This question is about retroviruses and potential treatments.
Describe how Feline Immunodeficiency Virus (FIV), a retrovirus, replicates once inside feline helper T cells (THT_{\text{H}}TH cells).
Feline Immunodeficiency Virus (FIV) is a retrovirus that infects domestic cats. FIV binds to a primary receptor called CD134 on feline THT_{\text{H}}TH cells. Current management of FIV relies on supportive therapy or daily administration of antiretroviral drugs (such as AZT) to slow viral replication, but AZT can cause bone marrow suppression. Scientists investigated a new stem cell gene therapy (GT-134GT\text{-}134GT-134) to treat FIV-positive cats. GT-134GT\text{-}134GT-134 delivers a gene that knocks out the CD134 receptor gene in T-lymphocyte stem cells. Scientists conducted a study on two small groups of FIV-positive cats: Group A (4 cats) received the stem cell gene therapy along with a pre-treatment of low-dose whole-body radiation to deplete existing T cells; Group B (4 cats) received the stem cell gene therapy following a pre-treatment of chemotherapy; Both groups stopped AZT therapy 12 months after starting the gene therapy. At 24 months after stopping AZT therapy: 3 out of 4 cats in Group A and 2 out of 4 cats in Group B showed complete remission, with no detectable FIV RNA in their blood plasma and no FIV DNA in their THT_{\text{H}}TH cells; THT_{\text{H}}TH cells in the remission cats did not express the CD134 receptor; One cat from Group B died from chemotherapy-related toxicity during the study. Use the information provided to evaluate the use of stem cell gene therapy (GT-134GT\text{-}134GT-134) to treat FIV infections.
