An ELISA method to compute endpoint titers to Epstein-Barr virus and cytomegalovirus: application to population-based studies

ELISA-R: an R-based method for robust ELISA data analysis

Enzyme-linked immunosorbent assay (ELISA) is a technique to detect the presence of an antigen or antibody in a sample. ELISA is a simple and cost-effective method that has been used for evaluating vaccine efficacy by detecting the presence of antibodies against viral/bacterial antigens and diagnosis of disease stages. Traditional ELISA data analysis utilizes a standard curve of known analyte, and the concentration of the unknown sample is determined by comparing its observed optical density against the standard curve. However, in the case of vaccine research for complicated bacteria such as Mycobacterium tuberculosis (Mtb), there is no prior information regarding the antigen against which high-affinity antibodies are generated and therefore plotting a standard curve is not feasible. Consequently, the analysis of ELISA data in this instance is based on a comparison between vaccinated and unvaccinated groups. However, to the best of our knowledge, no robust data analysis method exists for "non-standard curve" ELISA. In this paper, we provide a straightforward R-based ELISA data analysis method with open access that incorporates end-point titer determination and curve-fitting models. Our modified method allows for direct measurement data input from the instrument, cleaning and arranging the dataset in the required format, and preparing the final report with calculations while leaving the raw data file unchanged. As an illustration of our method, we provide an example from our published data in which we successfully used our method to compare anti-Mtb antibodies in vaccinated vs non-vaccinated mice.

Anti-cytomegalovirus antibody levels stratify human immune profiles across the lifespan

Human cytomegalovirus (hCMV) is a ubiquitous latent persistent herpesvirus infecting 60-90% of the population worldwide. hCMV carriage in immunocompetent people is asymptomatic; thus, hCMV can be considered a component of normative aging. However, hCMV powerfully modulates many features of the immune, and likely other, systems and organs. Questions remain as to how hCMV carriage affects the human host. We used anti-CMV antibody titers as a stratifying criterion to examine the impact of "intensity" of hCMV infection as a potential biomarker of aging, inflammation, and immune homeostasis in a cohort of 247 participants stratified into younger (21-40 years) and older (> 65 years of age) groups. We showed that anti-CMV antibody titers increased with age and directly correlated to increased levels of soluble tumor necrosis factor (sTNFR) I in younger but not older participants. CD8 + cell numbers were reduced in the older group due to the loss in CD8 + T naïve (Tn) cells. In CMV carriers and, in particular, in anti-CMV Ab-high participants, this loss was mitigated or reversed by an increase in the numbers of CD8 + T effector memory (Tem) and T effector memory reexpressing CD45RA (Temra) cells. Analysis of CD38, HLA-DR, and CD57 expression revealed subset (CD4 or CD8)-specific changes that correlated with anti-CMV Ab levels. In addition, anti-CMV Ab levels predicted anti-CMV CD8 T cell responsiveness to different CMV open reading frames (ORFs) selectively in older participants, which correlated to the transcriptional order of expression of specific CMV ORFs. Implications of these results for the potential predictive value of anti-CMV Ab titers during aging are discussed.

Dietary yeast beta 1,3/1,6 glucan supplemented to adult Labrador Retrievers alters peripheral blood immune cell responses to vaccination challenge without affecting protective immunity

Yeast-derived 1,3/1,6 β-glucans may alter host immunity to produce robust and quickly resolved responses that align with companion animal health goals. In adult dogs, immunomodulation by yeast 1,3/1,6 β-glucans in extruded kibble diet have not been well documented. The study objective was to evaluate systemic immune responses in dogs fed kibble diets with two yeast 1,3/1,6 β-glucans doses before and after vaccine challenge. Twenty-four adult Labrador Retrievers were assigned to three dietary treatments consisting of a basal diet (control) supplemented with 0.012% or 0.023% (0.5 or 1×, respectively) yeast 1,3/1,6 β-glucan with equal sex representation within each treatment (8 dogs/diet). Animals were fed experimental diets for a 29-d acclimation period, after which baseline blood samples were collected before administration of a combination canine distemper virus, parvovirus, and adenovirus-2 vaccine. Blood samples were collected weekly for 21 d following vaccination with whole blood for CBC analysis, serum for titer and cytokine assays, and peripheral blood mononuclear cells (PBMC) isolated for flow cytometric immune cell profiling. Data were analyzed using the MIXED procedure with diet and timepoint fixed effects. Serum titer was analyzed by Kruskal-Wallis test (SAS 9.4; P ≤ 0.05). Prior to vaccination, β-glucan diets did not affect serum cytokines, antibody titer, or immune cell populations. In the first 7 d post-vaccination (dpv), PBMC CD21low B cells increased 36.5% to 58.1% in all groups but the magnitude of change was lesser in the 0.5× β-glucan diet resulting in 25.6% lower CD21low populations compared to control-fed dogs (P = 0.007). By 21 dpv, B-cell populations recovered to baseline levels in dogs fed 1× β-glucan, but CD21high cells remained elevated 50.5% in dogs fed 0.5× β-glucan diets compared with baseline (P < 0.0001). While no differences in serum titer or cytokines were observed, feeding both β-glucan diets maintained stable blood monocytes, whereas a 53.0% decrease between baseline and 14 dpv was observed in control-fed dogs (P = 0.01). Collectively, these outcomes suggest that a 1× dose of 1,3/1,6 yeast β-glucan in extruded kibble diets altered monocytes associated with trained immunity, did not reduce PBMC CD21low B-cell responsiveness, and simultaneously contributed to B-cell population resolution by 21 dpv in adult dogs. Additional research to assess the functionality of these changes is needed.

Inflammatory and immune markers in HIV-infected older adults on long-term antiretroviral therapy: Persistent elevation of sCD14 and of proinflammatory effector memory T cells

HIV-positive patients whose viral loads are successfully controlled by active antiretroviral therapy (ART) show no clinical signs of AIDS. However, their lifespan is shorter compared with individuals with no HIV infection and they prematurely exhibit a multitude of chronic diseases typically associated with advanced age. It was hypothesized that immune system aging may correlate with, and provide useful biomarkers for, this premature loss of healthspan in HIV-positive subjects. Here, we tested whether the immune correlates of aging, including cell numbers and phenotypes, inflammatory status, and control of human cytomegalovirus (hCMV) in HIV-positive subjects on long-term successful ART (HIV+) may reveal increased "immunological age" compared with HIV-negative, age-matched cohort (HIV-) in participants between 50 and 69 years of age. Specifically, we expected that younger HIV+ subjects may immunologically resemble older individuals without HIV. We found no evidence to support this hypothesis. While T cells from HIV+ participants displayed differential expression in several differentiation and/or inhibitory/exhaustion markers in different T cell subpopulations, aging by a decade did not pronounce these changes. Similarly, while the HIV+ participants exhibited higher T cell responses and elevated inflammatory marker levels in plasma, indicative of chronic inflammation, this trait was not age-sensitive. We did find differences in immune control of hCMV, and, more importantly, a sustained elevation of sCD14 and of proinflammatory CD4 and CD8 T cell responses across age groups, pointing towards uncontrolled inflammation as a factor in reduced healthspan in successfully treated older HIV+ patients.

Diminished Cellular Immunity and Executive Cognitive Functioning Among Middle-Aged and Elderly Adults

OBJECTIVE

Within the field of psychoneuroimmunology, much attention has been given to immune dysregulation and its impact on cognitive functioning. Some of this work has focused on the association between high levels of basal proinflammatory cytokines and poorer performance on measures of executive functioning; however, effect sizes have been quite small in human studies.

METHODS

We investigated whether Epstein-Barr virus (EBV) antibody titers, a marker of immune dysregulation related to cellular immunity, may be associated with executive functioning while also attempting to replicate prior studies using two markers of proinflammatory cytokine production (i.e., circulating and lipopolysaccharide [LPS]-stimulated cytokines [interleukin 6, interleukin 1β, interferon-γ]). A total of 71 community-dwelling adults (mean [standard deviation] age = 60.87 [6.26] years) who were seropositive for EBV infection participated in the study.

RESULTS

Findings indicated that greater EBV antibody titers were associated with poorer performance on measures of the executive functions of inhibition ( B = -2.36, standard error = 1.06, p = .028) and cognitive flexibility ( B = -2.89, standard error = 1.13, p = .013) when including circulating and LPS-stimulated cytokines and other relevant covariates (i.e., age, sex, and body mass index) in linear regression analyses. Neither circulating nor LPS-stimulated cytokines were associated with performance on the cognitive tasks in the regression analyses.

CONCLUSIONS

These results suggest that EBV antibody titers may be an indicator of immune dysregulation that is more relevant to executive functioning performance than either circulating or stimulated proinflammatory cytokines among community-dwelling adults.

Racial and Economic Adversity Differences in Stress Markers and Immune Function Among Urban Adolescents

BACKGROUND

Exposure to racism and associated adversities, such as poverty, is hypothesized to contribute to racial inequities in health via stress and immune pathways. Furthermore, the effects of adversity may be more salient during sensitive developmental periods. Our study examined racial differences in stress and immune biomarkers during adolescence and the effects of exposure to economic adversity at distinct developmental time periods and cumulatively in accounting for potential racial differences.

METHODS

Secondary analysis of the Adolescent Health and Development in Context study was conducted. Data were derived from self-administered surveys; interviews; smartphone-based, geographic-explicit ecological momentary assessment; stress biomarkers (evening salivary cortisol over six nights and hair cortisol); and immune biomarkers (salivary shedding of Epstein-Barr virus [EBV] DNA among EBV-positive adolescents). Current socioeconomic status measures included annual household income and caregiver education. Caregivers also reported experiences of bankruptcy, difficulty paying bills, receipt of food stamps/Supplemental Nutrition Assistance Program/electronic benefit transfer, and job loss when the child was of ages birth-5 years, 6-10 years, and 11 years or older. An affirmative response to any item was defined as exposure to economic adversity for that developmental time period (yes/no). A cumulative economic adversity measure was calculated as the sum of exposures across developmental periods (0 = never exposed to 3 = exposed across all time periods). Descriptive and multivariable regression analyses were conducted, accounting for covariates.

RESULTS

Black/African American adolescents had higher salivary cortisol concentration, higher hair cortisol concentration, and an increased odd of salivary shedding of EBV DNA compared to White adolescents. Racial differences were not attenuated by the current socioeconomic status or economic adversity (developmental period or cumulatively).

DISCUSSION

Our study provides evidence that stress and immune biomarkers differ by race as early as adolescence and may be one pathway through which racism and associated adversities contribute to racial health inequities. Further research on the contribution of multiple adversities beyond poverty to racial inequities in physiological stress and health is critical for informing effective prevention and intervention efforts.

An automated approach to determine antibody endpoint titers for COVID-19 by an enzyme-linked immunosorbent assay

While a variety of therapeutic options continue to emerge for COVID-19 treatment, convalescent plasma (CP) has been used as a possible treatment option early in the pandemic. One of the most significant challenges with CP therapy, however, both when defining its efficacy and implementing its approach clinically, is accurately and efficiently characterizing an otherwise heterogenous therapeutic treatment. Given current limitations, our goal is to leverage a SARS antibody testing platform with a newly developed automated endpoint titer analysis program to rapidly define SARS-CoV-2 antibody levels in CP donors and hospitalized patients. A newly developed antibody detection platform was used to perform a serial dilution enzyme-linked immunosorbent assay (ELISA) for immunoglobulin (Ig)G, IgM, and IgA SARS-CoV-2 antibodies. Data were then analyzed using commercially available software, GraphPad Prism, or a newly developed program developed in Python called TiterScape, to analyze endpoint titers. Endpoint titer calculations and analysis times were then compared between the two analysis approaches. Serial dilution analysis of SARS-CoV-2 antibody levels revealed a high level of heterogeneity between individuals. Commercial platform analysis required significant time for manual data input and extrapolated endpoint titer values when the last serial dilution was above the endpoint cutoff, occasionally producing erroneously high results. By contrast, TiterScape processed 1008 samples for endpoint titer results in roughly 14 minutes compared with the 8 hours required for the commercial software program analysis. Equally important, results generated by TiterScape and Prism were highly similar, with differences averaging 1.26 ± 0.2 percent (mean ± SD). The pandemic has created unprecedented challenges when seeking to accurately test large numbers of individuals for SARS-CoV-2 antibody levels with a rapid turnaround time. ELISA platforms capable of serial dilution analysis coupled with a highly flexible software interface may provide a useful tool when seeking to define endpoint titers in a high-throughput manner. Immunohematology 2021;37:33-43.

While a variety of therapeutic options continue to emerge for COVID-19 treatment, convalescent plasma (CP) has been used as a possible treatment option early in the pandemic. One of the most significant challenges with CP therapy, however, both when defining its efficacy and implementing its approach clinically, is accurately and efficiently characterizing an otherwise heterogenous therapeutic treatment. Given current limitations, our goal is to leverage a SARS antibody testing platform with a newly developed automated endpoint titer analysis program to rapidly define SARS-CoV-2 antibody levels in CP donors and hospitalized patients. A newly developed antibody detection platform was used to perform a serial dilution enzyme-linked immunosorbent assay (ELISA) for immunoglobulin (Ig)G, IgM, and IgA SARS-CoV-2 antibodies. Data were then analyzed using commercially available software, GraphPad Prism, or a newly developed program developed in Python called TiterScape, to analyze endpoint titers. Endpoint titer calculations and analysis times were then compared between the two analysis approaches. Serial dilution analysis of SARS-CoV-2 antibody levels revealed a high level of heterogeneity between individuals. Commercial platform analysis required significant time for manual data input and extrapolated endpoint titer values when the last serial dilution was above the endpoint cutoff, occasionally producing erroneously high results. By contrast, TiterScape processed 1008 samples for endpoint titer results in roughly 14 minutes compared with the 8 hours required for the commercial software program analysis. Equally important, results generated by TiterScape and Prism were highly similar, with differences averaging 1.26 ± 0.2 percent (mean ± SD). The pandemic has created unprecedented challenges when seeking to accurately test large numbers of individuals for SARS-CoV-2 antibody levels with a rapid turnaround time. ELISA platforms capable of serial dilution analysis coupled with a highly flexible software interface may provide a useful tool when seeking to define endpoint titers in a high-throughput manner. Immunohematology 2021;37:33–43.

Relationship satisfaction determines the association between Epstein-Barr virus latency and somatic symptoms after the loss of a spouse

The loss of a spouse is associated with a host of negative health outcomes. While bereaved individuals commonly report somatic symptoms, no investigations exist of the association between reactivation of latent Epstein-Barr virus (EBV) and somatic symptoms among this population. Further, how an individual perceives the quality of their lost relationship in retrospect may impact loss outcomes. Among 99 bereaved spouses, elevated EBV antibody titers were associated with somatic symptoms for those who retrospectively reported high or mean levels of relationship satisfaction (RS), but not among those less satisfied. Further, higher RS was associated with greater grief symptoms. This study identifies higher retrospective RS as a possible risk factor for negative physical and mental health outcomes during bereavement.

Predictors of Epstein-Barr virus serostatus and implications for vaccine policy: A systematic review of the literature

BACKGROUND

Epstein-Barr virus (EBV) is an important human pathogen; it infects >90% people globally and is linked to infectious mononucleosis and several types of cancer. Vaccines against EBV are in development. In this study we present the first systematic review of the literature on risk factors for EBV infection, and discuss how they differ between settings, in order to improve our understanding of EBV epidemiology and aid the design of effective vaccination strategies.

METHODS

MEDLINE, Embase, and Web of Science were searched on 6th March 2017 for observational studies of risk factors for EBV infection. Studies were excluded if they were published before 2008 to ensure relevance to the modern day, given the importance of influencing future vaccination policies. There were no language restrictions. After title, abstract and full text screening, followed by checking the reference lists of included studies to identify further studies, data were extracted into standardised spreadsheets and quality assessed. A narrative synthesis was undertaken.

RESULTS

Seventy-seven papers met our inclusion criteria, including data from 31 countries. There was consistent evidence that EBV seroprevalence was associated with age, increasing throughout childhood and adolescence and remaining constant thereafter. EBV was generally acquired at younger ages in Asia than Europe/North America. There was also compelling evidence for an association between cytomegalovirus infection and EBV. Additional factors associated with EBV seroprevalence, albeit with less consistent evidence, included ethnicity, socioeconomic status, other chronic viral infections, and genetic variants of HLA and immune response genes.

CONCLUSIONS

Our study is the first systematic review to draw together the global literature on the risk factors for EBV infection and includes an evaluation of the quality of the published evidence. Across the literature, the factors examined are diverse. In Asia, early vaccination of infants would be required to prevent EBV infection. In contrast, in Western countries a vaccine could be deployed later, particularly if it has only a short duration of protection and the intention was to protect against infectious mononucleosis. There is a lack of high-quality data on the prevalence and age of EBV infection outside of Europe, North America and South-East Asia, which are essential for informing effective vaccination policies in these settings.

Performance of Zika Assays in the Context of Toxoplasma gondii, Parvovirus B19, Rubella Virus, and Cytomegalovirus (TORCH) Diagnostic Assays

Infections during pregnancy that may cause congenital abnormalities have been recognized for decades, but their diagnosis is challenging. This was again illustrated with the emergence of Zika virus (ZIKV), highlighting the inherent difficulties in estimating the extent of pre- and postnatal ZIKV complications because of the difficulties in establishing definitive diagnoses. We reviewed the epidemiology, infection kinetics, and diagnostic methods used for Toxoplasma gondii, parvovirus B19, rubella virus, and cytomegalovirus (TORCH) infections and compared the results with current knowledge of ZIKV diagnostic assays to provide a basis for the inclusion of ZIKV in the TORCH complex evaluations. Similarities between TORCH pathogens and ZIKV support inclusion of ZIKV as an emerging TORCH infection. Our review evaluates the diagnostic performance of various TORCH diagnostic assays for maternal screening, fetal screening, and neonatal screening. We show that the sensitivity, specificity, and positive and negative predictive value of TORCH complex pathogens are widely variable, stressing the importance of confirmatory testing and the need for novel techniques for earlier and accurate diagnosis of maternal and congenital infections. In this context it is also important to acknowledge different needs and access to care for different geographic and resource settings.

Sex differences in executive functioning and latent herpesvirus reactivation among bereaved and non-bereaved individuals

The death of a spouse is a highly stressful event. Better executive functioning has been shown to benefit men to a greater degree than women during stress. We evaluated potential sex differences in stress and immune dysregulation among control and bereaved participants who completed a self-report measure of perceived stress, neuropsychological measures of inhibition and updating/monitoring of information in working memory, and a blood draw to measure Epstein-Barr virus (EBV) antibody titres. Moderation analyses were conducted to test the hypothesis that better inhibition would be associated with less stress and immune dysregulation among male bereaved participants compared with female bereaved participants. Bereaved females demonstrated greater EBV antibody titres than bereaved males. Male bereaved participants benefited from better inhibition, as evidenced by fewer EBV antibody titres, whereas bereaved female participants did not. In the control group, males with high inhibition reported lower stress than males with low inhibition. Present study results are an important step towards identifying those at greatest risk of stress and poor health.

Church Attendance and CMV Herpes Virus Latency Among Bereaved and Non-Bereaved Adults

OBJECTIVE

There is widespread literature linking church attendance to physical health. However, little is known about the association of church attendance and the immune system, particularly during difficult life transitions. This study investigated the association between church attendance and CMV herpes-virus latency by assessing Cytomegalovirus (CMV) IgG antibody titers among bereaved and non-bereaved individuals.

METHODS

Participants included 44 bereaved individuals and 44 controls with a mean age of 68 (SD=12.84). CMV herpes-virus latency was measured using CMV IgG antibody titers. Church attendance was measured using three items from the Community Healthy Activities Model Program for Seniors (CHAMPS) Questionnaire.

RESULTS

After adjusting for participant's age, gender, education, minority status, weekly alcohol consumption, smoking, depression, body mass index (BMI) and comorbidities, church attendance was associated with lower CMV IgG antibody titers among bereaved and control participants. Further, there was a significant moderating effect of church attendance in the association between bereavement status and CMV IgG antibody titers, so that bereaved individuals attending church were found to have less herpes-virus reactivation (lower CMV IgG antibody titers) when compared to their bereaved counterparts that do not attend church.

CONCLUSION

This study demonstrated that church attendance is associated with less herpes-virus reactivation as indexed by lower levels of CMV IgG antibody titers, particularly among the bereaved. Future studies should focus on further understanding the pathways by which church attendance impacts CMV herpes-virus latency during stressful life events, such as bereavement.

Depressive symptoms are associated with salivary shedding of Epstein-Barr virus in female adolescents: The role of sex differences

BACKGROUND

Adolescent females have a higher prevalence of depression in comparison to their male peers - a disparity that has been increasing over the past decade. Depression is of concern as it is associated with chronic disease and to immune dysregulation, which may be one mechanism linking depression to future pathology. This study examined the extent to which sex moderated the association between depressive symptoms and immune dysregulation during adolescence using Epstein-Barr virus (EBV) reactivation, a biomarker of cellular immune response, as a model.

METHODS

A representative community sample of 259 female and 279 male adolescents aged 11-17 years who were EBV IgG positive were examined. Trained interviewers collected the data during two home visits, one week apart. Depressive symptoms were measured at the first visit using the 9 item short-form of the Center for Epidemiologic Studies-Depression scale. EBV biomarkers were collected via saliva at the second visit and included a qualitative measure of EBV viral capsid antigen immunoglobulin G to assess prior EBV infection and a quantitative measure of EBV DNA to assess the number of viral copies shed in the saliva.

RESULTS

In multivariable logistic regression analyses, increasing depressive symptoms were significantly associated with salivary shedding of EBV DNA for adolescent females only (logit=0.66, se=0.30, p<0.05), and the interaction between sex and depressive symptoms on salivary shedding of EBV DNA was statistically significant (logit=-1.19, se=0.42, p<0.01). Sensitivity analyses were conducted in which sex was examined as a moderator in the relationship between depressive symptoms and salivary EBV DNA quantitative copies via Tobit regression; results were consistent with the presented findings.

CONCLUSIONS

Depressive symptoms are associated with EBV reactivation among EBV positive female adolescents, but not males. Future research is needed to examine EBV reactivation in female adolescents as a mechanism linking depression to future chronic disease and the role of sex hormones in explaining sex differences in the relationship between depressive symptoms and EBV reactivation.

Increasing the accuracy and scalability of the Immunofluorescence Assay for Epstein Barr Virus by inferring continuous titers from a single sample dilution

High Epstein Barr Virus (EBV) titers detected by the indirect Immunofluorescence Assay (IFA) are a reliable predictor of Nasopharyngeal Carcinoma (NPC). Despite being the gold standard for serological detection of NPC, the IFA is limited by scaling bottlenecks. Specifically, 5 serial dilutions of each patient sample must be prepared and visually matched by an evaluator to one of 5 discrete titers. Here, we describe a simple method for inferring continuous EBV titers from IFA images acquired from NPC-positive patient sera using only a single sample dilution. In the first part of our study, 2 blinded evaluators used a set of reference titer standards to perform independent re-evaluations of historical samples with known titers. Besides exhibiting high inter-evaluator agreement, both evaluators were also in high concordance with historical titers, thus validating the accuracy of the reference titer standards. In the second part of the study, the reference titer standards were IFA-processed and assigned an 'EBV Score' using image analysis. A log-linear relationship between titers and EBV Score was observed. This relationship was preserved even when images were acquired and analyzed 3days post-IFA. We conclude that image analysis of IFA-processed samples can be used to infer a continuous EBV titer with just a single dilution of NPC-positive patient sera. This work opens new possibilities for improving the accuracy and scalability of IFA in the context of clinical screening.