Effect of glycocalyx-targeted therapy on vascular function in older adults: a randomized controlled trial.

Advancing age increases cardiovascular disease risk, in part, because of impaired glycocalyx thickness and endothelial dysfunction. Glycocalyx-targeted therapies, such as Endocalyx Pro, could improve both glycocalyx thickness and endothelial function in older adults; however, this has yet to be tested. We hypothesized that Endocalyx Pro supplementation would increase glycocalyx thickness and endothelial function in older adults. Twenty-three older adults aged 66 ± 7 yr (52% female) were enrolled in a randomized, double-blind, placebo-controlled, parallel-arms study to investigate the effect of 12-wk Endocalyx Pro supplementation (3,712 mg/day) on glycocalyx thickness and endothelial function. Glycocalyx thickness was assessed using the GlycoCheck, and endothelial function was determined via brachial artery flow-mediated dilation (FMD). Between-group comparisons revealed Endocalyx Pro did not increase glycocalyx thickness in microvessels 4-25 µm (P = 0.33), 4-7 µm (P = 0.07), or 10-25 µm (P = 0.47) in diameter when compared with placebo. In addition, Endocalyx Pro did not significantly improve FMD [mean ratio (95%) confidence interval [CI]) for between-group comparisons, 1.16 (0.77-1.74); P = 0.48]. However, Endocalyx Pro improved FMD normalized to shear rate (SR) area under the curve [mean ratio (95% CI) for between-group comparisons, 2.41 (1.14,4.13); P = 0.001]. Moreover, Endocalyx Pro increased capillary glycocalyx thickness more than placebo in individuals not taking antihypertensive medication [mean difference (95% CI) for between-group comparison, -0.08 (-0.15, -0.01); P = 0.02]. Our pilot study suggests that Endocalyx Pro supplementation is feasible in older adults but has no measurable effect on overall glycocalyx thickness and FMD. However, Endocalyx Pro may have select effects on capillary glycocalyx thickness and FMD normalized to shear rate among older adults, but further investigation is warranted.NEW & NOTEWORTHY Endothelial glycocalyx thickness and vascular endothelial function decline with advancing age. Endocalyx Pro is a glycocalyx-targeted therapy that may improve endothelial glycocalyx thickness and vascular endothelial function in older adults. This study demonstrated that 12-wk Endocalyx Pro supplementation did not improve overall endothelial glycocalyx thickness or flow-mediated dilation in older adults; however, Endocalyx Pro did increase capillary glycocalyx thickness in individuals not taking antihypertensive medication and improve flow-mediated dilation normalized to the shear stimulus.

A role for adverse childhood experiences and depression in preeclampsia.

Introduction: Adverse childhood experiences (ACEs) are a measure of childhood adversity and are associated with life-long morbidity. The impacts of ACEs on peripartum health including preeclampsia, a common and dangerous hypertensive disorder of pregnancy, remain unclear, however. Therefore, we aimed to determine ACE association with peripartum psychiatric health and prevalence of preeclampsia using a case-control design. Methods: Clinical data were aggregated and validated using a large, intergenerational knowledgebase developed at our institution. Depression symptoms were measured by standard clinical screeners: the Patient Health Questionnaire-9 (PHQ-9) and the Edinburgh Postnatal Depression Scale (EPDS). ACEs were assessed via survey. Scores were compared between participants with (N = 32) and without (N = 46) prior preeclampsia. Results: Participants with ACE scores ≥4 had significantly greater odds of preeclampsia than those with scores ≤ 3 (adjusted odds ratio = 6.71, 95% confidence interval:1.13-40.00; p = 0.037). Subsequent speculative analyses revealed that increased odds of preeclampsia may be driven by increased childhood abuse and neglect dimensions of the ACE score. PHQ-9 scores (3.73 vs. 1.86, p = 0.03), EPDS scores (6.38 vs. 3.71, p = 0.01), and the incidence of depression (37.5% vs. 23.9%, p = 0.05) were significantly higher in participants with a history of preeclampsia versus controls. Conclusions: Childhood sets the stage for life-long health. Our findings suggest that ACEs may be a risk factor for preeclampsia and depression, uniting the developmental origins of psychiatric and obstetric risk.

Low indoleamine 2, 3 dioxygenase (IDO) activity is associated with psycho-obstetric risk.

OBJECTIVES: Preeclampsia and depression in pregnancy are among the most prevalent obstetric disorders with no known cures. While depression and preeclampsia each increase risk for the other, shared mechansisms are unclear. One possibility is low levels of Indoleamine 2,3 dioxygenase (IDO), which links immune dysregulation and oxidative arterial damage resulting in poor vascular function in both preeclampsia and depression. We hypothesized low circulating IDO activity levels in pregnancy would correspond to poor vascular function and depression symptoms. STUDY DESIGN: In this nested case-control study, clinical, demographic, and biologic data from a cohort of pregnant women recruited to longitudinal studies measuring noninvasive vascular function and circulating factors were analyzed. MAIN OUTCOME MEASURE: IDO activity across all three trimesters of pregnancy was measured using a colorimetric assay. Carotid-femoral pulse wave velocity (cfPWV), a measure of arterial stiffness, was also assessed throughout gestation by non-invasive applanation tonometry. Depression symptoms were assessed in pregnancy via the validated patient health questionnaire 9 (PHQ9). RESULTS: Participants with low second and third trimester IDO activity had significantly decreased cfPWV. This association remained statistically significant when controlled for confounders such as BMI and chronic hypertension in the third but not second trimester. While PHQ9 scores were not associated with cfPWV differences, IDO activity was lower in moderate and severely depressed relative to non-depressed pregnant individuals. CONCLUSION: These results implicate IDO in arterial stiffness and depression symptoms, suggesting that decreased IDO may be a central target for improved psycho-obstetric health.

Effect of acute heparin administration on glycocalyx thickness and endothelial function in healthy younger adults.

The endothelial glycocalyx is a dynamic, gel-like layer that is critical to normal vascular endothelial function. Heparin impairs the endothelial glycocalyx and reduces vascular endothelial function in a murine model; however, this has yet to be tested in healthy humans. We hypothesized that a single bolus dose of heparin would increase circulating glycocalyx components and decrease endothelial glycocalyx thickness resulting in blunted brachial artery vasodilation in healthy younger adults. Healthy adults (n = 19, aged 18-39 yr, 53% female) underwent measurements of the endothelial glycocalyx and vascular endothelial function at baseline and after a single bolus 5,000 U dose of heparin. The glycocalyx components syndecan-1 and heparan sulfate were measured from plasma samples using enzyme-linked immunosorbent assays. Glycocalyx thickness was determined as perfused boundary region (PBR) in sublingual microvessels using the GlycoCheck. Endothelial function was measured via ultrasonography and quantified as brachial artery flow-mediated dilation (FMD). Following acute heparin administration, there was no increase in syndecan-1 or heparan sulfate (P = 0.90 and P = 0.49, respectively). In addition, there was no change in PBR 4-7 µm (P = 0.55), PBR 10-25 µm (P = 0.63), or 4-25 µm (P = 0.49) after heparin treatment. Furthermore, we did not observe a change in FMDmm (P = 0.23), FMD% (P = 0.35), or plasma nitrite concentrations (P = 0.10) in response to heparin. Finally, time to peak dilation and peak FMD normalized to shear stress were unchanged following heparin (P = 0.59 and P = 0.21, respectively). Our pilot study suggests that a single bolus intravenous dose of heparin does not result in endothelial glycocalyx degradation or vascular endothelial dysfunction in healthy younger adults.NEW & NOTEWORTHY The endothelial glycocalyx's role in modulating vascular endothelial dysfunction with aging and disease is becoming increasingly recognized. This study presents novel findings that acute heparin administration is not a feasible method to experimentally degrade the endothelial glycocalyx and measure concurrent changes in vascular endothelial function in healthy humans. Alternative approaches will be needed to translate findings from preclinical studies and test the effects of acute endothelial glycocalyx degradation on vascular endothelial function in humans.

Performance evaluation of a non-invasive one-step multiplex RT-qPCR assay for detection of SARS-CoV-2 direct from saliva.

Polymerase chain reaction (PCR) has proven to be the gold-standard for SARS-CoV-2 detection in clinical settings. The most common approaches rely on nasopharyngeal specimens obtained from swabs, followed by RNA extraction, reverse transcription and quantitative PCR. Although swab-based PCR is sensitive, swabbing is invasive and unpleasant to administer, reducing patient compliance for regular testing and resulting in an increased risk of improper sampling. To overcome these obstacles, we developed a non-invasive one-step RT-qPCR assay performed directly on saliva specimens. The University of Nottingham Asymptomatic Testing Service protocol simplifies sample collection and bypasses the need for RNA extraction, or additives, thus helping to encourage more regular testing and reducing processing time and costs. We have evaluated the assay against the performance criteria specified by the UK regulatory bodies and attained accreditation (BS EN ISO/IEC 17,025:2017) for SARS-CoV-2 diagnostic testing by the United Kingdom Accreditation Service. We observed a sensitivity of 1 viral copy per microlitre of saliva, and demonstrated a concordance of > 99.4% between our results and those of other accredited testing facilities. We concluded that saliva is a stable medium that allows for a highly precise, repeatable, and robust testing method.

Postpartum ambulatory and home blood pressure monitoring in women with history of preeclampsia: Diagnostic agreement and detection of masked hypertension.

Women with a history of preeclampsia (hxPE) are at a four-fold higher risk for chronic hypertension after pregnancy compared with healthy pregnancy, but 'masked' hypertension cases are missed by clinical assessment alone. Twenty-four hour ambulatory blood pressure monitoring (ABPM) is the reference-standard for confirmation of hypertension diagnoses or detection of masked hypertension outside of clinical settings, whereas home blood pressure monitoring (HBPM) may represent a well-tolerated and practical alternative to ABPM in the postpartum period. The objectives of this study were to 1) assess concordance between ABPM and HBPM postpartum in women with a hxPE compared with healthy pregnancy controls and 2) evaluate HBPM in the detection of masked postpartum hypertension. Young women with a hxPE (N = 26) and controls (N = 36) underwent in-office, 24-h ABPM and 7-day HBPM 1-4 years postpartum. Chronic hypertension was more prevalent among women with a hxPE by all three blood pressure measures, but the prevalence of masked postpartum hypertension did not differ (36% vs 37%, P = 0.97). HBPM showed excellent agreement with ABPM (systolic: r = 0.78, intraclass coefficient [ICC] = 0.83; diastolic: r = 0.82, ICC = 0.88) and moderate concordance in classification of hypertension (κ = 0.54, P < 0.001). HBPM identified 21% of masked postpartum hypertension cases without false-positive cases, and HBPM measures among those with normotensive in-office readings could detect ABPM-defined masked hypertension (area under the curve [AUC] = 0.88 ± 0.06, P < 0.0001). The findings of the present study indicate that HBPM may be a useful screening modality prior or complementary to ABPM in the detection and management of postpartum hypertension.

One-day acceptance and commitment therapy (ACT) workshop improves anxiety but not vascular function or inflammation in adults with moderate to high anxiety levels in a randomized controlled trial.

OBJECTIVE: Acceptance and Commitment Therapy (ACT) is a behavioral intervention demonstrating sustained improvements in anxiety in individuals with chronic anxiety and psychological distress. Because anxiety disorders are associated with the development of cardiovascular disease (CVD), we hypothesized that a novel 1-day ACT workshop would both lower anxiety and improve vascular function in persons with moderate/high anxiety. METHODS: In a randomized controlled study, 72 adults (age 33.9 ± 8.6 (SD) years) with baseline moderate/high anxiety completed a one-day ACT intervention (n = 44, age 33.9 ± 8.7 years) or control (n = 28, age 37.1 ± 10.1 years). Pre-specified secondary outcomes were measured over 12 weeks: aortic stiffness (carotid-femoral pulse wave velocity [cfPWV]), forearm vascular endothelial function (post-ischemic peak forearm blood flow [FBF] via plethysmography), and brachial artery flow-mediated dilation (FMD). Carotid artery stiffness (ß-stiffness index), and inflammatory markers (C-reactive protein and tumor necrosis factor-alpha) were also explored. RESULTS: Although the intervention had a significant and sustained effect on the primary outcome of anxiety as measured by the Beck Anxiety Inventory, the 1-day ACT workshop was not associated with improvement in vascular or inflammatory endpoints. The intervention was unexpectedly associated with increases in ß-stiffness index that were also associated with changing trait anxiety. CONCLUSION: Anxiety improvements did not translate into improvements in any of the vascular function outcomes. This may reflect a less-than-robust effect of the intervention on anxiety, failure in design to select those with vascular dysfunction, or not intervening on a relevant causal pathway. (Trial registration NCT02915874 at www.clinicaltrials.gov).

A randomized controlled trial for symptoms of anxiety and depression: Effects of a 1-day acceptance and commitment training workshop.

BACKGROUND: Cognitive-behavioral therapies often are recommended for anxiety disorders. However, treatment adherence and compliance are major barriers for these treatments, which are often delivered in 10 to 12 sessions over several months. This randomized controlled trial (trial registration NCT02915874 at www.clinicaltrials.gov) examined the effectiveness and feasibility of a 1-day cognitive-behavioral intervention for mixed anxiety. METHODS: A total of 72 adults with moderate-to-high anxiety were randomized into a 1-day acceptance and commitment therapy (ACT) work-shop (n = 44) or treatment as usual (n = 28). Follow-up assessments were conducted 6 and 12 weeks after the workshop. Clinical outcomes were anxiety (primary) and depressive (secondary) symptoms, as measured by the Beck Anxiety Inventory and Beck Depression Inventory-II, respectively. Proposed mediators of ACT-psychological flexibility and commit-ted action-also were examined. RESULTS: Participants assigned to the ACT workshop showed significant improvements in anxiety (beta = -1.13; P = .02) and depression (beta = -1.09; P = .02) after 12 weeks. Consistent with the theoretical model, these clinical improvements were mediated by psychological flexibility and committed action. Notable limitations included the sample size, inability to blind to treatment condition, and a racially and ethnically homogeneous sample. CONCLUSIONS: Our 1-day ACT workshop was effective for anxiety with co-occurring depressive symptoms. One-day interventions are a promising alternative to weekly treatments.

Twenty-Four-Hour Blood Pressure Variability Is Associated With Lower Cognitive Performance in Young Women With a Recent History of Preeclampsia.

BACKGROUND: Women with a history of preeclampsia (hxPE) exhibit sustained arterial stiffness and elevated blood pressure postpartum. Aortic stiffness and 24-hour blood pressure variability (BPV) are associated with age-related cognitive decline. Although hxPE is related to altered cognitive function, the association between aortic stiffness and BPV with cognitive performance in young women with hxPE has not been investigated. The objectives of this study were to (i) test whether cognitive performance is lower in young women with hxPE and (ii) determine whether aortic stiffness and BPV are associated with cognitive performance independent of 24-hour average blood pressure. METHODS: Women with hxPE (N = 23) and healthy pregnancy controls (N = 38) were enrolled 1-3 years postpartum. Cognitive performance was assessed in domains of memory, processing speed, and executive function. Twenty-four-hour ambulatory blood pressure monitoring and carotid-femoral pulse wave velocity (cfPWV) were used to measure BPV and aortic stiffness, respectively. RESULTS: Women with hxPE had slower processing speed (-0.56 ± 0.17 vs. 0.34 ± 0.11 Z-score, P < 0.001) and lower executive function (-0.43 ± 0.14 vs. 0.31 ± 0.10 Z-score, P = 0.004) compared with controls independent of education, whereas memory did not differ. BPV and cfPWV (adjusted for blood pressure) did not differ between women with hxPE and controls. Greater diastolic BPV was associated with lower executive function independent of 24-hour average blood pressure and education in women with hxPE (r = -0.48, P = 0.03) but not controls (r = 0.15, P = 0.38). CONCLUSIONS: Select cognitive functions are reduced postpartum in young women with a recent hxPE and linked with elevated 24-hour diastolic BPV.

Beat-to-Beat Blood Pressure Variability in the First Trimester Is Associated With the Development of Preeclampsia in a Prospective Cohort: Relation With Aortic Stiffness.

Women with preeclampsia, a hypertensive disorder of pregnancy, exhibit greater beat-to-beat blood pressure variability (BPV) in the third trimester after clinical onset of the disorder. However, it remains unknown whether elevated BPV precedes the development of preeclampsia. A prospective study cohort of 139 women (age 30.2±4.0 years) were enrolled in early pregnancy (<14 weeks gestation). BPV was quantified by time domain analyses of 10-minute continuous beat-to-beat blood pressure recordings via finger photoplethysmography in the first, second, and third trimesters. Aortic stiffness (carotid-femoral pulse wave velocity) and spontaneous cardiovagal baroreflex sensitivity were also measured each trimester. Eighteen women (13%) developed preeclampsia. Systolic BPV was higher in all trimesters among women who developed versus did not develop preeclampsia (first: 4.8±1.3 versus 3.7±1.2, P=0.001; second: 5.1±1.8 versus 3.8±1.1, P=0.02; third: 5.2±0.8 versus 4.0±1.1 mm Hg, P=0.002). Elevated first trimester systolic BPV was associated with preeclampsia (odds ratio, 1.94 [95% CI, 1.27-2.99]), even after adjusting for risk factors (age, body mass index, systolic blood pressure, history of preeclampsia, and diabetes mellitus) and was a significant predictor of preeclampsia (area under the receiver operator characteristic curve=0.75±0.07; P=0.002). Carotid-femoral pulse wave velocity was elevated in the first trimester among women who developed preeclampsia (5.9±0.8 versus 5.2±0.8 m/s; P=0.002) and was associated with BPV after adjustment for mean blood pressure (r=0.26; P=0.005). First trimester baroreflex sensitivity did not differ between groups (P=0.23) and was not related to BPV (P=0.36). Elevated systolic BPV is independently associated with the development of preeclampsia as early as the first trimester, possibly mediated in part by higher aortic stiffness.

Dual Predation by Bacteriophage and Bdellovibrio bacteriovorus Can Eradicate Escherichia coli Prey in Situations where Single Predation Cannot.

Bacteria are preyed upon by diverse microbial predators, including bacteriophage and predatory bacteria, such as Bdellovibrio bacteriovorus While bacteriophage are used as antimicrobial therapies in Eastern Europe and are being applied for compassionate use in the United States, predatory bacteria are only just beginning to reveal their potential therapeutic uses. However, predation by either predator type can falter due to different adaptations arising in the prey bacteria. When testing poultry farm wastewater for novel Bdellovibrio isolates on Escherichia coli prey lawns, individual composite plaques were isolated containing both an RTP (rosette-tailed-phage)-like-phage and a B. bacteriovorus strain and showing central prey lysis and halos of extra lysis. Combining the purified phage with a lab strain of B. bacteriovorus HD100 recapitulated haloed plaques and increased killing of the E. coli prey in liquid culture, showing an effective side-by-side action of these predators compared to their actions alone. Using approximate Bayesian computation to select the best fitting from a variety of different mathematical models demonstrated that the experimental data could be explained only by assuming the existence of three prey phenotypes: (i) sensitive to both predators, (ii) genetically resistant to phage only, and (iii) plastic resistant to B. bacteriovorus only. Although each predator reduces prey availability for the other, high phage numbers did not abolish B. bacteriovorus predation, so both predators are competent to coexist and are causing different selective pressures on the bacterial surface while, in tandem, controlling prey bacterial numbers efficiently. This suggests that combinatorial predator therapy could overcome problems of phage resistance.IMPORTANCE With increasing levels of antibiotic resistance, the development of alternative antibacterial therapies is urgently needed. Two potential alternatives are bacteriophage and predatory bacteria. Bacteriophage therapy has been used, but prey/host specificity and the rapid acquisition of bacterial resistance to bacteriophage are practical considerations. Predatory bacteria are of interest due to their broad Gram-negative bacterial prey range and the lack of simple resistance mechanisms. Here, a bacteriophage and a strain of Bdellovibrio bacteriovorus, preyed side by side on a population of E. coli, causing a significantly greater decrease in prey numbers than either alone. Such combinatorial predator therapy may have greater potential than individual predators since prey surface changes selected for by each predator do not protect prey against the other predator.

Elevated Muscle Sympathetic Nerve Activity Contributes to Central Artery Stiffness in Young and Middle-Age/Older Adults.

Muscle sympathetic nerve activity (MSNA) influences the mechanical properties (ie, vascular smooth muscle tone and stiffness) of peripheral arteries, but it remains controversial whether MSNA contributes to stiffness of central arteries, such as the aorta and carotids. We examined whether elevated MSNA (age-related) would be independently associated with greater stiffness of central (carotid-femoral pulse wave velocity [PWV]) and peripheral (carotid-brachial PWV) arteries, in addition to lower carotid compliance coefficient, in healthy men and women (n=88, age: 19-73 years, 52% men). We also examined whether acute elevations in MSNA without increases in mean arterial pressure using graded levels of lower body negative pressure would augment central and peripheral artery stiffness in young (n=15, 60% men) and middle-age/older (MA/O, n=14, 43% men) adults. Resting MSNA burst frequency (bursts·min-1) was significantly correlated with carotid-femoral PWV ( R=0.44, P<0.001), carotid-brachial PWV ( R=0.32, P=0.004), and carotid compliance coefficient ( R=0.28, P=0.01) after controlling for sex, mean arterial pressure, heart rate, and waist-to-hip ratio (central obesity), but these correlations were abolished after further controlling for age (all P>0.05). In young and MA/O adults, MSNA was elevated during lower body negative pressure ( P<0.001) and produced significant increases in carotid-femoral PWV (young: Δ+1.3±0.3 versus MA/O: Δ+1.0±0.3 m·s-1, P=0.53) and carotid-brachial PWV (young: Δ+0.7±0.3 versus MA/O: Δ+0.7±0.5 m·s-1, P=0.92), whereas carotid compliance coefficient during lower body negative pressure was significantly reduced in young but not MA/O (young: Δ-0.04±0.01 versus MA/O: Δ0.001±0.008 mm2·mm Hg-1, P<0.01). Collectively, these data demonstrate the influence of MSNA on central artery stiffness and its potential contribution to age-related increases in stiffness of both peripheral and central arteries.

Relative burst amplitude of muscle sympathetic nerve activity is an indicator of altered sympathetic outflow in chronic anxiety.

Relative burst amplitude of muscle sympathetic nerve activity (MSNA) is an indicator of augmented sympathetic outflow and contributes to greater vasoconstrictor responses. Evidence suggests anxiety-induced augmentation of relative MSNA burst amplitude in patients with panic disorder; thus we hypothesized that acute stress would result in augmented relative MSNA burst amplitude and vasoconstriction in individuals with chronic anxiety. Eighteen participants with chronic anxiety (ANX; 8 men, 10 women, 32 ± 2 yr) and 18 healthy control subjects with low or no anxiety (CON; 8 men, 10 women, 39 ± 3 yr) were studied. Baseline MSNA and 24-h blood pressure were similar between ANX and CON ( P > 0.05); however, nocturnal systolic blood pressure % dipping was blunted among ANX ( P = 0.02). Relative MSNA burst amplitude was significantly greater among ANX compared with CON immediately preceding (anticipation) and during physiological stress [2-min cold pressor test; ANX: 73 ± 5 vs. CON: 59 ± 3% arbitrary units (AU), P = 0.03] and mental stress (4-min mental arithmetic; ANX: 65 ± 3 vs. CON: 54 ± 3% AU, P = 0.02). Increases in MSNA burst frequency, incidence, and total activity in response to stress were not augmented among ANX compared with CON ( P > 0.05), and reduction in brachial artery conductance during cold stress was similar between ANX and CON ( P = 0.92). Relative MSNA burst amplitude during mental stress was strongly correlated with state ( P < 0.01) and trait ( P = 0.01) anxiety (State-Trait Anxiety Inventory), independent of age, sex, and body mass index. Thus in response to acute stress, both mental and physiological, individuals with chronic anxiety demonstrate selective augmentation in relative MSNA burst amplitude, indicating enhanced sympathetic drive in a population with higher risk for cardiovascular disease. NEW & NOTEWORTHY Relative burst amplitude of muscle sympathetic nerve activity in response to acute mental and physiological stress is selectively augmented in individuals with chronic anxiety, which is a prevalent condition that is associated with the development of cardiovascular disease. Augmented sympathetic burst amplitude occurs with chronic anxiety in the absence of common comorbidities. These findings provide important insight into the relation between anxiety, acute stress and sympathetic activation.

Genetic and Biochemical Identification of a Novel Single-Stranded DNA-Binding Complex in Haloferax volcanii.

Single-stranded DNA (ssDNA)-binding proteins play an essential role in DNA replication and repair. They use oligonucleotide/oligosaccharide-binding (OB)-folds, a five-stranded ß-sheet coiled into a closed barrel, to bind to ssDNA thereby protecting and stabilizing the DNA. In eukaryotes the ssDNA-binding protein (SSB) is known as replication protein A (RPA) and consists of three distinct subunits that function as a heterotrimer. The bacterial homolog is termed SSB and functions as a homotetramer. In the archaeon Haloferax volcanii there are three genes encoding homologs of RPA. Two of the rpa genes (rpa1 and rpa3) exist in operons with a novel gene specific to Euryarchaeota; this gene encodes a protein that we have termed RPA-associated protein (rpap). The rpap genes encode proteins belonging to COG3390 group and feature OB-folds, suggesting that they might cooperate with RPA in binding to ssDNA. Our genetic analysis showed that rpa1 and rpa3 deletion mutants have differing phenotypes; only Δrpa3 strains are hypersensitive to DNA damaging agents. Deletion of the rpa3-associated gene rpap3 led to similar levels of DNA damage sensitivity, as did deletion of the rpa3 operon, suggesting that RPA3 and RPAP3 function in the same pathway. Protein pull-downs involving recombinant hexahistidine-tagged RPAs showed that RPA3 co-purifies with RPAP3, and RPA1 co-purifies with RPAP1. This indicates that the RPAs interact only with their respective associated proteins; this was corroborated by the inability to construct rpa1 rpap3 and rpa3 rpap1 double mutants. This is the first report investigating the individual function of the archaeal COG3390 RPA-associated proteins (RPAPs). We have shown genetically and biochemically that the RPAPs interact with their respective RPAs, and have uncovered a novel single-stranded DNA-binding complex that is unique to Euryarchaeota.