Detection of herpes simplex virus DNA sequences in corneal transplant recipients by polymerase chain reaction assays

A serious adverse surgical event: Management of suspected HSV-1 keratitis in a donor cornea

PURPOSE

To describe the management of a serious adverse event in a patient undergoing penetrating keratoplasty (PK).

CASE REPORT

A 68-year-old man underwent PK for an aphakic bullous keratopathy following previous complicated cataract surgery. He had no past history of herpetic disease. Storage of the corneoscleral disc in the transport bottle precluded microscopic examination. After placement of the trephined donor cornea on the open eye of the recipient, a large dendritiform geographic ulcer was noted on the donor cornea. A replacement cornea was used after changing potentially contaminated instruments. Intravenous antiviral treatment was commenced intraoperatively to reduce the risk of infection to the central nervous system. Postoperatively, oral and topical antiviral treatment was commenced and 6 months following surgery the patient developed a geographic corneal ulcer at the graft host interface.

CONCLUSION

Containers to transport corneoscleral discs should enable microscopic examination by the surgeon prior to use. High dose systemic antivirals may reduce the risk of herpetic disease involving the posterior segment of the eye and neuroretina in the aphakic eye and spread to the central nervous system.

HSV1 latent transcription and non-coding RNA: A critical retrospective

Virologists have invested great effort into understanding how the herpes simplex viruses and their relatives are maintained dormant over the lifespan of their host while maintaining the poise to remobilize on sporadic occasions. Piece by piece, our field has defined the tissues in play (the sensory ganglia), the transcriptional units (the latency-associated transcripts), and the responsive genomic region (the long repeats of the viral genomes). With time, the observed complexity of these features has compounded, and the totality of viral factors regulating latency are less obvious. In this review, we compose a comprehensive picture of the viral genetic elements suspected to be relevant to herpes simplex virus 1 (HSV1) latent transcription by conducting a critical analysis of about three decades of research. We describe these studies, which largely involved mutational analysis of the notable latency-associated transcripts (LATs), and more recently a series of viral miRNAs. We also intend to draw attention to the many other less characterized non-coding RNAs, and perhaps coding RNAs, that may be important for consideration when trying to disentangle the multitude of phenotypes of the many genetic modifications introduced into recombinant HSV1 strains.

Frequency of dendritiform inflammatory cells in the cornea in herpetic anterior uveitis without clinical keratitis and Fuchs uveitis

Background

Herpetic anterior uveitis is a frequent cause of infectious uveitis. A definite diagnosis is obtained by anterior chamber puncture and polymerase chain reaction, an invasive procedure. We hypothesized that patients with herpetic anterior uveitis have a certain pattern of inflammatory cells in their cornea that distinguishes herpetic anterior uveitis from other uveitis types. This study is a prospective, controlled, observational study. Ten patients are with active herpetic anterior uveitis and 14 patients are with Fuchs uveitis syndrome. Patients were imaged with the Heidelberg Retina Tomograph with the Rostock Cornea Module attachment. Three images of the subepithelial area of the cornea were evaluated for dendritiform inflammatory cells. Means were calculated and used for analysis. The contralateral unaffected eyes and numbers published in the literature served as controls.

Results

The number of dendritiform inflammatory cells in herpetic anterior uveitis was compared to that in the Fuchs uveitis syndrome. Of the eyes of patients with herpetic anterior uveitis, 80% had an average of 98.0±10.8 cells/mm² (mean±standard error of the mean (SEM), n=10) in their affected eyes and 60.4±26.4 cells/mm², (n=6) in 30% of their fellow eyes. Patients with Fuchs uveitis syndrome had moderately elevated dendritiform inflammatory cells (47.0±9.7 cells/mm², n=14) in 96.4% of their affected eyes and normal numbers (23.0±7.3 cells/mm², n=13) in 46.4% of their fellow eyes. The difference between the four groups was significant (p=0.0004).

Conclusions

Patients with herpetic anterior uveitis had significantly higher levels of dendritiform inflammatory cells in their subepithelial cornea than patients with Fuchs uveitis syndrome, which can be detected by in vivo confocal microscopy. The clinically unaffected eyes of herpetic anterior uveitis patients showed a co-response regarding dendritiform inflammatory cell elevation. We conclude that high numbers of dendritiform inflammatory cells in the cornea of uveitis patients may support the clinical diagnosis of herpetic anterior uveitis.

Novel biotinylated lipid prodrugs of acyclovir for the treatment of herpetic keratitis (HK): transporter recognition, tissue stability and antiviral activity

PURPOSE

Biotinylated lipid prodrugs of acyclovir (ACV) were designed to target the sodium dependent multivitamin transporter (SMVT) on the cornea to facilitate enhanced cellular absorption of ACV.

METHODS

All the prodrugs were screened for in vitro cellular uptake, interaction with SMVT, docking analysis, cytotoxicity, enzymatic stability and antiviral activity.

RESULTS

Uptake of biotinylated lipid prodrugs of ACV (B-R-ACV and B-12HS-ACV) was significantly higher than biotinylated prodrug (B-ACV), lipid prodrugs (R-ACV and 12HS-ACV) and ACV in corneal cells. Transepithelial transport across rabbit corneas indicated the recognition of the prodrugs by SMVT. Average Vina scores obtained from docking studies further confirmed that biotinylated lipid prodrugs possess enhanced affinity towards SMVT. All the prodrugs studied did not cause any cytotoxicity and were found to be safe and non-toxic. B-R-ACV and B-12HS-ACV were found to be relatively more stable in ocular tissue homogenates and exhibited excellent antiviral activity.

CONCLUSIONS

Biotinylated lipid prodrugs demonstrated synergistic improvement in cellular uptake due to recognition of the prodrugs by SMVT on the cornea and lipid mediated transcellular diffusion. These biotinylated lipid prodrugs appear to be promising drug candidates for the treatment of herpetic keratitis (HK) and may lower ACV resistance in patients with poor clinical response.

2-[4,5-Difluoro-2-(2-fluorobenzoylamino)-benzoylamino]benzoic acid, an antiviral compound with activity against acyclovir-resistant isolates of herpes simplex virus types 1 and 2

Herpes simplex viruses 1 and 2 (HSV-1 and HSV-2) are responsible for lifelong latent infections in humans, with periods of viral reactivation associated with recurring ulcerations in the orofacial and genital tracts. In immunosuppressed patients and neonates, HSV infections are associated with severe morbidity and, in some cases, even mortality. Today, acyclovir is the standard therapy for the management of HSV infections. However, the need for novel antiviral agents is apparent, since HSV isolates resistant to acyclovir therapy are frequently isolated in immunosuppressed patients. In this study, we assessed the anti-HSV activity of the antiadenoviral compounds 2-[2-(2-benzoylamino)-benzoylamino]benzoic acid (benzavir-1) and 2-[4,5-difluoro-2-(2-fluorobenzoylamino)-benzoylamino]benzoic acid (benzavir-2) on HSV-1 and HSV-2. Both compounds were active against both viruses. Importantly, benzavir-2 had potency similar to that of acyclovir against both HSV types, and it was active against clinical acyclovir-resistant HSV isolates.

Ocular herpes simplex virus type 1: is the cornea a reservoir for viral latency or a fast pit stop?

PURPOSE

To present a review supporting and refuting evidence from mouse, rabbit, nonhuman primate, and human studies of herpes simplex virus type 1 (HSV-1) concerning corneal latency.

METHODS

More than 50 research articles on HSV-1 published in peer-reviewed journals were examined.

RESULTS

Infectious HSV-1 has been found in mouse denervated tissues and in tissues with negative cultures from the corresponding ganglion. However, the different mouse strains have shown varied responses to different strains of HSV, making it difficult to relate such findings to humans. Rabbit studies provide excellent evidence for HSV-1 corneal latency including data on HSV-1 migration from the cornea into the corneoscleral rim and on the distribution of HSV-1 DNA in the cornea. However, the available methods for the detection of infectious HSV-1 may not be sensitive enough to detect low-level infection. Infectious HSV-1 has been successfully isolated from the tears of nonhuman primates in the absence of detectable corneal lesions. The recurrence of corneal ulcers in nonhuman primates before the appearance of infectious HSV-1 in tears suggests that the origin of the HSV-1 is the cornea, rather than the trigeminal ganglion. Human studies presented evidence of both ganglion and corneal latency.

CONCLUSIONS

Understanding HSV-1 disease progression and the possibility of corneal latency could lead to more effective treatments for herpetic keratitis. However, it is unlikely that operational latency in the cornea will be definitively proven unless a new method with higher sensitivity for the detection of infectious virus is developed.

Clinical application of real-time polymerase chain reaction for diagnosis of herpetic diseases of the anterior segment of the eye

PURPOSE

To assess the value of quantification of herpes simplex virus (HSV) DNA for the differential diagnosis of herpetic diseases of the anterior segment of the eye.

METHODS

One hundred forty-four samples from 90 patients with ocular inflammatory diseases were examined for HSV DNA by real-time polymerase chain reaction (PCR) with primers set for the consensus sequence of HSV-1/2 DNA polymerase. The samples included corneal epithelial scrapings, tear fluid (200microl of eye wash), and aqueous humor.

RESULTS

In cases of typical herpetic epithelial keratitis, a large number of copies of HSV DNA were detected (mean, 1.0 x 10(7) copies in epithelial scrapings and 3.5 x 10(5) copies in tear fluid). In atypical epithelial keratitis cases, a smaller number of HSV DNA copies were detected. In stromal keratitis cases, the number of copies of HSV DNA in the tear fluid (mean: 4.7 x 10(2) copies) was significantly smaller than in cases of epithelial keratitis. In the aqueous humor, the number of copies was small in endotheliitis cases (mean, 2.9 x 10(2) copies/microl), but the range was great, from (1.2-4.8) x 10(5)/microl in herpetic iridocyclitis. Seventeen percent of cases in which HSV was not suspected to be involved showed a small number of copies of HSV DNA, indicating the unexpected involvement of HSV in these cases.

CONCLUSIONS

Real-time PCR is an informative method of diagnosing herpetic eye diseases and evaluating the possible involvement of HSV in other inflammatory ocular diseases.

Specific antibody production in herpes keratitis: intraocular inflammation and corneal neovascularisation as predicting factors

PURPOSE

The purpose of the study is to investigate whether analysis of specific antibody synthesis can aid the diagnosis of herpes keratitis.

METHODS

Aqueous humor was collected from 39 patients with presumed recurrent herpes keratitis, including 23 consulting for keratitis and 16 patients scheduled for penetrating keratoplasty. Local antibody production was ascertained by analysis of paired aqueous humor/serum samples, using a modified micro-ELISA technique.

RESULTS

Local production of antibodies was found in 32 patients (82%): anti-herpes simplex virus (HSV) antibodies in 26 (67%) and anti-varicella zoster virus (VZV) antibodies in 11 (28%). Twenty of 23 patients with active keratitis (87%), and 12 of 16 undergoing keratoplasty (75%), tested positive. Five patients had local production of both anti-HSV and anti-VZV antibodies, whereas seven patients tested negative. Local antibody production was significantly associated with intraocular inflammation (P<0.05), corneal neovascularisation (P<0.05), and positive response to anti-viral treatment (P<0.05). No complications were encountered in sampling aqueous humor.

CONCLUSIONS

Assessment of local anti-HSV and -VZV antibody production is a safe and reliable diagnostic procedure for recurrent herpes keratitis. It might be particularly helpful in patients presenting with intraocular inflammation and neovascularisation since it discriminates between herpes and non-herpes pathologies and may therefore be useful for preventive and therapeutic strategies.

Epidemiology and molecular analysis of herpes simplex keratitis requiring primary penetrating keratoplasty

AIMS

To determine whether herpes simplex keratitis (HSK) has declined as an indication for penetrating keratoplasty (PKP) at the University of California San Francisco (UCSF) over the past 30 years.

METHODS

Records of the Hogan Eye Pathology Laboratory were reviewed to determine the incidence of PKP performed for HSK from 1972 through 2001. Archived corneal tissue with the diagnosis of HSK was evaluated for herpes simplex virus (HSV) DNA by polymerase chain reaction (PCR) based assays.

RESULTS

The number of corneal buttons submitted with the clinical diagnosis of HSK decreased from 1972 to 2001, while the overall number of PKPs performed did not. The percentage of corneal buttons with a clinical diagnosis of HSK that contained detectable HSV DNA did not change over the course of the study period.

CONCLUSION

HSK declined as an indication for PKP from 1972 to 2001 at UCSF. It is unlikely that this decline was the result of improved diagnostic accuracy since detection of HSV DNA in corneal buttons with a clinical diagnosis of HSK was similar at the beginning and end of the study period.

[Clinical and diagnostic developments in corneal herpes]

The indications for keratoplasty in treating herpes keratitis are currently declining because of recent progress in diagnosis and treatment. Clinically, corneal signs may be caused by HSV reactivation or a secondary anti-HSV immune response. Corneal opacification may be acute or the expression of sequela (meta-herpetic keratitis). The virus can be detected on a corneal surface sample by direct examination or cell culture, the only way to detect an infective virus. The detection of local antibody production in the aqueous humor is an inexpensive method, indicating the local immune anti-HSV response. Detection of HSV DNA using PCR is more sensitive, but the presence of HSV DNA within corneal tIssue may be more delicate to interpret. It is now proven that HSV can be transmitted through a corneal graft from donor to recipient, but no diagnostic test currently detects potentially infective corneas in eyebanks.

New onset of herpes simplex virus epithelial keratitis after penetrating keratoplasty

PURPOSE

To report a series of patients with no previous history of herpes simplex virus (HSV) infection who had new onset of herpetic keratitis after penetrating keratoplasty (PK).

DESIGN

Noncontrolled, retrospective case series.

METHODS

We included in the study the patients who had new onset of herpetic keratitis after penetrating keratoplasty for corneal diseases unrelated to HSV infection who were seen at the Cornea Service at Wills Eye Hospital (Philadelphia, Pennsylvania) from January 1996 to December 2002. The diagnosis of HSV epithelial keratitis was based on clinical characteristics of either a classic herpetic dendrite, a geographic ulcer, or a nonhealing epithelial defect that responded only to antiviral therapy.

RESULTS

Fourteen patients were included in the study. Eight of these (57%) had presented with a geographic ulcer whereas six patients (43%) had a classic dendrite. The most common primary corneal disease that led to PK was pseudophakic bullous keratopathy (36%), followed by keratoconus (29%), Fuchs dystrophy (21%), and corneal scar unrelated to HSV (14%).

CONCLUSIONS

The ophthalmologist should be aware of the possibility of herpetic keratitis in eyes after PK, even in patients with no previous history of HSV infection.

Herpes simplex virus DNA in corneal transplants: prospective study of 38 recipients

Herpes simplex virus (HSV) infection of the eye can induce epithelial and stromal keratitis and may also lead to postoperative endothelial failure in keratoplasty. Clinical symptoms and/or virus culture of corneal scrapings most frequently provide the basis for diagnosis of ocular HSV infection, and although HSV DNA has been shown to be present in the cornea, its role in success or failure of corneal grafts remains unclear. In this study, a PCR assay was used to detect HSV DNA in corneal buttons of 38 corneal graft recipients and in donor scleral remnants, retaining one-half of each sample for subsequent viral isolation. Recipients were followed up clinically for a period of 6 months after keratoplasty. All recipients but three were found to be HSV seropositive. Eight recipient corneal buttons contained detectable HSV DNA (7 HSV-1, 1 HSV-2, the latter case confirmed by viral culture). Two donor corneas were found positive for HSV-1 DNA, with negative cultures, and endothelial graft failure occurred in one of the matching recipients after 4 months. One recipient with no history of herpes contracted herpetic keratitis 4 months after keratoplasty, even though the corneal button and donor scleral remnants contained no detectable HSV DNA. The study confirms previous observations of HSV DNA in the corneal tissue of HSV seropositive patients apparently unrelated to any clinical manifestation of herpes infection. However, as demonstrated by culture, HSV remains infectious and may therefore induce donor-to-host infection in corneal recipients.

HSV-1 antigens and DNA in the corneal explant buttons of patients with non-herpetic or clinically atypical herpetic stromal keratitis

BACKGROUND

Little is known about the role of HSV-1 in keratitis not primarily attributed to herpetic origin. This study therefore aimed to prospectively evaluate the corneal explant buttons of patients with non-herpetic or clinically atypical herpetic stromal keratitis (experimental group: non-HSK) for the presence of HSV-1 antigens and DNA, and to compare the findings with those from individuals with typical herpetic stromal keratitis (positive control group: HSK) or non-inflammatory degenerative keratopathy (negative control group).

METHODS

Corneal buttons derived from 51 patients with HSK, from 72 with non-HSK and from 30 with degenerative keratopathy were prospectively collected and subjected to immunohistochemical analysis for HSV-1 antigens and to HSV-1 DNA amplification.

RESULTS

In corneal buttons derived from patients with non-HSK, viral antigens were detected immunohistochemically in 8/72 cases and DNA amplified in 16/72. Corresponding values for the HSK group were 16/51 and 11/51. Taking viral antigen and DNA findings together, HSV-1 was detected in 18/72 (25%) patients with non-HSK and in 19/51 (37%) with HSK (p=0.2), but in only 2/30 (6%) individuals with non-inflammatory degenerative keratopathy.

CONCLUSION

Since the detection frequencies for HSV-1 antigens and DNA were comparable in the HSK and non-HSK groups, Herpes may play an underestimated and as yet undefined role in non-herpetic and clinically atypical herpetic stromal keratitis, either as a primary trigger of the disease or as a secondary contributor to it. In this category of individuals, early anti-herpetic therapy should be considered if patients do not respond in the expected manner to treatment for non-herpetic stromal keratitis.

Herpes simplex virus infection in the media of donor corneas during organ culture: frequency and consequences

BACKGROUND AND PURPOSE

According to polymerase chain reaction (PCR) studies 2-38% of organ culture donor corneas may contain herpes simplex virus (HSV) DNA, but there are only 6 reported instances of proven virus replication in a corneoscleral disc. Moreover there are only 6 patients reported in whom primary graft failure and extensive post-operative epithelial defects were probably caused by a herpetic infection of the corneal graft. Recently we observed virus replication in a donor cornea with subsequent complete endothelial necrosis in our cornea bank. The aim of this study was to investigate the possible correlation between herpetic donor cornea infection and endothelial necrosis in organ culture.

METHODS

To evaluate the frequency of HSV as a reason for endothelial necrosis in organ culture we tested the media of 199 donor corneas discarded due to an altered endothelium in the years 1997 to 1999 by PCR for HSV. As a negative control group we screened the media of 117 transplanted corneas using PCR.

RESULTS

In the control group we had only negative PCR results, in contrast to the corneas with severe or complete endothelial necrosis where HSV DNA was detected in 12 media of the corneas of 9 donors. Virus could be cultivated out of 7 media.

CONCLUSIONS

(1) HSV replication is a common cause of severe endothelial necrosis in organ culture corneas. (2) Replication of the virus during organ culture comes close to a virus cultivation using the corneoscleral disc as a cell culture. (3) We consider the danger of transplanting active HSV to be very small if critical assessment of the graft prior to surgery is carried out.

Feline leukemia virus detection in corneal tissues of cats by polymerase chain reaction and immunohistochemistry

OBJECTIVES

To determine the presence of feline leukemia virus (FeLV) in the corneas of FeLV-infected cats.

ANIMALS STUDIED

Thirty-four random source cats.

PROCEDURES

Seventeen cats were found positive for FeLV serum p27 antigen by enzyme-linked immunosorbent assay (ELISA). Twelve ELISA positive cats were also positive on peripheral blood samples by immunofluorescent antibody (IFA) testing. Seventeen ELISA negative cats served as negative controls. Full thickness corneal specimens were collected from the left cornea of all cats and analyzed for FeLV proviral DNA and gp70 antigen by polymerase chain reaction (PCR) and immunohistochemical (IHC) testing, respectively.

RESULTS

Eleven (64.7%) positive corneal PCR results were obtained from 17 ELISA positive cats. Of 12 cats that were both ELISA and IFA positive on peripheral blood, 10 (83.3%) had positive corneal PCR results. All corneal tissues from ELISA negative cats were PCR negative. IHC staining of corneal sections revealed the presence of FeLV gp70 in corneal tissues of nine (52.9%) ELISA positive cats. Of the 12 cats that were both ELISA and IFA positive on peripheral blood, eight (66.7%) had positive corneal IHC results. Positive IHC staining was localized to the corneal epithelium. Corneal tissues of all ELISA negative cats and all IFA negative cats were negative on IHC testing.

CONCLUSIONS

FeLV antigens and proviral DNA are present in corneal tissues of some FeLV-infected cats. Screening corneal donors for FeLV infection is warranted.

Primary graft failure caused by herpes simplex virus type 1

PURPOSE

To present a cluster of four patients with primary graft failure (PGF) who consecutively underwent a penetrating keratoplasty (PKP) during a period of 17 days in one institution. PKP was performed for reasons unrelated to herpes simplex infection. Herpes simplex virus type 1 (HSV-1) is presented as the possible cause of these PGFs.

METHODS

Viral culture of conjunctival swabs and of a bandage contact lens was performed on VERO, MRC-5, and Hep-2 cells. The four patients underwent subsequent regrafting. Polymerase chain reaction (PCR) for HSV-1 was carried out on aqueous humor and on a sample of iris and cornea with primers. Aqueous humor specimens were pretreated by boiling, and a qiagen extraction was performed according to the instructions of the manufacturer on biopsies of iris and cornea. Immunohistopathology was performed with polyclonal antibodies directed against HSV-1 and -2.

RESULTS

Culture of a conjunctival swab in three patients and culture of a bandage contact lens in the fourth patient were positive for HSV-1. In three of the four patients, PCR was positive for HSV-1 on aqueous humor and corneal graft tissue. PCR on iris tissue was positive in all patients. In three patients, culture for HSV-1 of aqueous humor and of iris tissue could not be carried out because of insufficient sample. Viral culture of the iris tissue in one patient and of the corneal graft in the four patients were negative. Immunohistopathologic examination was positive for HSV-1 in three cases.

CONCLUSION

These case reports strongly support the hypothesis that HSV-1 can be the cause of PGF.

Investigation of aciclovir-resistant herpes simplex virus I infection in a bone marrow transplantation unit: genotyping shows that different strains are involved

Over an eight-month period from October 1997 to May 1998, four patients who had received a bone marrow transplant (BMT) from an unrelated donor presented with severe mucosal cutaneous infections involving aciclovir resistant herpes simplex virus 1 (HSV-1). The emergence within a short period of resistant HSV-1 strains in the bone marrow transplantation unit raised fears of hospital-acquired infections. The hypothesis was investigated by restriction fragment length polymorphism (RFLP), sequencing of the thymidine kinase (TK) gene and genotyping of hypervariable regions of these four strains. Restriction fragment length polymorphism proved to be poorly discriminant and the TK sequence did not rule out transmission between these patients. Amplification of reiterating hypervariable genomic HSV-1 regions designated Re IV and Re VII clearly differentiated patients' strains. Thus, in this study, there was no evidence of nosocomial transmission of HSV-1 strains between the four patients.

Detection of herpes simplex virus type 1, 2 and varicella zoster virus DNA in recipient corneal buttons

AIM

To study the value of polymerase chain reaction (PCR) analysis, to detect viral DNA in recipient corneal buttons taken at the time of penetrating keratoplasty (PKP) in patients with an initial diagnosis of herpetic stromal keratitis (HSK). Since HSK has a tendency to recur, an accurate diagnosis of previous HSK could be the reason to start antiviral treatment immediately, thereby possibly decreasing the number of graft failures due to recurrent herpetic keratitis.

METHODS

Recipient corneal buttons and aqueous humour (AH) samples were obtained at the time of PKP from HSK patients (n=31) and from other patients (n=78). Eye bank corneas were also used (n=23). Herpes simplex virus type 1 (HSV-1), type 2 (HSV-2), and varicella zoster virus (VZV) infection were assessed by PCR and antibody detection.

RESULTS

The clinical diagnosis HSK could be confirmed by PCR for HSV-1 in 10/31 (32%). In these corneal buttons HSV-2 DNA was detected in 1/31 (3%) and VZV DNA in 6/31 (19%). Intraocular anti-HSV antibody production was detected in 9/28 AH samples tested (32%). In the other patient derived corneas HSV-1 DNA was detected in 13/78 (17%), including eight failed corneal grafts without clinically obvious herpetic keratitis in the medical history. In clear eye bank corneas HSV-1 was detected in 1/23 (4%).

CONCLUSIONS

PCR of HSV-1 on corneal buttons can be a useful diagnostic tool in addition to detection of intraocular anti-HSV antibody production. Furthermore, the results were suggestive for the involvement of corneal HSV infection during allograft failure of corneas without previous clinical characteristic signs of herpetic keratitis.

Human herpesviruses in the cornea

AIMS

To determine the sensitivity and specificity of culture, immunohistochemistry (IHC), the polymerase chain reaction (PCR), and in situ hybridisation (ISH) for detecting herpes simplex virus (HSV-1) in the cornea of patients undergoing penetrating keratoplasty. To compare the incidence of HSV-1 in the cornea with that of varicella zoster virus (VZV), cytomegalovirus (CMV), and Epstein-Barr virus (EBV).

METHODS

The corneas of 110 patients, 52 with a documented history of herpes keratitis (HSK) and 58 with non-herpetic corneal disease, were investigated using IHC, PCR, ISH, and culture.

RESULTS

HSV-1 DNA and antigen were detected in 82% and 74% respectively, of corneas of patients with HSK and in 22% and 15% of corneas of patients with no history of HSK. The sensitivity of PCR and IHC was 82% and 74% with a specificity of 78% and 85%, respectively. HSV-1 DNA and antigen were found more frequently and in increased amounts in corneas of patients with a short interval between their last attack of HSK and surgery. There was a good correlation between PCR and IHC in 71%. HSV-1 was isolated by culture in 2%. Latency associated transcripts were not detected using ISH. Evidence of VZV DNA or antigen was found significantly more frequently in the corneas of patients with a history of HSK (p<0.001). No evidence of EBV or CMV was found in any cornea.

CONCLUSIONS

PCR and IHC are both sensitive for the detection of HSV-1 in the cornea. A combination of PCR and IHC increases the specificity for the diagnosis of HSK to 97%. HSV-1 appears to be slowly removed from the cornea. VZV and HSV-1 may co-infect the cornea.

Low rate shedding of HSV-1 DNA, but not of infectious virus from human donor corneae into culture media

Fluid samples derived from 451 organ cultured corneae were tested for the presence of HSV-1 DNA after electroseparation and amplification for fragments of the glycoprotein D- and thymidine kinase-encoding genes. Of the culture media, 134 were processed immediately after withdrawal (Group 1); 100 were stored at ambient temperature for 6 to 60 weeks (Group 2); 90 were stored at -8 degrees C for 4 to 9 weeks (Group 3); and 127 were stored at -20 degrees C for 2 to 30 weeks (Group 4). The degradation of human DNA (marker gene, betaglobin) under these different storage conditions and of human and HSV-1 DNA as a sequential function of time at ambient temperature was gauged by the loss of a detectable signal for the respective component. Endothelial cell density within each of the corneal discs was determined before and after organ culture. In 7/451 culture fluid samples, HSV-1 DNA corresponding to either the glycoprotein D- or thymidine kinase-encoding genes was detected. In culture fluid samples derived from Group 2 at ambient temperature, for 6 to 60 weeks) and 3 (at -8 degrees C, for 4 to 9 weeks), complete degradation precluded the detection of human DNA, and hence probably also of HSV-1 DNA; only at -20 degrees C did DNA remain stable for protracted periods of time. Even so, HSV-1 DNA was detected in only 2% of those media in which no degradation was to be expected; additionally, there existed no correlation between its presence in culture fluid samples and the loss of endothelial cells or cytopathic changes. DNA can be extracted successfully and concentrated twenty-fold from high-volume samples by electroseparation. When shed into culture fluid, it is remarkably prone to a time and temperature dependent degradation, which may lead to false negative results. It is concluded that there is no infectious virus to be expected in the specimens; the occurrence of HSV-1 DNA in donor corneae would not appear to be an important factor influencing their biological quality during the period of organ culture.

Newly acquired herpes simplex virus keratitis after penetrating keratoplasty

BACKGROUND

After penetrating keratoplasty for reasons unrelated to herpes simplex virus (HSV) keratitis, any nonspecific epithelial defect may still be caused by HSV. The purpose of this study is to determine the incidence of newly acquired herpetic keratitis and to assess contributing factors.

METHODS

The authors retrospectively studied the results of 2398 penetrating keratoplasties performed between 1980 and 1995. Three typical case histories are discussed.

RESULTS

Of 2112 patients in whom the primary diagnosis was not related to HSV keratitis, 18 presented with epithelial herpetic keratitis in their corneal graft. The incidence of newly acquired herpetic keratitis after penetrating keratoplasty was 1.2 per 1000 person-years. In most cases, the infection occurred in the first 2 years after the transplantation. Most often, well-known reactivating stimuli could have caused the HSV infection.

CONCLUSIONS

Herpes simplex virus keratitis may develop after penetrating keratoplasty even without a clinical history of HSV in the host. Thus, HSV should be considered in the differential diagnosis of a postpenetrating keratoplasty epithelial defect. The high incidence of this infection in the first 2 years after such surgery suggests a causal relation between corneal transplantation and the HSV infection.

High sensitivity polymerase chain reaction assay for active and latent feline herpesvirus-1 infections in domestic cats

A polymerase chain reaction (PCR) assay was developed and used to detect feline herpesvirus-1 (FHV-1) in conjunctival and oropharyngeal swabs, and in latently infected tissues (trigeminal ganglia, optic nerves, optic chiasma, olfactory bulbs and corneas) collected from 10 experimentally infected cats. There was good agreement between parallel tests of the swab specimens by PCR and virus isolation assay during the phase of acute, latent and recurrent disease episodes (kappa = 0.63, P < 0.001). The PCR reliably detected < or = 240 copies of FHV-1 template DNA, significantly improving upon previously published PCR assays for the agent.

Slow viral replication of HSV-1 is responsible for early recurrence of herpetic keratitis after corneal grafting

BACKGROUND

The presence of herpetic DNA has been shown in diseased and healthy corneal tissue. A clinical correlation with the activity of the disease has not yet been demonstrated. This study was done to evaluate the use of DNA amplification for HSV-1 from different sites for the clinical prognosis after corneal grafting.

PATIENTS AND METHODS

Eighteen patients with herpetic keratitis, 8 patients with other forms of keratitis, and 15 patients with corneal disease unrelated to herpes undergoing penetrating keratoplasty were investigated. From these, aqueous humor was obtained at the time of surgery. The excised cornea was divided into three parts for paraffin embedding, 24 h tissue culture and preparation of minced tissue. All samples were processed for HSV-1 glycoprotein D PCR followed by Southern blot and DNA hybridization.

RESULTS

In the herpes group, target DNA was detected in 4/18 aqueous humor samples, 7/16 minced tissue preparations, 6/18 explant culture fluid samples and 4/15 paraffin sections. In the control groups of other keratitis and non-herpetic eye disease, respectively, target DNA was found in 0/5 and 2/12 aqueous humor samples, 1/6 and 0/12 minced tissue preparations, 0/8 and 0/15 explant culture fluid samples and in 1/6 and 1/14 paraffin sections. Five of six patients in whom herpes DNA was detected in the short-term tissue culture experienced an episode of herpes reactivation, within 4 months after transplantation, whereas only one of the remaining patients in all three groups did so (p = 0.0005).

CONCLUSION

A slow viral replication may be responsible for early recurrence of herpetic keratitis after corneal grafting. Detection of herpetic DNA in short-term tissue cultures from explant tissues may help to define the patients at risk.

Detection of herpes simplex virus after penetrating keratoplasty by polymerase chain reaction: correlation of clinical and laboratory findings

BACKGROUND

The study was carried out to investigate the possible correlation of clinical findings, histopathologic features and detection of herpes simplex virus DNA in corneal buttons obtained after penetrating keratoplasty.

METHODS

We examined 47 consecutive corneal buttons sent for histopathologic examination by light microscopy and using the polymerase chain reaction for the detection of HSV1 and HSV2. Twenty-one corneal buttons from eyes with bullous keratopathy served as controls.

RESULTS

The 47 cases were graded from the clinical information available as unproven, suspected and clinically proven cases of herpetic keratitis. This grading did not correlate to specific histopathologic features or to the results of HSV1 DNA testing. None of the cases were positive for HSV2 DNA.

CONCLUSION

HSV DNA was detected in some of the cases of clinically unsuspected herpetic keratitis. This technique of demonstrating the presence or absence of HSV in the cornea after keratoplasty is more reliable than clinical data or histopathologic findings and may be important in cases of recurrent inflammatory episodes involving grafts after keratoplasty.

Herpes simplex virus DNA in normal corneas: persistence without viral shedding from ganglia

Herpes simplex virus type 1 (HSV-1) DNA has been shown to persist in the cornea not only after inoculation of experimental animals but also in surgical samples from patients with herpes keratitis. The further observation of corneal HSV-1 DNA in subjects without known HSV eye disease prompted the present study of the presence and distribution of HSV-1 in eye bank corneas. Prior to DNA extraction, the corneas were trephined, separating the central and peripheral cornea. With polymerase chain reaction (PCR) for HSV-1 thymidine kinase (TK) and glycoprotein D (gD) gene sequences, we found HSV-1 in 10 of 24 eye bank corneas, from the 4 mm wide corneal rim in 8 eyes and from the 8 mm diameter central cornea in 2 eyes. In 9 subjects, both eyes were assayed, and HSV-1 was detected in 6 subjects. In only one subject was HSV-1 detected in both eyes and in only one subject was HSV-1 detected in the central and peripheral cornea of the same eye. The biological role of HSV-1 DNA corneal sequences is unknown. To investigate this, a rabbit animal model was established by transplantation of corneas containing viral DNA sequences in HSV-1 naive recipients. Followed for 5 months, there was no evidence of sheeding of HSV-1 in the tear film or seroconversion of the recipient rabbits. At the end of this time, HSV-1 DNA was detected in the corneal graft at a similar intensity to the PCR signal from the donor rims.(ABSTRACT TRUNCATED AT 250 WORDS)

Detection of human immunodeficiency virus, hepatitis B virus, and hepatitis C virus in donor eyes using polymerase chain reaction

Detection of human immunodeficiency virus (HIV), hepatitis B virus (HBV), and hepatitis C virus (HCV) in donor eyes was performed. DNAs were extracted from the uvea, and they were amplified using the polymerase chain reaction (PCR). Amplified viral DNAs were detected with liquid hybridisation and chemiluminescent assay in which no radioactive materials were used. This method was shown to have a sensitivity limit of fewer than 10 copies of HIV, making it much more sensitive than the current techniques employed in eye banks. The method was applied to 120 donor eyes, including four from donors seropositive for HBV. The HBV gene was detected in one case in which the donor's blood had not been tested for HBV. HIV and HCV genes were not detected in any of the samples. The assay could be an effective screening test for the detection of these viruses in eye bank eyes.

Typing and strain differentiation of clinical herpes simplex virus type 1 and 2 isolates by polymerase chain reaction and subsequent restriction fragment length polymorphism analysis

In the present study, different combinations of primers were investigated for PCR amplification and typing of clinical herpes simplex virus type 1 (HSV-1) (n = 22) and herpes simplex virus type 2 (HSV-2) (n = 12) isolates. Intratypic strain differentiation was performed by restriction fragment length polymorphism (RFLP) analysis of different PCR amplified HSV genome regions. Enzymatic amplification of HSV DNA from all the clinical isolates could be achieved using primer combinations DNAP5/DNAp3-1 (HSV-1), DNAP5/DNAP3-2 (HSV-2). With the primer pair corresponding to the thymidine kinase (TK) genome region, amplification of all the HSV-1 isolates was only possible by nested PCR. With primers HSV UP/DOWN, 10 of 12 HSV-2 isolates could be detected. HSV typing by type-specific primers DNAP5/DNAP3-1 (HSV-1), DNAP5/DNAP3-2 (HSV-2) or restriction enzyme analysis (Ava II) of amplified DNA with HSV-specific UP/DOWN primers showed results which concorded with serotyping by monoclonal antibodies. RFLP analysis of the PCR products using selected restriction enzymes showed sufficient diversity of profiles among strains to differentiate all the HSV-1 isolates and to distinguish four groups of HSV-2 isolates. Amplification of HSV DNA from clinical isolates with subsequent typing and strain differentiation represents a valuable alternative to conventional methods (virus isolation, serotyping and restriction fragment analysis of the entire genomic DNA) and may be suitable for the study of HSV transmission and pathogenesis, especially in labour-intensive clinical samples with low levels of virus replication (i.e. cerebrospinal fluid, vitreous fluid and corneal transplants).

A thymidine kinase deficient HSV-2 strain causes acute keratitis and establishes trigeminal ganglionic latency, but poorly reactivates in vivo

The incidence of herpetic keratitis following intranasal or direct ocular infection with thymidine kinase-negative (TK-) strains of herpes simplex virus (HSV)-2 has not been well studied, and the role of the TK gene in the establishment of latency and virus reactivation is controversial. To determine whether a TK- strain of HSV-2 could establish trigeminal ganglionic latency and be reactivated in vivo to produce recurrent keratitis or nervous system infection, an animal model of acute and recurrent infection was utilized. Rabbits were infected by the intranasal or ocular routes, and latency was reactivated by immunosuppression. Virus shedding in nasal and ocular secretions was monitored, and the eyes were examined for the presence of corneal epithelial lesions during acute and reactivated infections. Central nervous system (CNS) and trigeminal ganglionic tissues were assayed by histologic, virologic, and in situ hybridization techniques. All rabbits intranasally infected shed virus in both ocular and nasal secretions, whereas only 30% of rabbits infected in the eyes shed virus in nasal secretions. Virus was recovered from cocultivation cultures, but not from cell-free homogenates, of trigeminal ganglionic and CNS tissues from animals inoculated by both routes. The incidence of keratitis was much greater after direct ocular inoculation, although both routes of inoculation produced CNS and ganglionic inflammatory lesions. Keratitis healed in 92% of the animals infected by the ocular route by 26 days post infection. Of rabbits initially infected in the eyes and then subjected to drug-induced reactivation, only 30% shed virus, which was limited to a 24 hour period; there was no reappearance of epithelial keratitis, no animal became blind, and none died. In contrast, latently infected control rabbits uniformly reactivated. These studies show that this TK-HSV-2 strain (i) replicates in the eye, (ii) is neuroinvasive but non-neurovirulent following intranasal and direct ocular infection; (iii) sheds in the eye more frequently and for longer periods after ocular than after intranasal inoculation; (iv) induces epithelial keratitis that usually heals spontaneously; (v) establishes latency in trigeminal ganglionic neurons, but no other ganglionic cells; and, (vi) reactivates in a small proportion of animals, but does not produce recurrent ocular lesions following drug-induced immunosuppression. Thus, the TK gene appears directly involved in HSV latency and reactivation in vivo.

Detection of herpes simplex virus DNA sequences in human blood and bone marrow cells

Herpes simplex virus type 1 (HSV1) establishes latent infections in neural tissues of humans and experimental animals. Utilizing a sensitive polymerase chain reaction (PCR) assay we detected HSV DNA sequences in blood cells of healthy prospective bone marrow transplant (BMT) donors and patients. In three healthy individuals studied, HSV DNA sequences were found in all blood cell types and also in bone marrow cells as well as in stem cell progenitor colonies isolated from in vitro cultures. Studies of BMT donor-recipient pairs suggested that HSV reactivation may occur in hematopoietic cells after transplantation, as the PCR signal intensity increased over time simultaneous with an increased antibody titer to HSV. In a mouse model for HSV infection, HSV DNA sequences were found in blood and bone marrow cells at the latent stage of infection, after intravenous (IV) inoculation, but not after ocular inoculation. These studies suggest that bone marrow cells may be an additional site of HSV latency capable of reactivation after BMT. These studies have broad implications for understanding pathogenesis of HSV disease and are of particular significance in situations where allogeneic bone marrow cells are given therapeutically.

Detection of active and latent feline herpesvirus 1 infections using the polymerase chain reaction

A polymerase chain reaction (PCR) assay was developed to detect the thymidine kinase gene of feline herpesvirus 1 (FHV-1) and to study the active and latent carrier state in a group of naturally FHV-1 infected specific pathogen free (SPF) cats. The detection limit of PCR products on ethidium bromide stained gels was 390 fg or about 3 x 10(3) copies of the FHV-1 genome. The PCR was 25% more sensitive than conventional cell culture based virus isolation techniques in detecting FHV-1 in oral/ocular swabs and 100 times more sensitive in detecting virus in cell culture supernatants. Sites of FHV-1 latency in FHV-1 carriers as determined by PCR were mainly tissues of the head, especially the trigeminal ganglia, optic nerves, olfactory bulbs and corneas. Oral fauces, salivary glands, lacrimal glands, cerebellum and conjunctiva were less consistently positive. The cerebral cortex, thymus, trachea, lung, liver, spleen, kidney, and peripheral blood mononuclear cells were consistently negative for FHV-1 genome. The distribution of FHV-1 DNA in the tissues of the head was similar whether or not corticosteroid-induced virus shedding was occurring at the time the tissues were collected. Infectious virus was never recovered from tissue homogenates regardless of the PCR status of the tissues.

Biology and molecular aspects of herpes simplex and varicella-zoster virus infections

The herpes simplex and varicella-zoster viruses are members of the subfamily alpha herpesviruses with specific properties of the virion and with the capacity to establish latent infections in humans. The genome of each of these viruses has been determined with an estimate of the number of genes and proteins encoded. The biology and molecular events of the herpes simplex virus productive and latent infection have been detailed with the use of both in vitro and in vivo model systems. The neuron is the site of latency in the ganglia with a limited transcription of genes expressed during the latent period. The specific molecular regulation of latency and reactivation are not well established. There are co-cultivation, electron microscopy, and biochemical studies that support the concept of corneal latency, although this has not been proven conclusively. Details about the varicella-zoster virus biology and molecular events are not as well advanced since animal models have been lacking. The biology of the productive infection (varicella) is different from herpes simplex virus infection since the portal of entry is the respiratory system. Data support the concept of the maintenance of latency within satellite cells in the ganglia rather than within neurons. There are multiple genes expressed during this latency. These features may explain the different clinical presentations and course of reactivation (zoster) compared with herpes simplex virus reactivation.