Overexpression of Interleukin-2 by a Recombinant Herpes Simplex Virus Type 1 Attenuates Pathogenicity and Enhances Antiviral Immunity

Allen

et al. 2016

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F ollowing ocular infection with herpes simplex virus type 1 (HSV-1), the virus travels in a retrograde direction toward neuronal cell bodies and establishes latency in trigeminal ganglia (TG) of infected mice (1-3). After establishment of latency in neurons, the latency-associated transcript (LAT) is the only viral product consistently detected in abundance in infected mouse, rabbit, and human TG (4-9). LAT is important for the high, wildtype (WT) rate of in vivo spontaneous (10) and induced (4) reactivation from latency. At various times throughout the life of the latently infected individual, the latent virus spontaneously reactivates and returns to the eye in an anterograde direction (1-3). The eye disease that is broadly referred to as herpes stromal keratitis (HSK) or corneal scarring (CS) occurs mainly as the result of virus reactivation rather than primary ocular infection in humans (11-15).Neurovirulence of HSV-1 strains can influence the eye disease in ocularly infected mice (16,17). Based on neurovirulence in animal studies, HSV-1 strains can be classified into two main categories: (i) avirulent HSV-1 strains, such as strains KOS and RE, which do not kill BALB/c mice or New Zealand White (NZW) rabbits following ocular infection and do not replicate efficiently in the eye without corneal scarification, and (ii) virulent HSV-1 strains, such as McKrae and its LAT (Ϫ) -derived virus, dLAT2903, that kill ϳ80% and ϳ50% of BALB/c mice and NZW rabbits, respectively, following ocular infection (18-21) and do not require corneal scarification for efficient ocular infection. Thus, in addition to the presence of LAT, the degree of HSV-1 virulence can also influence the level of recurrence.Following ocular infection, latent HSV genomes express LAT in a portion of those neurons maintaining them, and virus can be recovered by cocultivation of ex-planted ganglia (22-24). In contrast to spontaneous reactivation in rabbits and humans, spontaneous reactivation in the murine model of ocular HSV-1 is rare (25). Previously, it was suggested that the HSV-1 genome is maintained in a quiescent state in sensory neurons during latency in mice due to the absence of detectable viral protein synthesis. However, studies from mice indicate that lytic transcripts and proteins

Section: Reactivation Correlates With the Amount Of Latency In Wt Butsupporting

confidence: 82%

Interrelationship of Primary Virus Replication, Level of Latency, and Time to Reactivation in the Trigeminal Ganglia of Latently Infected Mice

Matundan

Allen

et al. 2016

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“…Although evidence has accumulated that infectious agents, particularly viral agents, may be involved (42,43); this, however, remains controversial (44)(45)(46). Previously, to show the involvement of higher levels of IL-2 in combination with viral infection in CNS demyelination, we constructed a recombinant HSV-1 strain constitutively expressing mIL-2, referred to as HSV-IL-2 (13). We have shown that infection of different strains of mice with the HSV-IL-2 recombinant resulted in CNS demyelination (17,18).…”

Section: Discussionmentioning

confidence: 99%

“…The McKrae virus strain is virulent at an infectious dose of 2 ϫ 10 5 PFU/eye, whereas the KOS virus strain and HSV-IL-2 are attenuated. We have shown previously that the recombinant HSV-IL-2 expresses IL-2 at high levels in different tissues (13).…”

Section: Ethicsmentioning

confidence: 99%

“…Female BALB/c and C57BL/6 mice (age, 6 weeks) were purchased from The Jackson Laboratory. Plaque-purified HSV-1 strain McKrae (virulent wild type) or KOS (avirulent wild type) and a recombinant HSV-1 strain expressing IL-2 (13) were grown in rabbit skin (RS) cell monolayers in minimal essential medium (MEM) containing 5% fetal calf serum (FCS), as described previously (13,14,16). The McKrae virus strain is virulent at an infectious dose of 2 ϫ 10 5 PFU/eye, whereas the KOS virus strain and HSV-IL-2 are attenuated.…”

Section: Ethicsmentioning

confidence: 99%

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Role of Interleukin-2 and Herpes Simplex Virus 1 in Central Nervous System Demyelination in Mice

Zandian

Allen

et al. 2013

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We have reported previously that ocular infection of different strains of mice with recombinant herpes simplex virus 1 (HSV-1) constitutively expressing interleukin-2 (IL-2) provokes central nervous system (CNS) demyelination and optic neuropathy, as determined by changes in visual evoked cortical potentials and pathological changes in the optic nerve and CNS, whereas recombinant viruses expressing IL-4, gamma interferon, IL-12p35, IL-12p40, or IL-12p70 do not induce this neuropathy. The goal of this study was to dissect the mechanism underlying the interplay between the immune system (elevation of IL-2) and an environmental factor (infection with HSV-1) that elicits this pathology. Similar results were obtained upon delivery of IL-2 into the mouse brain using osmotic minipumps or injection of mice with recombinant IL-2 protein, IL-2 DNA, or IL-2 synthetic peptides prior to infection with wild-type (wt) HSV-1 strains McKrae and KOS. The critical role of IL-2 is further supported by our data, indicating that a single mutation at position T27A in IL-2 completely blocks the HSV-1-induced pathology. This study shows a novel model of autoimmunity in which viral infection and enhanced IL-2 cause CNS demyelination. Several lines of evidence implicate interleukin-2 (IL-2) in the pathology of multiple sclerosis (MS) (1-4). Patients with MS have elevated levels of IL-2 in their sera and cerebrospinal fluid (CSF) (1-4). The soluble IL-2 receptor (sIL-2R) is also elevated in the sera and CSF of patients with MS (3, 5-10). These clinical findings of elevated IL-2 levels (and lower than normal IL-4 levels) in the sera of MS patients suggest a possible link between IL-2 and the onset of MS. Furthermore, supernatants harvested from T lymphocytes of MS patients cause damage to myelin and glial cells in vitro (11,12), suggesting that the MS T lymphocytes produce demyelination factors and are activated in vivo.In order to investigate the role of cytokines in demyelination in a viral model of MS, we had constructed a panel of recombinant herpes simplex virus 1 (HSV-1) isolates that constitutively express murine cytokines, including IL-2 (13), IL-4, gamma interferon (IFN-␥), . Using these viruses, we have shown that infection of different strains of mice with a recombinant HSV-1 strain constitutively expressing IL-2 (HSV-IL-2), but not HSV-IL-4, HSV-IFN-␥, HSV-IL-12p35, or HSV-IL12p40, results in demyelination of the optic nerves (ONs), the spinal cords (SCs), and the brains of the infected mice, as determined by histologic examination of tissues obtained at necropsy (17,18). In addition, the HSV-IL-2-infected mice developed optic neuropathy, as determined by changes in the visual evoked cortical potentials (VECPs) (18). Using knockout mice, depletion, and transfer studies, we found that both CD8 ϩ and CD4 ϩ T cells contributed to HSV-IL-2-induced central nervous system (CNS) demyelination, with CD8 ϩ T cells being the primary inducers (19). We have also found that infection of mice with a recombinant HSV-1 isolate expressing IL-12p...

“…We performed sitespecific mutagenesis within the gK 8mer region and inserted the complete open reading frame (ORF) of the mutated form of the gK gene into both copies of the latency-associated transcript (LAT) regions and under the LAT promoter as we described previously (34,(37)(38)(39)(40). Since suitable antibodies for detection of gK are not available, we inserted the myc epitope tag in-frame at the 3= end of the mutated gK ORF for identification of the inserted gK.…”

mentioning

confidence: 99%

Mutations within the Pathogenic Region of Herpes Simplex Virus 1 gK Signal Sequences Alter Cell Surface Expression and Neurovirulence

Matundan

Akhtar

et al. 2015

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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. IMPORTANCEIn 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. Herpes simplex virus 1 (HSV-1) infections are among the most frequent serious viral eye infections in the United States and are a major cause of virus-induced blindness (1-3). It is estimated that 70 to 90% of American adults have antibodies to HSV-1 and/or HSV-2 and ca. 25% of these individuals have clinical symptoms upon routine clinical inquiry. HSV-1 is responsible for Ͼ90% of ocular HSV infections (1, 2, 4-7). HSV-1-induced corneal scarring (CS), also broadly referred to as herpes stromal keratitis (HSK), can lead to blindness. Furthermore, HSV-1 is the leading cause of corneal blindness due to an infectious agent in developed countries (1, 2, 4-7). In addition to necrotizing HSK, ocular infection with HSV-1 can cause eye disease ranging in severity from blepharitis, conjunctivitis, and dendritic keratitis to disciform stromal edema (4, 7-11). In the United States, approximately 30,000 people per year suffer recurrent ocular HSV episodes, requiring doctor visits, medication, and in severe cases, corneal transplants.Although it is well established that HSV-1-induced CS is due to immune responses to the virus, the exact...