Development of an Effective Polyvalent Vaccine against both Marek's and Newcastle Diseases Based on Recombinant Marek's Disease Virus Type 1 in Commercial Chickens with Maternal Antibodies

Serological Evaluation of Turkey Herpesvirus Vector Vaccines Expressing the Hemagglutinin Gene of Avian Influenza Virus H5 Subtype under Three Different Promoters

“…Furthermore, a longer period of immunity can be expected, since MDV persists in inoculated chickens (Witter and Offenbecker, 1978;Palya et al, 2014). Also, efficacy of MDV vector vaccines does not appear to be excessively affected by the presence of maternally derived antibodies, probably because MDV replicates in a cell-associated manner (Morgan et al, 1993;Sonoda et al, 2000). Along with other factors, selection of an appropriate promoter for expression of antigen genes in MDV vectors appear to be very important for providing optimum immunity.…”

“…Marek's disease virus, including HVT, have been evaluated as viral vectors expressing protective antigen gene(s) of various poultry pathogens (Morgan et al, 1993;Darteil et al, 1995;Sonoda et al, 2000;Tsukamoto et al, 2002;Ma et al, 2014). There are several elements of MDV vector vaccines that can impact efficacy of these vaccines in chickens.…”

“…The HVT vector vaccine with the Pec promoter provided better protection than the HVT vector with the CMV promoter against challenge with IBDV. Sonoda et al (2000) reported that the MDV serotype 1 (MDV1) glycoprotein B promoter appeared to be more suitable than the simian virus 40 (SV40) late promoter for use in MDV1 vector Newcastle disease virus vaccine expressing the fusion gene, when tested in chickens with maternally derived antibodies to Newcastle disease virus. Ma et al (2014) compared five different promoters in MDV1 vector vaccines for expression of the HA gene of AIV H9N2 subtype and found that two MDV endogenous promoters (pp38 and gB) with relatively low expression activities gave better protection than the other three promoters (CMV, SV40, and p1.8 kb).…”

Progress toward the development of polyvalent vaccination strategies against multiple viral infections in chickens using herpesvirus of turkeys as vector

“…Among candidates, fowl pox virus (FPV), Newcastle disease virus (NDV), infectious laryngotracheitis virus (ILTV), Marek disease virus (MDV-1) and herpesvirus of turkeys (HVT) are receiving the most attention as potential vectors, since these viruses have restricted host ranges among avian species. 14,[16][17][18][19] The recombinant FP vector-based vaccine "Trovac AI H5" was licensed in the USA in 1998 for the immunization of poultry and an NDV-based live attenuated vaccine "NDV-H5HA" is commercially available in China. 20 However, there are some inherent shortcomings, such as lower susceptibility in very young birds due to maternally derived antibodies, that limit their effectiveness and commercial use.…”

“…This is because this vaccine can induce lifetime protection against MDV even in the presence of maternal antibodies after in ovo inoculation of the embryo or subcutaneous administration into one-day-old chicks. 19 Herpesvirus of turkeys is a naturally occurring apathogenic MDV strain (MDV-3) originally isolated from domestic turkeys and has been widely used as a vaccine against MD for several decades. Herpesvirus of turkeys vaccine is still widely used for the control of MD in countries where MDV infection is endemic.…”