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[Detection of four human herpesviruses DNA and virus-specific IgM antibody in blood specimens of infants].

OBJECTIVE
To establish a restriction endonuclease pattern which could detect and differentiate four major human herpesviruses by polymerase chain reaction (PCR), restriction fragment length polymorphism (RFLP), DNA cloning and sequence analysis.


METHODS
A pair of primer, which was designed according to sequences in well-conserved regions of the DNA polymerase gene in human herpesviruses, was designed to amplify herpes simplex virus type 1 and 2 (HSVI/II), Epstein-Barr virus (EBV) and cytomegalovirus (CMV). Sequences of the primers are as follows: P(1) (5'-CGACTTTGCCAGCCTGACC-3') and P(2) (5'-AGTCCGTGTCCCCGTAGATG-3'). DNA of four strains of standard herpesviruses were amplified by PCR, and further studied by DNA cloning, sequence analysis and RFLP. At last, the authors established the PCR-RFLP technique to differentiate the four different herpesviruses. Meanwhile, 75 clinical blood specimens from infants with suspected viral infection and 38 blood specimens from healthy children were evaluated for herpesviruses DNA or virus-specific IgM antibody by PCR-RFLP or by ELISA.


RESULTS
The PCR amplified products of four human herpesviruses were from 510 bp to 592 bp in length and were analyzed for herpesvirus types with restriction endonuclease technique. The specificity and sensitivity of this PCR-RFLP were examined. There was no cross-reaction with Escherichia coli, Staphylococcus aureus, hepatitis B virus (HBV), Clostridium neoformans and human-genomic DNA and the lowest detection level was 0.1 fg DNA. Among 75 specimens, 23 were positive by PCR and the positive rate was 30.7%, including 13 for CMV, four for EBV, five for HSVII and one for HSVI after restriction enzyme digestion with BamHI and BstUI, while 10 were positive by ELISA and positive rate was 13.3%. All ELISA-positive specimens were likewise positive by PCR. Thirteen of 65 specimens that were ELISA-negative were tested positive by PCR. An infant with CMV infection was determined with viral DNA and virus-specific IgM antibody in blood at 3, 4 and 6 months after birth, respectively. The result showed that she was still CMV DNA-positive in blood whereas IgM antibody was positive only at month 3 after birth. None of the 38 control blood specimens was positive for herpesvirus by this PCR-RFLP or by ELISA.


CONCLUSIONS
This PCR-RFLP technique was specific, sensitive, rapid and accurate in diagnosing herpesviruses infection in infants, and it could detect herpesviruses DNA in specimens which were negative for IgM antibody by ELISA.