Efficacy, humoral, and cell-mediated immune response of inactivated fowl adenovirus 8b propagated in chicken embryo liver cells using bioreactor in broiler chickens

Abstract

Background and Aim: Fowl adenovirus (FAdV) 8b causes inclusion body hepatitis, resulting in major economic losses globally among chickens. The objectives were to inactivate FAdV 8b isolate propagated in chicken embryo liver (CEL) cells using a stirred tank bioreactor (UPM08136P5B1) and determine the humoral and cell-mediated immune response, efficacy, and virus shedding in broiler chickens. Materials and Methods: The FAdV 8b isolate UPM08136P5B1 was inactivated using binary ethyleneimine, adjuvanted with Montanide 71VG, inoculated into day-old broiler chickens in a booster group (BG) and non-booster group (NBG), and challenged with a pathogenic FAdV 8b strain. Clinical signs, gross lesions, body weight (BW), liver: body weight ratio, FAdV antibody titer using enzyme-linked immunosorbent assay, and histopathological changes were recorded. The CD3+, CD4+, and CD8+ T-lymphocyte profiles of the liver, spleen, and thymus using flow cytometry, and viral load in liver and cloacal shedding using quantitative polymerase chain reaction were evaluated. Results: Chickens in the challenged control group (CCG) exhibited mild clinical signs, gross lesions, and histopathological changes, which were absent in the inoculated groups, and had lower BW and higher liver BW ratio than chickens in the unchallenged control group (UCG); BG and NBG on 35- and 42-days post-inoculation (DPI). Chickens in NBG and BG had higher antibodies than UCG on 7, 21, 35, and 42 DPI. The challenged BG and NBG produced higher antibodies than the CCG on 35 DPI. T-lymphocytes were higher among the inoculated groups than UCG in the liver, spleen, and thymus. Inoculated challenged groups recorded higher CD3+, CD4+, and CD8+ T-lymphocytes on 35 and 42 DPI than CCG. The challenged control group had a significantly higher viral load in the liver than challenged that in BG on 35 DPI and BG and NBG on 42 DPI. The challenged control group had significantly higher challenge FAdV shedding than challenged inoculated groups on 35 and NBG on 42 DPI. Conclusion: UPM08136P5B1 was successfully inactivated and mixed with Montanide 71VG. The inactivated vaccine candidate that induced humoral and cellular immunity was effective, reduced FAdV load in the liver, and shedding in the cloaca, and could be useful against FAdV 8b infections in chickens.

Attenuation and molecular characterization of fowl adenovirus 8b propagated in a bioreactor and its immunogenicity, efficacy, and virus shedding in broiler chickens

“…Attenuation of viruses involves serial passage in susceptible host cells. Typical CPEs were observed with UPM08136 passage isolates on CEL cells, similar to FAdV 4 on CEL cells [ 15 ]; however, delayed CPEs started occurring from P14 to P15, which could indicate that the infectivity of the isolate is reducing, an indication of probable attenuation. Reduced pathogenicity and retained immunogenicity of viruses are expected through serial passages [ 22 ].…”

“…Aseptically harvested liver tissue from 15-day-old SPF CEE rats was used to prepare CEL cells as previously described [ 15 ]. Confluent CEL cells in tissue culture (TC) flasks were used to passage UPM08136CELP0 20 times to yield CELP1–CELP20, and molecular analysis was performed every five passages.…”

“…FAdV 8b (UPM08136P20) was propagated once in a stirred tank bioreactor using CEL cells adapted to Cytodex™ 1 microcarriers to produce UPM08136P20B1 [ 16 ], whereas inactivated UPM08136P5B1 was prepared as previously reported [ 18 ] and used as attenuated and inactivated inocula, respectively, in the experimental animal trial. UPM11142CELP5 isolates passaged 2× in SPF CEE to obtain UPM11142P5EP2 with a titer of 10 8 egg Infective dose (EID)50/mL were filtered and used as a challenge virus for the chicken trial.…”

“…On day 28 pi, 0.5 mL of UPM11142CEL5EP2 (10 8 TCID50/mL) was administered intramuscularly as a challenge to eight chickens in each group. Sampling was performed as previously described by Ugwu et al [ 18 ].…”

“…Two-way repeated-measures analysis of variance on Statistical Package for the Social Sciences (SPSS) 25.0 for Windows (SPSS Inc., Chicago, IL, USA) was used to analyze the differences within and between groups with a 5% probability using the post hoc Tukey HSD test [ 18 ]. A probability value of p < 0.05 was considered significant.…”