[PCR amplification, cloning and expression of the gene coding for CD4 V1-V2 domains].

We describe the use of a modified technique of polymerase chain reaction (PCR) for facilitating cloning and expression of a cDNA fragment encoding CD4 V1-V2 domains. The modification includes introducing suitable signals to start primer and halt primer of the target gene as indicated in Fig. 1. After verified by DNA sequencing, the amplified DNA fragment was cloned into prokaryotic expression vectors containing lambda PL promoter. The screened clones were induced to express the target fragment V1-V2 of CD4 gene and the expected gene product was estimated to be 8% or 10% of the total cellular proteins.