Development of vaccine-induced immunity against TRT in turkeys depends remarkably on the level of maternal antibodies and the age of birds on the day of vaccination

Abstract

BackgroundAvian Metapneumovirus (aMPV) infections are a huge economical issue for the poultry industry worldwide. Although maternal antibodies do not protect turkey poults against turkey rhinotracheitis (TRT), almost no studies have been conducted so far regarding the impact of these antibodies on vaccine induced immunity development against aMPV infection. We conducted four experiments on commercial turkeys aimed at comparing local humoral and cell mediated immune response of maternally delivered anti-aMPV antibody positive (MDA+; Experiment I and II) and negative (MDA-; Experiment III and IV) turkeys following vaccination with an attenuated live aMPV subtype A vaccine at the day of hatch (Experiment I and III) or at two weeks of age (Experiment II and IV).ResultsRegardless of the birds’ age, vaccination of MDA- turkeys resulted in strong stimulation of CD8+ T lymphocytes in the Harderian gland and tracheal mucosa, whereas vaccination of MDA+ birds stimulated mainly CD4+ T cells in those structures. An increase in the level of anti-aMPV IgY antibodies was noted in the serum (but not in tracheal washings) as early as 7 days after vaccination, but only in birds possessing low levels (MDA+ birds vaccinated at 2 weeks of age) or no maternal anti-aMPV antibodies at the time of vaccination. In MDA+ turkeys vaccinated at hatch, the decrease in serum levels of maternal anti-aMPV antibodies proceeded faster (in comparison to control group), which, together with faster viral clearance, indicates that maternal antibodies can inhibit vaccine virus replication and influence the development of vaccine-induced immunity.ConclusionThis study provides the first documented evidence that the frequency of TRT outbreaks in the field and/or failure of TRT vaccination could be correlated with differences in the immunological status and/or age of vaccinated turkeys.

Three-step Anti-aMPV IgA Expression Profile Evaluation in Turkeys of Different Immunological Status after TRT Vaccination

“…The birds were not vaccinated at the hatchery against TRT, which was confirmed with RT-PCR (Smialek et al 2015) The turkeys were housed in isolated units maintained at a PCL 3 (physical containment level 3) facility. They were vaccinated occulonasaly with 10 4 of tissue infectious dose 50% (TCID 50 ) / bird of aMPV/A strain BUT1 #8544 commercial attenuated vaccine reconstituted in milli-q water.…”

“…HG and TC were pooled from 5-6 birds per sample (in different groups the number of birds per sample was equal in each sampling), which produced 4 samples of each organ for flow cytometry and ELIPOT analysis. Tracheal washings were collected from 10 birds in each group as described previously (Smialek et al 2015). Following centrifugation, the supernatant and serum samples were stored at -20 o C for ELISA.…”

“…Isolation of mononuclear cells from HG and TC, with the use of Percoll density gradient solution, were performed as described previously (Smialek et al 2015).…”

“…Further steps of flow cytometry data acquisition and dual platform analysis allowing the calculation of B IgA + absolute cell count (ACC) were performed as described previously (Smialek et al 2015). Data were expressed as mean x-fold change in ACC of IgA + B lymphocytes in vaccinated groups relative to non-vaccinated groups.…”

“…Considering the above, and our previous findings concerning the differences in humoral and cell-mediated immunity stimulation after TRT vaccination of turkeys with or without maternally derived antibodies (MDA) (Smialek et al 2015), the aim of this study was to investigate the impact of MDA on stimulation and antigen memory acquisition of B IgA + cells and the production of anti-aMPV IgA in the URT after TRT vaccination of turkeys.…”