Detecting Psychological Interventions Using Bilateral Electromyographic Wearable Sensors

This study investigated the impact of auditory stimuli on muscular activation patterns using wearable surface electromyography (EMG) sensors. Employing four key muscles (Sternocleidomastoid Muscle (SCM), Cervical Erector Muscle (CEM), Quadricep Muscles (QMs), and Tibialis Muscle (TM)) and time domain features, we differentiated the effects of four interventions: silence, music, positive reinforcement, and negative reinforcement. The results demonstrated distinct muscle responses to the interventions, with the SCM and CEM being the most sensitive to changes and the TM being the most active and stimulus dependent. Post hoc analyses revealed significant intervention-specific activations in the CEM and TM for specific time points and intervention pairs, suggesting dynamic modulation and time-dependent integration. Multi-feature analysis identified both statistical and Hjorth features as potent discriminators, reflecting diverse adaptations in muscle recruitment, activation intensity, control, and signal dynamics. These features hold promise as potential biomarkers for monitoring muscle function in various clinical and research applications. Finally, muscle-specific Random Forest classification achieved the highest accuracy and Area Under the ROC Curve for the TM, indicating its potential for differentiating interventions with high precision. This study paves the way for personalized neuroadaptive interventions in rehabilitation, sports science, ergonomics, and healthcare by exploiting the diverse and dynamic landscape of muscle responses to auditory stimuli.

Establishing RTS,S/AS01 as a benchmark for comparison to next-generation malaria vaccines in a mouse model

New strategies are needed to reduce the incidence of malaria, and promising approaches include vaccines targeting the circumsporozoite protein (CSP). To improve upon the malaria vaccine, RTS,S/AS01, it is essential to standardize preclinical assays to measure the potency of next-generation vaccines against this benchmark. We focus on RTS,S/AS01-induced antibody responses and functional activity in conjunction with robust statistical analyses. Transgenic Plasmodium berghei sporozoites containing full-length P. falciparum CSP (tgPb-PfCSP) allow two assessments of efficacy: quantitative reduction in liver infection following intravenous challenge, and sterile protection from mosquito bite challenge. Two or three doses of RTS,S/AS01 were given intramuscularly at 3-week intervals, with challenge 2-weeks after the last vaccination. Minimal inter- and intra-assay variability indicates the reproducibility of the methods. Importantly, the range of this model is suitable for screening more potent vaccines. Levels of induced anti-CSP antibody 2A10 equivalency were also associated with activity: 105 μg/mL (95% CI: 68.8, 141) reduced liver infection by 50%, whereas 285 μg/mL (95% CI: 166, 404) is required for 50% sterile protection from mosquito bite challenge. Additionally, the liver burden model was able to differentiate between protected and non-protected human plasma samples from a controlled human malaria infection study, supporting these models' relevance and predictive capability. Comparison in animal models of CSP-based vaccine candidates to RTS,S/AS01 is now possible under well controlled conditions. Assessment of the quality of induced antibodies, likely a determinant of durability of protection in humans, should be possible using these methods.

Echocardiographic and pathologic identification of an aorto-left atrial fistula secondary to infective endocarditis in a canine patient

A dog was presented for lameness, fever, and extreme lethargy. On physical exam, a new heart murmur, arrhythmia, and joint effusion were detected. These findings were not detected two months prior. A diagnostic work-up confirmed septic suppurative inflammation in multiple joints. Echocardiogram revealed aortic valvular endocarditis along with a communication, as a consequence of a fistula, that extended from just below the aortic sinotubular junction to the left atrial lumen. Due to a poor prognosis, humane euthanasia was elected. Necropsy and histopathology confirmed infective endocarditis of the aortic valve and an aorto-left atrial fistulous tract extending from the left coronary sinus of the aortic valve to the lumen of left atrium.

Novel antibody competition binding assay identifies distinct serological profiles associated with protection

Introduction

Pre-erythrocytic malaria vaccines hold the promise of inducing sterile protection thereby preventing the morbidity and mortality associated with Plasmodium infection. The main surface antigen of P. falciparum sporozoites, i.e., the circumsporozoite protein (CSP), has been extensively explored as a target of such vaccines with significant success in recent years. Systematic adjuvant selection, refinements of the immunization regimen, and physical properties of the antigen may all contribute to the potential of increasing the efficacy of CSP-based vaccines. Protection appears to be dependent in large part on CSP antibodies. However due to a knowledge gap related to the exact correlates of immunity, there is a critical need to improve our ability to down select candidates preclinically before entering clinical trials including with controlled human malaria infections (CHMI).

Methods

We developed a novel multiplex competition assay based on well-characterized monoclonal antibodies (mAbs) that target crucial epitopes across the CSP molecule. This new tool assesses both, quality and epitope-specific concentrations of vaccine-induced antibodies by measuring their equivalency with a panel of well-characterized, CSP-epitope-specific mAbs.

Results

Applying this method to RTS,S-immune sera from a CHMI trial demonstrated a quantitative epitope-specificity profile of antibody responses that can differentiate between protected vs. nonprotected individuals. Aligning vaccine efficacy with quantitation of the epitope fine specificity results of this equivalency assay reveals the importance of epitope specificity.

Discussion

The newly developed serological equivalence assay will inform future vaccine design and possibly even adjuvant selection. This methodology can be adapted to other antigens and disease models, when a panel of relevant mAbs exists, and could offer a unique tool for comparing and down-selecting vaccine formulations.

Affinity-matured homotypic interactions induce spectrum of PfCSP structures that influence protection from malaria infection

The generation of high-quality antibody responses to Plasmodium falciparum (Pf) circumsporozoite protein (PfCSP), the primary surface antigen of Pf sporozoites, is paramount to the development of an effective malaria vaccine. Here we present an in-depth structural and functional analysis of a panel of potent antibodies encoded by the immunoglobulin heavy chain variable (IGHV) gene IGHV3-33, which is among the most prevalent and potent antibody families induced in the anti-PfCSP immune response and targets the Asn-Ala-Asn-Pro (NANP) repeat region. Cryo-electron microscopy (cryo-EM) reveals a remarkable spectrum of helical antibody-PfCSP structures stabilized by homotypic interactions between tightly packed fragments antigen binding (Fabs), many of which correlate with somatic hypermutation. We demonstrate a key role of these mutated homotypic contacts for high avidity binding to PfCSP and in protection from Pf malaria infection. Together, these data emphasize the importance of anti-homotypic affinity maturation in the frequent selection of IGHV3-33 antibodies and highlight key features underlying the potent protection of this antibody family.

Extending the range of Plasmodium falciparum transmission blocking antibodies

Recent work demonstrating that asymptomatic carriers of P. falciparum parasites make up a large part of the infectious reservoir highlights the need for an effective malaria vaccine. Given the historical challenges of vaccine development, multiple parasite stages have been targeted, including the sexual stages required for transmission. Using flow cytometry to efficiently screen for P. falciparum gamete/zygote surface reactivity, we identified 82 antibodies that bound live P. falciparum gametes/zygotes. Ten antibodies had significant transmission-reducing activity (TRA) in a standard membrane feeding assay and were subcloned along with 9 nonTRA antibodies as comparators. After subcloning, only eight of the monoclonals obtained have significant TRA. These eight TRA mAbs do not recognize epitopes present in any of the current recombinant transmission-blocking vaccine candidates, Pfs230D1M, Pfs48/45.6C, Pf47 D2 and rPfs25. One TRA mAb immunoprecipitates two surface antigens, Pfs47 and Pfs230, that are expressed by both gametocytes and gametes/zygotes. These two proteins have not previously been reported to associate and the recognition of both by a single TRA mAb suggests the Pfs47/Pfs230 complex is a new vaccine target. In total, Pfs230 was the dominant target antigen, with five of the eight TRA mAbs and 8 of 11 nonTRA gamete/zygote surface reactive mAbs interacting with Pfs230. Of the three remaining TRA mAbs, two recognized non-reduced, parasite-produced Pfs25 and one bound non-reduced, parasite-produced Pfs48/45. None of the TRA mAbs bound protein on an immunoblot of reduced gamete/zygote extract and two TRA mAbs were immunoblot negative, indicating none of the new TRA epitopes are linear. The identification of eight new TRA mAbs that bind epitopes not included in any of the constructs currently under advancement as transmission-blocking vaccine candidates may provide new targets worthy of further study.

Safety, tolerability, and immunogenicity of inactivated poliovirus vaccine with or without E.coli double mutant heat-labile toxin (dmLT) adjuvant in healthy adults; a phase 1 randomized study

BACKGROUND

Inactivated trivalent poliovirus vaccine (IPV) induces humoral immunity, which protects against paralytic poliomyelitis but does not induce sufficient mucosal immunity to block intestinal infection. We assessed the intestinal immunity in healthy adults in Belgium conferred by a co-formulation of IPV with the mucosal adjuvant double mutant Labile Toxin (dmLT) derived from Escherichia coli.

METHODS

Healthy fully IPV-vaccinated 18-45-year-olds were randomly allocated to three groups: on Day 1 two groups received one full dose of IPV (n = 30) or IPV + dmLT (n = 30) in a blinded manner, and the third received an open-label dose of bivalent live oral polio vaccine (bOPV types 1 and 3, n = 20). All groups received a challenge dose of bOPV on Day 29. Participants reported solicited and unsolicited adverse events (AE) using study diaries. Mucosal immune responses were measured by fecal neutralization and IgA on Days 29 and 43, with fecal shedding of challenge viruses measured for 28 days. Humoral responses were measured by serum neutralizing antibody (NAb).

RESULTS

Solicited and unsolicited AEs were mainly mild-to-moderate and transient in all groups, with no meaningful differences in rates between groups. Fecal shedding of challenge viruses in both IPV groups exceeded that of the bOPV group but was not different between IPV and IPV + dmLT groups. High serum NAb responses were observed in both IPV groups, alongside modest levels of fecal neutralization and IgA.

CONCLUSIONS

Addition of dmLT to IPV administered intramuscularly neither affected humoral nor intestinal immunity nor decreased fecal virus shedding following bOPV challenge. The tolerability of the dose of dmLT used in this study may allow higher doses to be investigated for impact on mucosal immunity. Registered on ClinicalTrials.gov - NCT04232943.

Safety, tolerability, and Plasmodium falciparum transmission-reducing activity of monoclonal antibody TB31F: a single-centre, open-label, first-in-human, dose-escalation, phase 1 trial in healthy malaria-naive adults

BACKGROUND

Malaria elimination requires interruption of the highly efficient transmission of Plasmodium parasites by mosquitoes. TB31F is a humanised monoclonal antibody that binds the gamete surface protein Pfs48/45 and inhibits fertilisation, thereby preventing further parasite development in the mosquito midgut and onward transmission. We aimed to evaluate the safety and efficacy of TB31F in malaria-naive participants.

METHODS

In this open-label, first-in-human, dose-escalation, phase 1 clinical trial, healthy, malaria-naive, adult participants were administered a single intravenous dose of 0·1, 1, 3, or 10 mg/kg TB31F or a subcutaneous dose of 100 mg TB31F, and monitored until day 84 after administration at a single centre in the Netherlands. The primary outcome was the frequency and magnitude of adverse events. Additionally, TB31F serum concentrations were measured by ELISA. Transmission-reducing activity (TRA) of participant sera was assessed by standard membrane feeding assays with Anopheles stephensi mosquitoes and cultured Plasmodium falciparum gametocytes. The trial is registered with Clinicaltrials.gov, NCT04238689.

FINDINGS

Between Feb 17 and Dec 10, 2020, 25 participants were enrolled and sequentially assigned to each dose (n=5 per group). No serious or severe adverse events occurred. In total, 33 grade 1 and six grade 2 related adverse events occurred in 20 (80%) of 25 participants across all groups. Serum of all participants administered 1 mg/kg, 3 mg/kg, or 10 mg/kg TB31F intravenously had more than 80% TRA for 28 days or more, 56 days or more, and 84 days or more, respectively. The TB31F serum concentration reaching 80% TRA was 2·1 μg/mL (95% CI 1·9-2·3). Extrapolating the duration of TRA from antibody kinetics suggests more than 80% TRA is maintained for 160 days (95% CI 136-193) following a single intravenous 10 mg/kg dose.

INTERPRETATION

TB31F is a well tolerated and highly potent monoclonal antibody capable of completely blocking transmission of P falciparum parasites from humans to mosquitoes. In areas of seasonal transmission, a single dose might cover an entire malaria season.

FUNDING

PATH's Malaria Vaccine Initiative.

Safety, immunogenicity, and reactogenicity of BNT162b2 and mRNA-1273 COVID-19 vaccines given as fourth-dose boosters following two doses of ChAdOx1 nCoV-19 or BNT162b2 and a third dose of BNT162b2 (COV-BOOST): a multicentre, blinded, phase 2, randomised trial

BACKGROUND

Some high-income countries have deployed fourth doses of COVID-19 vaccines, but the clinical need, effectiveness, timing, and dose of a fourth dose remain uncertain. We aimed to investigate the safety, reactogenicity, and immunogenicity of fourth-dose boosters against COVID-19.

METHODS

The COV-BOOST trial is a multicentre, blinded, phase 2, randomised controlled trial of seven COVID-19 vaccines given as third-dose boosters at 18 sites in the UK. This sub-study enrolled participants who had received BNT162b2 (Pfizer-BioNTech) as their third dose in COV-BOOST and randomly assigned them (1:1) to receive a fourth dose of either BNT162b2 (30 μg in 0·30 mL; full dose) or mRNA-1273 (Moderna; 50 μg in 0·25 mL; half dose) via intramuscular injection into the upper arm. The computer-generated randomisation list was created by the study statisticians with random block sizes of two or four. Participants and all study staff not delivering the vaccines were masked to treatment allocation. The coprimary outcomes were safety and reactogenicity, and immunogenicity (anti-spike protein IgG titres by ELISA and cellular immune response by ELISpot). We compared immunogenicity at 28 days after the third dose versus 14 days after the fourth dose and at day 0 versus day 14 relative to the fourth dose. Safety and reactogenicity were assessed in the per-protocol population, which comprised all participants who received a fourth-dose booster regardless of their SARS-CoV-2 serostatus. Immunogenicity was primarily analysed in a modified intention-to-treat population comprising seronegative participants who had received a fourth-dose booster and had available endpoint data. This trial is registered with ISRCTN, 73765130, and is ongoing.

FINDINGS

Between Jan 11 and Jan 25, 2022, 166 participants were screened, randomly assigned, and received either full-dose BNT162b2 (n=83) or half-dose mRNA-1273 (n=83) as a fourth dose. The median age of these participants was 70·1 years (IQR 51·6-77·5) and 86 (52%) of 166 participants were female and 80 (48%) were male. The median interval between the third and fourth doses was 208·5 days (IQR 203·3-214·8). Pain was the most common local solicited adverse event and fatigue was the most common systemic solicited adverse event after BNT162b2 or mRNA-1273 booster doses. None of three serious adverse events reported after a fourth dose with BNT162b2 were related to the study vaccine. In the BNT162b2 group, geometric mean anti-spike protein IgG concentration at day 28 after the third dose was 23 325 ELISA laboratory units (ELU)/mL (95% CI 20 030-27 162), which increased to 37 460 ELU/mL (31 996-43 857) at day 14 after the fourth dose, representing a significant fold change (geometric mean 1·59, 95% CI 1·41-1·78). There was a significant increase in geometric mean anti-spike protein IgG concentration from 28 days after the third dose (25 317 ELU/mL, 95% CI 20 996-30 528) to 14 days after a fourth dose of mRNA-1273 (54 936 ELU/mL, 46 826-64 452), with a geometric mean fold change of 2·19 (1·90-2·52). The fold changes in anti-spike protein IgG titres from before (day 0) to after (day 14) the fourth dose were 12·19 (95% CI 10·37-14·32) and 15·90 (12·92-19·58) in the BNT162b2 and mRNA-1273 groups, respectively. T-cell responses were also boosted after the fourth dose (eg, the fold changes for the wild-type variant from before to after the fourth dose were 7·32 [95% CI 3·24-16·54] in the BNT162b2 group and 6·22 [3·90-9·92] in the mRNA-1273 group).

INTERPRETATION

Fourth-dose COVID-19 mRNA booster vaccines are well tolerated and boost cellular and humoral immunity. Peak responses after the fourth dose were similar to, and possibly better than, peak responses after the third dose.

FUNDING

UK Vaccine Task Force and National Institute for Health Research.

Heterologous Expression and Evaluation of Novel Plasmodium falciparum Transmission Blocking Vaccine Candidates

Malaria transmission blocking vaccines (TBV) aim to induce antibodies that can interrupt Plasmodium falciparum development in the mosquito midgut and thereby prevent onward malaria transmission. A limited number of TBV candidates have been identified and only three (Pfs25, Pfs230 and Pfs48/45) have entered clinical testing. While one of these candidates may emerge as a highly potent TBV candidate, it is premature to determine if they will generate sufficiently potent and sustained responses. It is therefore important to explore novel candidate antigens. We recently analyzed sera from naturally exposed individuals and found that the presence and/or intensity of antibodies against 12 novel putative surface expressed gametocyte antigens was associated with transmission reducing activity. In this study, protein fragments of these novel TBV candidates were designed and heterologously expressed in Drosophila melanogaster S2 cells and Lactococcus lactis. Eleven protein fragments, covering seven TBV candidates, were successfully produced. All tested antigens were recognized by antibodies from individuals living in malaria-endemic areas, indicating that native epitopes are present. All antigens induced antigen-specific antibody responses in mice. Two antigens induced antibodies that recognized a native protein in gametocyte extract, and antibodies elicited by four antigens recognized whole gametocytes. In particular, we found that antigen Pf3D7_0305300, a putative transporter, is abundantly expressed on the surface of gametocytes. However, none of the seven novel TBV candidates expressed here induced an antibody response that reduced parasite development in the mosquito midgut as assessed in the standard membrane feeding assay. Altogether, the antigen fragments used in this study did not prove to be promising transmission blocking vaccine constructs, but led to the identification of two gametocyte surface proteins that may provide new leads for studying gametocyte biology.

Identifying Individuals Who Currently Report Feelings of Anxiety Using Walking Gait and Quiet Balance: An Exploratory Study Using Machine Learning

Literature suggests that anxiety affects gait and balance among young adults. However, previous studies using machine learning (ML) have only used gait to identify individuals who report feeling anxious. Therefore, the purpose of this study was to identify individuals who report feeling anxious at that time using a combination of gait and quiet balance ML. Using a cross-sectional design, participants (n = 88) completed the Profile of Mood Survey-Short Form (POMS-SF) to measure current feelings of anxiety and were then asked to complete a modified Clinical Test for Sensory Interaction in Balance (mCTSIB) and a two-minute walk around a 6 m track while wearing nine APDM mobility sensors. Results from our study finds that Random Forest classifiers had the highest median accuracy rate (75%) and the five top features for identifying anxious individuals were all gait parameters (turn angles, variance in neck, lumbar rotation, lumbar movement in the sagittal plane, and arm movement). Post-hoc analyses suggest that individuals who reported feeling anxious also walked using gait patterns most similar to older individuals who are fearful of falling. Additionally, we find that individuals who are anxious also had less postural stability when they had visual input; however, these individuals had less movement during postural sway when visual input was removed.

A novel CSP C-terminal epitope targeted by an antibody with protective activity against Plasmodium falciparum

Potent and durable vaccine responses will be required for control of malaria caused by Plasmodium falciparum (Pf). RTS,S/AS01 is the first, and to date, the only vaccine that has demonstrated significant reduction of clinical and severe malaria in endemic cohorts in Phase 3 trials. Although the vaccine is protective, efficacy declines over time with kinetics paralleling the decline in antibody responses to the Pf circumsporozoite protein (PfCSP). Although most attention has focused on antibodies to repeat motifs on PfCSP, antibodies to other regions may play a role in protection. Here, we expressed and characterized seven monoclonal antibodies to the C-terminal domain of CSP (ctCSP) from volunteers immunized with RTS,S/AS01. Competition and crystal structure studies indicated that the antibodies target two different sites on opposite faces of ctCSP. One site contains a polymorphic region (denoted α-ctCSP) and has been previously characterized, whereas the second is a previously undescribed site on the conserved β-sheet face of the ctCSP (denoted β-ctCSP). Antibodies to the β-ctCSP site exhibited broad reactivity with a diverse panel of ctCSP peptides whose sequences were derived from field isolates of P. falciparum whereas antibodies to the α-ctCSP site showed very limited cross reactivity. Importantly, an antibody to the β-site demonstrated inhibition activity against malaria infection in a murine model. This study identifies a previously unidentified conserved epitope on CSP that could be targeted by prophylactic antibodies and exploited in structure-based vaccine design.

Risk Factors for Testing Positive for Severe Acute Respiratory Syndrome Coronavirus 2 in a National United States Healthcare System

BACKGROUND

Identifying risk factors for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection could help health systems improve testing and screening strategies. The aim of this study was to identify demographic factors, comorbid conditions, and symptoms independently associated with testing positive for SARS-CoV-2.

METHODS

This was an observational cross-sectional study at the Veterans Health Administration, including persons tested for SARS-CoV-2 nucleic acid by polymerase chain reaction (PCR) between 28 February and 14 May 2020. Associations between demographic characteristics, diagnosed comorbid conditions, and documented symptoms with testing positive for SARS-CoV-2 were measured.

RESULTS

Of 88 747 persons tested, 10 131 (11.4%) were SARS-CoV-2 PCR positive. Positivity was associated with older age (≥80 vs <50 years: adjusted odds ratio [aOR], 2.16 [95% confidence interval {CI}, 1.97-2.37]), male sex (aOR, 1.45 [95% CI, 1.34-1.57]), regional SARS-CoV-2 burden (≥2000 vs <400 cases/million: aOR, 5.43 [95% CI, 4.97-5.93]), urban residence (aOR, 1.78 [95% CI, 1.70-1.87]), black (aOR, 2.15 [95% CI, 2.05-2.26]) or American Indian/Alaska Native Hawaiian/Pacific Islander (aOR, 1.26 [95% CI, 1.05-1.52]) vs white race, and Hispanic ethnicity (aOR, 1.52 [95% CI, 1.40-1.65]). Obesity and diabetes were the only 2 medical conditions associated with testing positive. Documented fevers, chills, cough, and diarrhea were also associated with testing positive. The population attributable fraction of positive tests was highest for geographic location (35.3%), followed by demographic variables (27.1%), symptoms (12.0%), obesity (10.5%), and diabetes (0.4%).

CONCLUSIONS

The majority of positive SARS-CoV-2 tests were attributed to geographic location, demographic characteristics, and obesity, with a minor contribution of chronic comorbid conditions.

Monoclonal antibodies block transmission of genetically diverse Plasmodium falciparum strains to mosquitoes

Malaria parasite transmission to mosquitoes relies on the uptake of sexual stage parasites during a blood meal and subsequent formation of oocysts on the mosquito midgut wall. Transmission-blocking vaccines (TBVs) and monoclonal antibodies (mAbs) target sexual stage antigens to interrupt human-to-mosquito transmission and may form important tools for malaria elimination. Although most epitopes of these antigens are considered highly conserved, little is known about the impact of natural genetic diversity on the functional activity of transmission-blocking antibodies. Here we measured the efficacy of three mAbs against leading TBV candidates (Pfs48/45, Pfs25 and Pfs230) in transmission assays with parasites from naturally infected donors compared to their efficacy against the strain they were raised against (NF54). Transmission-reducing activity (TRA) was measured as reduction in mean oocyst intensity. mAb 45.1 (α-Pfs48/45) and mAb 4B7 (α-Pfs25) reduced transmission of field parasites from almost all donors with IC80 values similar to NF54. Sequencing of oocysts that survived high mAb concentrations did not suggest enrichment of escape genotypes. mAb 2A2 (α-Pfs230) only reduced transmission of parasites from a minority of the donors, suggesting that it targets a non-conserved epitope. Using six laboratory-adapted strains, we revealed that mutations in one Pfs230 domain correlate with mAb gamete surface binding and functional TRA. Our findings demonstrate that, despite the conserved nature of sexual stage antigens, minor sequence variation can significantly impact the efficacy of transmission-blocking mAbs. Since mAb 45.1 shows high potency against genetically diverse strains, our findings support its further clinical development and may inform Pfs48/45 vaccine design.

Age differences in the association of comorbid burden with adverse outcomes in SARS-CoV-2

Background

Older age and comorbid burden are both associated with adverse outcomes in SARS-CoV-2, but it is not known whether the association between comorbid burden and adverse outcomes differs in older and younger adults.

Objective

To compare the relationship between comorbid burden and adverse outcomes in adults with SARS-CoV-2 of different ages (18–64, 65–79 and ≥ 80 years).

Design, setting, and participants

Observational longitudinal cohort study of 170,528 patients who tested positive for SARS-CoV-2 in the US Department of Veterans Affairs (VA) Health Care System between 2/28/20 and 12/31/2020 who were followed through 01/31/2021.

Measurements

Charlson Comorbidity Index (CCI); Incidence of hospitalization, intensive care unit (ICU) admission, mechanical ventilation, and death within 30 days of a positive SARS-CoV-2 test.

Results

The cumulative 30-day incidence of death was 0.8% in cohort members < 65 years, 7.1% in those aged 65–79 years and 20.6% in those aged ≥80 years. The respective 30-day incidences of hospitalization were 8.2, 21.7 and 29.5%, of ICU admission were 2.7, 8.6, and 11% and of mechanical ventilation were 1, 3.9 and 3.2%. Median CCI (interquartile range) ranged from 0.0 (0.0, 2.0) in the youngest, to 4 (2.0, 7.0) in the oldest age group. The adjusted association of CCI with all outcomes was attenuated at older ages such that the threshold level of CCI above which the risk for each outcome exceeded the reference group (1st quartile) was lower in younger than in older cohort members (p < 0.001 for all age group interactions).

Limitations

The CCI is calculated based on diagnostic codes, which may not provide an accurate assessment of comorbid burden.

Conclusions

Age differences in the distribution and prognostic significance of overall comorbid burden could inform clinical management, vaccination prioritization and population health during the pandemic and argue for more work to understand the role of age and comorbidity in shaping the care of hospitalized patients with SARS-CoV-2.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12877-021-02340-5.

Cirrhosis and Severe Acute Respiratory Syndrome Coronavirus 2 Infection in US Veterans: Risk of Infection, Hospitalization, Ventilation, and Mortality

BACKGROUND AND AIMS

Whether patients with cirrhosis have increased risk of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and the extent to which infection and cirrhosis increase the risk of adverse patient outcomes remain unclear.

APPROACH AND RESULTS

We identified 88,747 patients tested for SARS-CoV-2 between March 1, 2020, and May 14, 2020, in the Veterans Affairs (VA) national health care system, including 75,315 with no cirrhosis-SARS-CoV-2-negative (C0-S0), 9,826 with no cirrhosis-SARS-CoV-2-positive (C0-S1), 3,301 with cirrhosis-SARS-CoV-2-negative (C1-S0), and 305 with cirrhosis-SARS-CoV-2-positive (C1-S1). Patients were followed through June 22, 2020. Hospitalization, mechanical ventilation, and death were modeled in time-to-event analyses using Cox proportional hazards regression. Patients with cirrhosis were less likely to test positive than patients without cirrhosis (8.5% vs. 11.5%; adjusted odds ratio, 0.83; 95% CI, 0.69-0.99). Thirty-day mortality and ventilation rates increased progressively from C0-S0 (2.3% and 1.6%) to C1-S0 (5.2% and 3.6%) to C0-S1 (10.6% and 6.5%) and to C1-S1 (17.1% and 13.0%). Among patients with cirrhosis, those who tested positive for SARS-CoV-2 were 4.1 times more likely to undergo mechanical ventilation (adjusted hazard ratio [aHR], 4.12; 95% CI, 2.79-6.10) and 3.5 times more likely to die (aHR, 3.54; 95% CI, 2.55-4.90) than those who tested negative. Among patients with SARS-CoV-2 infection, those with cirrhosis were more likely to be hospitalized (aHR, 1.37; 95% CI, 1.12-1.66), undergo ventilation (aHR, 1.61; 95% CI, 1.05-2.46) or die (aHR, 1.65; 95% CI, 1.18-2.30) than patients without cirrhosis. Among patients with cirrhosis and SARS-CoV-2 infection, the most important predictors of mortality were advanced age, cirrhosis decompensation, and high Model for End-Stage Liver Disease score.

CONCLUSIONS

SARS-CoV-2 infection was associated with a 3.5-fold increase in mortality in patients with cirrhosis. Cirrhosis was associated with a 1.7-fold increase in mortality in patients with SARS-CoV-2 infection.

Plasmodium falciparum Pf77 and male development gene 1 as vaccine antigens that induce potent transmission-reducing antibodies

Malaria vaccines that disrupt the Plasmodium life cycle in mosquitoes and reduce parasite transmission in endemic areas are termed transmission-blocking vaccines (TBVs). Despite decades of research, there are only a few Plasmodium falciparum antigens that indisputably and reproducibly demonstrate transmission-blocking immunity. So far, only two TBV candidates have advanced to phase 1/2 clinical testing with limited success. By applying an unbiased transcriptomics-based approach, we have identified Pf77 and male development gene 1 (PfMDV-1) as two P. falciparum TBV antigens that, upon immunization, induced antibodies that caused reductions in oocyst counts in Anopheles mosquito midguts in a standard membrane feeding assay. In-depth studies were performed to characterize the genetic diversity of, stage-specific expression by, and natural immunity to these two molecules to evaluate their suitability as TBV candidates. Pf77 and PfMDV-1 display limited antigenic polymorphism, are pan-developmentally expressed within the parasite, and induce naturally occurring antibodies in Ghanaian adults, which raises the prospect of natural boosting of vaccine-induced immune response in endemic regions. Together, these biological properties suggest that Pf77 and PfMDV-1 may warrant further investigation as TBV candidates.

Trends over time in the risk of adverse outcomes among patients with SARS-CoV-2 infection

Background

We aimed to describe trends in adverse outcomes among patients who tested positive for SARS-CoV-2 between February and September 2020 within a national healthcare system.

Methods

We identified enrollees in the national U.S. Veterans Affairs healthcare system who tested positive for SARS-CoV-2 between 2/28/2020 and 9/30/2020 (n=55,952), with follow-up extending to 11/19/2020. We determined trends over time in incidence of the following outcomes that occurred within 30 days of testing positive: hospitalization, intensive care unit (ICU) admission, mechanical ventilation and death.

Results

Between February and July 2020, there were marked downward trends in the 30-day incidence of hospitalization (44.2% to 15.8%), ICU admission (20.3% to 5.3%), mechanical ventilation (12.7% to 2.2%), and death (12.5% to 4.4%), which subsequently plateaued between July and September 2020. These trends persisted after adjustment for sociodemographic characteristics, comorbid conditions, documented symptoms and laboratory tests, including among subgroups of patients hospitalized, admitted to the ICU or treated with mechanical ventilation. From February to September, there were decreases in the use of hydroxychloroquine (56.5% to 0%), azithromycin (48.3% to 16.6%) vasopressors (20.6% to 8.7%), and dialysis (11.6% to 3.8%) and increases in the use of dexamethasone (3.4% to 53.1%), other corticosteroids (4.9% to 29.0%) and remdesivir (1.7% to 45.4%) among hospitalized patients.

Conclusions

The risk of adverse outcomes in SARS-CoV-2-positive patients decreased markedly between February and July, with subsequent stabilization from July to September. These trends were not explained by changes in measured baseline patient characteristics and may reflect changing treatment practices or viral pathogenicity.

BMI and Outcomes of SARS-CoV-2 Among US Veterans

OBJECTIVE

The purpose of this study is to examine the associations of BMI with testing positive for severe acute respiratory coronavirus 2 (SARS-CoV-2) and risk of adverse outcomes in a cohort of Veterans Affairs enrollees.

METHOD

Adjusted relative risks/hazard ratios (HRs) were calculated for the associations between BMI category (underweight, normal weight, overweight, class 1 obesity, class 2 obesity, and class 3 obesity) and testing positive for SARS-CoV-2 or experiencing hospitalization, intensive care unit admission, mechanical ventilation, and death among those testing positive.

RESULTS

Higher BMI categories were associated with higher risk of a positive SARS-CoV-2 test compared with the normal weight category (class 3 obesity adjusted relative risk: 1.34, 95% CI: 1.28-1.42). Among 25,952 patients who tested positive for SARS-CoV-2, class 3 obesity was associated with higher risk of mechanical ventilation (adjusted HR [aHR]: 1.77, 95% CI: 1.35-2.32) and mortality (aHR: 1.42, 95% CI: 1.12-1.78) compared with normal weight individuals. These associations were present primarily in patients younger than 65 and were attenuated or absent in older age groups (interaction P < 0.05).

CONCLUSION

Veterans Affairs enrollees with higher BMI were more likely to test positive for SARS-CoV-2 and were more likely to be mechanically ventilated or die if infected with SARS-CoV-2. Higher BMI contributed relatively more to the risk of death in those younger than 65 years of age as compared with other age categories.

Multiplex serological assay for establishing serological profiles of polymorphic, closely related peptide antigens

Profiling of serological responses to establish the landscape of antibody specificities in individuals exposed to pathogens or vaccines is crucial for (a) revealing humoral immune correlates of protection; (b) uncovering markers of pathogen exposure; and (c) identifying antigens and epitopes associated with disease vs. protection. Establishing the antigenic profile of serological responses requires either expensive microarrays or labor- and time-intensive ELISA assays. Multiplex assay platforms are increasingly being evaluated for their usefulness for high-throughput testing of sera or plasma. The methodology described here utilizes a plate-based assay that allows the simultaneous detection of up to ten antigens per well in a 96 well format using an electrochemiluminescence immunoassay (ECLIA).•The newly developed protocol outlines high-throughput profiling of serological responses using a multiplex testing platform with subsequent computational analysis.•The protocol is a modification of the basic assay development manual from the manufacturer of the MESO QuickPlex SQ 120 instrument (MSD, Gaithersburg, MD) and can be used for synthetic peptides as well as full length proteins.•The protocol can be applied to map serological responses to pathogens or pathogen-derived antigens to establish serological profiles in search for biomarkers or immune correlates.

Development of COVIDVax Model to Estimate the Risk of SARS-CoV-2-Related Death Among 7.6 Million US Veterans for Use in Vaccination Prioritization

Importance

A strategy that prioritizes individuals for SARS-CoV-2 vaccination according to their risk of SARS-CoV-2-related mortality would help minimize deaths during vaccine rollout.

Objective

To develop a model that estimates the risk of SARS-CoV-2-related mortality among all enrollees of the US Department of Veterans Affairs (VA) health care system.

Design, Setting, and Participants

This prognostic study used data from 7 635 064 individuals enrolled in the VA health care system as of May 21, 2020, to develop and internally validate a logistic regression model (COVIDVax) that predicted SARS-CoV-2-related death (n = 2422) during the observation period (May 21 to November 2, 2020) using baseline characteristics known to be associated with SARS-CoV-2-related mortality, extracted from the VA electronic health records (EHRs). The cohort was split into a training period (May 21 to September 30) and testing period (October 1 to November 2).

Main Outcomes and Measures

SARS-CoV-2-related death, defined as death within 30 days of testing positive for SARS-CoV-2. VA EHR data streams were imported on a data integration platform to demonstrate that the model could be executed in real-time to produce dashboards with risk scores for all current VA enrollees.

Results

Of 7 635 064 individuals, the mean (SD) age was 66.2 (13.8) years, and most were men (7 051 912 [92.4%]) and White individuals (4 887 338 [64.0%]), with 1 116 435 (14.6%) Black individuals and 399 634 (5.2%) Hispanic individuals. From a starting pool of 16 potential predictors, 10 were included in the final COVIDVax model, as follows: sex, age, race, ethnicity, body mass index, Charlson Comorbidity Index, diabetes, chronic kidney disease, congestive heart failure, and Care Assessment Need score. The model exhibited excellent discrimination with area under the receiver operating characteristic curve (AUROC) of 85.3% (95% CI, 84.6%-86.1%), superior to the AUROC of using age alone to stratify risk (72.6%; 95% CI, 71.6%-73.6%). Assuming vaccination is 90% effective at preventing SARS-CoV-2-related death, using this model to prioritize vaccination was estimated to prevent 63.5% of deaths that would occur by the time 50% of VA enrollees are vaccinated, significantly higher than the estimate for prioritizing vaccination based on age (45.6%) or the US Centers for Disease Control and Prevention phases of vaccine allocation (41.1%).

Conclusions and Relevance

In this prognostic study of all VA enrollees, prioritizing vaccination based on the COVIDVax model was estimated to prevent a large proportion of deaths expected to occur during vaccine rollout before sufficient herd immunity is achieved.

Structural and biophysical correlation of anti-NANP antibodies with in vivo protection against P. falciparum

The most advanced P. falciparum circumsporozoite protein-based malaria vaccine, RTS,S/AS01 (RTS,S), confers partial protection but with antibody titers that wane relatively rapidly, highlighting the need to elicit more potent and durable antibody responses. Here, we elucidate crystal structures, binding affinities and kinetics, and in vivo protection of eight anti-NANP antibodies derived from an RTS,S phase 2a trial and encoded by three different heavy-chain germline genes. The structures reinforce the importance of homotypic Fab-Fab interactions in protective antibodies and the overwhelmingly dominant preference for a germline-encoded aromatic residue for recognition of the NANP motif. In this study, antibody apparent affinity correlates best with protection in an in vivo mouse model, with the more potent antibodies also recognizing epitopes with repeating secondary structural motifs of type I β- and Asn pseudo 310 turns; such insights can be incorporated into design of more effective immunogens and antibodies for passive immunization.

Breadth of humoral immune responses to the C-terminus of the circumsporozoite protein is associated with protective efficacy induced by the RTS,S malaria vaccine.. [DOI: 10.1101/2020.11.15.20232033]

The circumsporozoite protein (CSP) is the main surface antigen of malaria sporozoites and a prime vaccine target. Responses induced by the CSP-based RTS,S vaccine towards the polymorphic C-terminal region of P.falciparum-CSP raise concerns that vaccines using single alleles may have lower efficacy against genotypic variants. We characterized the extent of C-terminal cross-reactivity of antibodies induced by RTS,S (based on the 3D7 allele) with variants representing seven circulating field isolates through a novel HTS-multiplex assay for screening closely related peptides. Reactivity to variants showed approximately 30-fold reduction in recognition relative to 3D7. The degree of reduced cross-reactivity,ranging from 21 to 69-fold, directly correlated with the number of polymorphisms between variants and 3D7. Surprisingly, protection assessed by challenge with 3D7 parasites was strongly associated with higher C-terminal antibody breadth suggesting that C-terminal specific avidity or fine-specificity may play a role in RTS,S/AS01B-mediated protection and that breadth of C-terminal CSP-specific antibody responses may be a marker of protection.

Factors Affecting Thermal Insulation of Songbird Nests as Measured Using Temperature Loggers

AbstractBird nests represent an extended phenotype that is variable among and within species in terms of nest location and construction materials. It has also been suggested that nests indicate niche construction, although empirical evidence to support this is lacking. The nest wall is often considered to confer some insulation because this would help minimize the energetic expenditure by the incubating adult. However, it has been previously suggested that nests are constructed primarily for their structural role rather than for insulation, but to date, studies have used a variety of techniques to investigate the insulation of nest walls but only for relatively few species. This study used temperature loggers to determine insulatory values of nests for 16 previously undescribed species and to replicate values for eight previously described species. In addition, data for nest wall insulation that were determined using temperature loggers have been collated for a total of 32 different passerine species. The effects of nest dimensions, mass, and composition on these values were examined. Base thickness, but not wall thickness, and nest mass significantly positively affected insulatory values. This study found that the proportions of feathers and moss in the nest wall significantly positively correlated with insulatory values. This suggests that there is a key role for nest materials in determining insulation, which provides empirical evidence that nest building constitutes niche construction. The data will also help us interpret data from future studies of the thermal properties of nests. Ultimately, we need to develop our understanding of the role of insulatory values in the evolution of nest function.

Risk Factors for Hospitalization, Mechanical Ventilation, or Death Among 10 131 US Veterans With SARS-CoV-2 Infection

Importance

Identifying independent risk factors for adverse outcomes in patients infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) can support prognostication, resource utilization, and treatment.

Objective

To identify excess risk and risk factors associated with hospitalization, mechanical ventilation, and mortality in patients with SARS-CoV-2 infection.

Design, Setting, and Participants

This longitudinal cohort study included 88 747 patients tested for SARS-CoV-2 nucleic acid by polymerase chain reaction between Feburary 28 and May 14, 2020, and followed up through June 22, 2020, in the Department of Veterans Affairs (VA) national health care system, including 10 131 patients (11.4%) who tested positive.

Exposures

Sociodemographic characteristics, comorbid conditions, symptoms, and laboratory test results.

Main Outcomes and Measures

Risk of hospitalization, mechanical ventilation, and death were estimated in time-to-event analyses using Cox proportional hazards models.

Results

The 10 131 veterans with SARS-CoV-2 were predominantly male (9221 [91.0%]), with diverse race/ethnicity (5022 [49.6%] White, 4215 [41.6%] Black, and 944 [9.3%] Hispanic) and a mean (SD) age of 63.6 (16.2) years. Compared with patients who tested negative for SARS-CoV-2, those who tested positive had higher rates of 30-day hospitalization (30.4% vs 29.3%; adjusted hazard ratio [aHR], 1.13; 95% CI, 1.08-1.13), mechanical ventilation (6.7% vs 1.7%; aHR, 4.15; 95% CI, 3.74-4.61), and death (10.8% vs 2.4%; aHR, 4.44; 95% CI, 4.07-4.83). Among patients who tested positive for SARS-CoV-2, characteristics significantly associated with mortality included older age (eg, ≥80 years vs <50 years: aHR, 60.80; 95% CI, 29.67-124.61), high regional COVID-19 disease burden (eg, ≥700 vs <130 deaths per 1 million residents: aHR, 1.21; 95% CI, 1.02-1.45), higher Charlson comorbidity index score (eg, ≥5 vs 0: aHR, 1.93; 95% CI, 1.54-2.42), fever (aHR, 1.51; 95% CI, 1.32-1.72), dyspnea (aHR, 1.78; 95% CI, 1.53-2.07), and abnormalities in the certain blood tests, which exhibited dose-response associations with mortality, including aspartate aminotransferase (>89 U/L vs ≤25 U/L: aHR, 1.86; 95% CI, 1.35-2.57), creatinine (>3.80 mg/dL vs 0.98 mg/dL: aHR, 3.79; 95% CI, 2.62-5.48), and neutrophil to lymphocyte ratio (>12.70 vs ≤2.71: aHR, 2.88; 95% CI, 2.12-3.91). With the exception of geographic region, the same covariates were independently associated with mechanical ventilation along with Black race (aHR, 1.52; 95% CI, 1.25-1.85), male sex (aHR, 2.07; 95% CI, 1.30-3.32), diabetes (aHR, 1.40; 95% CI, 1.18-1.67), and hypertension (aHR, 1.30; 95% CI, 1.03-1.64). Notable characteristics that were not significantly associated with mortality in adjusted analyses included obesity (body mass index ≥35 vs 18.5-24.9: aHR, 0.97; 95% CI, 0.77-1.21), Black race (aHR, 1.04; 95% CI, 0.88-1.21), Hispanic ethnicity (aHR, 1.03; 95% CI, 0.79-1.35), chronic obstructive pulmonary disease (aHR, 1.02; 95% CI, 0.88-1.19), hypertension (aHR, 0.95; 95% CI, 0.81-1.12), and smoking (eg, current vs never: aHR, 0.87; 95% CI, 0.67-1.13). Most deaths in this cohort occurred in patients with age of 50 years or older (63.4%), male sex (12.3%), and Charlson Comorbidity Index score of at least 1 (11.1%).

Conclusions and Relevance

In this national cohort of VA patients, most SARS-CoV-2 deaths were associated with older age, male sex, and comorbidity burden. Many factors previously reported to be associated with mortality in smaller studies were not confirmed, such as obesity, Black race, Hispanic ethnicity, chronic obstructive pulmonary disease, hypertension, and smoking.

Comparison of ELISA with electro-chemiluminescence technology for the qualitative and quantitative assessment of serological responses to vaccination

Background

Profiling immune responses induced by either infection or vaccination can provide insight into identification of correlates of protection. Furthermore, profiling of serological responses can be used to identify biomarkers indicative of exposure to pathogens. Conducting such immune surveillance requires readout methods that are high-throughput, robust, and require small sample volumes. While the enzyme-linked immunosorbent assay (ELISA) is the classical readout method for assessing serological responses, the advent of multiplex assays has significantly increased the throughput and capacity for immunoprofiling. This report describes the development and assay performance (sensitivity, linearity of detection, requirement for multiple dilutions for each sample, intra- and inter-assay variability) of an electro-chemiluminescence (ECLIA)-based multiplex assay.

Methods

The current study describes the development of a multiplex ECLIA-based assay and characterizes the sensitivity, linear range, and inter- and intra-assay variability of the ECLIA platform and its agreement with the traditional ELISA. Special emphasis was placed on potential antigenic competition when testing closely related antigens in the multiplex format.

Results

Multiplexing of antigens in ECLIA provides significant practical benefits in terms of reducing sample volume requirements and experimental time. Beyond the practical advantages of multiplexing, the ECLIA provides superior assay performance when compared to the ELISA. Not only does ECLIA show good agreement with the ELISA assay, but the linear range of ECLIA is also sufficiently wide to permit single-dilution measurements of concentration without the need to do serial dilutions. The lack of antigenic competition allows the simultaneous testing of closely related antigens, such as plate antigens representing different alleles of the same protein, which can inform about cross-reactivities—or lack thereof—of serological responses.

Conclusion

The advantages of the newly developed tool for assessing the antigen profiles of serological responses may ultimately lead to the identification of biomarkers associated with various disease stages and or protection against disease.

Characterization of two in vivo challenge models to measure functional activity of monoclonal antibodies to Plasmodium falciparum circumsporozoite protein

BACKGROUND

New strategies are needed to reduce the incidence of malaria, and promising approaches include the development of vaccines and monoclonal antibodies (mAbs) that target the circumsporozoite protein (CSP). To select the best candidates and speed development, it is essential to standardize preclinical assays to measure the potency of such interventions in animal models.

METHODS

Two assay configurations were studied using transgenic Plasmodium berghei expressing Plasmodium falciparum full-length circumsporozoite protein. The assays measured (1) reduction in parasite infection of the liver (liver burden) following an intravenous (i.v) administration of sporozoites and (2) protection from parasitaemia following mosquito bite challenge. Two human CSP mAbs, AB311 and AB317, were compared for their ability to inhibit infection. Multiple independent experiments were conducted to define assay variability and resultant impact on the ability to discriminate differences in mAb functional activity.

RESULTS

Overall, the assays produced highly consistent results in that all individual experiments showed greater functional activity for AB317 compared to AB311 as calculated by the dose required for 50% inhibition (ID50) as well as the serum concentration required for 50% inhibition (IC50). The data were then used to model experimental designs with adequate statistical power to rigorously screen, compare, and rank order novel anti-CSP mAbs.

CONCLUSION

The results indicate that in vivo assays described here can provide reliable information for comparing the functional activity of mAbs. The results also provide guidance regarding selection of the appropriate experimental design, dose selection, and group sizes.

Structure and mechanism of monoclonal antibody binding to the junctional epitope of Plasmodium falciparum circumsporozoite protein

Lasting protection has long been a goal for malaria vaccines. The major surface antigen on Plasmodium falciparum sporozoites, the circumsporozoite protein (PfCSP), has been an attractive target for vaccine development and most protective antibodies studied to date interact with the central NANP repeat region of PfCSP. However, it remains unclear what structural and functional characteristics correlate with better protection by one antibody over another. Binding to the junctional region between the N-terminal domain and central NANP repeats has been proposed to result in superior protection: this region initiates with the only NPDP sequence followed immediately by NANP. Here, we isolated antibodies in Kymab mice immunized with full-length recombinant PfCSP and two protective antibodies were selected for further study with reactivity against the junctional region. X-ray and EM structures of two monoclonal antibodies, mAb667 and mAb668, shed light on their differential affinity and specificity for the junctional region. Importantly, these antibodies also bind to the NANP repeat region with equal or better affinity. A comparison with an NANP-only binding antibody (mAb317) revealed roughly similar but statistically distinct levels of protection against sporozoite challenge in mouse liver burden models, suggesting that junctional antibody protection might relate to the ability to also cross-react with the NANP repeat region. Our findings indicate that additional efforts are necessary to isolate a true junctional antibody with no or much reduced affinity to the NANP region to elucidate the role of the junctional epitope in protection.

The circumsporozoite protein (CSP) of Plasmodium falciparum malaria has been the foundation for the design of transmission blocking malaria vaccines. To date, the most promising CSP-based vaccine candidate is RTS,S, which consists of the central repeating NANP amino-acid sequence and the C-terminal domain of CSP fused to hepatitis B surface antigen that assembles into virus-like particles. Potential shortcomings of RTS,S includes the lack of other potential CSP epitopes such as the junctional epitope, which is located between the N-terminal domain of CSP and the start of the NANP repeat region. Here, we elicited antibodies against full-length CSP and screened for junctional epitope binding. We then used an array of biophysical techniques to elucidate the nature of the binding and tested the level of two protective antibodies in a mouse challenge model. Although the antibodies were able to bind both junctional and NANP epitopes, the in vivo data showed distinct levels of protection between themselves and also to an NANP-only binder. Our data suggest that their protection ability may be related to the strong cross-reactivity with NANP epitopes. Since all reported junctional antibodies to date have dual-specificity, we suggest that a true junctional binder with no or very low NANP affinity, if one can be found, is essential to evaluate the contribution of the junctional epitope to protection.

Diverse Antibody Responses to Conserved Structural Motifs in Plasmodium falciparum Circumsporozoite Protein

Malaria vaccine candidate RTS,S/AS01 is based on the central and C-terminal regions of the circumsporozoite protein (CSP) of P. falciparum. mAb397 was isolated from a volunteer in an RTS,S/AS01 clinical trial, and it protects mice from infection by malaria sporozoites. However, mAb397 originates from the less commonly used VH3-15 germline gene compared to the VH3-30/33 antibodies generally elicited by RTS,S to the central NANP repeat region of CSP. The crystal structure of mAb397 with an NPNA₄ peptide shows that the central NPNA forms a type I β-turn and is the main recognition motif. In most anti-NANP antibodies studied to date, a germline-encoded Trp is used to engage the Pro in NPNA β-turns, but here the Trp interacts with the first Asn. This “conserved” Trp, however, can arise from different germline genes and be located in the heavy or the light chain. Variation in the terminal ψ angles of the NPNA β-turns results in different dispositions of the subsequent NPNA and, hence, different stoichiometries and modes of antibody binding to rsCSP. Diverse protective antibodies against NANP repeats are therefore not limited to a single germline gene response or mode of binding.

•

mAb397 from an RTS,S trial binds NANP repeats of malaria circumsporozoite protein.

•

Protective mAb397 is encoded by the VH3-15 gene that is rare for NANP antibodies.

•

Anti-NANP mAbs bind type I β-turns in three modes using germline-encoded Trp residues.

•

The Trp of mAb397 interacts with Asn instead of Pro in the NPNA type I β-turn.

•

Diversity in NANP immune responses can aid in next-generation vaccine design.

Optimization of an in vivo model to study immunity to Plasmodium falciparum pre-erythrocytic stages

BACKGROUND

The circumsporozoite protein (CSP) of Plasmodium is a key surface antigen that induces antibodies and T-cells, conferring immune protection in animal models and humans. However, much of the work on CSP and immunity has been developed based on studies using rodent or non-human primate CSP antigens, which may not be entirely translatable to CSP expressed by human malaria parasites, especially considering the host specificity of the different species.

METHODS

Using a genetically engineered strain of Plasmodium berghei that expresses luciferase, GFP and the Plasmodium falciparum orthologue of CSP, the effect of laboratory preparation, mosquito treatment and mouse factors on sporozoite infectivity was assessed using an in vivo bioluminescence assay on mice. This assay was compared with a PCR-based protection assay using an already described monoclonal antibody that can provide sterile protection against sporozoite challenge.

RESULTS

Bioluminescence assay demonstrated similar detection levels of the quantity and kinetics of liver-stage infection, compared to PCR-based detection. This assay was used to evaluate treatment of sporozoite and delivery method on mouse infectivity, as well as the effects of age, sex and strain of mice. Finally, this assay was used to test the protective capacity of monoclonal antibody AB317; results strongly recapitulate the findings of previous work on this antibody.

CONCLUSIONS

The PbGFP-Luc line and in vivo bioluminescence imaging provide highly sensitive read-outs of liver-stage infection in mice, and this method can be useful to reliably evaluate potency of pre-erythrocytic interventions.

The Plasmodium falciparum circumsporozoite protein produced in Lactococcus lactis is pure and stable

The Plasmodium falciparum circumsporozoite protein (PfCSP) is a sporozoite surface protein whose role in sporozoite motility and cell invasion has made it the leading candidate for a pre-erythrocytic malaria vaccine. However, production of high yields of soluble recombinant PfCSP, including its extensive NANP and NVDP repeats, has proven problematic. Here, we report on the development and characterization of a secreted, soluble, and stable full-length PfCSP (containing 4 NVDP and 38 NANP repeats) produced in the Lactococcus lactis expression system. The recombinant full-length PfCSP, denoted PfCSP4/38, was produced initially with a histidine tag and purified by a simple two-step procedure. Importantly, the recombinant PfCSP4/38 retained a conformational epitope for antibodies as confirmed by both in vivo and in vitro characterizations. We characterized this complex protein by HPLC, light scattering, MS analysis, differential scanning fluorimetry, CD, SDS-PAGE, and immunoblotting with conformation-dependent and -independent mAbs, which confirmed it to be both pure and soluble. Moreover, we found that the recombinant protein is stable at both frozen and elevated-temperature storage conditions. When we used L. lactis-derived PfCSP4/38 to immunize mice, it elicited high levels of functional antibodies that had the capacity to modify sporozoite motility in vitro We concluded that the reported yield, purity, results of biophysical analyses, and stability of PfCSP4/38 warrant further consideration of using the L. lactis system for the production of circumsporozoite proteins for preclinical and clinical applications in malaria vaccine development.

Robust antibody and CD8+ T-cell responses induced by P. falciparum CSP adsorbed to cationic liposomal adjuvant CAF09 confer sterilizing immunity against experimental rodent malaria infection

Despite several decades of extensive research, the development of a highly efficacious malaria vaccine has yet to be accomplished. While the RTS,S malaria vaccine candidate shows the potential to prevent a substantial number of clinical malaria cases, significant improvements in protective efficacy are still needed. Multiple studies have shown that RTS,S induces protective antibody and CD4⁺ T-cell responses, but limited or negligible CD8⁺ T cells. In this study, we evaluated the immunogenicity and protective capacity of full-length recombinant Plasmodium falciparum circumsporozoite protein administered with the novel cationic liposomal adjuvant system CAF09. Using newly developed transgenic rodent malaria parasites expressing the full-length Plasmodium falciparum circumsporozoite protein, we demonstrate that this liposome-based protein-in-adjuvant formulation is capable of inducing robust antibody and CD8⁺ T-cell responses that strongly inhibit parasite infection and development of liver stages, conferring durable sterilizing immunity. These findings underscore the potential of liposome-based adjuvants for inducing robust humoral and CD8⁺ T-cell responses and warrant further studies toward the development of novel subunit vaccine formulations with this adjuvant system.

A vaccine consisting of parasitic proteins enveloped by fatty molecules provides comprehensive protection against malaria in a rodent model, Previous and current malaria vaccines concentrate on priming antibodies to recognize malarial infection, despite evidence that, by activating ‘killer’ CD8⁺ T cells, greater protection is conferred against the disease. Fidel Zavala, of the Johns Hopkins University, United States, and an international group of researchers developed their vaccine by encapsulating proteins from the malaria-causing parasite Plasmodium falciparum in fat-based carriers called liposomes. In past experiments, killer T cells recruited via this vaccine-type have effectively protected against other diseases. In this study, the vaccine induced both CD8⁺ T cell and antibody responses and provided significant immunity against P. falciparum-instigated malaria. As a highly efficacious vaccine against malaria is not yet available, this research will likely prove invaluable in guiding further studies.

An inter-laboratory comparison of standard membrane-feeding assays for evaluation of malaria transmission-blocking vaccines

BACKGROUND

An effective malaria transmission-blocking vaccine may play an important role in malaria elimination efforts, and a robust biological assay is essential for its development. The standard membrane-feeding assay (SMFA) for Plasmodium falciparum infection of mosquitoes is considered a "gold standard" assay to measure transmission-blocking activity of test antibodies, and has been utilized widely in both non-clinical and clinical studies. While several studies have discussed the inherent variability of SMFA within a study group, there has been no assessment of inter-laboratory variation. Therefore, there is currently no assurance that SMFA results are comparable between different studies.

METHODS

Mouse anti-Pfs25 monoclonal antibody (mAb, 4B7 mAb), rat anti-Pfs48/45 mAb (85RF45.1 mAb) and a human polyclonal antibody (pAb) collected from a malaria-exposed adult were tested at the same concentrations (6-94 μg/mL for 4B7, 1.2-31.3 μg/mL for 85RF45.1 and 23-630 μg/mL for human pAb) in two laboratories following their own standardized SMFA protocols. The mAbs and pAb, previously shown to have strong inhibition activities in the SMFA, were tested at three or four concentrations in two or three independent assays in each laboratory, and percent inhibition in mean oocyst intensity relative to a control in the same feed was determined in each feeding experiment.

RESULTS

Both monoclonal and polyclonal antibodies dose-dependently reduced oocyst intensity in all experiments performed at the two test sites. In both laboratories, the inter-assay variability in percent inhibition in oocyst intensity decreased at higher levels of inhibition, regardless of which antibody was tested. At antibody concentrations that led to a >80 % reduction in oocyst numbers, the inter-laboratory variations were in the same range compared with the inter-assay variation observed within a single laboratory, and the differences in best estimates from multiple feeds between the two laboratories were <5 percentage points.

CONCLUSIONS

This study confirms previous reports that the precision of the SMFA increases with increasing percent inhibition. Moreover, the variation between the two laboratories is not greater than the variation observed within a laboratory. The findings of this study provide guidance for comparison of SMFA data from different laboratories.

Overuse of short-acting beta-agonist bronchodilators in COPD during periods of clinical stability

BACKGROUND

Overuse of short-acting beta-agonists (SABA) is described in asthma, but little is known about overuse of SABA in chronic obstructive pulmonary disease (COPD).

METHODS

Prospective 3-month cohort study of patients with moderate-to-severe COPD who were provided a portable electronic inhaler sensor to monitor daily SABA use. Subjects wore a pedometer for 3 seven-day periods and were asked to complete a daily diary of symptoms and inhaler use. Overuse was defined as >8 actuations of their SABA per day while clinically stable.

RESULTS

Among 32 participants, 15 overused their SABA inhaler at least once (mean 8.6 ± 5.0 puffs/day), and 6 overused their inhaler more than 50% of monitored days. Compared to those with no overuse, overusers had greater dyspnea (modified Medical Research Council Dyspnea Scale: 2.7 vs. 1.9, p = 0.02), were more likely to use home oxygen (67% vs. 29%, p = 0.04), and were more likely to be on maximal inhaled therapy (long-acting beta-agonist, long-acting antimuscarinic agent, and an inhaled steroid: 40% vs. 6%, p = 0.03), and most had completed pulmonary rehabilitation (67% vs. 0%, p < 0.001). However, 27% of overusers of SABA were not on guideline-concordant COPD therapy.

CONCLUSIONS

Overuse of SABA was common and associated with increased disease severity and symptoms, even though overusers were on more COPD-related inhalers and more had completed pulmonary rehabilitation. More research is needed to understand factors associated with inhaler overuse and how to improve correct inhaler use.

A slot blot immunoassay for quantitative detection of Plasmodium falciparum circumsporozoite protein in mosquito midgut oocyst

There is still a need for sensitive and reproducible immunoassays for quantitative detection of malarial antigens in preclinical and clinical phases of vaccine development and in epidemiology and surveillance studies, particularly in the vector host. Here we report the results of sensitivity and reproducibility studies for a research-grade, quantitative enhanced chemiluminescent-based slot blot assay (ECL-SB) for detection of both recombinant Plasmodium falciparum circumsporozoite protein (rPfCSP) and native PfCSP from Oocysts (Pf Oocyst) developing in the midguts of Anopheles stephensi mosquitoes. The ECL-SB detects as little as 1.25 pg of rPfCSP (linear range of quantitation 2.5-20 pg; R2 = 0.9505). We also find the earliest detectable expression of native PfCSP in Pf Oocyst by ECL-SB occurs on day 7 post feeding with infected blood meal. The ECL-SB was able to detect approximately as few as 0.5 day 8 Pf Oocysts (linear quantitation range 1-4, R2 = 0.9795) and determined that one Pf Oocyst expressed approximately 2.0 pg (0.5-3 pg) of native PfCSP, suggesting a similar range of detection for recombinant and native forms of Pf CSP. The ECL-SB is highly reproducible; the Coefficient of Variation (CV) for inter-assay variability for rPf CSP and native PfCSP were 1.74% and 1.32%, respectively. The CVs for intra-assay variability performed on three days for rPf CSP were 2.41%, 0.82% and 2% and for native Pf CSP 1.52%, 0.57%, and 1.86%, respectively. In addition, the ECL-SB was comparable to microscopy in determining the P. falciparum prevalence in mosquito populations that distinctly contained either high and low midgut Pf Oocyst burden. In whole mosquito samples, estimations of positivity for P. falciparum in the high and low burden groups were 83.3% and 23.3% by ECL-SB and 85.7% and 27.6% by microscopy. Based on its performance characteristics, ECL-SB could be valuable in vaccine development and to measure the parasite prevalence in mosquitoes and transmission-blocking interventions in endemic areas.

Preclinical Evaluation of a Chimeric Malaria Vaccine Candidate in Montanide ISA 720®: Immunogenecity and Safety in Rhesus Macaques

Several malarial antigens are in development as potential vaccine candidates as part of a concerted effort to control the disease, which kills more than one million people per year. Although some antigens have demonstrated an impact against the malaria parasite, Plasmodium falciparum, many researchers hypothesize that a combination of antigens will be required to generate high levels of efficacy against clinical disease. PfCP2.9 is a chimeric protein that includes MSP119 and domain III of AMA1 [AMA1 (111)] of Plasmodium falciparum in a single recombinant molecule. The antigen, formulated in Seppic's ISA 720 adjuvant, is approaching Phase I clinical testing in humans. The purpose of this study was to assess the safety of this vaccine and to explore possible dosage levels for clinical evaluation. Groups of five monkeys each were immunized i.m. with 25 microg, 50 microg, 100 microg and 200 microg of PfCP2.9/ISA 720 in 0.5 mL on days 0 and 112. The mean anti-PfCP2.9 titres to the 50 microg dose group were higher than the other dose groups; however, there was no statistically significant difference between the anti-CP2.9 titres of any of the groups, suggesting that the immune response to PfCP2.9 was saturated at 25 microg. One animal in the 100 microg dose group elicited a higher antibody and IFN-gamma response to PfCP2.9 than the rest of the cohort; this animal developed a small sterile abscess following the second vaccination, which spontaneously resolved within one week.

IN CONCLUSION

(a) 50 microg is highly immunogenic, appears safe, and is likely to be an appropriate dose for clinical evaluation; and (b) a conservative trial design is warranted to avoid any unexpected reactogenicity with the PfCP2.9/ISA 720 formulation.

Western blot assay for quantitative and qualitative antigen detection in vaccine development

Immunological methods for quantitative measurement, antigenic characterization, and monitoring the stability of active immunogenic component(s) are a critical need in the vaccine development process. This unit describes an enhanced chemiluminescence-based western blot for quantitative detection of Plasmodium falciparum circumsporozoite protein (PfCSP), a major malaria candidate vaccine antigen. The most salient features of this assay are its high sensitivity and reproducibility; it can reliably detect ∼5 to 10 pg PfCSP expressed on native parasites or recombinantly expressed in Escherichia coli. Although described for a specific vaccine antigen, this assay should be applicable for any antigen-antibody combination for which relevant detection reagents are available. Detailed stepwise experimental procedures and methods for data acquisition and analysis are described.

Effects of respiratory and non-respiratory factors on disability among older adults with airway obstruction: the Cardiovascular Health Study

BACKGROUND

High rates of disability associated with chronic airway obstruction may be caused by impaired pulmonary function, pulmonary symptoms, other chronic diseases, or systemic inflammation.

METHODS

We analyzed data from the Cardiovascular Health Study, a longitudinal cohort of 5888 older adults. Categories of lung function (normal; restricted; borderline, mild-moderate, and severe obstruction) were delineated by baseline spirometry (without bronchodilator). Disability-free years were calculated as total years alive and without self-report of difficulty performing &γτ;1 Instrumental Activities of Daily Living over 6 years of follow-up. Using linear regression, we compared disability-free years by lung disease category, adjusting for demographic factors, body mass index, smoking, cognition, and other chronic co-morbidities. Among participants with airflow obstruction, we examined the association of respiratory factors (FEV1 and dyspnea) and non-respiratory factors (ischemic heart disease, congestive heart failure, diabetes, muscle weakness, osteoporosis, depression and cognitive impairment) on disability-free years.

RESULTS

The average disability free years were 4.0 out of a possible 6 years. Severe obstruction was associated with 1 fewer disability-free year compared to normal spirometry in the adjusted model. For the 1,048 participants with airway obstruction, both respiratory factors (FEV1 and dyspnea) and non-respiratory factors (heart disease, coronary artery disease, diabetes, depression, osteoporosis, cognitive function, and weakness) were associated with decreased disability-free years.

CONCLUSIONS

Severe obstruction is associated with greater disability compared to patients with normal spirometery. Both respiratory and non-respiratory factors contribute to disability in older adults with abnormal spirometry.

Qualification of standard membrane-feeding assay with Plasmodium falciparum malaria and potential improvements for future assays

Vaccines that interrupt malaria transmission are of increasing interest and a robust functional assay to measure this activity would promote their development by providing a biologically relevant means of evaluating potential vaccine candidates. Therefore, we aimed to qualify the standard membrane-feeding assay (SMFA). The assay measures the transmission-blocking activity of antibodies by feeding cultured P. falciparum gametocytes to Anopheles mosquitoes in the presence of the test antibodies and measuring subsequent mosquito infection. The International Conference on Harmonisation (ICH) Harmonised Tripartite Guideline Q2(R1) details characteristics considered in assay validation. Of these characteristics, we decided to qualify the SMFA for Precision, Linearity, Range and Specificity. The transmission-blocking 4B7 monoclonal antibody was tested over 6 feeding experiments at several concentrations to determine four suitable concentrations that were tested in triplicate in the qualification experiments (3 additional feeds) to evaluate Precision, Linearity and Range. For Specificity, 4B7 was tested in the presence of normal mouse IgG. We determined intra- and inter-assay variability of % inhibition of mean oocyst intensity at each concentration of 4B7 (lower concentrations showed higher variability). We also showed that % inhibition was dependent on 4B7 concentration and the activity is specific to 4B7. Since obtaining empirical data is time-consuming, we generated a model using data from all 9 feeds and simulated the effects of different parameters on final readouts to improve the assay procedure and analytical methods for future studies. For example, we estimated the effect of number of mosquitoes dissected on variability of % inhibition, and simulated the relationship between % inhibition in oocyst intensity and % inhibition of prevalence of infected mosquitos at different mean oocysts in the control. SMFA is one of the few biological assays used in preclinical and early clinical development of transmission-blocking vaccines, and this study strongly supports its further development and application.

A chemiluminescent-western blot assay for quantitative detection of Plasmodium falciparum circumsporozoite protein

Highly sensitive and reliable assays based on the quantitation of immunologically relevant component(s) in recombinant or whole parasite-based vaccines would facilitate pre-clinical and clinical phases and the monitoring of malaria vaccine deployment. Here we report a laboratory-grade Western Blot assay for quantitative detection of Plasmodium falciparum circumsporozoite protein (PfCSP) in P. falciparum sporozoite (PfSPZ) and in recombinant (rPfCSP) product. This assay is based on the immuno-reactivity of an anti-P. falciparum CSP monoclonal antibody (mAb 2A10) with the NANP-repeat units on PfCSP. The antigen-antibody complex is detected by reaction with a commercially obtained chemiluminescence-linked Immunodetection system. The linear range for detecting the recombinant P. falciparum CSP (rPfCSP) in this assay is 3-12pg (R(2)=0.9399). The range for detecting the day 15 salivary-gland PfSPZ is between 0.0625 and 1 parasite (R(2)=0.9448) and approximately 10.0pg of PfCSP was detected on each sporozoite. The assay was highly reproducible in measuring the PfCSP on PfSPZ. The inter-assay Coefficient of Variation (CV%) was 10.31% while the intra-assay CV% on three different days was 6.05%, 2.03% and 1.42% respectively. These results suggest that this ECL-WB assay is highly sensitive and robust with a low degree of inter-assay and intra-assay variations. To our knowledge, this is the most sensitive immunoassay for the detection of a recombinant or native malarial protein and may have a wider range of applications including the quantification of immunological component(s) in a vaccine formulation, determination of the antigenic integrity in adjuvanted-vaccine and in stability studies. In addition, this assay can be applied to measure the mosquito infectivity in malaria transmission areas and to determine the effects of intervention measures on malaria transmission.

Mosquito feeding assays to determine the infectiousness of naturally infected Plasmodium falciparum gametocyte carriers

Introduction

In the era of malaria elimination and eradication, drug-based and vaccine-based approaches to reduce malaria transmission are receiving greater attention. Such interventions require assays that reliably measure the transmission of Plasmodium from humans to Anopheles mosquitoes.

Methods

We compared two commonly used mosquito feeding assay procedures: direct skin feeding assays and membrane feeding assays. Three conditions under which membrane feeding assays are performed were examined: assays with i) whole blood, ii) blood pellets resuspended with autologous plasma of the gametocyte carrier, and iii) blood pellets resuspended with heterologous control serum.

Results

930 transmission experiments from Cameroon, The Gambia, Mali and Senegal were included in the analyses. Direct skin feeding assays resulted in higher mosquito infection rates compared to membrane feeding assays (odds ratio 2.39, 95% confidence interval 1.94–2.95) with evident heterogeneity between studies. Mosquito infection rates in membrane feeding assays and direct skin feeding assays were strongly correlated (p<0.0001). Replacing the plasma of the gametocyte donor with malaria naïve control serum resulted in higher mosquito infection rates compared to own plasma (OR 1.92, 95% CI 1.68–2.19) while the infectiousness of gametocytes may be reduced during the replacement procedure (OR 0.60, 95% CI 0.52–0.70).

Conclusions

Despite a higher efficiency of direct skin feeding assays, membrane feeding assays appear suitable tools to compare the infectiousness between individuals and to evaluate transmission-reducing interventions. Several aspects of membrane feeding procedures currently lack standardization; this variability makes comparisons between laboratories challenging and should be addressed to facilitate future testing of transmission-reducing interventions.

Proteomic identification of host and parasite biomarkers in saliva from patients with uncomplicated Plasmodium falciparum malaria

Background

Malaria cases attributed to Plasmodium falciparum account for approximately 600,000 deaths yearly, mainly in African children. The gold standard method to diagnose malaria requires the visualization of the parasite in blood. The role of non-invasive diagnostic methods to diagnose malaria remains unclear.

Methods

A protocol was optimized to deplete highly abundant proteins from saliva to improve the dynamic range of the proteins identified and assess their suitability as candidate biomarkers of malaria infection. A starch-based amylase depletion strategy was used in combination with four different lectins to deplete glycoproteins (Concanavalin A and Aleuria aurantia for N-linked glycoproteins; jacalin and peanut agglutinin for O-linked glycoproteins). A proteomic analysis of depleted saliva samples was performed in 17 children with fever and a positive–malaria slide and compared with that of 17 malaria-negative children with fever.

Results

The proteomic signature of malaria-positive patients revealed a strong up-regulation of erythrocyte-derived and inflammatory proteins. Three P. falciparum proteins, PFL0480w, PF08_0054 and PFI0875w, were identified in malaria patients and not in controls. Aleuria aurantia and jacalin showed the best results for parasite protein identification.

Conclusions

This study shows that saliva is a suitable clinical specimen for biomarker discovery. Parasite proteins and several potential biomarkers were identified in patients with malaria but not in patients with other causes of fever. The diagnostic performance of these markers should be addressed prospectively.

Quantitative detection of Plasmodium falciparum DNA in saliva, blood, and urine

BACKGROUND

Current methods for detecting malaria parasites are invasive and associated with poor compliance when repeated sampling is required. New methods to detect and quantify parasites in a less-invasive manner would greatly enhance the potential for longitudinal surveillance in clinical trials.

METHODS

Saliva, urine, and blood samples from 386 Gambian outpatients with suspected malaria infections were analyzed by nested polymerase chain reaction (nPCR) to detect infection and to evaluate diagnostic accuracy in comparison to expert microscopy. The amount of parasite DNA in malaria-positive samples was estimated using real-time quantitative PCR (qPCR).

RESULTS

Blood parasite density as estimated by qPCR correlated well with parasite counts established by microscopy (p = 0.94; P < .001). qPCR results for saliva had a significant correlation with microscopy counts (p = 0.58; P < .001), whereas qPCR results for urine had a positive but poor correlation with microscopy counts (p = 0.20; P = .117). The mean amounts of parasite DNA quantified in blood were greater than the mean amounts quantified in saliva and urine samples obtained concurrently from the same individual, by approximately 600-fold and approximately 2500-fold, respectively. When nPCR results were compared with microscopy results, nPCR of saliva had a sensitivity of 73% and a specificity of 97%; its sensitivity increased to 82% in samples with a parasite density of > or = 1000 parasites/microL. nPCR of urine had a sensitivity of 32% and a specificity of 98%.

CONCLUSION

Saliva sampling is a promising less-invasive approach for detecting malaria infection.

Seasonal variation in fruit and vegetable consumption in a rural agricultural community

BACKGROUND

Seasonal variation in fruit and vegetable consumption has been documented in a limited number of previous investigations and is important for the design of epidemiologic investigations and in the evaluation of intervention programs.

OBJECTIVE

This study investigates fruit and vegetable consumption behaviors among Hispanic farmworkers and non-farmworkers in a rural agricultural community.

DESIGN

A larger study recruited 101 farmworker families and 100 non-farmworker families from the Yakima Valley in Washington State between December 2004 and October 2005. All families were Hispanic. An in-person administered questionnaire collected information on consumption of locally grown fruits and vegetables and sources of obtaining fruits and vegetables. Data on dietary intake asked whether or not the respondent had consumed a given fruit or vegetable in the past month. Data were collected longitudinally, coinciding with three agricultural seasons: thinning (summer), harvest (fall), and nonspray (winter).

STATISTICAL ANALYSES PERFORMED

Generalized estimating equations were used to test for statistical significance between proportions of the population who consumed a given fruit or vegetable across agricultural seasons. Multivariable logistic regression was performed and corresponding odds ratios and 95% confidence intervals are reported.

RESULTS

The proportion of respondents who ate apples, pears, plums, peaches, apricots, peppers, corn, and cucumbers was highest in the fall harvest season, whereas the proportions of those who ate cherries and asparagus were highest in the summer thinning season. Compared to non-farmworkers, a higher proportion of farmworkers reported having eaten peaches, apricots, cherries, green beans, carrots, peppers, corn, pumpkin, squash, and onions, in the past month.

CONCLUSIONS

Epidemiologic investigations and public health interventions that examine the consumption of fruits and vegetables should consider seasonal variation in consumption patterns, especially in agricultural communities.