Review on Discriminatory Tests of Immune Reaction due to Infection and Vaccination (DIVA Test)

Review Article

Austin J Vet Sci & Anim Husb. 2023; 10(3): 1120.

Review on Discriminatory Tests of Immune Reaction due to Infection and Vaccination (DIVA Test)

Tsion B¹* and Fanose T²

1Sebeta, Oromia, Ethiopia Animal Health Institute, Department of Veterinary Microbiology, Ethiopia

2Bishofitu, Oromia Addis Ababa University College of Veterinary Medicine and Agriculture, Ethiopia

*Corresponding author: Tsion B Sebeta, Oromia, Ethiopia Animal Health Institute, Department of Veterinary Microbiology, Ethiopia

Received: January 21, 2023; Accepted: March 07, 2023; Published: March 14, 2023

Abstract

In concern for animal diseases, the goal of vaccination is to prevent or reduce clinical diseases associated with the infectious agent, but it can also be used as a means of managing or eradicating a disease from a particular region. Therefore it is essential to differentiate immune responses due to vaccination compared to natural infection. It was to satisfy this requirement that the term Differentiation of Infected from Vaccinated Animals (DIVA) was coined in 1999 by Jan T van Oirschot. DIVA principle is based on a DIVA vaccine producing an antibody response that is different from the antibody response produced by the wild-type virus. The DIVA approach has been applied and proposed successfully to various diseases. Although considerable progress has been made to evaluate which different DIVA strategies are most likely to be applicable in the field, considerably more work needs to be done. If properly applied, DIVA vaccination strategies promise to provide new tools for the control and eradication of diseases.

Keywords: Control; Diseases; DIVA vaccines; Eradication

Abbreviations: DIVA: Differentiation of Infected from Vaccinated Animals

Introduction

Vaccination has effects at the individual and population, levels. Efficacious vaccines reduce or prevent clinical signs without necessarily preventing virus replication. They may also increase the dose of virus needed to establish an infection and/or reduce the level and duration of virus shedding following infection. Vaccine effectiveness within a population is a function of its ability to reduce virus transmission. Transmission is best described by the reproductive ratio, R, which is defined as the average number of new infections caused by one infectious individual. By helping to reduce the R-value below 1, vaccination can be an effective adjunct in abbreviating an outbreak. Nevertheless, vaccination can also complicate serological surveillance activities that follow eradication, if the antibody response induced by vaccination is indistinguishable from that which follows infection. This disadvantage can be overcome by the use of DIVA vaccines and their companion diagnostic tests [1,2].

The term DIVA (differentiating infected from vaccinated individuals) was coined in 1999 van Oirschot of the Central Veterinary Institute, in the Netherlands [3]. It is now generally used as an acronym for differentiating infected from vaccinated animals. The term was originally applied to the use of marker vaccines, which are based on deletion mutants of wild-type microbes, in conjunction with a differentiating diagnostic test. The DIVA strategy has been extended to include subunit and killed whole-virus vaccines. This system makes possible the mass vaccination of a susceptible animal population without compromising the serological identification of convalescent individuals. The DIVA approach has been applied successfully to pseudo rabies and avian influenza eradication, and has been proposed for use in foot-and-mouth disease and classical swine fever eradication campaigns [4].

This document provides a short review on the design and use of DIVA tests to differentiate between vaccinated and infected animals and also its impact on disease control and eradication.

Principle of Diva Test

The general DIVA principle is that antibody response produced by vaccination can be differentiated from the antibody response elicited by natural infection (e.g. a modified wild type virus with a gene deletion resulting in the absence of a particular diagnostic antigen). It can be live or killed vaccines. The DIVA immune response can be detected by companion diagnostic tests such as enzyme linked immunosorbent assay. Companion serology based tests rely on seroconversion, and upon exposure to wild type virus the antibody response to DIVA vaccines will be masked by that of the wild type virus [5]. More recently, the use of genetic DIVA has been introduced, which is based on identifying genetic differences between live vaccines and the field viruses.

The ability to identify and selectively delete genes from a pathogen has allowed the development of “marker vaccines” that, combined with suitable diagnostic assays, allow Differentiating Infected from Vaccinated Animals (DIVA) by differentiation of antibody responses induced by the vaccine (no antibodies generated to deleted genes) from those induced during infection with the wild-type virus. Such DIVA vaccines and their companion diagnostic tests are now available or in development for several diseases including Infectious Bovine Rhinotracheitis (IBR), pseudorabies, Classical Swine Fever (CSF), and FMD.

A marker vaccine can be either positive or negative in that it can include antigens not found in the wild-type virus, which would be a positive-marker vaccine, or it can contain fewer antigens than the wild-type virus and would be a negative-marker vaccine. In either case, a companion diagnostic test needs to be available to allow the differentiation of the vaccinated animal to the naturally infected animal [6].

The main advantage of DIVA vaccines and their companions test is the possibility to distinguish between infected and vaccinated animals. Therefore, special restrictions, which are necessary for infected animals, can be loosened for vaccinated animals [8].

Diva Designing and Development Strategies

The DIVA strategy has been extended to include subunit and killed whole-virus vaccines. This system makes possible the mass vaccination of a susceptible animal population without compromising the serological identification of convalescent individuals. The DIVA approach has been applied successfully to pseudorabies and avian influenza eradication, and has been proposed for use in foot-and-mouth disease and classical swine fever eradication campaigns [9].

Suitable and simple tests for differentiating vaccinated animals from infected are required for DIVA designing. The simple test has to be defined to differentiate vaccine strain from field strain. Although mucosal route is the best and most warranted, one study is required to prove that which of the route gives best protection against natural way of infection. Suitable dosages defined in terms of colony forming units (cfu) per dose have to be determined. Live vaccines require a bit of nutrient to support the life and side by side there is need to keep the cfu at constant level therefore live vaccines need a suitable excipient when the vaccine is not a freeze dried one and when it is freeze dried it need a suitable freeze drying and re- suspension medium to be chosen after experimentation [7].

There are a number of different DIVA systems currently available or in the process of development and validation. One type is Heterologous Nuraminidase type DIVA. It is a DIVA strategy based on the use of an inactivated oil-emulsion vaccine containing the same Hemaglutinin subtype as the challenge virus, but a different NA [10].

Four different serologic tests have been described for the hNA DIVA strategy including the indirect immunofluorescent antibody test (iIFAT), a standard Neuraminidase Inhibition (NI) test, a modified NI test, and the ELISA test. For both the standard and modified NI tests, because they measure the reduction of NA activity they are designed to be used with any NA subtype. However, because of antigenic variation and the difficulty in running large numbers of samples with either test, both tests are used only experimentally, with little chance that they could be adapted to be a rapid, sensitive, and inexpensive test that can test large numbers of samples [11].

Another one is Non-structural 1 protein DIVA, a promising system based on the detection of antibodies against a specific antigen, the NS1 protein of AI, has been deemed a good DIVA candidate. The NS1 protein is synthesized in large amounts in infected cells but is not incorporated into the mature virions, and for this reason represents the ideal candidate to elicit a specific immune response [12].

It may be possible to differentiate the epitopes that induce antibodies in vaccinated and infected animals. Luminex is a florescence microsphere immunoassay technology where microspheres can be coupled with different antigens and the profile of antibodies can be assessed [6].

In endemic setting, NSP tests can be used to support sero-surveillance exercises that assess the prevalence of infection in livestock and wildlife, especially where the results for SP tests might be complicate by the presence of vaccine-induced antibodies. When used for ruminants, a limitation of these tests is that they are unable to distinguish between convalescent and carrier animals [13].

Vaccine DIVA functionality is often limited to large viruses with increased potential for gene deletion and removal of redundant expressed antigens. Therefore, for viruses with small genomes such as paramyxoviruses where gene deletion of neutralizing antigens may reduce vaccine efficacy, alternative approaches are required to provide DIVA functionality [14].

Citation: Tsion B, Fanose T. Review on Discriminatory Tests of Immune Reaction due to Infection and Vaccination (DIVA Test). Austin J Vet Sci & Anim Husb. 2023; 10(3): 1120.