人疱疹病毒6型荧光定量分型方法的建立和临床应用

Objective Human herpesvirus 6(HHV-6)isolates are classified into two variants,HHV-6A and HHV-6B,based on distinct genetic,antigenic and biological characteristics.HHV-6 has been associated with encephalitis in children recently.This study aireed to estabhsh a real time PCR assay for simultaneous detection of the two subtypes of HHV-6,and apply this new assay to children with suspected encephalitis,then analyze the relationship between the infeetion with HHV-6 and encephalitis in children.Method The universal primers and variant-specific TaqMan probes were designed based on the highly conserved sequences of the DNA polymerase gene(U38)of HHV-6.The 5'end of the probes for HHV-6A and HHV-6B was labeled with the fluoreseein reporter tetrachloro-6-carboxyfluorescein and 6-earboxyfluorescein(6-FAM),separately,while the 3'end were quenched with 6-carboxy-tetramethyl-rhedamine.The real time PCR assay for simultaneous detection of HHV-6A and HHV-6B was established.Then,the plasmids of HHV-6A and -6B which were diluted by a 10-fold series from 109 to 10°copies/μl,together with controls were used for testing both sensitivity and specificity of the real time PCR assay.The cerebrospinal fluid(CSF) specimens from 445 cases of suspected encephalitis were tested with this real time PCR and positive samples were then sequenced.Result Both HHV6A(strain ZJ-159)and HHV-6B (strain GS)were positive on the real time PCR assay.There were no cross-reaction with herpes simplex virus type 1,type 2(HSV-1,HSV-2),varicella-zoster virus(YZV),cytomegalovirus(CMV),EpsteinBarr virus(EBV),hepatitis B virus,Staphylococcus aureus,Mycoplasma pneumoniae and human DNA.A linear regression curve was obtained when plotting Ct values against the log10 of the viral DNA input for both subtypes of HHV-6.The sensitivity threshold was 10 copies/μl for the real time PCR.HHV-6 positive rate by the real time PCR assay was 4.72%(21/445),including 4 ca8es with HHV-6A infection,16 cases of HHV-6B infeedon and l case with mixed HHV-6A and HHV-6B infeetion.The new PCR assay usually took 2 to 3 hours to provide results.Conclusion This new real time PCR assay call simultaneously detect both subtypes of HHV-6,and have high specificity and sensitivity.It will pmvide an early and sensitive diagnosis of HHV-6 encephalitis in children.

Establishment and clinical application of a new real time PCR assay for simultaneous detection of human herpesvirus-6A and human herpesvirus-6B