International Journal of Molecular Veterinary Research, 2024, Vol.14, No.6, 235-243 http://animalscipublisher.com/index.php/ijmvr 237 3 Vaccine Development and Types 3.1 Overview of vaccines for Newcastle disease Newcastle disease (ND) is a significant threat to poultry, necessitating effective vaccination strategies. Vaccines for ND have been developed over the past 60 years, with a focus on preventing the replication and infection of the Newcastle disease virus (NDV) (Shafaati et al., 2024). The World Organisation for Animal Health emphasizes the importance of ND vaccination due to its economic impact and rapid spread potential. Traditional vaccines include live and inactivated forms, which have been widely used since the 1950s. Recent advancements have introduced recombinant and viral-vectored vaccines, which express NDV proteins to enhance immune responses (Figure 2) (Dimitrov et al., 2016; Fulber and Kamen, 2022). Figure 2 Overview of production processes for viral-vectored vaccines in (A) embryonated chicken eggs (ECEs) and (B) suspension cell cultures in stirred-tank bioreactors (Adopted from Fulber and Kamen, 2022) 3.2 Types of NDV vaccines: live, inactivated, and recombinant NDV vaccines are categorized into live, inactivated, and recombinant types. Live vaccines, such as the LaSota and B1 strains, are known for their efficacy and safety in both avian and non-avian species6. Inactivated vaccines are often used in combination with live vaccines to boost immunity. Recombinant vaccines, including those based on genotype VII.1.1, have shown superior protection by closely matching circulating field isolates (Dewidar et al., 2022). These recombinant vaccines can be engineered to express multiple antigens, providing broader protection against various NDV strains (Xu et al., 2020; Jamil et al., 2022). 3.3 Efficacy, safety, and challenges in vaccine development The efficacy of NDV vaccines varies depending on the type and genetic match to circulating strains. Recombinant vaccines, particularly those using the VG/GA strain backbone, have demonstrated high efficacy and reduced virus shedding (Dewidar et al., 2022). Safety is a critical consideration, with avirulent strains like LaSota being preferred for their established safety profiles (Kim and Samal, 2016). However, challenges remain, such as ensuring even vaccine application in large flocks and maintaining the cold chain for thermo-labile vaccines. Additionally, maternal antibodies can interfere with vaccine efficacy, necessitating strategies to overcome this obstacle (Dimitrov et al., 2016). The development of thermostable vaccines and multi-epitope constructs are promising approaches to enhance vaccine stability and immune response (Tan et al., 2020; Jamil et al., 2022).
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