Classical Swine Fever: pathology of bone marrow

Twenty pigs were inoculated with a virulent isolate (Quillota strain) of classical swine fever (CSF) virus to determine the chronological development of lesions in bone marrow. Histopathologic, ultrastructural and immunohistochemical (detection of viral antigen gp55, myeloid-histiocyte antigen, CD3 antigen, and FVIII-rag), and morphometric techniques were employed. Viral antigen was detected from 2 days postinfection (dpi) in stromal and haematopoitic cells, and severe atrophy related to apoptosis of haematopoitic cells was observed. Megakaryocytes (MKs) did not show significant changes in number, but there were important qualitative changes including 1) increased numbers of cloud-nuclei MKs, microMKs, apoptotic MKs, and atypical nucleated MKs and 2) decreased number of typical nucleated MKs. Morphometric study of these cells showed a decrease in cytoplasmic area. MK infection was detected from 2 dpi, but in a small percentage of cells. Myeloid cells showed quantitative changes, with an increase in granulocyte numbers. Apoptosis of lymphocytes and viral infection of erythroblasts were also observed. The main changes in stroma were depletion of T lymphocytes in the middle phase of the experiment and macrophages. Viral infection was also observed in these cells. MK lesions suggest dysmegakaryocytopoiesis, which would aggravate the thrombocytopenia already present and could be responsible for it. Granulocyte changes would lead to the appearance of circulating immature forms, whereas lymphocyte apoptosis in bone marrow would contribute to lymphopenia.     

Cutaneous lesions in experimental acute and subacute African swine fever: an immunohistopathological and ultrastructural study

Histopathological, immunohistochemical and ultrastructural cutaneous changes are described in acute and subacute forms of experimental African Swine Fever (ASF). Fourteen 3-month-old Large White cross pigs were infected intramuscularly with the Dominican Republic 78 (DR78) ASF virus isolate and euthanized in pairs on alternatives days (3 to 17) post-inoculation (dpi). Three pigs were found dead at 8, 10 and 13 dpi, respectively. Antibodies against viral antigen Vp73, human fibrinogen, glycoprotein IIIa and Factor VIII-ra were used to evaluate viral antigen distribution, fibrin microthrombi and platelets in dermal vessels, respectively. Cutaneous lesions were characterised by vascular changes ranging from hyperaemia, mild oedema, scarce fibrin microthrombi and microhaemorrhages in euthanized animals, to generalized fibrin microthrombosis and microhaemorrhages in dead pigs. Secondary pustules and superficial folliculitis were observed in two animals dead at 10 and 13 dpi. Diffuse cytoplasmic Vp73 labelling was found in numerous intravascular monocytes and dermal macrophages. Ultrastructural studies showed mature viral particles in the lumen of dermal vessels but viral replication was not observed; nonetheless, microtubuloreticular structures were observed in the cytoplasm of some endothelial cells and macrophages which showed cytopathic effects, signs of cell activation or degeneration. Morphological and immunohistochemical evidences of platelet activation, degranulation and consumption were observed from 5 dpi onward.     

Functional impairment of PRRSV-specific peripheral CD3+CD8high cells

The replication of porcine reproductive and respiratory syndrome virus (PRRSV) in lungs and lymphoid tissues of PRRSV-infected pigs is already strongly reduced before the appearance of neutralizing antibodies, indicating that other immune mechanisms are involved in eliminating PRRSV at those sites. This study aimed to determine whether PRRSV Lelystad virus (LV)-specific cytotoxic T-lymphocytes (CTL) can efficiently eliminate PRRSV-infected alveolar macrophages. Therefore, CTL assays were performed with PRRSV-infected alveolar macrophages as target cells and autologous peripheral blood mononuclear cells (PBMC) from PRRSV-infected pigs as a source of PRRSV-specific CTL. PBMC of 3 PRRSV-infected pigs were used either directly in CTL assays, or following restimulation in vitro. CTL assays with pseudorabies virus (PRV) Begonia-infected alveolar macrophages and autologous PBMC, from 2 PRV Begonia-inoculated pigs, were performed for validation of the assays. In freshly isolated PBMC, derived from PRRSV-infected pigs, CTL activity towards PRRSV-infected macrophages was not detected until the end of the experiment (56 days post infection – dpi). Restimulating the PBMC with PRRSV in vitro resulted in proliferation of CD3⁺CD8^high cells starting from 14 dpi. Although CD3⁺CD8^high cells are generally considered to be CTL, CTL activity was not detected in PRRSV-restimulated PBMC of the 3 pigs until 49 dpi. A weak PRRSV-specific CTL activity was observed only at 56 dpi in PRRSV-restimulated PBMC of one pig. In contrast, a clear CTL activity was observed in PRV Begonia-restimulated PBMC, derived from PRV Begonia-infected pigs, starting from 21 dpi. This study indicates that PBMC of PRRSV-infected pigs contain proliferating CD3⁺CD8^high cells upon restimulation in vitro, but these PBMC fail to exert CTL activity towards PRRSV-infected alveolar macrophages.     

Increase in chemokines CXCL10 and CCL2 in blood from pigs infected with high compared to low virulence African swine fever virus isolates

Modulation of the expression of chemokines and chemokine receptors in whole blood was compared following infection of pigs with high and low virulence isolates of African swine fever virus. Levels of mRNAs for CCL2, CCL3L1, CCL4, CXCL10, CCR1 and CCR5 were significantly increased in at least one time point following infection in two experiments and CCL5, CCR9 and CXCR4 mRNA were significantly increased in one of the experiments. The results showed that greatest fold increases in mRNAs for CXCL10 and CCL2 were observed following infection of pigs. CXCL10 mRNA was increased by up to 15 fold in infected compared to uninfected pigs. CXCL10 protein was also detected in serum from pigs infected with the high virulence Benin 97/1 isolate. Levels of CCL2 mRNA were increased in pigs infected with high virulence Benin 97/1 isolate compared to low virulence OURT88/3 isolate and this correlated with an increase of greater than 30 fold in levels of CCL2 protein detected in serum from pigs infected with this isolate. An increase in overall chemotaxis active compounds in defibrinated plasma samples from Benin 97/1 infected pigs was observed at 3 days post-infection (dpi) and a decrease by 7 dpi as measured by chemotaxis assay using normal pig leucocytes in vitro. Increased levels of CXCL10 may either contribute to the activation of lymphocyte priming toward the Th1 phenotype or induction of T lymphocyte apoptosis. Increased levels of CCL2, a chemoattractant for macrophages, may result in increased recruitment of monocytes from bone marrow thus increasing the pool of cells susceptible to infection.     

Increased porcine circovirus type 2 replication in porcine leukocytes in vitro and in vivo by concanavalin A stimulation

Previously, it was shown that modulation of the immune system enhances porcine circovirus type 2 (PCV2) replication in pigs. In the present study, the effect of the mitogen concanavalin A (ConA) on PCV2 replication was investigated. Since ConA induces T-lymphocyte activation and initiates the production of interferon-gamma (IFN-gamma), a cytokine that enhances PCV2 replication in porcine epithelial and monocytic cell lines in vitro, it was examined if the effects observed with ConA were mediated by IFN-gamma. In an in vitro study, ConA but not IFN-gamma enhanced PCV2 replication in peripheral blood mononuclear cells (PBMC). Up to 2.08% and 0.96% of PBMC were antigen positive for PCV2 strains 1121 and Stoon-1010, respectively, and a low virus production was observed. PCV2-infected PBMC were identified as CD4(+) (40%), CD8(+) (54%) and IgM(+) (11%). In a subsequent in vivo study, caesarean-derived colostrum-deprived piglets were injected with ConA or IFN-gamma 12h before inoculation and every 3 days for 9 days after inoculation with strain 1121. PCV2 was isolated from inguinal lymph node biopsies from 10 days post-inoculation (dpi) in ConA-treated pigs and from 15dpi in non-treated and IFN-gamma-treated pigs. ConA increased PCV2 replication levels, but disease was not observed. Half of the ConA-treated and IFN-gamma-treated pigs showed a delayed humoral immune response, but this delay did not result in increased PCV2 replication in these pigs. These experiments demonstrated that ConA enhances PCV2 replication in PBMC in vitro and in lymphoid tissues in vivo.     

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.     

Porcine circovirus type 2 (PCV2)-infection and re-inoculation with homologous or heterologous strains: virological, serological, pathological and clinical effects in growing pigs

Long-term PCV2 infection and/or concurrent infection with genotypes PCV2a and PCV2b may play a role in the development of clinical porcine circovirus-associated disease (PCVAD). To evaluate this premise, 24 11-week-old specific pathogen-free (SPF) pigs were randomly assigned to 1 of 4 treatments: negative controls, a single inoculation with PCV2a, single inoculation followed by re-inoculation with a homologous PCV2a strain, or repeated inoculations with heterologous strains (PCV2a, PCV2b). Pigs were evaluated for clinical signs daily through 140 days post inoculation (dpi). Serum samples were collected every other day from dpi 0 through 14 and weekly thereafter. PCV2-inoculated pigs were viremic by dpi 2 and 13 of 18 pigs remained viremic at 140 dpi. No statistical differences in the onset, level, or duration of PCV2 viremia were detected among treatment groups. Anti-PCV2 antibodies were detected between 14 and 28 dpi and were present through 140 dpi without statistical differences in antibody response among treatment groups. In the current study, pigs had extended viremia combined with detectable tissue PCV2 antigen levels despite the presence of high levels of anti-PCV2 antibody; however, no clinical disease was observed.     

Experimental reproduction of severe disease in CD/CD pigs concurrently infected with type 2 porcine circovirus and porcine reproductive and respiratory syndrome virus

Three-week-old cesarean-derived colostrum-deprived (CD/CD) pigs were inoculated with porcine circovirus type 2 (PCV2, n = 19), porcine reproductive and respiratory syndrome virus (PRRSV, n = 13), concurrent PCV2 and PRRSV (PCV2/PRRSV, n = 17), or a sham inoculum (n = 12) to compare the independent and combined effects of these agents. Necropsies were performed at 7, 10, 14, 21, 35, and 49 days postinoculation (dpi) or when pigs became moribund. By 10 dpi, PCV2/PRRSV-inoculated pigs had severe dyspnea, lethargy, and occasional icterus; after 10 dpi, mortality in this group was 10/11 (91%), and all PCV2/ PRRSV-inoculated pigs were dead by 20 dpi. PCV2-inoculated pigs developed lethargy and sporadic icterus, and 8/19 (42%) developed exudative epidermitis; mortality was 5/19 (26%). PRRSV-inoculated pigs developed dyspnea and mild lethargy that resolved by 28 dpi. Microscopic lesions consistent with postweaning multisystemic wasting syndrome (PMWS) were present in both PCV2- and PCV2/PRRSV-inoculated pigs and included lymphoid depletion, necrotizing hepatitis, mild necrotizing bronchiolitis, and infiltrates of macrophages that occasionally contained basophilic intracytoplasmic inclusion bodies in lymphoid and other tissues. PCV2/ PRRSV-inoculated pigs also had severe proliferative interstitial pneumonia and more consistent hepatic lesions. The most severe lesions contained the greatest number of PCV2 antigen-containing cells. PRRSV-inoculated pigs had moderate proliferative interstitial pneumonia but did not develop bronchiolar or hepatic lesions or lymphoid depletion. All groups remained seronegative to porcine parvovirus. The results indicate that 1) PCV2 coinfection increases the severity of PRRSV-induced interstitial pneumonia in CD/CD pigs and 2) PCV2 but not PRRSV induces the lymphoid depletion, granulomatous inflammation, and necrotizing hepatitis characteristic of PMWS.     

猪支原体肺炎活疫苗（168株）气溶胶免疫后呼吸道sIgA分泌及抗原存留规律

猪支原体肺炎是由猪肺炎支原体(Mycoplasma hyopneumoniae ,Mhp)引起的猪的一种慢性呼吸道疾病,严重影响养猪业发展,活疫苗气溶胶免疫是防治该病的新措施。为研究猪肺炎支原体活疫苗(168株)经气溶胶免疫后,疫苗株在免疫猪肺内的占位存留规律,选用3周龄不吃初乳猪27头,随机分为3组,G1气溶胶免疫组12头,G2肺内免疫组12头,同时设立阴性对照3头。分别于免疫后第2 h、7 d、14 d及28 d进行鼻拭子Mhp sIgA检测以及血清抗体检测。另外在上述时间点分别宰杀G1和G2组各3头,对照组在实验组免疫后第28 d宰杀,采集肺泡灌洗液,分别进行Mhp sIgA检测及Mhp疫苗株含量检测。结果显示:(1)所有试验猪至实验结束,Mhp血清抗体未出现转阳现象;(2)鼻拭子sIgA水平G1组在免疫后第14 d与对照组相比上升,差异具有显著统计学意义(p <0.05);G2组在免疫后第7 d和14 d与相应的对照组相比上升,差异具有显著统计学意义(p <0.05),各时间点G1组与G2组sIgA水平差异不具备统计学意义(p >0.05);(3)G1组肺泡灌洗液中的 sIgA在免疫后14 d部分转阳(阳性率33.33%),28 d全部转阳(阳性率100%);G2组在免疫14 d时已全部转阳(阳性率100%),各时间点G1组与G2组sIgA水平差异不具备统计学意义(p >0.05);(4)气溶胶免疫组肺泡灌洗液内Mhp疫苗株浓度在免疫后第2 h、7 d、14 d和28 d分别是相应肺内免疫组的0.37倍、1.01倍、0.88倍以及0.52倍。猪支原体肺炎活疫苗(168株)经气溶胶免疫后,和肺内免疫一样可以诱导免疫猪的局部黏膜免疫以及具有同等的占位效应,且经气溶胶免疫的疫苗株在免疫仔猪体内的增殖水平可能与其诱导的黏膜免疫水平相关。     

Localisation of swine hepatitis E virus in experimentally infected pigs

The distribution of intravenously inoculated swine hepatitis E virus (HEV) was assessed by in situ hybridisation for a period of 50 days. Evidence of apparent clinical disease was found in only one pig in the HEV infected group. The only gross lesion observed was mildly enlarged mesenteric lymph nodes at 50 days post infection (dpi). Histopathologically, mild lymphoplasmacytic infiltration and focal hepatocellular necrotic lesions were found in HEV-infected pigs. Swine HEV nucleic acids were detected by RT-PCR in the faeces at 3 dpi in 100% of the 18 pigs infected with the virus. Thereafter, the number of positives declined.The most consistent and intense signal was found in the liver of infected animals using in situ hybridisation. The positive cells were hepatocytes, Kupffer cells, bile epithelial cells and interstitial lymphocytes. Swine HEV RNA was localised in the cytoplasm of the hepatocytes, with a slightly granular pattern of staining, but hybridisation signals were not observed in degenerative or vacuolated hepatocytes. HEV was much less frequently detected in extrahepatic tissues such as lymph nodes, tonsil, spleen and small and large intestine. It was concluded that swine HEV had replicated primarily in the hepatocytes and infection resulted in subclinical infection with minimal histopathological changes in the liver.     

Histopathologic and immunohistochemical characterization of Nipah virus infection in the guinea pig

Mortality rate in humans infected with Nipah virus (NiV) has been reported as high as 92%. Humans infected with NiV show a widespread multisystemic vasculitis with most severe clinical and pathologic manifestations in the brain, lungs, and spleen. The purpose of this study was to study pathologic and immunohistochemical findings in guinea pigs infected with NiV. Of 28 animals inoculated intraperitoneally, only 2 survived the infection, and most died between 4 and 8 days postinoculation (dpi). Viral antigen with minimal pathologic changes was first detected 2 dpi in lymph nodes and spleen. More severe changes were noted in these organs 4-8 dpi, where pathologic damage had a vasocentric distribution and viral antigen was abundant in vascular endothelium, tunica media, adventitia, as well as in macrophages lining sinuses. The urinary bladder, uterus, and ovaries were also affected with necrosis and acute inflammation. In these organs, immunohistochemical positive staining was intense in blood vessels, epithelial cells, and ovarian follicles. Approximately 50% of the animals that died or were euthanized in extremis had evidence of viral antigen and histopathologic changes in brain, especially involving meninges and ependymal cells, with lesser changes in the neural parenchyma. A unifying feature of the damage for all affected tissues was necrosis and inflammation of the vasculature, chiefly in arterioles, capillaries, and venules. Inoculation of guinea pigs intraperitoneally with NiV produces a disease with considerable resemblance to the disease in humans, but with reduced pulmonary involvement and marked infection of urinary bladder and the female reproductive tract.     

Viral distribution and lesions in Kunming mice experimentally infected with porcine circovirus type 2b

The viral distribution and lesions in Kunming mice experimentally infected with porcine circovirus type 2b (PCV-2b) were investigated. Seventy special pathogen free mice were divided into 2 groups with 35 mice in each group. The test group (TG) was infected with PCV-2b, the control group (CG) was inoculated with sterile cell cultures. Five mice in each group were sacrificed at 3, 7, 14, 21, 28, 35 and 42 dpi (day post infection), respectively. Necropsies were performed on all mice and tissues were collected for testing by histopathology, immunohistochemistry, transmission electron microscope (TEM) and polymerase chain reaction (PCR). Apoptosis and necrosis in lymphoid organs were observed in virus-infected mice, and became severe from 14 to 28 dpi. The proportion of PCV-2b antigen-positive cells was moderate in lung, heart, thymus, liver or kidney, and low in brain from TG. In spleen and cervical lymph node, the proportions of PCV-2b antigen-positive cells were low to high from 7 to 28 dpi, and moderate from 35 to 42 dpi. PCV-2b DNA was detected in all tissues examined in TG from 7 to 42 dpi. Viral inclusion bodies presented in the cytoplasm of lymphocytes, macrophages, hepatocytes, podocytes, neurocytes, spermatids and uterine epithelial cells in TG. In CG, no viruses and viral lesions were detected. PCV-2b could replicate in mice, and PCV-2b associated lesions in mice were similar to those observed in pigs. The present results indicate that it is possible to use Kunming mouse as an animal model for PMWS research.     

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.     

Lymphocyte apoptosis and thrombocytopenia in spleen during classical swine fever: role of macrophages and cytokines

Thirty-two Large White x Landrace pigs, 4 months old, were inoculated with the classical swine fever (CSF) or hog cholera virus strain "Alfort" in order to identify the mechanism responsible for the lymphopenia and thrombocytopenia observed in the spleen during the experimental induction of disease, by immunohistochemical and ultrastructural techniques. Results showed a progressive depletion of splenic lymphoid structures and evidence of platelet aggregation processes. Lymphoid depletion was due to lymphocyte apoptosis, which could not be ascribed to the direct action of the virus on these cells; direct virus action could play only a secondary role in the death of these cells. Absence of severe tissue and endothelial damage, together with moderate procoagulant cytokine levels in the serum, suggest that these pathologies can be ruled out as the cause of platelet aggregation and thrombocytopenia in CSF. Monocyte/macrophages were the main target cells for the CSF virus, and they exhibited phagocytic and secretory activation leading to the synthesis and release of tumor necrosis factor alpha, which proved to be the chief mediator, followed by IL-6, IL-1alpha, and C1q complement component. In view of their characteristics, TNF-alpha and, to a lesser extent, IL-1alpha and IL-6 appear to be the major cytokines involved in the pathogenesis of lymphocytopenia and thrombocytopenia; a clear spatial and temporal relationship was observed between these two phenomena.     

猪繁殖与呼吸综合征病毒核酸在仔猪呼吸及繁殖系统动态分布的研究

应用针对 PRRSV ATCC VR- 2 332株基因组 ORF6片段的 4 6 3bp的 c DNA探针 ,对 4 5日龄 SPF仔猪分别人工感染 ATCC VR- 2 332株及北京分离株 B96 - 4后不同时间呼吸系统及繁殖系统组织中病毒核酸的分布进行了研究。结果显示 ,在感染后 30 h,即可在鼻黏膜、气管、肺脏、睾丸、附睾、精囊、前列腺、子宫、扁桃体等组织中检出阳性杂交信号 ,且一直持续到感染后 2 8天。其中扁桃体中病毒的数目远多于呼吸系统及繁殖系统组织中的数目 ,说明扁桃体可作为活体检查的目的器官之一     

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.     

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.     

Hepatic immune response in calves during acute subclinical infection with bovine viral diarrhoea virus type 1

Eight colostrum-deprived calves aged 8-12 weeks were inoculated intranasally with a non-cytopathic strain of bovine viral diarrhoea virus (BVDV) genotype-1 and the effects on the hepatic immune response were studied. Two calves were sacrificed at each of 3, 6, 9 and 14 days post-inoculation (dpi) and two uninoculated animals were used as negative controls. BVDV was detected in hepatic macrophages and monocytes from 3 to 14dpi and in Küpffer cells (KCs) from 6 to 14dpi. Increases in the numbers of MAC387(+) KCs and monocytes, but not interstitial macrophages, differentiated by morphological features, were evident in the liver following inoculation with BVDV. There was a substantial increase in the number of monocytes positive for tumour necrosis factor (TNF)-α, but only small increases in the numbers of TNF-α(+) KCs and interstitial macrophages and interleukin (IL)-6(+) monocytes, KCs and interstitial macrophages. There was an increase in the number of interstitial CD3(+) T lymphocytes in the liver, but no substantial changes in the numbers of circulating CD3(+) T lymphocytes, interstitial or circulating CD4(+) or CD8(+) T lymphocytes, or CD79αcy(+) B lymphocytes. Serum haptoglobin and serum amyloid A increased transiently at 12dpi. Upregulation of some pro-inflammatory cytokines by hepatic macrophages is evident in subclinical acute BVDV type 1 infection in calves.