Embryo vaccination of chickens using a novel adjuvant formulation stimulates protective immunity against Eimeria maxima infection

Abstract

Our previous study demonstrated that chickens immunized subcutaneously with an Eimeria recombinant profilin protein vaccine emulsified in a Quil A/cholesterol/DDA/Carbopol (QCDC) adjuvant developed partial protection against experimental avian coccidiosis compared with animals immunized with profilin alone. Because in ovo vaccination is presently used in commercial applications worldwide throughout the poultry industry, the current study was undertaken to investigate chicken embryo vaccination with profilin plus QCDC adjuvant. Eighteen day-old embryos were immunized with isotonic saline (control), profilin alone, QCDC alone, or profilin plus QCDC, and orally challenged with live Eimeria maxima at 7 days post-hatch. Body weight gain, fecal oocyst output, and intestinal cytokine transcript levels were assessed as measures of protective immunity. While immunization with profilin alone or QCDC alone did not alter body weight gain of infected chickens compared with the saline control group, vaccination with profilin plus QCDC increased body weight gain such that it was equal to the uninfected controls. Immunization with profilin plus QCDC also reduced fecal oocyst shedding compared with unimmunized controls, although in this case QCDC failed to provide an adjuvant effect since no difference was observed between the profilin-only and profilin/QCDC groups. Finally, increased levels of transcripts encoding IL-1β, IL-15, and IFN-γ were seen in the intestinal tissues of animals given profilin plus QCDC compared with the profilin-only or QCDC-only groups. In summary, this study demonstrates an adjuvant effect of QCDC on body weight gain and intestinal cytokine responses following in ovo vaccination of chickens with an Eimeria profilin vaccine.

Fig. 1

Schematic outline of the experimental design.

Fig. 2

Effects of vaccination with profilin plus QCDC on body weight gain. Eighteen day-old embryos were immunized with PBS (control), QCDC alone (QCDC), profilin alone (Profilin), or profilin plus QCDC (Profilin/QCDC). Chickens were uninfected or orally infected with 1.0 × 10⁴ sporulated oocysts of E. maxima at 7 days post-hatch, and body weight gains between 0 and 9 days post-infection were calculated. Each bar represents the mean ± SEM (n = 12). Bars not sharing the same letters are significantly different according to the Tukey's HSD test (P < 0.05).

Fig. 3

Effects of vaccination with profilin plus QCDC on fecal oocyst shedding. Eighteen day-old embryos were immunized with PBS (control), QCDC alone (QCDC), profilin alone (Profilin), or profilin plus QCDC (Profilin/QCDC). Chickens were uninfected or orally infected with 1.0 × 10⁴ sporulated oocysts of E. maxima at 7 days post-hatch, and fecal oocyst numbers were determined between days 6 and 9 post-infection. Each bar represents the mean ± SEM (n = 12). Bars not sharing the same letters are significantly different according to the Tukey's HSD test (P < 0.05).

Fig. 4

Effect of vaccination with profilin plus QCDC on intestinal cytokine transcript levels. Eighteen day-old embryos were immunized with PBS (control), QCDC alone (QCDC), profilin alone (Profilin), or profilin plus QCDC (Profilin/QCDC). The levels of transcripts encoding IL-1β (A), IL-15 (B), and IFN-γ (C) were quantified by RT-PCR and normalized to GAPDH transcript levels at 9 days post-infection. Each bar represents the mean ± SEM from triplicate samples/bird (n = 4). Bars not sharing the same letters are significantly different according to the Tukey's HSD test (P < 0.05).