Immunity to the Varicella-Zoster Virus

Varicella zoster virus (VZV) is a highly contagious agent of chickenpox and shingles. Chickenpox can be fatal for immunocompromised patients, babies, HIV patients and other adults with weakened immunity. Serological evaluation of immunity to VZV will help determine which individuals are susceptible and assess vaccine efficacy.

A collection of 110 monoclonal antibodies (mAbs) was obtained by immunizing mice with membrane proteins or acellular viruses. The mAbs were well characterized and a competitive sandwich ELISA (capture mAb: 8H6; label mAb: 1B11) was established to determine neutralizing antibodies in human serum with reference to the FAMA assay. A total of 920 human sera were evaluated.

The competitive sandwich ELISA test showed 95.6% sensitivity, 99.77% specificity and 97.61% coincidence compared to the fluorescent-antibody-to-membrane-antigen (FAMA) test. Capture mAb 8H6 has been characterized as a specific mAb for VZV ORF9, a membrane-associated tegument protein that interacts with glycoprotein E (gE), glycoprotein B (gB), and glycoprotein C (gC).

The 1B11 marker mAb was characterized as a complement-dependent neutralizing mAb specific for the immunodominant epitope located on gE, not on other VZV glycoproteins. The established competitive sandwich ELISA could be used as a rapid, high-throughput method to assess immunity to VZV.

Varicella zoster virus (VZV) is a highly contagious agent belonging to the Alphaherpesvirinae subfamily. Primary VZV infection causes varicella, while reactivation of latent sensory ganglia virus results in shingles (HZ)1. Postherpetic neuralgia (PHN) is a severe sequelae of shingles and the most common, especially in the elderly2. VZV infections are more serious in immunocompromised patients and can be accompanied by serious complications, such as encephalomyelitis3, gangrenous varicella4, myelitis5.

Effective vaccines have been developed to prevent VZV infection6,7, however, they are limited by the scope of vaccination and in some cases vaccine efficacy8 and VZV remains an important pathogen. In particular, laboratory determination of VZV immunity status has been recommended for immunocompromised patients, pregnant women, and healthcare workers after exposure to VZV9.

VZV-specific antibodies in serum could be used as a reliable indicator for serological confirmation of VZV-specific immunity10. A highly sensitive and specific serological test is important to achieve herd immunity against VZV. Several methods have been developed to measure VZV-specific immunoglobulin G (IgG) antibodies, including the fluorescent antibody-to-membrane-antigen (FAMA) test11,12, an antigen-based enzyme-linked immunosorbent assay (ELISA) total VZV or purified glycoproteins (gps)13,14,15 and many other methods10,16,17,18,19,20,21.

Glycoprotein-based ELISA (gpELISA) has been used to detect seroconversion in vaccinated populations13,15,18. The FAMA test is considered the "gold standard" indication for immunity to varicella8,11. FAMA titer is strongly correlated with the level of neutralizing antibodies and susceptibility to varicella22,23,24. In addition, the FAMA test result is officially approved and it is recommended that new tests use the FAMA test as a reference.