Evidence for herpes simplex viral latency in the human cornea

Herpes simplex virus PCR in 2230 explanted corneal buttons

PURPOSE

To determine herpes simplex virus (HSV) DNA prevalence and mean cycle threshold of polymerase chain reaction (PCR) in corneal tissue of patients with penetrating keratoplasty (PKP), with (HSK+) and without (HSK-) previous clinical herpetic keratitis history.

METHODS

Retrospective review of recipient corneal buttons which were explanted through PKP between March 2010 and September 2018 at the Department of Ophthalmology, Saarland University Medical Center in Homburg/Saar, Germany. Corneal tissue samples were analysed by real-time PCR for the presence of HSV DNA. For each subject, clinical data, including patients' demographics and clinical diagnoses, were collected.

RESULTS

In total, 2230 corneal samples (age at the time of the surgery 57.3 ± 19.2 years) of 1860 patients were analysed. HSV PCR was positive in 137 (6.1%) corneal samples, with a 30.57 ± 6.01 (range 14-39) mean cycle threshold (Ct) value. Two hundred ninety-eight (13.4%) corneas of 266 patients were clinically HSK+, and 1932 (86.6%) corneas of 1600 patients were clinically HSK-. HSV DNA was detected significantly more frequently (p < 0.0001) in HSK+ corneal samples (108 corneal samples; 36.2%), than in HSK- corneal samples (29 corneal samples; 1.5%). Ct value was significantly lower in HSK+ than in HSK- corneal samples (29.8 ± 5.8 versus 32.6 ± 5.9; p = 0.008).

CONCLUSION

Our data demonstrate that a positive clinical history of HSK is related to HSV PCR positivity in about every 2.8th patient. In addition, about every 66th explanted corneal tissue is HSV PCR-positive despite the lack of clinical suspicion. These patients may need additional local/systemic antiviral treatment to avoid newly acquired HSK following penetrating keratoplasty.

Quantitative analysis of herpes simplex virus-1 transcript in suspected viral keratitis corneal buttons and its clinical significance

Purpose:

The evaluation of Herpes Simplex virus-1 (HSV-1) transcript by different investigative methods (qPCR, PCR and IHC) in corneal buttons from suspected viral keratitis patients and the comparison of results with histopathological findings and clinical diagnosis.

Methods:

Sixty corneal buttons, 30 suspected viral keratitis, and 30 controls (keratoconus and bullous keratopathy) obtained after primary penetrating keratoplasty, were included in the study. All the corneal buttons were subjected to reverse transcriptase quantitative PCR (qPCR) for the detection of latency-associated transcript (LAT) gene, conventional PCR for polymerase (pol) gene, and immunohistochemistry (IHC) for HSV-1 antigen respectively. After obtaining baseline preoperative clinical data, all the patients were followed up for three years. The results obtained were correlated with clinicopathological features and follow-up data.

Results:

Of the 30 suspected viral keratitis patients there were 6 females and 24 males with mean age 46.5 ± 24.62 years (3-80 yrs). There was a marked male preponderance (80%). HSV-1 LAT transcript was detected in 23% (7/30) corneal buttons by qPCR, HSV-1 DNA in 6.7% (2/30) and HSV-1 antigen in 30% (9/30) cases by conventional PCR and IHC respectively. A statistically significant association was found between qPCR and DNA PCR (P = 0.04). All the 30 control corneas were negative for HSV-1 LAT gene, DNA and antigen.

Conclusion:

Detection of HSV-1 LAT transcript by qPCR may be superior to HSV-1 DNA PCR (conventional) and IHC, which has low sensitivity. However, the utility of HSV-1 LAT mRNA analysis as a diagnostic modality by qPCR needs to be validated on a larger patient cohort.

Characteristics of New Onset Herpes Simplex Keratitis after Keratoplasty

Purpose

To observe clinical characteristics and treatment outcomes of new onset herpes simplex keratitis (HSK) after keratoplasty.

Methods

Among 1,443 patients (1,443 eyes) who underwent keratoplasty (excluding cases of primary HSK) in Shandong Eye Hospital, 17 patients suffered postoperative HSK. The clinical manifestations, treatment regimens, and prognoses of the patients were evaluated.

Results

The incidence of new onset HSK after keratoplasty was 1.18%. Epithelial HSK occurred in 10 eyes, with dendritic epithelial infiltration in 6 eyes and map-like epithelial defects in 4 eyes. Nine eyes had lesions at the junction of the graft and recipient. Stromal necrotic and endothelial HSK occurred in 7 eyes, presenting map-shaped ulcers in the entire corneal graft and recipient (two eyes) or at the graft-recipient junction (five eyes). Confocal microscopy revealed infiltration of a large number of dendritic cells at the junction of the lesion and transparent cornea. All 10 eyes with epithelial lesions and two eyes suffering stromal lesions of ≤1/3 corneal thickness healed after systematic and local antiviral treatment. Best-corrected visual acuity and corneal graft transparency were restored. For stromal HSK with an ulcer of >1/3 corneal thickness, amniotic membrane transplantation was performed, and visual acuity and graft transparency decreased significantly.

Conclusion

New onset HSK after keratoplasty primarily resulted in epithelial and stromal lesion, involving both the graft and recipient. Effective treatments included antiviral medications and amniotic membrane transplantation. Delayed treatment may lead to aggravated graft opacification.

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.

Equine Herpesvirus-4 Kinetics in Peripheral Blood Leukocytes and Nasopharyngeal Secretions in Foals Using Quantitative Real-Time TaqMan PCR

Based on the hypothesis that the viral load of cells infected with EHV-4 will likely change during the course of disease, TaqMan PCR was used to investigate and characterize the kinetics of EHV-4 viral DNA load (glycoprotein B gene) and transcriptional activity (glycoprotein B and latency-associated transcripts) in peripheral blood leukocytes (PBLs) and nasopharyngeal secretions (NSs) collected from 11 foals during a field outbreak of respiratory disease. The EHV-4 DNA load in PBLs was low and of short duration after onset of clinical signs. In contrast, the EHV-4 load in NSs remained high for the majority of the foals over a period of 4 weeks. Viral replication determined by detection of mRNA expression of the structural glycoprotein B was detected only in NSs during the first 7 days after onset of clinical signs for most foals. The majority of foals expressed latency-associated transcripts in NS sonly during the first 7 days after onset of clinical signs. Persistence of the expression of latency-associated transcripts in NS, as a reflection of a latent viral state, was not documented during the 28-day study period. Based on these results, it was concluded that lytic infection with EHV-4 can be diagnosed either by high EHV-4 DNA load of glycoprotein B gene or by detection of transcriptional activity of glycoprotein B.

Real-time polymerase chain reaction for the diagnosis of necrotizing herpes stromal keratitis

AIM

To design, optimize and validate a rapid, internally controlled real-time polymerase chain reaction (RT-PCR) test for herpes simplex virus (HSV) in the diagnosis of necrotizing herpes stromal keratitis.

METHODS

Tears alone or together with corneal epithelium scrapings from 30 patients (30 eyes) suspected of necrotizing herpes stromal keratitis were tested for HSV DNA by RT-PCR. The samples were collected during the first visit and then on the subsequent 7, 14, 28, 42, and 56d. The symptoms of the patients were scored before treatment to determine the correlation between HSV concentration in the corneal epithelium scrapings and clinical scores.

RESULTS

The positive rate (46.4%) in the corneal epithelium group before the therapy was significantly higher than that (13.3%) in the tears group (P=0.006). There were 13 positive HSV patients before the therapy, the concentration of HSV DNA in corneal epithelium scrapings group was significantly higher than that in the tears group (paired t-test, P=0.0397). Multilevel mixed-effects model analysis showed that the difference between the corneal epithelium scrapings group and the tears group was statistically significant (P=0.0049). The Spearman rank correlation analysis indicated a positive correlation between the HSV concentration in the corneal epithelium scrapings and clinical scores before the treatment (r=0.844, P<0.0001).

CONCLUSION

RT-PCR appears to be a powerful molecular tool for the diagnosis of necrotizing herpes stromal keratitis.

The treatment of HSV1 ocular infections using quantitative real-time PCR results

PURPOSE

Herpes stromal keratitis is a serious condition and the most frequent cause of unilateral blindness. The real-time PCR is an accurate and fast diagnostic method for an analysis of infectious agents causing keratitis and keratouveitis. The aim of the study was to assess the relationship between clinical symptoms, treatment efficacy monitoring and viral quantity in corneal swabs determined by quantitative real-time PCR method. The real-time PCR method was used as well for the detection of other viral eye pathogens.

METHODS

A total of 212 patients (136 men and 76 women) suspect of having herpes simplex virus (HSV) keratitis or keratouveitis were included in the study. The detection and quantitative analysis of the viral DNA were performed using the EliGene HSV1 RT kit, and the result was correlated with the clinical picture of the disease. The patients were routinely treated with acyclovir applied locally or, alternatively, in systemic administration. In a case of acyclovir treatment resistant keratitis, the patients were treated with local ganciclovir (Virgan gel ophth 0.15%).

RESULTS

A total of 636 analyses of the viral DNA were performed; 85 patients were positive for HSV1 (198 detected). There were 16 acyclovir resistant cases of keratitis (14%).

CONCLUSIONS

The real-time PCR appears as a fast and accurate method for an exact identification of the viral DNA in patients with herpes stromal keratitis. The introduction of the quantification is important for the treatment evaluation and for the specification of a so-called acyclovir resistant keratitis. A long-term systemic administration in maintenance doses may lead to the resistance and repeated, frequent relapses of the disease.

Therapeutic effect of deep anterior lamellar keratoplasty for active or quiescent herpetic stromal keratitis

PURPOSE

To evaluate the therapeutic effect of deep anterior lamellar keratoplasty (DALK) in patients with herpetic stromal keratitis (HSK).

METHODS

Forty-three eyes belonging to 42 patients with HSK, including 22 eyes in the active phase and 21 eyes in the quiescent phase, underwent DALK at the Shandong Eye Institute from January 2006 to December 2009. All patients with active disease had received intravenous acyclovir and amniotic membrane implants prior to DALK. Herpes simplex virus type 1 (HSV-1) antigens from excised corneal buttons were detected by immunohistochemistry.

RESULTS

The follow-up ranged from 1 to 4 years (mean, 29.1 months). Graft rejection occurred in one eye (2.3%) and was reversed. Among the other 42 survived grafts (97.7%), 37 remained clear at the last visit. The best spectacle-corrected visual acuity was 20/200 or better in 95.2% of eyes and 20/40 or better in 38.1% of eyes. Six eyes (14.0%) developed recurrent HSK, one of which received a second keratoplasty due to ineffective antiviral medication. There were no significant differences in endothelial cell density between 6 months and 12 months after the surgery. By immunohistochemistry, HSV-1 antigens were observed in the stroma of 18 of 32 corneal buttons.

CONCLUSIONS

DALK can not only remove the corneal lesions of HSK but also reduce latent or persistent viral loads in the cornea. In eyes with active or quiescent HSK but otherwise healthy endothelia, DALK seems to be safe and promising for its favorable visual outcome, graft survival rate, and low endothelial cell loss.

Ocular herpes simplex virus: how are latency, reactivation, recurrent disease and therapy interrelated?

Most humans are infected with herpes simplex virus (HSV) type 1 in early childhood and remain latently infected throughout life. While most individuals have mild or no symptoms, some will develop destructive HSV keratitis. Ocular infection with HSV-1 and its associated sequelae account for the majority of corneal blindness in industrialized nations. Neuronal latency in the peripheral ganglia is established when transcription of the viral genome is repressed (silenced) except for the latency-associated transcripts and microRNAs. The functions of latency-associated transcripts have been investigated since 1987. Roles have been suggested relating to reactivation, establishment of latency, neuronal protection, antiapoptosis, apoptosis, virulence and asymptomatic shedding. Here, we review HSV-1 latent infections, reactivation, recurrent disease and antiviral therapies for the ocular HSV diseases.

Association of HSV-1 antigen distribution in the cornea with clinical characteristics of herpetic stromal keratitis

PURPOSE

To investigate whether the clinical characteristics of stromal herpetic simplex keratitis (HSK) are associated with herpes simplex virus type 1 (HSV-1) antigens distribution in the pathologic cornea.

MATERIALS AND METHODS

Pathologic corneal buttons from 8 eyes were obtained during keratoplasty at the Shandong Eye Institute from 2006 to 2009. Immunohistochemical examination was performed to detect the distribution of HSV-1 antigens, including position, depth, and load in the cornea.

RESULTS

Each of the 8 pathologic corneal buttons was positive for HSV-1 antigen by immunohistochemical staining, and HSV-1 antigen was detected in the corneal stroma but not in the corneal epithelium or endothelium. Combined with the clinical characteristics, it was found that the distribution depth of HSV-1 antigen in the cornea was partly related to the disease course, and the load was related to the delay time for treatment. Furthermore, HSK could be effectively cured by deep anterior lamellar keratoplasty (DALK).

CONCLUSIONS

The distribution characteristics of HSV-1 in HSK corneal stroma supports the theory of HSV-1 latency in the cornea and guides the selection of DALK, rather than penetrating keratoplasty (PKP), for clinical stromal HSK treatment.

Circulating herpes simplex type 1 (HSV-1)-specific CD8+ T cells do not access HSV-1 latently infected trigeminal ganglia

Background

Therapeutic vaccines can be designed to enhance existing T cell memory populations for increased protection against re-infection. In the case of herpes simplex virus type 1, recurrent disease results from reactivation of latent virus in sensory ganglia, which is controlled in part by a ganglia-resident HSV-specific memory CD8⁺ T cell population. Thus, an important goal of a therapeutic HSV-1 vaccine would be to enhance this population.

Methods

HSV-1-infected mice were treated with TAK-779 to block CCR5- and CXCR3-mediated CD8⁺ T cell migration during both acute and latent infections. Additionally, HSV-1-specific CD8⁺ T cells were transferred into HSV-1 latently infected mice to mimic the effect of a therapeutic vaccine, and their migration into trigeminal ganglia (TG) was traced during steady-state latency, or during recovery of the TG-resident memory CD8⁺ T cell population following stress-, and corticosterone-induced depletion and HSV-1 reactivation from latency. Bromodeoxy uridine (BrdU) incorporation measured cell proliferation in vivo.

Results

TAK-779 treatment during acute HSV-1 infection reduced the number of infiltrating CD8⁺ T cells but did not alter the number of viral genome copies. TAK-779 treatment during HSV latency did not affect the size of the TG-resident memory CD8⁺ T cell population. Transferred HSV-specific CD8⁺ T cells failed to access latently infected TG during steady-state latency, or during recovery of the TG resident HSV-specific CD8⁺ T cell population following exposure of latently infected mice to stress and corticosterone. Recovery of the HSV-specific CD8⁺ T cell population after stress and corticosterone treatment occurred with homeostatic levels of cell division and did not require CD4⁺ T cell help.

Conclusions

Our findings are consistent with the notion that the CD8⁺ T cells in latently infected TG are a tissue-resident memory (Trm) population that is maintained without replenishment from the periphery, and that when this population is disrupted, it recovers without proliferation or detectable recruitment of HSV-specific CD8⁺ T cells from the blood. The compartmentalization of the HSV-specific CD8⁺ memory T cell population in latently infected TG will complicate the design of therapeutic vaccines.

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.

Corneal latency and transmission of herpes simplex virus-1

The transmission of herpes simplex virus (HSV)-1 by corneal transplantation has rarely been reported. It is believed that these cases have resulted either from reactivated virus traveling from the trigeminal ganglion to the cornea or from latent HSV-1 in the donor cornea itself. Studies of long-term viral presence in corneal tissue have sought to determine whether there is evidence of true non-neuronal latency, although there are problems in its definition. Recent studies provide new insights into neuronal latency, while similar HSV-1 gene regulation in the cornea may implicate corneal latency in pathophysiology and as a potential risk for transplant recipients. This issue has led to concerns over eye banking, which currently screens for other infectious agents but not HSV-1. Here we review the literature regarding corneal latency and the transmission of HSV-1.

Human herpes simplex virus keratitis: the pathogenesis revisited

Infections with several members of the human herpesviruses are the cause of significant ocular morbidity. Of the human herpesviruses, HSV-1 is the most frequent cause of primary and recurrent eye disease. Despite the availability of effective antiviral treatment, recurrent HSV-1 infection continues to be the leading cause of corneal blindness in industrialized nations. This review recapitulates the current insights in the role of the virus and the intra-corneal T cell response involved in the pathogenesis of human HSV-1-induced keratitis.

Clinical, virological, and immunological parameters associated with superinfection of latently with FeHV-1 infected cats

Infections with feline herpesvirus type 1 (FeHV-1) are frequently associated with recurrent ocular disease, which may occur even in vaccinated cats. The underlying pathogenesis is poorly understood. Specifically, the role of circulating, superinfecting virus strains is unknown. To begin addressing this complex question, we reconstituted a marker-tagged mutant FeHV-1 from a bacterial artificial chromosome (BAC) harboring the FeHV-1 genome. This mutant was deleted for the glycoprotein G gene (DeltagG) but carried instead a gene encoding the green fluorescent protein (GFP). Nine latently with wild-type (wt) FeHV-1-infected cats were superinfected with this mutant and monitored for clinical, virological, and immunological parameters. While the mutant virus replicated locally, induced a rise in neutralizing antibody titers, and stimulated the interferon system, no evidence for ocular illness or reactivation of the underlying wtFeHV-1-infection was detected. However, cyclophosphamide-dexamethasone (C-D) treatment, applied 16 months after the superinfection, was able to reactivate wtFeHV-1. Reactivation was accompanied by recrudescence of ocular disease signs. In contrast, reactivation of the superinfecting mutant virus was not detected. Since kittens are normally infected with wtFeHV-1 prior to the first immunization, the data described in this study may be valuable for designing future live attenuated FeHV-1 vaccines.

Fewer latent herpes simplex virus type 1 and cytotoxic T cells occur in the ophthalmic division than in the maxillary and mandibular divisions of the human trigeminal ganglion and nerve

Following primary infection of the mouth, herpes simplex virus type 1 (HSV-1) travels retrogradely along the maxillary (V2) or mandibular (V3) nerve to the trigeminal ganglion (TG), where it establishes lifelong latency. Symptomatic HSV-1 reactivations frequently manifest as herpes labialis, while ocular HSV-1 disease is rare. We investigated whether these clinical observations are mirrored by the distribution of latent HSV-1 as well as cytotoxic T-cell infiltration around the nerve cell bodies and in the nerve fibers. The three divisions of the TG were separated by using neurofilament staining and carbocyanine dye Di-I tracing and then screened by in situ hybridization for the presence of HSV-1 latency-associated transcript (LAT). The T-cell distribution and the pattern of cytolytic molecule expression were evaluated by immunohistochemistry. The Di-I-labeled neurons were largely confined to the nerve entry zone of the traced nerve branches. Very few Di-I-labeled neurons were found in adjacent divisions due to traversing fiber bundles. LAT was abundant in the V2 and V3 divisions of all TG but was scarce or totally absent in the ophthalmic (V1) division. CD8(+) T cells were found in all three divisions of the TG and in the respective nerves, clearly clustering in V2 and V3, which is indicative of a chronic inflammation. Only T cells surrounding neurons in the V2 and V3 ganglionic divisions expressed granzyme B. In conclusion, the large accumulation of LAT and cytotoxic T cells in the V2 and V3 but not in the V1 division of the TG reflects the sites supplied by the sensory fibers and the clinical reactivation patterns.

Level of herpes simplex virus type 1 latency correlates with severity of corneal scarring and exhaustion of CD8+ T cells in trigeminal ganglia of latently infected mice

A hallmark of infection with herpes simplex virus type 1 (HSV-1) is the establishment of latency in ganglia of the infected individual. During the life of the latently infected individual, the virus can occasionally reactivate, travel back to the eye, and cause recurrent disease. Indeed, a major cause of corneal scarring (CS) is the scarring induced by HSV-1 following reactivation from latency. In this study, we evaluated the relationship between the amount of CS and the level of the HSV-1 latency-associated transcript (LAT) in trigeminal ganglia (TG) of latently infected mice. Our results suggested that the amount of CS was not related to the amount of virus replication following primary ocular HSV-1 infection, since replication in the eyes was similar in mice that did not develop CS, mice that developed CS in just one eye, and mice that developed CS in both eyes. In contrast, mice with no CS had significantly less LAT, and thus presumably less latency, in their TG than mice that had CS in both eyes. Higher CS also correlated with higher levels of mRNAs for PD-1, CD4, CD8, F4/80, interleukin-4, gamma interferon, granzyme A, and granzyme B in both cornea and TG. These results suggest that (i) the immunopathology induced by HSV-1 infection does not correlate with primary virus replication in the eye; (ii) increased CS appears to correlate with increased latency in the TG, although the possible cause-and-effect relationship is not known; and (iii) increased latency in mouse TG correlates with higher levels of PD-1 mRNA, suggesting exhaustion of CD8+ T cells.

Ocular HSV-1 latency, reactivation and recurrent disease

Ocular infection with HSV-1 continues to be a serious clinical problem despite the availability of effective antivirals. Primary infection with HSV-1 can involve ocular and adenaxial sites and can manifest as blepharitis, conjunctivitis, or corneal epithelial keratitis. After initial ocular infection, HSV-1 can establish latent infection in the trigeminal ganglia for the lifetime of the host. During latency, the viral genome is retained in the neuron without producing viral proteins. However, abundant transcription occurs at the region encoding the latency-associated transcript, which may play significant roles in the maintenance of latency as well as neuronal reactivation. Many host and viral factors are involved in HSV-1 reactivation from latency. HSV-1 DNA is shed into tears and saliva of most adults, but in most cases this does not result in lesions. Recurrent disease occurs as HSV-1 is carried by anterograde transport to the original site of infection, or any other site innervated by the latently infected ganglia, and can reinfect the ocular tissues. Recurrent corneal disease can lead to corneal scarring, thinning, stromal opacity and neovascularization and, eventually, blindness. In spite of intensive antiviral and anti-inflammatory therapy, a significant percentage of patients do not respond to chemotherapy for herpetic necrotizing stromal keratitis. Therefore, the development of therapies that would reduce asymptomatic viral shedding and lower the risks of recurrent disease and transmission of the virus is key to decreasing the morbidity of ocular herpetic disease. This review will highlight basic HSV-1 virology, and will compare the animal models of latency, reactivation, and recurrent ocular disease to the current clinical data.

Detection of virulent feline herpesvirus-1 in the corneas of clinically normal cats

To evaluate the clinically normal feline cornea for the presence of virulent feline herpesvirus-1 (FHV-1), corneas from 31 cats (25 with normal eyes and six with active disease or corneal scarring) euthanased at a shelter were collected. Corneas from two specific pathogen-free cats were included as negative controls. Virus isolation (VI), fluorescent antibody (FA) staining and real-time polymerase chain reaction (rt-PCR) were performed on all samples. The presence or absence of dexamethasone in the media was evaluated for its effect on VI. VI was positive for FHV-1 in six corneas from five cats, all with clinically normal eyes. One cornea was positive for feline calicivirus (FCV) in addition to FHV-1, but only in media that included dexamethasone. Eight corneas were positive on rt-PCR for FHV-1, all from cats with clinically normal eyes. All positive VI samples were confirmed with FA staining. VI and rt-PCR were negative for FHV-1 and FCV in cats with active disease or corneal scarring. Data from this study indicate that virulent FHV-1 and FCV can be present in feline corneas that are clinically normal. Dexamethasone may enhance viral spread through a cell receptor mechanism.

Corneal Toxicity of Cell-Penetrating Peptides That InhibitHerpes simplexVirus Entry

Cell-penetrating peptides (CPPs) inhibit Herpes simplex virus entry at low micromolar concentrations and may be useful either as prophylactic or therapeutic agents for herpetic keratitis. The aim of this study was to assess the in vitro and in vivo toxicity of three CPPs-EB, TAT-C, and HOM (penetratin)-for the cornea. Incubation of primary (HK320) or immortalized (THK320) human keratocytes with the EB peptide (up to 100 microM), bHOMd (up to 200 microM), or TAT-C (up to 400 microM) resulted in no evidence of toxicity using a formazan dye-reduction assay. Similar results were obtained with a human trabecular meshwork cell line (TM-1), primary human foreskin fibroblasts (DP-9), Vero, and HeLa cells with EB and TATC. The bHOMd peptide showed some toxicity in Vero and HeLa cells, with CC50 values of 70 and 93 microM, respectively. The EB peptide did not inhibit macromolecular synthesis in Vero cells at concentrations below 150 microM, although cell proliferation was blocked at concentrations of EB above 50 microM. In vivo toxicity was assessed by applying peptides in Dulbecco's modified Eagle's medium to the cornea 4 times daily for 7 d. At concentrations 1000 times the IC50 values, the EB and bHOM peptides showed no toxicity, whereas TAT-C caused some mild eyelid swelling. Some slight epithelial cell sloughing was seen with the bKLA peptide in vivo. These results suggest that these CPPs-and EB in particular-have a favorable toxicity profile, and that further development is warranted.

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.

Absence of bacterial and viral DNA in bladder biopsies from patients with interstitial cystitis/chronic pelvic pain syndrome

PURPOSE

We examined bladder biopsies from women with interstitial cystitis/chronic pelvic pain syndrome (IC/CPPS) for the presence of bacterial and viral DNA sequences using polymerase chain reaction.

MATERIALS AND METHODS

Bladder biopsies were taken during cystoscopy from patients under investigation for IC/CPPS, or controls undergoing colposuspension for stress incontinence. Biopsies were snap frozen to -70C. After DNA extraction, polymerase chain reaction (PCR) using specific primers for the hypoxanthine-guanine phosphoribosyl transferase gene confirmed the presence of human DNA. PCR for bacterial and viral gene sequences was performed using specific primers. Positive reactions were repeated to confirm the signal.

RESULTS

A total of 92 patients with IC/CPPS (12 who met the National Institute of Diabetes and Digestive and Kidney Diseases criteria and 80 who did not) and 91 controls were recruited. PCR for hypoxanthine-guanine phosphoribosyl transferase gene was positive in all samples. PCR for the 16S ribosomal RNA gene, as well as for adenovirus, cytomegalovirus, herpes simplex virus types I and II, human papillomavirus (all subtypes) and Chlamydia trachomatis were negative in all samples.

CONCLUSIONS

IC/CPPS is not associated with persistence of viral and bacterial DNA in the bladder. A chronic infective etiology for the condition is excluded by these findings.

Cytologic findings, and feline herpesvirus DNA and Chlamydophila felis antigen detection rates in normal cats and cats with conjunctival and corneal lesions

Samples were collected from 36 cats with feline herpesvirus (FHV-1)-related ocular disease (conjunctivitis, epithelial or stromal keratitis, or corneal sequestration), and 17 cats without ocular changes. Corneoconjunctival swabs, scrapings and biopsies were tested in various combinations for presence of FHV-1 DNA using single round (sr) polymerase chain reaction (PCR) and nested PCR (nPCR). Additional swabs from the inferior conjunctival fornix were tested by enzyme-linked immunosorbent assay for Chlamydophila felis antigen. Cytologic evaluation was carried out on conjunctival (cats with conjunctivitis) and corneal (cats with keratitis) cytobrush preparations. FHV-1 DNA was detected by PCR in 14 (39%) cats with ocular disease and 1 (6%) of the control group. Agreement between srPCR and nPCR results was significant (P < 0.01). FHV-1 DNA was detected in 3/7 cats with conjunctivitis, 5/6 cats with epithelial keratitis, 3/11 cats with stromal keratitis, and 3/12 cats with corneal sequestration. There was a significant association (P = 0.0027) between viral presence and epithelial keratitis. However, no significant association was found between viral presence and conjunctivitis (P = 0.059), stromal keratitis (P = 0.15), or corneal sequestration (P = 0.18). With respect to FHV-1 DNA detection, intersample agreement was significant (P < 0.03). No sampling technique seemed more likely than another to harvest detectable viral DNA, except for cats with corneal sequestrum in which viral DNA was not detected using corneoconjunctival swabs. FHV-1 DNA was detected in 6/9 samples with intranuclear inclusion bodies and in 6/7 cats with eosinophils on cytologic examination. All samples tested negative for C. felis antigen.

Evidence for persistence of adenovirus in the tear film a decade following conjunctivitis

Chronic papillary conjunctivitis has been described following adenoviral conjunctivitis. It is unknown however, how long adenovirus is able to persist in the tear film and conjunctiva. To determine if adenovirus persists in the ocular surface following adenoviral conjunctivitis, 304 patients with a history of adenovirus conjunctivitis from whom an adenovirus had been isolated 10 years previously were sent a questionnaire regarding persistent or recurrent symptoms and were invited to attend. Patients were examined and samples of tears and conjunctival cells were collected from both eyes using tear film washes, filter paper, and swabs, the latter for virus isolation. Extracted DNA from the ocular samples was amplified using primers for herpes simplex virus (thymidine kinase) and adenovirus (hexon) genes. Adenovirus amplicons were sequenced and compared to original serotype. Thirty patients attended, 19 of whom had persistent papillary conjunctivitis. Evidence of adenovirus DNA was detected in 17 of 30 patients, 15 of whom also had evidence of a chronic papillary conjunctivitis. Adenovirus DNA was significantly associated with papillary conjunctivitis (P = 0.03). Adenovirus amplicons were successfully sequenced from six patients. Four patients harbored type 3 adenovirus, the same serotype with which they were infected originally 10 years previously. Two patients were infected originally with adenovirus serotype 3 but the current serotype was type 4. Infection of the ocular surface with adenovirus may predispose to the development of a persistent or recurrent conjunctivitis, the presence of which, appears to be associated with evidence of long term persistence of adenovirus DNA.

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.

Development of a reverse transcriptase-polymerase chain reaction assay to detect feline herpesvirus-1 latency-associated transcripts in the trigeminal ganglia and corneas of cats that did not have clinical signs of ocular disease

OBJECTIVE

To develop a reverse transcriptase-polymerase chain reaction (RT-PCR) assay to detect feline herpesvirus-1 (FHV-1) latency-associated transcripts (LATs) in the corneas and trigeminal ganglia of cats that did not have clinical signs of ocular disease.

SAMPLE POPULATION

Corneas and trigeminal ganglia obtained from 21 cats necropsied at the Indiana Animal Disease Diagnostic Laboratory and 25 cats euthanatized at a humane shelter; none of the cats had a recent history of respiratory tract or ocular disease, and all had normal results for ophthalmic examinations.

PROCEDURE

Both corneas and both trigeminal ganglia were harvested from each cat. An initial PCR assay detected FHV-1 DNA in the corneas and trigeminal ganglia. The RNA was then isolated from samples positive for FHV-1 DNA, and an RT-PCR assay was used to detect LATs.

RESULTS

FHV-1 DNA was detected in 45 of 92 (48.9%) corneas and 38 of 92 (41.3%) trigeminal ganglia. In many samples, the RNA had degraded and RT-PCR assay was not possible. Of the samples subjected to RT-PCR assay, none of the 39 corneas but 4 of 16 trigeminal ganglia had positive results when tested for LATs.

CONCLUSIONS AND CLINICAL RELEVANCE

Analysis of the results indicated that a high percentage of cats that did not have clinical signs of ocular disease had detectable FHV-1 DNA in their corneas and trigeminal ganglia. This study documents that the RT-PCR assay can successfully identify LATs and may serve as a tool to better understand the biologic characteristics of FHV-1 and its relationship to clinical disease.

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.

Simian varicella virus DNA is present and transcribed months after experimental infection of adult African green monkeys

To study the pathogenesis of simian varicella virus (SVV) infection in its natural primate host, we inoculated adult SVV-seronegative African green monkeys intratracheally with 10(3)-10(4) PFU of SVV, sacrificed them 11 days, 2, 5, 10, and 12 months postinfection (p.i.), and examined lung, liver, and ganglia for SVV DNA and RNA. PCR analysis revealed SVV DNA in ganglia and viscera at 11 days and 2, 5, and 10 months p.i. Similarly, SVV transcripts corresponding to immediate early (IE), putative early (E), and late (L) SVV open-reading frames (ORFs) were found in liver, lung, and ganglia of most monkeys at multiple intervals for the 12-month study period. SVV-specific antigens were detected in ganglia and liver during acute varicella, but not in ganglia 12 months p.i. Analysis of control tissue (ganglia, lung, and liver) from uninfected SVV-seronegative adult African green monkeys did not reveal SVV DNA, SVV RNA, SVV-specific antigen, or varicella-specific pathological changes. Overall, intratracheal inoculation of SVV in African green monkeys resulted in the presence of viral DNA and transcription of multiple viral genes in many tissues for months after experimental infection.

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.

A cAMP response element within the latency-associated transcript promoter of HSV-1 facilitates induced ocular reactivation in a mouse hyperthermia model

Herpes simplex virus type 1 (HSV-1) recombinant strain 17CRE contains a site-directed mutation in the 7-bp CRE consensus sequence located 38 nucleotides upstream of the transcription start site. Scarified mouse corneas received inoculations of 17syn+ (parent), 17CRE, and rescue 17CREr. Slit lamp examination of herpetic lesions and tear film swabs containing infectious virus showed that 17CRE had the same acute phenotype as 17syn+ and 17CREr. At 4 weeks, when the corneas had healed and latency was established, mice received hyperthermic shock. Eye swabs taken 24 h after hyperthermia showed that 17CRE reactivated significantly less than 17syn+ and 17CREr, while no significant differences were found in HSV-1 DNA genome copy numbers and latent virus in the trigeminal ganglia. These results are evidence that this CRE site in the LAT promoter facilitates ocular HSV-1 reactivation in mice.

Herpesvirus-mediated systemic delivery of nerve growth factor

Sustained systemic dissemination of therapeutic proteins from peripheral sites is an attractive prospect for gene therapy applications. Replication-defective genomic herpes simplex virus type 1 (HSV-1) vectors were evaluated for their ability to express nerve growth factor (NGF) as a model gene product both locally and systemically. Intra-articular inoculation of NGF expression vectors in rabbits resulted in significant increases in joint lavage and blood plasma NGF that persisted for 1 year. A rhesus macaque injected intra-articularly displayed a comparable increase in plasma NGF for at least 6 months, at which time the serum NGF levels of this animal were sufficient to cause differentiation of PC12 cells in culture, but not to increase footpad epidermis innervation. Long-term reporter transgene expression was observed primarily in ligaments, a finding confirmed by direct inoculation of patellar ligament. Patellar ligament inoculation with a NGF vector resulted in elevated levels of circulating NGF similar to those observed following intra-articular vector delivery. These results represent the first demonstration of sustained systemic release of a transgene product using HSV vectors, raising the prospect of new applications for HSV-1 vectors in the treatment of systemic disease.

Tegument-specific, virus-reactive CD4 T cells localize to the cornea in herpes simplex virus interstitial keratitis in humans

Herpes stromal keratitis (HSK) is a prevalent and frequently vision-threatening disease associated with herpes simplex virus type 1 (HSV-1) infection. In mice, HSK progression occurs after viral clearance and requires T cells and neutrophils. One model implicates Th1-like CD4 T cells with cross-reactivity between the HSV-1 protein UL6 and a corneal autoantigen. HSK can be prevented by establishing specific immunological tolerance. However, HSK can also occur in T-cell receptor-transgenic X SCID mice lacking HSV-specific T cells. To study the pathogenesis of HSK in the natural host species, we measured local HSV-specific T-cell responses in HSK corneas removed at transplant surgery (n = 5) or control corneas (n = 2). HSV-1 DNA was detected by PCR in two specimens. HSV-specific CD4 T cells were enriched in three of the five HSK specimens and were not detectable in the control specimens. Reactivity with peptide epitopes within the tegument proteins UL21 and UL49 was documented. Responses to HSV-1 UL6 were not detected. Diverse HLA DR and DP alleles restricted these local responses. Most clones secreted gamma interferon, but not interleukin-5, in response to antigen. HSV-specific CD8 cells were also recovered. Some clones had cytotoxic-T-lymphocyte activity. The diverse specificities and HLA-restricting alleles of local virus-specific T cells in HSK are consistent with their contribution to HSK by a proinflammatory effect.

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.

Feline herpesvirus

Feline herpesvirus infection is extremely common and may lead to recurring ocular disease in the adult cat. Recognition of the history and clinical signs that are consistent with FHV-1 infection is critical because diagnostic tests may be negative. Although a variety of treatment options are available, no one therapy is successful in every cat, and a small percentage of cats respond poorly to any treatment.

Graft failure in human donor corneas due to transmission of herpes simplex virus

AIM

To report the clinical consequences of contamination of human donor corneas by herpes simplex virus (HSV) in organ culture.

METHODS

Two patients without previous history of ocular HSV infection underwent penetrating keratoplasty (PK), one for keratoconus and the other for Fuchs' endothelial dystrophy. One patient suffered primary graft failure while the other developed a persistent epithelial defect, ultimately resulting in graft failure. Viral culture of swabs taken from both corneas during the early postoperative period was undertaken. The failed donor corneas were examined histopathologically by immunohistochemistry (IHC) for HSV-1 antigens, transmission electron microscopy (TEM), and by polymerase chain reaction (PCR) for HSV DNA. Both failed corneas were replaced within 6 weeks of the initial surgery. The records of the fellow donor corneas were also examined for evidence of infection.

RESULTS

HSV was cultured from both corneas during the early postoperative period. Histology of both donor corneas demonstrated a thickened corneal stroma with widespread necrosis of keratocytes and loss of endothelial cells. IHC showed keratocytes positive with antibodies to HSV-1 antigens. TEM demonstrated HSV-like viral particles within degenerating keratocytes. PCR performed on the failed corneal grafts was positive for HSV-1 DNA, whereas PCR performed on the excised host corneal buttons was negative in both patients. Records of the fellow donor corneas showed that one cornea was successfully transplanted into another recipient after 18 days in organ culture, whilst the other was discarded because of extensive endothelial cell necrosis noted after 15 days in organ culture.

CONCLUSION

HSV within a donor cornea may cause endothelial destruction in organ culture and both primary graft failure and ulcerative keratitis after transplantation. Endothelial necrosis of a donor cornea in culture also raises the possibility of HSV infection within the fellow cornea.

Advances in diagnosis and management of herpetic uveitis

Herpetic eye disease is common and is frequently associated with intraocular inflammation or uveitis. Despite recent advances in measuring anti-herpes virus antibodies and viral DNA in ocular fluids, diagnosis remains largely clinical. The two more common syndromes include anterior uveitis, often associated with keratitis, and the acute retinal necrosis (ARN) syndrome. Treatment is complex and requires careful monitoring to provide the appropriate balance of antiviral medication and corticosteroids. Long-term prophylaxis with oral antiviral agents may be required in selected patients to help prevent the vision-compromising complications associated with recurrences.

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.

Valacyclovir for the prevention of recurrent herpes simplex virus eye disease after excimer laser photokeratectomy

PURPOSE

A variety of factors have been reported as inducing the reactivation of latent herpes simplex virus (HSV), among them stress, trauma, and UV radiation. Excimer laser photorefractive keratectomy (PRK) is a surgical procedure utilizing a 193 nm ultraviolet light to alter the curvature of the cornea and hence correct vision. Reactivation of ocular herpes simplex keratitis following such excimer laser PRK has been reported. All published cases of HSV reactivation following excimer laser treatment in humans are reviewed. The present study evaluates whether stress, trauma of the corneal de-epithelialization prior to the laser, or the excimer laser treatment itself to the stromal bed induces this ocular reactivation of the latent HSV, and whether a systemic antiviral agent, valacyclovir, would prevent such laser PRK-induced reactivation of the HSV.

METHODS

Forty-three normal 1.5- to 2.5-kg New Zealand white rabbits were infected on the surface of the cornea with HSV-1, strain RE. The animals were monitored until resolution, and then all animals were divided into 5 treatment groups: (1) de-epithelialization only, intraperitoneal (i.p.) saline for 14 days; (2) de-epithelialization plus laser, i.p. saline for 14 days; (3) de-epithelialization plus laser, valacyclovir 50 mg/kg per day i.p. for 14 days; (4) de-epithelialization plus laser, valacyclovir 100 mg/kg per day i.p. for 14 days; (5) de-epithelialization plus laser, valacyclovir 150 mg/kg per day i.p. for 14 days. Animals were evaluated in a masked fashion by clinical examination biweekly and viral cultures biweekly through day 28.

RESULTS

The reactivation rates were as follows: group 1, 0%; group 2, 67%; group 3, 50%; group 4, 17%; and group 5, 0%. Viral titers were negative in animals that had no reactivation but persistently positive in those that had reactivation (day 6 through day 28).

CONCLUSIONS

Excimer laser (193 nm) treatment can trigger reactivation of ocular herpes disease (67%) and viral shedding in the latently infected rabbit. De-epithelialization alone is not sufficient to cause reactivation or viral shedding. Prophylaxis with intraperitoneal valacyclovir decreases the recurrence rate in a dose-response fashion. At 150 mg/kg per day, there are no recurrences. The presence of persistent viral shedding in reactivated animals may correlate with cases of late HSV recurrence reported in humans undergoing excimer treatment. The data suggest that humans undergoing excimer laser procedures for correction of refractive errors or treatment of corneal scars with a history of herpetic keratitis are at increased risk for reactivation. Such patients, however, may appropriately be considered for prophylactic systemic antiviral medication at the time of the laser procedure in order to decrease the possibility of recurrence.

Dominant negative suppression of major histocompatibility complex genes occurs in trophoblasts

BACKGROUND

Polymorphic class I and II major histo-: compatibility complex (MHC) genes are not transcribed in trophoblasts although many immune system cells express these genes constitutively. To study the molecular biology of MHC suppression for the purposes of potential transgenic animal development, we examined the effect on MHC expression in B cells by fusing them with trophoblasts.

METHODS

Trophoblasts and B cells with separate selection markers were fused with polyethylene glycol. After growth in double selection media, the hybrids were analyzed for HLA-A, -B, -C, -DR, -DP, and -DQ expression by fluorescence-activated cell scanning and class I and II mRNA by Northern blotting. Class II promoter activity in trophoblasts was then analyzed by transfection of a lethal reporter construct and subsequently, the class II transactivator.

RESULTS

Class I and II surface antigens and their corresponding mRNA were completely suppressed in the hybrids. The lethal reporter construct demonstrated that class II suppression resulted from lack of activation of the class II promoter. This in turn was caused by lack of functional class II transactivator.

CONCLUSIONS

These data indicate that dominant negative trophoblast factors, either directly or indirectly, suppress expression of the MHC genes. If these factors can be cloned, the potential exists for developing transgenic animals that cannot express MHC or peptide antigen to T cell receptors through the MHC system.