Background The prevalence of donors seropositive for hepatitis B virus (HBV) surface antigen (HBsAg) in China is estimated to be about 10%. There have been two cases, published so far, where HBV was suspected to have been transmitted by penetrating keratoplasty. Currently, infection of the donors with HBV is excluded in most cornea banks by serological testing of the cadaveric serum only. Serological testing of cadaveric serum is not a reliable method for screening of potential cornea donors, and may not be sufficient for the virus safety of cornea grafts. And no data are available about the amount of HBV genomes in ocular tissues of donors with HBV infection. Therefore, other screening strategies such as detection of viral nucleic acids by PCR should be evaluated. This study was to evaluate the detectability of HBV-DNA in the ocular tissues of donors tested seropositive for HBsAg in an attempt to obtain information as to the potential infectivity of this donor material.
Method Real-time quantitative PCR (QPCR) has been proven to be a powerful tool for quantifying specific target DNA sequences. We optimized QPCR for quantifying ocular HBV-DNA and analyzed tissue DNA extracts from 2 HBsAg-positive and 4 HBsAg-negative individuals. Aqueous humor DNA extracts from 15 HBsAg-positive and 18 HBsAg-negative individuals were also detected for HBV DNA.
Results Viral genomes could not be detected in the Aqueous humor and vitreous by QPCR at a detection limit of 500 copies/ml. In seropositive donors, HBV genomes per microgram of DNA were 1716 to 2968 (cornea), 1070 to 17812 (limbus), 1333 to 5625 (conjunctiva), 1541 to 2482 (sclera), 141 to 1333 (iris and ciliary body), 2939 to 5698 (choroid), 128 to 365 (retina), and 4807 to 23343 (extraocular muscles). Viral genomes could not be detected in the HBsAg-negative donors.
Conclusions This study confirmed that HBV can be present in many ocular tissues. The possibility of HBV transmission through corneal transplantation should not be overlooked. Eye banks should continue to screen donors for HBV. This preliminary study could be an encouraging step for further researches to evaluate the possibility of the avascular cornea to carry HBV.