Viral Kinetics, Shedding Profile, and Transmission of Serotype 1 Marek's Disease Vaccine Rispens/CVI988 in Maternal Antibody-Free Chickens

Abstract

Probably the most effective current vaccine against Marek's disease is the live Rispens (CVI988) attenuated serotype 1 Marek's disease virus (MDV). It is unknown whether the currently available Rispens vaccines transmit effectively between chickens. To investigate the kinetics and shedding of three commercially available strains of this virus and the extent of lateral transmission, we measured the shedding rate in dander and the viral load in peripheral blood lymphocytes (PBLs) and feather tips over time. Four identical climate-controlled rooms were stocked with a total of 70 specific-pathogen-free chickens for 56 days. In each of three rooms, 10 chickens were vaccinated with one of the commercial vaccines at day old and left in contact with 10 unvaccinated chickens. The fourth room contained 10 unvaccinated control chickens. As determined by MDV-specific quantitative real-time polymerase chain reaction of weekly room dust and individual PBLs and feather tip samples, the vaccine virus was shed from the vaccinated chickens in dander from day 7 postvaccination and transmitted effectively from vaccinated to in-contact chickens with a lag period of 2-3 wk. Viral load in PBLs and feather tips peaked at days 7 and 14, respectively, and declined thereafter, whereas viral load in dust increased rapidly to day 21 and then increased gradually thereafter. Antibody titer at day 56 was correlated with earlier measures of MDV load in PBLs but not feather tips or dust. These results show that currently available Rispens CVI988 vaccine virus is shed in significant quantities from vaccinated chickens and transmits effectively between chickens.

Chicken skin virome analyzed by high-throughput sequencing shows a composition highly different from human skin

“…The replication of CVI988 virus in the feather follicle has been previously reported [22,23] and its shedding attested by the presence of viral DNA in dust [23]. Baigent and al. reported high levels (10 6 to 10 8 ) of CVI988 genome copy numbers per 10 6 feather tip cells, from 10-to 28-day postvaccination in maternal antibody-free SFP chickens [22].…”

“…Baigent and al. reported high levels (10 6 to 10 8 ) of CVI988 genome copy numbers per 10 6 feather tip cells, from 10-to 28-day postvaccination in maternal antibody-free SFP chickens [22]. Other authors reported titers that never exceeded 10 6 and was below 10 2 at 56 days in maternal antibody-free White leghorn vaccinated at 1 day [23]. Considering that Rispens may be less shed than HVT (especially over time), and that only 20 % of the birds had received Rispens, the absence of GaHV-2 in this analysis is not totally surprising.…”

Replication kinetics and shedding of very virulent Marek's disease virus and vaccinal Rispens/CVI988 virus during single and mixed infections varying in order and interval between infections

“…Good progress has been made in studying the kinetics of infection with mixed infections of MDV with HVT and MDV-2 vaccines (Islam and Walkden-Brown, 2007;Islam et al, 2006b). For single infections with the Rispens virus the kinetics of viral replication in the early post infection stage in feather tips and lymphocytes has been reported (Baigent et al, 2005b) as have the longer term kinetics in lymphocytes, feather tips and dust, and the efficacy of transmission to unvaccinated chickens (Islam et al, 2013a). With the development of real time quantitative PCR (qPCR) assays which can differentiate between Rispens and pathogenic serotype 1 MDV the possibility of examining the effects kinetics of mixed infections of Rispens and pathogenic MDV became possible.…”

Vaccination and Host Marek's Disease-Resistance Genotype Significantly Reduce Oncogenic <b><i>Gallid alphaherpesvirus 2</i></b> Telomere Integration in Host Birds

“…The genomes of these strains are highly similar to the oncogenic strains, but crucial differences exist . The MD vaccine viruses replicate in host cells and transmit to other birds [Baigent et al, 2005;Islam et al, 2007;Tan et al, 2007;Gimeno et al, 2011;Islam et al, 2013;], but do not induce disease or lymphomas [Calnek and Witter, 1997]. Despite improved understanding of vaccine-related immunity [Witter, 1984;Osterrieder et al, 2006], an explanation for the anti-tumor effect of vaccination has not yet been established.…”