Acquisition of Growth-Inhibitory Antibodies against Blood-Stage Plasmodium falciparum

Background: Antibodies that inhibit the growth of blood-stage Plasmodium falciparum may play an important role in acquired and vaccine-induced immunity in humans. However, the acquisition and activity of these antibodies is not well understood. Methods: We tested dialysed serum and purified immunoglobulins from Kenyan children and adults for inhibition of P. falciparum blood-stage growth in vitro using different parasite lines. Serum antibodies were measured by ELISA to bloodstage parasite antigens, extracted from P. falciparum schizonts, and to recombinant merozoite surface protein 1 (42 kDa Cterminal fragment, MSP1-42). Results: Antibodies to blood-stage antigens present in schizont protein extract and to recombinant MSP1-42 significantly increased with age and were highly correlated. In contrast, growth-inhibitory activity was not strongly associated with age and tended to decline marginally with increasing age and exposure, with young children demonstrating the highest inhibitory activity. Comparison of growth-inhibitory activity among samples collected from the same population at different time points suggested that malaria transmission intensity influenced the level of growth-inhibitory antibodies. Antibodies to recombinant MSP1-42 were not associated with growth inhibition and high immunoglobulin G levels were poorly predictive of inhibitory activity. The level of inhibitory activity against different isolates varied. Conclusions: Children can acquire growth-inhibitory antibodies at a young age, but once they are acquired they do not appear to be boosted by on-going exposure. Inhibitory antibodies may play a role in protection from early childhood malaria

Diet-associated inflammation modulates inflammation and WNT signaling in the rectal mucosa, and the response to supplementation with dietary fiber

Inflammation drives colorectal cancer development, and colorectal cancer risk is influenced by dietary factors, including dietary fiber. Hyperactive WNT signaling occurs in colorectal cancer and may regulate inflammation. This study investigated (i) relationships between the inflammatory potential of diet, assessed using the Energy-adjusted Dietary Inflammatory Index (E-DII), and markers of WNT signaling, and (ii) whether DII status modulated the response to supplementation with two types of dietary fiber. Seventy-five healthy participants were supplemented with resistant starch and/or polydextrose (PD) or placebo for 50 days. Rectal biopsies were collected before and after intervention and used to assess WNT pathway gene expression and crypt cell proliferation. E-DII scores were calculated from food frequency questionnaire data. High-sensitivity C-reactive protein (hsCRP) and fecal calprotectin concentrations were quantified. hsCRP concentration was significantly greater in participants with higher E-DII scores [least square means (LSM) 4.7 vs. 2.4 mg/L, P = 0.03]. Baseline E-DII score correlated with FOSL1 (b = 0.503, P = 0.003) and WNT11 (b = 0.472, P = 0.006) expression, after adjusting for age, gender, body mass index, endoscopy procedure, and smoking status. WNT11 expression was more than 2-fold greater in individuals with higher E-DII scores (LSM 0.131 vs. 0.059, P = 0.002). Baseline E-DII modulated the effects of PD supplementation on FOSL1 expression (P = 0.04). More proinflammatory diets were associated with altered WNT signaling and appeared to modulate the effects of PD supplementation on expression of FOSL1. This is the first study to investigate relationships between the E-DII and molecular markers of WNT signaling in rectal tissue of healthy individuals

Protocol for the IDEAL-2 longitudinal study: Following the experiences of people with dementia and their primary carers to understand what contributes to living well with dementia and enhances active life

Background There is a major need for longitudinal research examining the experiences of people with dementia and their primary carers, as relatively little is known about how the factors associated with capability to ‘live well’ vary over time. The main aim of the IDEAL-2 study is to investigate how and why, over time, people with dementia and their primary carers might vary in their capability to live well with dementia, whilst exploring both their use of health and care services and their unmet needs. Methods IDEAL-2 will build on the Improving the experience of Dementia and Enhancing Active Life (IDEAL) cohort of 1547 people (who, at recruitment between July 2014 and July 2016, had mild-to-moderate dementia), and their 1283 primary carers in Great Britain. The existing cohort will be enriched with additional participants with mild-to-moderate dementia (and their primary carers where available and willing) from the following groups: people with rarer forms of dementia, and/or those who are ≥90 years or < 65 years of age at time of recruitment. We will assess the primary outcome, capability to live well with dementia, and the factors influencing it using questionnaires at yearly intervals for 3 years. Additionally, we will seek to link the cohort data with administrative data to obtain information about health service use. Some participants will be invited for in-depth face-to-face interviews. The cohort study will be supplemented by linked research focusing on: the co-production of new measures of living well; including the perspectives of people with advanced dementia living in residential care settings; including people with dementia from black, Asian, and minority ethnic groups; and understanding the experience of people living with undiagnosed dementia. Discussion IDEAL-2 will provide evidence about the key indicators of, and factors associated with, living well over the course of dementia and how these differ for particular subgroups. It will tell us which combinations of services and support are most beneficial and cost-effective. Moreover, the IDEAL-2 study will gather evidence from under-researched groups of people with dementia, who are likely to have their own distinct perceptions of living well.Alzheimer’s Society & The University of Exete

Effect of Hydrocortisone on Mortality and Organ Support in Patients With Severe COVID-19: The REMAP-CAP COVID-19 Corticosteroid Domain Randomized Clinical Trial.

Importance: Evidence regarding corticosteroid use for severe coronavirus disease 2019 (COVID-19) is limited. Objective: To determine whether hydrocortisone improves outcome for patients with severe COVID-19. Design, Setting, and Participants: An ongoing adaptive platform trial testing multiple interventions within multiple therapeutic domains, for example, antiviral agents, corticosteroids, or immunoglobulin. Between March 9 and June 17, 2020, 614 adult patients with suspected or confirmed COVID-19 were enrolled and randomized within at least 1 domain following admission to an intensive care unit (ICU) for respiratory or cardiovascular organ support at 121 sites in 8 countries. Of these, 403 were randomized to open-label interventions within the corticosteroid domain. The domain was halted after results from another trial were released. Follow-up ended August 12, 2020. Interventions: The corticosteroid domain randomized participants to a fixed 7-day course of intravenous hydrocortisone (50 mg or 100 mg every 6 hours) (n = 143), a shock-dependent course (50 mg every 6 hours when shock was clinically evident) (n = 152), or no hydrocortisone (n = 108). Main Outcomes and Measures: The primary end point was organ support-free days (days alive and free of ICU-based respiratory or cardiovascular support) within 21 days, where patients who died were assigned -1 day. The primary analysis was a bayesian cumulative logistic model that included all patients enrolled with severe COVID-19, adjusting for age, sex, site, region, time, assignment to interventions within other domains, and domain and intervention eligibility. Superiority was defined as the posterior probability of an odds ratio greater than 1 (threshold for trial conclusion of superiority >99%). Results: After excluding 19 participants who withdrew consent, there were 384 patients (mean age, 60 years; 29% female) randomized to the fixed-dose (n = 137), shock-dependent (n = 146), and no (n = 101) hydrocortisone groups; 379 (99%) completed the study and were included in the analysis. The mean age for the 3 groups ranged between 59.5 and 60.4 years; most patients were male (range, 70.6%-71.5%); mean body mass index ranged between 29.7 and 30.9; and patients receiving mechanical ventilation ranged between 50.0% and 63.5%. For the fixed-dose, shock-dependent, and no hydrocortisone groups, respectively, the median organ support-free days were 0 (IQR, -1 to 15), 0 (IQR, -1 to 13), and 0 (-1 to 11) days (composed of 30%, 26%, and 33% mortality rates and 11.5, 9.5, and 6 median organ support-free days among survivors). The median adjusted odds ratio and bayesian probability of superiority were 1.43 (95% credible interval, 0.91-2.27) and 93% for fixed-dose hydrocortisone, respectively, and were 1.22 (95% credible interval, 0.76-1.94) and 80% for shock-dependent hydrocortisone compared with no hydrocortisone. Serious adverse events were reported in 4 (3%), 5 (3%), and 1 (1%) patients in the fixed-dose, shock-dependent, and no hydrocortisone groups, respectively. Conclusions and Relevance: Among patients with severe COVID-19, treatment with a 7-day fixed-dose course of hydrocortisone or shock-dependent dosing of hydrocortisone, compared with no hydrocortisone, resulted in 93% and 80% probabilities of superiority with regard to the odds of improvement in organ support-free days within 21 days. However, the trial was stopped early and no treatment strategy met prespecified criteria for statistical superiority, precluding definitive conclusions. Trial Registration: ClinicalTrials.gov Identifier: NCT02735707

Variation in use of erythrocyte invasion pathways by Plasmodium falciparum mediates evasion of human inhibitory antibodies

Antibodies that inhibit Plasmodium falciparum invasion of erythrocytes are believed to be an important component of immunity against malaria. During blood-stage infection, P. falciparum can use different pathways for erythrocyte invasion by varying the expression and/or utilization of members of 2 invasion ligand families: the erythrocyte-binding antigens (EBAs) and reticulocyte-binding homologs (PfRhs). Invasion pathways can be broadly classified into 2 groups based on the use of sialic acid (SA) on the erythrocyte surface by parasite ligands. We found that inhibitory antibodies are acquired by malaria-exposed Kenyan children and adults against ligands of SA-dependent and SA-independent invasion pathways, and the ability of antibodies to inhibit erythrocyte invasion depended on the pathway used by P. falciparum isolates. Differential inhibition of P. falciparum lines that varied in their use of specific EBA and PfRh proteins pointed to these ligand families as major targets of inhibitory antibodies. Antibodies against recombinant EBA and PfRh proteins were acquired in an age-associated manner, and inhibitory antibodies against EBA175 appeared prominent among some individuals. These findings suggest that variation in invasion phenotype might have evolved as a mechanism that facilitates immune evasion by P. falciparum and that a broad inhibitory response against multiple ligands may be required for effective immunity

Prevalence of antibodies to AMA1 or specific epitopes by age group in the Chonyi cohort.

<p>Antibodies to recombinant AMA1 protein were tested by standard ELISA. Antibodies to specific AMA1 epitopes were measured by assessing the ability of human serum antibodies to inhibit the binding of monoclonal antibodies 1F9 and 2C5 in competition ELISA. (<b>A</b>) IgG to recombinant AMA1 (P&lt;0.001), (<b>B</b>) inhibition of binding of mAb 1F9 epitope (P&lt;0.001), (<b>C</b>) inhibition of binding of mAb 2C5 (P = 0.028). P values were calculated using the Chi square test for trend excluding age 0 (&lt;1) years. Data represent the proportion of individuals with detectable IgG binding or inhibitory activity and error bars indicate 95% CI.</p

Association between antibody responses and risk of clinical malaria in the Chonyi cohort.

<p>Notes.</p>1<p>Children were classified as high and low responders for antibodies based on being above or below the median level for the cohort.</p>2<p>Multivariable Cox proportional hazards adjusted for age.</p>3<p>Hazard ratios show the risk of <i>P. falciparum</i> malaria over a 6 month follow-up period comparing children who were high or low antibody responders to each antigen or epitope.</p>4<p>Parasitemia detected by light microscopy.</p

Levels of inhibition of 1F9-binding by human antibodies according to age group and infection status in the Ngerenya cohort.

<p>Values show the level of inhibition of 1F9 mAb binding to AMA1 by human serum antibodies, stratified by infection status at the time of sample collection and grouped according to age. Boxes indicate median and interquartile range, and whiskers represent 95% CI. Positive 1F9 inhibition was defined as inhibition of 1F9 binding&gt;(mean +2 standard deviations of negative controls = 6.19%). Differences in the level of anti-1F9 activity among age groups was significant amongst aparasitemic individuals (P = 0.020, Kruskal Wallis test), but not amongst parasitemic individuals. The median level of anti-1F9 activity was lower amongst aparasitemic compared to parasitemic individuals (median inhibition [IQR] −0.1% [−2.8–1.7] vs 4.3% [−1.0–13.2], P = 0.002, Mann Whitney U test).</p

Combined antibody responses to AMA1 and the risk of clinical malaria in the Chonyi cohort.

<p>Notes.</p>1<p>Children were classified as high and low responders for antibodies based on being above or below the median level for the cohort. Analysis compared children who were high responders to both antigens versus those who were low responders to both.</p>2<p>Multivariable Cox proportional hazards adjusted for age.</p>3<p>Hazard ratios show the risk of <i>P. falciparum</i> malaria over a 6 month follow-up period.</p

Immunoglobulin G Subclass-Specific Responses against Plasmodium falciparum Merozoite Antigens Are Associated with Control of Parasitemia and Protection from Symptomatic Illness▿ †

Substantial evidence indicates that antibodies to Plasmodium falciparum merozoite antigens play a role in protection from malaria, although the precise targets and mechanisms mediating immunity remain unclear. Different malaria antigens induce distinct immunoglobulin G (IgG) subclass responses, but the importance of different responses in protective immunity from malaria is not known and the factors determining subclass responses in vivo are poorly understood. We examined IgG and IgG subclass responses to the merozoite antigens MSP1-19 (the 19-kDa C-terminal region of merozoite surface protein 1), MSP2 (merozoite surface protein 2), and AMA-1 (apical membrane antigen 1), including different polymorphic variants of these antigens, in a longitudinal cohort of children in Papua New Guinea. IgG1 and IgG3 were the predominant subclasses of antibodies to each antigen, and all antibody responses increased in association with age and exposure without evidence of increasing polarization toward one subclass. The profiles of IgG subclasses differed somewhat for different alleles of MSP2 but not for different variants of AMA-1. Individuals did not appear to have a propensity to make a specific subclass response irrespective of the antigen. Instead, data suggest that subclass responses to each antigen are generated independently among individuals and that antigen properties, rather than host factors, are the major determinants of IgG subclass responses. High levels of AMA-1-specific IgG3 and MSP1-19-specific IgG1 were strongly predictive of a reduced risk of symptomatic malaria and high-density P. falciparum infections. However, no antibody response was significantly associated with protection from parasitization per se. Our findings have major implications for understanding human immunity and for malaria vaccine development and evaluation