R5-Tropic Virus
Also known as M-tropic virus. A strain of HIV that uses the chemokine receptor CCR5 as a co-receptor to bind to and infect human cells. HIV is usually R5 tropic early on in infection, but the virus can switch to using a different co-receptor as the disease progresses.
See Also:   X4-Tropic Virus
                   CCR5
                   Co-Receptor

Randomized Trial
A type of clinical trial in which participants are assigned by chance to one of two or more treatment or placebo groups. A randomized trial design helps researchers gather meaningful information and make valid statistical calculations.
See Also:   Clinical Trial
                   Placebo

Rapid Test
A type of HIV-1 ELISA test that can detect antibodies to HIV in the blood in less than 30 minutes with greater than 99% sensitivity and specificity. A positive rapid test result should be confirmed by an HIV Western blot test.
See Also:   Enzyme-Linked Immunosorbent Assay
                   Western Blot

Rebound
See:    Viral Rebound

Receptor
A protein on the surface of a cell that serves as a binding site for substances outside the cell, such as HIV floating free in the blood.
See Also:   Co-Receptor
                   CD4 Receptor

Recombinant
Produced by genetic engineering. Also refers to a new organism or compound produced by inserting the genetic material of one organism into the genetic material of another organism.
See Also:   Genetic Engineering

Refractory
Refers to a disease or condition that has gotten worse despite treatment.

Remission
The period during which symptoms of a disease diminish or disappear. In people infected with HIV, effective treatment regimens may result in the remission of HIV-associated symptoms and conditions.

Renal
Pertaining to the kidneys.

Rescue Therapy
See:    Salvage Therapy

Resistance
See:    Drug Resistance

Resistance Testing
A laboratory test to determine if an individual's HIV strain is resistant to any anti-HIV drugs.
See Also:   Genotypic Assay
                   Phenotypic Assay
                   Drug Resistance

Retinal Detachment
Separation of the retina from the inner wall of the eye. Retinal detachment can be a complication of cytomegalovirus (CMV) retinitis and can cause vision loss.
See Also:   Cytomegalovirus Retinitis

Retinitis
Inflammation of the retina, the thin layer of tissue that lines the inside back wall of the eye and functions like the film of a camera. In people with HIV, retinitis can be caused by cytomegalovirus (CMV). If untreated, retinitis can lead to blindness. Symptoms include floating spots, flashing lights, blind spots, and blurred vision.
See Also:   Cytomegalovirus
                   Cytomegalovirus Retinitis

Retrovirus
A type of virus that stores its genetic information in a single-stranded RNA molecule, then constructs a double-stranded DNA version of its genes using a special enzyme called reverse transcriptase. The DNA copy is then integrated into the host cell's own genetic material. HIV is an example of a retrovirus.
See Also:   Reverse Transcriptase
                   Integration
                   Provirus

Reverse Transcriptase (RT)
An enzyme found in HIV and other retroviruses. RT converts single-stranded HIV RNA into double-stranded HIV DNA. Some anti-HIV drugs interfere with this stage of HIV's life cycle.
See Also:   Nucleoside Reverse Transcriptase Inhibitors
                   Non-Nucleoside Reverse Transcriptase Inhibitors
                   Provirus
                   Retrovirus

Reverse Transcriptase-Polymerase Chain Reaction (RT-PCR)
A laboratory test that measures the amount of HIV RNA (also known as viral load) in a blood sample by replicating HIV's genetic material to measurable levels. RT-PCR is the primary way that health care providers monitor HIV infection and its treatment.
See Also:   Polymerase Chain Reaction
                   Viral Load

Ribonucleic Acid (RNA)
Chemical structure that carries genetic instructions for protein synthesis. Although DNA is the primary genetic material of cells, RNA is the genetic material for some viruses.
See Also:   Deoxyribonucleic_Acid
                   Messenger RNA

RNA
See: Ribonucleic Acid

RT
See: Reverse Transcriptase

RT-PCR
See: Reverse Transcriptase-Polymerase Chain Reaction

Ryan White Care Act
The Ryan White Comprehensive AIDS Resources Emergency (CARE) Act is Federal legislation that addresses unmet health needs of people living with HIV/AIDS by funding primary health care and support services that enhance access to and retention in care. The CARE Act is administered by the Health Resources and Services Administration (HRSA).
See Also:   Health Resources and Services Administration