HIV检查 ppt课件

Retroviruses,Retroviruses are enveloped ,single-stranded plus-sense RNA viruses. They encode an enzyme called reverse transcriptase that converts the RNA genome into a double-stranded DNA copy that subsequently becomes integrated into the host cell DNA.,Retroviruses structure,Retroviruses are classified into three families: Oncoviruses,(onco-, “related to a tumor”) Lentiviruses, (lenti-, “related to slow”)Spumaviruses,(human foamy virus) Spumaviruses has not yet been definitely associated with disease in humans. Representatives of two major groups are considered in this chapter: the oncoviruses and the lentiviruses.,Members of the oncoviruses subgroup of retroviruses have long been associated with a variety of cancers in animals, including leukemias, lymphomas, and sarcomas, but until recent years had not been found to infect humans. The first human retrovirus, human T-cell leukemia virus type I(HTLV-1),was discovered in the late 1970s .It was shown to cause adult T-cell leukemia, a rare malignancy found only in Japan, Africa, and the Caribbean. A relative of HTLV-1, HTLV-2,has been associated with a few rare cases of T-cell malignancies, including hairy cell leukemia, but its precise role in these diseases remains unclear.,Human Immunodeficiency Virus(HIV), The virus that causes AIDS First exposed in 1981 in central Africa, infection unknown Has killed more than 20 million people With 3.1 million people dying last year alone. Estimated 45 million people that we know of are currently living with HIV,The most important disease resulting from a human retrovirus infection,acquired immunodeficiency syndrome(AIDS), is caused by either of two lentviruses termed human immunodeficiency viruses types 1 and 2(HIV-1 and HIV-2). A devastating disease, for which there is no present cure.,Viruses are also etiologic factors in the development of several types of human tumors, including two of great significance worldwide-cervical cancer and liver cancer. At least 15% of all human tumors worldwide have a viral cause. These viruses are cancer associated viruses or human cancer viruses or tumor viruses.,HIV and AIDSan infectious agent,1979 - 5 cases of Pneumocystis carinii,With giemsa stain at high magnification, the faint bluish dot-like intracystic bodies of Pneumocystis carinii in lung are seen in this cytologic preparation from a bronchoalveolar lavage,In Los Angeles 1967-1978 only two cases of Pneumocystis carinii pneumonia,All Homosexual,HIV and AIDS,With dissemination to extrapulmonary sites, Pneumocystis carinii tends to produce foci with prominent calcification, as seen in the kidney here grossly.,HIV and AIDSan infectious agent Kaposis Sarcoma,Early 1981 MMWR: 5 cases of Kaposis sarcomaHitherto: rare (immunocompromization) 1981 - 26 cases of Kaposis sarcoma Young San Francisco and New York All Homosexuals,HIV is a retrovirus, a member of the lentivirus genus, and exhibits many of the physicochemical features typical of the family.The unique morphologic characteristic of HIV is a cylindrical nucleoid in the mature virion.The diagnostic barshaped nucleoid is visible in electron micrographs in those extracellular particles that happen to be section at the appropriate angle. The virion is about 100-120nm in diameter,and because it contains two copies of the RNA genome, it is diploid.,The RNA genome is coated with the nucleocapsid protein(NC),and the RNA-protein complexes are enclosed in a capsid (CA) composed of multiple subunits. Like all enveloped viruses, the membrane is acquired during budding from the host cell,but the surface glycoproteins(SU,also called gp120) and transmembrane glycoproteins(TM, also called gp 41)found in the envelope are virally encoded. In addition to the structural proteins,the virion core contains three virus specific proteins that are essential for viral replication: reverse transcriptase(RT),protease(PR),and integrase(IN).,The virus contains the three structure genes required for a replicating retrovirus-gag,pol,and env. Up to six additional genes regulate viral expression and are important in disease pathogenesis in vivo. HIV-1 contains, in addition to the gag,pol,and env genes, an array of other genes (tat,rev, vef,vif ,vpr,and vpu).Expression of these genes requires mRNA splicing,and all apparently encode proteins that serve regulatory or accessory roles during the infection. Tat is transcriptional activator that promotes synthesis of full-length viral transcripts. Rev promotes export of unspliced and partially spliced transcripts to cytoplasm. Vef down-regulates CD4 to promote virus release and also down-regulates MHC-I to interfere with immune recognition. Vpu targets CD4 destruction and virion release. Vpr promotes transport of subviral particles into nucleus of nondividing cells. Vpu and Vif increase efficiency of in fection and yield of virus. Activation of CD4 T lymphocytes virus increases virus production.,The regions of greatest divergence among different isolates are localized to the env gene, which codes for the viral envelope proteins.The SU (gp120) product of the env gene contains binding domains responsible for virus attachment to the CD4 molecule and coreceptors, determines lymphocyte and macrophage tropisms, and carries the major antigenic determinants that elicit neutralizing antibodies.The TM(gp41) env product contains both a transmembrane domain that anchors the glycoprotein in the viral envelope and a fusion domain that facilitates viral penetration into target cells.The divergence in the envelope of HIV complicates efforts to develop an effective vaccine for AIDS.,Major retroviral genes and proteins of HIV,Surface glycoprotein,Transmembrane protein,matrix,cpsid,nucleocapsid,Reverse transcriptase,Virus replication,The virions adsorb to cellular membrane receptors and enter the cell by direct fusion with the plasma membrane. For HIV -1, the virion attachment protein is the SU glycoprotein gp120, and the cellular receptor is the CD4 molecule. All primate lentiviruses use as a receptor the CD4 molecule, which is expressed on macrophages and T lymphocytes. A second coreceptor in addition to CD4 is necessary for HIV-1to gain entry to cells.The second receptor is required for fusion of the virus with the cell membrane .,The virus first binds to CD4 and then to the coreceptor.These interactions cause conformational changes in the viral envelope, activating the gp41 fusion peptide and triggering membrane fusion. The HIV-1transmembrane TM protein gp 41 is responsible for fusion of the viral and cell membranes, leading to entry of the virion core complex into the cytoplasm of the cell.,Fusion activity may also play an important role in amplification of the effects of the virus infection,particularly during the later stages of the infection,because infected cells expressing viral glycoproteins in their membranes readily fuse with uninfected CD4+T lymphocytes to form large syncytia.This process appears to provide a means for cell-to-cell transmission of the virus that bypasses the usual extracellular phase and may contribute to the overall depletion of CD4 lymphocytes in an infected individual.,Soon after entry of the viral core into the cytoplasm of the infected cell,the RNA is copied into double-stranded DNA by reverse transcriptase,the virion-associated DNA polymerase. The overall processes referred to as reverse transcriptase and results in a linear DNA molecule that enters the nucleus and integrates more-or-less at random into a host cell chromosome. Once the viral genetic information has been converted to DNA and integrated,it essentially becomes part of the cellular genome.The viral genes,called the provirus, are therefore replicated and faithfully inherited as long as the infected cell continues to divide. Special sequences contained within the RNA are duplicated during the reverse transcription prosess so that the integrated provirus contains identical long terminal repeats(LTRs) at its ends.,The LTR sequences contain the appropriate promoter, enhancer,and other signals required for transcription of the viral genes by the host RNA polymerase II. DNA polymerase activity, the reverse transcriptase possesses an RNase H activity that is responsible for degrading the RNA portion of the DNA-RNA hybrid(RNA/DNA) produced in the first phase of reverse transcription. The immediate product of reverse transcription is a linear double-stranded DNA molecule that is flanked by the LTR sequences. The viral integrase(IN) catalyzes the integration of the linear DNA into host DNA.,The choice of a target site for integration into the cellular DNA appears, however, to be nearly random. The replication process is completed by transcription of the proviral DNA by the host RNA polymerase II . Virus particles mature and emerge from infected host cells by budding from cytoplasmic membranes. The viral protease then cleaves the Gag and Pol proteins from the precursor polyprotein ,producing an infectious virion prepared for reverse transcription when the next cell is infected.,Replication,HIV Viruse Classification,Lentiviruses have been isolated from many species including at least 26 different African nonhuman primate species. There are two distinct types of human AIDS viruses:HIV-1 and HIV-2.The two types are distinguished on the basis of genome organization and phylogenetic (evolutionary) relation-ship with other primate lentiviruses.,Variation,HIV-1 possesses the most error-prone reverse transcriptase. The consequence of this high error rate is that each time the viral RNA is reverse transcribed, one to two new mutations are introduced into the resulting DNA . Because the process of transcription of the integrated proviral DNA to produce new viral genomes is also error prone, mutant genomes accumulate rapidly over the course of an infection.,The end result is a quasi-species that accounts for the many nucleotide differences observed between different isolates (even from the same infect individual) and for the variability of the SU envelope protein gp120. It may explain, in part, the failure of the immune system to contral the infection and also the increases in viral virulence that appears to occur during the course of the infection,Disinfection and inactivation,HIV is completely inactivated by treatment for 10 minutes at room temperature with any of the following: 10% household bleach,50% ethanol, 35% isopropanol,1% Nonidet P40, 0.5% lysol, 0.5% paraformaldehyde, or 0.3% hydrogen peroxide. The virus is also inactivated by extremes of pH (pH 1.0, pH 1.3). However, when HIV is present in clotted or unclotted blood in a needle or syringe, exposure to undiluted bleach for at least 30 seconds is necessary for inactivation. HIV is readily inactivated in liquids or 10% serum by heating at 56 for 10 minutes, but dried proteinaceous material affords marked protection.,Pathogenesis and symptomatology,Pathogenesis and pathology The typical course of untreated HIV infection spans about a decade. Stages include the primate infection, dissemination of virus to lymphoid organs, clinical latency, elevated HIV expression, clinical disease, and death. The duration between primary infection and progression to clinical disease averages about 10 yesrs. In untreated cases, death usually occurs within 2 years after the onset of clinical symptoms. Following primary infection ,there is a 4-to 11-day period between mucosal infection and initial viremia; the viremia is detectable for about 8-12 weeks. Vrius is widely disseminated throughout the body during this time, and the lymphoid organs become seeded.,An acute mononucleosis-like syndrome develops in many patients(50%-75%)3-6weeks after primary infection. There is a significant drop in numbers of circulating CD4+ T cells at this early time. An immune response to HIV occurs 1 week to 3 months after infection,plasma viremia drops, and levels of CD4 cells rebound however, the immune response is unable to clear the infection completely, and HIV-infected cells persist in the lymph nodes. This period of clinical latency may last for as long as 10 years. During this time, there is a high level of ongoing viral replication. It is estimated that 10 billion HIV particles are produced and destroyed each day. Eventually, the patient will develop constitutional symptoms and clinically apparent disease, such as opportunistic infections or neoplasms.,B Clinical features Symptoms of acute HIV infection are nonspecific and include fatigue, rash, headache, nausea, and night sweats. AIDS is characterized by pronounce suppression of the immune system and development of a wide variety of severe opportunistic infections or unusual neoplasms. The more serious symptoms in adults are often preceded by a prodtone (“diarrhea and dwindling”) that can include fatigue, malaise, weight loss, fever, shortness of breath, chronic diarrhea, white patches on the tongue(hairy leukoplakia, oral candidiasis) disease symptoms in the gastrointestinal tract from the esophagus to the colon are a major cause of debility.,The predominant causes of morbidity and mortality among patients with late-stage HIV infection are opportunistic infections, i.e. severe infections induced by agents that rarely cause serious disease in immune competent individuals. Opportunistic infections usually do not occur in HIV-infected patients until CD4+ T cells counts have dropped from the normal level of about 1000cells/L to less than 200 cells/L.,AIDS patients exhibit a marked predisposition to the development of cancer, another consequence of immune suppression. AIDS-associated cancers include non-Hodgkin,s lymphoma ( both systemic and central nervous system types), Kaposi,s sarcoma, cervical cancer, anogenital cancers, and Hodgkin,s lymphoma Kaposi,s sarcoma, is now 20,000 times more common in untreated AIDS patients than in the general population. Kaposi,s sarcoma,associated herpesvirus, or HHV8,appear to be causally related to be cancer.,The cardinal feature of HIV infection is the depletion of T helper-inducer lymphocytes-the result of HIV replication in this population of lymphocytes as well as the death of uninfected T cells by indirect mechanisms. The T cells express the CD4 phenotypic marker on their surface. The CD4 molecule is the major receptor for HIV; it has a high affinity for the viral envelope. The HIV coreceptor on lymphocytes is the CXCR4 chemokine receptor. Monocytes and macrophages play a major role in the dissemination and pathogenesis of HIV infection. Curtain subsets of monocytes express the CD4 surface antigen and therefore bind to the envelope of HIV. Unlike the CD4 T lymphocyte, the monocyte is relatively refractory to the cytopathic effects of HIV, so that the virus not only can survive in this cell but also can be transported to various organs in the body (such as the lungs and brain).,Infected macrophages may continue to produce virus for a long period of time. The HIV coreceptor on monocytes and macrophages is the CCR5 chemokine receptor. In the brain, the major cell types infected with HIV appear to be the monocytes and macrophages, and this may have important consequences for the development of neuropsychiatric manifestations associated with HIV infection. Infected pulmonary alveolar macrophages may play a role in the interstitial pneumonitis seen in certain patients with AIDS.,C. Immunity HIV-infected persons develop both humoral and cell mediated responses against HIV-related antigens. Antibodies to a number of viral antigens develop soon after infection. Most infected individuals make neutralizing antibodies against HIV, directed against the envelope glycoprotein. However ,the levels of neutralizing activity are low; many anti-envelope antibodies are nonneutralizing. It is believed that the dense glycosylation may inhibit binding of neutralizing antibody to the envelope protein. The envelope glycoprotein shows great sequence variability. This natural variation may allow the evolution of successive of resistant virus that escape recognition by existing neutralizing by neutralizing antibodies.,Laboratory diagnosis,Evidence of infection by HIV can be detected in three ways: a) virus isolation, b) serologic determination of antiviral antibodies, and c) measurement of viral nucleic acid or antigens.,Virus isolation HIV can be cultured from lymphocytes in peripheral blood. The most sensitive virus isolation technique is to cocultivate the test sample with uninfected, mitogen-stimulated peripheral blood mononuclear cells. The vast majority of HIV-1 antibody-positive persons will have virus that can be cultured from their blood cells. However, virus isolation techniques are time consuming and laborious and are limited to research studies. PCR amplification techniques are more commonly used for detection of virus in clinical specimens.,B. Serology Most individuals will have detectable antibodies within 6-12 weeks after infection, whereas virtually all will be positive within 6 months. Test kits are commercially available for measuring antibodies by enzyme-linked immunoassay(EIA). If properly performed, these test have a sensitivity and specificity exceeding 98%. antibodies to viral core protein p24 or envelope glycoprotein gp41, gp120, or gp160 are most commonly detected. simple, rapid tests for detecting HIV antibodies are available for use in laboratories ill-equipped to perform EIA test. The simple tests are based on principles such as agglutination or immunodot reactions.,C. Detection of viral nucleic acid or antigens Amplification assays such as the RT-PCR, DNA PCR, AND bDNA tests are commonly used to detect viral RNA in clinical specimens. The HIV RNA levels are important predictive markers of disease progression and valuable tools with which to monitor the effectiveness of antiviral therapies.,Prevention and treatment,Transmission route The HIV virus is transmitted between humans in three ways: sexually, perinatally, and by exposure to contaminated blood or body fluids. Th