Cytokine and chemokine mRNA expression profiles in tracheobronchial lymph nodes from pigs singularly infected or coinfected with porcine circovirus type 2 (PCV2) and Mycoplasma hyopneumoniae (MHYO)

The objective of this study was to determine cytokine and chemokine mRNA expression profiles in tracheobronchial lymph nodes from pigs singularly infected with porcine circovirus type 2 (PCV2), Mycoplasma hyopneumoniae (MHYO), or coinfected with both. Twenty-eight pigs were randomly assigned to one of four groups: (1) negative controls (NEG), (2) inoculated with MHYO (IMHYO), (3) inoculated with MHYO and PCV2 (CoI), and (4) inoculated with PCV2 (IPCV2). MHYO infection significantly (P<0.05) stimulated innate cytokines, IL1B and IL8. PCV2 infection significantly stimulated expression of IFNG, IL8, NOS2A and chemokines CCL2, CCL5, and CXCL10. IFNB, IL1B and IL12 were slightly increased with PCV2 infection and IFNA and IL4 were significantly downregulated. Compared to NEG pigs, coinfection resulted in a significant increase in expression of IFNG, IL1B, IL8, CCL5, CXCL10, and weak stimulation of IFNB, IL6 and IL10; IL13 and IFNA were significantly downregulated. Overall MHYO potentiated PCV2 infection by increasing IFNG and IL10 mRNA expression levels. The increase of IFNG and chemokines and decrease of IFNA in IPCV2 and CoI pigs were correlated with increased severity of lymphoid lesions and the presence of PCV2 antigen. In summary, this work provided evidence that the increased severity of lesions in PCV2 and MHYO coinfected pigs was associated mainly with the presence of PCV2 antigen and alterations of cytokine mRNA expression profiles.     

蛋鸡感染新城疫病毒后输卵管组织中病毒分布与炎症相关细胞因子mRNA的表达

通过间接免疫荧光(IFC)和实时荧光定量PCR(real-time PCR)方法研究了蛋鸡感染新城疫病毒(NDV)后输卵管组织中病毒分布及炎症相关细胞因子mRNA的表达变化。结果表明,NDV可在输卵管组织中复制,证明感染成功,NDV感染引起蛋鸡输卵管膨大部和子宫部IL-2、IL-6、IL-1β、IFN-β、CXCLi1、CXCLi2及CCR5mRNA mRNA表达上调;在感染120h后,膨大部IL-2、IFN-β和IL-1βmRNA表达达到峰值,分别为健康对照组的137倍、95.1倍和15.9倍;子宫部在感染第9天达到峰值,分别为36.2倍、59.9倍和10.3倍。在感染前3d,IFN-αmRNA在膨大部的表达为下调的趋势,而从感染第5天开始上调;而子宫部IFN-α的mRNA表达均上调。NDV感染后趋化因子CXCLi1、CXCLi2及CCR5mRNA的在膨大部和子宫部表达均上调,其中膨大部CXCLi1、CXCLi2和CCR5mRNA上调的最高值分别为20.5倍、78.3倍和22.1倍;其在子宫部分别上调5.5倍、64.3倍、25.5倍。总的来说,NDV能感染蛋鸡输卵管组织并引起IL-2、IL-6、IL-1β、IFN-β、CXCLi1、CXCLi2及CCR5mRNA表达上调,这些细胞因子mRNA表达的上调可能与输卵管炎症的发生有关。     

Role of the suppressor of cytokine signaling 2 (SOCS2) during meningoencephalitis caused by Bovine herpesvirus 5 (BoHV-5)

The role of suppressors of cytokine signaling (SOCS) in meningoencephalitis caused by Bovine herpesvirus 5 (BoHV-5) was evaluated by intracranial infection in C57BL/6 wild-type mice (WT) and SOCS2 deficient mice (SOCS2^−/−). Both infected groups presented weight loss, ruffled fur and hunched posture. Additionally, infected SOCS2^−/− mice showed swollen chamfer and progressive depression. Infected WT animals developed mild meningitis, characterized by infiltration of mononuclear cells. Moreover, viral DNA was detected in liver and lung from infected WT group. This group also showed elevated brain levels of IFN-γ, IL-10, CXCL1 and CCL5, when compared with non-infected WT animals. Brain inflammation was exacerbated in infected SOCS2^−/− mice with widespread distribution of the virus and increased brain levels of TNF-α, IFN-γ, IL-10, IL-12, CXCL1 and CCL5, when compared with WT infected mice. Moreover, infected SOCS2 deficient mice exhibited reduced brain mRNA expression of IFNα and IFNβ and increased expression of mRNA of SOCS1, compared with infected WT mice. Taken together, our study provides an insight into the role of SOCS2 in modulating the immune response to BoHV-5 infection.     

Equine herpesvirus type-1 modulates CCL2, CCL3, CCL5, CXCL9, and CXCL10 chemokine expression

Equine herpesvirus type 1 (EHV-1) is highly prevalent in horses and causes rhinopneumonitis, abortion, and encephalopathy. Studies on the related human herpes simplex virus and of murine models of EHV-1 suggest that chemokines play important roles in coordinating of innate and adaptive immune responses, and thus effective control of herpesvirus infection and prevention of severe clinical disease. Here, equine peripheral blood mononuclear cells (PBMC) were infected with one of three EHV-1 strains, which differ in pathogenicity (RacL11, NY03=abortogenic, Ab4=neurogenic). Changes in CCL2, CCL3, CCL5, CXCL9 and CXCL10 chemokine gene expression relative to non-infected PBMC were measured by real-time PCR. CXCL9 and CXCL10 gene expression was up-regulated 10h post infection and decreased to the level of non-infected cells after 24h. CCL2 and CCL3 were significantly down-regulated 24h post infection with NY03 and Ab4. CCL5 was up-regulated 24h after infection with RacL11. Ab4 infected PBMC had significantly lower expression of all chemokines except CCL2 24h post infection then RacL11 infected cells. While there was not a significant difference between NY03 and the other strains, there was a trend with each chemokine toward NY03 inducing less expression then RacL11 but more then Ab4. The data suggested that EHV-1 infection of PBMC induced up-regulation of inflammatory chemokines CCL5, CXCL9 and CXCL10, and down-regulation of chemotactic CCL2 and CCL3. The data also implies that different EHV-1 strains have varying effects on all five chemokines, with the nuropathogenic strain, Ab4, having the greatest suppressive potential.     

The porcine skin associated T-cell homing chemokine CCL27: molecular cloning and mRNA expression in piglets infected experimentally with Staphylococcus hyicus

CCL27 (also named CTACK, ALP, ILC and ESkine) is a CC chemokine primarily expressed by keratinocytes of the skin. The cognate receptor of CCL27 named CCR10 (GPR-2), is also expressed in skin-derived cells, and in addition by a subset of peripheral blood T-cells and in a variety of other tissues. In this paper, we report the cloning of porcine CCL27 cDNA and investigation of CCL27 mRNA expression in Staphylococcus hyicus infected piglets. At the protein level, 77 and 74% homology was found to human and mouse CCL27 sequences, respectively. The results of the expression analyses show that CCL27 mRNA is upregulated in the skin of infected piglets and to a lesser extent in piglets recovered from disease and without clinical signs of infection, indicating a role for CCL27 both during inflammation and after recovery from an infection.     

Pathogenicity of emerging Japanese type 1 porcine reproductive and respiratory syndrome virus in experimentally infected pigs

To clarify the pathogenicity of Japanese type 1 porcine reproductive and respiratory syndrome virus (PRRSV) isolate in experimentally infected pigs, we evaluated clinical signs and monitored viremia for 21 days post-inoculation (dpi). Lungs were mottled, tanned and reddish in appearance; had lesions predominantly in the cranial, middle and accessory lobes; and failed to collapse at 10 dpi. Although microscopic lesions of lungs were reproduced using the Japanese emerging type 1 PRRSV isolate under experimental conditions, no significant differences were noted between the challenge and control groups regarding mean rectal temperature and daily weight gain. These results provide useful insights into the limited pathogenicity of single infection with the Japanese type 1 PRRSV isolate in piglets, which differ from findings in reported field cases.     

Acute phase protein response during subclinical infection of pigs with H1N1 swine influenza virus

In the present study acute phase proteins (APPs) responses in pigs after subclinical infection with H1N1 swine influenza virus (SwH1N1) were evaluated. Fourteen 5 weeks old, seronegative piglets, both sexes were used. Ten of them were infected intranasally with SwH1N1. C-reactive protein (CRP), haptoglobin (Hp), serum amyloid A (SAA) and pig major acute phase protein (Pig-MAP) concentrations in serum were measured using commercial ELISAs. No significant clinical signs were observed in any of the infected pigs, however, all infected animals developed specific antibodies against SwH1N1 and viral shedding was observed from 2 to 5dpi. Only concentrations of Hp and SAA were significantly induced after infection, with mean maximum levels from days 1 to 2 post infection (dpi). The concentrations of CRP and Pig-MAP remained generally unchanged, however in half of infected pigs the concentration of CRP tended to increase at 1dpi (but without statistical significance). The results of our study confirmed that monitoring of APPs may be useful for detection of subclinically infected pigs. The use of SAA or Hp and Pig-MAP may be a valuable in combination [i.e. Hp (increased concentration) and Pig-MAP (unchanged concentration)] to detect subclinically SIV infected pigs, or to identify pigs actually producing a large amount of virus. Additional studies need to be done in order to confirm these findings.     

Antiviral effect of Saccharomyces cerevisiae beta-glucan to swine influenza virus by increased production of interferon-gamma and nitric oxide

The aim of these experiments was to investigate the potential antiviral effect of Saccharomyces cerevisiae beta-glucan on the pneumonia induced by swine influenza virus (SIV). Forty colostrum-deprived 5-day-old piglets were randomly divided into four groups of 10. The 20 pigs in groups 1 and 2 were administered Saccharomyces cerevisiae beta-glucan orally (50 mg/day/pig; En-Bio Technology Co., Ltd) for 3 days before SIV infection and those in groups 3 and 4 were given culture medium/diluent alone. Groups 1 and 3 were inoculated intranasally with 3 ml of tissue culture fluid containing 2 x 10(6) tissue culture infective doses 50% (TCID(50))/ml of SIV and those in groups 2 and 4 were exposed in the same manner to uninfected cell culture supernatant. The microscopic lung lesions induced by SIV infection (group 1 pigs) were significantly more severe than those induced by infection in animals pre-administered beta-glucan (group 3) (P < 0.05). Significantly more SIV nucleic acid was detected in the lungs of pigs experimentally infected with SIV only (group 1) at 5, 7 and 10 days post-inoculation (dpi) compared with lungs from pigs pre-administered beta-glucan and infected with SIV (group 3) (P < 0.05). The concentrations of interferon-gamma (IFN-gamma) and nitric oxide (NO) in bronchoalveolar lavage fluid from pigs pre-administered beta-glucan and infected with SIV (group 3) were significantly higher than for any other group at 7 and 10 dpi for IFN-gamma, and at 5, 7 and 10 dpi for NO (P < 0.05). Saccharomyces cerevisiae beta-glucan reduced the pulmonary lesion score and viral replication rate in SIV-infected pigs. These findings support the potential application of beta-glucan as prophylactic/treatment agent in influenza virus infection.     

Hemostatic alterations in pigs fed sublethal doses of Sarcocystis miescheriana

Effects of non-lethal Sarcocystis miescheriana infections on the blood coagulation system were investigated. Nine pigs were inoculated orally with 2 X 10(5) sporocysts (Group A) and nine pigs (Group B) served as non-infected controls. Blood samples were taken from the vena jugularis externa every 2 or 3 days until 19 days post-infection (dpi). The following parameters were investigated: partial thromboplastin time (PTT), prothrombin time (PT), thrombin time (TT), thrombin coagulase time (TCT), fibrinogen (FIB), factor (F) VIII, F XI, F XII, antithrombin III (AT III), alpha 2 macroglobulin (alpha 2 MG), alpha 2 antiplasmin (alpha 2 AP), pre-kallikrein (PK), and the number of circulating thrombocytes. All infected pigs suffered from acute sarcocystiosis between 12 and 19 dpi. Clinical illness was most severe from 14 to 17 dpi. At this time, PTT and FIB increased, and TT and TCT decreased slightly. The activities of the clotting factors increased at 17 and 19 dpi. However, only F VIII activity was significantly higher in the infected pigs than in the controls at 17 and 19 dpi. PK was significantly lower in the infected pigs at 12, 14, and 17 dpi. Thrombocyte counts were reduced with the onset of the acute phase of illness and some pigs had marked thrombocytopenia. These results indicate low-grade disseminated intravascular coagulation (DIC) in the course of mild S. miescheriana infections in pigs.     

Respiratory function and pulmonary lesions in pigs infected with porcine reproductive and respiratory syndrome virus

Pulmonary dysfunction was evaluated in pigs infected with porcine reproductive and respiratory syndrome virus (PRRSV, isolate VR-2332) and compared to clinical and pathological findings. Infected pigs developed fever, reduced appetite, respiratory distress and dullness at 9 days post-inoculation (dpi). Non-invasive pulmonary function tests using impulse oscillometry and rebreathing of test gases (He, CO) revealed peripheral airway obstruction, reduced lung compliance and reduced lung CO-transfer factor. PRRSV-induced pulmonary dysfunction was most marked at 9–18 dpi and was accompanied by a significantly increased respiratory rate and decreased tidal volume. Expiration was affected more than inspiration. On histopathological examination, multifocal areas of interstitial pneumonia (more severe and extensive at 10 dpi than 21 dpi) were identified as a possible structural basis for reduced lung compliance and gas exchange disturbances.     

Porcine reproductive and respiratory syndrome virus (PRRSV) influences infection dynamics of porcine circovirus type 2 (PCV2) subtypes PCV2a and PCV2b by prolonging PCV2 viremia and shedding

The objective of this study was to determine the effect of porcine reproductive and respiratory syndrome virus (PRRSV) infection on porcine circovirus type 2 (PCV2) subtypes a (PCV2a) or b (PCV2b) viremia and shedding characteristics in oral, nasal and fecal samples in experimentally infected pigs. Twenty-three, 2- to 6-week-old pigs were randomly divided into five groups: negative control (n=3), PCV2a-I (n=5), PCV2a-PRRSV-CoI (n=5), PCV2b-I (n=5), and PCV2b-PRRSV-CoI (n=5). Blood, oral, nasal and fecal swabs were collected in regular intervals from day post inoculation (dpi) 0 until dpi 70 and tested by quantitative real-time PCR for the presence and amount of PCV2 DNA and by ELISA for the presence of PCV2-specific antibodies. The results indicate that there were significantly (P<0.05) higher loads of PCV2a and PCV2b DNA in serum, oral swabs, nasal swabs and fecal swabs and a higher prevalence of detectable PCV2 antigen in tissues of pigs concurrently infected with PCV2 and PRRSV compared to pigs singularly infected with PCV2 further confirming that PRRSV enhances replication of PCV2. Moreover, PRRSV infection significantly prolonged the presence of PCV2 DNA in serum and increased the amount of PCV2 DNA in oral and nasal secretions and fecal excretions in the later stages of infection between dpi 28 and 70. Shedding patterns were similar between groups infected with PCV2a and PCV2b, indicating that there was no subtype-specific interaction with the PRRSV isolate used in this study. The results from this study highlight the interaction between PRRSV and PCV2 and the importance of controlling PRRSV infection in order to reduce PCV2 virus loads in pig populations.     

Effect of porcine circovirus type 2a or 2b on infection kinetics and pathogenicity of two genetically divergent strains of porcine reproductive and respiratory syndrome virus in the conventional pig model

To determine differences in infection kinetics of two temporally and genetically different type 2 porcine reproductive and respiratory syndrome virus (PRRSV) isolates in vivo with and without concurrent porcine circovirus (PCV) type 2a or 2b infection, 62 pigs were randomly assigned to one of seven groups: negative controls (n=8); pigs coinfected with a 1992 PRRSV strain (VR-2385) and PCV2a (CoI-92-2a; n=9), pigs coinfected with VR-2385 and PCV2b (CoI-92-2b; n=9), pigs coinfected with a 2006 PRRSV strain (NC16845b) and PCV2a (CoI-06-2a; n=9), pigs coinfected with NC16845b and PCV2b (CoI-06-2b; n=9), pigs infected with VR-2385 (n=9), and pigs infected with NC16845b (n=9). Blood samples were collected before inoculation and at day post-inoculation (dpi) 3, 6, 9 and 12 and tested for the presence of PRRSV antibody and RNA, PCV2 antibody and DNA, complete blood counts, and interferon gamma (IFN-γ) levels. Regardless of concurrent PCV2 infection, VR-2385 initially replicated at higher levels and reached peak replication levels at dpi 6. Pigs infected with VR-2385 had significantly higher amounts of viral RNA in serum on both dpi 3 and dpi 6, compared to pigs infected with NC16845b. The peak of NC16845b virus replication occurred between dpi 9 and dpi 12 and was associated with a delayed anti-PRRSV antibody response in these pigs. PCV2 coinfection resulted in significantly more severe macroscopic and microscopic lung lesions and a stronger anti-PRRSV IgG response compared to pigs infected with PRRSV alone. This work further emphasizes in vivo replication differences among PRRSV strains and the importance of coinfecting pathogens.     

Distribution of porcine monocytes in different lymphoid tissues and the lungs during experimental Actinobacillus pleuropneumoniae infection and the role of chemokines

Monocytes play an essential role in the defense against bacterial pathogens. Bone marrow (BM) and peripheral blood (PB) monocytes in pigs consist of the main “steady-state” subpopulations: CD14^hi/CD163^-/SLA-DR^- and CD14^low/CD163⁺/SLA-DR⁺. During inflammation, the subpopulation of “inflammatory” monocytes expressing very high levels of CD163, but lacking the SLA-DR molecule (being CD14^low/CD163⁺/SLA-DR^-) appears in the BM and PB and replaces the CD14^low/CD163⁺/SLA-DR⁺ subpopulation. However, current knowledge of monocyte migration into inflamed tissues in pigs is limited. The aim of the present study was to evaluate the distribution of “inflammatory” CD14^low/CD163⁺/SLA-DR^- monocytes during experimental inflammation induced by Actinobacillus pleuropneumoniae (APP) and a possible role for chemokines in attracting “inflammatory” CD14^low/CD163⁺/SLA-DR^- monocytes into the tissues. Monocyte subpopulations were detected by flow cytometry. Chemokines and chemokine receptors were detected by RT-qPCR. The “steady-state” monocytes were found in the BM, PB, spleen and lungs of control pigs. After APP-infection, “inflammatory” monocytes replaced the “steady-state” subpopulation in BM, PB, spleen and moreover, they appeared in an unaffected area, demarcation zone and necrotic area of the lungs and in tracheobronchial lymph nodes. They did not appear in mesenteric lymph nodes. Levels of mRNA for various chemokines with their appropriate receptors were found to be elevated in BM (CCL3-CCR1/CCR5, CCL8-CCR2/CCR5, CCL19-CCR7), necrotic area of the lungs (CCL3-CCR1, CCL5-CCR1/CCR3, CCL11-CCR3, CCL22/CCR4) and tracheobronchial lymph nodes (CCL3-CCR1) and therefore they could play a role in attracting monocytes into inflamed tissues. In conclusion, “inflammatory” monocytes appear in different lymphoid tissues and the lungs after APP infection in pigs. Various chemokines could drive this process.     

Laminar chemokine mRNA concentrations in horses with carbohydrate overload-induced laminitis

Chemokines play a vital role in leukocyte activation and emigration that reportedly plays a central role in laminar injury in equine laminitis. The purpose of this study was to evaluate the pattern of laminar chemokine expression in horses in the classical carbohydrate overload (CHO)-model of laminitis. Laminar samples were obtained 24h following water administration in the control group (CON, n=8), and at the onset of fever (≥ 102°F, 12-22 h post CHO, DEV group, n=8) and at the onset of lameness (20-48 h post CHO, LAM group, n=8) in induced horses. Real time quantitative PCR was performed on all samples in order to determine laminar mRNA concentrations of both CXC chemokines (CXCL1, CXCL6, CXCL8) and CC chemokines (CCL2 [MCP-1], CCL3 [MIP-1α], and CCL8 [MCP-2]). Data were subjected to ANOVA followed by Student-Newman-Keuls (P<0.05). Laminar mRNA concentrations for all CXC chemokines were increased (P<0.05) at both the DEV and LAM horses when compared to the control horses, whereas mRNA concentrations of CCL2 and CCL8 were only increased in the LAM horses when compared to controls and the DEV horses. When taken in context with our previous studies, CXCL1, CXCL6 and CXCL8 increases precede peak laminar leukocyte accumulation. Additionally, CCL2 and CCL8 expression corroborate previous reports of monocyte/macrophage accumulation in affected laminae. Compared with previous studies, our findings demonstrate that increased laminar CXC chemokine expression consistently precedes peak leukocyte accumulation and onset of lameness in CHO laminitis models. Chemokine antagonists may be considered as possible therapeutic targets to decrease the influx of leukocytes that occurs during the development of equine laminitis.     

An assessment of the duration of Mycoplasma hyopneumoniae infection in an experimentally infected population of pigs

Mycoplasma hyopneumoniae (M. hyopneumoniae) is the primary pathogen of enzootic pneumonia (EP), a highly prevalent respiratory disease that affects pigs worldwide. Previous studies have demonstrated that M. hyopneumoniae infection can be longer than 185 days; however, the total duration of infection has not been determined yet. Therefore, the objective of this study was to determine the duration of M. hyopneumoniae infection in asymptomatic carriers. To achieve our goal, 60 pigs were inoculated with M. hyopneumoniae strain 232 and the persistence of M. hyopneumoniae in the respiratory tract was assessed by detection of the bacterial DNA in bronchial swabs and the ability of the infected pigs to transmit the pathogen to sentinels. Infection of the inoculated animals was demonstrated by the detection of M. hyopneumoniae DNA in nasal swabs, seroconversion to the bacteria and the onset of dry coughing. Experimentally infected pigs shed M. hyopneumoniae prior to and after the cough was observed. M. hyopneumoniae DNA was detected in 100% of experimentally infected pigs at 94 days post infection (dpi), 61% at 214dpi and 0% at 254dpi. Experimentally infected pigs transmitted the bacteria to sentinels at 80 and 200dpi. Results of this study have demonstrated that M. hyopneumoniae infected pigs can be incubatory as well as convalescent carriers of the pathogen and that convalescent carriers can remain infectious for up to 200 days. Total clearance of M. hyopneumoniae in the group was evidenced, demonstrating that duration of M. hyopneumoniae infection lasts less than 254 days.     

Evaluation of the effects of animal age, concurrent bacterial infection, and pathogenicity of porcine reproductive and respiratory syndrome virus on virus concentration in pigs

OBJECTIVE: To evaluate the influences of animal age, bacterial coinfection, and porcine reproductive and respiratory syndrome virus (PRRSV) isolate pathogenicity on virus concentration in pigs. ANIMALS: Twenty-one 2-month-old pigs and eighteen 6-month-old pigs. PROCEDURE: Pigs were grouped according to age and infected with mildly virulent or virulent isolates of PRRSV. The role of concurrent bacterial infection was assessed by infecting selected pigs with Mycoplasma hyopneumoniae 21 days prior to inoculation with PRRSV. On alternating days, blood and swab specimens of nasal secretions and oropharyngeal secretions were collected. On day 21 after inoculation with PRRSV, selected tissues were harvested. Concentrations of PRRSV were determined by use of quantitative real-time PCR and expressed in units of TCID(50) per milliliter (sera and swab specimens) or TCID(50) per gram (tissue specimens). RESULTS: Concentrations of virus were higher in blood and tonsils of pigs infected with virulent PRRSV. Pigs infected with virulent PRRSV and M hyopneumoniae had significantly higher concentrations of viral RNA in lymphoid and tonsillar tissue. Coinfection with M hyopneumoniae resulted in a higher viral load in oropharyngeal swab specimens and blood samples, independent of virulence of the PRRSV isolate. Two-month-old pigs had significantly higher viral loads in lymph nodes, lungs, and tracheal swab specimens than did 6-month-old pigs, independent of virulence of the PRRSV isolate. CONCLUSIONS AND CLINICAL RELEVANCE: Multiple factors affect PRRSV concentration in pigs, including pathogenicity of the PRRSV isolate, age, and concurrent infection with M hyopneumoniae.     

Up-regulated expression of PD-1 and its ligands during acute Classical Swine Fever virus infection in swine

In order to investigate the relationship between the PD-1 pathway and impairment of immune responses with the CSFV infection, the mRNA expression of PD-1 and its ligands were evaluated by quantitative polymerase chain reaction (qPCR) during artificial CSFV infection. Simultaneously, expression of IL-2 and IL-10 mRNA were detected. The T cell proliferation and CSFV load in plasma were also measured. Results showed that the expression of PD-1 and its ligands mRNA were significantly increased (p < 0.01) in PBMC from 3 to 7 days post infection (dpi). Meanwhile the level of IL-10 was up-regulated (p < 0.01). The IL-2 mRNA was not obviously changed but it is significantly increased from 14 dpi. The T cell proliferation was notably decreased at 7 dpi. The CSFV load was also increased in plasma. Overall, our results suggest that the expression of PD-1 and its ligands were up-regulated and probably correlated with immune inhibition during acute CSFV infection.