Altered antibody profiles against common infectious agents in chronic disease

Cytomegalovirus IgG is Associated With Physical Function But Not Muscle Density in People With HIV

BACKGROUND

Cytomegalovirus (CMV) seropositivity is associated with poor outcomes, including physical function impairment, in people without HIV. We examined associations between CMV IgG titer and physical function in virologically suppressed people with HIV (PWH).

METHODS

REPRIEVE is a double-blind randomized trial evaluating pitavastatin for primary prevention of atherosclerotic cardiovascular disease in PWH. This analysis focused on participants enrolled in a substudy with additional biomarker testing, imaging [coronary CT angiography], and physical function measures at entry. CMV IgG was measured using quantitative enzyme immunoassay, physical function by Short Physical Performance Battery, and muscle density and area by CT. Associations between CMV IgG (risk factor) and outcomes were evaluated using the partial Spearman correlation and linear and log-binomial regression.

RESULTS

Among 717 participants, 82% male, the median CMV IgG was 2716 (Q1, Q3: 807, 6672) IU/mL, all above the limit of quantification. Among 631 participants with imaging, there was no association between CMV IgG and CT-based muscle density or area, controlling for age (r = -0.03 and r = -0.01, respectively; P ≥ 0.38). Among 161 participants with physical function data, higher CMV IgG was associated with poorer overall modified Short Physical Performance Battery score ( P = 0.02), adjusted for age, nadir CD4, and high-sensitivity C-reactive protein.

CONCLUSIONS

Higher CMV IgG titer was associated with poorer physical function, not explained by previous immune compromise, inflammation, or muscle density or area. Further mechanistic studies are needed to understand this association and whether CMV-specific therapy can affect physical function in PWH.

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.

Inherited Chromosomally Integrated Human Herpesvirus 6 Demonstrates Tissue-Specific RNA Expression In Vivo That Correlates with an Increased Antibody Immune Response

HHV-6A and -6B are human herpesviruses that have the unique property of being able to integrate into the telomeric regions of human chromosomes. Approximately 1% of the world’s population carries integrated HHV-6A/B genome in every cell of their body. Whether viral genes are transcriptionally active in these individuals is unclear. By taking advantage of a unique tissue-specific gene expression data set, we showed that the majority of tissues from iciHHV-6 individuals do not show HHV-6 gene expression. Brain and testes showed the highest tissue-specific expression of HHV-6 genes in two separate data sets. Two HHV-6 genes, U90 (immediate early 1 protein) and U100 (glycoproteins Q1 and Q2), were found to be selectively and consistently expressed across several human tissues. Expression of U90 translates into an increase in antigen-specific antibody response in iciHHV-6A/B⁺ subjects relative to controls. Future studies will be needed to determine the mechanism of gene expression, the effects of these genes on human gene transcription networks, and the pathophysiological impact of having increased viral protein expression in tissue in conjunction with increased antigen-specific antibody production.

Human herpesviruses 6A and 6B (HHV-6A and HHV-6B) are human viruses capable of chromosomal integration. Approximately 1% of the human population carries one copy of HHV-6A/B integrated into every cell in their body, referred to as inherited chromosomally integrated human herpesvirus 6A/B (iciHHV-6A/B). Whether iciHHV-6A/B is transcriptionally active in vivo and how it shapes the immunological response are still unclear. In this study, we screened DNA sequencing (DNA-seq) and transcriptome sequencing (RNA-seq) data for 650 individuals available through the Genotype-Tissue Expression (GTEx) project and identified 2 iciHHV-6A- and 4 iciHHV-6B-positive candidates. When corresponding tissue-specific gene expression signatures were analyzed, low levels HHV-6A/B gene expression was found across multiple tissues, with the highest levels of gene expression in the brain (specifically for HHV-6A), testis, esophagus, and adrenal gland. U90 and U100 were the most highly expressed HHV-6 genes in both iciHHV-6A- and iciHHV-6B-positive individuals. To assess whether tissue-specific gene expression from iciHHV-6A/B influences the immune response, a cohort of 15,498 subjects was screened and 85 iciHHV-6A/B⁺ subjects were identified. Plasma samples from iciHHV-6A/B⁺ and age- and sex-matched controls were analyzed for antibodies to control antigens (cytomegalovirus [CMV], Epstein-Barr virus [EBV], and influenza virus [FLU]) or HHV-6A/B antigens. Our results indicate that iciHHV-6A/B⁺ subjects have significantly more antibodies against the U90 gene product (IE1) than do non-iciHHV-6-positive individuals. Antibody responses against EBV and FLU antigens or HHV-6A/B gene products either not expressed or expressed at low levels, such as U47, U57, and U72, were identical between controls and iciHHV-6A/B⁺ subjects. CMV-seropositive individuals with iciHHV-6A/B⁺ have more antibodies against CMV pp150 than do CMV-seropositive controls. These results argue that spontaneous gene expression from integrated HHV-6A/B leads to an increase in antigenic burden that translates into a more robust HHV-6A/B-specific antibody response.

IMPORTANCE HHV-6A and -6B are human herpesviruses that have the unique property of being able to integrate into the telomeric regions of human chromosomes. Approximately 1% of the world’s population carries integrated HHV-6A/B genome in every cell of their body. Whether viral genes are transcriptionally active in these individuals is unclear. By taking advantage of a unique tissue-specific gene expression data set, we showed that the majority of tissues from iciHHV-6 individuals do not show HHV-6 gene expression. Brain and testes showed the highest tissue-specific expression of HHV-6 genes in two separate data sets. Two HHV-6 genes, U90 (immediate early 1 protein) and U100 (glycoproteins Q1 and Q2), were found to be selectively and consistently expressed across several human tissues. Expression of U90 translates into an increase in antigen-specific antibody response in iciHHV-6A/B⁺ subjects relative to controls. Future studies will be needed to determine the mechanism of gene expression, the effects of these genes on human gene transcription networks, and the pathophysiological impact of having increased viral protein expression in tissue in conjunction with increased antigen-specific antibody production.

New Parvovirus Associated with Serum Hepatitis in Horses after Inoculation of Common Biological Product

Equine serum hepatitis (i.e., Theiler's disease) is a serious and often life-threatening disease of unknown etiology that affects horses. A horse in Nebraska, USA, with serum hepatitis died 65 days after treatment with equine-origin tetanus antitoxin. We identified an unknown parvovirus in serum and liver of the dead horse and in the administered antitoxin. The equine parvovirus-hepatitis (EqPV-H) shares <50% protein identity with its phylogenetic relatives of the genus Copiparvovirus. Next, we experimentally infected 2 horses using a tetanus antitoxin contaminated with EqPV-H. Viremia developed, the horses seroconverted, and acute hepatitis developed that was confirmed by clinical, biochemical, and histopathologic testing. We also determined that EqPV-H is an endemic infection because, in a cohort of 100 clinically normal adult horses, 13 were viremic and 15 were seropositive. We identified a new virus associated with equine serum hepatitis and confirmed its pathogenicity and transmissibility through contaminated biological products.

Emerging technologies for the detection of viral infections

Viruses represent one of the major environmental agents that cause human illness and disease. However, the ability to diagnose viral infections is limited by detection capability and scope. Here we describe several emerging technologies that provide rapid and/or high-quality viral diagnostic information. Two technologies, novel CRISPR-based diagnostics and a portable DNA sequencing instrument, are uniquely suited to increase the number of viral agents analyzed, even in point of care settings. We also discuss a phage-based method for generating comprehensive viral profiles of previous exposure/infection and a fluid-phase immunoassay that yields highly quantitative viral antibody analyses. Future applications of these approaches will accelerate on-site clinical diagnosis of viral infections and provide insights into the role viruses play in complex diseases.

Physical function impairment of older, HIV-infected adults is associated with cytomegalovirus immunoglobulin response

Cytomegalovirus (CMV) is associated with poor outcomes, including physical function impairment, in older HIV-uninfected adults. Whether CMV is associated with physical functional impairment in HIV-infected adults is unknown. The primary objective of this study was to determine the relationship between CMV-specific humoral and cell-mediated immune responses with functional impairment in well-controlled HIV infection. In a case-control study, low-function cases were matched by age, gender, and time from HIV diagnosis to high-function controls. Quantitative CMV IgG and %CMV-specific CD8(+) and CD4(+) T cells (interferon-γ expression following CMV pp65 stimulation) were used to estimate physical function. Among 30 low-function cases and 48 high-function matched controls, CMV IgG ranged from <10 to 8,830 EU/ml, including four controls with results <10 EU/ml. Each log10 increase in CMV IgG was associated with 5-fold greater odds of low function (p=0.01); these findings were robust to adjustment for concomitant CD4(+) count, tobacco use, and age; to exclusion of subjects with CMV IgG <10 EU/ml; and to adjustment for hepatitis C viremia. %CMV-specific CD4(+) or CD8(+) T cells were not associated with low function. In bivariable models, the relationship between CMV IgG and physical function was attenuated and was no longer significant when including IL-6, CD4/CD8 ratio, or the Veterans Aging Cohort Study Index score. High levels of CMV-specific IgG were associated with impaired physical function. Attenuation of the strength of this association in bivariable models suggests an indirect relationship mediated by systemic inflammation and immune suppression.

Luciferase immunoprecipitation systems for measuring antibodies in autoimmune and infectious diseases

Antibody profiles have the potential to revolutionize personalized medicine by providing important information related to autoimmunity against self-proteins and exposure to infectious agents. One immunoassay technology, luciferase immunoprecipitation systems (LIPS), harnesses light-emitting recombinant proteins to generate robust, high-quality antibody data often spanning a large dynamic range of detection. Here, we describe the general format of LIPS and discuss studies using the technology to measure autoantibodies in several human autoimmune diseases including type 1 diabetes, Sjögren's syndrome, systemic lupus erythematosus, and immunodeficiencies secondary to anticytokine autoantibodies. We also describe the usefulness of evaluating antibodies against single or multiple antigens from infectious agents for diagnosis, pathogen discovery, and for obtaining individual exposure profiles. These diverse findings support the notion that the LIPS is a useful technology for generating antibody profiles for personalized diagnosis and monitoring of human health.