This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Human Immunodeficiency Virus, Subject name: Microbiology
Nef gene in HIV is for use: 
Select and explain. 
A. Enhancing the expression of genes, B. Enhancing viral replication, C. Decreasing viral replication, D. Maturation
C: Decreasing viral replication
Answer: C: Decreasing viral replication 
Explanation: Ans. is 'c' i.e., Decreasing viral replication(Ref: Ananthanarayan, 9th/e, and 8th/e, p. 571)Nef (Negative factor gene): Downregulating viral replication. QThe Nef protein increases viral infectivity, facilitates activation of resting T cells, and downregulates expression of CD4 and MHC class I. The Nef gene is necessary for simian immunodeficiency virus (SIV) to be pathogenic in monkeys. (Jawetz)