Effect of Pullet Vaccination on Development and Longevity of Immunity.

Emily Aston,Mark Jackwood,Brian Jordan,Susan Williams,Maricarmen García

doi:10.3390/v11020135

Abstract

Avian respiratory disease causes significant economic losses in commercial poultry. Because of the need to protect long-lived poultry against respiratory tract pathogens from an early age, vaccination programs for pullets typically involve serial administration of a variety of vaccines, including infectious bronchitis virus (IBV), Newcastle disease virus (NDV), and infectious laryngotracheitis virus (ILTV). Often the interval between vaccinations is only a matter of weeks, yet it is unknown whether the development of immunity and protection against challenge when vaccines are given in short succession occurs in these birds, something known as viral interference. Our objective was to determine whether serially administered, live attenuated vaccines against IBV, NDV, and ILTV influence the development and longevity of immunity and protection against challenge in long-lived birds. Based on a typical pullet vaccination program, specific-pathogen-free white leghorns were administered multiple live attenuated vaccines against IBV, NDV, and ILTV until 16 weeks of age (WOA), after which certain groups were challenged with IBV, NDV, or ILTV at 20, 24, 28, 32, and 36 WOA. Five days post-challenge, viral load, clinical signs, ciliostasis, tracheal histopathology, and antibody titers in serum and tears were evaluated. We demonstrate that pullets serially administered live attenuated vaccines against IBV, NDV, and ILTV were protected against homologous challenge with IBV, NDV, or ILTV for at least 36 weeks, and conclude that the interval between vaccinations used in this study (at least 2 weeks) did not interfere with protection. This information is important because it shows that a typical pullet vaccination program consisting of serially administered live attenuated vaccines against multiple respiratory pathogens can result in the development of protective immunity against each disease agent.

Highlights

Vaccination against respiratory viral disease is standard practice in commercial poultry operations.Both live and killed vaccines are administered to poultry, and live vaccines are commonly used for a variety of pathogens because they are effective when mass applied and are relatively economical [1].In general, live vaccines induce local and cell-mediated immunity and provide a broader protective response than killed vaccines, whereas killed vaccines primarily induce humoral immunity and tend to be antigen-specific
At 5 days following challenge with infectious bronchitis virus (IBV) GA98, vaccinated/challenged birds had significantly lower RNA loads compared to positive controls at all collection times and in all tissue samples, with the exception of cecal tonsil at 24 weeks of age (WOA) (Table 1)
Clinical signs of IBV infection measured at 5 days post-challenge were significantly reduced in vaccinated/challenged birds when compared to positive controls in all weeks except 28 WOA, but trends in clinical sign scores were numerically lower among vaccinated/challenged birds (Table 2)

Summary

Introduction

Vaccination against respiratory viral disease is standard practice in commercial poultry operations.Both live and killed vaccines are administered to poultry, and live vaccines are commonly used for a variety of pathogens because they are effective when mass applied and are relatively economical [1].In general, live vaccines induce local and cell-mediated immunity and provide a broader protective response than killed vaccines, whereas killed vaccines primarily induce humoral immunity and tend to be antigen-specific. Vaccination against respiratory viral disease is standard practice in commercial poultry operations. Both live and killed vaccines are administered to poultry, and live vaccines are commonly used for a variety of pathogens because they are effective when mass applied and are relatively economical [1]. The duration of immunity achieved following live vaccine administration depends on the age and type of bird, levels of maternal immunity, disease targeted by the vaccine, Viruses 2019, 11, 135; doi:10.3390/v11020135 www.mdpi.com/journal/viruses. Live vaccines are generally administered to young birds to achieve early protection, and layers and breeders are boosted with either live or inactivated vaccines, which vary based on their similarity to the circulating field viruses [2]

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