Comparison of five assays for antibody to varicella-zoster virus and the fluorescent-antibody-to-membrane-antigen test

Current Methods for the Detection of Antibodies of Varicella-Zoster Virus: A Review

Infection with the varicella-zoster virus (VZV) causes chickenpox and shingles, which lead to significant morbidity and mortality globally. The detection of serum VZV-specific antibodies is important for the clinical diagnosis and sero-epidemiological research of VZV infection, and for assessing the effect of VZV vaccine immunization. Over recent decades, a variety of methods for VZV antibody detection have been developed. This review summarizes and compares the current methods for detecting VZV antibodies, and discussed future directions for this field.

Epidemiology of Breakthrough Varicella after the Implementation of a Universal Varicella Vaccination Program in Taiwan, 2004-2014

National one-dose varicella vaccination at 12 months of age was implemented in Taiwan since 2004.Our study aimed to evaluate breakthrough varicella (BV) in post-vaccine era and its associated risk factors. We retrospectively identified children vaccinated against varicella between 12-23 months of age during 2004-2008. Their vaccination information was extracted from the national vaccination registry system and linked to the 2004-2014 National Health Insurance database. BV was defined as a diagnosis of varicella (ICD-9-CM codes 052 and 052.0-052.9) beyond 42 days post-vaccination. Multiple Cox regression model was used to identify risk factors for BV. Among 932,874 enrolled vaccinees, 26,446 (2.8%) had BV and 219 (0.024%) required hospitalization over the study period. Varicella incidence declined from 4.71 per 1000 person-year (PY) in 2004 to 0.81/1000 PY in 2014. BV incidence decreased from 3.90/1000 PY at first year to 1.94/1000 PY at 11th year after vaccination. Females had a lower risk for BV than males (hazard ratio [HR] 0.85, 95% CI, 0.83-0.87); Varivax^® recipients had a lower risk for BV than Varilrix^® recipients (HR 0.75, 95% CI, 0.72-0.78). Our study showed the incidence of varicella, BV and varicella-related hospitalizations in Taiwan were kept low in post-vaccine era.

Negative IgG Varicella Zoster Virus Antibody Status: Immune Responses Pre and Post Re-immunization

INTRODUCTION

Varicella zoster virus (VZV) causes chicken pox and herpes zoster and is a self-limiting disease in healthy children. Vaccination is recommended for children, adolescents, and adults. This study discusses a healthy pediatric patient with negative immunoglobulin (Ig) G VZV antibody (Ab) status after two doses of varicella vaccine and then subsequently re-immunized. Since measurement of serum IgG titers alone may not reflect vaccine protection, we further evaluated cell-mediated and humoral immune responses before and after re-immunization.

METHODS

Blood lymphocyte distributions (CD3+CD4+, CD3+CD8+, CD19+, CD4+CD60+, CD8+CD60+), total serum IgG and IgE levels, and VZV-IgG, IgM, and IgE Ab levels were measured in a healthy girl (14 year-old) pre- and post-VZV re-immunization (weeks 1-8) [flow microfluorimetry, nephelometry, ELISA, enzyme immunoassay (EIA)].

RESULTS

Pre-re-immunization numbers of T cells (CD3+CD4+, CD3+CD8+, CD4+CD60+, CD8+CD60+) and B cells (CD19+) were within normal ranges. After re-immunization, numbers of T cells remained relatively unchanged; however, numbers of CD19+ B cells increased (48%). Total serum IgG was low (757 mg/dl), and total serum IgE was normal (30 IU/ml). Pre-reimmunization, VZV IgG and IgM Ab levels were negative (< 0.90 and < 0.90 antibody index, respectively), and VZV IgE levels were undetectable. After re-immunization, VZV IgG Ab levels were positive (690.70 Ab index), VZV IgM Ab levels were negative (≤ 0.90), and VZV IgE levels remained undetectable.

CONCLUSION

Vaccination with the VZV vaccine may boost IgG but not IgE-specific viral responses and concurrently increase the numbers of CD19+ B cells.

Evaluation of immunity to varicella zoster virus with a novel double antigen sandwich enzyme-linked immunosorbent assay

Varicella is a highly contagious disease caused by primary infection of Varicella zoster virus (VZV). Varicella can be severe or even lethal in susceptible adults, immunocompromised patients and neonates. Determination of the status of immunity to VZV is recommended for these high-risk populations. Furthermore, measurement of population immunity to VZV can help in developing proper varicella vaccination programmes. VZV glycoprotein E (gE) is an antigen that has been demonstrated to be a highly accurate indicator of VZV-specific immunity. In this study, recombinant gE (rgE) was used to establish a double antigen sandwich enzyme-linked immunosorbent assay (ELISA). The established sandwich ELISA showed high specificity and sensitivity in the detection of human sera, and it could detect VZV-specific antibodies at a concentration of 11.25 m IU/mL with a detection linearity interval of 11.25 to 360 m IU/mL (R ² = 0.9985). The double gE antigen sandwich ELISA showed a sensitivity of 95.08 % and specificity of 100 % compared to the fluorescent-antibody-to-membrane-antigen (FAMA) test, and it showed a sensitivity of 100 % and a specificity of 94.74 % compared to a commercial neutralizing antibody detection kit. Thus, the established double antigen sandwich ELISA can be used as a sensitive and specific quantitative method to evaluate immunity to VZV.

Seroepidemiology of varicella-zoster virus in Korean adolescents and adults using fluorescent antibody to membrane antigen test

We conducted a cross-sectional seroepidemiological study in 2012–2013 to determine the seroprevalence of varicella-zoster virus (VZV) in adolescents and adults living in Korea, where varicella vaccination has been recommended universally at age 12–15 months since 2005. Residual serum samples were collected from 1196 healthy adults and adolescents aged ⩾10 years between November 2012 and March 2013. The fluorescent antibody to membrane antigen (FAMA) test and enzyme-linked immunosorbent assay (ELISA) were performed to determine the seroprevalence of VZV. The seroprevalences of VZV were compared between six age groups: 10–19, 20–29, 30–39, 40–49, 50–59, and ⩾60 years. The seroprevalence of VZV in the entire study cohort was 99·1% according to the FAMA test and 93·1% as determined by ELISA. The seroprevalences of the six age groups were as follows: 96·0%, 99·5%, 99·5%, 99·5%, 100%, and 100%, respectively, by the FAMA test, and 83·3%, 93·0%, 93·0%, 97·5%, 94·5%, and 97·5%, respectively, by ELISA. Seroprevalence increased significantly with age (P < 0·001); moreover, the seroprevalence in subjects aged 10–19 years was significantly lower than in other age groups (P < 0·001), as measured by both the FAMA test and ELISA. Thus, strategies to increase protective immunity against VZV in teenagers are necessary.

Seroprevalence rate after one dose of varicella vaccine in infants

SUMMARY BACKGROUND

Live, attenuated varicella vaccine has been used since 1988 in Korea. However, varicella is still prevalent among both vaccinated and unvaccinated individuals, despite a relatively high level of immunization rate up to 80%. A recent report has demonstrated approximately 20% of primary vaccine failure rate after one dose of varicella vaccine using the fluorescent antibody to membrane antigen (FAMA) assay.

METHODS

The seroprevalence rate was determined using the FAMA and ELISA assays in 67 Korean infants following one dose of varicella vaccine. Positive fluorescence at a serum dilution of 1:4 or greater was considered as seropositive.

RESULTS

The median age at vaccination was 12 months and the post-immunization sera were obtained on average 6.3 months (range 6 weeks-12 months) after vaccination. Among the 67 vaccinated infants, 56 (83.6%) were seropositive by FAMA assay while 30 (44.8%) were seropositive by ELISA. The geometric mean titers (GMTs) of the seropositive vaccinated infants (n = 56) were significantly lower than the GMTs of 9 individuals with a history of varicella (1:17.0 vs. 1:74.7, P = 0.001). Although there were no significant differences in seropositive rates according to intervals, there was a decreasing trend in the GMTs over time among the 56 seropositive recipients (r(2) = 0.154, P < 0.001).

CONCLUSIONS

These data can be useful for optimizing the immunization strategy against varicella and should be confirmed by a prospective study including a large number of immunized infants.

Comparison of fifteen commercial assays for detecting Varicella Zoster virus IgG with reference to a time resolved fluorescence immunoassay (TRFIA) and the performance of two commercial assays for screening sera from immunocompromised individuals

The performance of fifteen, commercially available, VZV IgG assays and an "in house" indirect immunofluorescence (IF) assay has been compared to a reference VZV IgG time resolved immunofluorescence assay (VZV TRFIA). A panel of 273 VZV TRFIA IgG positive serum samples and 136 VZV TRFIA IgG susceptible sera, collected from a number of UK hospitals was used. Irrespective of the interpretation of equivocal results the most sensitive assays were Dade Behring EIA (97.4%), "in house" IF (95.2%), Human EIA (92.3%) and Becton Dickinson latex agglutination (94.1%). The least sensitive assays were Virion EIA (69.6%), Diesse EIA (68.9%) and Diasys EIA (68.5%). The least sensitive (<70%) assays all had >99.0% specificity whereas the most sensitive assays had lower specificities; for example, Dade Behring EIA had a specificity of 69.9% when equivocals were treated as VZV IgG negative. For some assays e.g. Dade Behring EIA there were major discrepancies between our findings and those reported by the manufacturer which may reflect the constitution of the panel(s) of sera used for evaluation or the reference method adopted or the choice of cut-off criteria (particularly relevant to our findings for the Behring EIA). Care must be taken to choose an assay with high specificity in order to accurately assess the need for vaccination or immunoprophylaxis; however, high sensitivity is preferable to prevent inappropriate and expensive treatment.

Primary vaccine failure after 1 dose of varicella vaccine in healthy children

Universal immunization of young children with 1 dose of varicella vaccine was recommended in the United States in 1995, and it has significantly decreased the incidence of chickenpox. Outbreaks of varicella, however, are reported among vaccinated children. Although vaccine effectiveness has usually been 85%, rates as low as 44% have been observed. Whether this is from primary or secondary vaccine failure-or both-is unclear. We tested serum samples from 148 healthy children immunized against varicella in New York, Tennessee, and California to determine their seroconversion rates, before and after 1 dose of Merck/Oka varicella vaccine. The median age at vaccination was 12.5 months; postvaccination serum samples were obtained on average 4 months later. Serum was tested for antibodies against varicella-zoster virus (VZV) by use of the previously validated sensitive and specific fluorescent antibody to membrane antigen (FAMA) assay. Of 148 healthy child vaccinees, 113 (76%) seroconverted, and 24% had no detectable VZV FAMA antibodies. Our data contrast with reported seroconversion rates of 86%-96% by other VZV antibody tests and suggest that many cases of varicella in immunized children are due to primary vaccine failure. A second dose of varicella vaccine is expected to increase seroconversion rates and vaccine effectiveness.

European seroepidemiology network 2: Standardisation of assays for seroepidemiology of varicella zoster virus

BACKGROUND

The aim of the European Sero-Epidemiology Network (ESEN2) is to harmonise the serological surveillance of vaccine-preventable diseases in Europe.

OBJECTIVE

To allow comparison of antibody prevalence in different countries by standardising results into common units.

STUDY DESIGN

For varicella zoster virus (VZV), a reference laboratory established a panel of 148 samples, characterised by indirect enzyme-immunoassay (ELISA), indirect immunofluorescence, and complement fixation test. Fifty-seven samples were also studied by the fluorescence antibody to membrane antigen test. The geometric mean of the antibody activity (GMAA) obtained from four ELISA determinations was used to characterise each sample of the panel as positive (GMAA: >100 mIU/ml), equivocal (GMAA: 50-100 mIU/ml) or negative (GMAA: <50 mIU/ml) for antibody to VZV (anti-VZV). Thirteen laboratories, using five different ELISA tests, tested the panel.

RESULTS

Agreement with the reference laboratory was above 85% in all cases, and the R(2) values obtained from regression analysis of the quantitative results were always higher than 0.87. Finally, the regression equations could be used to convert national values into a common unitage.

CONCLUSION

This study confirmed that results for anti-VZV obtained by different ELISA methods can be converted into common units, enabling the comparison of the seroprevalence profiles obtained in the participant countries.

Performance of a time-resolved fluorescence immunoassay for measuring varicella-zoster virus immunoglobulin G levels in adults and comparison with commercial enzyme immunoassays and Merck glycoprotein enzyme immunoassay

Highly sensitive and specific, quantitative assays are needed to detect varicella-zoster virus (VZV) immunoglobulin G in human sera, particularly for determining immune status and response following vaccination. A time-resolved fluorescence immunoassay (TRFIA) has been developed, and its performance was compared to that of two commercial enzyme immunoassays (EIAs) and Merck glycoprotein EIA (gpEIA). The TRFIA had equivalent sensitivity (97.8%) and high specificity (93.5%) in relation to gpEIA. A commercial (Behring) EIA compared favorably with TRFIA in terms of sensitivity (98.4%) but had lower specificity (80.7%). Another commercial EIA (Diamedix) had high specificity (97.1%) but low sensitivity (76.4%) compared to TRFIA if equivocal test results were treated as negative for VZV antibody. A novel feature of the TRFIA was that the cutoff was generated using population mixture modeling and was expressed in mIU/ml, as the assay was calibrated using the British standard VZV antibody.

Varicella zoster virus antibody titers after intravenous zoster immune globulin in neonates, and the safety of this preparation

AIMS

1) To assess the safety of intravenous varicella zoster virus hyperimmune globulin G (IV-VZVIG) in neonates; 2) measure varicella zoster virus-specific IgG antibody (VZVIG) changes in newborn IV-VZVIG recipients.

METHODS

Eighteen neonatal intensive care unit (NICU) neonates with varicella exposure were given 1 ml/kg (43 International Units (IU)/kg) Varitect IV-VZVIG. Serum VZVIG titers were assayed in neonatal recipients 0, 1, 7, 14, 21, 28, and 35 d after IV-VZVIG. Also, serum samples for VZV-IgM antibody determinations were obtained at 4 wk post-infusion.

RESULTS

No varicella developed in the 18 infants. Infusion of 1 ml/kg (43 IU/kg) IV-VZVIG was generally safe. The IV-VZVIG dose resulted in seroconversion of a non-immune newborn. Five infants had low basal VZVIG titers, and two of them had a 0.6-log10 increase at 24 h post-infusion. Neonatal VZVIG titers (mean+/-SEM in log(10)) before IV-VZVIG and after by 1, 7, 14, 21, 28, and 35 d were 2.22+/-0.15, 2.17+/-0.17, 2.02+/-0.12, 0.87+/-0.2, 1.09+/-0.19, 2.33+/-0.07, and 2.16+/-0.1, respectively.

CONCLUSIONS

One ml/kg (43 IU/kg) IV-VZVIG was generally safe. Our neonatal mean VZV-immune status did not significantly increase after the 1 ml/kg (43 IU/kg) IV-VZVIG dose, although no varicella developed and it caused a VZV-specific seroconversion.

Effectiveness of live varicella vaccine

The disease burden of chickenpox to children has been described, and a lower force of neutralising antibody to varicella-zoster virus (VZV) than against measles, either after natural infection or after vaccination, has been reported. In the case of VZV, strong cell-mediated immunity may work efficiently to prevent the spread of the virus. The lower force of humoral antibody to VZV might be related to the occurrence of "breakthrough" varicella cases in a small portion of the vaccine recipients. Safety and high effectiveness of the varicella vaccine--approximately 85% effective for all diseases and 95-100% effective for moderate-to-severe diseases--have been reported. Vaccine-induced immunity persists for 10-20 years. However, concerns have been raised that universal immunisation in children may shift the susceptibility from children to adults, whose symptoms are usually moderate-to-severe. In addition, other concerns have been expressed that, due to lack of exposure to varicella in children, the elderly may develop zoster infections more frequently than before. A clear answer is difficult to give at present, although, for several reasons, such situations may be unlikely to occur.

Immunofluorescence test for sensitive detection of varicella-zoster virus-specific IgG: an alternative to fluorescent antibody to membrane antigen test

A highly sensitive indirect fluorescence antibody test (IFAT) has been developed on the basis of varicella-zoster virus (VZV)-infected human lung carcinoma (A549) cells and evaluated for the determination of immunity to VZV. Different serum panels with negative, low, moderate or high anti-VZV IgG levels detected by the fluorescent antibody to membrane antigen (FAMA) assay were investigated. As a result, the sensitivity and the specificity of IFAT were 100% compared to FAMA test. In anti-VZV IgG-positive sera, a significant correlation between the results of FAMA procedure and IFAT could be shown. However, there were considerably higher antibody titers by the IFAT than by FAMA. Whereas the FAMA test had a detection limit of 250 mIU/ml anti-VZV IgG, the limit of detection of IFAT was 50 mIU/ml. In conclusion, the IFAT using VZV-infected A549 cells as antigen allows a highly sensitive, specific, and rapid detection of anti-VZV IgG class antibodies. This simple technique can replace the labor-intensive FAMA procedure for laboratory determination of immunity to VZV.

Viral diseases of the oral mucosa

A wide variety of both DNA and RNA viruses affect the oral cavity. When considered in conjunction with cutaneous features, careful examination of the oral mucosa and oropharynx aids the clinician in making a diagnosis. Examination of the oral cavity should be incorporated as a regular component of the dermatologic examination because diagnostic clues are readily available to assist in the evaluation of infectious processes.

Safety and immunogenicity of live attenuated varicella vaccine in 9-month-old children

BACKGROUND

The present study was conducted to evaluate the safety and immunogenicity of live attenuated varicella vaccine (Oka-strain) in 9-month-old infants.

METHODS

One hundred and fourteen infants were vaccinated once with live attenuated varicella vaccine (Valrix; SmithKline Beecham Biologicals, Rixensart, Belgium) containing a mean virus titer of 10(4.0) plaque-forming units (p.f.u.) per dose. Signs and/or symptoms after vaccination were followed for 42 days. Home visits were made to detect solicited local reactions (0-3 days) and solicited general reactions (0-21 days), as well as unsolicited reactions. Specific varicella antibodies were determined by an indirect immunofluorescence method. The geometric mean titer and seroconversion rate were calculated.

RESULTS

Signs and/or symptoms were reported in 47.4% (54/114) of cases following vaccination. The only local symptom reported was pain on digital pressure at the injection site and this was reported in 28.1% (32/114) of infants. General symptoms were reported in 38.6% (44/114) of cases. The most frequently reported findings were fever (27.2%), which was mostly mild, restlessness (20.2%) and cough (11.4%). Only four unsolicited symptoms were reported and they were all unrelated to vaccination. No serious adverse event was reported. Of the 109 infants included in the immunogenicity analysis, 105 were seronegative and four were seropositive for antibodies against varicella before vaccination. The vaccine elicited seroconversion in 97.1% of initially seronegative cases. The post-vaccination geometric mean titer for these infants was 30.9 geometric mean titer (GMT).

CONCLUSIONS

The vaccine was found to be safe and immunogenic when given to infants as young as 9 months of age. This may be of clinical significance during outbreaks of varicella and especially for developing countries.

Seroprevalence of varicella antibodies among new house officers

STUDY OBJECTIVE

Varicella, an illness common to children, can occur in nonimmune adults, often causing serious morbidity and mortality. House officers without protective titers to varicella are at risk of contracting the disease and may spread it to the patients they serve. They are also subject to significant losses in work time and wages. Accordingly, in August 1996, the Centers for Disease Control and Prevention recommended vaccinating nonimmune health care providers with the varicella vaccine. We also sought to document the seroprevalence of varicella antibodies among new house officers and to determine the association of self-reported history of infection with varicella antibody levels.

METHODS

This study was conducted at a university-affiliated teaching hospital. Serology testing was performed on house officers beginning their residencies in July 1997. Subjects provided information regarding demographics, medical history, previous varicella exposure, and previous administration of varicella vaccine. Serum was tested using the FIAX test kit, (Biowhitaker, Walkersville, MD).

RESULTS

One hundred fifty-four house officers participated. The mean age was 30 (range, 24 to 50+/-SD 5.5 years). History of varicella infection was given by 119 (77%) of the 154 subjects, whereas 15 (10%) reported no history of infection, and 20 (13%) were uncertain. Ten (7%) of the participants had received varicella vaccine previously. Overall, 6 (4%) had nonprotective titers to varicella. Of the 119 house officers who reported a history of varicella, only 2 (1.7%) had nonprotective titers, and 4 (27%) who reported no history of varicella infection had nonprotective titers. Of the 10 house officers who had previously received varicella vaccine, 1 (10%) had nonprotective titers.

CONCLUSION

Although most house officers had protective titers, a reported history of varicella or the administration of varicella vaccine did not assure the presence of protective titers. House officers should be tested for varicella immunity regardless of a history of previous infection or the administration of varicella vaccine.

Assays for antibodies to varicella-zoster virus

Anti-varicella-zoster virus serum antibody assays and their use in vaccine development are described. Of particular interest are FAMA and neutralization assays and the gpELISA. These and other assays are compared and summarized in terms of characteristics including biologic relevance, sensitivity, specificity, and suitability for different laboratory and clinical applications.

Comparison of two methods for detecting varicella-zoster virus antibody with varicella-zoster virus cell-mediated immunity

We evaluated an enzyme-linked immunoassay (EIA; BioWhittaker) and a latex agglutination (LA; Becton Dickinson) for varicella-zoster virus (VZV) antibody determination, using cell-mediated immunity (CMI) as a "gold standard." VZV EIA had a sensitivity, specificity, positive predictive value, and negative predictive value of 87, 91, 87, and 91%, respectively, compared with CMI. Correlation was excellent except when the varicella index was 0.9 to 1.2. We defined sera with varicella indices of 0.9 to 1.2 as indeterminate. LA had a sensitivity, specificity, positive predictive value, and negative predictive value of 96, 91, 97, and 90%, respectively, compared with EIA. LA reactivity only at a 1:2 dilution did not correlate with CMI, but sera reactive at dilutions of > or = 1:8 indirectly did. We defined indeterminate sera as those reactive at 1:2 and nonreactive at 1:8. EIA and LA were equivalent for determining VZV immune status, and both methods required modified criteria of interpretation to increase their specificity.

The risk of measles, mumps, and varicella among young adults: a serosurvey of US Navy and Marine Corps recruits

OBJECTIVES

To assess the risk of epidemic transmission and to guide immunization policy, the seroprevalence of antibody to measles, mumps, and varicella was determined in a group of young adults.

METHODS

A cross-sectional study of 1533 US Navy and Marine Corps recruits was conducted in June 1989. Antibody status was determined with commercially available enzyme-linked immunosorbent assays.

RESULTS

Direct sex and race adjustment to the 15- to 29-year-old US population resulted in seronegativity rates of 17.8% for measles, 12.3% for mumps, and 6.7% for varicella. Measles and mumps seronegativity rates were higher among Whites whereas varicella seronegativity was higher among non-Whites. Recruits enlisting from outside the 50 US states, especially those from island territories, were more likely to lack varicella antibody. The sensitivity of a positive history of vaccination or disease in predicting antibody status was less than 90% for all diseases.

CONCLUSIONS

These results suggest a continued potential for epidemics, especially of measles, and the need for mandatory immunization policies. Immigrants to the United States, especially those from island territories, may be a high-risk group that could benefit from varicella vaccination.