Levamisole Enhances Cell-Mediated Immune Responses and Reduces Shedding of H9N2 Avian Influenza Virus in Japanese Quails (Coturnix coturnix japonica)

Abstract

Problem statement: Regarding the role of Japanese quails (Coturnix coturnix japonica) in reassortment and spreading of avian influenza (AI) viruses and inadequate protection of vaccination in this species, the present study aimed to evaluate the effect of levamisole as an immunomodulatory agent on cell-mediated immunity (CMI), antibody responses and shedding of H9N2 AI virus in experimentally infected quails. Approach: On day 20 of age, 100 quails randomly allocated into 4 equal groups. Birds in groups 2, 3 and 4 were inoculated with virus where group 1 kept as control. Groups 3 and 4 orally received 15 mg kg^-1 levamisole for three consecutive days just before virus inoculation which was repeated 10 days post inoculation (PI) only in group 4. Antibody titers and CMI of all birds were assayed by HI and delayed type hypersensitivity (DTH) test respectively and virus detection in fecal and tracheal samples performed by RT-PCR method. Data analyzed by one-way ANOVA and Tukey’s test. Results: Levamisole in both regimens had no appreciable effect on antibody titers (p>0.05) while repeated regimen resulted in higher CMI response than group 2 at 48 and 72 h post DTH test (p = 0.011 and p = 0.031 respectively). Total fecal samples positive for virus from birds in group 3 and 4 were 34.4 and 40% lower than group 2 respectively. For trachea, the positive samples were 33.3% (group 3) and 46.7% (group 4) lower than group 2. Moreover; fecal and tracheal samples from levamisole treated birds (especially from group 4) became void of virus earlier than group 2. Conclusion/Recommendations: Levamisole administration in a repeated regimen enhances CMI response against H9N2 AI virus and reduces virus shedding in quails. This may pave the road for further investigations on potential positive effects of this agent on prevention and management of H9N2 AI infections in quail industry.