymptomatic CMV infection.

Low correlation between self-report and medical record documentation of urinary tract infection symptoms.

BACKGROUND Correlations between symptom documentation in medical records and patient self-report (SR) vary depending on the condition studied. Patient symptoms are particularly important in urinary tract infection (UTI) diagnosis, and this correlation for UTI symptoms is currently unknown. METHODS This is a cross-sectional survey study in hospitalized patients with Escherichia coli bacteriuria. Patients were interviewed within 24 hours of diagnosis for the SR of UTI symptoms. We reviewed medical records for UTI symptoms documented by admitting or treating inpatient physicians (IPs), nurses (RNs), and emergency physicians (EPs). The level of agreement between groups was assessed using Cohen κ coefficient. RESULTS Out of 43 patients, 34 (79%) self-reported at least 1 of 6 primary symptoms. The most common self-reported symptoms were urinary frequency (53.5%); retention (41.9%); flank pain, suprapubic pain, and fatigue (37.2% each); and dysuria (30.2%). Correlation between SR and medical record documentation was slight to fair (κ, 0.06-0.4 between SR and IPs and 0.09-0.5 between SR and EDs). Positive agreement was highest for dysuria and frequency. CONCLUSION Correlation between self-reported UTI symptoms and health care providers' documentation was low to fair. Because medical records are a vital source of information for clinicians and researchers and symptom assessment and documentation are vital in distinguishing UTI from asymptomatic bacteriuria, efforts must be made to improve documentation.

Overtreatment of asymptomatic bacteriuria: a qualitative study

BACKGROUND Overtreatment of asymptomatic bacteriuria (ASB) is widespread and may result in antibiotic side-effects, excess costs to the healthcare system, and may potentially trigger antimicrobial resistance. According to international management guidelines, ASB is not an indication for antibiotic treatment (with few exceptions). AIM To determine reasons for using antibiotics to treat ASB in the absence of a treatment indication. METHODS A qualitative study was conducted at a tertiary care hospital in Switzerland during 2011. We interviewed 21 internal medicine residents and attending physicians selected by purposive sampling, using a semi-structured questionnaire. Responses were analysed in an inductive thematic content approach using dedicated software (MAXQDA(®)). FINDINGS In the 21 interviews, the following thematic rationales for antibiotic overtreatment of ASB were reported (in order of reporting frequency): (i) treating laboratory findings without taking the clinical picture into account (N = 17); (ii) psychological factors such as anxiety, overcautiousness, or anticipated positive impact on patient outcomes (N = 13); (iii) external pressors such as institutional culture, peer pressure, patient expectation, and excessive workload that interferes with proper decision-making (N = 9); (iv) difficulty with interpreting clinical signs and symptoms (N = 8). CONCLUSION In this qualitative study we identified both physician-centred factors (e.g. overcautiousness) and external pressors (e.g. excessive workload) as motivators for prescribing unnecessary antibiotics. Also, we interpreted the frequently cited practice of treating asymptomatic patients based on laboratory findings alone as lack of awareness of evidence-based best practices.

An Arginine Deprivation Response Pathway Is Induced in Leishmania during Macrophage Invasion

Amino acid sensing is an intracellular function that supports nutrient homeostasis, largely through controlled release of amino acids from lysosomal pools. The intracellular pathogen Leishmania resides and proliferates within human macrophage phagolysosomes. Here we describe a new pathway in Leishmania that specifically senses the extracellular levels of arginine, an amino acid that is essential for the parasite. During infection, the macrophage arginine pool is depleted due to its use to produce metabolites (NO and polyamines) that constitute part of the host defense response and its suppression, respectively. We found that parasites respond to this shortage of arginine by up-regulating expression and activity of the Leishmania arginine transporter (LdAAP3), as well as several other transporters. Our analysis indicates the parasite monitors arginine levels in the environment rather than the intracellular pools. Phosphoproteomics and genetic analysis indicates that the arginine-deprivation response is mediated through a mitogen-activated protein kinase-2-dependent signaling cascade.