Caracterização epidemiológica e fatores de risco associados à infecção por lentivírus de pequenos ruminantes na região do semiárido paraibano, Nordeste do Brasil / Epidemiological characterization and risk factors associated with lentivirus infection in small ruminants in the semiarid of Paraíba State, Northeastern Brazil

O objetivo deste estudo foi determinar a soroprevalência de lentivírus de pequenos ruminantes (LVPR) e identificar os fatores de risco para a ocorrência de caprinos e ovinos soropositivos no semiárido do Estado da Paraíba. Foram utilizados 1.733 animais, sendo 1.274 caprinos procedentes de 62 Unidades de Produção (UPs) e 459 ovinos provenientes de 32 UPs. Para o diagnóstico sorológico da infecção por lentivírus foi utilizado o teste de imunodifusão em gel de ágar (IDGA). Dos 1.274 caprinos analisados 15 (1,18%) foram soropositivos, enquanto que todos os 459 ovinos foram soronegativos. Das 62 propriedades caprinas analisadas oito (12,9%) apresentaram pelo menos um animal soropositivo. Os fatores de risco para a ocorrência de caprinos soropositivos foram área da propriedade (odds ratio = 3,28; p = 0,044), ausência de capacitação dos produtores (odds ratio = 8,29; p = 0,042) e uso de monta natural não controlada (odds ratio = 6,78; p = 0,012). Conclui-se que a infecção por lentivírus de pequenos ruminantes, demonstrada pela detecção de anticorpos, está disseminada em rebanhos caprinos do semiá­rido paraibano, e sugere-se o incentivo à capacitação contínua dos produtores, manutenção de reprodutores negativos ao LVPR e utilização de inseminação artificial com o intuito de evitar o contato físico entre macho e fêmeas.(AU)

The aim of this survey was to determine the seroprevalence of small ruminant lentivirus (SRLV) and to identify risk factors for the occurrence of seropositive goats and sheep in the semiarid region of Paraiba State. It were used 1,733 animals, being 1,274 goats from 62 Production Units (PU) and 459 sheep from 38 PU. For the serological diagnosis of lentivirus infection the agar gel immunodiffusion test (AGID) was used. Of the 1,274 goats 15 (1.18%) were seropositive, and all 459 sheep were seronegative. Of the 62 goat herds eight (12.9%) presented at least one seropositive animal. Risk factors for the occurrence of seropositive goats were area of the property ≤35 ha (odds ratio = 3.28; p=0.044), not training of producers (odds ratio = 8.29; p=0.042) and use of uncontrolled natural mating (odds ratio = 6.78; p=0.012). It is concluded that lentivirus infection detected by serology is spread in goat flocks in the semiarid of the State of Paraíba, and it is suggested to encourage the continous capacitation of owners, maintenance of reproducers negative for SRLV and use of artificial insemination aiming to avoid the physical contact among male and females.(AU)

Comparison of risk factors for seropositivity to feline immunodeficiency virus and feline leukemia virus among cats: a case-case study.

BACKGROUND: Feline immunodeficiency virus (FIV) and feline leukemia virus (FeLV) are reported to have similar risk factors and similar recommendations apply to manage infected cats. However, some contrasting evidence exists in the literature with regard to commonly reported risk factors. In this study, we investigated whether the known risk factors for FIV and FeLV infections have a stronger effect for either infection. This retrospective study included samples from 696 cats seropositive for FIV and 593 cats seropositive for FeLV from the United States and Canada. Data were collected during two cross sectional studies, where cats were tested using IDEXX FIV/FeLV ELISA kits. To compare the effect of known risk factors for FIV infection compared to FeLV, using a case-case study design, random intercept logistic regression models were fit including cats' age, sex, neuter status, outdoor exposure, health status and type of testing facility as independent variables. A random intercept for testing facility was included to account for clustering expected in testing practices at the individual clinics and shelters. RESULTS: In the multivariable random intercept model, the odds of FIV compared to FeLV positive ELISA results were greater for adults (OR = 2.09, CI: 1.50-2.92), intact males (OR = 3.14, CI: 1.85-3.76), neutered males (OR = 2.68, CI: 1.44- 3.14), cats with outdoor access (OR = 2.58, CI: 1.85-3.76) and lower for cats with clinical illness (OR = 0.60, 95% CI: 0.52-0.90). The variance components obtained from the model indicated clustering at the testing facility level. CONCLUSIONS: Risk factors that have a greater effect on FIV seropositivity include adulthood, being male (neutered or not) and having access to outdoors, while clinical illness was a stronger predictor for FeLV seropositivity. Further studies are warranted to assess the implications of these results for the management and control of these infections.

Influence of proinflammatory cytokines and chemokines on the neuropathogenesis of oncornavirus and immunosuppressive lentivirus infections.

Retroviral infection of the CNS can lead to severe debilitating neurological diseases in humans and other animals. Four general types of pathogenic effects with various retroviruses have been observed including: hemorrhage (TR1.3), spongiform encephalopathy (CasBrE, FrCasE, PVC211, NT40, Mol-ts1), demyelination with inflammatory lesions (HTLV-1, visna, CAEV), and encephalopathy with gliosis and proinflammatory chemokines and cytokines, usually with microglial giant cells and nodules [human immunodeficiencyvirus (HIV), feline immunodeficiencyvirus (FIV), simian immunodeficiency virus (SIV), Fr98]. This review focuses on this fourth group of retroviruses. In this latter group, proinflammatory cytokine and chemokine upregulation accompanies the disease process, and may influence pathogenesis by direct effects on resident CNS cells. The review first discusses the Fr98 murine polytropic virus system with particular reference to the roles of cytokines and chemokines in the pathogenic process. The Fr98 data are then compared and contrasted to the cytokine and chemokine data in the lentivirus systems, HIV, SIV, and FIV. Finally, various mechanisms are presented by which tumor necrosis factor (TNF) and several chemokines may alter the pathogenesis of retrovirus infection of the CNS.

Characterization and role of lentivirus-associated host proteins.

Enveloped viruses obtain their envelopes during the process of budding from infected cells. During this process, however, these viruses acquire parts of the host cell membranes and host cell-derived proteins as integral parts of their mature envelopes. These host-derived components of viral envelopes may subsequently exhibit various effects on the life cycle of the virus; virus cell interactions, especially host response to virus-incorporated self-proteins; and the pathogenesis of the disease induced by these viruses. Although it was known for some time that various viruses incorporate host cell-derived proteins, the issue of the role of these proteins has received increased attention, specifically in connection with human immunodeficiency virus (HIV) infection and development of acquired immunodeficiency syndrome (AIDS) in humans. The aim of this review is to summarize our current knowledge of the analysis and role of host-derived proteins associated with enveloped viruses, with emphasis on the potential role of these proteins in the pathogenesis of AIDS. Clearly, differences in the clinical outcome of those nonhuman primates infected with simian immunodeficiency virus (SIV) that are disease resistant compared with SIV-infected species that are disease susceptible provide a unique opportunity to determine whether differences in the incorporation of distinct sets of host proteins play a role with distinct clinical outcomes.

Lack of enhancement of caprine arthritis encephalitis virus infection in monocyte-derived macrophage cultures by sera from goats that developed severe arthritis after vaccination and virus challenge.

We examined sera from goats that developed more rapid and severe clinical disease after vaccination with inactivated caprine arthritis encephalitis virus (CAEV) and virus challenge for CAEV infection-enhancing antibodies. Sera from one control and two vaccinated goats were examined for neutralization or enhancement of virus infection in caprine macrophages. Macrophage cultures were incubated with virus-serum mixtures, then washed and fed with fresh media and incubated. Culture fluid was collected at days 2,4 and 8 post-infection and assayed for reverse transcriptase (RT) activity. Serum from one of the vaccinated goats neutralized virus at 10(-2) and 10(-3) dilutions (p = 0.045 and p = 0.020, respectively). The neutralizing effect was lost at higher dilutions (10(-4) and 10(-5)) of the serum, but no enhancement of infection was seen. Serum from the other vaccinated goat did not show any significant neutralizing effect at either 10(-2) or 10(-3) dilutions and increased infection (40% or greater) at higher dilutions, but the increases were not statistically significant. Therefore, there was no evidence of virus infection-enhancing activity in these sera that would suggest that the severe disease experienced by the vaccinated animals was due to serum enhancement of infection. Alternately, the severe arthritis observed could have resulted from the pro-inflammatory activities of cytokines and chemokines produced by macrophages upon phagocytosis, or receptor-mediated uptake of CAEV-antibody complexes.

Xenoinfection of nonhuman primates by feline immunodeficiency virus.

New viral infections in humans usually result from viruses that have been transmitted from other species as zoonoses. For example, it is accepted widely that human immunodeficiency virus (HIV) is the result of the propagation and adaptation of a simian immunodeficiency virus (SIV) from nonhuman primates to man [1]. Previously, we reported productive infection of primary human cells in vitro by feline immunodeficiency virus (FIV) [2], a lentivirus that causes an immunodeficiency syndrome in cats similar to HIV in humans [3]. The present study extends these findings by demonstrating that cynomolgus macaques (Macaca fasicularis) infected with FIV exhibited clinical signs, including depletion of CD4+ cells and weight loss, that are consistent with FIV infection. The development of an antibody response to FIV gag-encoded proteins and detection of virus-specific sequences in sera, blood-derived cells, and necropsied tissue accompanied these changes. Moreover, the reactivation of FIV replication from latently infected cells was observed after stimulation in vitro with phorbol esters and in vivo with tetanus toxoid. The proposed use of lentiviruses in human gene therapy [4, 5] and of nonhuman cells and organs in xenotransplantation [6] has raised concerns about zoonoses as potential sources of new human pathogens. Therefore, the study of FIV infection of primate cells may provide insight into the principles underlying retroviral xenoinfections.

The role of in vitro-induced lymphocyte apoptosis in feline immunodeficiency virus infection: correlation with different markers of disease progression.

Human immunodeficiency virus infection is characterized by a progressive decline in the number of peripheral blood CD4(+) T lymphocytes, which finally leads to AIDS. This T-cell decline correlates with the degree of in vitro-induced lymphocyte apoptosis. However, such a correlation has not yet been described in feline AIDS, caused by feline immunodeficiency virus (FIV) infection. We therefore investigated the intensity of in vitro-induced apoptosis in peripheral blood lymphocytes from cats experimentally infected with a Swiss isolate of FIV for 1 year and for 6 years and from a number of long-term FIV-infected cats which were coinfected with feline leukemia virus. Purified peripheral blood lymphocytes were either cultured overnight under nonstimulating conditions or stimulated with phytohemagglutinin and interleukin-2 for 60 h. Under stimulating conditions, the isolates from the infected cats showed significantly higher relative counts of apoptotic cells than did those from noninfected controls (1-year-infected cats, P = 0.01; 6-year-infected cats, P = 0.006). The frequency of in vitro-induced apoptosis was inversely correlated with the CD4(+) cell count (P = 0. 002), bright CD8(+) cell count (P = 0.009), and CD4/CD8 ratio (P = 0. 01) and directly correlated with the percentage of bright major histocompatibility complex class II-positive peripheral blood lymphocytes (P = 0.004). However, we found no correlation between in vitro-induced apoptosis and the viral load in serum samples. Coinfection with feline leukemia virus enhanced the degree of in vitro-induced apoptosis compared with that in FIV monoinfected cats. We concluded that the degree of in vitro-induced apoptosis was closely related to FIV-mediated T-cell depletion and lymphocyte activation and could be used as an additional marker for disease progression in FIV infection.

Molecular and immunophenotypical characterization of a feline immunodeficiency virus (FIV)-associated lymphoma: a direct role for FIV in B-lymphocyte transformation?

We describe the histopathological, immunohistochemical, and molecular characterization of a lymphoma arising in a 7-year-old cat following experimental infection with feline immunodeficiency virus (FIV). The tumor was high grade and of B-cell lineage. The transformed cell had an immature phenotype (CD79a+, CD79b-, CD21-, immunoglobulin heavy and light chain negative), confirmed by antigen receptor gene analysis, which showed germ line configuration. Single-copy, clonally integrated FIV provirus was detected in tumor genomic DNA. FIV p24 antigen was not detected in tumor cells by immunostaining. This study provides the first evidence that the feline lentivirus may play a direct role in cell transformation under certain circumstances.

Encephalitis, lymphoid tissue depletion and secondary diseases associated with bovine immunodeficiency virus in a dairy herd.

Encephalitis, lymphoid tissue depletion and secondary infections occurred over a 5-yr-period in Holstein cows infected with bovine immunodeficiency virus (BIV). There were 59 cattle studied, the majority during 1991, when a severe environmental stress occurred, each with one or more primary causes of death, natural or by euthanasia, and most with several secondary diseases. The encephalitis was characterized by meningeal, perivascular and parenchymal infiltration with lymphocytes, occasional plasma cells and macrophages with perivascular edema in some cows. Affected areas included the cerebrum, cerebellum, and spinal cord with no particular distribution pattern recognized. The lymphoid depletion was primarily an absence of follicular development in nodes draining regions with secondary infections such as chronic mastitis and chronic suppurative pododermatitis. Paucity of lymphocytes in thymic-dependent regions of lymph nodes and the spleen suggested a primary depletion of T cells. Secondary infections were often multiple with each cow having several minor conditions, usually considered short-term and treatable. These included mastitis and pododermatitis, with many cows having non-responding abscesses, cellulitis and myositis attributed to injection site infections. A large number of the cattle had parturition difficulties such as dystocia, obturator paralysis, and metritis. Pulmonary, cardiovascular, and intestinal disease were recognized as both primary and secondary disease conditions. There was a high level of infection with bovine leukemia virus with 4 of the 59 cattle having lymphosarcoma. Under practical conditions, the infection with BIV has a different effect on the host than has been observed under experimental conditions. The presence of BIV combined with the stresses associated with parturition and a modern dairy production system were considered causal for the development of untreatable secondary diseases in immunocompromised cattle. The peak incidence in 1991 was attributed to increased environmental stress during renovation of the barn facility. During this time the cattle were kept on open pasture, exposed to an extremely wet winter, and spring weather conditions. The effect of co-infection with bovine leukemia virus, the influence of immunocompromise on the chronicity of mastitis, the relationship with laminitis and pododermatitis, and several questions related to viral transmission, complementarism with bovine leukemia virus, viral reactivation and immunoprophylaxis all remain as viable avenues for future investigations.

Cloning, sequencing and expression of the ovine interleukin 6 gene.

Gene amplification by reverse transcriptase PCR with heterologous primers has been used to obtain a cDNA clone encoding the structural sequences of ovine interleukin 6 from alveolar macrophages. This cDNA encodes a protein of M(r) = 23,429, which is 53% homologous in amino acid sequence to human IL = 6. The clone hybridizes to an RNA of size 1260 nt in alveolar macrophages, expression of which is potentiated by LPS. The ovine IL-6 structural gene has been cloned into the yeast expression vector pOGS40, and used to produce a recombinant protein. This protein is capable of causing increased immunoglobulin production in pokeweed mitogen stimulated ovine peripheral blood mononuclear cells at concentrations of 10-100 ng/ml, but it only causes very limited replication of B9 cells, a murine IL-6 dependent cell line. This is in contrast to recombinant human IL-6, which is capable of stimulating B9 cell proliferation, but not immunoglobulin production by ovine PBMC.

Lentivirus infection of macrophages.

The ovine and caprine lentiviruses infect monocytes, and the viral DNA is integrated into the cellular DNA. The provirus remains silent until the monocyte matures into a macrophage. Intrinsic to this maturation is the induction of a class of immediate early genes in the monocyte that includes the transcription factors JUN and FOS. These transcription factors are thought to couple short-term signals in the cell to long-term cellular differentiation by regulation of specific cellular genes. Thus, JUN and FOS bind to the AP-1 site in the promoters of cellular genes and activate their transcription, resulting in maturation of the monocyte into a macrophage. In addition, these cellular factors activate the same AP-1 sequence in the visna virus LTR, leading to transcriptional activation, full viral gene expression, and production of progeny virus. The expression of viral antigens in the context of MHC class II on the macrophage leads to the production of cytokines and a lymphoproliferative response that causes the lesions in specific target organs in an infected animal. We still understand only the framework of these events. The specific mechanisms by which viral genes alter macrophage gene expression and the molecular basis of different viral tropism for specific tissue macrophages, i.e. microglia, remain to be determined.

Lessons from caprine and ovine retrovirus infections.

Two lentiviruses that infect sheep and goats have been shown to be closely related to the human immunodeficiency virus (HIV). These ungulate lentiviruses cause a spectrum of diseases, including arthritis in their natural hosts. The molecular and cellular biology of these viruses as well as possible pathogenic mechanisms is compared to HIV-1 in order to identify common features and significant differences between the human and animals pathogens.