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

Long-term outcomes of the Boston type I keratoprosthesis in eyes with previous herpes simplex virus keratitis

Purpose

To report the long-term outcomes of the Boston type I keratoprosthesis (Kpro) in eyes with prior herpes simplex virus (HSV) keratitis.

Methods

Retrospective review of all Kpro procedures performed by a single surgeon from 1 May 2004 to 1 January 2015.

Results

13 of 173 Kpro procedures were performed in 11 eyes with prior HSV keratitis. There was not a significant difference in the percentage of eyes with and without prior HSV keratitis with preoperative (9% vs 8%, p=1.00) or postoperative (57% vs 60%, p=1.00) corrected distance visual acuity (CDVA) ≥20/200 or in the percentage of contralateral eyes with preoperative CDVA ≥20/50 (55% vs 30%, p=0.18). While several postoperative complications occurred approximately twice as often in eyes with prior HSV keratitis, including persistent epithelial defect (63.6% vs 34.1%; p=0.10), corneal infiltrate (27.3% vs 12.3%; p=0.17) and sterile vitritis (18.2% vs 9.4%; p=0.31), only cystoid macular oedema (45.5% vs 12.3%; p=0.01) was significantly more common. Similarly, while the Kpro retention failure rate in eyes with prior HSV keratitis was twice than that in eyes without it (0.15 vs 0.07 per year), the difference was not statistically significant (p=0.09).

Conclusion

As greater than half of patients with unilateral HSV keratitis undergoing Kpro implantation have CDVA ≥20/50 in the contralateral eye, and as the Kpro retention failure rate in eyes with prior HSV keratitis is twice than that in eyes without prior HSV keratitis, caution should be exercised when considering Kpro implantation in these patients.

Mutations within the pathogenic region of herpes simplex virus 1 gK signal sequences alter cell surface expression and neurovirulence

To investigate the role of the signal sequences of herpes simplex virus 1 (HSV-1) gK on virus replication and viral pathogenesis, we constructed recombinant viruses with or without mutations within the signal sequences of gK. These recombinant viruses expressed two additional copies of the mutated (MgK) or native (NgK) form of the gK gene in place of the latency-associated transcript with a myc epitope tag to facilitate detection at their 3' ends. The replication of MgK virus was similar to that of NgK both in vitro and in vivo, as well as in the trigeminal ganglia (TG) of latently infected mice. The levels of gB and gK transcripts in the corneas, TG, and brains of infected mice on days 3 and 5 postinfection were markedly virus and time dependent, as well as tissue specific. Mutation in the signal sequence of gK in MgK virus blocked cell surface expression of gK-myc in rabbit skin cells, increased 50% lethal dose, and decreased corneal scarring in ocularly infected mice compared to the NgK or revertant (RgK) virus. MgK and NgK viruses, and not the RgK virus, showed a reduced extent of explant reactivation at the lower dose of ocular infection but not at the higher dose. However, the time of reactivation was not affected by overexpression of the different forms of gK. Taken together, these results strongly suggest that the 8mer peptide (ITAYGLVL) within the signal sequence of gK promotes cell surface expression of gK in infected cells and ocular pathogenesis in infected mice.

IMPORTANCE

In this study, we show for the first time that mutations within the signal sequence of gK blocked cell surface expression of inserted recombinant gK in vitro. Furthermore, this blockage in cell surface expression was correlated with higher 50% lethal dose and less corneal scarring in vivo. Thus, these studies point to a key role for the 8mer within the signal sequence of gK in HSV-1-induced pathogenicity.

Binding of HSV-1 glycoprotein K (gK) to signal peptide peptidase (SPP) is required for virus infectivity

Glycoprotein K (gK) is a virion envelope protein of herpes simplex virus types 1 (HSV-1) and 2 (HSV-2), which plays important roles in virion entry, morphogenesis and egress. Two-hybrid and pull-down assays were utilized to demonstrate that gK and no other HSV-1 genes specifically binds to signal peptide peptidase (SPP), also known as minor histocompatibility antigen H13. SPP dominant negative mutants, shRNA against SPP significantly reduced HSV-1 replication in vitro. SPP also affected lysosomes and ER responses to HSV-1 infection. Thus, in this study we have shown for the first time that gK, despite its role in fusion and egress, is also involved in binding the cytoplasmic protein SPP. These results also suggest that SPP plays an important role in viral replication and possibly virus pathogenesis. This makes SPP unique in that its function appears to be required by the virus as no other protein can compensate its loss in terms of viral replication.

Herpes simplex virus keratitis: histopathology and corneal allograft outcomes

Molecular biologic studies have elucidated the roles of specific and innate immune responses in the pathogenesis of HSV keratitis. Recent evidence suggests that interference with innate immune mechanisms may reduce the severity of HSV keratitis and its complications. The agents targeting innate immune responses are particularly amenable to translational therapy for patients at risk of complications of HSV keratitis and poor corneal transplant outcomes. Histopathologic evidence of neovascularization or inflammation in tissue removed at the time of corneal transplantation predicts patients who are at risk for allograft rejection or failure. Such patients are prime candidates for close monitoring and intensive therapy. Newer imaging techniques, such as clinical confocal biomicroscopy, might be useful in identifying neovascularization and inflammation that place patients at high risk for poor allograft outcomes prior to corneal transplantation.

Herpes simplex epithelial and stromal keratitis: an epidemiologic update

Herpes simplex virus (HSV) is associated with a variety of ocular diseases, including epithelial and stromal keratitis. HSV can cause stromal opacification and is believed to be the leading cause of infectious blindness in the developed world. An improved understanding of the global burden of HSV keratitis, including the incidence of severe vision loss, could have a significant effect on prevention and treatment and place it in perspective among causes of corneal ulceration. We found that the global incidence of HSV keratitis is roughly 1.5 million, including 40,000 new cases of severe monocular visual impairment or blindness each year. We also discuss relevant epidemiologic issues regarding HSV epithelial and stromal disease.

Herpes simplex virus keratitis: histopathologic neovascularization and corneal allograft failure

PURPOSE

To identify whether histopathologic presence of neovascularization is predictive for allograft failure following penetrating keratoplasty for herpes simplex virus (HSV) keratitis.

METHODS

Retrospective, interventional case series of 62 consecutive patients with HSV keratitis who underwent penetrating keratoplasty at the Kellogg Eye Center between 1990 and 2000. Reviews of the patients' clinical charts and the histopathologic slides of their excised corneal buttons were performed to identify associations between histopathologic neovascularization and clinical outcomes.

MAIN OUTCOME MEASURE

To determine whether histopathologic presence of neovascularization predicts allograft failure.

RESULTS

Histopathologic presence of neovascularization was present in 31% of corneal specimens and predicted subsequent allograft failure (P = 0.002) and HSV recurrence (P = 0.05).

CONCLUSION

Histopathologic presence of neovascularization is a risk factor for corneal allograft failure and HSV recurrence.

Herpes simplex virus keratitis: histopathologic inflammation and corneal allograft rejection

OBJECTIVE

To identify whether histopathologic and immunoassay biomarkers of inflammation are predictive for allograft rejection after penetrating keratoplasty (PKP) for herpes simplex virus (HSV) keratitis.

DESIGN

Retrospective, interventional case series with prospective component of pathologic evaluation of frozen tissue.

PARTICIPANTS

Sixty-two consecutive patients with HSV keratitis who underwent PKP.

METHODS

A chart review and histopathologic examination of the excised host corneal button was performed to identify associations between clinical data and histopathologic presence of inflammation. Enzyme-linked immunosorbent assay for interleukin (IL)-8 and monocyte chemotactic protein-1 (MCP-1) chemokines and immunohistochemical staining for human leukocyte antigen (HLA)-DR and intercellular adhesion molecule-1 (ICAM-1) antigens was also performed in inflamed and noninflamed specimens.

MAIN OUTCOME MEASURES

To determine whether the presence of subclinical inflammation at the time of PKP predicts allograft rejection.

RESULTS

Although 81% of patients had clinically quiescent disease, histopathology revealed that 74% had active corneal inflammation, a finding that was associated with the presence of clinical neovascularization (P = 0.01). Allograft rejections were experienced by 34% of the patients in this cohort. The histopathologic presence of inflammation was a risk factor for allograft rejection (P = 0.02). Corneal specimens demonstrating inflammation had significantly increased IL-8 (P = 0.0005) and MCP-1 (P = 0.003) levels, and greater immunoreactivity for HLA-DR and ICAM-1 when compared with specimens without inflammation. Treatment with IL-10 ex vivo significantly inhibited IL-8 (P = 0.006), and MCP-1 (P = 0.01) chemokines, and qualitatively substantially reduced HLA-DR, but not ICAM-1, expression.

CONCLUSIONS

Histopathologic inflammation is a risk factor for corneal allograft rejection.

Prospects for Developing an Effective Vaccine Against Ocular Herpes Simplex Virus Infection

One of the hallmarks of herpes simplex virus (HSV) infection is the establishment of a lifelong latent infection accompanied by periods of recurrent disease. Primary HSV infections or repeated clinical recurrences do not elicit immune responses capable of completely preventing recurrences of endogenous virus. It is therefore questionable if vaccination approaches that seek to mimic the immune response to natural infection will reduce infection or disease due to an exogenous viral challenge. Approaches to the induction of protective responses by altering or enhancing both innate and adaptive immunity, using novel vaccines specifically tested in models of HSV infections of the eye, such as recombinant viral vaccine vectors and DNA vaccines, are detailed in this review.

HSV keratitis: histopathologic predictors of corneal allograft complications

PURPOSE

To identify histopathologic features predictive for adverse allograft outcomes following penetrating keratoplasty for herpes simplex virus (HSV) keratitis.

METHODS

Retrospective, interventional case series of 62 consecutive patients with HSV keratitis who underwent penetrating keratoplasty at the Kellogg Eye Center from 1990 through 2000. A detailed chart review and review of the histopathology of the excised corneal button were performed to identify associations between clinical data (disease activity, vascularity, adverse allograft outcomes) and histopathologic data (inflammation, neovascularization, biomarkers). The main outcome measure was to find histopathologic features that may predict HSV recurrence, allograft rejection, or failure.

RESULTS

Although 81% of patients had clinically quiescent disease, histopathology revealed that 74% had active corneal inflammation, a finding that was associated with the presence of clinical neovascularization (P = .01). Histopathologic inflammation was a risk factor for allograft rejection (P = .02) but not failure (P = .98) or HSV recurrence (P = .45). Histopathologic neovascularization did not predict rejection (P = .19) but did predict failure (P = .002) and HSV recurrence (P = .05). Biomarkers, including HLA-DR, ICAM-1, and IL-8(CXC) and MCP-1 (CC) chemokines, were all significantly increased in fresh corneal specimens demonstrating moderate to severe inflammation. IL-10 treatment ex vivo significantly inhibited HLA-DR, IL-8 (P = .006), and MCP-1 (P = .01) but did not reduce ICAM-1 expression.

CONCLUSION

Histopathologic inflammation, neovascularization, and the presence of specific biomarkers are risk factors for corneal allograft morbidity.

Effect of prophylactic oral acyclovir after penetrating keratoplasty for herpes simplex keratitis

PURPOSE

To determine the effect of routine use of prophylactic oral acyclovir after penetrating keratoplasty (PK) for herpes simplex virus (HSV) keratitis on recurrence, rejection, and graft failure rates.

METHODS

Records from 70 consecutive patients who underwent PK for HSV keratitis at the W.K. Kellogg Eye Center between August 1, 1990, and December 31, 2000, were reviewed. Data collected included preoperative disease activity, duration, host vascularity, pre- and postoperative vision, and antiviral use. Particular attention was given to all episodes of HSV recurrence, graft rejection, and failure.

RESULTS

Fifty-six patients (80%) were treated with prophylactic oral acyclovir after surgery. This cohort experienced fewer episodes of rejection (P = 0.006) and better overall graft survival (P = 0.04) than those who were not treated with prophylactic oral antivirals. There was no statistically significant difference in recurrence-free survival between the 2 groups (P = 0.22). Cox regression analysis failed to identify any single variable as a statistically significant predictor of recurrence, rejection, or graft failure.

CONCLUSIONS

Prophylactic oral acyclovir use after PK for HSV keratitis is associated with decreased episodes of rejection and improved graft survival.

Ocular herpes simplex: changing epidemiology, emerging disease patterns, and the potential of vaccine prevention and therapy

PURPOSE

To review the changing epidemiology of herpes simplex virus infection, emerging patterns of herpetic ocular disease, and the challenges and promise of herpes simplex virus vaccine therapy.

DESIGN

Perspective.

METHODS

Literature review.

RESULTS

An epidemic increase in genital herpes simplex type 2 infection is reflected in a 30% increase in HSV-2 antibodies in the United States since 1976. Approximately one in four people in the United States over age 30 is infected with HSV-2. Primary acquisition of herpes simplex type 1 is becoming progressively delayed in many industrialized countries, in contrast to developing nations where the virus is acquired early in life and is ubiquitous. Changes in sexual behavior among young adults have been associated with a recent increase in genital HSV-1 infection, resulting from oral-genital rather than genital-genital contact. Clinical trials of HSV vaccines using selected herpes simplex virus type 2 proteins mixed in adjuvant have shown limited efficacy in seronegative women, but not in men.

CONCLUSIONS

The recent epidemic of genital herpes simplex type 2 infection is likely to result in an increase in neonatal ocular herpes and in delayed cases of acute retinal necrosis syndrome. The increase in genital HSV-1 may lead to industry production of vaccines that contain components of both HSV-1 and HSV-2 targeted toward limiting genital disease and transmission. As newer herpes simplex vaccines become available, ophthalmologists must be vigilant that a boost in immunity against HSV does not have a paradoxical effect in exacerbating break-through cases that develop immune-mediated herpes simplex stromal keratitis.

Chlamydia psittaci is variably associated with ocular adnexal MALT lymphoma in different geographical regions

Infectious agents play a critical role in MALT lymphoma development. Studies from Italy showed Chlamydia psittaci infection in 87% of ocular adnexal MALT lymphomas and complete or partial regression of the lymphoma after C. psittaci eradication in four of nine cases. However, C. psittaci was not demonstrated in ocular adnexal MALT lymphomas from the USA. This study was thus designed to investigate further the role of C. psittaci, and other infectious agents commonly associated with chronic eye disease, in the development of ocular adnexal MALT lymphoma. The presence of C. psittaci, C. trachomatis, C. pneumoniae, herpes simplex virus 1 and 2 (HSV1, HSV2), and adenovirus 8 and 19 (ADV8, ADV19) was assessed separately by polymerase chain reaction in 142 ocular adnexal MALT lymphomas, 53 non-marginal zone lymphomas, and 51 ocular adnexal biopsies without a lymphoproliferative disorder (LPD), from six geographical regions. C. psittaci was detected at similar low frequencies in non-LPD and non-marginal zone lymphoma groups from different geographical regions (0-14%). Overall, the prevalence of C. psittaci was significantly higher in MALT lymphomas (22%) than in non-LPD (10%, p=0.042) and non-marginal zone lymphoma cases (9%, p=0.033). However, the prevalence of C. psittaci infection in MALT lymphoma showed marked variation among the six geographical regions examined, being most frequent in Germany (47%), followed by the East Coast of the USA (35%) and the Netherlands (29%), but relatively low in Italy (13%), the UK (12%), and Southern China (11%). No significant differences in the detection of C. pneumoniae, C. trachomatis, HSV1, HSV2, ADV8, and ADV19 were found between lymphomas and controls from different geographical regions. In conclusion, our results show that C. psittaci, but not C. pneumoniae, C. trachomatis, HSV1, HSV2, ADV8 or ADV19, is associated with ocular adnexal MALT lymphoma and that this association is variable in different geographical areas.