Figure 1. Genetic structure of the DNA provirus of HIV-1 showing the major open reading frames, gag, pol and env, and the accessory and regulatory genes, vpu, vif, vpr, nef, tat and rev. The 5¢ long terminal repeat acts as a promoter and the 3¢ long terminal repeat as the polyadenylation sequence. Three families of messenger RNAs are produced, a full-length version which is either singly or multiply spliced as shown. is the packaging signal sequence allowing encapsidation of the vector RNA into the viral particle. SD: major splice donor.

Figure 2. Infection and virus production in a single cell. Bold arrows demonstrate transport events and dotted arrows represent transport and regulatory functions. Numbers set events chronologically, although many processes overlap: 1, binding of gp120 to CD4 on the cell surface; 2, coreceptor binding and membrane fusion; 3, entry of viral capsid and subsequent uncoating, reverse transcription begins; 4, completion of reverse transcription and formation of preintegration complex (PIC); 5, translocation of PIC across nuclear membrane through pore complexes; 6, integration of viral genome into host DNA; 7, generation of multiply spliced viral transcripts; 8, production of viral regulatory proteins at rough endoplasmic reticulum (ER); 9, exponential increase of viral transcription mediated by Tat protein; 10, downregulation of surface CD4 by the action of Nef protein; 11, production of singly spliced mRNA by the action of Rev protein; 12, production of viral Env protein on rough ER; 13, production of unspliced genomic mRNA by the action of Rev protein; 14, production of viral structural and replication proteins on polysomes; 15, transport of viral Env protein to cell membrane and cleavage by host cell proteases; 16, packaging of genomic mRNAs into nascent virion at plasma membrane; 17, budding of immature viral particle from cell surface; 18, maturation of virion into infectious particle mediated by viral protease. (Reproduced from Lever, AML and Griffin, SDC (2001) HIV: future and futuristic therapies. Journal of HIV Therapy 6(4): 85–90. Published by Mediscript Limited, London, UK with permission.)

Figure 3. Examples of vector design. 1: Minimal vector showing the position of the packaging signal () and polypurine tract (ppt). Long terminal repeats (LTRs) act as promoter and polyadenylation signals. 2: Vector with RNA nuclear export signal; RRE, Rev response element. 3: Self-inactivating vector. Mutation in U3 copied to the 5¢ LTR inactivates the LTR promoter. The internal promoter alone (Pro) is active in the transduced vector. 4: Dual gene vector. One gene driven from LTR and the second from the internal promoter or internal ribosome entry site (IRES).

Figure 4. Subdivision of the HIV ORFs into separate expressors for packaging lentiviral vector RNA indicates a heterologous promoter distinct from the retroviral LTR. VSV: vesicular stomatitis virus.