Abstract: Effect of MDV-1 vaccines administered alone or with HVT on the development of the chicken embryo immune system
In previous studies, we have demonstrated that HVT (herpes virus of turkey) hastens the immunocompetence of chickens when administered in ovo.
HVT immunostimulant effect is stronger than that of known adjuvants such as poly I:C. Preliminary studies have also shown that in ovo administration of CVI988 had minor to no adjuvant effect, but it enhanced the transcription of various cytokines when administered together with HVT.
In the present study, we have evaluated how in ovo administration of two MDV-1 vaccines (CVI988 and CVI-LTR), alone or in combination with HVT, affects the percentage of activated T cells and macrophages in 1-day-old chickens.
Our results confirm that HVT strongly activates T cells more efficiently than either CVI988 or CVI-LTR. However, administration of CVI-LTR together with HVT had the strongest immunostimulant effect on activation of CD4+ and CD8α+ T cells; significantly higher than HVT alone.
In addition, CVI-LTR and CVI-LTR + HVT, but not other treatments, increased the proportion of γδT CD8αα cells, which have been related to cytotoxic ability. A decrease in CD8β and activated CD8β T cells was found in the group vaccinated with CVI-LTR but not in the one vaccinated with CVI-LTR + HVT.
Our results show that administration of CVI-LTR with HVT significantly enhances the adjuvant effect of HVT and can render chickens more immunocompetent at hatch.
This study was conducted by Abdelhamid Fares, Raveendra Kulkarni, Nagwa Khaled, Deanna Emanuel, Isabel Gimeno, North Carolina State University; and Christa Goodell, William Stanley, Boehringer Ingelheim. It was presented at the 2025 conference of the American Association of Avian Pathologists.
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