Effects Of Threonine And Tryptophan On Immune Response Of Growing Pigs Inoculated Porcine Reproductive And Respiratory Syndrome Virus Modified Live Vaccine

Threonine and Tryptophan is an essential amino acid for pigs.the benefit of threonine and tryptophan supplementation for immune response has been established for increased antibody production,serum IgG levels and modulating T-cell proliferation.For virus infect or vaccine inoculate,modulating T-cell proliferation and increased antibody production,serum IgG levels lead to several Threonine and Tryptophan metabolites,thus may reduce immune response.This study was conducted to investigate Effect of TTR on immune response of growing pigs inoculated porcine reproductive and respiratory syndrome virus modified live vaccine.Twenty-eight crossbred male pigs(Landrace×Yorkshire) weighing 20 kg were obtained from a herd(noninfected,nonvaccinated for PRRS) from the Gaojin Pig Breeding Company located near Dayi.Ten pigs were inoculated with PRRSV before the initiation of the experiment.On the average BW of 29 kg,half of the pigs continued to receive the control diet,while the rest pigs were fed Threonine and Tryptophan rich diet.This Experiment was designed with Threonine and Tryptophan administration,PRRSV specific antibody and PRRS vaccination being the three factors.Therefore,six treatments each employing a group of pigs were applied:PRRSV positive and treated with PRRS vaccinated and CON diet against PRRS(PV+CON group),PRRSV positive treated with PRRS vaccinated and TTR diet against PRRS(PV+TTR group), non PRRSV infect and treated with PRRS vaccinated and CON diet against PRRS (V+CON group),non PRRSV infect and treated with PRRS vaccinated and TTR diet against PRRS(V-TTRgroup),non PRRSV infect and non PRRS vaccinated treated with CON diet against PRRS(CON-group) and non PRRSV infect and non PRRS vaccinated treated with TTR diet against PRRS(TTR-group).in day 0 of the experiment and re-vaccined on day 35 of the experiment.Groups CON and TTR were mock-vaccinated intramuscular with 2 ml of phosphate buffered saline in day 0 and day 35of the experiment.Serum samples were collected from all pigs at -21,0,7,14,21,28,35,49 days of post vaccination.At day 49 post vaccination.,pigs were euthanatized and necropsied,tonsils,tracheobronchial and medial iliac lymph nodes and lungs,were collected from each animal,serum samples were randomly ordered and analyzed for PRRSV-specific antibodies,immunoglobulin and serum cytokines.Tissue sample were randomly ordered and analyzed for PRRSV load and TLR3 and TLR7 by PCR(lungs and lymph nodes) and histopathology(lungs and lymph nodes).The results were as follows:1,After post vaccination,PRRSv-specific antibody titer of PBS treatment groups was nearly kept at a stabilized level and was lower(P＜0.05) than that of PRRS vaccination groups.In the PV and PVT group,all pigs were seropositive(S/P＞0.4) to PRRSV by ELISA test at days7 to days 49 post vaccination,besides were significant higher the other four groups on days 14 and 21 post vaccination(P＜0.05).2,The PRRSV-vaccined pigs had higher(P＜0.05)levels of both IFN-γ,IL-10and IL-1βthan control pigs at 14,28 and 35 d post vaccination(P＜0.05).In PRRS negative vaccination group,TTR diet significant higher levels of IFN-γat 35 d post vaccination(P＜0.05).but no differences were detected in the levels of IL-1βand IL-10 in vaccination groups.3,For PRRS vaccination group,the TLR3 mRNA was significantly(p＜0.05) higher than that of PRRSV-infected pigs at 49 dpv.The mRNA levels of TLR3 and 7 in lymph nodes of TTR-dieted pigs were significantly(p＜0.05) higher than those of CON-dieted pigs.In PRRS positive vaccination group,The mRNA levels of TLR7 in lungs of TTR-dieted pigs were significantly(p＜0.05) higher than those of CON-dieted pigs.In PRRS negative vaccination group,The mRNA levels of TLR3 in lungs of TTR-dieted pigs were enhance.4,For PRRS positive vaccination group,pigs developed acute multifocal or mild interstitial pneumonia.For PRRS negative vaccination group,Alveolar septa were mildly thickened by infiltrates of fewer macrophages and fewer plasma cells.These results demonstrated that:1,Supplement of threonine and tryptophan diet enhance PRRS vaccine induce levels of PRRSV-specific antibody and Neutralizing antibody titre.2,Supplement of threonine and tryptophan diet could up-regulated the lungs and lymph nodes TLRs 3,7mRNA expression and increase Serum IFN-γlevels. supplement of threonine and tryptophan dietary help to activation of immune recognition system,enhance humoral-mediated immunity and cell-mediated immunity,mitigate tissue damage,thus Threonine and Tryptophan enhance vaccine induced immune response.