Lamivudine: A reverse transcriptase inhibitor and ZALCITABINE analog in which a sulfur atom replaces the 3' carbon of the pentose ring. It is used to treat HIV disease.Reverse Transcriptase Inhibitors: Inhibitors of reverse transcriptase (RNA-DIRECTED DNA POLYMERASE), an enzyme that synthesizes DNA on an RNA template.Hepatitis B, Chronic: INFLAMMATION of the LIVER in humans caused by HEPATITIS B VIRUS lasting six months or more. It is primarily transmitted by parenteral exposure, such as transfusion of contaminated blood or blood products, but can also be transmitted via sexual or intimate personal contact.Organophosphonates: Carbon-containing phosphonic acid compounds. Included under this heading are compounds that have carbon bound to either OXYGEN atom or the PHOSPHOROUS atom of the (P=O)O2 structure.Hepatitis B virus: The type species of the genus ORTHOHEPADNAVIRUS which causes human HEPATITIS B and is also apparently a causal agent in human HEPATOCELLULAR CARCINOMA. The Dane particle is an intact hepatitis virion, named after its discoverer. Non-infectious spherical and tubular particles are also seen in the serum.Antiviral Agents: Agents used in the prophylaxis or therapy of VIRUS DISEASES. Some of the ways they may act include preventing viral replication by inhibiting viral DNA polymerase; binding to specific cell-surface receptors and inhibiting viral penetration or uncoating; inhibiting viral protein synthesis; or blocking late stages of virus assembly.Hepatitis B e Antigens: A closely related group of antigens found in the plasma only during the infective phase of hepatitis B or in virulent chronic hepatitis B, probably indicating active virus replication; there are three subtypes which may exist in a complex with immunoglobulins G.Adenine: A purine base and a fundamental unit of ADENINE NUCLEOTIDES.Drug Resistance, Viral: The ability of viruses to resist or to become tolerant to chemotherapeutic agents or antiviral agents. This resistance is acquired through gene mutation.Anti-HIV Agents: Agents used to treat AIDS and/or stop the spread of the HIV infection. These do not include drugs used to treat symptoms or opportunistic infections associated with AIDS.Zidovudine: A dideoxynucleoside compound in which the 3'-hydroxy group on the sugar moiety has been replaced by an azido group. This modification prevents the formation of phosphodiester linkages which are needed for the completion of nucleic acid chains. The compound is a potent inhibitor of HIV replication, acting as a chain-terminator of viral DNA during reverse transcription. It improves immunologic function, partially reverses the HIV-induced neurological dysfunction, and improves certain other clinical abnormalities associated with AIDS. Its principal toxic effect is dose-dependent suppression of bone marrow, resulting in anemia and leukopenia.Stavudine: A dideoxynucleoside analog that inhibits reverse transcriptase and has in vitro activity against HIV.Hepatitis B: INFLAMMATION of the LIVER in humans caused by a member of the ORTHOHEPADNAVIRUS genus, HEPATITIS B VIRUS. It is primarily transmitted by parenteral exposure, such as transfusion of contaminated blood or blood products, but can also be transmitted via sexual or intimate personal contact.Dideoxynucleosides: Nucleosides that have two hydroxy groups removed from the sugar moiety. The majority of these compounds have broad-spectrum antiretroviral activity due to their action as antimetabolites. The nucleosides are phosphorylated intracellularly to their 5'-triphosphates and act as chain-terminating inhibitors of viral reverse transcription.Drug Therapy, Combination: Therapy with two or more separate preparations given for a combined effect.DNA, Viral: Deoxyribonucleic acid that makes up the genetic material of viruses.Nevirapine: A potent, non-nucleoside reverse transcriptase inhibitor used in combination with nucleoside analogues for treatment of HIV INFECTIONS and AIDS.HIV Infections: Includes the spectrum of human immunodeficiency virus infections that range from asymptomatic seropositivity, thru AIDS-related complex (ARC), to acquired immunodeficiency syndrome (AIDS).Alanine Transaminase: An enzyme that catalyzes the conversion of L-alanine and 2-oxoglutarate to pyruvate and L-glutamate. (From Enzyme Nomenclature, 1992) EC 2.6.1.2.Benzoxazines: OXAZINES with a fused BENZENE ring.Hepatitis B Surface Antigens: Those hepatitis B antigens found on the surface of the Dane particle and on the 20 nm spherical and tubular particles. Several subspecificities of the surface antigen are known. These were formerly called the Australia antigen.Viral Load: The quantity of measurable virus in a body fluid. Change in viral load, measured in plasma, is sometimes used as a SURROGATE MARKER in disease progression.Indinavir: A potent and specific HIV protease inhibitor that appears to have good oral bioavailability.Didanosine: A dideoxynucleoside compound in which the 3'-hydroxy group on the sugar moiety has been replaced by a hydrogen. This modification prevents the formation of phosphodiester linkages which are needed for the completion of nucleic acid chains. Didanosine is a potent inhibitor of HIV replication, acting as a chain-terminator of viral DNA by binding to reverse transcriptase; ddI is then metabolized to dideoxyadenosine triphosphate, its putative active metabolite.HIV-1: The type species of LENTIVIRUS and the etiologic agent of AIDS. It is characterized by its cytopathic effect and affinity for the T4-lymphocyte.PyrimidinonesNucleosides: Purine or pyrimidine bases attached to a ribose or deoxyribose. (From King & Stansfield, A Dictionary of Genetics, 4th ed)Oxazines: Six-membered heterocycles containing an oxygen and a nitrogen.Treatment Outcome: Evaluation undertaken to assess the results or consequences of management and procedures used in combating disease in order to determine the efficacy, effectiveness, safety, and practicability of these interventions in individual cases or series.Drug Resistance, Multiple, Viral: The ability of viruses to resist or to become tolerant to several structurally and functionally distinct drugs simultaneously. This resistance phenotype may be attributed to multiple gene mutation.Hepatitis B Antibodies: Antibodies to the HEPATITIS B ANTIGENS, including antibodies to the surface (Australia) and core of the Dane particle and those to the "e" antigens.Antiretroviral Therapy, Highly Active: Drug regimens, for patients with HIV INFECTIONS, that aggressively suppress HIV replication. The regimens usually involve administration of three or more different drugs including a protease inhibitor.Gene Products, pol: Retroviral proteins coded by the pol gene. They are usually synthesized as a protein precursor (POLYPROTEINS) and later cleaved into final products that include reverse transcriptase, endonuclease/integrase, and viral protease. Sometimes they are synthesized as a gag-pol fusion protein (FUSION PROTEINS, GAG-POL). pol is short for polymerase, the enzyme class of reverse transcriptase.Treatment Failure: A measure of the quality of health care by assessment of unsuccessful results of management and procedures used in combating disease, in individual cases or series.Nelfinavir: A potent HIV protease inhibitor. It is used in combination with other antiviral drugs in the treatment of HIV in both adults and children.Zalcitabine: A dideoxynucleoside compound in which the 3'-hydroxy group on the sugar moiety has been replaced by a hydrogen. This modification prevents the formation of phosphodiester linkages which are needed for the completion of nucleic acid chains. The compound is a potent inhibitor of HIV replication at low concentrations, acting as a chain-terminator of viral DNA by binding to reverse transcriptase. Its principal toxic side effect is axonal degeneration resulting in peripheral neuropathy.GuanineLopinavir: An HIV protease inhibitor used in a fixed-dose combination with RITONAVIR. It is also an inhibitor of CYTOCHROME P-450 CYP3A.Mutation: Any detectable and heritable change in the genetic material that causes a change in the GENOTYPE and which is transmitted to daughter cells and to succeeding generations.HIV Reverse Transcriptase: A reverse transcriptase encoded by the POL GENE of HIV. It is a heterodimer of 66 kDa and 51 kDa subunits that are derived from a common precursor protein. The heterodimer also includes an RNAse H activity (RIBONUCLEASE H, HUMAN IMMUNODEFICIENCY VIRUS) that plays an essential role the viral replication process.Ritonavir: An HIV protease inhibitor that works by interfering with the reproductive cycle of HIV. It also inhibits CYTOCHROME P-450 CYP3A.CD4 Lymphocyte Count: The number of CD4-POSITIVE T-LYMPHOCYTES per unit volume of BLOOD. Determination requires the use of a fluorescence-activated flow cytometer.Liver Transplantation: The transference of a part of or an entire liver from one human or animal to another.Interferon-alpha: One of the type I interferons produced by peripheral blood leukocytes or lymphoblastoid cells. In addition to antiviral activity, it activates NATURAL KILLER CELLS and B-LYMPHOCYTES, and down-regulates VASCULAR ENDOTHELIAL GROWTH FACTOR expression through PI-3 KINASE and MAPK KINASES signaling pathways.Dideoxynucleotides: The phosphate esters of DIDEOXYNUCLEOSIDES.Recurrence: The return of a sign, symptom, or disease after a remission.HIV Protease Inhibitors: Inhibitors of HIV PROTEASE, an enzyme required for production of proteins needed for viral assembly.Hepatitis B Core Antigens: The hepatitis B antigen within the core of the Dane particle, the infectious hepatitis virion.Liver Cirrhosis: Liver disease in which the normal microcirculation, the gross vascular anatomy, and the hepatic architecture have been variably destroyed and altered with fibrous septa surrounding regenerated or regenerating parenchymal nodules.RNA, Viral: Ribonucleic acid that makes up the genetic material of viruses.Virus Activation: The mechanism by which latent viruses, such as genetically transmitted tumor viruses (PROVIRUSES) or PROPHAGES of lysogenic bacteria, are induced to replicate and then released as infectious viruses. It may be effected by various endogenous and exogenous stimuli, including B-cell LIPOPOLYSACCHARIDES, glucocorticoid hormones, halogenated pyrimidines, IONIZING RADIATION, ultraviolet light, and superinfecting viruses.Cytidine Triphosphate: Cytidine 5'-(tetrahydrogen triphosphate). A cytosine nucleotide containing three phosphate groups esterified to the sugar moiety.Arabinofuranosyluracil: A pyrimidine nucleoside formed in the body by the deamination of CYTARABINE.Immunoglobulins: Multi-subunit proteins which function in IMMUNITY. They are produced by B LYMPHOCYTES from the IMMUNOGLOBULIN GENES. They are comprised of two heavy (IMMUNOGLOBULIN HEAVY CHAINS) and two light chains (IMMUNOGLOBULIN LIGHT CHAINS) with additional ancillary polypeptide chains depending on their isoforms. The variety of isoforms include monomeric or polymeric forms, and transmembrane forms (B-CELL ANTIGEN RECEPTORS) or secreted forms (ANTIBODIES). They are divided by the amino acid sequence of their heavy chains into five classes (IMMUNOGLOBULIN A; IMMUNOGLOBULIN D; IMMUNOGLOBULIN E; IMMUNOGLOBULIN G; IMMUNOGLOBULIN M) and various subclasses.Infectious Disease Transmission, Vertical: The transmission of infectious disease or pathogens from one generation to another. It includes transmission in utero or intrapartum by exposure to blood and secretions, and postpartum exposure via breastfeeding.2-Aminopurine: A purine that is an isomer of ADENINE (6-aminopurine).Therapeutic Equivalency: The relative equivalency in the efficacy of different modes of treatment of a disease, most often used to compare the efficacy of different pharmaceuticals to treat a given disease.Drug Administration Schedule: Time schedule for administration of a drug in order to achieve optimum effectiveness and convenience.Anti-Retroviral Agents: Agents used to treat RETROVIRIDAE INFECTIONS.Drug Resistance, Microbial: The ability of microorganisms, especially bacteria, to resist or to become tolerant to chemotherapeutic agents, antimicrobial agents, or antibiotics. This resistance may be acquired through gene mutation or foreign DNA in transmissible plasmids (R FACTORS).Polyethylene Glycols: Polymers of ETHYLENE OXIDE and water, and their ethers. They vary in consistency from liquid to solid depending on the molecular weight indicated by a number following the name. They are used as SURFACTANTS, dispersing agents, solvents, ointment and suppository bases, vehicles, and tablet excipients. Some specific groups are NONOXYNOLS, OCTOXYNOLS, and POLOXAMERS.