Schizophrenia Is Associated With an Aberrant Immune Response to Epstein–Barr Virus

Faith Dickerson; Lorraine Jones-Brando; Glen Ford; Giulio Genovese; Cassie Stallings; Andrea Origoni; Colm O'Dushlaine; Emily Katsafanas; Kevin Sweeney; Sunil Khushalani; Robert Yolken

Disclosures

Schizophr Bull. 2019;45(5):1112-1119. 

In This Article

Methods

Study Population

The study population consisted of 743 individuals: 432 with a schizophrenia diagnosis and 311 without a history of psychiatric disorder. The details of the recruitment and evaluation of individuals in these populations have been previously described.[24] Individuals with schizophrenia met the following criteria: age between 18 and 65 inclusive, diagnosis of schizophrenia or schizoaffective disorder meeting criteria in the Diagnostic and Statistical Manual of Mental Disorder Fourth Edition (DSM-IV); currently receiving antipsychotic medications. Individuals in the nonpsychiatric control sample met the criteria: age between 18 and 60 inclusive, absence of a current or past psychiatric disorder as confirmed by screening with the Structured Clinical Interview for DSM-IV Axis I Disorders – Non-patient Edition (SCID-I/NP). Participants were assessed for the deficit syndrome, a putative schizophrenia subtype comprised of individuals with schizophrenia who have primary and enduring negative symptoms such as restricted affect and diminished social drive.[25] Additional details of the methods for recruitment and evaluation are presented in the supplementary materials and methods.

The studies were approved by the Institutional Review Boards of the Sheppard Pratt Health System and the Johns Hopkins Medical Institutions following established guidelines. All participants provided written informed consent after the study procedures were explained.

Antibody Measurements

Immunoglobulin G (IgG) antibodies to EBV antigens derived from intact virions were measured by means of solid phase enzyme immunoassay. Details of the procedure are provided in the supplementary materials and methods. IgG antibodies to EBV-VCA and EBV nuclear antigen-1 (EBNA-1) were measured by solid phase immunoassay employing commercially available assay kits (IBL America).[26] IgG antibodies to other human herpesviruses were measured by similar procedures.[26,27] Complete baseline sample sets consisting of N = 743 individual blood samples were available for all immunoassay tests.

Quantitative western blot assays were performed using methods presented in the supplementary materials and depicted in supplementary figure 5. Samples were available for western blot from 257 individuals, 150 of whom were individuals with schizophrenia and 107 controls. The individuals from whom samples were available for western blot did not differ significantly from the overall study population in any demographic or clinical variable.

Supplemental Figure 5.

Using the "normalized intensity" option of the software displays the intensity curve of the entire test strip (shown above the test strip) in which any background interferences have been removed. The positions of the subset of 12 viral proteins specified by the software are shown above the curve. The software measures the intensity for each band and then determines the corresponding arbitrary intensity units as shown in the table of results below the strip. The intensities are then compared to those of the kit calibrator/control strip and a determination for each band as + Positive, (+) Borderline, or ○ Negative is made by the software. Anl: Positioning mark used by the software for proper alignment of each strip; Co: Control band for ensuring that the procedure was performed correctly, i.e., human IgX was applied followed by the alkaline phosphatase-labeled anti-human IgX and then the enzyme substrate; M, G, A: conjugate control that displays which specific human immunoglobulin, IgM, IgG, or IgA, has been tested on the strip. See Supplementary Methods for protocol details.

Genetic Analyses

DNA was extracted from whole blood and analyzed for genetic polymorphisms using the Illumina array. Polygenic risk score was calculated using a P-value cutoff of P < .05 for inclusion of individual polymorphisms used to calculate the polygenic risk score. Details of the methods used are provided in the supplementary material.

Statistical Analyses

The results of the assays were compared between the individuals with schizophrenia and controls employing parametric and nonparametric regression models.28 Details of the statistical methods are presented in the supplementary material. In light of the performance of 3 sets of immunoassay measurements (EBV virions, EBV VCA, EBNA-1), a critical value of P < .05/3 = .016 was employed to indicate statistical significance for assays using these measures. A value of .016 ≤ P ≤ .05 was considered to represent a trend.

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