Human Immunodeficiency Virus Retroviruses Research Articles

Use of recombinant viruses to assess the pattern of early human immunodeficiency virus breakthrough infection in the presence of stavudine.

A variety of cell lines were infected with replication-defective recombinant retroviruses in the presence of stavudine (d4T). Cells which were infected despite the presence of d4T were isolated and subjected to infection with other retroviruses [replication-competent human immunodeficiency virus (HIV), replication-defective HIV or replication-defective recombinant murine retroviruses]. Each of the host cell types tested had a small subset of cells that were infected with HIV or murine retroviruses in the presence of d4T. Some of these infected cells could be infected repeatedly at high efficiency in the presence of d4T. This phenotype of 'persistent refractoriness' to the antiviral effects of d4T could be overcome by the addition of 5-fluoro-2-deoxyuridine (floxuridine) to d4T. The d4T-floxuridine combination also had potent antiretroviral effects in primary blood mononuclear cells.

Sensitization of cells and retroviruses to human serum by (alpha 1-3) galactosyltransferase.

Mammalian C-type retroviruses are inactivated by human serum, following triggering of the classical complement cascade. This may have inhibited transmission to humans of C-type oncoviruses from other mammals. Indeed, the retroviruses human immunodeficiency virus and human T-cell leukaemia virus are resistant to human complement. Antibody-independent activation of human C1q, the first component of the classical pathway, by retroviral envelope proteins has been described. However, retroviruses produced from human cells are resistant to inactivation by human complement and human serum is known to contain antibodies directed against carbohydrates on retroviral envelopes. Gal(alpha 1-3)Gal terminal carbohydrates are expressed by most mammals but are absent in humans, which lack a functional (alpha 1-3)galactosyltransferase gene. Here, we demonstrate that anti-Gal(alpha 1-3)Gal antibodies in human serum inactivate retroviruses produced from animal cells. Expression of porcine (alpha 1-3)galactosyltransferase in human cells renders the cells and the retroviruses they produce sensitive to human serum.

Immunopathogenesis of inflammatory myopathies.

Immune-mediated mechanisms appear to play a primary role in the pathogenesis of polymyositis (PM) and dermatomyositis (DM). The serum of patients with active DM has high levels of circulating complement fragments C3b, C4b, and C5b-9 membranolytic attack complex (MAC) and demonstrates a very high C3 uptake in an vitro assay system. The MAC and the immune complex-specific C3bNEO fragment are deposited on the endomysial capillaries early in the disease and lead sequentially to loss of capillaries, muscle ischemia, muscle fiber necrosis, and perifascicular atrophy. In contrast, in PM the muscle fiber injury is initiated by sensitized CD8+ cytotoxic T cells that recognize heretofore unknown and probably endogenous muscle antigens in the context of major histocompatibility complex (MHC) class I expression. A restricted (oligoclonal) pattern of T-cell receptor with prominence of Va1, Vb6, and Vb15 genes is noted within the endomysial infiltrates suggesting that the T-cell response is antigen driven. In both PM and DM, intercellular adhesion molecule (ICAM)-1 and vascular cell adhesion molecule (VCAM)-1 are upregulated in the endomysial endothelial cells and function as ligands for the leukocyte integrins leukocyte function-associated antigen (LFA)-1 and very late activating antigen (VLA)-4, allowing activated lymphocytes to adhere to the endothelial cells and migrate to the muscle fibers. Among viruses, only the retroviruses human immunodeficiency virus (HIV) and human T-cell lymphotropic virus (HTLV)-1 have been convincingly shown to trigger PM, which is mediated by nonviral-specific, cytotoxic CD8+ cells. The treatment of inflammatory myopathies remains empirical. Many patients respond to steroids to some degree and for some period of time. Azathioprine, methotrexate, cyclosporine, cyclophosphamide, and plasmapheresis can be of mild to moderate benefit. High-dose intravenous immunoglobulin (IVIg) is a promising therapeutic modality for some patients resistant to therapies. In a controlled study, IVIg was effective in DM not only in improving the clinical symptoms but also in reversing the underlying immunopathology. The role of IVIg in PM and IBM is under study in control trials.

A General Model for the Surface Glycoproteins of HIV and Other Retroviruses

A hypothetical model of the surface (SU) glycoproteins of human immunodeficiency virus (HIV) and other retroviruses is proposed. The model is based on repetition of a limited number of sequence motifs conserved within the virus family; similarities in biological, immunological, or genetic properties; as well as the tendency for regions of dissimilar sequence to share protein structures predicted by computer algorithms. It is proposed that the protein consists of three structural and functional domains interspersed by relatively conserved interdomain regions. For each retrovirus, these amino-terminal, central, and carboxy-terminal domains may play different roles in binding, postbinding events, and the immune response to viral infection.

Cyotkines as Potential Therapies for Human Immunodeficiency Virus Infections

Cytokines are attracting increased interest as potential therapies for human immunodeficiency virus (HIV) infections. This attraction has particularly arisen as these cytokines have become more commercially available through recombinant technologies. This review focuses on the effects of these biological response modifiers on preclinical HIV and related retrovirus infections. Cytokines that have particularly been considered for HIV disease control include: interferons ‐α , ‐β and ‐γ, interleukins‐2. ‐3. ‐4. ‐6 and ‐7; tumour necrosis factors ‐α and ‐β; and the colony stimulating factors. Efficacy has especially been seen when these cytokines have been used in combination with the more conventional antiviral agents. Due to the many biological functions exerted by cytokines and their interweaving of biological effects with other cytokines, they appear to have the potential to both inhibit as well as enhance viral infections, depending upon how they are used, and caution is therefore urged in their use.

Blood Borne Viral Infections in Transplantation: Hepatitis Viruses and Retroviruses

Hepatitis viruses B (HBV), C (HCV) and D (HDV) and the retroviruses human immunodeficiency virus (HIV‐1) and human T celllymphotropic virus type I (HTLV‐1) and type ll (HTLV‐11) have been transmitted from infected organ and tissue donors to allograft recipients. Ascertainment of personal risk factors by health questionnaire may exclude volunteer blood donors recently exposed to transmissible diseases who could be in the ′window period′ of the infection, when routine serological screening tests are negative. Difficulty in obtaining historical evidence of possible recent exposure from a critically ill prospective organ donor may make the residual risk of infection slightly higher than the risk estimated per unit of transfused products from serologically screened volunteer blood donors. Current estimates of residual risk from transfusion based on United States data are: one in 200,000 units for HBV; one in 2000 to one in 6000 units for HCV; one in 40.000 lo one in 60,000 units for HIV‐1; and one in 69,272 units for HTLV‐1/11. Despite recent improvements in anti‐HCV testing, current screening assays underestimate the incidence of transmission and prevalence of HCV infection among immunosuppressed organ recipients: evidence of ongoing HCV infection depends on detection of HCV RNA by polymerase chain reaction. Determination of I‐IIV‐1 p24 antigen may facilitate identification of prospective organ donors in ll1e window period of early infection and may enhance serological follow‐up of allograft recipients al risk of transplantation‐associated HIV‐1 infection. Highly sensitive assays that can be completed very rapidly are needed to ensure greater safely for the recipient of an emergency organ transplant, where time to screen a prospective donor for infectious diseases may be extremely limited.

Mechanism of action of regulatory proteins encoded by complex retroviruses.

Complex retroviruses are distinguished by their ability to control the expression of their gene products through the action of virally encoded regulatory proteins. These viral gene products modulate both the quantity and the quality of viral gene expression through regulation at both the transcriptional and posttranscriptional levels. The most intensely studied retroviral regulatory proteins, termed Tat and Rev, are encoded by the prototypic complex retrovirus human immunodeficiency virus type 1. However, considerable information also exists on regulatory proteins encoded by human T-cell leukemia virus type I, as well as several other human and animal complex retroviruses. In general, these data demonstrate that retrovirally encoded transcriptional trans-activators can exert a similar effect by several very different mechanisms. In contrast, posttranscriptional regulation of retroviral gene expression appears to occur via a single pathway that is probably dependent on the recruitment of a highly conserved cellular cofactor. These two shared regulatory pathways are proposed to be critical to the ability of complex retroviruses to establish chronic infections in the face of an ongoing host immune response.

Definition of the human immunodeficiency virus type 1 Rev and human T-cell leukemia virus type I Rex protein activation domain by functional exchange.

The human retroviruses human immunodeficiency virus type 1 (HIV-1) and human T-cell leukemia virus type I (HTLV-I) are characterized by complex regulation of gene expression. Each virus encodes a posttranscriptional regulator, the 19-kDa HIV-1 Rev protein and the 27-kDa HTLV-I Rex protein, which is required for viral replication. Expression of these trans activators results in the cytoplasmic accumulation of unspliced or singly spliced viral mRNA which encode the gag, pol, and env gene products. The finding that the HTLV-I Rex protein is able to functionally substitute for the Rev protein of HIV-1 indicates that HIV-1 Rev and HTLV-I Rex may interact with the same component of a cellular pathway involved in either mRNA splicing or transport. In this study, we have generated functional Rev/Rex hybrid proteins by domain exchange. We have defined, using in vivo and in vitro analyses, the activation domains of Rev and Rex which are the putative targets of a common host cell factor(s) required for Rev and Rex function.

Mechanism of action of regulatory proteins encoded by complex retroviruses.

Complex retroviruses are distinguished by their ability to control the expression of their gene products through the action of virally encoded regulatory proteins. These viral gene products modulate both the quantity and the quality of viral gene expression through regulation at both the transcriptional and posttranscriptional levels. The most intensely studied retroviral regulatory proteins, termed Tat and Rev, are encoded by the prototypic complex retrovirus human immunodeficiency virus type 1. However, considerable information also exists on regulatory proteins encoded by human T-cell leukemia virus type I, as well as several other human and animal complex retroviruses. In general, these data demonstrate that retrovirally encoded transcriptional trans-activators can exert a similar effect by several very different mechanisms. In contrast, posttranscriptional regulation of retroviral gene expression appears to occur via a single pathway that is probably dependent on the recruitment of a highly conserved cellular cofactor. These two shared regulatory pathways are proposed to be critical to the ability of complex retroviruses to establish chronic infections in the face of an ongoing host immune response.

Diagnosis of Human Immunodeficiency Virus Infection in Infants and Children

Since its initial description at the beginning of this decade,1-3 the acquired immunodeficiency syndrome (AIDS) has become one of the major medical, public health, and social issues of our times. Since the isolation of the retrovirus human immunodeficiency virus (HIV) from patients with AIDS and AIDS-related complex,4,5 major advances have been made in understanding the biology of the virus and the disease it causes. Diagnosis of HIV infection in adults and older children, and screening of blood products, have become routine and reliable with the use of licensed tests that detect HIV-specific antibody.6 Antiretroviral drugs, as well as new agents active against AIDS-associated opportunistic infections, have been developed and the first steps in the treatment of HIV infection and its associated illnesses have been taken. Whereas most HIV infection has occurred in adults, it has become an increasing problem among children, particularly in certain geographic areas and populations, reflecting the changing nature of the epidemiology of the disease in the United States. In contrast with the early predominance among homosexual males,7 at present the most significant increases in both HIV infection and AIDS are occurring in users of illicit intravenous drugs, in heterosexual contacts of infected individuals, and in infants born to HIV-infected mothers.8 Nationwide the prevalence of HIV infection in childbearing women remains low; however, rates as high as 1% to greater than 4% have been reported from some urban areas.9,10 Although widely disparate rates of vertical transmission have been reported,11 ongoing prospective studies indicate that the rate of transmission from HIV-infected mother to infant appears to be in the range of 24% to 35%.12-14

Various regulatory sequences are deprived of their uniqueness by the universal rule of TA/CG deficiency and TG/CT excess.

The universal rule of TA/CG deficiency-TG/CT excess endures the extremely high mutation rate of a retrovirus (human immunodeficiency virus type 1) as well as methylation of CAG rather than CG in a plant (maize). Among the consistently abundant nucleotide oligomers, there are two complementary pairs of palindromic nucleotide pentamers containing TG and CA. Out of the CAGTG and CACTG pair emerged the heptameric pair for the long-distance recombination of immunoglobulin genes, CACAGTG and CACTGTG. Reflecting their origin, these heptamers are found everywhere in all DNA, and a substantial fraction of them are accompanied by nonameric components properly spaced from them. It appears that, were the recombination event not confined to B cells, results of illegitimate recombinations might be disastrous. The other pentameric pair is TGCAT and ATGCA. Out of this pair emerged the complementary pair of transcription enhancer decamers: TNATTTGCAT for immunoglobulin light chains and ATGCAAATNA for immunoglobulin heavy chains. Again reflecting their origin, these decamers are found everywhere in all DNA and some genes--for example, in the 3' flanking region of immunoglobulin heavy chain constant region--are accompanied by a downstream "TATA box." It seems that even with regard to the productively recombined immunoglobulin genes, misinitiation of enhanced transcription is a real possibility.

ChemInform Abstract: Synthesis and Antiviral Activity of 3′‐C‐Cyano‐3′‐deoxynucleosides.

A series of 3'-C-cyano-3'-deoxynucleosides have been synthesized and evaluated as antiviral agents. Reaction of 2',5'-bis-O-(tert-butyldimethylsilyl)-beta-D-erythro-pentofuranos- 3'-ulosyl derivatives of uracil, 4-N-acetylcytosine, and adenine with sodium cyanide gave a mixture of epimeric cyanohydrins, which after 3'-deoxygenation yielded the corresponding 3'-C-cyano-3'-deoxy-beta-D-xylo-pentofuranosyl derivatives 10. These compounds were epimerized to the corresponding beta-D-ribo-pentofuranosyl derivatives 11. Desilylation of 10 and 11 gave the deprotected 3'-C-cyano-3'-deoxy-beta-D-xylo- and -ribo-pentofuranosyl nucleosides. These derivatives of uridine, cytidine, and adenine, as well as the 3'-C-cyano-3'-deoxy-beta-D-xylo- and -ribo-pentofuranosyl, 3'-C-cyano-2',3'-dideoxy-beta-D-threo- and -erythro-pentofuranosyl, and 3'-C-cyano-2',3'-dideoxy-beta-D-glycero-pent-2'-enofuranosyl derivatives of thymine, were evaluated for their antiviral activity. None of the compounds proved active against the replication of retroviruses (human immunodeficiency virus, murine sarcoma virus) at concentrations that were not toxic to the host cells. However, the 3'-C-cyano-3'-deoxy-beta-D-xylo- (12e) and -ribo-pentofuranosyl (13e) derivatives of adenine showed activity against some DNA (i.e., vaccinia) and RNA (i.e., Sindbis, Semliki forest) viruses at concentrations well below the cytotoxicity threshold.

Synthesis and antiviral activity of 3'-C-cyano-3'-deoxynucleosides.

A series of 3'-C-cyano-3'-deoxynucleosides have been synthesized and evaluated as antiviral agents. Reaction of 2',5'-bis-O-(tert-butyldimethylsilyl)-beta-D-erythro-pentofuranos- 3'-ulosyl derivatives of uracil, 4-N-acetylcytosine, and adenine with sodium cyanide gave a mixture of epimeric cyanohydrins, which after 3'-deoxygenation yielded the corresponding 3'-C-cyano-3'-deoxy-beta-D-xylo-pentofuranosyl derivatives 10. These compounds were epimerized to the corresponding beta-D-ribo-pentofuranosyl derivatives 11. Desilylation of 10 and 11 gave the deprotected 3'-C-cyano-3'-deoxy-beta-D-xylo- and -ribo-pentofuranosyl nucleosides. These derivatives of uridine, cytidine, and adenine, as well as the 3'-C-cyano-3'-deoxy-beta-D-xylo- and -ribo-pentofuranosyl, 3'-C-cyano-2',3'-dideoxy-beta-D-threo- and -erythro-pentofuranosyl, and 3'-C-cyano-2',3'-dideoxy-beta-D-glycero-pent-2'-enofuranosyl derivatives of thymine, were evaluated for their antiviral activity. None of the compounds proved active against the replication of retroviruses (human immunodeficiency virus, murine sarcoma virus) at concentrations that were not toxic to the host cells. However, the 3'-C-cyano-3'-deoxy-beta-D-xylo- (12e) and -ribo-pentofuranosyl (13e) derivatives of adenine showed activity against some DNA (i.e., vaccinia) and RNA (i.e., Sindbis, Semliki forest) viruses at concentrations well below the cytotoxicity threshold.

A general model for the transmembrane proteins of HIV and other retroviruses.

A hypothetical model of the transmembrane (TM) protein of human immunodeficiency virus (HIV) is proposed that is derived from the known structure of the influenza TM protein HA2. This model is consistent with computer algorithms of predicted protein structure and with known properties of TM proteins determined by sequence homology, site-directed mutations, peptide analogs, immunochemistry, or other biologic means. It is applicable to a wide variety of retroviral TM proteins differing widely in overall molecular weight.

Immunodeficiency virus rev trans-activator modulates the expression of the viral regulatory genes.

The pathogenic human retrovirus human immunodeficiency virus type 1 (HIV-1) encodes two trans-acting nuclear proteins, tat and rev, whose functional expression is essential for viral replication in vitro. The tat protein greatly enhances the expression of both structural and regulatory genes of HIV-1 (linked to the viral long-terminal-repeat promoter element), whereas the rev gene product (previously termed art or trs) has only been shown to be required for the synthesis of structural proteins. Here, we demonstrate that rev also moderates the expression of regulatory genes of HIV-1. It decreases the expression of messenger RNAs that encode the full-length form of the viral tat gene product or the rev protein itself, and induces the synthesis of a previously unreported, truncated tat protein. These actions of rev are mediated by a dramatic shift in the ratio of spliced to unspliced cytoplasmic HIV-1 mRNA. Therefore rev not only activates the synthesis of the viral structural proteins, but also modulates the level and quality of HIV-1 regulatory gene expression.

Human immunodeficiency virus in brain biopsies of patients with AIDS and progressive encephalopathy.

Human immunodeficiency virus (HIV) has been identified in patients with AIDS in their circulating and tissue lymphocytes and in their monocyte-macrophages, an arm of the cell-mediated immune system. We report our findings of HIV in brain biopsies. Virus was detected in oligodendroglial and astroglial cells. Virus was also present in the brain capillaries, both in lumens and at the endothelial gaps. Virus was also found in extracellular spaces. Budding forms of the developing virus and bar-shaped nucleoids of mature virus, the diagnostic hallmark of the HIV retrovirus, were identified in brain tissue of five of seven patients with AIDS studied. We believe that HIV may enter the the brain via the vascular capillaries (through the endothelial gaps), bind to brain cells containing T4 receptors, enter the cells, and replicate. There follows a reactive hyperplasia and degeneration of oligodendroglial and astroglial cells. The oligodendroglial cells are the myelin-forming cells, and thus, the result is myelin degeneration.

HIV Antibody Screening

THE ACQUIRED immunodeficiency syndrome (AIDS) poses a compelling ethical challenge to medicine, science, public health, the legal system, and our political democracy. This report focuses on one aspect of that challenge: the use of blood tests to identify individuals who have been infected with the retrovirus human immunodeficiency virus (HIV). In this article we follow the terminology recently proposed by the International Committee on the Taxonomy of Viruses; that is, we use the term<i>human immunodeficiency virus</i>. This replaces the more cumbersome dual terminology of human T-cell lymphotropic virus type III/lymphadenopathy-associated virus (HTLV-III/ LAV). The issue is urgent the tests are already in use and plans to implement them much more broadly are being proposed.¹The issue is also complex: at stake is a potential conflict between the community's interests in stopping the spread of a devastating disease and in preserving important values of individual liberty and equal rights.

Viral Infections of the Nervous System

Part 1 General principles: historical background viruses and virus-cell interactions - nature of viruses, virus-cell interactions, virus-virus interations, effects of virus, replication of cells pathogenesis of CNS infections - experimental approaches, entry of viruses, pathways of neurinvasion, neurotropism, neurovirulence immune responses - anatomy of the immune system, immune responses to viruses, immune responses in the CNS, virus clearance from the CNS. Part 2 Acute neurological diseases: meningitis, encephalitis and poliomyelitis - general considerations, enteroviruses, mumps, adenoviruses, parvovirus, arenaviruses, filoviruses, arbviruses, differential diagnosis herpesvirus infections - varicella-zoster virus, Epstein-Barr virus, cytomegalovirus, human herpesviruses 6 and 7 rabies postinfectious demyelinating diseases - considerations of mechanisms, postinfectious enecphalomyelitis, Guillan-Barre syndrome other postviral syndromes - virus-induced encephalopahty, Reye syndrome, postpolio syndrome, chronic fatigue syndrome. Part 3 Chronic neurological diseases: chronic inflammatory and demyelinating diseases - mechanisms of virus persistence in the CNS, subacute sclerosing panencephalitis, progressive rubella panencephalitis, progresive multifocal leukoencephalopathy, possible viral cause of multiple sclerosis, possible viral cuases of other chronic inflammatory diseases retroviruses - nature of retroviruses, human T-cell lymphotrophic viruses, neurological diseases of animal retroviruses human immunodeficiency virus - human immunodeficinecy virus infections, neurological diseases, pathogenesis of neurological diseases, treatment viral infections of the developing nervous sytems - pathogenesis of foetal infections, foetal and neonatal infections in humans, viral teratogenesis in animals degenerative diseases and prions - scrapie, kuru, Creutzfeld-Jakob disease, bovine spongiform encephalopathy, possible viral causes of human degenerative diseases. Part 4 Other perspectives: cerebal tumours - pathogenesis of cell transformation by viruses, experimental production of cerebal tumous evidence for viruses in human brain tumours neurovirology afield - retinitis, labyrinthitis, myositis, vasculitis prevention and treatment - environmental control, vaccines, antiviral drugs postscripts - in defense of the white mouse, Koch's postulates revisited, emerging viral infections.