Tang B, Wang YM, Liu J, Zhang R. Detection of hepatitis B virus cccDNA with modified polymerase chain reaction.
Shijie Huaren Xiaohua Zazhi 2005;
13:2188-2192. [DOI:
10.11569/wcjd.v13.i18.2188]
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Abstract
AIM: To establish a simple and fast hepatitis B virus covalently closed circular DNA(cccDNA) detecting method based on polymerase chain reaction(PCR) with satisfactory sensitivity and specificity.
METHODS: The cccDNA and the relaxed circular DNA (rcDNA) were extracted from HepG2.2.15 cells and supernatant, respectively, and then purified. Two pairs of specific PCR primes were designed to cover the single strand area of rcDNA. And two pairs of non-specific PCR primes were designed to cover the double strand area of rcDNA. Before and after digested by single-strand-specific mung bean nuclease(MBN), cccDNA and rcDNA samples were amplified by specific primes and non-specific primes. Whether the digested cccDNA can be amplified by specific primes, without amplifying the digested rcDNA, was observed. The PCR parameters such as substrate amount and circulation times were changed during amplification. The HBV genome plasmid was used as control; and the HBV samples from patient with hepatitis B was used for practical test.
RESULTS: Different amounts of rcDNA template were amplified by specific and non-specific primes. More than 104 and 102 rcDNA template molecules were amplified by two pairs of specific and non-specific primes, respectively. The specific primes could not discriminate between rcDNA and cccDNA when the template molecules were overabundant. Before and after the digestion by MBN, different amounts of cccDNA were amplified by specific and non-specific primes; and after the digestion, rcDNA templates were amplified by non-specific primes, but not by specific primes. With this strategy, we found the virus samples from the serum of the patient with chronic hepatitis B contained mainly rcDNA and a small quantity of cccDNA, while the samples from hepatocytes contained mainly cccDNA.
CONCLUSION: The combination of MBN selective digestion and specific PCR amplification of the cccDNA is a simple, fast, sensitive and specific method for the detection of HBV cccDNA.
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