An ultrastructural pathologist's views on fibroblasts, modified smooth muscle cells, wound healing, stenosing arteriopathies, Kawasaki disease, Dupuytren's contracture, and the stroma of carcinomas

It wasn't until 1960 that the dense bodies of the peripheral actin arrays of fibroblasts were finally visualized, i.e., stress fibers (SFs). Mistakenly assumed that its SFs turned the fibroblast into a unique cell situated somewhere in a continuum between it and a smooth muscle cell (SMC), it was descriptively named a "myofibroblast" (MF). Automatically, spindle cells with SFs and/or smooth muscle actin by SMA IHC-staining, became MFs, although endothelial cells, pericytes, modified SMCs (mSMC), and myoepithelial cells all contain SFs. An invisible "intermediate" cell was hypothesized to exist somewhere between SMA-negative and positive fibroblasts, and named a "proto-myofibroblast". The sub-epithelial spindle cells of normal and malignant tumors of the GI, GU, and respiratory tracts are all fibroblasts with SFs. The second erroneous myofibroblast came from a 1971 rat wound healing study and its 1974 human counterpart. Updated analysis of the papers' TEMs proved that the cells are mSMCs and not fibroblasts (AKA: MFs). The pathognomonic cells of Dupuytren's contracture are mSMCs and fibroblasts and that of the stenosing arteriopathy of Kawasaki Disease and other similar arteriopathies are mSMCs. TEM remains a powerful tool.

CD84 is markedly up-regulated in Kawasaki disease arteriopathy

The major goals of Kawasaki disease (KD) therapy are to reduce inflammation and prevent thrombosis in the coronary arteries (CA), but some children do not respond to currently available non-specific therapies. New treatments have been difficult to develop because the molecular pathogenesis is unknown. In order to identify dysregulated gene expression in KD CA, we performed high-throughput RNA sequencing on KD and control CA, validated potentially dysregulated genes by real-time reverse transcription-polymerase chain reaction (RT-PCR) and localized protein expression by immunohistochemistry. Signalling lymphocyte activation molecule CD84 was up-regulated 16-fold (P < 0·01) in acute KD CA (within 2 months of onset) and 32-fold (P < 0·01) in chronic CA (5 months to years after onset). CD84 was localized to inflammatory cells in KD tissues. Genes associated with cellular proliferation, motility and survival were also up-regulated in KD CA, and immune activation molecules MX2 and SP140 were up-regulated in chronic KD. CD84, which facilitates immune responses and stabilizes platelet aggregates, is markedly up-regulated in KD CA in patients with acute and chronic arterial disease. We provide the first molecular evidence of dysregulated inflammatory responses persisting for months to years in CA significantly damaged by KD.

The "myofibroblast" that is omnipresent in pathology and key to the EMT concepts does not actually exist, since normal fibroblasts contain stress fibril organelles (SMA bundles with dense bodies) variably detected by TEM and IHC: conclusions by a diagnostic pathologist with decades of ultrastructural experience

The so-called "enigmatic" unique "myofibroblast" has been erroneously substituted for virtually all things fibroblastic in soft tissue pathology and believed to be the ultimate fibrogenic cell. It is also internationally considered to be the mesenchymal cell in un-proven post-natal EMT, EMT organ/tissue fibrosis, and the assumption that EMT/MET is key to carcinoma/adenocarcinoma invasion and metastasis. However, no such cell exists, having been mistaken for our normal ubiquitous fibrogenic fibroblasts that contain peripheral bundles of actin (SMA) with dense bodies, i.e. stress fibril (SF) organelles variably detectable by TEM and SMA IHC, depending on the degree of activation. The only detectable features distinguishing what are erroneously believed to be two unique fibrogenic spindle cells are the SF. Is the variable detection of SF/SMA in fibroblastic and non-fibroblastic lesions significant? Carcinosarcomas are not bi-phasic malignancies or proof of EMT/MET. What does it mean that the fibroblasts of so-called "carcinoma-associated fibroblasts (CAF)" are not "myofibroblasts"? The true myofibroblast is the ultrastructurally and functionally unique, terminally-differentiated, pathognomonic cell of physiologic wound-healing, which unfortunately has been confused with the activated fibroblast. This study fails to demonstrate any ultrastructural evidence that either normal epithelial (EMT) or carcinoma/adenocarcinoma cells can undergo reversible transition into mesenchymal cells (EMT/MET) under any circumstances. The SF/SMA-positive fibrogenic cell in organ/tissue fibrosis is the genetically up-regulated, activated fibroblast, which has no relationship to EMT. Are any of the innumerable biochemical factors/elements considered to be associated with this non-existent cell and its related processes related to the activated fibroblast? The conclusions are based on review of every electron micrograph taken during a 40-year career in diagnostic and research ultrastructural pathology, and by confirming that the published TEM figures of so-called "myofibroblasts", are actually of fibroblasts.

Fatal Pulmonary Microsporidiosis Due toEncephalitozoon cuniculiFollowing Allogeneic Bone Marrow Transplantation for Acute Myelogenous Leukemia

Microsporidia are ubiquitous obligate eukaryotic intracellular parasites that are now felt to be more akin to degenerate fungi than to protozoa. Microsporidia can be highly pathogenic, causing a broad range of symptoms in humans, especially individuals who are immunocompromised. The vast majority of human cases of microsporidiosis have been reported during the past 20 years, in patients with HIV/AIDS, while only relatively rare cases have been described in immunocompetent individuals. However, microsporidia infections are being increasingly reported in patients following solid-organ transplanation, where the main symptom has been diarrhea. The authors report the first case of pulmonary microsporidial infection in an allogeneic bone marrow transplant recipient in the United States and only the second case in the world. The patient, with a history of Hodgkin disease followed by acute myelogenous leukemia received a T-cell-depleted graft, but succumbed to respiratory failure 63 days post transplantation. An open lung biopsy, taken just before death, was originally thought to show toxoplasmosis. The correct diagnosis of microsporidiosis was made postmortem by light and electron microscopy. DNA polymerase chain reaction analysis confirmed the diagnosis and furthermore revealed it to be the dog strain of the microsporidia species Encephalitozoon cuniculi. Although to date rarely diagnosed, microsporidial infection should also be considered in the differential diagnosis of, e.g., unexplained pulmonary infection in bone marrow transplant patients.

Replication of HIV-1 in Vivo and in Vitro

A complex relationship exists between HIV and its cellular targets. The lethal effect of HIV on circulating CD4(+) helper T lymphocytes parallels the degree of the infected individual's immunodeficiency and ultimately the transition to AIDS and death. However, as with other members of the Lentivirus family of retroviruses, the ubiquitous, mobile macrophage is also a prime target for HIV infection, and apparently, in most instances, is the initial infected cell, since most people are infected with a CCR5 chemokine-tropic virus. Unlike the lymphocyte, the macrophage is apparently a more stable viral host, capable of a long infected life as an HIV reservoir and a chronic source of infectious virus. Published in vitro studies have indicated that whereas lymphocytes replicate HIV solely on their plasma membrane, macrophages have been envisaged to predominantly replicate HIV within cytoplasmic vacuoles, and thus have been likened to a "Trojan horse," when it comes to the immune system. Recent studies have revealed an ingenious way by which the cultured monocyte-derived macrophage (MDM) replicates HIV and releases it into the medium. The key macrophage organelle appears to be what is alternatively referred to as the "late endosome" (LE) or the "multivesicular body" (MVB), which have a short and a long history, respectively. Proof of the association is that chemically, LE/MVB and their vesicles possess several pathopneumonic membrane markers (e.g., CD63) that are found on released HIV particles. The hypothesis is that HIV usurps this vesicle-forming mechanism and employs it for its own replication. Release of the intravacuolar virus from the cell is hypothesized to occur by a process referred to as exocytosis, resulting from the fusion of virus-laden LE/MVB with the plasma membrane of the macrophage. Interestingly, LE/MVB are also involved in the infection stage of MDM by HIV. Close review of the literature reveals that along with the Golgi, which contributes to the formation of LE/MVB, the MVB was first identified as a site of HIV replication by macrophages many years ago, but the full implication of this observation was not appreciated at the time. As in many other areas of HIV research, what has been totally lacking is an in vivo confirmation of the in vitro phenomenon. Herein, the ultrastructure of HIV interaction with cells in vitro and in vivo is explored. It is shown that while HIV is regularly found in LE/MVB in vitro, it is infrequently the case in vivo. Therefore, the results challenge the "Trojan horse" concept.

Ultrastructure of Kaposi sarcoma

Kaposi sarcoma (KS) is a complex disease with aspects of virology (human herpesvirus-8, HHV-8, and human immunodeficiency virus, HIV), immunology (immunodeficiency), hyperplasia (multiple widely spaced de novo lesions), and neoplasia (metastases) that has always been the most common AIDS-defining malignancy. The lesional spindle cell has been classified as being derived from either blood vascular or, more recently, lymphatic endothelial cell origin. This study revealed a spectrum of endothelial cell ultrastructure from lymphatic to blood vascular. It demonstrated frequent Weibel-Palade bodies and gap junctions. The spindle cells were shown to behave as facultative phagocytes, internalizing and processing necrotic cells and leaked red blood cells (RBCs). Fragmented RBCs were equivalent to the "hyaline droplets" seen by light microscopy. The final stages of RBC disintegration were hemosiderin and ferritin. Most significantly, this study disclosed that KS is actually composed of a single type of randomly oriented spindle cell forming vessels of varying size and integrity.

Hyperplastic lymphoid tissue in HIV/AIDS: an electron microscopic study

The purpose of this study was to characterize the ultrastructure of lymphoid tissue from HIV/AIDS patients and to evaluate it as a reservoir and source of HIV. HIV has been demonstrated in lymph nodes and tonsils and adenoids, by immunohistochemistry (IHC), in situ hybridization (ISH), and transmission electron microscopy (TEM), to be associated with germinal center (GC) follicular dendritic cells (FDC). The presence of HIV in the larger gastrointestinal tract-associated lymphoid tissue (GALT) has been much less studied. Whether FDC themselves are productively infected by HIV in any of the lymphoid sites is controversial. Lymph nodes, tonsils, and gastrointestinal biopsies were fixed in neutral buffered glutaraldehyde and prepared for TEM. Mature HIV particles were abundant in GC of hyperplastic lymph nodes, tonsils, and the GALT. They were enmeshed within an electron-dense matrix associated with an all-encompassing branching FDC network of processes. HIV particles were seen budding from both FDC and lymphocytes. The greatest numbers of particles were seen in hyperplastic lymphoid tissue from untreated individuals and in lymph nodes co-infected with opportunistic organisms, such as Mycobacterium avium complex. In addition to HIV, unidentifiable "particles" of varying sizes, possibly including other viruses, were regularly seen in association with FDC. Ultrastructural study graphically demonstrated the abundance of HIV particles associated with the complex FDC network of hyperplastic lymph nodes, tonsils, and GALT. HIV was shown to productively infect FDC, as well as lymphocytes.

Processing tissue and cells for transmission electron microscopy in diagnostic pathology and research

In transmission electron microscopy (TEM), electrons are transmitted through a plastic-embedded specimen, and an image is formed. TEM enables the resolution and visualization of detail not apparent via light microscopy, even when combined with immunohistochemical analysis. Ultrastructural examination of tissues, cells and microorganisms plays a vital role in diagnostic pathology and biologic research. TEM is used to study the morphology of cells and their organelles, and in the identification and characterization of viruses, bacteria, protozoa and fungi. In this protocol, we present a TEM method for preparing specimens obtained in clinical or research settings, discussing the particular requirements for tissue and cell preparation and analysis, the need for rapid fixation and the possibility of analysis of tissue already fixed in formalin or processed into paraffin blocks. Details of fixation, embedding and how to prepare thin and semi-thin sections, which can be used for analysis complementary to that performed ultimately using TEM, are also described.

Nitric oxide in experimental joint inflammation. Benefit or detriment?

The host response to infection or injury initiates a cascade of events involving recruitment of leukocytes and the release of multiple inflammatory mediators. One of these mediators, nitric oxide (NO), not only represents an important microbicidal agent in host defense, but also functions as a biological signaling and effector molecule in inflammation and immunity. However, overproduction of NO can be autotoxic and contribute to tissue damage and has been implicated in pathogenesis of tumors, and infectious, autoimmune and chronic degenerative diseases. NO is generated via constitutive and inducible nitric oxide synthases (iNOS) which catalyze the oxidation of a guanidino nitrogen associated with L-arginine. Whereas endothelial NOS (eNOS) and neuronal NOS (nNOS) are constitutively expressed, iNOS is transcriptionally induced by bacterial constituents and inflammatory mediators, including TNF alpha and IL-1. In an experimental model of bacterial component-induced joint inflammation and tissue degradation, functionally distinct roles of the constitutive NOS and iNOS were demonstrated. Following systemic delivery of an arthritogenic dose of streptococcal cell walls (SCW), these bacterial peptidoglycan-polysaccharide complexes disseminate and target the peripheral joints, liver and spleen of the treated animals. Following deposition of the SCW in the peripheral joints, an initial innate inflammatory response to the bacterial components progresses into an adaptive immune response with the recruitment and activation of mononuclear phagocytes and T lymphocytes. With the release of cytokines and inflammatory mediators, there is an upregulation of gene expression for iNOS, but not the constitutive nNOS or eNOS. Nonetheless, the constitutive NOS isoforms, regulated by calcium fluxes and interaction with calmodulin, may also enhance NO production. Increased release of NO was detected not only in the synovium, but also in the circulation, and plasma levels of nitrate plus nitrite, the stable products of NO reactions, correlated with disease progression. Following inhibition of NO production with nonspecific NOS inhibitors, such as N(G)-monomethyl-L-arginine, which target all three isoforms, there is a striking therapeutic benefit with reduced signs and symptoms of erosive arthritis. In contrast, selective targeting of iNOS with N-iminoethyl-L-lysine resulted in exacerbation of the synovial inflammation and degradation of joint structures. Based on these data, it appears that the constitutive isoforms of NOS contribute to the pathophysiology of the arthropathy, and that induced NOS and NO may function, in part, in a protective pathway. Moreover, the suppression of NO following treatment with TNF alpha antagonists results in reduced inflammation and the associated synovial pathology. Collectively, these data implicate discrete roles for the NOS isoforms in the emergence of local tissue pathology and underscore the need to define the specific pathways that are being targeted for interventional strategies.

Pulmonary infection with microsporidia after allogeneic bone marrow transplantation

Microsporidia are obligate, intracellular protozoal parasites that can be pathogenic in immunocompromised individuals. The majority of cases of microsporidiosis have been documented in patients with HIV, and only a few case reports exist of infection in solid organ transplant patients. We report the first case of pulmonary microsporidial infection in an allogeneic bone marrow transplant recipient in the US. The patient was a recipient of a T-cell-depleted graft who succumbed to complications from respiratory failure 63 days post transplant. The diagnosis was made post mortem by electron microscopy and confirmed with PCR. Although rare, microsporidial infection should be considered in the differential diagnosis of unexplained pulmonary infection in bone marrow transplant patients.

PA-457: a potent HIV inhibitor that disrupts core condensation by targeting a late step in Gag processing

New HIV therapies are urgently needed to address the growing problem of drug resistance. In this article, we characterize the anti-HIV drug candidate 3-O-(3',3'-dimethylsuccinyl) betulinic acid (PA-457). We show that PA-457 potently inhibits replication of both WT and drug-resistant HIV-1 isolates and demonstrate that the compound acts by disrupting a late step in Gag processing involving conversion of the capsid precursor (p25) to mature capsid protein (p24). We find that virions from PA-457-treated cultures are noninfectious and exhibit an aberrant particle morphology characterized by a spherical, acentric core and a crescent-shaped, electron-dense shell lying just inside the viral membrane. To identify the determinants of compound activity we selected for PA-457-resistant virus in vitro. Consistent with the effect on Gag processing, we found that mutations conferring resistance to PA-457 map to the p25 to p24 cleavage site. PA-457 represents a unique class of anti-HIV compounds termed maturation inhibitors that exploit a previously unidentified viral target, providing additional opportunities for HIV drug discovery.

Ultrastructure of HIV/AIDS

Transmission electron microscopy has played a key role in our understanding of the human immunodeficiency virus and the opportunistic infections that accompany HIV disease. This paper describes features of HIV production; HHV-8, the virus that is associated with Kaposi sarcoma; Trachipleistophora anthropophthera, a new disseminating microsporidian; and bacterial enteritis, which causes diarrhea in patients with AIDS.

The macrophage in HIV infection

Macrophages play a key role in several critical aspects of HIV disease. They appear to be the first cells infected by HIV and perhaps the very source of HIV production when CD4+ cells are markedly depleted in the patient. Macrophages and microglial cells are the cells infected by HIV in the CNS. In tonsils and adenoids of HIV-infected patients, macrophages fuse into multinucleated giant cells that produce copious amounts of virus. Finally, opportunistic pathogens can cause an upregulation of HIV production by macrophages, often in the multinucleated form.

Intestinal macrophages lack CD14 and CD89 and consequently are down-regulated for LPS- and IgA-mediated activities

The intestinal mucosa normally displays minimal inflammation despite the close proximity between mucosal macrophages and lumenal bacteria. Macrophages interact with bacteria and their products through CD14, a surface receptor involved in the response to LPS, and CD89, the receptor for IgA (FcalphaR). Here we show that resident macrophages isolated from normal human intestine lack CD14 and CD89. The absence of CD14 and CD89 was not due to the isolation procedure or mucosal cell products, but was evident at the transcriptional level, as the macrophages expressed neither CD14- nor CD89-specific mRNAs, but did express Toll-like receptor 2 and 4 transcripts. Consistent with their CD14(-) phenotype, lamina propria macrophages displayed markedly reduced LPS-induced cytokine production and LPS-enhanced phagocytosis. In addition, IgA-enhanced phagocytosis was sharply reduced in lamina propria macrophages. Thus, the absence of CD14 and CD89 on resident intestinal macrophages, due to down-regulated gene transcription, causes down-modulated LPS- and IgA-mediated functions and probably contributes to the low level of inflammation in normal human intestinal mucosa.

Expression and immunogenicity of human immunodeficiency virus type 1 Gag expressed by a replication-competent rhabdovirus-based vaccine vector

A replication-competent rhabdovirus-based vector expressing human immunodeficiency virus type 1 (HIV-1) Gag protein was characterized on human cell lines and analyzed for the induction of a cellular immune response in mice. We previously described a rabies virus (RV) vaccine strain-based vector expressing HIV-1 gp160. The recombinant RV was able to induce strong humoral and cellular immune responses against the HIV-1 envelope protein in mice (M. J. Schnell et al., Proc. Natl. Acad. Sci. USA 97:3544-3549, 2000; J. P. McGettigan et al., J. Virol. 75:4430-4434, 2001). Recent research suggests that the HIV-1 Gag protein is another important target for cell-mediated host immune defense. Here we show that HIV-1 Gag can efficiently be expressed by RV on both human and nonhuman cell lines. Infection of HeLa cells with recombinant RV expressing HIV-1 Gag resulted in efficient expression of HIV-1 precursor protein p55 as indicated by both immunostaining and Western blotting. Moreover, HIV-1 p24 antigen capture enzyme-linked immunosorbent assay and electron microscopy showed efficient release of HIV-1 virus-like particles in addition to bullet-shaped RV particles in the supernatants of the infected cells. To initially screen the immunogenicity of this new vaccine vector, BALB/c mice received a single vaccination with the recombinant RV expressing HIV-1 Gag. Immunized mice developed a vigorous CD8(+) cytotoxic T-lymphocyte response against HIV-1 Gag. In addition, 26.8% of CD8(+) T cells from mice immunized with RV expressing HIV-1 Gag produced gamma interferon after challenge with a recombinant vaccinia virus expressing HIV-1 Gag. These results further confirm and extend the potency of RV-based vectors as a potential HIV-1 vaccine.

HIV-1 induces phenotypic and functional perturbations of B cells in chronically infected individuals

A number of perturbations of B cells has been described in the setting of HIV infection; however, most remain poorly understood. To directly address the effect of HIV replication on B cell function, we investigated the capacity of B cells isolated from HIV-infected patients to respond to a variety of stimuli before and after reduction of viremia by effective antiretroviral therapy. B cells taken from patients with high levels of plasma viremia were defective in their proliferative responses to various stimuli. Viremia was also associated with the appearance of a subpopulation of B cells that expressed reduced levels of CD21. After fractionation into CD21(high)- and CD21(low)-expressing B cells, the CD21(low) fraction showed dramatically reduced proliferation in response to B cell stimuli and enhanced secretion of immunoglobulins when compared with the CD21(high) fraction. Electron microscopic analysis of each fraction revealed cells with plasmacytoid features in the CD21(low) B cell population but not in the CD21(high) fraction. These results indicate that HIV viremia induces the appearance of a subset of B cells whose function is impaired and which may be responsible for the hypergammaglobulinemia associated with HIV disease.

The histopathology of 103 consecutive colonoscopy biopsies from 82 symptomatic patients with acquired immunodeficiency syndrome: original and look-back diagnoses

OBJECTIVE

To compare the primary diagnoses assigned by general surgical pathologists on a series of 103 consecutive colon biopsies from individuals infected with human immunodeficiency virus (HIV) with diagnoses rendered by a pathologist with extensive experience in gastrointestinal pathology in HIV/acquired immunodeficiency syndrome.

DESIGN

New sections were cut from paraffin blocks of 103 consecutive colon biopsies taken during colonoscopies of 82 different HIV-infected patients; all new sections were stained with hematoxylin-eosin. These individuals either had negative stool studies or had failed to respond to therapy and had chronic large bowel symptoms, such as frequent small volume-type diarrhea, tenesmus, and/or bright red blood per rectum. Immunohistochemistry for cytomegalovirus (CMV) was performed on 18 of 22 specimens originally diagnosed with CMV colitis.

RESULTS

The initial study yielded 70 (68%) negative or nonspecific diagnoses, 22 (21%) cases of CMV colitis, 5 (5%) Cryptosporidium diagnoses, 2 cases each of adenomatous polyps and Kaposi sarcoma, and 1 case each of spirochetosis and squamous cell carcinoma of the anorectum. Review of the recuts yielded 64 (62%) negative or nonspecific diagnoses, 12 (12%) new adenovirus infections (3 combined with CMV), and 11 (11%) lone CMV infections. Three attaching and effacing bacterial infections were diagnosed, 1 with adenovirus coinfection. A total of 4 spirochetosis cases were found on review. Seven (7%) of the biopsies showed at least 1 coinfection. Nine biopsies had features suggestive of inflammatory bowel disease.

CONCLUSIONS

Colonoscopy with biopsy after negative stool studies or failure to respond to therapy yielded a high proportion of negative or nonspecific diagnoses. Adenovirus and enteropathogenic bacterial infections had been totally overlooked on initial examination. It takes particular experience to evaluate gastrointestinal biopsies from HIV-infected patients.

Targeted inhibition of calcineurin signaling blocks calcium-dependent reactivation of Kaposi sarcoma-associated herpesvirus

Kaposi sarcoma-associated herpesvirus (KSHV) is associated with KS, primary effusion lymphoma (PEL), and multicentric Castleman disease. Reactivation of KSHV in latently infected cells and subsequent plasma viremia occur before the development of KS. Intracellular signaling pathways involved in KSHV reactivation were studied. In latently infected PEL cells (BCBL-1), KSHV reactivation in single cells was determined by quantitative flow cytometry. Viral particle production was determined by electron microscope analyses and detection of minor capsid protein in culture supernatants. Agents that mobilized intracellular calcium (ionomycin, thapsigargin) induced expression of KSHV lytic cycle-associated proteins and led to increased virus production. Calcium-mediated virus reactivation was blocked by specific inhibitors of calcineurin-dependent signal transduction (cyclosporine, FK506). Similarly, calcium-mediated virus reactivation in KSHV-infected dermal microvascular endothelial cells was blocked by cyclosporine. Furthermore, retroviral transduction with plasmid DNA encoding VIVIT, a peptide specifically blocking calcineurin-NFAT interactions, inhibited calcium-dependent KSHV reactivation. By contrast, chemical induction of lytic-phase infection by the phorbol ester 12-O-tetradecanoyl-phorbol-13-acetate was blocked by protein kinase C inhibitors, but not by calcineurin inhibitors. In summary, calcineurin-dependent signal transduction, an important signaling cascade in vivo, induces calcium-dependent KSHV replication, providing a possible target for the design of antiherpesvirus strategies in KSHV-infected patients.

Low levels of productive HIV infection in Langerhans cell-like dendritic cells differentiated in the presence of TGF-beta1 and increased viral replication with CD40 ligand-induced maturation

Langerhans cells (LC) represent dendritic cells (DC) within mucosal epithelium that are purported initial targets for HIV following sexual exposure to virus. Here, morphologic, phenotypic, functional and HIV infection experiments were performed using monocyte-derived DC cultured in the presence of GM-CSF, IL-4 and TGF-beta1 (G4T-DC), GM-CSF and IL-4 (G4-DC), and G4T-DC incubated for an additional 3 days with CD40 ligand (CD40L-DC). G4T-DC, which demonstrated characteristics of immature LC, could be productively infected by either R5- or X4-HIV strains. Infection levels, however, were markedly lower than those observed in immature G4-DC. Surprisingly, CD40L-DC, which demonstrated features of mature LC, could be productively infected with HIV at higher levels than immature G4T-DC. Productive HIV infection in these three DC populations correlated positively with cell surface expression of CD4, CCR5 and CXCR4. We suggest that low levels of HIV infection in LC-like G4T-DC indicate an inefficient mechanism by which HIV can initially infect individuals, perhaps explaining the relative difficulty in becoming infected during sexual exposure to virus. In addition, enhanced HIV infection in LC-like G4T-DC following CD40L treatment suggests a mechanism by which inflammatory CD40L(+) T cells, if present in mucosal tissue, could lead to increased HIV transmission rates.

Candidate microbicides block HIV-1 infection of human immature Langerhans cells within epithelial tissue explants

Initial biologic events that underlie sexual transmission of HIV-1 are poorly understood. To model these events, we exposed human immature Langerhans cells (LCs) within epithelial tissue explants to two primary and two laboratory-adapted HIV-1 isolates. We detected HIV-1(Ba-L) infection in single LCs that spontaneously emigrated from explants by flow cytometry (median of infected LCs = 0.52%, range = 0.08-4.77%). HIV-1-infected LCs downregulated surface CD4 and CD83, whereas MHC class II, CD80, and CD86 were unchanged. For all HIV-1 strains tested, emigrated LCs were critical in establishing high levels of infection (0.1-1 microg HIV-1 p24 per milliliter) in cocultured autologous or allogeneic T cells. HIV-1(Ba-L) (an R5 HIV-1 strain) more efficiently infected LC-T cell cocultures when compared with HIV-1(IIIB) (an X4 HIV-1 strain). Interestingly, pretreatment of explants with either aminooxypentane-RANTES (regulated upon activation, normal T cell expressed and secreted) or cellulose acetate phthalate (potential microbicides) blocked HIV-1 infection of LCs and subsequent T cell infection in a dose-dependent manner. In summary, we document HIV-1 infection in single LCs after exposure to virus within epithelial tissue, demonstrate that relatively low numbers of these cells are capable of inducing high levels of infection in cocultured T cells, and provide a useful explant model for testing of agents designed to block sexual transmission of HIV-1.

Morphogenesis of HHV8 in primary human dermal microvascular endothelium and primary effusion lymphomas

This study elucidates the morphology of HHV8 replication in human dermal endothelial cells and primary effusion lymphomas (PEL) and compares it to that seen in Kaposi sarcoma. Primary human dermal microvascular endothelial cells (DMVEC) exposed to the cell-filtered supernatant of the PEL JSC1 and PEL cell lines (KS-1, BCBL-1, BC-1, BC-3) were cultured in the presence or absence of 12-O-tetradecanoyl-phorbol-13-acetate (TPA) or butyrate. Cells were fixed in neutral-buffered glutaraldehyde, gelled in cooled agar, and processed for TEM. There was a quantitative, but not a qualitative difference in viral expression associated with no treatment or exposure to TPA or butyrate of H HV8 in DMVEC and PEL. Two types of viral-induced intranuclear inclusions (INI) were visible at the light and ultrastructural levels. The more common INI had lighter staining material filling the nucleus, except for a rim of dense chromatin, and could be seen even before viral nucleocapsids (NC) were visible. The second type of INI resembled a target formed by condensation of electron-dense material surrounded by a lighter halo and marginated heterochromatin and containing NC. Collections of coalescing electron-dense granules resembling starbursts were often present in nuclei containing either type of INI. Next to appear in productively infected cells were mature enveloped particles that formed mostly by the budding of NC into cytoplasmic vacuoles. Mature particles were also seen free on the plasma membrane. Tufts of electron-dense intermediate filaments were associated with maturing particles. Mature virions lacked an electron-dense tegument. Viral production was ultimately associated with cell lysis. It appears that HHV8 propagate in DMVEC, with and without stimulation, and have a similar morphogenesis to that seen in PEL cell lines and Kaposi sarcoma lesions. Several unique features characterize cells productively infected by HHV8.

Permissive factors for HIV-1 infection of macrophages

Immunodeficiency, the consequence of HIV-1 infection, predisposes the host to opportunistic infections. In turn, opportunistic pathogens influence target cell susceptibility to HIV-1 infection and replication. Although the advent of highly active antiretroviral therapy (HAART) has altered these sequelae, co-infections may prevail in some parts of the world and in failed HAART regimens. Moreover, immune activation as occurs in tonsil and non-infectious mucosal inflammatory lesions may also be associated with proximal sites of viral replication. These connections between enhancement of HIV-1 infection and activation/inflammation warrant further elucidation of the factors promoting permissiveness to HIV-1 infection. Using the opportunistic pathogen Mycobacterium avium as an in vitro model, we demonstrated that co-infection facilitated HIV-1 infection of monocyte-macrophages by multiple pathways. M. avium activated NF-kappaB, the downstream consequences of which included augmented expression of tumor necrosis factor alpha and CCR5 receptors, both permissive for sustaining HIV-1 infection. Pronounced viral replication in lymph nodes co-infected with M. avium and HIV-1 paralleled these in vitro findings. Furthermore, reduction in viral burden is associated with treatment of infected or inflamed tissues, underscoring the link between immune activation and viral replication.

Rapid activation of lymph nodes and mononuclear cell HIV expression upon interrupting highly active antiretroviral therapy in patients after prolonged viral suppression

OBJECTIVE

To compare the architecture and HIV-1 RNA and Gag p24 protein expression in lymph nodes (LN) excised from individuals during chronic highly active antiretroviral therapy (HAART) with LN removed from the same patient after plasma virus rebound following the interruption of HAART.

MATERIALS AND METHODS

Six HIV-1-infected patients on HAART, with CD4 cell counts greater than 350 cells/microl, and plasma HIV-1 RNA less than 50 copies/ml, underwent inguinal LN excision upon discontinuation of HAART, and again after rebound of plasma virus. Lymph nodes were evaluated by immunohistochemical staining for Gag p24 antigen and Ki67, in-situ hybridization for HIV-1 RNA and H3-histone, and transmission electron microscopy (TEM).

RESULTS

LN at baseline were quiescent to mildly hyperplastic and generally contained more primary than secondary follicles. Only one LN had detectable follicular dendritic cell (FDC)-associated p24 antigen, none had HIV RNA. Few mononuclear cells (MNC) expressed RNA or p24 antigen. Plasma virus at the second biopsy ranged from 329 to 3.2 x 10(6) copies/ml. CD4 cell count decline ranged from 5 to 51% during drug hiatus, and was greatest in patients with highest viral rebound. Four of six of the second LN were more hyperplastic than the initial LN, two showed paracortical hyperplasia. MNC expression of HIV RNA in the second LN paralleled the level of plasma viremia. Increased Ki67 and H3-histone signal occurred in the second LN.

CONCLUSION

Quiescent LN from individuals on HAART rapidly become hyperplastic and activated within 1-2 months after treatment interruption. As in acute HIV infection, virus expression by LN MNC parallels the rebound in plasma viremia and fall in CD4 cell count.

In vivo cytolysis and fusion of human immunodeficiency virus type 1-infected lymphocytes in lymphoid tissue

Lymphoid tissue was examined to see whether in vivo cytopathic effects of human immunodeficiency virus (HIV) infection on lymphocytes could be detected. Transmission electron microscopy of mechanical suspensions prepared from lymph nodes showed both replication and phagocytosis of HIV particles by macrophages. Phagosomes contained cellular debris and virions, some of which were undergoing digestion. Neutrophils also contained HIV particles intermixed with cellular debris in phagosomes. Immunohistochemistry revealed whole Gag p24-positive lymphocytes and p24-positive cellular debris within the cytoplasm of paracortical macrophages. Lysing p24-positive lymphocytes were also seen. In the paracortex, p24-positive multinucleated lymphocytes with up to 5 nuclei were seen. In situ hybridization for HIV RNA in combination with immunohistochemistry for HAM56, a macrophage-specific marker, revealed colabeled cells. Thus, HIV-positive lymphocytes undergo lysis in lymphoid tissue. The cellular debris is phagocytized by macrophages, which themselves can replicate HIV. HIV-positive lymphocytes fuse in lymph nodes to form multinucleated cells.

Apoptosis and P53 induction in human lung fibroblasts exposed to chromium (VI): effect of ascorbate and tocopherol

Some forms of hexavalent chromium [Cr(VI)] are known to cause damage to respiratory tract tissue, and are thought to be human lung carcinogens. Because Cr(VI) is mutagenic and carcinogenic at doses that evoke cell toxicity, the objective of these experiments was to examine the effect of Cr(VI) on the growth, survival, and mode of cell death in normal human lung fibroblasts (HLF cells). DNA adduct formation was monitored as a marker for bioavailability of genotoxic chromium. We also examined the modulation of these endpoints by vitamins C and E. Long-term Cr(VI) exposures were employed, which decreased clonogenic cell survival by 25% to 95% in a dose-dependent manner. The predominant cellular response to Cr(VI) was growth arrest. We found that Cr(VI) caused up to 20% of HLF cells to undergo apoptosis, and documented apoptotic morphology and the phagocytosis of apoptotic bodies by neighboring cells. P53 levels increased 4- to 6-fold in chromium-treated cells. In contrast with previous studies using CHO cells, the present study using HLFs found that pretreatment with either vitamin C or E did not exhibit a significant effect on Cr-induced apoptosis or clonogenic survival. In addition, pretreatment with vitamin C did not affect the p53 induction observed after chromium treatment. Neither vitamin had any effect on Cr-DNA adduct formation. These data indicate that although pretreatment with vitamin C or E alters the spectrum of cellular and/or genetic lesions induced by chromium(VI), neither vitamin altered the initiation or progression of apoptosis in diploid human lung cells.

Evaluation of lymph node virus burden in human immunodeficiency virus-infected patients receiving efavirenz-based protease inhibitor--sparing highly active antiretroviral therapy

Although efavirenz-containing regimens effectively suppress plasma levels of human immunodeficiency virus (HIV) RNA, it is now clear that undetectable plasma viremia may not reflect a lack of viral replication. Because lymphoid tissue is an active site of HIV replication, the lymph node virus burden was analyzed in persons who received highly active antiretroviral therapy (HAART) containing either efavirenz or a protease inhibitor (PI). Testing with in situ hybridization revealed no detectable follicular dendritic cell-associated HIV RNA in either group, and only 2 of 8 persons in the efavirenz group and 1 of 4 in the PI group had detectable RNA in lymph node mononuclear cells (LNMC) when tested by use of nucleic acid sequencebased amplification. Low levels of replication-competent HIV were identified in both groups by use of quantitative coculture assays. There was no evidence of development of resistance to either regimen in virus isolated from LNMC. These data support the use of efavirenz as an alternative to a PI in initial HAART regimens.

Isn't a picture still worth a thousand words?

The transmission electron microscope is a valuable diagnostic and research tool that is presently under-appreciated. In the area of human immunodeficiency virus research alone, it has provided critical information about viral pathogenesis and opportunistic infections and malignancies. However, because it has not always been used with care, the literature contains misinterpretations, especially as to what is a virus and what is actually a cell organelle, e.g., lysosome and Golgi vesicles. It is important to review the subject periodically to maintain its quality.

TGF-beta influences the life and death decisions of T lymphocytes

TGF-beta is a powerful mediator of immune cell phenotype and function. In TGF-beta1 homozygous null mice, aberrant regulation of the immune response culminates in lethal cardiopulmonary inflammation. In dissecting the underlying mechanisms leading to the attack of self, a role for TGF-beta1 in controlling apoptosis and T cell selection patterns was uncovered. Increased levels of apoptosis and TCR mediated cell death disrupted normal negative and positive T cell selection in the thymus. Moreover, in peripheral T cell populations, increased T lymphocyte death was associated with increased expression of apoptosis-inducing receptors. Persistent activation of T cells engendered unchecked apoptosis which, rather than reducing, further exacerbated, tissue inflammation due to the absence of TGF-beta1. TGF-beta, normally generated by macrophages during clearance of apoptotic cells contributes to dampening of inflammatory sequelae associated with phagocytosis. Collectively, these data demonstrate a pivotal role for TGF-beta in multiple stages of T cell apoptosis, selection, activation and clearance.

Role of the Gag matrix domain in targeting human immunodeficiency virus type 1 assembly

Human immunodeficiency virus type 1 (HIV-1) particle formation and the subsequent initiation of protease-mediated maturation occur predominantly on the plasma membrane. However, the mechanism by which HIV-1 assembly is targeted specifically to the plasma membrane versus intracellular membranes is largely unknown. Previously, we observed that mutations between residues 84 and 88 of the matrix (MA) domain of HIV-1 Gag cause a retargeting of virus particle formation to an intracellular site. In this study, we demonstrate that the mutant virus assembly occurs in the Golgi or in post-Golgi vesicles. These particles undergo core condensation in a protease-dependent manner, indicating that virus maturation can occur not only on the plasma membrane but also in the Golgi or post-Golgi vesicles. The intracellular assembly of mutant particles is dependent on Gag myristylation but is not influenced by p6(Gag) or envelope glycoprotein expression. Previous characterization of viral revertants suggested a functional relationship between the highly basic domain of MA (amino acids 17 to 31) and residues 84 to 88. We now demonstrate that mutations in the highly basic domain also retarget virus particle formation to the Golgi or post-Golgi vesicles. Although the basic domain has been implicated in Gag membrane binding, no correlation was observed between the impact of mutations on membrane binding and Gag targeting, indicating that these two functions of MA are genetically separable. Plasma membrane targeting of Gag proteins with mutations in either the basic domain or between residues 84 and 88 was rescued by coexpression with wild-type Gag; however, the two groups of MA mutants could not rescue each other. We propose that the highly basic domain of MA contains a major determinant of HIV-1 Gag plasma membrane targeting and that mutations between residues 84 and 88 disrupt plasma membrane targeting through an effect on the basic domain.

Human endogenous retroviral expression by leukocytes

Budding endogenous retroviral particles were identified on the plasma membrane of a high percentage of neurotrophils in four widely varied pathological specimens.

Internalization of carcinogenic lead chromate particles by cultured normal human lung epithelial cells: formation of intracellular lead-inclusion bodies and induction of apoptosis

Occupational exposure to certain particulate hexavalent chromium [Cr(VI)] compounds, such as lead chromate, has been associated with lung cancer and respiratory tract toxicity. We have previously shown that apoptosis is a major mode of death in cultured rodent cells treated with soluble sodium chromate and particulate lead chromate. Here we report the cellular and molecular effects of lead chromate and sodium chromate in normal human lung small airway epithelial (HSAE) cells, which may be one of the targets for Cr(VI)-induced lung cancer and respiratory tract toxicity. Phagocytosed lead chromate particles and intracellular lead-inclusion bodies (LIB) were observed by transmission electron microscopy and confirmed by X-ray analysis. HSAE cells exposed to lead chromate and sodium chromate underwent dose-dependent apoptosis. The cellular uptake and genomic interactions of both Cr and lead (Pb) were examined by inductively coupled plasma mass spectrometry (ICPMS) coupled with a novel, direct-injection high-efficiency nebulizer (DIHEN). Using this approach, we have quantitated a dose-dependent formation of Cr-DNA adducts and DNA-associated Pb in lead chromate-treated HSAE cells. The formation of LIB in normal human lung cells exposed to lead chromate indicates that ionic Pb is released from the particles and thus might contribute to the cell toxicity caused by lead chromate. Internalization and dissolution of lead chromate particles and the interaction of ionic Cr and Pb with DNA, may be components of the mechanism of lead chromate carcinogenesis. Lead chromate-induced apoptosis may be a mechanism to eliminate cells with chromium- and/or lead-damaged DNA.

Lymph node architecture preceding and following 6 months of potent antiviral therapy: follicular hyperplasia persists in parallel with p24 antigen restoration after involution and CD4 cell depletion in an AIDS patient

OBJECTIVES

To evaluate changes in architecture, viral RNA, and viral protein over 6 months in lymph nodes from retroviral-naïve HIV-infected persons before and after commencing highly active antiretroviral therapy (HAART).

METHODS

Nine antiretroviral-naïve HIV-infected persons had lymph nodes excised at baseline and at 2 and 6-8 months after beginning a four-drug combination regimen containing zidovudine, lamivudine, nevirapine, and indinavir. Two patients had AIDS. Lymph nodes were examined by immunohistochemical staining for Gag p24 HIV, CD3, CD21, CD20, HAM 56, and Ki67 antigens and by in-situ hybridization (ISH) for HIV RNA and H3-histone RNA.

RESULTS

Eight of nine baseline lymph nodes showed follicular hyperplasia and germinal center and paracortical mononuclear cell activation. At 2 months, the lymph nodes from seven patients, including the AIDS patients, showed more follicular hyperplasia and activation than their baseline specimens but with decreased mononuclear cell activation. By 6 months, seven lymph nodes were less hyperplastic and activated than their corresponding 2 month specimens. Combined ISH/immunohistochemical staining of baseline lymph nodes revealed productively infected T (CD3) and B (CD20) cells and macrophages (HAM56+). HIV RNA-positive mononuclear cells were infrequent at 2 months, and rare at 6 months. HIV RNA was still associated with follicular dendritic cells (FDC) at 2 months, but not at 6 months. HIV p24-positive antigen in germinal centers persisted through all 6, and the one 8 month specimens. The baseline lymph nodes from one of the AIDS patients was involuted and T cell depleted, whereas the follow-up lymph nodes were hyperplastic with normal T cell levels.

CONCLUSION

Follicular hyperplasia and cell activation, possibly caused by persistent viral protein in germinal centers, may help explain why HIV viremia rebounds so rapidly after the interruption of HAART. Restoration of architecture may follow the treatment of patients with AIDS who initially had involuted and CD4 cell-depleted lymph nodes.

Killing of Streptococcus pneumoniae by capsular polysaccharide-specific polymeric IgA, complement, and phagocytes

The role of IgA in the control of invasive mucosal pathogens such as Streptococcus pneumoniae is poorly understood. We demonstrate that human pneumococcal capsular polysaccharide-specific IgA initiated dose-dependent killing of S. pneumoniae with complement and phagocytes. The majority of specific IgA in serum was of the polymeric form (pIgA), and the efficiency of pIgA-initiated killing exceeded that of monomeric IgA-initiated killing. In the absence of complement, specific IgA induced minimal bacterial adherence, uptake, and killing. Killing of S. pneumoniae by resting phagocytes with immune IgA required complement, predominantly via the C2-independent alternative pathway, which requires factor B, but not calcium. Both S. pneumoniae-bound IgA and complement were involved, as demonstrated by a 50% decrease in killing with blocking of Fcalpha receptor (CD89) and CR1/CR3 (CD35/CD11b). However, IgA-mediated killing by phagocytes could be reproduced in the absence of opsonic complement by pre-activating phagocytes with the inflammatory products C5a and TNF-alpha. Thus, S. pneumoniae capsule-specific IgA may show distinct roles in effecting clearance of S. pneumoniae in the presence or absence of inflammation. These data suggest mechanisms whereby pIgA may serve to control pneumococcal infections locally and upon the pathogen's entry into the bloodstream.

Heterogeneity of viral IL-6 expression in HHV-8-associated diseases

In order to characterize the expression of the viral interleukin-6 (vIL-6) homologue in various human herpesvirus 8 (HHV-8)-associated diseases, in situ hybridization and immunohistochemistry were applied to formalin-fixed specimens. These assays showed consistent expression of vIL-6 in primary effusion lymphomas and in a case of human immunodeficiency virus (HIV)-associated lymphadenopathy with a Castleman's disease-like appearance. In contrast, Kaposi's sarcoma specimens showed marked differences among specimens. In a consecutive series of specimens from the Johns Hopkins archives, vIL-6 expression was demonstrated in one of 13 cases. However, among 7 specimens selected from the AIDS Malignancy Bank because of their high levels of the T1.1 lytic transcript and virion production, vIL-6 expression was consistently demonstrated in infiltrating mononuclear cells and occasional spindle-shaped cells. Thus vIL-6 expression in clinical specimens correlates with other measures of the lytic viral cycle. Both assays generally give congruent results and are consistent with the possibility that vIL-6 expression plays a role in the pathogenesis of a variety of HHV-8-associated diseases.

Comparison of genetic variability at multiple loci across the genomes of the major subtypes of Kaposi's sarcoma-associated herpesvirus reveals evidence for recombination and for two distinct types of open reading frame K15 alleles at the right-hand end

Kaposi's sarcoma (KS)-associated herpesvirus or human herpesvirus 8 (HHV8) DNA is found consistently in nearly all classical, endemic, transplant, and AIDS-associated KS lesions, as well as in several AIDS-associated lymphomas. We have previously sequenced the genes for the highly variable open reading frame K1 (ORF-K1) protein from more than 60 different HHV8 samples and demonstrated that they display up to 30% amino acid variability and cluster into four very distinct evolutionary subgroups (the A, B, C, and D subtypes) that correlate with the major migrationary diasporas of modern humans. Here we have extended this type of analysis to six other loci across the HHV8 genome to further evaluate overall genotype patterns and the potential for chimeric genomes. Comparison of the relatively conserved ORF26, T0.7/K12, and ORF75 gene regions at map positions 0. 35, 0.85, and 0.96 revealed typical ORF-K1-linked subtype patterns, except that between 20 and 30% of the genomes analyzed proved to be either intertypic or intratypic mosaics. In addition, a 2,500-bp region found at the extreme right-hand side of the unique segment in 45 HHV8 genomes proved to be highly diverged from the 3,500-bp sequence found at this position in the other 18 HHV8 genomes examined. Furthermore, these previously uncharacterized "orphan" region sequences proved to encompass multiexon latent-state mRNAs encoding two highly diverged alleles of the novel ORF-K15 protein. The predominant (P) and minor (M) forms of HHV8 ORF-K15 are structurally related integral membrane proteins that have only 33% overall amino acid identity to one another but retain conserved likely tyrosine kinase signaling motifs and may be distant evolutionary relatives of the LMP2 latency protein of Epstein-Barr virus. The M allele of ORF-K15 is also physically linked to a distinctive M subtype of the adjacent ORF75 gene locus, and in some cases, this linkage extends as far back as the T0.7 locus also. Overall, the results suggest that an original recombination event with a related primate virus from an unknown source introduced exogenous right-hand side ORF-K15(M) sequences into an ancient M form of HHV8, followed by eventual acquisition into the subtype C lineage of the modern P-form of the HHV8 genome and subsequent additional, more recent transfers by homologous recombination events into several subtype A and B lineages as well.

Identification and rapid quantification of early- and late-lytic human herpesvirus 8 infection in single cells by flow cytometric analysis: characterization of antiherpesvirus agents

Human herpesvirus 8 (HHV-8) infection is associated with Kaposi's sarcoma, primary effusion lymphoma (PEL), and multicentric Castleman's disease. In this study, we used monoclonal antibodies (MAbs) directed against HHV-8 lytic cycle-associated proteins encoded by open reading frame (ORF) 59 (nuclear PF-8 protein) and ORF K8.1 (viral envelope glycoprotein K8.1 [gpK8.1]) to investigate HHV-8 lytic infection in single cells. Lytically infected cells were labeled with MAbs, stained with fluorescently conjugated secondary Abs, and analyzed by flow cytometry. A 3-day stimulation of HHV-8-positive PEL cell lines (BCBL-1 and BC-3) with 12-O-tetradecanoylphorbol-13-acetate (30 nM) or n-butyric acid (0.3 mM) maximized the expression of lytic-phase viral proteins and minimized cell toxicity. The absolute number of expressing cells was inducer and cell line dependent. Expression of PF-8 occurred earlier and more frequently (in up to 20% of cells) than did expression of gpK8.1. A subset of PF-8 positive cells (25%) co-expressed gpK8.1, representing the majority of gpK8.1 expressing cells. Acyclovir, foscarnet, cidofovir, and PMEA reduced the number of cells expressing gpK8.1, but not the number expressing the nonstructural early lytic gene product PF-8. By contrast, alpha interferon (IFN-alpha) and IFN-beta reduced expression of both PF-8 and gpK8.1, implying an overall inhibitory effect on viral gene transcription or translation. In summary, we have characterized and quantified HHV-8 lytic infection in single cells by dual measurement of early- and late-lytic-cycle HHV-8 protein expression. This technique should prove useful for screening of possible antiherpesvirus agents and for detailed phenotypic characterization of HHV-8-infected cells in vitro and in patients with HHV-8-associated diseases.

High-level variability in the ORF-K1 membrane protein gene at the left end of the Kaposi's sarcoma-associated herpesvirus genome defines four major virus subtypes and multiple variants or clades in different human populations

Infection with Kaposi's sarcoma (KS)-associated herpesvirus (KSHV) or human herpesvirus 8 (HHV8) is common in certain parts of Africa, the Middle East, and the Mediterranean, but is rare elsewhere, except in AIDS patients. Nevertheless, HHV8 DNA is found consistently in nearly all classical, endemic, transplant and AIDS-associated KS lesions as well as in some rare AIDS-associated lymphomas. The concept that HHV8 genomes fall into several distinct subgroups has been confirmed and refined by PCR DNA sequence analysis of the ORF-K1 gene encoding a highly variable glycoprotein related to the immunoglobulin receptor family that maps at the extreme left-hand end of the HHV-8 genome. Among more than 60 different tumor samples from the United States, central Africa, Saudi Arabia, Taiwan, and New Zealand, amino acid substitutions were found at a total of 62% of the 289 amino acid positions. These variations defined four major subtypes and 13 distinct variants or clades similar to those found for the HIV ENV protein. The B and D subtype ORF-K1 proteins differ from the A and C subtypes by 30 and 24%, respectively, whereas A and C differ from each other by 15%. In all cases tested, multiple samples from the same patient were identical. Examples of the B subtype were found almost exclusively in KS patients from Africa or of African heritage, whereas the rare D subtypes were found only in KS patients of Pacific Island heritage. In contrast, C subtypes were found predominantly in classic KS and in iatrogenic and AIDS KS in the Middle East and Asia, whereas U.S. AIDS KS samples were primarily A1, A4, and C3 variants. We conclude that this unusually high diversity, in which 85% of the nucleotide changes lead to amino acid changes, reflects some unknown powerful biological selection process that has been acting preferentially on this early lytic cycle membrane signalling protein. Two distinct levels of ORF-K1 variability are recognizable. Subtype-specific variability indicative of long-term evolutionary divergence is both spread throughout the protein as well as concentrated within two 40-amino-acid extracellular domain variable regions (VR1 and VR2), whereas intratypic variability localizes predominantly within a single 25-amino-acid hypervariable Cys bridge loop and apparently represents much more recent changes that have occurred even within specific clades. In contrast, numerous extracellular domain glycosylation sites and Cys bridge residues as well as the ITAM motif in the cytoplasmic domain are fully conserved. Overall, we suggest that rather than being a newly acquired human pathogen, HHV8 is an ancient human virus that is preferentially transmitted in a familial fashion and is difficult to transmit horizontally in the absence of immunosuppression. The division into the four major HHV8 subgroups is probably the result of isolation and founder effects associated with the history of migration of modern human populations out of Africa over the past 35,000 to 60,000 years.

Co-infection with opportunistic pathogens promotes human immunodeficiency virus type 1 infection in macrophages

Human immunodeficiency virus type 1 (HIV-1) infection is dependent on susceptible host cells that express both CD4 and chemokine co-receptors. The co-receptor CCR5 is associated with primary infection by macrophage-tropic virus isolates, whereas CXCR4 is commonly associated with T cell- and dual-tropic viruses. Once infected, lymphocytes and macrophages may replicate HIV-1 or harbor latent virus, depending on environmental factors and cellular activation. Immune activation is often associated with viremia, which is consistent with enhanced infection and viral replication in activated cells harboring virus. In this regard, opportunistic infections activate the immune system with the detrimental sequelae of enhanced viral replication and viremia. Under these conditions, viral expansion extends beyond T cells to tissue macrophages, many of which are co-infected with opportunistic pathogens. The opportunistic infections promote macrophage susceptibility to HIV-1 through cytokine modulation and altered chemokine co-receptors, potential targets for intervention.

The macrophage origin of the HIV-expressing multinucleated giant cells in hyperplastic tonsils and adenoids

Replication and storage of virus are characteristic features of hyperplastic lymphoid tissues in HIV infection. In opportunistic infections, HIV is synthesized by phagocytic mononuclear and Langhans'-type multinucleated macrophages that coexpress the dendritic cell-associated S-100 and p55 antigens. However, similar cells in hyperplastic tonsils and adenoids from HIV+ individuals were alternatively identified as macrophages or, on the basis of the same S-100 and p55 staining, as dendritic cells. To consider establishing the role of these HIV-rich cells in HIV disease, it is important to reconcile this apparent discrepancy in identity. Hyperplastic tonsils and adenoid specimens were analyzed by HIV RNA in situ hybridization (ISH), light and transmission electron microscopy (TEM), and immunohistochemistry (IHC) (HIV Gag p24 protein, S-100, p55, CD68, HAM56, lysozyme, alpha-1-anti-trypsin, and alpha-1-anti-chymotrypsin). In HIV+ pediatric and adult surgical specimens (n = 11), the giant cells and their mononuclear counterpart were positive for both macrophage and p55 and S-100 IHC markers. In addition, TEM, p24 IHC, and ISH showed HIV expression by cells with typical features of macrophages. Furthermore, these cells were not unique to HIV+ specimens, being seen in 20% of hyperplastic T&A surgical specimens (n = 57) lacking HIV as well as in several types of granulomatous processes, such as sarcoidosis. These cells appear to represent an activated phenotype that can develop independent of HIV, but that may represent a viral host in HIV-infected individuals. Thus, the giant and mononuclear cells that produce striking amounts of HIV in tonsils and adenoids are of macrophage origin, yet, as in opportunistic infections, share dendritic cell-associated antigens, reflecting a common CD34+ bone marrow progenitor.

Human immunodeficiency virus-rich multinucleated giant cells in the colon: a case report with transmission electron microscopy, immunohistochemistry, and in situ hybridization

Multinucleated giant cells (MNGCs) expressing the human immunodeficiency virus (HIV) are characteristically found in hyperplastic tonsils and adenoids, acquired immunodeficiency syndrome encephalitis, vacuolar myelopathy, and lymph nodes coinfected with opportunistic pathogens. We identified similar polykaryons in the hyperplastic gut-associated immune system of an HIV-infected patient. Colonic biopsy specimens from this patient with heme-positive stools were studied by light and transmission electron microscopy (TEM), immunohistochemistry, and in situ hybridization for HIV-specific RNA. No bleeding source was identified by endoscopic or light microscopic examination of the biopsied tissues. There was diffuse and nodular lymphoid hyperplasia with germinal centers. HIV RNA-positive and p24 gag-positive Langhans'-type MNGCs and mononuclear cells (MNCs) were present within the lamina propria The MNGCs and MNCs were identified as macrophages on the basis of TEM and expression of CD68, HAM56, and lysozyme markers. They also expressed S100 protein, a marker of dendritic/Langerhans' cells, but they lacked Birbeck granules by TEM. In situ hybridization demonstrated RNA expression by MNGCs, MNCs, and follicular dendritic cells. TEM revealed budding and mature HIV particles on the plasma membranes of MNGCs, MNCs, and follicular dendritic cells. We conclude, therefore, that hyperplastic gut-associated immune systems can contain HIV-positive MNGCs and MNCs of the type seen in tonsils and adenoids and opportunistic pathogen-infected lymph nodes. Associated with immune activation, macrophages can express markers of dendritic/Langerhans' cells, cell types derived from the same CD34-positive bone marrow progenitor.

Changes in circulating levels of HIV, CD4, and tissue expression of HIV in a patient with recent-onset ulcerative colitis treated by surgery. Case report

OBJECTIVE

To determine CD4+ T-cell count and circulating and tissue levels of HIV before and after surgery in a patient with recent-onset ulcerative colitis.

STUDY DESIGN/METHODS

CD4 lymphocytes and circulating and tissue HIV RNA levels were measured in an HIV-infected patient with ulcerative colitis before and after proctocolectomy.

RESULTS

Approximately 3 weeks prior to surgery for ulcerative colitis that was unresponsive to corticosteroids, the patient's CD4 count was 930 cells/mm3 and fell to 313 cells/mm3 within 10 days; the viral burden was approximately 80,000 RNA copies/mL. Tissue macrophages and lymphocytes in biopsy and resection specimens were shown to express high levels of HIV RNA by in situ hybridization. Five days postoperatively, the patient became asymptomatic and was discharged on tapering prednisone without antiretroviral agents. After surgery, the patient's CD4 count progressively rose, while viral RNA levels precipitously dropped. At 3, 6, and 15 weeks postoperatively, CD4 and viral RNA counts were 622 cells/mm3 and 31,300 RNA copies/mL, 843 cells/mm3 and 11,400 RNA copies/mL, and 747 cells/mm3 and 1500 RNA copies/mL, respectively.

CONCLUSIONS

Circulating levels of HIV and CD4+ cells, as well as tissue expression of HIV, apparently can be influenced by localized inflammatory processes such as those occurring in inflammatory bowel disease.

Animal models of human microsporidial infections

Two new models have been described for Enterocytozoon bieneusi, non-human primates and immuno-suppressed gnotobiotic pigs, but there still is no successful cell culture system. The intestinal xenograft system holds promise as an animal model for Encephalitozoon intestinalis. Encephalitozoon hellem is easily propagated in mice, and also may be an important cause of spontaneous disease of psittacine birds. Encephalitozoon cuniculi occurs spontaneously in a wide variety of animals and can be induced experimentally in athymic mice. This is a useful experimental system and animal model, but the infection is relatively rare in man. Mammalian microsporidioses first were recognized as spontaneous diseases of animals that later confounded studies intended to elucidate the nature of diseases of humans. Much was learned about both experimental and spontaneous animal microsporidial infections that subsequently has been applied to the human diseases. In addition, new diseases have appeared, in both animals and humans, for which models are being developed. Since there are now animal models for almost all the known human microsporidioses, information on pathogenesis, host defenses, and effective treatments may become available soon. The microsporidioses provide a good example of the value of comparative pathology. Dr. Payne: Joe Payne. How much accidental infection has occurred with adjacent laboratory animals? Dr. Shadduck: A hard question. The organisms are thought to spread horizontally, and there is some pretty good evidence for that in rabbits. One assumes that this also is the explanation for the occurrence in infected kennels. Horizontal transmission probably occurs via contaminated urine, at least in the case of rabbits and dogs. Experimentally, horizontal transmission has been difficult to demonstrate in mice. Relative to the danger in people, I don't know how to answer that. I have always treated this as one of those things where you should be careful, but you shouldn't get paranoid. So, we have handled infected cell cultures and animals as if they were potentially infectious for man, but not as if they were something as hot as the human AIDS virus, for example. With the increasing number of reports in humans, I think it is clear that one would never want anybody who was at risk of being immunocompromised to work with these organisms. Dr. Fenkel: Are there other questions? Dr. Mysore: How do the parasites spread within the infected hosts? Dr. Shadduck: The usual answer is hematogenously via infected macrophages, but data that actually support that statement are rare. One does see infected macrophages in tissues, so it is not unreasonable to think that some of them escape and lodge in other tissues. But that has never actually been formally demonstrated. Dr. Nakeeb: Is E. bieneusi a human pathogen? Dr. Shadduck: The answer depends on which paper you read and what approach the authors took. There are papers in which the authors argue that the organism is not a cause of clinical disease in AIDS patients, but the general belief today is that the parasite does cause diarrhea and enteritis. I think the evidence for pathogenicity is quite strong for the various species of the Encephalitozoon, based on the severity and distribution of the lesions.

Mycobacterium avium complex augments macrophage HIV-1 production and increases CCR5 expression

Infection with HIV-1 results in pronounced immune suppression and susceptibility to opportunistic infections (OI). Reciprocally, OI augment HIV-1 replication. As we have shown for Mycobacterium avium complex (MAC) and Pneumocystis carinii, macrophages infected with opportunistic pathogens and within lymphoid tissues containing OI, exhibit striking levels of viral replication. To explore potential underlying mechanisms for increased HIV-1 replication associated with coinfection, blood monocytes were exposed to MAC antigens (MAg) or viable MAC and their levels of tumor necrosis factor alpha (TNFalpha) and HIV-1 coreceptors monitored. MAC enhanced TNFalpha production in vitro, consistent with its expression in coinfected lymph nodes. Using a polyclonal antibody to the CCR5 coreceptor that mediates viral entry of macrophage tropic HIV-1, a subset of unstimulated monocytes was shown to be CCR5-positive by fluorescence-activated cell sorter analysis. After stimulation with MAg or infection with MAC, CCR5 expression was increased at both the mRNA level and on the cell surface. Up-regulation of CCR5 by MAC was not paralleled by an increase in the T cell tropic coreceptor, CXCR4. Increases in NF-kappaB, TNFalpha, and CCR5 were consistent with the enhanced production of HIV-1 in MAg-treated adherent macrophage cultures as measured by HIV-1 p24 levels. Increased CCR5 was also detected in coinfected lymph nodes as compared with tissues with only HIV-1. The increased production of TNFalpha, together with elevated expression of CCR5, provide potential mechanisms for enhanced infection and replication of HIV-1 by macrophages in OI-infected cells and tissues. Consequently, treating OI may inhibit not only the OI-induced pathology, but also limit the viral burden.

The Warthin-Finkeldey-type giant cell in HIV infection, what is it?

A study was conducted to ascertain the origin of the Warthin-Finkeldey-type giant cell that is common to lymphoid tissues of HIV-infected individuals. Light microscopy (LM) and transmission electron microscopy (TEM), in situ hybridization (ISH) (HIV-specific RNA), and immunohistochemistry (HIV p24, OPD4, CD3, CD45 UCHL, CD21, CD35, S-100, p55 (actin-bundling protein), CD68, HAM56, alpha-1-antitrypsin, alpha-1-antichymotrypsin, and lysozyme) studies were performed on hyperplastic tonsil, adenoid, lymph node, and intestinal MALT specimens from HIV+ patients. Warthin-Finkeldey-type giant cells (WFTGC) and follicular dendritic cells (FDC) shared characteristic morphologic (high N: C ratio; crowded, irregular nuclei; thin filaments with dense bodies; desmosomes; and cilia) and immunophenotypic (CD21+, CD35+, S-100+, p55, and vimentin+) features. Also, transitional forms between binucleated FDC and WFTGC were identified by TEM. TEM and ISH revealed evidence of HIV expression by FDC, but not WFTGC. WFTGC in HIV- lymphoid specimens displayed identical LM and IHC characteristics. The WFTGC in HIV infection appears to represent a multinucleated form of FDC.

Renal Encephalitozoon (Septata) intestinalis infection in a patient with AIDS. Post-mortem identification by means of transmission electron microscopy and PCR

We describe the occurrence of renal Encephalitozoon (Septata) intestinalis infection in a 35-year-old AIDS patient who died with disseminated tuberculosis. The patient did not complain of specific symptoms involving the kidney or lower urinary tract during life, but at autopsy, light microscopic examination of the kidney revealed numerous small round or oval bodies in the tubules and tubular cell cytoplasm that were interpreted as intracellular protozoa. Transmission electron microscopy of tissue retrieved from paraffin-embedded samples identified these organisms as microsporidia belonging to the Encephalitozoonidae family, but did not allow definitive identification of the species of infecting parasite. This was made possible only by means of Southern blot hybridization after the polymerase chain reaction, which recognized the micro-organism as E. intestinalis.

Infection of human primary renal epithelial cells with HIV-1 from children with HIV-associated nephropathy

Children affected with human immunodefficiency virus (HIV)-associated nephropathy (HIVAN) usually develop significant renal glomerular and tubular epithelial cell injury. The pathogenesis of these changes is not clearly understood. Human renal tubular epithelial cells (RTEc) do not express CD4 surface receptors, and it is not clear whether these cells can be infected by HIV-1. Certain strains of HIV-1, however, have been shown capable of infecting CD4-negative epithelial cell lines. We hypothesized that the inability of laboratory strains of HIV-1 to infect renal epithelial cells may be due to a limited tropism, as opposed to wild-type viruses derived from children with HIVAN, and that viruses derived from these children are capable of infecting RTEc from the same patient. Here, we have demonstrated that HIV-1 isolates from children with HIVAN can productively infect RTEc through a CD4 independent pathway, and that infected mononuclear cells can transfer the virus to human RTEc. Human RTEc sustained low levels of viral replication and HIV-1 inhibited the growth and survival of cultured human RTEc. Thus, HIV-1 may directly induce degenerative changes in RTEc of children with HIVAN. Infected macrophages may play a relevant role in this process by transferring viruses to RTEc.