Detection of antibodies to varicella-zoster virus in recipients of the varicella vaccine by using a luciferase immunoprecipitation system assay.

Detection of Antibodies to Varicella-Zoster Virus in Recipients of the Varicella Vaccine by Using a Luciferase Immunoprecipitation System Assay Jeffrey I. Cohen,a Mir A. Ali,a Ahmad Bayat,b Sharon P. Steinberg,c Hosun Park,d Anne A. Gershon,c Peter D. Burbeloe Medical Virology Section, Laboratory of Infectious Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, USAa; Department of Perioperative Medicine, Clinical Center, National Institutes of Health, Bethesda, Maryland, USAb; Division of Pediatric Infectious Disease, Department of Pediatrics, Columbia University College of Physicians and Surgeons, New York, New York, USAc; Department of Microbiology, College of Medicine, Yeungnam University, Daegu, South Koread; Dental Clinical Research Core, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, Maryland, USAe A high-throughput test to detect varicella-zoster virus (VZV) antibodies in varicella vaccine recipients is not currently available. One of the most sensitive tests for detecting VZV antibodies after vaccination is the fluorescent antibody to membrane antigen (FAMA) test. Unfortunately, this test is labor-intensive, somewhat subjective to read, and not commercially available. Therefore, we developed a highly quantitative and high-throughput luciferase immunoprecipitation system (LIPS) assay to detect antibody to VZV glycoprotein E (gE). Tests of children who received the varicella vaccine showed that the gE LIPS assay had 90% sensitivity and 70% specificity, a viral capsid antigen enzyme-linked immunosorbent assay (ELISA) had 67% and 87% specificity, and a glycoprotein ELISA (not commercially available in the United States) had 94% sensitivity and 74% specificity compared with the FAMA test. The rates of antibody detection by the gE LIPS and glycoprotein ELISA were not statistically different. Therefore, the gE LIPS assay may be useful for detecting VZV antibodies in varicella vaccine recipients. (This study has been registered at ClinicalTrials.gov under registration no. NCT00921999.) V aricella-zoster virus (VZV) causes both chickenpox and zoster. A live attenuated varicella vaccine derived from the Oka strain of the virus was developed by Takahashi and colleagues in the 1970s and was licensed for routine use in the United States in 1995. One of the most sensitive tests for detecting VZV antibodies after vaccination is the fluorescent antibody to membrane antigen (FAMA) test. For this test, serial dilutions of human serum are incubated with live VZV-infected human fibroblasts, incubated with fluorescein-tagged anti-human immunoglobulin, and examined by fluorescence microscopy (1). The test detects antibodies to surface glycoproteins on live VZV-infected cells. While the FAMA test is highly predictive of protection from varicella infection after vaccination (2), the test is labor-intensive and somewhat subjective to read. Therefore, the FAMA assay is not applicable for largescale or commercial testing, nor is it readily available. Most laboratories use commercial enzyme-linked immunosorbent assays (ELISAs) to determine VZV seropositivity. A comparison of the commercially available ELISA with the FAMA test in recipients of the varicella vaccine indicates that the ELISA has a sensitivity of 74% and a specificity of 89% (3) (assuming that the FAMA has 100% sensitivity and 100% specificity). Thus, the ELISA is not considered sufficiently sensitive for reliably detecting antibodies after varicella immunization. Several studies have reported failures to seroconvert after immunization even after 2 doses, based on ELISA (4), and these are thought to represent a failure to detect antibody responses rather than a failure of the vaccine. Modified FAMA tests have been developed, including ones that use fixed cells (5) and a flow cytometry-based FAMA assay using virus-infected cells (6). The fixed-cells test is subjective to read, and the flow cytometry-based test uses live virus-infected cells; however, neither test is commercially available. Other tests have been developed in an attempt to replace the FAMA test. A 1288 cvi.asm.org Clinical and Vaccine Immunology glycoprotein (gp) ELISA containing purified VZV-infected cell glycoproteins (including gE, gB, and gH) was developed by Merck to measure antibodies after vaccination (7); however, this test is not commercially available. In a recent study in Europe (8), a different commercially available gpELISA and a whole-cell ELISA had 92% and 96% sensitivity, respectively, compared to that of the FAMA test for detecting VZV antibodies in vaccine recipients. A time-resolved fluorescence immunoassay (TRFIA) showed 83% sensitivity and 88% specificity in vaccine recipients compared with those of the FAMA test (9). A comparison of a latex agglutination test, which is no longer marketed, with the FAMA test in recipients of the varicella vaccine indicated that the latex agglutination assay had a sensitivity of 82% and a specificity of 94% (3). Serological testing after vaccination is not recommended, because commercially available tests are not sensitive enough to detect antibodies and may lack specificity (10, 11). Concerns persist about vaccine responses in women who may become pregnant and in health care workers, especially those who care for patients with varicella and zoster infection. All of these individuals have an increased risk for developing severe varicella infection. Therefore, a sensitive and specific reliable test for measuring VZV antibodies on a large-scale basis would be clinically useful. We developed a new assay based on a highly quantitative immunoprecipitation Received 24 April 2014 Returned for modification 10 June 2014 Accepted 29 June 2014 Published ahead of print 2 July 2014 Editor: S. A. Plotkin Address correspondence to Jeffrey I. Cohen, . Copyright © 2014, American Society for Microbiology. All Rights Reserved. doi:10.1128/CVI.00250-14 p. 1288 –1291 September 2014 Volume 21 Number 9 Antibodies to VZV in Vaccine Recipients assay format (12) and compared it to the standard ELISA, FAMA test, and gpELISA for VZV. MATERIALS AND METHODS Subjects. Serum samples were obtained from three sources, and all assays were performed in a blinded fashion. Archived serum from South Korea and New York were anonymized, and the use of samples was deemed exempt by the Office of Human Subjects Research at the National Institutes of Health (NIH). The subjects at NIH gave informed consent and the study (ClinicalTrials.gov under registration no. NCT00921999) was approved by the Institutional Review Board of the National Institute of Allergy and Infectious Diseases. The initial cohort of 40 samples from New York included 11 serum samples from healthy patients (mostly adults) obtained prior to developing varicella infection (all with negative FAMA titers), 11 serum samples from patients after proven varicella infe (...truncated)