Pathogenesis of lentivirus infections

INIBIÇÃO DOS LENTIVÍRUS DE PEQUENOS RUMINANTES POR DROGAS ANTIVIRAIS

RESUMO Inibidores da enzima transcriptase reversa e da protease foram avaliados quanto ao seu efeito inibitório na replicação do Vírus da Artrite Encefalite Caprina (CAEV) cepa CAEV Cork e do vírus Maedi-Visna (MVV) cepa K1514 cultivados em células fibroblásticas de caprinos. Os fármacos utilizados foram: lamivudina, didanosina, estavudina, zidovudina, efavirenz, atazanavir e lopinavir/ritonavir. A maior concentração utilizada para lamivudina, estavudina, zidovudina e efavirenz foi 500 ?M, para atazanavir foi 50 ?M e 5,0 ?M para lopinavir/r e didanosina. A atividade antiviral in vitro foi pesquisada por meio da avaliação da viabilidade celular através da redução do MTT e pela pesquisa de inibição dos efeitos citopáticos (CPE) dos vírus. A replicação dos vírus só não foi completamente bloqueada pelos inibidores de protease (IP) atazanavir e lopinavir/r enquanto os demais apresentaram eficácia antiviral significativa em diferentes concentrações. Os IP juntamente com o efavirenz, não mostraram atividade antiviral quando foram avaliados pela técnica de redução do MTT. Esses dados indicam que os fármacos inibidores da transcriptase reversa lamivudina, didanosina, estavudina e zidovudina são eficazes na inibição in vitro dos lentivírus de pequenos ruminantes.

Non-polymeric nano-carriers in HIV/AIDS drug delivery and targeting

Development of an effective drug delivery approach for the treatment of HIV/AIDS is a global challenge. The conventional drug delivery approaches including Highly Active Anti Retroviral Therapy (HAART) have increased the life span of the HIV/AIDS patient. However, the eradication of HIV is still not possible with these approaches due to some limitations. Emergence of polymeric and non-polymeric nanotechnological approaches can be opportunistic in this direction. Polymeric carriers like, dendrimers and nanoparticles have been reported for the targeting of anti HIV drugs. The synthetic pathways as well polymeric framework create some hurdles in their successful formulation development as well as in the possible drug delivery approaches. In the present article, we have discussed the general physiological aspects of the infection along with the relevance of non-polymeric nanocarriers like liposomes, solid lipid nanoparticles (SLN), ethosomes, etc. in the treatment of this disastrous disease.

HIV-1 neuroimmunity in the era of antiretroviral therapy

Human immunodeficiency virus type 1 (HIV-1)-associated neurocognitive disorders (HAND) can affect up to 50% of infected people during the disease course. While antiretroviral therapies have substantively increased the quality of life and reduced HIV-1-associated dementia, less severe minor cognitive and motor deficits continue. Trafficking of HIV-1 into the central nervous system (CNS), peripheral immune activation, dysregulated glial immunity, and diminished homeostatic responses are the disease-linked pathobiologic events. Monocyte-macrophage passage into the CNS remains an underlying force for disease severity. Monocyte phenotypes may change at an early stage of cell maturation and immune activation of hematopoietic stem cells. Activated monocytes are pulled into the brain in response to chemokines made as a result of glial inflammatory processes, which in turn, cause secondary functional deficits in neurons. Current therapeutic approaches are focused on adjunctive and brain-penetrating antiretroviral therapies. These may attenuate virus-associated neuroinflammatory activities thereby decreasing the severity and frequency of HAND.

A coat of many colors: neuroimmune crosstalk in human immunodeficiency virus infection

The use of antiretroviral therapy has reduced mortality and increased the quality of life of HIV-1-infected people, particularly in more developed countries where access to treatment is more widespread. However, morbidities continue, which include HIV-1-associated neurocognitive disorders (HAND). Subtle cognitive abnormalities and low-level viral replication underlie disease. The balance between robust antiviral adaptive immunity, neuronal homeostatic mechanisms, and neuroprotective factors on one hand and toxicities afforded by dysregulated immune activities on the other govern disease. New insights into the pathobiological processes for neuroimmune-linked disease and ways to modulate such activities for therapeutic gain are discussed. Better understanding of the complexities of immune regulation during HAND can improve diagnosis and disease outcomes but is also relevant for the pathogenesis of a broad range of neurodegenerative disorders.

[Implication of the blood-brain barrier in neurological diseases: part II]

The main characteristic of the blood-brain-barrier (BBB) is its extremely low permeability, due to tight intercellular endothelial junctions and a variety of transporters, which provides the brain with a unique protection against the potential toxicity of several xenobiotics, but also constitutes a major limitation to drug delivery to the central nervous system. Several dysfunctions of the BBB have been recently implicated in the pathophysiology of neurological diseases: inflammatory, vascular, tumoral, infectious and neurodegenerative diseases. Based on a better knowledge of the BBB biology, new therapeutic strategies are emerging, which by-pass the BBB or take advantage of the selective expression of membrane proteins by brain endothelial cells or circulating leucocytes to target new drugs, such as the anti-VLA4 antibody recently approved for multiple sclerosis treatment. This review will focus on the recently described BBB dysfunctions presumably involved in various neurological diseases.

The blood-brain barrier in brain homeostasis and neurological diseases

Brain endothelial cells are unique among endothelial cells in that they express apical junctional complexes, including tight junctions, which quite resemble epithelial tight junctions both structurally and functionally. They form the blood-brain-barrier (BBB) which strictly controls the exchanges between the blood and the brain compartments by limiting passive diffusion of blood-borne solutes while actively transporting nutrients to the brain. Accumulating experimental and clinical evidence indicate that BBB dysfunctions are associated with a number of serious CNS diseases with important social impacts, such as multiple sclerosis, stroke, brain tumors, epilepsy or Alzheimer's disease. This review will focus on the implication of brain endothelial tight junctions in BBB architecture and physiology, will discuss the consequences of BBB dysfunction in these CNS diseases and will present some therapeutic strategies for drug delivery to the brain across the BBB.

HIV infection of the central nervous system: clinical features and neuropathogenesis

Almost 65 million people worldwide have been infected with HIV since it was first identified in the early 1980s. Neurologic disorders associated with HIV type 1 affect between 40% and 70% of infected individuals. The most significant of these disorders include HIV-associated neurocognitive disorder, which comprises HIV-associated dementia, mild neurocognitive disorder, and asymptomatic neurocognitive impairment. Despite the availability of combination antiretroviral therapy, HIV-related central nervous system disorders continue to represent a substantial personal, economic, and societal burden. This review summarizes the clinical manifestations, diagnosis, treatment, and pathogenesis of the primary HIV-associated central nervous system disorders.

Experimental infection of sheep with visna/maedi virus via the conjunctival space

Experiments were performed to determine whether visna/maedi virus (VMV), a small ruminant lentivirus (SRLV), could infect sheep via ocular tissues. The EV1 strain of VMV was administered into the conjunctival space of uninfected sheep, and the animals monitored for the presence of provirus DNA and anti-VMV antibodies in blood. The results showed that provirus DNA appeared in peripheral blood mononuclear cells of all animals within a few weeks of receiving either 10(6) TCID50 or 10(3) TCID50 of VMV. Of the animals receiving the higher dose of virus via the conjunctival space, two seroconverted by 7 and 10 weeks post-infection, one seroconverted 8 months post-infection, and one had not seroconverted by 15 months post-infection. With the lower virus dose, the animals infected via the trachea seroconverted by 4 and 14 weeks, respectively. After ocular infection with this dose, one animal showed a transitory seroconversion with low levels of antibody, peaking at 2 weeks post-administration. The remaining three of the animals infected via the eyes did not seroconvert over a period of 13 months. At post-mortem, evidence for the presence of proviral DNA was obtained from ocular tissue, lungs or mediastinal lymph node in both groups of animals. Histological analysis of lung tissue from animals receiving the lower dose of virus showed the presence of early inflammatory lesions. The results thus show for the first time that transmission of VMV can occur via ocular tissues, suggesting that the conjunctival space may be an additional route of natural transmission.

Increased loss of CCR5+ CD45RA- CD4+ T cells in CD8+ lymphocyte-depleted Simian immunodeficiency virus-infected rhesus monkeys

Previously we have shown that CD8(+) T cells are critical for containment of simian immunodeficiency virus (SIV) viremia and that rapid and profound depletion of CD4(+) T cells occurs in the intestinal tract of acutely infected macaques. To determine the impact of SIV-specific CD8(+) T-cell responses on the magnitude of the CD4(+) T-cell depletion, we investigated the effect of CD8(+) lymphocyte depletion during primary SIV infection on CD4(+) T-cell subsets and function in peripheral blood, lymph nodes, and intestinal tissues. In peripheral blood, CD8(+) lymphocyte-depletion changed the dynamics of CD4(+) T-cell loss, resulting in a more pronounced loss 2 weeks after infection, followed by a temporal rebound approximately 2 months after infection, when absolute numbers of CD4(+) T cells were restored to baseline levels. These CD4(+) T cells showed a markedly skewed phenotype, however, as there were decreased levels of memory cells in CD8(+) lymphocyte-depleted macaques compared to controls. In intestinal tissues and lymph nodes, we observed a significantly higher loss of CCR5(+) CD45RA(-) CD4(+) T cells in CD8(+) lymphocyte-depleted macaques than in controls, suggesting that these SIV-targeted CD4(+) T cells were eliminated more efficiently in CD8(+) lymphocyte-depleted animals. Also, CD8(+) lymphocyte depletion significantly affected the ability to generate SIV Gag-specific CD4(+) T-cell responses and neutralizing antibodies. These results reemphasize that SIV-specific CD8(+) T-cell responses are absolutely critical to initiate at least partial control of SIV infection.

Expression of the endoplasmic reticulum stress response marker, BiP, in the central nervous system of HIV-positive individuals

The prevalence of HIV-associated neurocognitive impairment (NCI), which includes HIV-associated dementia (HAD) and minor cognitive and motor disorder (MCMD), has been increasing. HIV-infected and/or activated macrophages/microglia in the brain initiate the neurodegeneration seen in HIV-associated NCI via soluble neurotoxic mediators, including reactive oxygen species, viral proteins and excitotoxins. Neurotoxic factors released by macrophages/microglia injure neurones directly and alter astrocytic homeostatic functions, which can lead to excitotoxicity and oxidative stress-mediated neuronal injury. Often, cells respond to oxidative stress by initiating the endoplasmic reticulum (ER) stress response. Thus, we hypothesize that ER stress response is activated in HIV-infected cortex. We used immunofluorescence and immunoblotting to assess expression patterns of the ER stress proteins, BiP and ATF6, in HIV-positive cortical autopsy tissue. Additionally, we performed immunofluorescence using cell type-specific markers to examine BiP staining in different cell types, including neurones, astrocytes and macrophages/microglia. We observed a significant increase in BiP expression by both immunoblotting and immunofluorescence in HIV-positive cortex compared with control tissue. Additionally, phenotypic analysis of immunofluorescence showed cell type-specific increases in BiP levels in neurones and astrocytes. Further, ATF-6beta, an ER stress response initiator, is up-regulated in the same patient group, as assessed by immunoblotting. These results suggest that ER stress response is activated in HIV-infected cortex. Moreover, data presented here indicate for the first time that numbers of macrophages/microglia increase in brains of MCMD patients, as has been observed in HAD.

Development of a candidate DNA vaccine against Maedi-Visna virus

DNA vaccine candidates against Maedi-Visna virus (MVV) infection in ovines were developed as an alternative to conventional vaccines. Candidates were constructed by cloning genes encoding the MVV gag polyprotein and gag proteins p16 and p25 fused to a beta-galactosidase reporter in a plasmid backbone. Transfection of different ovine cells showed a higher protein expression with plasmid lacZp16, which was hence further optimised by (i) removing a putative inhibitory sequence via reduction of the AU-content in the p16 gene or by (ii) introducing a secretory signal (Sc) to promote antigen secretion and increase its presentation to APCs. Unexpectedly, plasmids constructed on the basis of the first strategy by mutagenesis of lacZp16 (lacZp16mut(24)), led to a reduction in the expression of the antigen/reporter fusion in cultured ovine cells. This indicates that the high AU content in MVV does not inhibit protein expression. However, mice primed with lacZp16mut(24) and boosted with MVV protein displayed higher humoral response when compared with control lacZp16. The addition of the Sc signal (Sc-p16) led to lower amounts of intracellular antigen/reporter fusion in transfected ovine cells, thus confirming secretion. These findings correlate with in vivo experiments, which showed that mice primed with Sc-p16 and boosted with MVV exhibited stronger antibody responses when compared with control mice primed with lacZp16 and boosted with MVV. Stronger humoral responses were recorded by immunising mice with (i) Sc-p16 and lacZp16mut(24) plasmids together or with (ii) one plasmid containing both the mutations and the Sc signal.

Involvement of morbilliviruses in the pathogenesis of demyelinating disease

Two members of the morbillivirus genus of the family Paramyxoviridae, canine distemper virus (CDV) and measles virus (MV), are well-known for their ability to cause a chronic demyelinating disease of the CNS in their natural hosts, dogs and humans, respectively. Both viruses have been studied for their potential involvement in the neuropathogenesis of the human demyelinating disease multiple sclerosis (MS). Recently, three new members of the morbillivirus genus, phocine distemper virus (PDV), porpoise morbillivirus (PMV) and dolphin morbillivirus (DMV), have been discovered. These viruses have also been shown to induce multifocal demyelinating disease in infected animals. This review focuses on morbillivirus-induced neuropathologies with emphasis on aetiopathogenesis of CNS demyelination. The possible involvement of a morbillivirus in the pathogenesis of multiple sclerosis is discussed.

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.

HIV and antiretroviral therapy in the brain: neuronal injury and repair

Approximately 40 million people worldwide are infected with human immunodeficiency virus (HIV). Despite HIV's known propensity to infect the CNS and cause neurological disease, HIV neurocognitive disorders remain under-recognized. Although combination antiretroviral therapy has improved the health of millions of those living with HIV, the penetration into the CNS of many such therapies is limited, and patients' quality of life continues to be diminished by milder, residual neurocognitive impairment. Synaptodendritic neuronal injury is emerging as an important mediator of such deficits in HIV. By carefully selecting specific antiretrovirals and supplementing them with neuroprotective agents, physicians might be able to facilitate innate CNS repair, promoting enhanced synaptodendritic plasticity, neural function and clinical neurological status.

Neurologic and neurodevelopmental manifestations of pediatric HIV/AIDS: a global perspective

Neurodevelopmental abnormalities associated with HIV infection have been described since the first reports of pediatric AIDS in the 1980s. Before antiretroviral therapy (ART) became widely available, progressive HIV-1 encephalopathy (PHE) was reported in the US in 13-35% of children with HIV-1 infection and in 35-50% of children with AIDS. Introduction of ART can prevent PHE and reverse PHE present at ART initiation, but a high prevalence of residual problems has been described. Even though 90% of HIV-infected children live in the developing world, few children have access to ART and little is known regarding the neurological manifestations of perinatal HIV infection in those regions. Mechanisms of pediatric HIV-1 neuropathogenesis and factors associated with neurodevelopmental abnormalities in perinatally infected children are not yet fully understood. Studies have demonstrated that HIV-1 enters the CNS soon after infection and may persist in this compartment over the entire course of HIV-1 infection. The CNS is a distinct viral reservoir, differing from peripheral compartments in target cells and antiretroviral penetration. Neurotropic HIV-1 likely develops distinct genotypic characteristics in response to this unique environment. We reviewed the literature on pediatric neuroAIDS and identified gaps in the current knowledge.

Cultured early goat embryos and cells are susceptible to infection with caprine encephalitis virus

Zona-pellucida-free embryos at 8-16 cell stage were co-cultured for 6 days in an insert over a mixed cell monolayer infected with CAEV-pBSCA. Embryos were washed and transferred to an insert on CAEV indicator goat synovial membrane cells for 6 h, then they were washed and cultivated in B2 Ménézo for 24 h, finally, embryo cells were dissociated and cultivated on a feeder monolayer for 8 days. After 5 weeks, multinucleated giant cells typical of CAEV infection were observed in indicator GSM cell monolayers. In the acellular medium, the early embryonic cells produced at least 10(3.25) TCID50/ml over 24 h. The monolayer of cultivated embryonic cells developed cytopathic lesions within 8 days, and CAEV RNA, CAEV proviral DNA and protein p28 of the capsid were detected. All of these results clearly demonstrate that caprine early embryonic cells are susceptible to infection with CAEV and that infection with this virus is productive.

Serum containing ovine IgG2 antibody specific for maedi visna virus envelope glycoprotein mediates antibody dependent cellular cytotoxicity

Antibody-dependent cell-mediated cytotoxicity (ADCC) specific for maedi visna virus (MVV) has never been described. The IgG antibody response to MVV is restricted to an IgG1 response whilst MVV specific IgG2 is never seen in persistently infected sheep. To determine whether the isotypic restriction of the antibody response is responsible for the lack of ADCC, an ADCC assay was developed using polyclonal serum raised to recombinant MVV ENV protein. Sheep immunised with a recombinant GST:SUenv fusion protein in complete Freund's adjuvant produced an antibody response which contained IgG1 and IgG2 antibodies. The activity of this serum in an ADCC assay was compared to serum from persistently infected sheep. Serum from immunised sheep mediated ADCC reactions whilst no activity was ever seen in persistently infected sheep serum. IgG2 may therefore be the possible effector isotype for ADCC reactions against MVV. Failure of the IgG2 dependent ADCC system in vivo may contribute to the persistence of MVV-infected macrophages in vivo.

Gene therapy for transplantation with viral vectors – how much of the promise has been realised?

Gene therapy holds promise in preventing the development of many diseases. One of the possible applications is the management of organ transplantation. Over the years, advances in vector development have allowed the clinical progression of this form of therapy to become more attainable. Viral vector technology has proved to be better than non-viral vectors at ferrying therapeutic genes to cells. However, many deficiencies in viral vectors hinder the full realisation of gene-based therapy in transplantation. Here, these deficiencies and their ramifications for the future of viral vector development are fully analysed. The authors propose that the slow progress of gene therapy in transplantation may be related to the deficiencies in viral vectors.

Immunopathogenesis of acute AIDS virus infection

The pathogenesis of chronic HIV infection has long been envisioned as a slow process of immune degradation ultimately leading to overt immune deficiency and AIDS. However, recent studies suggest that the massive viral replication of acute infection initiates the pathogenic process, significantly degrading the immune system and setting up a sequence of events that years later leads to final decompensation and AIDS. The central player of the disease process appears to be the CD4(+) effector memory T cell population that resides in the extra-lymphoid immune effector sites of the body (e.g. gut, lung and genital tract), and has a crucial role in maintaining immune competence at the tissue-external environment interface. HIV and its monkey counterpart SIV specifically target these CCR5-expressing T cells, significantly depleting them in acute infection and, in AIDS-susceptible species (humans, Asian macaques), initiating and maintaining a state of hyperactivation that undermines their regeneration. With time, uncontrolled viral replication leads to loss of these cells in tissue below a crucial threshold, resulting in increased susceptibility to opportunistic infection.

HIV-1 associated dementia: symptoms and causes

Despite the use of highly active antiretroviral therapy (HAART), neuronal cell death remains a problem that is frequently found in the brains of HIV-1-infected patients. HAART has successfully prevented many of the former end-stage complications of AIDS, however, with increased survival times, the prevalence of minor HIV-1 associated cognitive impairment appears to be rising among AIDS patients. Further, HIV-1 associated dementia (HAD) is still prevalent in treated patients as well as attenuated forms of HAD and CNS opportunistic disorders. HIV-associated cognitive impairment correlates with the increased presence in the CNS of activated, though not necessarily HIV-1-infected, microglia and CNS macrophages. This suggests that indirect mechanisms of neuronal injury and loss/death occur in HIV/AIDS as a basis for dementia since neurons are not themselves productively infected by HIV-1. In this review, we discussed the symptoms and causes leading to HAD. Outcome from this review will provide new information regarding mechanisms of neuronal loss in AIDS patients.

Perils at mucosal front lines for HIV and SIV and their hosts

HIV-1 and simian immunodeficiency virus (SIV), as well as their hosts, face perils at mucosal front lines in early infection. At these sites, 'resting' CD4+ memory T cells fuel infection (because they are hosts for virus), depleting CD4+ memory T cells throughout the lymphoid tissues, particularly in the gut, and eliciting an immunosuppressive regulatory T-cell response that impairs host defence. But HIV-1 and SIV also risk elimination at the earliest stage of infection, at the mucosal point of entry, if founder populations of infected cells do not expand sufficiently to establish a self-propagating infection. Microbicides and vaccines could increase these viral vulnerabilities at mucosal front lines.

Diagnostic tests for small ruminant lentiviruses

Maedi visna virus and caprine arthritis encephalitis virus are closely related retroviruses that cause chronic inflammatory disease in small ruminants. The infections are characterised by insidious onset and slow progression. Diagnosis of infection is usually by serological testing. A variety of assays are available for this purpose, though the relative sensitivity and specificity of these assays has not been compared systematically. Here we review recent developments in laboratory diagnostic methods and their use in field diagnosis. The results suggest that a combination of ELISA and PCR might afford optimal detection of SRLV infection.

The neuropathogenesis of AIDS

HIV-associated dementia (HAD) is an important complication of the central nervous system in patients who are infected with HIV-1. Although the incidence of HAD has markedly decreased since it has become possible to effectively control viral replication in the blood by administering highly active antiretroviral therapy, a less severe form of HAD, comprising a milder cognitive and motor disorder, is now potentially a serious problem. Brain macrophages and microglia are the key cell types that are infected by HIV-1 in the central nervous system, and they are likely to mediate the neurodegeneration seen in patients with HAD; however, the precise pathogenesis of this neurodegeneration is still unclear. Here, we discuss the studies that are being carried out to determine the respective contributions of infection, and monocyte and macrophage activation, to disease progression.

Cloning, expression, purification, crystallization and preliminary crystallographic study of the protein module (BIV2-Helix) in the fusion core of bovine immunodeficiency-like virus (BIV) gp40

The fusion core of bovine immunodeficiency virus (BIV) gp40 is proposed to be involved in membrane fusion. However, no crystal structures are yet available. A predicted protein module BIV2-Helix of BIVgp40 has been expressed in Escherichia coli and purified by chromatography. Recombinant BIV2-Helix was crystallized using the hanging-drop vapour-diffusion technique at 291 K. The crystals were grown in MPD and belonged to the primitive rhombohedral space group R3, with unit-cell parameters a = 39.17, b = 39.17, c = 295.05 A and two molecules per asymmetric unit. X-ray diffraction data were collected to 1.76 A in the home laboratory from a single crystal.

HIV-1 and the hijacking of dendritic cells: a tug of war

Dendritic cells are critical for host immunity and are involved both in the innate and adaptive immune responses. They are among the first cells targeted by HIV-1 in vivo at mucosal sites. Dendritic cells can sequester HIV-1 in endosomal compartments for several days and transmit infectious HIV-1 to interacting T cells in the lymph node, which is the most important site for viral replication and spread. Initially, the cellular immune response developed against HIV-1 is strong, but eventually it fails to control and resolve the infection. The most dramatic effect seen on the immune system during untreated HIV-1 infection is the destruction of helper CD4(+) T cells, which leads to subsequent immune deficiency. However, the immunomodulatory effects of HIV-1 on different dendritic cell subpopulations may also play an important role in the pathogenesis of HIV-1. This review discusses the effects HIV-1 exerts on dendritic cells in vivo and in vitro, including the binding and uptake of HIV by dendritic cells, the formation of infectious synapses, infection, and the role of dendritic cells in HIV-1 pathogenesis.

Transmission of small ruminant lentiviruses

Small ruminant lentiviruses (SRLV) are classical slow retroviruses causing chronic inflammatory disease in a variety of target organs. The routes of transmission have been investigated and a large body of evidence has accumulated over many years. The main routes are through ingestion of infected colostrum and/or milk, or through inhalation of respiratory secretions. However, many studies also provide evidence that intrauterine infection may occur, though the extent and significance of this route is controversial. Embryos treated to IETS standards appear to pose very little risk of infection. SRLV have been detected in semen suggesting a potential source of transmission. However, such transmission has not been demonstrated to date. The application of control measures based on this information allows more efficient strategies to be developed which will reduce the rate of transmission.

Simian AIDS: an historical perspective

The author has had the unique opportunity to participate, over the last 35 years, in the retrovirus research field that proceeded and followed the discovery of human, simian and feline AIDS. The onset of human AIDS was certainly unanticipated, but in retrospect, the warning signs had been present for at least a decade in captive macaques. I will briefly summarize the key scientific knowledge and 'mindset' leading up to these events and will outline the major contributions and unanswered questions arising from the simian model of AIDS.

The role of dendritic cells in the pathogenesis of HIV-1 infection

Dendritic cells are professional antigen-presenting cells required for generation of adaptive immunity. These cells are one of the initial target cells for HIV-1 infection or capture of virions at site of transmission in the mucosa. DCs carrying HIV-1 will migrate to the lymphoid tissue where they can contribute to the dissemination of the virus to adjacent CD4+ T cells. In addition, HIV-1-exposed DCs may have impaired antigen-presenting capacity resulting in inadequate expansion of HIV-1-specific T cell responses. Here, we review the infection of different subtypes of DCs by HIV-1 and the relevance of these cells in the transmission and establishment of HIV-1 disease. In addition, we discuss the mechanisms through which HIV-1-DC interactions could be exploited to optimise the generation and maintenance of HIV-1-specific T cell immunity.

Increased intrathecal release of soluble fractalkine in HIV-infected patients

The CX(3)C chemokine fractalkine is suggested to play an important role in inflammatory brain diseases, for example, because of its chemotactic properties. To investigate the release of soluble fractalkine in HIV-induced brain diseases fractalkine levels were determined in cerebrospinal fluid (CSF) and serum samples of HIV-infected patients with (n = 10) and without (n = 23) HIV-induced CNS complications, using semiquantitative Western blot analysis. Fractalkine CSF levels were significantly elevated (p < 0.05) in HIV-infected patients with CNS diseases compared with those without, and compared with HIV-negative controls (n = 23). Fractalkine serum concentrations did not differ between the two groups of HIV-infected patients, but were significantly elevated (p < 0.05) in HIV-infected patients with CNS complications compared with HIV-negative controls. Levels of fractalkine did not correlate with the CSF and serum HIV load and other CSF parameters. In one patient with HIV-associated dementia and myelopathy CSF fractalkine levels decreased on initiation of antiretroviral therapy and subsequent clinical improvement. In conclusion, intrathecal fractalkine release was observed in the majority of patients with HIV infection. The highest levels of soluble fractalkine were detected in CSF (and serum) samples of patients with HIV-induced CNS disorders. These results suggest a dysregulation of brain soluble fractalkine release during HIV infection.

Early embryonic cells from in vivo-produced goat embryos transmit the caprine arthritis–encephalitis virus (CAEV)

The aim of this study was to investigate whether cells of early goat embryos isolated from in vivo-fertilized goats interact with the caprine arthritis-encephalitis virus (CAEV) in vitro and whether the embryonic zona pellucida (ZP) protects early embryo cells from CAEV infection. ZP-free and ZP-intact 8-16 cell embryos were inoculated for 2 h with CAEVat the 10(4) tissue culture infectious dose 50 (TCID50)/ml. Infected embryos were incubated for 72 h over feeder monolayer containing caprine oviduct epithelial cells (COECs) and CAEV indicator goat synovial membrane (GSM) cells. Noninoculated ZP-free and ZP-intact embryos were submitted to similar treatments and used as controls. Six days postinoculation, infectious virus assay of the wash fluids of inoculated early goat embryos showed typical CAEV-induced cytopathic effects (CPE) on indicator GSM monolayers, with fluids of the first two washes only. The mixed cell monolayer (COEC + GSM) used as feeder cells for CAEV inoculated ZP-free embryos showed CPE. In contrast, none of the feeder monolayers, used for culture of CAEV inoculated ZP-intact embryos or the noninoculated controls, developed any CPE. CAEV exposure apparently did not interfere with development of ZP-free embryos in vitro during the 72 h study period when compared with untreated controls (34.6 and 36% blastocysts, respectively, P > 0.05). From these results one can conclude that the transmission of infectious molecularly cloned CAEV-pBSCA (plasmid binding site CAEV) by embryonic cells from in vivo-produced embryos at the 8-16 cell stages is possible with ZP-free embryos. The absence of interactions between ZP-intact embryos and CAEV in vitro suggests that the ZP is an efficient protective embryo barrier.

Neuroimmune and neurovirological aspects of human immunodeficiency virus infection

Like most lentiviruses, HIV-1 causes both immune suppression and neurological disease. Neurological disease may occur at any stage of HIV infection but is most apparent with severe immune suppression. Cognitive impairment, reflected strikingly by HIV-associated dementia, has attracted intense interest since the outset of the HIV epidemic, and understanding of its pathogenesis has been spurred on by the emergence of several hypotheses outlining potential pathogenic mechanisms. The release of inflammatory molecules by HIV-infected microglia and macrophages and the concurrent neuronal damage play central roles in the conceptualization of HIV neuropathogenesis. Many inflammatory molecules appear to contribute to the pathogenic cascade and their individual roles remain undefined. At the same time, the abundance of virus in the brain and the type or strain of virus found in the brain may also be important codeterminants of neurological disease, as shown for other neurotropic viruses. Coreceptor use by HIV found in the brain appears to closely mirror what has been reported in systemic macrophages. The impact of HAART on viral genotype and phenotype found in the brain, and its relationship to clinical disease, remain uncertain. Several interesting animal models have been developed, using other lentiviruses, transgenic animals, and HIV-infected SCID mice, that may prove useful in future pathogenesis and therapeutic studies. Despite the progress in the understanding of HIV neuropathogenesis, many questions remain unanswered.

Progress in clinical neurosciences: The neuropathogenesis of HIV infection: host-virus interaction and the impact of therapy

Despite the availability of highly active antiretroviral therapy (HAART), primary HIV-related neurological diseases remain major problems in HIV clinics. The present review examines the pathogenesis of HIV-related dementia and the less severe minor cognitive and motor deficit, together with distal sensory and drug-induced toxic polyneuropathies. Abnormal host immune responses within the nervous system and the role of viral expression and diversity are emphasized in relation to neurovirulence. Induction of innate immune responses within the central and peripheral nervous systems, largely mediated by cells of macrophage lineage, appear to be common to the development of primary HIV-related neurological disease. Activation of these cell types results in the release of a cascade of inflammatory molecules including cytokines, chemokines, matrix metalloproteinases, and arachidonic acid metabolites that influence neuronal survival. Individual viral proteins encoded by envelope and tat genes and discrete sequences within these genes influence the extent to which these pro-inflammatory molecules are induced. At the same time, systemic immune suppression may influence the occurrence and severity of HIV-related neurological diseases. Implementation of HAART and neuroprotective treatments improves neurological function although the evolution of drug-resistant viral strains limits the sustained benefits of HAART.

Search for hepatitis C virus negative-strand RNA sequences and analysis of viral sequences in the central nervous system: evidence of replication

Patients with chronic hepatitis C are more likely to have significant changes in their physical and mental well-being than patients with liver disease of other etiology, and hepatitis C virus (HCV) has been occasionally implicated in diseases of the central nervous system. We analyzed the presence of the HCV negative-strand RNA sequence, which is the viral replicative intermediary, in autopsy brain tissue samples from six HCV-infected patients. Negative-strand HCV RNA was searched for by a strand-specific Tth-based reverse transcriptase PCR, and viral sequences amplified from brain tissue and serum were compared by single-strand conformational polymorphism analysis and direct sequencing. HCV RNA negative strands were detected in brain tissue in three patients. In two of these patients, serum- and brain-derived viral sequences were different and classified as belonging to different genotypes. In one of the latter patients, HCV RNA negative strands were detected in lymph node and, while being different from serum-derived sequences, were identical to those present in the brain. The results of the present study suggest that HCV can replicate in the central nervous system, probably in cells of the macrophage/monocyte lineage.

Highly activated CD8(+) T cells in the brain correlate with early central nervous system dysfunction in simian immunodeficiency virus infection

One of the consequences of HIV infection is damage to the CNS. To characterize the virologic, immunologic, and functional factors involved in HIV-induced CNS disease, we analyzed the viral loads and T cell infiltrates in the brains of SIV-infected rhesus monkeys whose CNS function (sensory evoked potential) was impaired. Following infection, CNS evoked potentials were abnormal, indicating early CNS disease. Upon autopsy at 11 wk post-SIV inoculation, the brains of infected animals contained over 5-fold more CD8(+) T cells than did uninfected controls. In both infected and uninfected groups, these CD8(+) T cells presented distinct levels of activation markers (CD11a and CD95) at different sites: brain > CSF > spleen = blood > lymph nodes. The CD8(+) cells obtained from the brains of infected monkeys expressed mRNA for cytolytic and proinflammatory molecules, such as granzymes A and B, perforin, and IFN-gamma. Therefore, the neurological dysfunctions correlated with increased numbers of CD8(+) T cells of an activated phenotype in the brain, suggesting that virus-host interactions contributed to the related CNS functional defects.

HIV-1-associated central nervous system dysfunction

Despite more than 15 years of extensive investigative efforts, a complete understanding of the neurological consequences of HIV-1 CNS infection remains elusive. Although the resources of numerous investigators have been focused on studies of HIV-1-associated CNS disease, the complex nature of the disease processes that underlie the clinical, pathological, and cellular manifestations of HIV-1 CNS infection have required a larger volume of studies than was initially envisioned. Several major areas remain as the focus of current research efforts. One of the more pressing issues facing researchers and clinicians alike is the search for correlates to the development of HIV-1-associated CNS neuropathology and the onset of HIVD. Although numerous parameters have been studied, none have been shown to be absolute predictors or markers of HIV-1-related CNS dysfunction. The identification of solid correlates of HIVD is an important goal that would permit clinical identification of individuals at risk for developing potentially crippling, life-threatening CNS abnormalities and would facilitate early treatment of nascent neurological problems. A more complete comprehension of the cellular foundations of CNS dysfunction and HIVD is also a fundamental part of strategies designed to treat or prevent HIV-1-associated CNS disease. Future investigations will strive to expand the body of knowledge concerning the complex interactions between infected and uninfected neuroglial cells and the roles of numerous cytokines, chemokines, and other soluble agents that are deregulated during HIV-1 CNS infection. In particular, a thorough understanding of the mechanisms of neurotoxicity may facilitate the development of new therapies that alleviate or eliminate the clinical consequences of CNS infection. Finally, investigators will continue to study HIVD within the context of single and combination drug therapies used in the treatment of HIV-1 infection and AIDS. As newer and more effective systemic treatments for HIV-1 infection and AIDS are introduced, the effects of these treatments on the onset, incidence, and severity of HIVD will also require intensive study. The impact of drug therapies on the ability of the CNS to act as an HIV-1 reservoir will also need to be addressed. Introduction of each new drug or drug combination will necessitate studies of drug penetration into the CNS and efficacy against the development of CNS abnormalities. Furthermore, as more effective treatments prolong the lifespan of individuals infected with HIV-1, the impact of extended survival on the occurrence and severity of HIVD will also require further investigations. The quest for answers to these and other questions will be complicated by the diversity of experimental systems used to study different aspects of HIV-1 CNS infection and HIVD. Each system has its own unique strengths and weaknesses. Clinical observations provide a continuous spectrum of symptomatic findings but reveal little about the underlying mechanisms of disease. In vivo imaging techniques, such as CT and MRI, also provide a continuum of observations, but the images are limited in their resolution. Neuropathological examinations of postmortem HIV-1-infected brains offer gross, cellular, and molecular views (including phenotypic and genotypic analyses of CNS viral isolates) of the diseased brain, but only provide a snapshot of the end-stage neurologic dysfunction. Studies that rely on animal surrogates for HIV-1, including SIV, simian-HIV (SHIV), feline immunodeficiency virus (FIV), visna virus, and HIV-1 SCID-hu models, permit experimental protocols that cannot be carried out in humans, but are limited by the fidelity with which each virus and animal model emulates the conditions and events observed in the human host. Finally, in vitro techniques, which include the use of primary cells and cell lines, adult or fetal human cell cultures, and BBB barrier model systems, are also convenient means by which aspe

Infecção experimental em cabritos pelo vírus da artrite encefalite

Vinte e quatro caprinos de uma semana de idade, soronegativos pela imunodifusão em gel de agar para artrite encefalite caprina (AEC), foram utilizados para estudo de infecção experimental pelo vírus da AEC. Dezesseis animais foram inoculados com lentivirus caprino, amostra Cork, oito pela via intravenosa e oito por instilação nasal. Oito animais serviram como controle, inoculados pelas vias intranasal ou intravenosa com 1ml de meio de cultura de células não infectadas. Os animais foram sacrificados aos 2, 6, 12 e 20 dias pós-inoculação (PI), e colhidas amostras do sistema nervoso central, articulações, tonsilas, linfonodos, pulmões, rins, timo, baço e intestinos delgado e grosso para histopatologia e imunoistoquímica. Um animal inoculado com o vírus da AEC pela via intranasal e sacrificado aos 20 dias PI apresentou imunomarcação positiva em um macrófago alveolar. Concluiu-se que a via aerógena é uma provável rota de infecção pelo vírus da AEC.

Targeting cell-free HIV and virally-infected cells with anti-HLA-DR immunoliposomes containing amphotericin B

OBJECTIVE

To evaluate the ability of liposomes bearing anti-HLA-DR Fab' fragments (immunoliposomes) and containing amphotericin B (AmB) to target and neutralize cell-free HIV-1 particles and virally-infected cells.

METHODS

The effect of AmB on the attachment and fusion of HIV-1(NL4-3) to Jurkat E6.1 cells has been evaluated using a p24 enzymatic assay. The ability of AmB to inhibit HIV-1-based luciferase reporter viruses pseudotyped with HXB2, AML-V and VSV-G envelopes has been evaluated in Jurkat E6.1 cells. The efficacy of free and immunoliposomal AmB to inhibit cell-free HIV, that have incorporated or not HLA-DR molecules, has been evaluated in HLA-DR/negative (NEG) 1G5 T cells and HLA-DR/positive (POS) Mono Mac 1 cells.

RESULTS

AmB inhibited HIV infectivity independently of the nature of viral envelope proteins. Pretreatment of HIV with AmB had no major effect on viral attachment and fusion process to Jurkat E6.1 cells. Immunoliposomal AmB (0.5 microg/ml) led to a 77% inhibition of replication of HLA-DR/POS HIV-1 with no cell toxicity, whereas free AmB had no significant antiviral activity at this concentration. A complete inhibition of viral replication was observed following incubation of viruses with immunoliposomal AmB (2.5 microg/ml). Anti-HLA-DR immunoliposomes containing AmB had no effect on the infectivity of HLA-DR/NEG HIV-1 particles in HLA-DR/NEG T lymphoid cells but completely inhibited replication of viruses in an HLA-DR/POS monocytic cell line.

CONCLUSION

The incorporation of neutralizing agents in anti-HLA-DR immunoliposomes could represent a novel therapeutic strategy to specifically target cell-free HIV particles and virally-infected cells to treat HIV infection more efficiently.

The effects of steroid hormones in HIV-related neurotoxicity: a mini review

This review examines the interaction of steroid hormones, glucocorticoids and estrogen, and gp120, a possible causal agent of acquired immune deficiency syndrome-related dementia complex. The first part of the review examines the data and mechanisms by which gp120 may cause neurotoxicity and by which these steroid hormones effect cell death in general. The second part of the review summarizes recent experiments that show how these steroid hormones can modulate the toxic effects of gp120 and glucocorticoids exacerbating toxicity, and estrogen decreasing it. We then examine the limited in vivo and clinical data relating acquired immune deficiency syndrome-related dementia complex and steroid hormones and speculate on the possible clinical significance of these findings with respect to acquired immune deficiency syndrome-related dementia complex.

Nuclear import of the retrotransposon Tf1 is governed by a nuclear localization signal that possesses a unique requirement for the FXFG nuclear pore factor Nup124p

Retroviruses, such as human immunodeficiency virus, that infect nondividing cells generate integration precursors that must cross the nuclear envelope to reach the host genome. As a model for retroviruses, we investigated the nuclear entry of Tf1, a long-terminal-repeat-containing retrotransposon of the fission yeast Schizosaccharomyces pombe. Because the nuclear envelope of yeasts remains intact throughout the cell cycle, components of Tf1 must be transported through the envelope before integration can occur. The nuclear localization of the Gag protein of Tf1 is different from that of other proteins tested in that it has a specific requirement for the FXFG nuclear pore factor, Nup124p. Using extensive mutagenesis, we found that Gag contained three nuclear localization signals (NLSs) which, when included individually in a heterologous protein, were sufficient to direct nuclear import. In the context of the intact transposon, mutations in the NLS that mapped to the first 10 amino acid residues of Gag significantly impaired Tf1 retrotransposition and abolished nuclear localization of Gag. Interestingly, this NLS activity in the heterologous protein was specifically dependent upon the presence of Nup124p. Deletion analysis of heterologous proteins revealed the surprising result that the residues in Gag with the NLS activity were independent from the residues that conveyed the requirement for Nup124p. In fact, a fragment of Gag that lacked NLS activity, residues 10 to 30, when fused to a heterologous protein, was sufficient to cause the classical NLS of simian virus 40 to require Nup124p for nuclear import. Within the context of the current understanding of nuclear import, these results represent the novel case of a short amino acid sequence that specifies the need for a particular nuclear pore complex protein.

Antiviral treatment normalizes neurophysiological but not movement abnormalities in simian immunodeficiency virus-infected monkeys

Simian immunodeficiency virus (SIV) infection of rhesus monkeys provides an excellent model of the central nervous system (CNS) consequences of HIV infection. To discern the relationship between viral load and abnormalities induced in the CNS by the virus, we infected animals with SIV and later instituted antiviral treatment to lower peripheral viral load. Measurement of sensory-evoked potentials, assessing CNS neuronal circuitry, revealed delayed latencies after infection that could be reversed by lowering viral load. Cessation of treatment led to the reappearance of these abnormalities. In contrast, the decline in general motor activity induced by SIV infection was unaffected by antiviral treatment. An acute increase in the level of the chemokine monocyte chemoattractant protein-1 (MCP-1) was found in the cerebrospinal fluid (CSF) relative to plasma in the infected animals at the peak of acute viremia, likely contributing to an early influx of immune cells into the CNS. Examination of the brains of the infected animals after return of the electrophysiological abnormalities revealed diverse viral and inflammatory findings. Although some of the physiological abnormalities resulting from SIV infection can be at least temporarily reversed by lowering viral load, the viral-host interactions initiated by infection may result in long-lasting changes in CNS-mediated functions.

In vivo infection of ramified microglia from adult cat central nervous system by feline immunodeficiency virus

Infection of microglial cells by the human immunodeficiency virus (HIV) is supposed to play an important role in the pathogenesis of AIDS-related central nervous system (CNS) complications. So far, however, experimental data about interactions between HIV and ramified microglia from the adult CNS were only occasionally reported, making it difficult to understand the exact nature of pathogenic events contributing to HIV-encephalopathy. Therefore, we used the animal model of feline immunodeficiency virus (FIV) infection of domestic cats to establish an experimental system which is suitable for studying the relationships between an immunodeficiency virus and the mature ramified microglia of the central nervous system. By means of density gradient centrifugation approximately 95% pure microglial cells could be isolated from adult feline brain that were characterized by their CD45(low) phenotype. Resident microglia extracted from the CNS of experimentally infected cats harbored FIV-specific DNA and cocultivation with mitogen-activated, but uninfected peripheral blood mononuclear cells (PBMC) resulted in recovery of high-titered infectious virus. Double labeling of brain cell monocultures explanted from persistently infected animals for both microglia and FIV markers disclosed less than 1% of viral antigen expressing microglial cells. This suggests that during the subclinical phase of the infection only a small number of brain-resident macrophages are productively infected. However, interaction of FIV-infected microglia and inflammatory lymphocytes may promote viral replication, thus supporting viral spread in brain tissue.

Sexual transmission and propagation of SIV and HIV in resting and activated CD4+ T cells

In sexual transmission of simian immunodeficiency virus, and early and later stages of human immunodeficiency virus-type 1 (HIV-1) infection, both viruses were found to replicate predominantly in CD4(+) T cells at the portal of entry and in lymphoid tissues. Infection was propagated not only in activated and proliferating T cells but also, surprisingly, in resting T cells. The infected proliferating cells correspond to the short-lived population that produces the bulk of HIV-1. Most of the HIV-1-infected resting T cells persisted after antiretroviral therapy. Latently and chronically infected cells that may be derived from this population pose challenges to eradicating infection and developing an effective vaccine.

Comparison of a maedi-visna virus CA-TM fusion protein ELISA with other assays for detecting sheep infected with North American ovine lentivirus strains

A maedi-visna virus CA-TM fusion protein ELISA (MVV ELISA) was evaluated for the detection of antibody in sheep infected with North American ovine lentivirus (OvLV). The results of the MVV ELISA were compared with other assays for OvLV antibody and with viral infection in an intensively studied group of 38 sheep with a high prevalence of OvLV infection and disease. The sensitivity, specificity, and concordance of assays for OvLV antibody (MVV ELISA, indirect ELISA, Western blot, and AGID), virus (virus isolation, PCR, antigen ELISA), and OvLV-induced disease in each animal were compared with OvLV infection status as defined by a positive result in two or more of the assays. Five sheep met the criteria for absence of OvLV infection. The sensitivity of the MVV ELISA in detecting OvLV infected sheep was 64%, whereas the sensitivity of the other three tests for antibody ranged from 85 to 94%. All the antibody assays were 100% specific in this group of animals. Of the assays for virus, the PCR test had the highest sensitivity and the best concordance with OvLV infection, but it also had the lowest specificity of any of the virus or antibody assays. Among the antibody tests, the concordance of the MVV ELISA compared most favorably with the AGID test for detecting OvLV-infected sheep. Analysis of serum samples from 28 lambs experimentally-infected with one of three North American strains of OvLV suggested that there were no significant strain differences detectable by antibody assay. Twenty virus-inoculated lambs were positive by both the MVV ELISA and the AGID test, five lambs were MVV ELISA negative and AGID test positive, and three lambs were MVV ELISA positive and AGID test negative. No pre-inoculation samples were positive by either assay. In a longitudinal study involving seven lambs, antibodies to OvLV were detected by AGID 3-5 weeks post-inoculation, but were not detected by MVV ELISA until 5-10 weeks post-inoculation. Among 128 naturally and experimentally-infected sheep that were seropositive in the AGID test, the overall sensitivity of the MVV ELISA was higher in the naturally infected sheep (84%) than in the experimentally infected sheep (69%). The data indicated that the MVV ELISA represents a less sensitive, but specific alternative for the detection of OvLV antibodies.

Retroviral sequences in rheumatoid arthritis synovium

There are several relationships between retroviruses and cellular transformation, as well as retroviruses being involved in the development of autoimmune diseases. Retroviruses have been discussed as etiologic agents modulating or triggering certain pathways in the pathogenesis of rheumatoid arthritis (RA). However, none of the currently known retroviruses has been identified as specific for RA. Due to the unique properties of retroviruses, distinct experimental approaches can be used to detect retroviral activity in cells and tissues. Current research in RA using state-of-the-art molecular biology techniques includes both the search for exogenous and endogenous retroviral gene sequences in synovium of patients with RA.

Human T cell leukemia virus type-I and rheumatoid arthritis

HTLV-I is a retrovirus known as an oncogenic virus for human. This virus, initially found as a causative agent for adult T cell leukemia, has been lately focused as a causative virus for several autoimmune disorders. Here we described the characteristics of polyarthritis in HTLV-I careers, which is indistinguishable from idiopathic rheumatoid arthritis (RA). The relationship between arthritis and this virus was clearly proved by epidimiological study. Moreover, we presented transactivating gene of this virus, tax, is responsible for proliferation of synovial cells. This was proved by Tax transgenic mice, which present chronic destructive arthritis resembling human RA. Other autoimmune disorders, such as Sjögren's syndrome and uveitis, are also reviewed.