Integrated histopathological and urinary metabonomic investigation of the pathogenesis of microcystin-LR toxicosis.

Patterns of change of endogenous metabolites may closely reflect systemic and organ-specific toxic changes. The authors examined the metabolic effects of the cyanobacterial (blue-green algal) toxin microcystin-LR by (1)H-nuclear magnetic resonance (NMR) analysis of urinary endogenous metabolites. Rats were treated with a single sublethal dose, either 20 or 80 µg/kg intraperitoneally, and sacrificed at 2 or 7 days post dosing. Changes in the high-dose, 2-day sacrifice group included centrilobular hepatic necrosis and congestion, accompanied in some animals by regeneration and neovascularization. By 7 days, animals had recovered, the necrotizing process had ended, and the centrilobular areas had been replaced by regenerative, usually hypertrophic hepatocytes. There was considerable interanimal variation in the histologic process and severity, which correlated with the changes in patterns of endogenous metabolites in the urine, thus providing additional validation of the biomarker and biochemical changes. Similarity of the shape of the metabolic trajectories suggests that the mechanisms of toxic effects and recovery are similar among the individual animals, albeit that the magnitude and timing are different for the individual animals. Initial decreases in urinary citrate, 2-oxoglutarate, succinate, and hippurate concentrations were accompanied by a temporary increase in betaine and taurine, then creatine from 24 to 48 hours. Further changes were an increase in guanidinoacetate, dimethylglycine, urocanic acid, and bile acids. As a tool, urine can be repeatedly and noninvasively sampled and metabonomics utilized to study the onset and recovery after toxicity, thus identifying time points of maximal effect. This can help to employ histopathological examination in a guided and effective fashion.

Activation of BLV transcription by NF-kappa B and Tax.

Bovine leukemia virus (BLV) is the causative agent of bovine leukosis, a naturally occurring fatal disease in cattle. BLV transcription is regulated by cellular transcription factors and the virally encoded oncoprotein Tax. In this report, we investigated the functional role of the putative NF-kappa B binding site recently identified in the BLV promoter. Our studies indicate that the kappa B binding motif acts as a functional enhancer in the presence of the cellular NF-kappa B proteins. Furthermore, the kappa B site together with a single 21-bp repeat confers strong activation of BLV transcription in the presence the NF-kappa B proteins and Tax. These results suggest that cellular NF-kappa B may be involved in the regulation of BLV transcription and activation of the virus from latency.

Increased ratio of bcl-2/bax expression is associated with bovine leukemia virus-induced leukemogenesis in cattle.

To further investigate the molecular basis underlying the dysregulation of B cell homeostasis associated with bovine leukemia virus disease progression in cattle, bovine bax was cDNA cloned and sequenced. The predicted amino acid sequence of bovine Bax revealed a 192-amino-acid protein having extensive identity with the human (97%), murine (93%), and rat (94%) homologues. Because the ratio of Bcl-2 to Bax is believed to predetermine the susceptibility to a given apoptotic stimulus, the relative expression of the genes encoding these oncoproteins was evaluated in cattle naturally infected with BLV. In BLV-infected cattle an increase in the ratios of bcl-2/bax mRNA and protein expression correlated with advancing stages of disease. These findings suggest that in addition to the maintenance of BLV-associated hematopoietic malignancies, the reciprocal expression of Bcl-2/Bax may modulate the induction of B cell expansion typical of BLV disease progression.

Unintegrated bovine leukemia virus DNA: association with viral expression and disease.

The correlation between bovine leukemia virus (BLV) unintegrated DNA, viral expression, and stage of disease was determined in cattle naturally infected with BLV. The concomitant presence of unintegrated BLV DNA with viral transcriptional activity was observed in 53% (18 of 34) of hematologically normal, BLV-seropositive cattle and in 100% (10 of 10) of BLV-seropositive cattle with the preneoplastic syndrome persistent lymphocytosis. In vitro studies suggested that accumulation of unintegrated BLV DNA resulted from a process of reinfection rather than intracellular reverse transcription of newly synthesized BLV RNA. Interestingly, unintegrated BLV DNA was not detected in tumor cells from cattle with BLV-associated lymphocytic leukemia/malignant lymphoma despite viral transcriptional activity in 100% (eight of eight) of these cattle. Thus, the presence of unintegrated BLV DNA differentiated nonneoplastic from neoplastic conditions in BLV-infected cattle. These results demonstrate that unintegrated viral DNA serves as a marker of disease progression in BLV-infected cattle but is not necessarily associated with induction or maintenance of the neoplastic state.

A deletion in the proximal untranslated pX region of human T-cell leukemia virus type II decreases viral replication but not infectivity in vivo.

The function of untranslated (UT) nucleotide sequences in the proximal portion of the pX region of the human T-cell leukemia virus (HTLV) family of retroviruses remains enigmatic. Previous studies have shown that these sequences are not necessary for the expression of viral proteins or for the induction, transmission, or maintenance of the transformed cell type in vitro. To determine the effect of the UT region in vivo, separate groups of rabbits were inoculated with lethally irradiated, stable clones of the human B-lymphoblastoid cell line, 729, transfected with either a full-length wild-type HTLV-II clone (pH6neo) or a mutant clone containing a 324-bp deletion in the proximal UT portion of pX (pH6neo delta UT[6661-6984]), or nontransfected 729 cells. All rabbits inoculated with either wild-type or pX-deleted HTLV-II developed a similar profile and titer of serum antibodies against HTLV-II antigens, as determined by Western immunoblots, by 4 weeks postinoculation (PI). Antibody titers, as determined by enzyme immunoassay, were similar between the two groups of rabbits and increased over the 18-week period of study. All rabbits were killed at 18 weeks PI, and spleen, peripheral blood lymphocytes (PBMC), bone marrow, and mesenteric lymph node were assayed for HTLV-II tax/rex sequences by quantitative polymerase chain reaction. Virus was detected in all tissues tested from all rabbits inoculated with 729pH6neo cells containing wild-type HTLV-II, which contained between 1.4 and 0.3 mean copies of provirus per cell. In contrast, the distribution and number of provirus copies were more limited in rabbits inoculated with 729pH6neo delta UT(6661-6984) cells containing UT-deleted HTLV-II; in most tissues, there was a fivefold to sevenfold reduction in mean provirus copies per cell as compared with rabbits inoculated with wild-type HTLV-II. All rabbits inoculated with control 729 cells remained negative for HTLV-II infection, as determined by the same techniques. It was concluded that UT sequences in the proximal portion of HTLV-II are not necessary for infection but confer increased replicative capacity in vivo.

Prospective characterization of the clinicopathologic and immunologic features of an immunodeficiency syndrome affecting juvenile llamas.

The clinicopathologic and immunologic features of 15 llamas affected with juvenile llama immunodeficiency syndrome (JLIDS) are described. Healthy adult (n = 10) and juvenile (n = 10) llamas served as controls. JLIDS llamas were characterized by wasting, and clinically apparent, repeated infections were frequently observed. The median age at which a health problem was first perceived was 11.6 months. All 15 affected llamas died or were killed, and JLIDS was confirmed at necropsy. The median duration of illness was 3.5 months. Lymphocyte blastogenesis assays showed suppressed responses (particularly to Staphylococcus sp. Protein A) in JLIDS llamas. No evidence of retroviral infection was detected. Mild, normocytic, normochromic, non-regenerative anemia, low serum albumin concentration and low to low-normal globulin concentrations were typically found on initial clinical evaluation. Lymph node biopsies showed areas of paracortical depletion. All llamas affected with JLIDS had low serum IgG concentrations, pre-vaccination titers against Clostridium perfringens C and D toxoids of < or = 1:100, and no titer increase following vaccination.

Identification of an NF-kappa B binding site in the bovine leukemia virus promoter.

Although the mechanism by which bovine leukemia virus (BLV) induces neoplastic transformation of the host B cells is unknown, it is likely that critical interactions between cellular DNA-binding proteins and the virus are involved. We have used DNase I protection (footprinting) assays to construct a map of protein-DNA interactions on the 5' long terminal repeat of BLV. In addition to the three cyclic AMP response elements previously reported, we have also found an NF-kappa B binding site between -118 and -70 nucleotides upstream of the RNA start site. This site binds several members of the kappa B family of proteins, including p49, p50, and p65, in both footprint and electrophoretic mobility shift assays and functions as an enhancer element when inserted upstream of the chloramphenicol acetyltransferase gene. NF-kappa B may be a critical nuclear binding protein that regulates both viral replication and key cellular genes in BLV-infected B cells.

Retrovirus-like activity in an immunosuppressed dog: pathological and immunological findings.

A putative retrovirus was isolated from a dog with a severe, acquired immunodeficiency-like syndrome. The haematological abnormalities and immunological deficiencies included anaemia, leucopenia (lymphopenia and neutropenia), thrombocytopenia, decreased humoral immunity, and ineffective T-cell responses in-vitro. The necropsy findings included generalized lymphoid depletion, severe bone marrow hypoplasia, plasmacytic infiltrates in lymphoid and non-lymphoid organs, and severe secondary infections. Supernates of peripheral blood mononuclear cell cultures from the affected dog contained an agent with manganese-dependent reverse transcriptase (RT) activity that sedimented at a density of 1.122 g/ml. RT activity was also found post-mortem in extracts prepared from the bone marrow, lymph nodes, and small intestine. The lymph nodes and small intestine expressed a 3.8 kb mRNA that was recognized by a bovine leukaemia virus (BLV) pol DNA probe by Northern blotting. DNA isolated from the lymph nodes and small intestine from the affected dog showed distinct band patterns by Southern analysis, suggesting an exogenous retrovirus. The retrovirus could be propagated in normal canine peripheral blood mononuclear cells or short-term canine lymphocyte cell lines in-vitro, and was cytopathogenic for cells of canine, but not human, origin. These results suggest the existence of a pathogenic canine retrovirus capable of producing disease of the type associated with retroviruses in other species.

Pathogenicity of molecularly cloned bovine leukemia virus.

To delineate the mechanisms of bovine leukemia virus (BLV) pathogenesis, four full-length BLV clones, 1, 8, 9, and 13, derived from the transformed cell line FLK-BLV and a clone construct, pBLV913, were introduced into bovine spleen cells by microinjection. Microinjected cells exhibited cytopathic effects and produced BLV p24 and gp51 antigens and infectious virus. The construct, pBLV913, was selected for infection of two sheep by inoculation of microinjected cells. After 15 months, peripheral blood mononuclear cells from these sheep served as inocula for the transfer of infection to four additional sheep. All six infected sheep seroconverted to BLV and had detectable BLV DNA in peripheral blood mononuclear cells after amplification by polymerase chain reaction. Four of the six sheep developed altered B/T-lymphocyte ratios between 33 and 53 months postinfection. One sheep died of unrelated causes, and one remained hematologically normal. Two of the affected sheep developed B lymphocytosis comparable to that observed in animals inoculated with peripheral blood mononuclear cells from BLV-infected cattle. This expanded B-lymphocyte population was characterized by elevated expression of B-cell surface markers, spontaneous blastogenesis, virus expression in vitro, and increased, polyclonally integrated provirus. One of these two sheep developed lymphocytic leukemia-lymphoma at 57 months postinfection. Leukemic cells had the same phenotype and harbored a single, monoclonally integrated provirus but produced no virus after in vitro cultivation. The range in clinical response to in vivo infection with cloned BLV suggests an important role for host immune response in the progression of virus replication and pathogenesis.

Inhibition of protein kinase C results in decreased expression of bovine leukemia virus.

The in vitro expression of bovine leukemia virus (BLV) in short-term cultured bovine peripheral blood mononuclear cells (PBMC) is associated with increased spontaneous lymphocyte blastogenesis. The purpose of this study was to determine whether intracellular pathways responsible for antigen- or mitogen-induced lymphocyte blastogenesis were also responsible for induction of BLV expression. The protein kinase C (PKC) inhibitor 1-(5-isoquinolinylsulfonyl)-3-methylpiperazine dihydrochloride (3-methyl H7) decreased blastogenesis in a dose-dependent manner, as measured by [3H]thymidine incorporation, in unstimulated, lipopolysaccharide-stimulated and phorbol ester (PMA)-stimulated BLV-infected PBMC. Similarly, 3-methyl H7 decreased BLV expression, as measured by production of gp51 envelope antigen or p24gag antigen, in BLV-infected PBMC under the same conditions. Using an RNase protection assay, the inhibition of BLV expression by 3-methyl H7 was shown to be due to decreased transcriptional activity. The cyclic GMP-dependent protein kinase and cyclic AMP-dependent protein kinase inhibitor N-(2-guanidinoethyl)-5-isoquinolinesulfonamide (HA1004) did not inhibit either BLV expression or blastogenesis of BLV-infected bovine PBMC. Additional evidence for the PKC-dependent expression of BLV was obtained by using a persistently BLV-infected B-lymphocyte cell line, NBC-13. Activation of PKC by PMA in NBC-13 cells increased BLV expression. 3-methyl H7 decreased the PMA-induced expression of BLV in NBC-13 cells in a dose-dependent manner, whereas HA1004 did not inhibit this expression. These results identify a mechanism for the induction of BLV expression through PKC activation and therefore indicate that latency and replication of BLV is controlled by normal B-lymphocyte intracellular signaling pathways.

Seroprevalence of bovine immunodeficiency-like virus and bovine leukemia virus in a dairy cattle herd.

To determine the prevalence of single vs. dual infection with bovine immunodeficiency virus (BIV) and bovine leukemia virus (BLV), sera (n = 95) from a dairy cattle herd were analyzed for anti-BIV and anti-BLV antibodies by an enzyme linked immunosorbent assay. Twenty-one percent (20/95) of samples were BIV-seropositive, while 52% (49/95) of the same samples were BLV-seropositive. A significantly greater percentage of BIV-seronegative samples were BLV-seropositive, 57% (43/75), than were BIV-seropositive samples, 30% (6/20). There was no significant correlation between data ranked from least to greatest amount of anti-viral antibody. Five cattle had persistent lymphocytosis (PL); all five were BLV-seropositive and two were BIV-positive. The mean anti-BLV titer was significantly greater in PL cattle, as compared at non-PL cattle, whereas there was no significant difference between the mean anti-BIV titer in PL cattle, as compared with non-PL cattle. These results provide additional information on the seroprevalence of naturally occurring BIV infection, and indicate that BIV can exist independent of other common infectious agents, such as BLV. Further, the results suggest that infection with BIV is not associated with an increased rate of infection with other infectious agents such as BLV.

Development of a monoclonal antibody-based p24 capsid antigen detection assay for HTLV-I, HTLV-II, and STLV-I infection.

A monoclonal antibody-based antigen capture enzyme-linked immunosorbent assay (ELISA) was developed and employed to detect p24 capsid antigen from human T-cell lymphotropic viruses type I and II (HTLV-I, HTLV-II), simian T-cell lymphotropic virus type I (STLV-I)-infected cell lines, and from mononuclear cell cocultures of HTLV-infected humans and STLV-I infected monkeys. A monoclonal antibody specific for HTLV p24 and p53 capsid antigens was coated onto 96-well microtiter plates to capture HTLV/STLV antigen. Captured antigen was then detected by the addition of a polyclonal, biotinylated human anti-HTLV-I antibody, and color developed with tetramethyl benzidine/H2O2 substrate. As little as 15 pg/ml of HTLV-I p24 antigen could be detected in this assay. Culture supernatants from HTLV-I-infected cell lines (HUT-102, MT-2, C5/MJ, HTLV-II-infected cell lines (Mo-T, Mo-B, PanG 12.1, NRA) and STLV-I-infected cell lines (Matsu, NEPC M39) were all positive in the assay. In addition, p24 was detected from peripheral blood mononuclear cell (PBMC) cocultures of 8 of 8 (100%) HTLV-I diseased patients, 14 of 20 (70%) HTLV-I and HTLV-II-infected, asymptomatic persons, and 8 of 8 (100%) STLV-I-infected, asymptomatic monkeys. Culture supernatants of cells infected with human immunodeficiency virus type (HIV-1), simian immunodeficiency virus (SIV), Chlamydia trachomatis, cytomegalovirus (CMV), herpes simplex I and II (HSV), feline leukemia virus (FELV), bovine leukemia virus (BLV), and bovine immunodeficiency virus (BIV) were all negative. Similarly, normal human peripheral blood mononuclear cells and uninfected, transformed human T cells, were also negative in the assay.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparative biological responses of rabbits infected with human T-lymphotropic virus type I isolates from patients with lymphoproliferative and neurodegenerative disease.

An experimental rabbit model was used to determine host responses to infection by various human T-lymphotropic virus type-I (HTLV-I) strains. Seven groups of 4 to 5 rabbits each were inoculated with lethally-irradiated HTLV-I-infected cell lines derived from patients with adult T-cell leukemia/lymphoma or from patients with HTLV-I-associated myelopathy. Four separate control groups of 2 rabbits each were inoculated with similarly prepared HTLV-I-negative cells derived from rabbits or humans. Anti-viral antibody responses were assessed by immunoblot assay and hematologic parameters were measured using automated cell counters and cytologic staining. The virologic status of challenged rabbits was determined by co-culture and HTLV-I antigen capture assay, as well as by polymerase chain reaction (PCR) amplification of HTLV-I DNA from peripheral blood mononuclear cells (PBMC) or tissues. The HTLV-I inocula could be separated into groups based upon their infectivity to rabbits: highly infectious strains elicited intense serologic responses and were detected frequently in tissues by antigen and PCR assays, while other strains were moderately to poorly infectious, induced weak antibody responses and were infrequently detected by antigen and PCR assays. Overall, PBMC appeared to have the greatest quantity of HTLV-I containing cells, while bone marrow was a poor source of virus. No clinical or hematologic abnormalities were evident during the 24-week course of infection. Taken together, our results suggest there is heterogeneity in the biological response to HTLV-I infection which is, in part, dependent on the infecting strain of virus.