Retroviruses immunodeficiency syndrom

The human immunodeficiency vims (HIV) is the causative agent of the acquired immunodeficiency syndrome (AIDS). HIV is a retrovirus, whose replication includes the transcription of the single-stranded RNA genome into double stranded DNA (reverse transcription) and the covalent insertion of the DNA... 

We have discussed in a general way the nature of animal viruses in the first part of this chapter. Now we discuss in some detail the structure and molecular biology of a number of important animal viruses. Viruses will be discussed which illustrate different ways of replicating, and both RNA and DNA viruses will be covered. One group of animal viruses, those called the retroviruses, have both an RNA and a DNA phase of replication. Retroviruses are especially interesting not only because of their unusual mode of replication, but because retroviruses cause such important diseases as certain cancers and acquired immunodeficiency syndrome (AIDS). 

Many viruses and retroviruses have genomes that are single-stranded RNA instead of DNA. These include the acquired immunodeficiency syndrome (AIDS) virus and some retroviruses that cause cancer. Here, an enzyme called reverse transcriptase converts the RNA genome of the virus into the DNA of the host cell genome, thus infecting the host. 

Human immunodeficiency virus (HIV) is a single-stranded RNA retrovirus that causes acquired immunodeficiency syndrome (AIDS), a condition in which individuals are at increased risk for developing certain infections and malignancies. The virus is found in two major forms HIV-1, the most prevalent worldwide, and HIV-2, the most common in western Africa. More than 22 million people have died of HIV infection, and 40 million are believed to be infected worldwide. AIDS epidemics threaten populations in sub-Saharan Africa, Southeast Asia, Central and South America, and Russia. In the United States about 450,000 deaths have occurred and another 900,000 people are estimated to carry the virus. Although the development of new drugs, complex multidrug regimens, and behavioral modification have done much to combat the spread of HIV in-... 

The human immunodeficiency virus (HIV) is one of only a few retroviruses known to infect humans. It is estimated that approximately twenty-two million people are now infected worldwide [1]. With only a tiny number of exceptions, infection ultimately leads to the development of the lethal condition of acquired immunodeficiency syndrome, or AIDS. To date, only a handful of drugs have been shown to have any effect on the course of the disease. These are, in general, relatively ineffective at significantly prolonging life, and drug resistance develops rapidly. Equally discouraging, vaccines have not yet been developed to prevent infection. 

K., Sliski, A., and Gallo, R. C., Seroepidemiological studies of human T-lymphotropic retrovirus type III in acquired immunodeficiency syndrome. Lancet 1, 1438-1440 (1984). 

There are also immunodeficiency states that are primary and can be caused by phagocytic cell defects, deficiencies in the complement system, B- and T-cell deficiency, and other causes. Secondary immunodeficiency disorders can result from malnutrition, cytotoxic drugs, infections with pyrogenic bacteria, and infections with an RNA retrovirus, as in the acquired immunodeficiency syndrome (AIDS). 

The retroviruses have been the subject of intense study because of the emergence of human immunodeficiency virus (HIV) and acquired immunodeficiency syndrome (AIDS), and this study has led to a structural understanding of complicated viruses that has been unfolding rapidly. In the immature virus, two copies of (+)ssRNA are surrounded by a spherical immature capsid that contains about 2000 copies of the Gag polyprotein (the precursor of the structural proteins), and up to a few hundred copies of larger polyproteins, the most ubiquitous being Gag-Pol, a polyprotein that in addition contains precursors of the proteinase (PR), reverse... 

The retrovirus destroys the immune system, resulting in human immunodeficiency virus (HIV). An HIV patient develops acquired immunodeficiency syndrome (AIDS) when the retrovirus becomes active and results in opportunistic infection and malignant neoplasm. 

Barre-Sinoussi, F., Chermann, J. C., Rey, F Nugeyre, M. T., Chamaret, S., Gruest, J., Dauguet, C., Axler-Blin, C., Brun-Vezinet, F., Rouzioux, C., Rozenbaum, W., and Montagnier, L. (1983) Isolation of a T-lymphotropic retrovirus from a patient at risk for acquired immunodeficiency syndrome. Science 220, 868-871. 

Since 1980 three types of infectious human T-cell lymphotrophic viruses (HTLVs) have been identified. HTLV-I is frequently associated with adult forms of T-cell leukemia-lymphoma, HTLV-II with hairy T-cell leukemia, and HTLV-III (now called human immunodeficiency virus HIV) with acquired immunodeficiency syndrome (AIDS). Other related retroviruses have been isolated from human and primate populations. Molecular biologists have developed a wealth of information about the biology and genetics of retroviruses, including the complete sequencing of their genomes. Despite this enormous research effort it still... 

Barre-Sinoussi F, Chermann J, Rey F, et al. Isolation of a T-lymphotropic retrovirus from a patient at risk for acquired immunodeficiency syndrome (AIDS). Science 1983 220 868-871. 

The most daunting claim to fame for a human retrovirus came in the early 1980s, when teams of researchers in France and the United States jointly identified human immunodeficiency virus (HIV-1) as the etiologic agent in the human acquired immunodeficiency syndrome called AIDS. HIV infection of human T cells eventually results in T-cell death and loss of these important cells from the immune system. AIDS patients with extremely low numbers of T cells are highly susceptible to opportunistic infectious diseases, which are often the underlying cause of death due to AIDS. 

Retroviruses are RNA-DNA viruses that require host-cell genome integration to complete their replication cycle. The retroviral enzyme reverse transcriptase is an RNA-dependent DNA polymerase that has important uses in recombinant DNA methodologies such as the synthesis of complementary DNA (cDNA). The human immunodeficiency virus (HIV) is the etiologic agent that causes acquired immunodeficiency syndrome (AIDS) in humans. HIV infects and destroys human T cells, which are required for immune system functions. 

Certain diseases such as acquired immunodeficiency syndrome (AIDS) and herpes are caused by retroviruses. The genetic information of a retrovirus is contained in its RNA. The retrovims uses the sequence of bases in RNA as a template to synthesize DNA. It is called a retrovirus because its genetic information flows from RNA to DNA instead of the more typical flow from DNA to RNA. 

Retroviruses are RNA viruses that cause diseases such as acquired immunodeficiency syndrome (AIDS) see Chapter 50) and T-cell leukemias (human T-ceU lymphotropic virus I [HTLV-I]). They contain a reverse transcriptase that makes a DNA copy of the viral RNA template. The DNA copy integrates into the host genome, at which point it is referred to as a provirus and is transcribed into both genomic RNA and mRNA for translation into viral proteins. The polymerase of hepadnaviruses possesses reverse transcriptase activity. 

Abstract Acquired immunodeficiency syndrome (AIDS) and its related disorders, caused by retrovirus human immunodeficiency virus (HIV) are a major health concern worldwide. HIV protease is one of the major viral targets for the development of new chemotherapeutics. Currently, many HIV protease inhibitors are used in combination with HIV reverse transcriptase inhibitors. However, the use of current drugs regimens has several shortcomings, such as adherence, tolerability, long-term toxicity and drug- and... 

In 1983 the move to develop red cell substitutes intensified when it was recognized that the acquired immune deficiency syndrome (AIDS) could be transmitted by the blood-bome human immunodeficiency virus (HIV). Concern for the nation s blood supply followed. Since that time other retroviruses have been identified, efforts to screen blood not only for these agents but also for viruses that cause hepatitis have intensified, the indications for transfusion have been reevaluated, and the use of blood products has become much more efficient. More careful screening of donors, testing of all donated units, and a general awareness in the donor population have all contributed to a decreased risk from transfusion-contracted AIDS. 

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