Antigen In Spleen Research Articles

The Lone Star tick, Amblyomma americanum, salivary factors exacerbate the clinical outcome of Heartland virus disease in a small animal model

Heartland virus was first isolated in 2009 from two patients in Missouri and is transmitted by the Lone Star tick, Amblyomma americanum. To understand disease transmission and pathogenesis, it is necessary to develop an animal model which utilizes the natural route of transmission and manifests in a manner similar to documented human cases. Herein we describe our investigations on identifying A129 mice as the most appropriate small animal model for HRTV pathogenesis that mimics human clinical outcomes. We further investigated the impact of tick saliva in enhancing pathogen transmission and clinical outcomes. Our investigations revealed an increase in viral load in the groups of mice that received both virus and tick salivary gland extract (SGE). Spleens of all infected mice showed extramedullary hematopoiesis (EH), depleted white pulp, and absence of germinal centers. This observation mimics the splenomegaly observed in natural human cases. In the group that received both HRTV and tick SGE, the clinical outcome of HRTV infection was exacerbated compared to HRTV only infection. EH scores and the presence of viral antigens in spleen were higher in mice that received both HRTV and tick SGE. In conclusion, we have developed a small animal model that mimics natural human infection and also demonstrated the impact of tick salivary factors in exacerbating the HRTV infection.

Exposure to a combination of MWCNTs and DBP causes splenic toxicity in mice

The large conjugated π bond in the molecular structure of carbon nanotubes (CNTs) interacts with the benzene ring structure in di (n-butyl) phthalates (DBP) through a π - π bond. Compounds of CNTs and DBP form easily, becoming another environmental pollutant of concern. We explore whether CNTs entering animals slow down the degradation of the DBP adsorbed in the CNT cavity, thereby prolonging the "hormonal activity" of DBP. In our study, male BALb/c mice were used as experimental subjects divided into four groups: the control group; the multi-walled carbon nanotubes (MWCNTs) exposure group (10mg/kg/d); the DBP exposure group (2.15 mg/kg/d); and the compound exposure group (MWCNTs + DBP). After 30 days of exposure, the mice were sacrificed and their spleens used for immunotoxicology study. The results showed that the exposure groups exhibited splenomegaly and suffered severe oxidative damage to the spleen. In the compound exposure group: levels of IgA and IgG in the serum of the mice changed, and were significantly different from levels in both the MWCNTs and DBP exposure groups (p <0.05); the pathological sections of the spleen showed that the boundary between the white pulp area (WP) and the red pulp area (RP) was blurred, that the cell arrangement was loose, and that more red blood cells were retained in the spleen. Proteomics mass spectrometry analysis showed that compared with the control group, 70 proteins were up-regulated and 27 proteins were down-regulated in the MWCNTs group, 36 proteins were up-regulated and 23 proteins were down-regulated in the DBP group, 87 proteins were up-regulated and 21 proteins were down-regulated in the compound exposure group. The results of GO enrichment analysis and KEGG enrichment analysis of the differentially expressed proteins showed that the compound exposure harmed the spleen antigen recognition, processing, and presentation, inhibited the activation and proliferation of B cells and T cells, and hindered the adaptive immune responses. Our results showed that MWCNTs and DBP compounds can damage the spleen, and impair the innate and adaptive immune functions of the body.

Molecular detection, histopathological analysis, and immunohistochemical characterization of equine infectious anemia virus in naturally infected equids.

Equine infectious anemia (EIA), a disease caused by equine infectious anemia virus (EIAV), is considered an obstacle to the development of the horse industry. There is no treatment or vaccine available for EIA, and its pathogenesis, as well as the immune response against the virus, is not fully understood. Therefore, an immunohistochemistry assay was developed for the detection of viral antigens in tissues of equids naturally infected with EIAV. Sections of organs of six equids from Apodi-RN, Brazil, that tested positive for EIA by serological tests (ELISA and AGID) were fixed in 10% formalin solution and embedded in paraffin. Immunohistochemistry was performed using a polyclonal anti-EIAV antibody. EIAV antigens were observed in red spleen pulp cells and hepatic sinusoids, as well as bronchiolar and alveolar epithelial cells of the lungs and proximal and distal tubules of the kidneys. The presence of EIAV in the spleen and liver was expected due to viral tropism by macrophages, which are abundantly present in these organs. However, EIAV was also found in lung and kidney epithelial cells, indicating that the virus infects cell types other than macrophages. In conclusion, the immunohistochemical assay standardized in this study was able to detect EIAV antigens in spleen, liver, kidney and lung cells from naturally infected EIAV equids. Immunostaining observed in the spleen confirms viral tropism by mononuclear phagocytes; however, the presence of EIAV in lung and kidney epithelial cells indicates that virus may be eliminated in urine and/or oronasal secretions, suggesting new routes for viral excretion.

Antigen-antibody Expression of Aeromonas hydrophilla on Spleen, Liver, and Kidney of Rabbit

Aeromonas hydrophila is abundant in freshwater environments, especially with high organic matter content. This bacterial infection is opportunistic, which is an infection that usually does not cause disease in animals with normal immune systems, but can attack animals with poor immune systems. Aeromonas hydrophila infection can be recognized for their external wounds (ulcers), mucus dries up, there are patches of bleeding in a latero-ventral region of the body and fins and scales chipped. Research on Outer Membrane Protein (OMP) has been studied in an attempt to obtain a reliable antigen both for diagnosis and for vaccines. In this study, the authors wanted to do research on the reactivity of the Outer Membrane Protein (OMP) Aeromonas hydrophila in New Zealand rabbits with Immunohistochemistry techniques to investigate the interaction of antibodies with antigens in spleen, liver, and kidney of New Zealand rabbits microscopically. The results will be obtained in this study in the form of spleen, liver, and kidney histopathology tissue images that showed the bond between antigens with antibodies with immunohistochemical techniques that visualized with a brownish color.

Experimental Inoculation of Egyptian Rousette Bats (Rousettus aegyptiacus) with Viruses of the Ebolavirus and Marburgvirus Genera.

The Egyptian rousette bat (Rousettus aegyptiacus) is a natural reservoir for marburgviruses and a consistent source of virus spillover to humans. Cumulative evidence suggests various bat species may also transmit ebolaviruses. We investigated the susceptibility of Egyptian rousettes to each of the five known ebolaviruses (Sudan, Ebola, Bundibugyo, Taï Forest, and Reston), and compared findings with Marburg virus. In a pilot study, groups of four juvenile bats were inoculated with one of the ebolaviruses or Marburg virus. In ebolavirus groups, viral RNA tissue distribution was limited, and no bat became viremic. Sudan viral RNA was slightly more widespread, spurring a second, 15-day Sudan virus serial euthanasia study. Low levels of Sudan viral RNA disseminated to multiple tissues at early time points, but there was no viremia or shedding. In contrast, Marburg virus RNA was widely disseminated, with viremia, oral and rectal shedding, and antigen in spleen and liver. This is the first experimental infection study comparing tissue tropism, viral shedding, and clinical and pathologic effects of six different filoviruses in the Egyptian rousette, a known marburgvirus reservoir. Our results suggest Egyptian rousettes are unlikely sources for ebolaviruses in nature, and support a possible single filovirus—single reservoir host relationship.

Expression and function of costimulatory molecules of spleen antigen presenting cells during pregnancy in mice

Expression and function of costimulatory molecules of spleen antigen presenting cells during pregnancy in mice

A novel Ly6C/Ly6G‐based strategy to analyze the mouse splenic myeloid compartment

Currently, there is no standardized panel for immunophenotyping myeloid cells in mouse spleen using flow cytometry. Markers such as CD11b, CD11c, F4/80, Gr-1, Ly6C, and Ly6G have long been used to identify various splenic cell myeloid populations. Flow cytometry and fluorescence-activated cell sorting (FACS) analysis demonstrated that Ly6G/Ly6C markers are superior to Gr-1 for identifying splenic neutrophils, eosinophils, and subsets of monocytes/macrophages. Moreover, these experiments showed that F4/80 is not required for identifying these myeloid subsets and that many of the commercially available preparations of anti-F4/80 antibodies stain poorly for this antigen in spleen. Taken together, we have now developed an informative flow cytometry panel that can be combined with other cell markers to further delineate subpopulations of mouse splenic myeloid cells. This panel will be highly useful to investigators in the flow cytometry field, as there is a critical need to standardize the analysis of myeloid cell subsets.

Expression of chemokine receptor CXCR3 on T cells affects the balance between effector and memory CD8 T-cell generation

Generation of a robust immunological memory response is essential for protection on subsequent encounters with the same pathogen. The magnitude and quality of the memory CD8 T-cell population are shaped and influenced by the strength and duration of the initial antigenic stimulus as well as by inflammatory cytokines. Although chemokine receptors have been established to play a role in recruitment of effector CD8 T cells to sites of inflammation, their contribution to determination of T-cell fate and shaping of the long-lived memory T-cell population is not fully understood. Here, we investigated whether reduced access to antigen and inflammation through alterations in expression of inflammatory and homeostatic chemokine receptors has an impact on generation of effector and memory CD8 T cells. We found that in mice infected with lymphocytic choriomeningitis virus, colocalization of virus-specific CD8 T cells with antigen in spleen is dependent on expression of the inflammatory chemokine receptor, CXCR3. In addition, absence of CXCR3 expression on CD8 T cells leads to formation of fewer short-lived effector cells and more memory precursor cells. Furthermore, the memory CD8 T-cell population derived from CXCR3-deficient cells has fewer cells of the effector memory phenotype and exhibits a recall response of greater magnitude than that of WT cells. These data demonstrate that CD8 T-cell positioning relative to antigen and inflammatory cytokines in secondary lymphoid organs affects the balance of effector and memory T-cell formation and has both a quantitative and qualitative impact on the long-lived memory CD8 T-cell population.

Long-term persistence after acute Q fever of non-infective Coxiella burnetii cell components, including antigens

Previous studies of inciting factors for a prolonged post-infection fatigue syndrome after Q fever (variously termed QFS or Q fever associated CFS/ME in the literature) showed that after the acute infection a high proportion of asymptomatic and QFS patients had Q fever antibody and also low levels in PBMC and bone marrow of Coxiella burnetii (C.b.) DNA with PCR assays directed against three different target sequences in different parts of the coxiella genome. Attempts to isolate a strain of C.b. in A/J mice, and cell culture from PCR positive PBMC and bone marrow were consistently negative. The detailed composition of the persisting coxiella residues remains to be defined. To retest and provide detailed results on selected PCR positive samples from the Birmingham Q fever outbreak patients tested by a highly sensitive method to detect viable organisms and to determine the nature of the residual coxiella cell components. Laboratory case study. NOD/SCID mice were inoculated with samples from the 1989 Q fever outbreak in Birmingham and followed for evidence of infection and the presence of coxiella DNA and specific antigens in spleen and liver macrophages. A significant, unexpected finding of specific antigen was followed by assessment of its ability to provoke production of inflammatory and non-inflammatory cytokines in mice, in THP-1 human macrophage cell cultures and to induce inflammatory lesions in the skin of guinea pigs hyperimmunized against Q fever vaccine. Culture of samples from 10 Birmingham Q fever patients in NOD/SCID mice, 12 years from infection did not yield viable Coxiella burnetii, as shown earlier. However complexes of material with coxiella antigens were found in mouse spleens in all cases but in significantly greater amounts in samples from those with post Q fever fatigue syndrome. The antigenic complexes [now designated 'immunomodulatory complexes' (IMC)] were shown to stimulate cytokine release in the mice and in the THP-1 macrophages and to provoke an inflammatory reaction on intradermal injection into the skin of Q fever hyperimmunized guinea pigs. The study identifies a non-infective complex of C.b. antigens able to survive in the host and provoke aberrant humoral and cell medicated immunity responses - a possible pathogenic link between initial infection and a subsequent long-term post Q fever fatigue syndrome.

Effects of the timing of the administration of Mycoplasma hyopneumoniae bacterin on the development of lesions associated with porcine circovirus type 2

To determine whether there is an effect of the timing of vaccination on porcine circovirus type 2 (PCV-2) replication and PCV-2-associated lesions, 78 pigs were randomly assigned to eight groups:...

IL-1 gene expression in human mammary tumour xenografts after treatment with hexadecylphosphocholine.

Hexadecylphosphocholine (HPC), an alkylphosphocholine, is active against experimental and clinical breast cancer in viw but the precise mechanisms involved in its anti-tumour activity are not fblly understood. In vitro studies have revealed remarkable anti-tumour activity against HL60, U937, Raji and K562 cell lines [l], three human mammary carcinomas cell lines, MT-1, MT-3, MaTu and a murine colon carcinoma MAC 16 [2]. HPC also induced apoptosis in KB cells in vitro [3]. In vivo studies with human mammary carcinomas in nude mice showed tumour volume was reduced following treatment with HPC compared with classic anti-tumour drugs such as doxorubicin, mitoxantrone, methotrexate and 5-fluorourad [4]. Topical application to recurrent breast cancer in the skin has resulted in a 30?? overall response rate [S]. In addition, HPC had outstanding anti-tumour activity in dimethylbenzanthe (DMBA) induced rat mammary tumours, however, another autochthonus tumour, the benzo (a) pyrene-induced sarcoma of the rat did not respond to HPC treatment 161. HPC has been shown previously to have effects on the immune system in vitro such as amplifying the efFect of granulocyte colony-stimulating factor on haematopoietic cells [7] and in liposomal form, increasing the production of TNFa [S]. Increases in leucocyte and platelet counts in patients after administration of HPC have also been observed [9]. Preliminary studies in this laboratory have shown increased expression of CD3 antigen in spleens [lo] and morphological changes in secondary immune tissues [ 111 and tumours [ 121 of MT-I tumour bearing nude mice after treatment with HPC. As yet, however, there is no clear understanding of how this drug recruits cells of the immune system or if immunological modifications lead to anti-tumour effects. The aim of this study was to investigate the anti-tumour mechanisms of HFT against MT1 breast cancer xenografts growing in nude mice and in particular the role of the immune system including cytokine production in the regression of tumours. MT-I tumours were transplanted into the mammary fat pads of twenty four female twelve week old NCWnude mice (weight range 25-30g) subcutaneously by means of a trocar. Tumours were allowed to grow until they were large enough to be measured accurately by callipers (approximately 22 days). Eight of these mice were then used for treatment with HPC, 8 mice were treated with solvent, 4 mice were treated with cyclophosphamide and 4 were kept as untreated controls. HPC was solubilized in 1 O?? Tween 80/ saline and administered orally once a day for 5 days to MT-1 tumour-bearing nude mice at a daily dose of 5Omg/kg. Both untreated and solvent treated controls were included. Cyclophosphamide was solubilized in saline and administered as a single I.P. dose (25Omg/kg). One week after the end of drug administration, the mice were killed and the tumours removed for histology, immunostaining and RNA extraction. Mice treated with cyclophosphamide were sacrificed when the tumours started to regress. Control mice were also sacrificed at the same time and the tumours removed for similar evaluation. Endothelial cells, macrophages (Mcp) and lymphocytes were detected with antibodies to CD31, pan Mcp marker, CD3, CD4, CDS and CD45wB220 respectively. To investigate the production of cytokines, the expression of IL-l was assessed by RT-PCR. HPC treated tumours showed large areas of lysis and the presence of giant cells. Immunostaining revealed increases in endothelial cells associated with massive infiltration of Mcp, T cells (Th and Tc) and B cells. Immune cell infiltration was not observed in tumours following cyclophosphamide treatment or control tumours. In hrther experiments to investigate cytokine gene expression, IL-l mRNA was detected in HPC treated tumours but not in cyclophosphamide treated or control tumours using RT-PCR (Fig. 1). 1 2 3 4 5 6

Modulation of primary antibody response by protein A in tumor bearing mice.

Protein A (PA) is a cell wall glycoprotein of Staphylococcus aureus Cowan I, which possess a number of immunomodulatory and antitumor properties. We have previously shown that PA suppresses the anti-sheep erythrocyte primary antibody response in normal mice. The present investigation evaluates the effect of protein A on the anti-sheep erythrocyte primary antibody response in tumor-bearing mice. The primary antibody response in tumor-bearing mice immunized with sheep red blood cells (SRBC) was suppressed by the intraperitoneal administration of PA in a dose-dependent fashion. The plaque forming cell (PFC) assay was used to assess this response. Maximum suppression of the PFC response was observed at 12 micrograms PA/animal (p < 0.001) and could be observed at doses as low as 1 microgram PA/animal (p < 0.01). The amount of suppression was proportional to the number of PA doses administered. In addition this effect was critically dependent on the timing of PA administration. PA showed no significant effect on PFC when injected after immunization, but it produced pronounced suppression when injected prior to the immunization with SRBC. Maximum suppression of the PFC response was observed when PA was administered one day before the antigen challenge. PA also reduced splenic localization of 51Cr labeled SRBC to 42% (p < 0.01). The altered localization of antigen in spleen may be responsible for reduced PFC response in tumor-bearing mice. Depletion of B-lymphocyte is reported to exhibit tumor inhibition. Therefore, we propose that the suppression of the primary antibody response by PA helps in tumor regression by reducing the soluble immunosuppressive immune complexes.

In vitroinfection of mononuclear cells derived from various chicken lymphoid tissues by chicken anaemia virus

Mononuclear cell suspensions derived from spleen, thymus and bone marrow tissues from chickens at 6 and 28 days of age were infected with CAV under various culture conditions. Indirect immunofluorescent staining of cytospin preparations of mononuclear cells revealed greater numbers of cells containing CAV antigens in spleen and bone marrow cultures than in thymus cultured under the same conditions. Cell cultures derived from 6- and 28-day-old chickens were equally susceptible to CAV infection. These results indicate that the age resistance to disease experimentally induced by CAV is not due to disappearance or increased resistance of a target cell. Infectivity titrations demonstrated that mononuclear cell cultures supported CAV replication. However, the virus titres obtained were lower than those detected in CAV infected MDCC-MSB1 cultures.

Stimulation of mature unprimed CD8+ T cells by semiprofessional antigen-presenting cells in vivo.

To test whether unprimed CD8+ cells can recognize class I alloantigens presented selectively on non-bone marrow (BM)-derived cells, unprimed parental strain CD8+ cells were transferred to long-term parent-->F1 BM chimeras prepared with supralethal irradiation. Host class I expression in the chimeras was undetectable on BM-derived cells and, in spleen, was limited to low-level staining of vascular endothelium and moderate staining of follicular dendritic cells (a population of nonhemopoietic cells in germinal centers). Despite this restricted expression of antigen, acute blood-to-lymph recirculation of parental strain T cells through the chimeras led to selective trapping of 95% of CD8+ cells reactive to normal F1 spleen antigen presenting cells (APC) in vitro. Subsequently, a small proportion of the trapped cells entered cell division and gave rise to effector cells expressing strong host-specific CTL activity. The activation of host-specific CD8+ cells was also prominent in double-irradiated chimeras, and cell separation studies showed that the effector cells were generated from resting precursor cells rather than from memory-phenotype cells. It is suggested that the non-BM-derived cells in the chimeras acted as semiprofessional APC. These cells were nonimmunogenic for most host-reactive CD8+ cells but were capable of stimulating a small subset of high-affinity T cells. The possible relevance of the data to the prolonged immunogenicity of vascularized allografts in humans is discussed.

Selective inability of spleen antigen presenting cells from Leishmania donovani infected hamsters to mediate specific T cell proliferation to parasite antigens.

Golden hamsters (Mesocricetus auratus) infected with Leishmania donovani develop a disease similar to human kala-azar. There is conspicuous hypergammaglobulinaemia and their T cells do not respond to stimulation by parasite antigens. The impairment of the cellular immune response seems to be restricted to parasite antigens since infected animals are able to develop a T cell response to the mitogen Concanavalin A (Con-A) and, after sensitization, to the antigens keyhole limpet haemocyanin (KLH) and human serum albumin (DNP-HSA). In the present investigations we studied the role played by infected macrophages in the development of the cellular unresponsiveness present in visceral leishmaniasis. Adherent spleen cells from infected hamsters were unable to present L. donovani antigens to antigen specific T cells, however they were able to present KLH. Conversely, T cells from infected animals did not respond to parasite antigens even when these antigens were presented by normal syngeneic macrophages. Interestingly, lymphocytes from inguinal lymph nodes of infected animals sensitized in their foot pad with parasite antigens proliferated well when stimulated in vitro with L. donovani antigens. These results suggest that the defect in the cellular immune response of the L. donovani infected hamsters is a consequence of a selective inability of their antigen presenting cells to process and present parasite antigens to T cells.

Peripheral tolerance induced in lymph nodes by syngenic spleen cells inhibits generation of CTLs to hapten-altered self antigens but not to alloantigens

The immunological tolerance that is induced in lymph nodes that have been exposed to syngeneic spleen cells has been examined. Development of cytotoxic T lymphocytes was used to assess the immunological status of the lymph node cells. The tolerance was studied from the viewpoint of its induction, its activation, and its specificity. We had already reported that injecting either T or B cells of splenic origin into a regional lymph node environment a week prior to immunization for CTL to hapten-altered self antigens prevents development of the CTL. Here, we confirm that syngeneic splenic cells but not lymph node cells will induce the suppression provided that spleen cells are not coupled with hapten. We now report that splenic cells that cannot replicate or synthesize and secrete protein are capable of inducing the suppression. The data suggest a preformed surface marker peculiar to spleen cells and perhaps on cells that traverse the thymus induces local tolerance that is mediated by suppressor cells. Triggering the induced suppressor T cells (previously identified as CD8 +) was achieved by syngeneic spleen cells as well as by H-2-compatible, Mls-disparate spleen cells but not by syngeneic lymph node cells or apparently by allogeneic spleen cells. Furthermore, triggering suppression was achieved by hapten-coupled syngeneic spleen cells whereas such cells would not induce the suppression. Thus, activating the suppressor cells requires reexposure to splenic cells of the proper MHC haplotype, unaltered or coupled with either TNP or FITC. Once triggered, the suppression was manifested toward CTL generation against hapten-coupled syngeneic antigens on either spleen or lymph node cells but not against allogeneic antigens. Thus, the specificity of the tolerance was directed to altered self antigens despite its induction by unaltered spleen antigen. Furthermore, for suppression to be seen the spleen antigen was not required to be on the hapten-coupled syngeneic cells used for the CTL immunization. The relationship of the splenic cell “antigen” to hapten-altered self antigens and to other surface markers and its site of acquisition within the body and its significance for cell homing have become intriguing questions of importance. This information has been discussed from the viewpoint of its applicability to autoimmune diseases as well as to cessation of inflammatory reactions that may be mediated by lymph node cells.

Elimination of Spleen and of Lymph Node Macrophages and Its Difference in the Effect on the Immune Response to Particulate Antigens

To study the role of macrophages in the in situ immune response to particulate antigens in spleen and popliteal lymph nodes (PLN), mice were injected with dichloromethylene diphosphonate (C1 2MDP)-containing liposomes to eliminate macrophages, followed by immunization with trinitrophenylated sheep red blood cells (TNP-SRBC). Depletion of macrophages in the spleen caused a strong decrease in the number of antibodyforming cells (AFC), which develop after intravenous (i.v.) injection of the antigen. These results strongly suggested the involvement of splenic macrophages in the processing of TNPSRBC. In particular, the populations of marginal zone macrophages may be involved in the inductive phase of an antibody response to particulate antigens. These macrophages are strategically positioned at the end of the white pulp capillaries in the marginal zone of the spleen and they have their cell processes between the marginal zone-B cells. Elimination of macrophages in PLN had no effect on the number of AFC, which develop after subcutaneous (s.c.) injection of the antigen in the hind footpads. This indicates that the macrophages are not essential for the induction of a local immune response to the particulate antigen TNP-SRBC. After depletion of lymph node macrophages, the number of AFC developing in the spleen after s.c. footpad injection of the antigen increased and the anti-TNP serum titers were elevated. This may well be caused by the fact that more of the antigen reaches the circulation and subsequently stimulates the spleen.

Efficacy of Avirulent Hemorrhagic Enteritis Virus Propagated in Turkey Leukocyte Cultures for Vaccination against Hemorrhagic Enteritis in Turkeys

Avirulent hemorrhagic enteritis virus (HEV-A) propagated in turkey leukocyte cell culture was tested as a vaccine to prevent hemorrhagic enteritis (HE) in turkeys in experimental and field trials. Immunization of turkeys with live HEV-A resulted in protection against a challenge with virulent HEV (HEV-V) as measured by the serological response and the absence of clinical disease and HEV antigen in spleens. In field trials, 19 out of 20 flocks seroconverted within 21 days after vaccination with live HEV-A distributed in the drinking water. The average immune response of the turkeys in these flocks was 96%. Most importantly, neither clinical HE nor other adverse effects caused by HEV-A vaccination were observed in any of the vaccinated flocks. Because maternal antibodies can interfere with the immune response to the vaccine, the optimum time for vaccination was determined. Using an established half-life value of 4.25 days for turkey antibody, and knowing the enzyme-linked immunosorbent assay titer of the maternal antibodies and age of the turkey, the time of vaccination could be calculated taking into account that maternal antibody titers should be lower than 40 to vaccinate the turkeys successfully and induce protection. In vivo tests with HEV-A preparations confirmed the replication of the virus in turkey leukocyte cultures and the potential to pass it in culture. Furthermore, in vivo analysis showed that most infectious virus was associated with preparations of the nonadherent cell population, confirming the results obtained by in vitro analysis. The potency of HEV-A preparations was dependent on the production method and varied from an average of 570 to 8135 doses per ml.

Big liver and spleen disease of broiler breeders

Five adult broiler breeders were inoculated with faeces and tissue extracts from birds with big liver and spleen (BLS) disease. Five birds were placed in contact with the inoculated birds. After 8 weeks all inoculated and four of the five in-contact birds were shown to be infected as evidenced by the detection of an immune response and/or the demonstration of BLS antigen in spleen and tissue smears, by an immunofluorescence test and by agar gel immunodiffusion. Using appropriate antisera BLS antigen was found mainly in phagocytic liver cells and in splenic macrophages and dendritic cells. Fewer cells containing antigen were found in the kidney. Double staining of liver and spleen tissue for BLS antigen and chicken immunoglobulin indicated that many cells were positive for both. It is possible that BLS antigen in most cells may represent phagocytosed material rather than a replicating agent. If so, while this could explain the failure to detect virus-like particles, it implies that the primary site of replication of the BLS agent and its nature remain to be established.

Hemorrhagic Enteritis of Turkeys: Influence of Maternal Antibody and Age at Exposure

The effect of maternal antibody (MAB) to hemorrhagic enteritis (HE) on the response of turkeys to infection with virulent and avirulent strains of HE virus (HEV) was examined. The influence of age at exposure and treatment with HEV antibody on development of clinical HE also was studied. MAB protected poults from clinical HE for up to 6 weeks of age. MAB also interfered with vaccination against the disease for at least 5 weeks after hatching, as indicated by absence of HEV antigen in spleens and by poor seroconversion at 6 days and at 3 weeks post-vaccination, respectively. The incidence of clinical HE in MAB-negative poults was significantly higher in poults inoculated with virus at 15 days of age or older than in poults inoculated at 1-13 days of age. Further, MAB-negative poults embryonally inoculated with virulent or avirulent strains of HEV did not develop disease; these poults developed antibody and resisted challenge with virulent virus at 6 weeks of age. Poults treated with HE antibody within 1 hour of challenge or at 1, 3, or 5 weeks before challenge with virulent virus were protected against lesions and mortality induced by HEV. These results suggest that MAB may influence susceptibility of turkeys to infection with HEV for at least 5 to 6 weeks after hatching, unlike the case with most other viral infections of poultry. The results confirm that early age resistance to clinical HE is independent of MAB and suggest that such resistance persists for up to 13 days of age. The data also suggest that turkeys lacking MAB can be immunized against HE by embryo vaccination.