Stavudine entrapped lipid nanoparticles for targeting lymphatic HIV reservoirs

The main objective of present research study was to evaluate the potential of lipid nanoparticles for active delivery of an antiretroviral drug to lymphatic tissues. Stavudine entrapped drug loaded solid lipid nanoparticles (SLNs) were prepared and characterized for a variety of physicochemical parameters such as appearance, particle size, polydispersity index and zeta potential. The targeting potential of the prepared nanoparticles was investigated by carrying out ex vivo cellular uptake studies in macrophages which depicted several times enhanced uptake as compared to pure drug solution. Further, the lymphatic drug levels and organ distribution studies demonstrated efficiency of the developed nanoparticles for prolonged residence in spleenic tissues. Thus it was concluded that stavudine entrapped lipid carriers can be exploited for effective and targeted delivery to cellular and anatomical HIV reservoirs and may ultimately increase the therapeutic safety and reduce side effects.

KSHV manipulates Notch signaling by DLL4 and JAG1 to alter cell cycle genes in lymphatic endothelia

Increased expression of Notch signaling pathway components is observed in Kaposi sarcoma (KS) but the mechanism underlying the manipulation of the canonical Notch pathway by the causative agent of KS, Kaposi sarcoma herpesvirus (KSHV), has not been fully elucidated. Here, we describe the mechanism through which KSHV directly modulates the expression of the Notch ligands JAG1 and DLL4 in lymphatic endothelial cells. Expression of KSHV-encoded vFLIP induces JAG1 through an NFkappaB-dependent mechanism, while vGPCR upregulates DLL4 through a mechanism dependent on ERK. Both vFLIP and vGPCR instigate functional Notch signalling through NOTCH4. Gene expression profiling showed that JAG1- or DLL4-stimulated signaling results in the suppression of genes associated with the cell cycle in adjacent lymphatic endothelial cells, indicating a role for Notch signaling in inducing cellular quiescence in these cells. Upregulation of JAG1 and DLL4 by KSHV could therefore alter the expression of cell cycle components in neighbouring uninfected cells during latent and lytic phases of viral infection, influencing cellular quiescence and plasticity. In addition, differences in signaling potency between these ligands suggest a possible complementary role for JAG1 and DLL4 in the context of KS.

Low viral loads and lymphoid organ spheroids are associated with yellow head virus (YHV) tolerance in whiteleg shrimp Penaeus vannamei

Yellow head virus (YHV) is an invertebrate nidovirus that has caused mass mortality in penaeid shrimp since 1990. Several YHV types are known, but only the original type (YHV-type 1 or YHV-1) is highly virulent. Most studies have focused on acute YHV-1 infections and there is limited work on YHV-1 survivors. We compared moribund and surviving (14%) whiteleg shrimp Penaeus (Litopenaeus) vannamei from an experimental challenge with YHV-1. Although grossly normal, all survivors were positive for YHV-1 by specific, reverse transcriptase polymerase chain reaction (RT-PCR) assays, histological analysis or transmission electron microscopy (TEM), indicating that they were not resistant but tolerant to YHV-1. On the other hand, real-time PCR analysis revealed that mean YHV-1 copies/ng total RNA for survivors (2.8x10(4) +/- 6.9x10(4)) were approximately 40 times lower (P<0.05) than those in moribund shrimp (1.2x10(6) +/- 6.7x10(5)copies/ng total RNA). This was confirmed by strong positive immunohistochemical and in situ hybridization (ISH) reactions for YHV-1 in lymphoid organ tubules (LOT) of moribund shrimp and weak positive reaction only in lymphoid organ spheroids (LOS) of survivors. TEM revealed morphologically complete YHV virions in both groups. Furthermore, immuno-TEM and Western blot analysis revealed that YHV-1 structural proteins gp116 and p20 were present at comparable reactive levels in each group. Thus, YHV-1 tolerance was not associated with absence of gp116 as previously reported for palaemonid shrimp. Instead, it was associated with the presence of YHV-positive LOS and a relatively low viral load.

Synthesis and biological evaluation of two glycerolipidic prodrugs of didanosine for direct lymphatic delivery against HIV

Novel glycerolipidic prodrugs of didanosine and didanosine monophosphate designed to by-pass the hepatic first pass metabolism were synthesized and tested for their cytotoxicity and anti-HIV-1 activity. Formulation as liposomes of dipalmitoylphosphatidylcholine was elaborated. A simple quantitative HPLC-UV method was developed and validated, and ESI-MS was used for qualitative purpose. These two prodrugs exhibited promising biological activities against HIV-1 in in vitro infected cell culture.

Rapid dissemination of SIV following oral inoculation

OBJECTIVE

To assess the earliest events regarding transmission and dissemination of SIV following nontraumatic oral inoculation in macaques.

DESIGN

Juvenile and neonate rhesus macaques were orally inoculated with SIVmac251 and necropsied at 1, 2, 4, 7, or 14 days post-inoculation. Sites of transmission and the extent of viral spread were assessed by using molecular techniques and in situ hybridization to identify SIV nucleic acid in lymphoid and nonlymphoid tissues.

RESULTS

This study demonstrates that 1 day post-exposure, SIV nucleic acid was detected in the alimentary canal only in tissues proximal to the stomach, including the oral and esophageal mucosa as well as the tonsils. Following infection, virus was observed to spread rapidly to regional and peripheral lymph nodes by 1 and 2 days post-inoculation (dpi). Hundreds of copies of SIV-DNA were detected 4 dpi, increasing to > 10 000 copies/1 x 10(6) cells by 7 dpi. Identification of SIV positive T cells and macrophages implicates these cell types in viral spread, although dissemination of free virus is also likely.

CONCLUSIONS

Here the oral and esophageal mucosa, as well as tonsils, are demonstrated to be potential sites for viral infection upon nontraumatic oral exposure to SIV in macaques. The rapid dissemination following oral transmission observed in this study is reflective of SIV transmission across other mucosal surfaces. The rapidity with which SIV, and probably HIV, spreads throughout the lymphatics indicates a major obstacle for a vaccine amnestic immune response to eliminate infected cells prior to dissemination.

Low doses of hepadnavirus induce infection of the lymphatic system that does not engage the liver

Woodchuck hepatitis virus (WHV), which is closely related to human hepatitis B virus and is considered to be principally hepatotropic, invades the host's lymphatic system and persists in lymphoid cells independently of whether the infection is symptomatic and serologically evident or concealed. In this study, we show, with the woodchuck model of hepatitis B, that hepadnavirus can establish an infection that engages the lymphatic system, but not the liver, and persists in the absence of virus serological markers, including antiviral antibodies. This primary occult infection is caused by wild-type virus invading the host at a quantity usually not greater than 10(3) virions. It is characterized by trace virus replication progressing in lymphatic organs and peripheral lymphoid cells that, with time, may also spread to the liver. The infection is transmissible to virus-naive hosts as an asymptomatic, indefinitely long, occult carriage of small amounts of biologically competent virus. In contrast to residual silent WHV persistence, which normally endures after the resolution of viral hepatitis and involves the liver, primary occult infection restricted to the lymphatic system does not protect against reinfection with a large, liver-pathogenic WHV dose; however, the occult infection is associated with a swift recovery from hepatitis caused by the superinfection. Our study documents that the lymphatic system is the primary target of WHV infection when small quantities of virions invade a susceptible host.

Simian immunodeficiency virus encephalitis in the white matter and degeneration of the cerebral cortex occur independently in simian immunodeficiency virus-infected monkey

Highly active antiretroviral therapy (HAART) has been successful to reduce progression of acquired immunodeficiency syndrome (AIDS). Nevertheless, recent autopsy analysis of the brain from patients with human immunodeficiency virus (HIV)-1 infection reported same or even increasing numbers of AIDS encephalopathy. This insufficient effect of HAART for central nervous system (CNS) complication might be explained by independent pathogenetic processes in lymph node and CNS. We inoculated macaques with three Simian immunodeficiency virus (SIV) strains and investigated relationship between degree of the lymph node pathology and that of AIDS-related brain pathology. Animals infected with T-cell-tropic viruses SIVmac239 and SHIV-RT developed typical AIDS pathology in the lymph node 46 to 156 weeks after infection. The cerebral cortex of these animals showed focal or diffuse gliosis, and electron microscopic analysis demonstrated degenerative changes, such as accumulation of dense lamellar bodies in the dendrites and swelling of astrocytic processes. However, there was no evidence of microglial nodules or multinucleated giant cells in the white mater. The animals infected with macrophage-tropic SIV239env/MERT did not develop lymph node pathology of AIDS in the same or longer period of infection. The white mater of the animal, however, showed microglial nodules with multinucleated giant cells, a pathological hallmark of AIDS encephalopathy. SIV immunoreactivity was demonstrated in these giant cells as well as macrophage/microglia cells. On the other hand, there was no abnormality in the cerebral cortex. These findings suggest that there are two independent pathogenetic processes in AIDS encephalopathy: immune response against virus infected macrophage/microglial cells in the white mater without immunodeficiency and cortical degeneration caused in the late stage of AIDS.

Detection of infectious bursal disease virus in different lymphoid organs by single-step reverse transcription polymerase chain reaction and microplate hybridization assay

A rapid and sensitive method for the detection of infectious bursal disease virus (IBDV) RNA in different chicken lymphoid organs was developed. The method is based on a single-step reverse transcription polymerase chain reaction (RT-PCR) procedure and the enzyme-linked immunosorbent assay (ELISA) detection method of amplified products. Vaccinal IBDV strain and field isolates were used for the optimization of RT-PCR and for the determination of conditions for microplate hybridization and colorimetric detection of the amplicons. With this method, viral RNA could be detected in various stages of infection in samples of different lymphoid organs. Bursas and cecal tonsils were suitable organs for viral RNA detection at different times during IBDV infection. The RT-PCR/ELISA method can be applied for IBDV detection in routine diagnostic tests, which are not usually carried out because of the difficulties involved in isolating the virus.

Tissue distribution of bovine viral diarrhea virus antigens in persistently infected cattle

The tissue distribution and cellular localization of viral antigens in three cattle with persistent bovine viral diarrhea virus (BVDV) infection was studied. In three cases, necropsy findings of oral ulcers, abmasal ulcers and necrosis of Peyer's patches were suspected have been caused by BVDV infection. Non-cytopathic BVDV was isolated from a tissue pool of liver, kidneys and spleen. Immunohistochemical detection of BVDV showed that BVDV antigens were detected in both epithelial and nonepithelial cells in all examined organs, including the gastrointestinal tract, liver, pancreas, lung, lymphatic organs (spleen, lymph nodes), adrenal gland, ovary, uterus, and the mammary gland. These findings support the hypothesis that animals with persistent BVDV infection spread BVDV through all routes, and that infertility in BVDV infection is associated with the infection of BVDV in the ovaries and uteri.

Lymphatic dissemination and comparative pathology of recombinant measles viruses in genetically modified mice

The dissemination of the Edmonston measles virus (Ed-MV) vaccine strain was studied with genetically modified mice defective for the alpha/beta interferon receptor and expressing human CD46 with human-like tissue specificity and efficiency. A few days after intranasal infection, macrophages expressing Ed-MV RNA were detected in the lungs, in draining lymph nodes, and in the thymus. In lymph nodes, large syncytia which stained positive for viral RNA and for macrophage surface marker proteins were found and apoptotic cell death was monitored. In the thymus, smaller syncytia which stained positive for macrophage and dendritic cell markers were detected. Thus, macrophages appear to be the main vectors for dissemination of MV infection in these mice; human macrophages may have a similar function in the natural host. We then compared the pathogenicities of two recombinant viruses lacking the C or V nonstructural proteins to that of the parental strain, Ed-MV. These viruses were less effective in spreading through the lymphatic system and, unlike Ed-MV, were not detected in the liver. After intracerebral inoculation the recombinant viruses caused lethal disease less often than Ed-MV and induced distinctive patterns of gliosis and inflammation. Ed-MV was reisolated from brain tissue, but its derivatives were not. C- and V-defective viruses should be considered as more-attenuated MV vaccine candidates.

Porcine reproductive and respiratory syndrome virus (PRRSV): kinetics of infection in lymphatic organs and lung

Pigs were infected by the oronasal route with European isolates of the porcine reproductive and respiratory syndrome virus (PRRSV; I10 and Cobbelsdorf). The kinetics of infection in lymphatic organs and the lung were analysed by immunofluorescence detection of virus antigen, re-isolation of the virus and reverse transcription--polymerase chain reaction (RT-PCR) for PRRSV-specific RNA. The kinetics of PRRSV infection proceeded in three phases, irrespective of the varying infestation of lymphatic organs within the first days post-infection (p.i.). First, an early acute infection of lymphatic organs developed within the first week and was characterized by a high number of antigen-positive macrophages. Second, a delayed acute infection of the lung was observed, which was most pronounced during the second and third week p.i. when a high number of infected alveolar macrophages was observed. The acute infection of lymphatic organs had resolved at this time. Infected cells in the lung were predominantly located in pneumonic lesions. Third, a persistent infection was demonstrated by RT-PCR and immunohistology when the experiments were terminated at day 49 p.i. The virus persisted in lymphatic organs, especially in the tonsils, and in the lung. At this stage, indications for a re-occurrence of acute infection were observed in restricted areas of the lung.

Homing of negatively charged albumins to the lymphatic system: general implications for drug targeting to peripheral tissues and viral reservoirs

The present study shows the lymphatic distribution of the negatively charged anti-HIV-1 agents succinylated or aconytilated human serum albumins (HSAs) in rats. Quantitation of blood and lymphatic concentrations of these proteins was performed through fluorescence detection of the fluorescein isothiocyanate (FITC)-labeled proteins. At several time points after i.v. injection, samples were taken from the cannulated thoracic duct and the carotid artery. Distribution of the negatively charged albumins (NCAs) to lymph was much more rapid than that of albumin itself and was dependent on the total net negative charge added to the protein: the half-life times of lymphatic equilibration were 15, 30, and 120 min for FITC-labeled aconytilated HSA, FITC-labeled succinylated HSA, and FITC-labeled HSA, respectively. Lymph to blood concentration ratios of the studied compounds obtained at steady state approached unity. In addition, the fluorescence in both body fluids was shown to represent unchanged labeled proteins. It was therefore inferred that the NCAs efficiently passed the endothelial barrier from blood to the interstitial compartment. Subsequently, we studied whether a specialized process was involved in the endothelial passage of the NCAs to the lymph. The following observations supported such a mechanism: a) preinjection of the scavenger receptor blockers polyinosinic- and formaldehyde-treated HSA reduced the transport from blood to the lymphatic compartment of FITC-labeled aconytilated HSA by more than 90%; b) the rate of lymphatic distribution was largely reduced when the body temperature of the rat was lowered to 28 degrees; and c) pre-administration of chloroquine resulted in a significant reduction in the lymphatic distribution of the NCAs. These data collectively indicate that a scavenger receptor-mediated process is involved in the transendothelial transport of NCAs. In situ localization in lymph nodes of the rat showed that FITC-labeled aconytilated and succinylated HSA are mainly present in the germinal center and parafollicular zones. The efficient distribution of these anionized proteins to the lymphatic system is of particular interest for HIV therapy, taking into account that replication of HIV mainly takes place in the lymphoid system. The observation that macromolecules, through charge modification, can extravasate through a receptor-mediated transcytotic process is potentially of major importance for the delivery of drugs with macromolecular carriers to cells not directly in contact with the blood.

Immunohistochemical demonstration of African horse sickness viral antigen in tissues of experimentally infected equines

African horse sickness virus (AHSV) antigen was demonstrated immunohistochemically in formalin-fixed, paraffin-embedded sections of tissues collected from three ponies suffering from the peracute form of the disease and from one pony affected by the fever form. The pattern of the antigen distribution indicated a particular organ tropism characterised by an accumulation of AHSV antigen in cardio-pulmonary tissues of the animals with the peracute disease and in the spleen of the pony with the fever form. AHSV antigen was identified in endothelial cells of small blood vessels, particularly capillaries and in large mono-nuclear cells resembling macrophages or reticular cells of lymphatic tissues. Occasional circulating mononuclear cells with the morphology of monocytes were also positively stained within the larger vessels. The immunohistochemical results confirm earlier work suggesting that AHSV may have different tropisms to particular organs during various forms of the disease and that different target cell populations exist in vivo. Immunohistochemistry may be an additional useful method for diagnostic and research purposes in AHS.

Transient virus infection and pathogenesis of a new HIV type 2 isolate, UC12, in baboons

We have previously shown that baboons (Papio cynocephalus) can be persistently infected with HIV-2 and some baboons progress to an AIDS-like disease with a CD4+ T cell decline, cachexia, alopecia, and Kaposi's sarcoma-like fibromatosis. In this study, we found that a new virus isolate, HIV-2UC12, replicated to high levels in baboon peripheral blood mononuclear cells (PBMCs) in vitro. Three baboons were subsequently inoculated and had plasma viral RNA loads that peaked between 15,000 and 7000 copies/ml at 2 weeks postinfection. Virus was isolated from the PBMCs for up to 6 months. Although PBMCs were subsequently virus culture negative, virus could be recovered from the spleen, lymph nodes, and tonsils, indicating that HIV-2 was sequestered within these lymphoid tissues. HIV-2-associated pathology included follicular lysis, vascular proliferation, and lymphoid depletion. This study indicated that HIV-2UC12 infection in baboons can cause HIV-associated pathological abnormalities within the lymphatic tissues and that the high level of HIV-2UC12 replication in vitro was not predictive of replication in vivo.

The XI AIDS conference and HIV-1 lymphopathy

The random reverse transcription of HIV-1 RNA into the genes of large dividing lymphocytes and transport of integrated proviral DNA within and between persons via migratory small cytoplasm depleted lymphocytes derived therefrom causes deterioration of the entire lymphopoietic system. Secondary results are progressive failure in homeostasis, loss of sensitivity to potentially therapeutic drugs, and inability to produce preventive vaccines. The world-wide prevention of HIV-1 sickness and other lymphopathic retroviral diseases will depend on greater individual cooperation, especially with respect to minimizing the numbers of infected lymphocytes which migrate between persons through blood, semen, uterine endocervical secretions and maternal colostrum.

The role of eukaryotic subtilisin-like endoproteases for the activation of human immunodeficiency virus glycoproteins in natural host cells

Proteolytic activation of the precursor envelope glycoproteins gp160 of human immunodeficiency virus type 1 (HIV-1) and gp140 of HIV-2, a prerequisite for viral infection, results in the formation of gp120/gp41 and gp125/gp36, respectively. Cleavage is mediated by cellular proteases. Furin, a member of the eukaryotic subtilisin family, has been shown to be an activating protease for HIV. Here, we compared the presence of furin and other mammalian subtilisins in lymphatic cells and tissues. Northern blot analyses revealed that furin and the recently discovered protease LPC/PC7 were the only subtilisin-like enzymes transcribed in such cells. Furin was identified as an enzymatically active endoprotease present in different lymphocytic, as well as monocytic, cell lines. When expressed from vaccinia virus vectors, the proprotein convertases were correctly processed, transported, and secreted into the media and enzymatically active. Coexpression of different subtilisins with the HIV envelope precursors revealed that furin and LPC/PC7 are able to cleave HIV-1 gp160. Moreover, both enzymes proteolytically processed the envelope precursor of HIV-2. gp140 was also cleaved to some extent by PC1, which is not, however, present in lymphatic cells. Furin- and LPC/PC7-catalyzed cleavage of HIV-1 gp160 resulted in biologically active envelope protein. In conclusion, among the known members of the subtilisin family, only furin and LPC/PC7 fulfill the requirements of a protease responsible for in vivo activation of HIV envelope glycoproteins.

Cellular targets of infection and route of viral dissemination after an intravaginal inoculation of simian immunodeficiency virus into rhesus macaques

We used the simian immunodeficiency virus (SIV)/rhesus macaque model to study events that underlie sexual transmission of human immunodeficiency virus type 1 (HIV-1). Four female rhesus macaques were inoculated intravaginally with SIVmac251, and then killed 2, 5, 7, and 9 d later. A technique that detected polymerase chain reaction-amplified SIV in situ showed that the first cellular targets for SIV were in the lamina propria of the cervicovaginal mucosa, immediately subjacent to the epithelium. Phenotypic and localization studies demonstrated that many of the infected cells were likely to be dendritic cells. Within 2 d of inoculation, infected cells were identified in the paracortex and subcapsular sinus of the draining internal iliac lymph nodes. Subsequently, systemic dissemination of SIV was rapid, since culturable virus was detectable in the blood by day 5. From these results, we present a model for mucosal transmission of SIV and HIV-1.

Evolving understanding of the immunopathogenesis of HIV

Understanding of the immunopathogenesis of HIV infection is becoming more advanced as the activity of HIV infection in lymph nodes is appreciated and as improved virological measures permit more accurate quantitation of viral burden in patients at all stages of HIV disease. Although CD4+ cell counts remain important prognostic indicators, their role as a surrogate for direct antiviral activity has been questioned and increasing focus has been placed on more direct quantitative viral measures that are now available. After an initial explosive burst of viral replication during acute seroconversion that is downregulated by the immune system, these newer markers have revealed that viral replication is ongoing during the so-called "clinically latent" period of HIV infection. One of the most active sites of viral replication during this asymptomatic period is in lymphoid tissues. Over time, however, immunological control of HIV wanes, the site of replication shifts from the lymph nodes to other lymphoid organs, and disease progression ensues. The role of viral diversity in late-stage HIV disease is now well established, yet its role in pathogenesis and establishment of viruses resistant to antiviral agents is not fully established. Increased understanding of how HIV causes immune dysfunction may help us control direct and indirect (opportunistic) complications of HIV infection.

Dynamics of viral spread in bluetongue virus infected calves

The kinetics of viremia and sites of viral replication in bluetongue virus (BTV) infected calves were characterized by virus isolation, serology and immunofluorescence staining procedures. In addition, the role of the regional lymph node and lymphatics draining inoculated skin in the pathogenesis of BTV infection was determined by analyzing efferent lymph collected from indwelling cannulas. Viremia persisted for 35 to 42 days after inoculation (DAI) and virus co-circulated with neutralizing antibodies for 23 to 26 days. Virus was first isolated from peripheral blood mononuclear (PBM) cells at 3 DAI, after stimulation of PBM cells with interleukin 2 and mitogen. BTV was frequently isolated from erythrocytes, platelets and stimulated PBM cells but never from granulocytes and rarely from plasma during viremia. Virus was consistently isolated from erythrocytes late in the course of viremia. Interruption of efferent lymph flow by cannulation delayed the onset of viremia to 7 DAI. BTV was infrequently isolated from lymph cells, and few fluorescence positive cells were observed after lymph and PBM cells were labelled with a BTV-specific monoclonal antibody. Virus was isolated from spleen by 4 DAI and most tissues by 6 DAI, whereas virus was isolated from bone marrow only at 10 DAI. Virus was not isolated from any tissue after termination of viremia. It is concluded that primary viral replication occurred in the local lymph node and BTV then was transported in low titer to secondary sites of replication via infected lymph and PBM cells. We speculate that virus replication in spleen resulted in release of virus into the circulation and non-selective infection of blood cells which disseminated BTV to other tissues. Virus association with erythrocytes likely was responsible for prolonged viremia, although infected erythrocytes eventually were cleared from the circulation and persistent BTV infection of calves did not occur.