Efficacy of Carbopol as an Adjuvant for Inactivated Rift Valley Fever Vaccine

Abstract

The purpose of the current study was to examine the immune response of sheep given the Rift Valley Fever virus vaccination adjuvanted with Carbopol®. Fifteen sheep were divided into three groups of five each. The first group received the ALOH adjuvanted inactivated RVF vaccination. The second group received the carbopol adjuvanted inactivated RVF vaccination. In the third group, no immunizations were administered as a control. In order to evaluate the Cellular immune response and the humeral immune response, the generated vaccines were evaluated by measuring the levels of interleukin, interferon and antibody levels using the enzyme linked immunosorbant assay (ELISA) and serum neutralization test (SNT). The efficacy of the vaccines was assessed using the challenge test in mice. The findings showed that the Carbopol® Adjuvanted inactivated RVF vaccine generated a potent immune response better than the traditionally produced ALOH adjuvanted vaccine.

Introduction

Acute infectious zoonotic arthropod-borne Rift Valley Fever disease is caused by a virus that affects a wide variety of animal species leading to significant financial losses for animals. The illness was first discovered in sheep in Kenya’s Rift Valley area in 1931, and RVF has been resurfacing for a number of years since then [1]. The illness is significantly dispersed in Africa and Asia produces huge losses amongst lambs and calves. Illness in animals is characterised by sever clinical manifestations and high mortality as well as multiple abortions and deaths in sheep, goats and camels [2]. Vaccination effectively prevents pathological illness by promoting innate, nonspecific protection, which in turn leads to the development of an adaptive immune response to combat newly introduced pathogens [3]. One of the major items in progress of vaccine formulation is adjuvant. It may alter the immunity. Consequently, it is among the most important elements in the manufacturing process of vaccine productions [4]. Specifically, the antigen-adjuvant complex activates pattern-recognition receptor (PRR) pathways by acting as pathogen-associated molecular patterns (PAMPs). This causes the activation of innate immune cells with the production of cytokines and chemokines [5]. The aluminum hydroxide adjuvant creates a “depot” at the injection site where antigen is generated gradually, resulting in a longer exposure to lymphocytes and antigen-presenting cells [6]. Cell-mediated immunity, especially cytotoxic T-cell responses, is poorly produced by aluminum hydroxide [7]. Also [8] said that the severe local tissue irritation, prolonged inflammatory response at injection sites, low activation of cell-mediated immunity, and tendency to elicit unwanted immunoglobulin IgE are some of the drawbacks of aluminum-based adjuvants. Additionally, vaccinations based on aluminum are poor at generating antiviral immunity. Therefore, it is necessary to find alternatives to aluminum hydroxide to improve the quality of the vaccine and to obtain a higher and longer level of immunity, beside stimulation of cell mediated immune response.

According to [9], adjuvants may determine the specific kind of immune response by stimulating the immune response and lengthening the duration of immunity. Carbopol was previously utilized in pigeon, swine, and horse vaccinations [10]-[12]. The adjuvant criteria of polyacrylic acids, designated by the term carbomers, may vary significantly with the number of carboxyl groups present in the final molecule. Polyacrylic acid polymers termed carbomers have been evaluated as adjuvants in animal vaccines with no side effect [9] [10] [13]-[16]. The systemic adjuvant activity of adding carbomer to animal immunizations includes pro-inflammatory T cell sensitization, fast leukocyte recruitment, proinflammatory cytokine release, and quick antigen uptake by the inflammatory monocytes [17].

It was shown that Carbomer 934 is actually immunogenic and may be a relevant alternative to oil in avian species for which safety is a major concern. Aluminum hydroxide was proved to be less immunogenic than carbomer and the last was totally safe by vaccination of the young goslings with inducing a good serological response [18]. Water-soluble acrylic acid (carbomer) was employed as an adjuvant in a study to increase the immunogenicity of the rabies vaccine, and the results showed that it is effective and powerful [19]. It was proposed that carbomers be used with other adjuvants to produce a potentially strong immunological response.

This work was designed to provide high protective, long-lasting immunity against RVF virus through the enhancement of the immunogenicity of the inactivated RVF vaccine using carbopol as adjuvant.

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Materials

2.4. Adjuvants

2.4.1. Carbopol

Lubrizol Co. provided it as a powder, which was then mixed in hot water to create stock solution that was 1% aqueous [20]. After autoclaving the prepared solutions for 20 minutes at 121˚C to heat sterilize them, it was kept at 4˚C until it was needed again.

2.4.2. Aluminum Hydroxide Gel

It was purchased as Lot No. 11-274-30 from Alliance Bio Company, USA, and added to the produced local vaccination at a 20% concentration [21].

Magd, D.M.A., Hassan, A.M., Mohamed, Y.M., Eita, R.A. and Mohamed, H.A. (2025) Efficacy of Carbopol as an Adjuvant for Inactivated Rift Valley Fever Vaccine. Open Journal of Veterinary Medicine, 15, 115-131. doi: 10.4236/ojvm.2025.155007.