Self-reported pain during different phases of orthodontic treatment with fixed appliance: A multi-centre randomized controlled trial in adolescents with crowding

OBJECTIVES

To compare self-reported pain levels across various treatment phases using passive self-ligating (Damon) and conventional (Victory) standardized fixed appliance systems.

MATERIALS AND METHODS

Adolescents (12-17 years old) with crowding and displaced teeth, planned for non-extraction treatment, were recruited from four orthodontic clinics. They were randomized into stratified blocks (1:1 ratio) using concealed allocation to receive Damon Q™ (34 boys, 28 girls) or Victory™ (39 boys, 31 girls). Pain and analgesic intake were assessed on seven different occasions with validated self-report questionnaires using a 10-grade scale.

RESULTS

Of the 132 patients included, six were lost to follow up. Clinically relevant mean pain scores (≥4) were registered in both groups after bonding upper and lower arches and after insertion of 0.019 × 0.025 stainless steel archwire. The highest mean scores were reported on day two after bonding the upper arch (Damon 5.96, Victory 7.18, P = .011). In both groups, at least 40% reported taking analgesics during various treatment phases. The Damon group reported a lower intake of analgesics on days one and two (P = .042 and .037) after treatment initiation. In the entire sample, boys reported significantly higher mean pain scores than girls on the second and third days after bonding (P = .008 and .026, respectively).

CONCLUSIONS

Lower pain levels were reported from the Damon group after bonding. In general, boys reported higher pain than girls did. Clinicians and adolescents need to be aware that clinically relevant pain levels can be expected not only after bonding but also in later phases.

Use of cytokine immunotherapy to block CNS demyelination induced by a recombinant HSV-1 expressing IL-2

We previously have described a model of multiple sclerosis (MS) in which constitutive expression of murine interleukin (IL)-2 by herpes simplex virus type 1 (HSV-1) (HSV-IL-2) causes central nervous system (CNS) demyelination in different strains of mice. In the current study, we investigated whether this HSV-IL-2-induced demyelination can be blocked using recombinant viruses expressing different cytokines or by injection of plasmid DNA. We have found that coinfection of HSV-IL-2-infected mice with recombinant viruses expressing IL-12p35, IL-12p40 or IL-12p35+IL-12p40 did not block the CNS demyelination, and that coinfection with a recombinant virus expressing interferon (IFN)-γ exacerbated it. In contrast, coinfection with a recombinant virus expressing IL-4 reduced demyelination, whereas coinfection of HSV-IL-2-infected mice with a recombinant HSV-1 expressing the IL-12 heterodimer (HSV-IL-12p70) blocked the CNS demyelination in a dose-dependent manner. Similarly, injection of IL-12p70 DNA blocked HSV-IL-2-induced CNS demyelination in a dose-dependent manner and injection of IL-35 DNA significantly reduced CNS demyelination. Injection of mice with IL-12p35 DNA, IL-12p40 DNA, IL-12p35+IL-12p40 DNA or IL-23 DNA did not have any effect on HSV-IL-2-induced demyelination, whereas injection of IL-27 DNA increased the severity of the CNS demyelination in the HSV-IL-2-infected mice. This study demonstrates for the first time that IL-12p70 can block HSV-IL-2-induced CNS demyelination and that IL-35 can also reduce this demyelination, whereas IFN-γ and IL-27 exacerbated the demyelination in the CNS of the HSV-IL-2-infected mice. Our results suggest a potential role for IL-12p70 and IL-35 signaling in the inhibition of HSV-IL-2-induced immunopathology by preventing development of autoaggressive T cells.

Three herpes simplex virus type 1 latency-associated transcript mutants with distinct and asymmetric effects on virulence in mice compared with rabbits

Herpes simplex virus type 1 latency-associated transcript (LAT)-null mutants have decreased reactivation but normal virulence in rabbits and mice. We report here on dLAT1.5, a mutant with LAT nucleotides 76 to 1667 deleted. Following ocular infection of rabbits, dLAT1.5 reactivated at a lower rate than its wild-type parent McKrae (6.1 versus 11.8%; P = 0.0025 [chi-square test]). Reactivation was restored in the marker-rescued virus dLAT1.5R (12.6%; P = 0.53 versus wild type), confirming the importance of the deleted region in spontaneous reactivation. Compared with wild-type or marker-rescued virus, dLAT1.5 had similar or slightly reduced virulence in rabbits (based on survival following ocular infection). In contrast, in mice, dLAT1.5 had increased virulence (P < 0.0001). Thus, deletion of LAT nucleotides 76 to 1667 increased viral virulence in mice but not in rabbits. In contrast, we also report here that LAT2.9A, a LAT mutant that we previously reported to have increased virulence in rabbits (G. C. Perng, S. M. Slanina, A. Yuhkt, B. S. Drolet, W. J. Keleher, H. Ghiasi, A. B. Nesburn, and S. L. Wechsler, J. Virol. 73:920-929, 1999), had decreased virulence in mice (P = 0.03). In addition, we also found that dLAT371, a LAT mutant that we previously reported to have wild-type virulence in rabbits (G. C. Perng, S. M. Slanina, H. Ghiasi, A. B. Nesburn, and S. L. Wechsler, J. Virol. 70:2014-2018, 1996), had decreased virulence in mice (P < 0.05). Thus, these three mutants, each of which encodes a different LAT RNA, have different virulence phenotypes. dLAT1.5 had wild-type virulence in rabbits but increased virulence in mice. In contrast, LAT2.9A had increased virulence in rabbits but decreased virulence in mice, and dLAT371 had wild-type virulence in rabbits but decreased virulence in mice. Taken together, these results suggest that (i) the 5' end of LAT and/or a gene that overlaps part of this region is involved in viral virulence, (ii) this virulence appears to have species-specific effects, and (iii) regulation of this virulence may be complex.

Recombinant herpes simplex virus type 1 expressing murine interleukin-4 is less virulent than wild-type virus in mice

The effect of interleukin-4 (IL-4) on herpes simplex virus type 1 (HSV-1) infection in mice was evaluated by construction of a recombinant HSV-1 expressing the gene for murine IL-4 in place of the latency-associated transcript (LAT). The mutant virus (HSV-IL-4) expressed high levels of IL-4 in cultured cells. The replication of HSV-IL-4 in tissue culture and in trigeminal ganglia was similar to that of wild-type virus. In contrast, HSV-IL-4 appeared to replicate less well in mouse eyes and brains. Although BALB/c mice are highly susceptible to HSV-1 infection, ocular infection with HSV-IL-4 resulted in 100% survival. Furthermore, 57% of the mice survived coinfection with a mixture of HSV-IL-4 and a lethal dose of wild-type McKrae, compared with only 10% survival following infection with McKrae alone. Similar to wild-type BALB/c mice, 100% of IL-4(-/-) mice also survived HSV-IL-4 infection. T-cell depletion studies suggested that protection against HSV-IL-4 infection was mediated by a CD4(+)-T-cell response.

Region of herpes simplex virus type 1 latency-associated transcript sufficient for wild-type spontaneous reactivation promotes cell survival in tissue culture

The latency-associated transcript (LAT) is the only abundant herpes simplex virus type 1 (HSV-1) transcript expressed during latency. In the rabbit eye model, LAT null mutants do not reactivate efficiently from latency. We recently demonstrated that the LAT null mutant dLAT2903 induces increased levels of apoptosis in trigeminal ganglia of infected rabbits compared to LAT+ strains (G.-C. Perng, C. Jones, J. Ciacci-Zarella, M. Stone, G. Henderson, A. Yokht, S. M. Slanina, F. M. Hoffman, H. Ghiasi, A. B. Nesburn, and C. S. Wechsler, Science 287:1500-1503, 2000). The same study also demonstrated that a plasmid expressing LAT nucleotides 301 to 2659 enhanced cell survival of transfected cells after induction of apoptosis. Consequently, we hypothesized that LAT enhances spontaneous reactivation in part, because it promotes survival of infected neurons. Here we report on the ability of plasmids expressing different portions of the 5' end of LAT to promote cell survival after induction of apoptosis. A plasmid expressing the first 1.5 kb of LAT (LAT nucleotides 1 to 1499) promoted cell survival in neuro-2A (mouse neuronal) and CV-1 (monkey fibroblast) cells. A plasmid expressing just the first 811 nucleotides of LAT promoted cell survival less efficiently. Plasmids expressing the first 661 nucleotides or less of LAT did not promote cell survival. We previously showed that a mutant expressing just the first 1.5 kb of LAT has wild-type spontaneous reactivation in rabbits, and a mutant expressing just the first 811 nucleotides of LAT has a reactivation frequency higher than that of dLAT2903 but lower than that of wild-type virus. In addition, mutants reported here for the first time, expressing just the first 661 or 76 nucleotides of LAT, had spontaneous reactivation indistinguishable from that of the LAT null mutant dLAT2903. In summary, these studies provide evidence that there is a functional relationship between the ability of LAT to promote cell survival and its ability to enhance spontaneous reactivation.

Corneal macrophage infiltrates following ocular herpes simplex virus type 1 challenge vary in BALB/c mice vaccinated with different vaccines

Macrophage cell infiltrates in the cornea were examined following ocular herpes simplex virus type 1 (HSV-1) challenge of vaccinated BALB/c mice. Mice were vaccinated with individual HSV-1 glycoproteins, cocktails of different HSV-1 glycoproteins, or live avirulent HSV-1 (strain KOS). Cryostat sections of cornea were taken at different times after challenge and reacted with M1/70, F4/80, BM8, or MOMA-1 monoclonal antibodies. The pattern of macrophage responses in the cornea differed depending on the vaccine that was given prior to HSV-1 ocular challenge. No macrophage response was detected in mice vaccinated with the highly protective 5gPs consisting of the five glycoproteins gB, gC, gD, gE, and gI. In contrast, mock vaccinated mice and mice vaccinated with gK, which is known to exacerbate HSV-1 induced eye disease, had high sustained macrophage responses. Mice vaccinated with 7gPs (5gPs+gG and gH) had moderate levels of macrophages. It appeared that (1) the most effective vaccines induced no detectable infiltrating macrophages in the eyes, while the least efficacious vaccines had very high levels of infiltrating macrophages; (2) presence of CD11b(+) cells in the cornea appeared to correlate with enhanced blepharitis, but did not appear to affect corneal scarring; and (3) presence of F4/80(+) cells in the cornea tended to correlate with increased corneal scarring.

The US5 open reading frame of herpes simplex virus type 1 does encode a glycoprotein (gJ)

Based on sequence analysis, the protein encoded by the US5 open reading frame (ORF) of herpes simplex virus type 1 (HSV-1) was predicted to contain an N-glycosylation site and was given the designation of glycoprotein J (gJ). However, the US5 gene product has not been identified and the identity of gJ as a glycoprotein has not been confirmed. We have cloned and expressed the DNA encoding the complete sequence of the US5 ORF, using a baculovirus expression system. Western blotting, using polyclonal antibody raised against synthetic US5 peptides, revealed two major baculovirus-US5-expressed protein bands with apparent molecular weights of 16-17 and 10 kD. The recombinant US5 was found on the membrane of Spodoptera frugiperda cells and was susceptible to tunicamycin, endoglycosidase H, glycosidase F and partially resistant to endoglycosidase F. Vaccination of mice with baculovirus-expressed US5 did not induce a neutralizing antibody to HSV-1 or provide protection against lethal HSV-1 challenge. However, serum from these vaccinated mice was able to recognize US5 in purified HSV-1 virions by Western blot analyses and on the surface of HSV-1-infected cells by immunofluorescence. These findings establish that US5 does encode a glycoprotein and confirm the appropriateness of naming the US5 gene product gJ.

Antibody-dependent enhancement of HSV-1 infection by anti-gK sera

We previously reported that vaccination of BALB/c mice with the baculovirus expressed HSV-1 glycoprotein K (gK) or passive transfer of gK purified IgG to naive BALB/c mice causes severe exacerbation of HSV-1 induced corneal scarring following ocular challenge. In addition, a productive chronic infection, rather than a latent infection, is found in most trigeminal ganglia. These phenomena are accompanied by a very high T(H)1+T(H)2 response in the eye (Ghiasi, H., Cai, S., Nesburn, A.B., Wechsler, S.L., 1996. Vaccination with herpes simplex virus type 1 glycoprotein K impairs clearance of virus from the trigeminal ganglia resulting in chronic infection. Virology 224, 330-333; Ghiasi, H., Cai, S., Slanina, S., Nesburn, A. B., Wechsler, S.L., 1997. Nonneutralizing antibody against the glycoprotein K of herpes simplex virus type-1 exacerbates herpes simplex virus type-1-induced corneal scarring in various virus-mouse strain combinations. Invest. Ophthalmol. Vis. Sci. 38, 1213-1221; Ghiasi, H., Hofman, F.M., Cai, S., Perng, G.C., Nesburn, A.B., Wechsler, S.L., 1999. Vaccination with different HSV-1 glycoproteins induces different patterns of ocular cytokine responses following HSV-1 challenge of vaccinated mice. Vaccine 17, 2576-2582). In the studies reported here, we investigated the hypothesis that anti-gK serum produces antibody-dependent enhancement (ADE) of ocular HSV-1 infection. We found that gK vaccinated mice had significantly higher HSV-1 titers in their eyes than gD or mock-vaccinated mice and that anti-gK sera enhanced HSV-1 infection in the macrophage cell line U937. In addition, passive transfer of anti-gK sera to naive mice 24 h prior to ocular HSV-1 challenge also increased viral replication. These results were consistent with ADE of HSV-1 by sera to gK. This suggests that the severely exacerbated corneal disease seen following HSV-1 ocular challenge of gK vaccinated mice is a result of ADE. The ability of gK sera to cause harmful ADE may impact HSV-1 vaccine development.

Both CD4+ and CD8+ T cells are involved in protection against HSV-1 induced corneal scarring

AIM

To determine the relative impact of CD4+ T cells and CD8+ T cells in protecting mice against ocular HSV-1 challenge.

METHODS

CD4+ T cell knockout mice (CD4-/- mice), CD8+ T cell knockout mice (CD8-/- mice), and mice depleted for CD4+ or CD8+ T cells by antibody (CD4+ depleted and CD8+ depleted mice), were examined for their ability to withstand HSV-1 ocular challenge. The parental mice for both knockout mice were C57BL/6J.

RESULTS

These results suggest that: (1) both CD4+ deficient mice (CD4-/- and CD4+ depleted mice) and CD8+ deficient mice (CD8-/-, and CD8+ depleted mice) developed significantly more corneal scarring than their C57BL/6J parental strain; (2) the duration of virus clearance from the eyes of the CD4+ deficient mice was 4 days longer than that of the CD8+ deficient mice; and (3) the severity of corneal scarring in the CD4+ deficient mice was approximately twice that of the CD8+ deficient mice.

CONCLUSIONS

It was reported here that: (1) CD4+ and CD8+ T cells were both involved in protection against lethal ocular HSV-1 infection; and (2) CD4+ and CD8+ T cells were both involved in protection against HSV-1 induced corneal scarring.

Virus-induced neuronal apoptosis blocked by the herpes simplex virus latency-associated transcript

Latent infections with periodic reactivation are a common outcome after acute infection with many viruses. The latency-associated transcript (LAT) gene is required for wild-type reactivation of herpes simplex virus (HSV). However, the underlying mechanisms remain unclear. In rabbit trigeminal ganglia, extensive apoptosis occurred with LAT(-) virus but not with LAT(+) viruses. In addition, a plasmid expressing LAT blocked apoptosis in cultured cells. Thus, LAT promotes neuronal survival after HSV-1 infection by reducing apoptosis.

The latency-associated transcript gene enhances establishment of herpes simplex virus type 1 latency in rabbits

The latency-associated transcript (LAT) gene the only herpes simplex virus type 1 (HSV-1) gene abundantly transcribed during neuronal latency, is essential for efficient in vivo reactivation. Whether LAT increases reactivation by a direct effect on the reactivation process or whether it does so by increasing the establishment of latency, thereby making more latently infected neurons available for reactivation, is unclear. In mice, LAT-negative mutants appear to establish latency in fewer neurons than does wild-type HSV-1. However, this has not been confirmed in the rabbit, and the role of LAT in the establishment of latency remains controversial. To pursue this question, we inserted the gene for the enhanced green fluorescent protein (EGFP) under control of the LAT promoter in a LAT-negative virus (DeltaLAT-EGFP) and in a LAT-positive virus (LAT-EGFP). Sixty days after ocular infection, trigeminal ganglia (TG) were removed from the latently infected rabbits, sectioned, and examined by fluorescence microscopy. EGFP was detected in significantly more LAT-EGFP-infected neurons than DeltaLAT-EGFP-infected neurons (4.9% versus 2%, P < 0.0001). The percentages of EGFP-positive neurons per TG ranged from 0 to 4.6 for DeltaLAT-EGFP and from 2.5 to 11.1 for LAT-EGFP (P = 0.003). Thus, LAT appeared to increase neuronal latency in rabbit TG by an average of two- to threefold. These results suggest that LAT enhances the establishment of latency in rabbits and that this may be one of the mechanisms by which LAT enhances spontaneous reactivation. These results do not rule out additional LAT functions that may be involved in maintenance of latency and/or reactivation from latency.

The role of natural killer cells in protection of mice against death and corneal scarring following ocular HSV-1 infection

C57BL/6 mice depleted of NK (natural killer) cells with anti-asialo-GM1 antibody were more susceptible to lethal HSV-1 ocular challenge (12% survival) than control C57BL/6 mice (100% survival), CD4+ depleted mice (100% survival), CD8+ depleted mice (80% survival), or macrophage depleted mice (85% survival). NK depletion also resulted in significantly higher levels of HSV-1 induced corneal scarring than was seen with any of the other groups. C57BL/6 mice depleted of NK cells with PK136 (anti-NK1.1 antibody which is more specific for NK cells than is anti-asialo-GM1 antibody) were also more susceptible to HSV-1 ocular challenge than T cell or macrophage depleted mice. Vaccination completely protected NK depleted mice against death and corneal scarring. In contrast to C57BL/6 mice, in BALB/c mice, NK depletion had no effect on survival or corneal scarring following ocular HSV-1 challenge. Experiments with IFN-gamma knockout mice (IFN-gamma(o/o) mice) suggested that IFN-gamma played a minor role in protection of naïve mice against death following HSV-1 challenge. However, IFN-gamma did not appear to be an important factor in protection against HSV-1 induced eye disease. Thus, protection against HSV-1 induced corneal scarring in naive mice appeared to be due to a non-INF-gamma NK function. Our results therefore suggest that NK cells were very important in protecting naive C57BL/6 mice but not vaccinated C57BL/6 mice against corneal scarring and death following ocular HSV-1 challenge.

Perforin pathway is essential for protection of mice against lethal ocular HSV-1 challenge but not corneal scarring

Perforin (cytolysin; pore-forming protein) is expressed in both CD8(+) cytotoxic T lymphocytes (CTLs) and natural killer (NK) cells, and is a major factor responsible for the cytolytic activities of these cells. Both CD8(+) T-cells and NK cells are important in eliminating cells infected with certain viruses. We examined the role of perforin in a mouse model of HSV-1 infection using perforin-deficient mice. Naïve perforin knockout (perforin(0/0)) mice were more susceptible to lethal HSV-1 ocular challenge (60% survival), than naïve parental C57BL/6 (100% survival). In contrast, both C57BL/6 and perforin(0/0) mice had similar levels of HSV-1 induced corneal scarring. Vaccination of perforin(0/0) mice induced a significantly higher HSV-1 neutralizing antibody titer than vaccination of C57BL/6 mice, and the mice were completely protected against lethal ocular challenge. These results suggest that in naïve mice ocularly challenged with HSV-1, the perforin pathway was involved in protection against death, but not in protection against corneal scarring.

Either a CD4(+)or CD8(+)T cell function is sufficient for clearance of infectious virus from trigeminal ganglia and establishment of herpes simplex virus type 1 latency in mice

Following ocular infection of normal mice, herpes simplex virus type 1 (HSV-1) establishes a latent infection in the trigeminal ganglia (TG) with the complete absence of detectable infectious virus. In this study, the role of CD4(+)and CD8(+)T cell dependent immune responses is examined in relation to clearing infectious virus from the TG following HSV-1 ocular challenge. Nude mice, which lack T cells, and MHC(o/o)mice, which lack both MHC class I and MHC class II, were challenged ocularly with wild-type HSV-1. Over 70% of the TG from mice surviving the infection contained infectious virus, indicative of a chronic infection in these TG, rather than a latent infection. No infectious virus was detected in TGs from infected C57BL/6 parental mice. Ocular challenge of CD4(o/o)A(beta(o/o, CD8(o/o)or beta(2)m(o/o)mice resulted in latent rather than chronic infection. Similarly, when C57BL/6 mice were depleted for CD4(+)or CD8(+)T cells from 4 days before ocular challenge to 26 days after ocular challenge, no free virus was detected in TGs of challenged mice. In contrast, when mice were depleted of both their CD4(+)and CD8(+)T cells, over 90% of TGs were positive for free virus, suggesting that the lack of virus clearance was due to the combined lack of both CD4(+)T cells and CD8(+)T cells (i.e. in the presence of either CD4(+)T cells or CD8(+)T cells alone all of the infectious virus was cleared and latency was established).))

Herpes simplex virus type 1 serum neutralizing antibody titers increase during latency in rabbits latently infected with latency-associated transcript (LAT)-positive but not LAT-negative viruses

The herpes simplex virus type 1 (HSV-1) latency-associated transcript (LAT) gene is essential for efficient spontaneous reactivation in the rabbit ocular model of HSV-1 latency and reactivation. LAT is also the only viral gene abundantly expressed during latency. Rabbits were ocularly infected with the wild-type HSV-1 strain McKrae or the McKrae-derived LAT null mutant dLAT2903. Serum neutralizing antibody titers were determined at various times during acute and latent infection. The neutralizing antibody titers induced by both viruses increased and were similar throughout the first 45 days after infection (P > 0.05). However, by day 59 postinfection (approximately 31 to 45 days after latency had been established), the neutralizing antibody titers induced by wild-type virus and dLAT2903 diverged significantly (P = 0.0005). The dLAT2903-induced neutralizing antibody titers decreased, while the wild-type virus-induced neutralizing antibody titers continued to increase. A rescuant of dLAT2903, in which spontaneous reactivation was fully restored, induced wild-type neutralizing antibody levels on day 59 postinfection. A second LAT mutant with impaired spontaneous reactivation had neutralizing antibody levels comparable to those of dLAT2903. In contrast to the results obtained in rabbits, in mice, neutralizing antibody titers did not increase over time during latency with any of the viruses. Since LAT is expressed in both rabbits and mice during latency, the difference in neutralizing antibody titers between these animals is unlikely to be due to expression of a LAT protein during latency. In contrast, LAT-positive (LAT(+)), but not LAT-negative (LAT(-)), viruses undergo efficient spontaneous reactivation in rabbits, while neither LAT(+) nor LAT(-) viruses undergo efficient spontaneous reactivation in mice. Thus, the increase in neutralizing antibody titers in rabbits latently infected with LAT(+) viruses may have been due to continued restimulation of the immune system by spontaneously reactivating virus.

Specific and nonspecific immune stimulation of MHC-II-deficient mice results in chronic HSV-1 infection of the trigeminal ganglia following ocular challenge

Ocular herpes simplex virus type 1 (HSV-1) infection of MHC-II-deficient mice (AO/Obeta mice) or their parental C57BL/6J wild-type mice resulted in the establishment of typical HSV-1 latent infections in the trigeminal ganglia (TG) of the surviving mice by day 28 postinfection. Latency was characterized by the complete absence of infectious virus in TG extracts, the ability to recover latent virus only following prolonged tissue culture cultivation of explanted TG, and the presence of HSV-1 DNA in TG extracts. When mice were vaccinated prior to ocular HSV-1 challenge, latency appeared unaltered in the C57BL/6J wild-type mice. However, in AO/Obeta mice, clearance of virus from the TG appeared to be seriously impaired, resulting in a chronic productive infection, rather than a latent infection. Infectious virus was readily detected in TG extracts of vaccinated AO/Obeta mice until at least 63 days postinfection. Glycoprotein B mRNA was also readily detected, confirming continued viral transcription. These chronic infections occurred regardless of whether the AO/Obeta mice were vaccinated with HSV-1-specific antigens (i.e., live HSV-1 strain KOS, recombinantly expressed HSV-1 glycoprotein D plus Freund's adjuvant, or a mixture of seven recombinantly expressed HSV-1 glycoproteins plus adjuvant) or non-HSV-1-specific antigens (i.e., tissue culture medium plus 5% fetal bovine serum, the expression vector plus adjuvant, or adjuvant alone). Passive transfer of HSV-1 neutralizing antibody to vaccinated AO/Obeta mice between days 0 and 28 post-ocular challenge did not clear infectious virus from the TG. Passive transfer of anti-HSV-1 antibody or purified naive mouse serum to unvaccinated AO/Obeta mice on days 3 or 6 post-HSV-1 ocular challenge also resulted in chronic, rather than latent, infection of the TG. Passive transfer of naive sera from B-cell-deficient mice or injection of keyhole limpet hemocyanin or purified IgG, but not PBS or dextran, 3 days after HSV-1 challenge also resulted in chronic infection of the TG.

Vaccination with different HSV-1 glycoproteins induces different patterns of ocular cytokine responses following HSV-1 challenge of vaccinated mice

We previously reported that vaccination of BALB/c mice with different baculovirus expressed HSV-1 glycoproteins induced varying degrees of protection against HSV-1 ocular challenge, ranging from complete protection to no protection, to exacerbation of eye disease. To correlate specific local immune responses with protection and exacerbation of corneal scarring, we examined immune cell infiltrates in the cornea after ocular HSV-1 challenge of vaccinated mice. Mice were vaccinated with gD, which completely protects against corneal scarring, gG, which produces no protection against corneal scarring, or gK, which exacerbates corneal scarring. Cryostat sections of cornea were taken at different times after challenge and examined for infiltrating cells containing IL-2, IL-4, IFN-gamma, IL-6, or TNF-alpha. No corneal infiltrates were seen before challenge or 1 day after ocular challenge in any groups. By days 3-7, many cells containing IL-4 and IFN-gamma, but few cells containing IL-2, had infiltrated into the corneas of gG or mock vaccinated mice. At the same times, many cells containing IL-2, but few cells containing IL-4 or IFN-gamma, were seen in the corneas of gD vaccinated mice. In contrast, the corneas of mice vaccinated with gK contained large amounts of IL-2, IFN-gamma, and IL-4. Our results suggest that: (1) corneas from gD vaccinated mice had no corneal disease and developed a response highly biased toward IL-2 responses; (2) corneas from gG or mock vaccinated eyes had significant corneal disease and developed a mostly IL-4 and IFN-gamma cytokine response; and (3) corneas from gK vaccinated mice had exacerbated corneal disease and developed strong IL-2, IL-4 and IFN-gamma cytokine responses.

The role of interleukin (IL)-2 and IL-4 in herpes simplex virus type 1 ocular replication and eye disease

To assess the relative effect of interleukin (IL)-2- and IL-4-dependent immune responses on herpes simplex virus (HSV)-1 infection, naive, vaccinated, and mock-vaccinated IL-20/0 and IL-40/0 knockout mice were challenged ocularly with HSV-1. Naive IL-20/0 mice were significantly more susceptible to lethal infection than IL-40/0 or parental BALB/c mice. Vaccinated, IL-20/0, IL-40/0, and BALB/c mice induced similar neutralizing antibody titers and were completely protected against HSV-1-induced death and corneal scarring. Vaccinated and mock-vaccinated IL-20/0 mice had significantly higher HSV-1 titers in their eyes than BALB/c mice, while vaccinated and mock-vaccinated IL-40/0 mice had significantly lower HSV-1 titers in their eyes than BALB/c mice. Recombinant (r) IL-2 treatment of the IL-20/0 mice significantly reduced ocular HSV-1 replications, but rIL-4 treatment of IL-40/0 mice significantly increased ocular HSV-1 replications. Th1 (IL-2) cytokine responses may help protect mice against ocular HSV-1 challenge and reduce ocular HSV-1 replication.

A herpes simplex virus type 1 latency-associated transcript mutant with increased virulence and reduced spontaneous reactivation

The herpes simplex virus type 1 (HSV-1) latency-associated transcript (LAT) gene is essential for efficient spontaneous reactivation of HSV-1 from latency. We previously reported that insertion of the LAT promoter and just the first 1.5 kb of the 8. 3-kb LAT gene into an ectopic location in the virus restored wild-type spontaneous reactivation to a LAT null mutant. This mutant, LAT3.3A (previously designated LAT1.5a), thus showed that the expression of just the first 1.5 kb of LAT is sufficient for wild-type spontaneous reactivation. We also showed that in the context of the entire LAT gene, deletion of LAT nucleotides 76 to 447 (LAT mutant dLAT371) had no effect on spontaneous reactivation or virulence. We report here on a LAT mutant designated LAT2.9A. This mutant is similar to LAT3.3A, except that the ectopic LAT insert contains the same 371-nucleotide deletion found in dLAT371. We found that LAT2.9A had a significantly reduced rate of spontaneous reactivation compared to marker-rescued and wild-type viruses. This was unexpected, since the combined results of dLAT371 and LAT3.3A predicted that spontaneous reactivation of LAT2.9A would be wild type. We also found that LAT2.9A was more virulent than wild-type or marker-rescued viruses after ocular infection of rabbits. This was unexpected, since LAT null mutants and LAT3.3A have wild-type virulence. These results suggest for the first time (i) that regions past the first 1.5 kb of LAT can compensate for deletions in the first 1.5kb of LAT and may therefore play a role in LAT dependent spontaneous reactivation and (ii) that regions of LAT affect viral virulence.

Identical 371-base-pair deletion mutations in the LAT genes of herpes simplex virus type 1 McKrae and 17syn+ result in different in vivo reactivation phenotypes

The herpes simplex virus type 1 (HSV-1) LAT gene is the only viral gene abundantly transcribed during latency. LAT null mutants created with strains McKrae and 17syn+ are impaired for both in vivo spontaneous and in vivo-induced reactivation. Thus, LAT is essential for efficient in vivo-induced and spontaneous reactivation. Different investigators have studied two LAT mutants containing a StyI-StyI region deletion corresponding to LAT nucleotides 76 to 447. One mutant, dLAT371 (parent strain, McKrae), had parental high frequencies of spontaneous reactivation. In vivo-induced reactivation was not examined. The other mutant, 17DeltaSty (parent strain, 17syn+), had parental frequencies of in vitro reactivation following cocultivation of explanted ganglia but reduced frequencies of in vivo-induced reactivation. Spontaneous reactivation frequency was not reported for 17DeltaSty. These combined results suggested the possibility that in vivo spontaneous reactivation and in vivo-induced reactivation may map to different regions within the LAT domain. We now report that dLAT371 has in vivo-induced reactivation frequencies of the parent and that 17DeltaSty has reduced frequencies of in vivo spontaneous reactivation. Thus, dLAT371 demonstrated the parental phenotype for both in vivo spontaneous and -induced reactivation while the apparently identical 17DeltaSty was impaired for both in vivo spontaneous and -induced reactivation. These results suggest that one or more differences between the genetic backgrounds of McKrae and 17syn+ result in different in vivo reactivation phenotypes of otherwise identical deletion mutations and that McKrae may have compensating sequences sufficient to overcome the loss of the StyI-StyI region of the LAT transcript.

Therapeutic periocular vaccination with a subunit vaccine induces higher levels of herpes simplex virus-specific tear secretory immunoglobulin A than systemic vaccination and provides protection against recurrent spontaneous ocular shedding of virus in latently infected rabbits

Rabbits latently infected with herpes simplex virus type 1 (HSV-1) were vaccinated either periocularly or systemically with a subunit vaccine (gB2 + gD2) plus adjuvant or adjuvant alone. Tear films were collected daily to measure recurrent infectious HSV-1 shedding. After systemic vaccination, the latently infected rabbits were not protected against recurrent ocular viral shedding (HSV-1-positive tear film cultures/total cultures) compared with either the systemic or periocular adjuvant controls (systemic vaccination = 49 of 972, 5.0%; systemic control = 46 of 972, 4.7%; periocular control = 43 of 930, 4.6%; P > 0.8). In contrast, latently infected rabbits vaccinated periocularly with the same vaccine had significantly reduced recurrent shedding (20 of 1026, 2.0%) compared with controls (P < 0.001) or systemic vaccination (P = 0.0002). Thus, recurrent HSV-1 shedding was significantly reduced by therapeutic local periocular subunit vaccination but not by therapeutic systemic subunit vaccination. Neutralizing antibody titers in the serum of systemically and ocularly vaccinated rabbits was similar. In contrast, HSV-specific tear secretory immunoglobulin A was significantly higher in the ocularly vaccinated group (P < 0.01). These results strongly suggest that in the rabbit, and presumably in humans, the local ocular (mucosal) immune response is much more important than the systemic immune response for therapeutic protection against recurrent ocular HSV-1. Thus development of a therapeutic vaccine against recurrent ocular HSV-1 should be directed at enhancing the local ocular (mucosal) immune response.

The role of neutralizing antibody and T-helper subtypes in protection and pathogenesis of vaccinated mice following ocular HSV-1 challenge

In order to determine the possible correlation of specific immune responses with protection against mortality and ocular disease following ocular herpes simplex virus type 1 (HSV-1) challenge, BALB/c mice were vaccinated with different doses and regimens of baculovirus-expressed gD. Neutralizing antibody, virus titres in the eyes, corneal scarring, and survival were measured. In addition, infiltration into the cornea of CD4+ T cells and cells containing the lymphokines interleukin-2 (IL-2), IL-4, IL-6 and tumour necrosis factor-alpha (TNF-alpha) were monitored on days 3, 7, 10, 14 and 21 post-challenge by immunocytochemistry. The vaccination regimens used induced varying degrees of immune responses and protection upon ocular challenge with HSV-1. Our results suggest that neutralizing antibody was the most important immune response in protecting mice against lethal ocular challenge and corneal scarring. TNF-alpha and IL-2 were not crucial in terms of survival and corneal scarring, since gD1 (one vaccination with 1 microg of gD) and gD0.1 (one vaccination with 0.1 microg of gD), both of which provided high levels of protection, showed no TNF-alpha or IL-2 expression. However, TNF-alpha and IL-2 were crucial in terms of virus clearance from the eyes, since gD3 (three vaccinations with 1 microg of gD), which had less virus in their eyes, had high numbers of TNF-alpha and IL-2 infiltrates. Finally, mock-vaccinated mice were not protected from death and corneal disease following HSV-1 challenge. Eyes of mock-vaccinated mice had little or no TNF-alpha or IL-2 responses and the strongest IL-4 and IL-6 responses.

Local periocular vaccination protects against eye disease more effectively than systemic vaccination following primary ocular herpes simplex virus infection in rabbits

Vaccination of experimental animals can provide efficient protection against ocular herpes simplex virus type 1 (HSV-1) challenge. Although it is suspected that local immune responses are important in protection against ocular HSV-1 infection, no definitive studies have been done to determine if local ocular vaccination would produce more efficacious protection against HSV-1 ocular challenge than systemic vaccination. To address this question, we vaccinated groups of rabbits either systemically or periocularly with recombinant HSV-2 glycoproteins B (gB2) and D (gD2) in MF59 emulsion or with live KOS (a nonneurovirulent strain of HSV-1). Three weeks after the final vaccination, all eyes were challenged with McKrae (a virulent, eye disease-producing strain of HSV-1). Systemic vaccination with either HSV-1 KOS or gB2/gD2 in MF59 did not provide significant protection against any of the four eye disease parameters measured (conjunctivitis, iritis, epithelial keratitis, and corneal clouding). In contrast, periocular vaccination with gB2/gD2 in MF59 provided significant protection against conjunctivitis and iritis, while ocular vaccination with live HSV-1 KOS provided significant protection against all four parameters. Thus, local ocular vaccination provided better protection than systemic vaccination against eye disease following ocular HSV-1 infection. Since local vaccination should produce a stronger local immune response than systemic vaccination, these results suggest that the local ocular immune response is very important in protecting against eye disease due to primary HSV-1 infection. Thus, for clinical protection against primary HSV-1-induced corneal disease, a local ocular vaccine may prove more effective than systemic vaccination.

A therapeutic vaccine that reduces recurrent herpes simplex virus type 1 corneal disease

PURPOSE

To investigate the therapeutic efficacy of periocular vaccination with herpes simplex virus (HSV) recombinant glycoprotein D from HSV-1 (gD1) or HSV-2 (gD2) in decreasing HSV-induced recurrent dendritic keratitis and HSV-induced recurrent ocular shedding in rabbits latently infected with HSV-1.

METHODS

Rabbits latently infected with HSV-1 were vaccinated periocularly (by subconjunctival injection) with gD1 and adjuvant, gD2 and adjuvant, or adjuvant alone. Eyes were examined daily for 49 days for recurrent herpetic keratitis and for recurrent infectious HSV-1 shedding.

RESULTS

In both vaccinated groups, a significantly decreased number of eyes exhibited recurrences of herpetic keratitis compared with recurrences in adjuvant-treated control eyes (gD1 group, 27/1372, [2%]; gD2 group, 24/1274, [2%]; and control, 54/1274 [4%]; P < 0.005). Eyes in the gD1-vaccinated group (44/1308 [3.4%]; P = 0.01), but not those in the gD2-vaccinated group (71/1274 [5.6%]; P = 0.93), had significantly decreased viral shedding (positive cultures compared with total cultures) compared with eyes in the adjuvant-treated control group (69 of 1275 [5.4%]).

CONCLUSIONS

Recurrent HSV-1 corneal disease was significantly reduced by therapeutic local periocular vaccination. The vaccine may be more efficacious against HSV-1-induced recurrent corneal disease than against recurrent HSV-1 ocular shedding. Its efficacy against corneal disease appeared to be longer lasting than its efficacy against recurrent spontaneous shedding. The heterotypic gD2 vaccine was as efficacious as the homotypic gD1 vaccine against recurrent corneal disease, whereas the homotypic vaccine was much more efficacious than the heterotypic vaccine against recurrent HSV-1 shedding. This is the first report in any animal model of a successful therapeutic vaccine against recurrent HSV-1-induced corneal disease. These results support the concept that development of a therapeutic vaccine for ocular HSV-1 recurrence in humans may be possible.

MHC-II but not MHC-I responses are required for vaccine-induced protection against ocular challenge with HSV-1

PURPOSE

To determine the importance of major histocompatibility complex (MHC) class-I versus MHC class-II immune responses in protecting naive versus vaccinated mice against an ocular HSV-1 challenge.

METHODS

Class-II deficient A beta o/o (CD4-CD8+ T cells) knockout mice, which are effectively CD4+ T cells-negative, and class-I deficient beta(2)mo/o (CD4+CD8- T cells) knockout mice, which are effectively CD8+ T cells negative, were either vaccinated or mock-vaccinated and examined for their ability to withstand HSV-1 ocular challenge.

RESULTS

Unvaccinated A beta o/o and beta(2)mo/o mice were both more susceptible to lethal ocular HSV-1 infection than the parental wild type C57BL/6J mice, indicating that both MHC-I and MHC-II were required for optimal protection of naive mice against ocular HSV-1 challenge. Vaccinated beta(2)mo/o mice produced significant neutralizing antibody titers, and following ocular challenge, these mice were completely protected against death and corneal scarring. In contrast, vaccinated A beta o/o mice developed no neutralizing antibody titers and vaccination did not provide these mice with any protection against death or corneal scarring. Passive transfer of anti-HSV-1 antibody into A beta o/o mice up to 6 days post ocular challenge resulted in complete protection against death and corneal scarring.

CONCLUSIONS

Passive antibody transfer, but not vaccination, protected A beta o/o mice against ocular challenge. In contrast, vaccination completely protected beta(2)mo/o mice. These results suggest for a vaccine to provide optimal protection against ocular HSV-1 challenge in this system, it is not only sufficient, but it is also required, that the vaccine induce an effective neutralizing antibody response.

The importance of MHC-I and MHC-II responses in vaccine efficacy against lethal herpes simplex virus type 1 challenge

To investigate the importance of major histocompatability complex (MHC) class I- and MHC class II-dependent immune responses in herpes simplex virus-1 (HSV-1) vaccine efficacy, groups of beta 2% (MHC I-) and Ab% (MHC II-) mice were inoculated with various vaccines, and then challenged intraperitoneally with HSV-1. Following vaccination with either live avirulent HSV-1, expressed HSV-1 glycoprotein D (gD), or a mixture of seven expressed HSV-1 glycoproteins (7gPs), Ab% (MHC-II-) mice developed no enzyme-linked immunosorbent assay (ELISA) or neutralizing antibody titres. In contrast, significant ELISA and neutralizing antibody titres were induced in beta 2m% (MHC-I-) mice by all three vaccines. The neutralizing antibody titres were similar for all three vaccines, but were only approximately 1/4 to 1/3 of that developed in C57BL/6 (parental) mice vaccinated with the same antigens. All three vaccines protected 100% of the wild-type C57BL/6 mice against lethal challenge with 2 x 10(7) plaque-forming units (PFU) of HSV-1. The live virus vaccine and the 7gPs vaccine also protected 80% of the beta 2m% mice against the same lethal HSV-1 challenge dose. In contrast, in Abo/o mice, none of the vaccines provided significant protection against the same lethal challenge dose of HSV-1. However, at a lower challenge dose of 2 x 10(6) PFU, all three vaccines protected 70-80% of the vaccinated Ab% mice (compared to only 10% survival in mock vaccinated controls). Thus, vaccination provided some protection against lethal HSV-1 challenge in both beta 2m% and Ab% mice; however, the protection was less than that seen in the parental C57BL/6 mice. In addition, Ab% mice were less well protected by vaccination than were beta 2m% mice. Our results suggest that (1) both MHC-I and MHC-II are involved in vaccine efficacy against HSV-1 challenge; (2) both types of responses must be present for maximum vaccine efficacy: and (3) the MHC-II-dependent immune response appeared to be more important than the MHC-I-dependent immune response for vaccine efficacy against HSV-I challenge.

Nonneutralizing antibody against the glycoprotein K of herpes simplex virus type-1 exacerbates herpes simplex virus type-1-induced corneal scarring in various virus-mouse strain combinations

PURPOSE

To determine whether the exacerbation of herpes simplex virus type-1 (HSV-1) induced corneal scarring that the authors reported previously in HSV-1 glycoprotein K (gK) vaccinated BALB/c mice challenged with HSV-1 strain McKrae was a general phenomenon independent of virus and mouse strains. To determine the gK-induced immune response leading to exacerbation of HSV-1-induced corneal scarring.

METHODS

BALB/c or C57BL/6 mice were vaccinated with gK, ocularly challenged with HSV-1 strain KOS or McKrae, and the relative amount of corneal scarring determined 28 days after challenge. The T cells, total serum, or purified immunoglobulin G (IgG) isolated from gK-vaccinated mice was transferred individually to naive mice, and the affects on corneal scarring after HSV-1 challenge were determined.

RESULTS

The KOS challenge of gK-vaccinated BALB/c mice resulted in significant corneal scarring (P = 0.0003), despite the fact that KOS normally produces no corneal scarring. McKrae challenge of gK-vaccinated C57BL/6 mice resulted in significant corneal scarring (P < 0.0001), despite the fact that C57BL/6 mice are normally refractory to HSV-1-induced corneal scarring. Passive transfer of total anti-gK mouse sera or purified anti-gK mouse IgG, but not adoptive transfer of total anti-gK T-cells to naive mice, resulted in exacerbation of corneal scarring after HSV-1 challenge (P < 0.0001). Mice defective for T-cell-dependent antibody production were not susceptible to exacerbation of HSV-1-induced corneal scarring by gK vaccination (P < 0.0001).

CONCLUSIONS

The ability of gK vaccination to exacerbate HSV-1-induced corneal scarring was not mouse strain or HSV-1 strain specific. The gK-induced exacerbation of corneal scarring was related to anti-gK IgG. How anti-gK IgG exacerbated HSV-1 induced corneal scarring remains to be determined.

The UL3 open reading frame of herpes simplex virus type 1 codes for a phosphoprotein

Based on sequence analysis, the protein encoded by the UL3 open reading frame (ORF) of herpes simplex virus type 1 (HSV-1) was predicted to contain an N glycosylation site and to be a glycoprotein. To determine if this prediction was correct, we cloned and expressed the DNA encoding the complete sequence of the UL3 ORF in a baculovirus expression system. Western blotting was done using polyclonal antibody raised against synthetic UL3 peptides. Two major baculovirus-UL3 expressed protein bands with apparent molecular weights of 30 kDa and 31 kDa, and two minor protein bands with apparent molecular weights of 29 kDa and 33 kDa were detected. None of the expressed UL3 protein species were susceptible to tunicamycin treatment, suggesting that they were not N-linked glycosylated. Cell fractionation studies indicated that the UL3 protein was localized in the cytoplasmic and nuclear portion of the cells, rather than the cell membrane, again suggesting a lack of glycosylation. In contrast, the baculovirus expressed UL3 protein was phosphorylated as judged by 32Pi-labeling. Immunoprecipitation followed by SDS-PAGE demonstrated a single 32Pi-labeled UL3 related band with an apparent molecular weight of 33 kDa, indicating that the UL3 protein was a phosphoprotein. Antibodies produced in mice vaccinated with baculovirus-UL3 protein reacted with two UL3 related HSV-1 bands on Western blots. These protein bands had apparent molecular weights of 27 and 33 kDa and presumably represent the unphosphorylated and phosphorylated forms of UL3.

Vaccination with herpes simplex virus type 1 glycoprotein K impairs clearance of virus from the trigeminal ganglia resulting in chronic infection

Following primary ocular infection, HSV-1 establishes a latent infection in the trigeminal ganglia with the complete absence of detectable infectious virus. Recently, we showed that vaccination of BALB/cJ with HSV-1 glycoprotein K (gK), but not other HSV-1 glycoproteins, significantly exacerbated the severity of HSV-1-induced ocular disease and herpetic dermatitis (H. Ghiasi et al. J. Virol. 68, 2347-2354, 1994). We now report that prior vaccination with gK blocked viral clearance from trigeminal ganglia until at least Day 56 postinfection, resulting in a chronic infection. The significance of this novel finding with respect to potential harmful complications associated with the immune response to gK is discussed.

High-dose ocular infection with a herpes simplex virus type 1 ICP34.5 deletion mutant produces no corneal disease or neurovirulence yet results in wild-type levels of spontaneous reactivation

We report here that in the rabbit ocular model of herpes simplex virus type 1 (HSV-1) latency, spontaneous reactivation of the HSV-1 ICP34.5 deletion mutant d34.5 increased significantly in response to increasing infectious doses. At the highest infectious dose of d34.5, the spontaneous reactivation rate was indistinguishable from that of wild-type virus (average spontaneous reactivation rates for d34.5, 0.3 to 1.4% at 2 x 10(5) PFU per eye, 3.4% at 2 x 10(6) PFU per eye, and 6.3 to 11.5% at 1 x 10(8) PFU per eye; average spontaneous reactivation rates for marker-rescued virus, 7.7 to 19.6% at 2 x 10(5) PFU per eye). The percentage of latency-associated transcript (LAT) RNA-positive neurons in sections from trigeminal ganglia (TG) of rabbits latently infected with d34.5 demonstrated a similar dose-response effect as estimated by in situ hybridization (0.05% LAT RNA-positive neurons at 2 x 10(5) PFU per eye and 0.1% LAT RNA-positive neurons at 1 x 10(8) PFU per eye; P = 0.002). In contrast, even at the highest infectious dose (1 x 10(8) PFU per eye), d34.5 was less virulent (23 of 23 survivors) than the normal infectious dose (2 x 10(5) PFU per eye) of marker-rescued virus (14 of 27 survivors; P < 0.0001). In addition, at 1 x 10(8) PFU per eye, d34.5 produced virtually no corneal disease, compared with the production of severe corneal disease by 2 x 10(5) PFU of marker-rescued virus per eye (P < 0.0001). Thus, at increasing infectious doses of d34.5, both spontaneous reactivation and the percentage of neurons expressing LAT appeared to increase, without a corresponding increase in virulence. These results strongly suggest that (i) the phenotypes of neurovirulence and spontaneous reactivation are separable, (ii) the phenotypes of corneal disease and spontaneous reactivation are separable, and (iii) the decreased rate of spontaneous reactivation previously reported for d34.5 (G. C. Perng, R. L. Thompson, N. M. Sawtell, W. E. Taylor, S. M. Slanina, H. Ghiasi, R. Kaiwar, A. B. Nesburn, and S. L. Wechsler, J. Virol. 69:3033-3041, 1995) is at least partially due to a reduced rate of establishing latency.

A 371-nucleotide region between the herpes simplex virus type 1 (HSV-1) LAT promoter and the 2-kilobase LAT is not essential for efficient spontaneous reactivation of latent HSV-1

The herpes simplex virus type 1 (HSV-1) latency-associated transcript (LAT) gene is essential for efficient spontaneous reactivation of HSV-1 from latency. However, neither the mechanism by which LAT carries out this function nor the region of LAT responsible for this function in known. LAT is transcribed as an unstable 8.3-kb RNA that gives rise to a very stable 2-kb LAT RNA that is readily detected in latently infected sensory neurons. We show here that 371 of the 662 nucleotides located between the start of LAT transcription and the 5' end of the 2-kb LAT RNA do not appear to be essential for wild-type levels of spontaneous reactivation in the rabbit ocular model of HSV-1 latency. We deleted LAT nucleotides 76 to 447 from both copies of the LAT gene (one in each viral long repeat) to produce the mutant dLAT371. Rabbits were ocularly infected with dLAT371, and spontaneous reactivation was measured in comparison with the marker-rescued virus dLAT371R. Both dLAT371 and dLAT371R had spontaneous reactivation rates of approximately 13 to 14%. This was consistent with the parental McKrae wild-type virus (11.7%; P = 0.49) and significantly higher than the LAT transcription-negative mutant dLAT2903 (2.4%; P < 0.0001). Southern analysis confirmed that the spontaneously reactivated dLAT371 virus retained the deletion in both copies of LAT. Therefore, it appeared that the function of LAT involved in efficient spontaneous reactivation mapped outside the 371-nucleotide region deleted from the LAT gene of dLAT371.

The spontaneous reactivation function of the herpes simplex virus type 1 LAT gene resides completely within the first 1.5 kilobases of the 8.3-kilobase primary transcript

The herpes simplex virus type 1 (HSV-1) latency-associated transcript (LAT) gene is essential for efficient spontaneous reactivation of HSV-1 from latency. We report here that although the LAT gene is 8.3 kb in length, the first 1.5 kb of the LAT gene alone is sufficient for wild-type levels of spontaneous reactivation. We began with a LAT deletion mutant of HSV-1 strain McKrae in which the LAT promoter and the first 1.6 kb of the 5' end of the LAT gene had been deleted from both copies of LAT (one in each viral long repeat). As we previously reported, this mutant (dLAT2903) was significantly impaired for spontaneous reactivation (G. C. Perng, E. C. Dunkel, P. A. Geary, S. M. Slanina, H. Ghiasi, R. Kaiwar, A. B. Nesburn, and S. L. Wechsler, J. Virol. 68:8045-8055, 1994). We then inserted the LAT promoter and the first 1.5 kb of the LAT gene into a location in the unique long region of dLAT2903 far removed from the normal location of LAT in the long repeats. This resulted in a virus (LAT15a) whose capacity for transcribing LAT RNA was limited to the first 1.5 kb of the 8.3-kb LAT primary transcript. Rabbits were ocularly infected with this mutant, and spontaneous reactivation was measured in comparison to those of the original LAT-negative mutant and its marker-rescued (wild-type) virus, dLAT2903R. LAT15a had an in vivo spontaneous reactivation rate of 12%, compared with a rate of 11% for the marker-rescued virus and 0% for the LAT-negative virus. Southern analysis confirmed that the spontaneously reactivated LAT15a virus retained the original deletions in both copies of LAT and the 1.5-kb LAT insertion in the unique long region. Thus, insertion of the first 1.5 kb of LAT (and its promoter) at a site distant from the normal LAT location appeared to completely restore in vivo spontaneous reactivation to wild-type levels, despite the remaining inability of the original LAT genes to transcribe any LAT RNA. The function of LAT involved in efficient spontaneous reactivation therefore appeared to map completely within the first 1.5 kb of the LAT gene.

Vaccination with a cocktail of seven recombinantly expressed HSV-1 glycoproteins protects against ocular HSV-1 challenge more efficiently than vaccination with any individual glycoprotein

Our previous studies have shown that of seven HSV-1 glycoproteins (gB, gC, gD, gE, gG, gH and gI) individually expressed in baculovirus, vaccination with gD provides the best protection against HSV-1 challenge. To establish whether vaccination with a mixture of these seven expressed glycoproteins would provide better protection against HSV-1 challenge than vaccination with gD alone, we determined the level of protection afforded by vaccination with a cocktail of the seven expressed glycoproteins. The amount of each of the seven expressed glycoproteins in the mixture was equivalent to one-seventh the amount of gD used in the gD alone vaccination. Thus, the total amount of glycoprotein was the same for the cocktail and gD alone vaccine. For neutralizing antibody titer, delayed-type hypersensitivity (DTH), and survival following lethal challenge, no difference was observed between mice vaccinated with all seven glycoproteins and those vaccinated with gD. However, for other criteria, vaccination with all seven glycoproteins appeared to provide better protection than vaccination with gD. Following ocular challenge, virus was not detected at any time in the tears of mice vaccinated with all seven glycoproteins. In contrast, virus was detected in the tears of gD vaccinated mice for up to 3 days post challenge. Mock vaccinated mice had virus in their tears for as long as 10 days. Mice vaccinated with all seven glycoproteins had no eye disease, while gD vaccinated mice had a significant amount of blepharitis. Finally, compared to gD vaccinated mice, the mice vaccinated with all seven glycoproteins were more efficiently protected against the establishment of HSV-1 latency following ocular infection. Our results therefore suggest that while for some protective criteria there was no significant difference between vaccination with gD or seven glycoproteins, vaccination with seven glycoproteins was more efficient in protecting challenged mice against some forms of eye disease, the duration of infection and the establishment of latency.

The region of the herpes simplex virus type 1 LAT gene that is colinear with the ICP34.5 gene is not involved in spontaneous reactivation

The goal of this report was to determine if the region of the LAT gene that is colinear with ICP34.5 (kb 6.2 to 7.1 of LAT) is involved in spontaneous reactivation of herpes simplex virus type 1. We inserted one copy of the ICP34.5 gene into the unique long region of a herpes simplex virus type 1 (strain McKrae) mutant lacking both copies of ICP34.5 (one in each viral long repeat) and the corresponding 917-nucleotide colinear portion of LAT (kb 6.2 to 7.1). Rabbits were ocularly infected with this mutant, and spontaneous reactivation relative to that for the wild-type virus and the original mutant was measured. As we previously reported, the original ICP34.5-deleted virus (d34.5) was significantly impaired for spontaneous reactivation and virulence (G. C. Perng, R. L. Thompson, N. M. Sawtell, W. E. Taylor, S. M. Slanina, H. Ghiasi, R. Kaiwar, A. B. Nesburn, and S. L. Wechsler, J. Virol. 69:3033-3041, 1995). In contrast, we report here that restoration of one copy of ICP34.5 at a distant location completely restored the wild-type level of in vivo spontaneous reactivation, despite retention of the deletion in LAT (spontaneous reactivation rate = 0.3 to 1.4% for the ICP34.5 deletion mutant, 7.7 to 19.6% for the wild type, and 9 to 16.1% for virus with one copy of ICP34.5). Thus, the 917-nucleotide region of LAT from kb 6.2 to 7.1 was not involved in the LAT function required for wild-type spontaneous reactivation. We also found that restoration of a single ICP34.5 gene in a novel location did not restore wild-type virulence (rabbit death rate = 0% [0 of 15] for the original ICP34.5 deletion mutant, 8% [2 of 24] for the single-copy IPC34.5 virus, and 52% [14 of 27] for wild-type virus; P < 0.001 for one versus two copies of ICP34.5). It is likely that either two gene doses of ICP34.5 or its location in the long repeat is essential for full functionality of ICP34.5's virulence function. Furthermore, the ability of the single-copy ICP34.5 virus to reactivate at wild-type levels despite being significantly less virulent than wild-type virus separates the spontaneous reactivation phenotype from the virulence phenotype.

Vaccination of mice with herpes simplex virus type 1 glycoprotein D DNA produces low levels of protection against lethal HSV-1 challenge

The herpes simplex virus type 1 (HSV-1) glycoprotein D (gD) gene was inserted into vectors pSVL or pRc/CMV under control of the SV40 late promoter or the human cytomegalovirus major immediate-early promoter, respectively. Intramuscular injection of mice with these gD-containing plasmids appeared to induce low levels of serum anti-gD antibody, as judged by the appearance of low levels of anti-HSV-1-neutralizing antibody and anti-gD ELISA responses in the serum of gD-DNA-vaccinated mice. As previously reported in other virus systems, vaccination with vector DNA also induced ELISA and neutralizing antibody titers. However, these titers were lower than those induced by the gD-containing plasmids. The ELISA and neutralization titers induced by the vectors appeared to be non-specific rather than directed at specific HSV-1 proteins, since serum from mice vaccinated with plasmid-gD immunoprecipitated significant amounts of gD from extracts of HSV-1-infected cells, while serum from mice vaccinated with vectors was unable to immunoprecipitate gD or any other obvious HSV-1 proteins. Neither pSVL-gD nor pRc/CMV-gD induced detectable lymphocyte proliferative or CTL responses. Vaccination with pSVL-gD provided a significant (P = 0.04, Fisher's exact test), but low level of protection against lethal challenge with HSV-1. Vaccination with pRc/CMV-gD also appeared to provide a low level of protection against challenge, that was statistically significance at the 10% level (P = 0.054, Fisher's exact test). Reports from numerous laboratories (including ours) have shown that vaccination with recombinantly expressed gD can provide very high levels of protection against HSV-1 lethal challenge. Thus, the results reported here suggest that vaccination with HSV-1 gD-DNA is not yet a useful alternative to a gD subunit vaccine.

Protection against herpes simplex virus-induced eye disease after vaccination with seven individually expressed herpes simplex virus 1 glycoproteins

PURPOSE

To compare the efficacy of each of seven expressed herpes simplex virus 1 (HSV-1) glycoproteins as vaccines to protect against ocular disease after primary ocular HSV-1 infection.

METHODS

Mice were vaccinated three times with equal amounts of each of seven individually expressed HSV-1 glycoproteins (gB, gC, gD, gE, gG, gH, and gI) and then ocularly challenged with McKrae, a corneal disease-producing strain of HSV-1. Viral clearance from the eye, blepharitis, keratitis, and neovascularization were determined at various times after infection.

RESULTS

Mice vaccinated with gD or gB had the best protection against eye disease. Vaccination with gI, gC, or gE produced moderate protection against eye disease. Vaccination with gG produced less protection, and vaccination with gH produced no apparent protection against eye disease.

CONCLUSIONS

These results suggest that when used as vaccines, different HSV-1 glycoproteins provide different levels of protection against HSV-1-induced eye disease. Based on comparison with the authors' previously published results, the ability of each glycoprotein to protect against eye disease correlated with the ability of the glycoprotein to induce high serum neutralizing antibody titers and killer cell activity. Results suggest that the effectiveness of these seven glycoproteins in protecting against eye disease can be ranked as follows: gD > gB > gI > (gC = gE) > gG > gH.

An avirulent ICP34.5 deletion mutant of herpes simplex virus type 1 is capable of in vivo spontaneous reactivation

The herpes simplex virus type 1 (HSV-1) ICP34.5 gene is a neurovirulence gene in mice. In addition, some ICP34.5 mutants have been reported to have a reduced efficiency of induced reactivation as measured by in vitro explantation of latently infected mouse ganglia. However, since spontaneous reactivation is almost nonexistent in mice, nothing has been reported on the effect of ICP34.5 mutants on spontaneous reactivation in vivo. To examine this, we have deleted both copies of the ICP34.5 neurovirulence gene from a strain of HSV-1 (McKrae) that has a high spontaneous reactivation rate in rabbits and used this mutant to infect rabbit eyes. All rabbits infected with the ICP34.5 mutant virus (d34.5) survived, even at challenge doses greater than 4 x 10(7) PFU per eye. In contrast, a 200-fold-lower challenge dose of 2 x 10(5) PFU per eye was lethal for approximately 50% of rabbits infected with either the wild-type McKrae parental virus or a rescued ICP34.5 mutant in which both copies of the ICP34.5 gene were restored. In mice, the 50% lethal dose of the ICP34.5 mutant was over 10(6) PFU, compared with a value of less than 10 PFU for the rescued virus. The ICP34.5 mutant was restricted for replication in rabbit and mouse eyes and mouse trigeminal ganglia in vivo. The spontaneous reactivation rate in rabbits for the mutant was 1.4% as determined by culturing tear films for the presence of reactivated virus. This was more than 10-fold lower than the spontaneous reactivation rate determined for the rescued virus (19.6%) and was highly significant (P < 0.0001, Fisher exact test). Southern analysis confirmed that the reactivated virus retained both copies of the ICP34.5 deletion. Thus, this report demonstrates that (i) the ICP34.5 gene, known to be a neurovirulence gene in mice, is also important for virulence in rabbits and (ii) in vivo spontaneous reactivation of HSV-1 in the rabbit ocular model, although reduced, can occur in the absence of the ICP34.5 gene.

Local expression of tumor necrosis factor alpha and interleukin-2 correlates with protection against corneal scarring after ocular challenge of vaccinated mice with herpes simplex virus type 1

To correlate specific local immune responses with protection from corneal scarring, we examined immune cell infiltrates in the cornea after ocular challenge of vaccinated mice with herpes simplex virus type 1 (HSV-1). This is the first report to examine corneal infiltrates following ocular challenge of a vaccinated mouse rather than following infection of a naive mouse. Mice were vaccinated systemically with vaccines that following ocular challenge with HSV-1 resulted in (i) complete protection against corneal disease (KOS, an avirulent strain of HSV-1); (ii) partial protection, resulting in moderate corneal disease (baculovirus-expressed HSV-1 glycoprotein E [gE]); and (iii) no protection, resulting in severe corneal disease (mock vaccine). Infiltration into the cornea of CD4+ T cells, CD8+ T cells, macrophages, and cells containing various lymphokines was monitored on days 0, 1, 3, 7, and 10 postchallenge by immunocytochemistry of corneal sections. Prior to ocular challenge, no eye disease or corneal infiltrates were detected in any mice. KOS-vaccinated mice developed high HSV-1 neutralizing antibody titers (> 1:640) in serum. After ocular challenge, they were completely protected against death, developed no corneal disease, and had no detectable virus in their tear films at any time examined. In response to the ocular challenge, these mice developed high local levels of infiltrating CD4+ T cells and cells containing interleukin-2 (IL-2), IL-4, IL-6, or tumor necrosis factor alpha (TNF-alpha). In contrast, only low levels of infiltrating CD8+ T cells were found, and gamma interferon (IFN-gamma)-containing cells were not present until day 10. gE-vaccinated mice developed neutralizing antibody titers in serum almost as high as those of the KOS-vaccinated mice (> 1:320). After ocular challenge, they were also completely protected against death. However, the gE-vaccinated mice developed low levels of corneal disease and virus was detected in one-third of their eyes. Compared with KOS-vaccinated mice, the gE-vaccinated mice had a similar pattern of IFN-gamma, but a delay in the appearance of CD4+ T cells, CD8+ T cells, and IL-4-, IL-6-, and TNF-alpha-containing cells. In sharp contrast to those of the KOS-vaccinated mice, no cells containing IL-2 were detected in the eyes of gE-vaccinated mice at any time. Mock-vaccinated mice developed no detectable neutralizing antibody titer and were not protected from lethal HSV-1 challenge.(ABSTRACT TRUNCATED AT 400 WORDS)

The latency-associated transcript gene of herpes simplex virus type 1 (HSV-1) is required for efficient in vivo spontaneous reactivation of HSV-1 from latency

During herpes simplex virus type 1 (HSV-1) neuronal latency, the only viral RNA detected is from the latency-associated transcript (LAT) gene. We have made a LAT deletion mutant of McKrae, an HSV-1 strain with a very high in vivo spontaneous reactivation rate. This mutant (dLAT2903) lacks the LAT promoter and the first 1.6 kb of the 5' end of LAT. dLAT2903 was compared with its parental virus and with a rescued virus containing a restored LAT gene (dLAT2903R). Replication of the LAT mutant in tissue culture, rabbit eyes, and rabbit trigeminal ganglia was similar to that of the rescued and parental viruses. On the basis of semiquantitative PCR analysis of the amount of HSV-1 DNA in trigeminal ganglia, the LAT mutant was unimpaired in its ability to establish latency. In contrast, spontaneous reactivation of dLAT2903 in the rabbit ocular model of HSV-1 latency and reactivation was decreased to approximately 33% of normal. This decrease was highly significant (P < 0.0001) and demonstrates that in an HSV-1 strain with a high spontaneous reactivation rate, deletion of LAT can dramatically decrease in vivo spontaneous reactivation. We also report here that deletion of LAT appeared to eliminate rather than just reduce in vivo induced reactivation.

Expression and characterization of baculovirus expressed herpes simplex virus type 1 glycoprotein L

We have constructed a recombinant baculovirus expressing high levels of the herpes simplex virus type 1 (HSV-1) glycoprotein L (gL) in Sf9 cells. Sf9 cells infected with this recombinant virus synthesized three polypeptides of 26-27 kDa 28 kDa, and 31 kDa. The 28 and 31 kDa species were sensitive to tunicamycin and N-glycosidase F (PNGase F) treatment, suggesting that they were glycosylated. As shown by both indirect immunofluorescence and Western blot analysis, using polyclonal antibodies to synthetic gL peptides indicated that the baculovirus expressed gL was abundant on the surface of baculovirus gL infected Sf9 cells. A small fraction of the 31 kDa polypeptide was secreted into the extracellular medium as judged by Western blot analysis. The secreted form of gL was completely resistant to Endoglycosidase H (Endo-H), while the membrane associated form of gL was only partially resistant to Endo-H treatment, suggesting that the secreted gL represented a subpopulation of the membrane bound gL. Mice vaccinated with baculovirus expressed gL produced serum antibodies that reacted with authentic HSV-1 gL. However, these mice produced no HSV-1 neutralizing antibody (titer < 1:10) and they were not protected from lethal intraperitoneal or lethal ocular challenge with HSV-1. Thus, when used as a vaccine in the mouse model, gL, similar to our findings with HSV-1 gH, but unlike our results with the other 6 HSV-1 glycoproteins that we have expressed in this baculovirus system, did not provide any protection against HSV-1 challenge.

Vaccine therapy for ocular herpes simplex virus (HSV) infection: periocular vaccination reduces spontaneous ocular HSV type 1 shedding in latently infected rabbits

Periocular vaccination of rabbits with preexisting herpes simplex virus type 1 (HSV-1) latent infection with recombinant HSV-2 glycoproteins B and D (gB2 and gD2) plus adjuvant significantly reduced ocular viral shedding. Rabbits were infected in both eyes with HSV-1 strain McKrae. Following HSV-1 infection and the establishment of latency (28 days postinfection), rabbits were given a periocular subconjunctival vaccination three times at 3-week intervals. Beginning 3 weeks after the final vaccination, tear films were collected daily and cultured to detect the presence of HSV-1 and determine the spontaneous HSV-1 ocular shedding rates. Periocular vaccination increased the mean HSV-1 serum neutralizing antibody titer to fivefold above that seen in mock-vaccinated latently infected rabbits. gB enzyme-linked immunosorbent assay (ELISA) antibody titers were increased approximately 8-fold, and gD ELISA antibody titers were increased 60-fold. These increases were all statistically significant (P < 0.0001). In two independent experiments, vaccination reduced the spontaneous shedding rate by approximately 2.5-fold (P < 0.0004). In addition, the percentage of eyes that never shed virus during the 6 week postvaccination test period increased threefold (20% in controls versus 60% in vaccinated animals; P < 0.007). These results show that spontaneous ocular shedding of HSV-1 in latently infected rabbits can be significantly reduced by local periocular vaccination. This is the first report in any animal model of a successful therapeutic vaccine against recurrent HSV-1 ocular shedding. These results support the concept that development of a therapeutic vaccine for ocular HSV-1 recurrence in humans is possible.

Similarities in regulation of the HSV-1 LAT promoter in corneal and neuronal cells

PURPOSE

To address the possibility of neuronal-like herpes simplex virus type 1 (HSV-1) latency in the cornea by determining if regulation of the HSV-1 LAT promoter in stromal keratocytes is similar to LAT promoter regulation in neurons.

METHODS

Transient chloramphenicol acetyltransferase (CAT) assays were used to measure the relative promoter activity of various HSV-1 LAT promoter fragments in primary human corneal cells versus neuronal and nonneuronal cells.

RESULTS

The authors found that the LAT promoter, whose location they previously mapped in neurons using transient CAT assays, functioned in stromal keratocytes using the same assay system and that two regions between -283 and -1932 nucleotides relative (upstream) to the start of LAT transcription slightly increased the LAT promoter activity in stromal keratocytes. They previously showed a similar increase in neuronal cells, and a large decrease in nonneuronal cells. In addition, they found that a neuronal specific enhancer region they previously defined between -162 and -283 nucleotides upstream of the start of LAT transcription also enhanced promoter activity in stromal keratocytes. Using gel-shift assays, they detected a nuclear factor specific to neurons and stromal keratocytes that binds to the LAT promoter and that may be a LAT regulatory factor.

CONCLUSIONS

Recently, it has been suggested that the cornea might serve as an alternative site of latent herpes simplex virus type 1 (HSV-1) infection. However, this remains controversial. The authors' findings suggest that corneal and neuronal cells regulate the LAT promoter similarly and that this regulation differs from that seen in nonneuronal cells. Thus, the possibility of neuronal-like latency in the cornea remains plausible.

Expression of seven herpes simplex virus type 1 glycoproteins (gB, gC, gD, gE, gG, gH, and gI): comparative protection against lethal challenge in mice

We have constructed recombinant baculoviruses individually expressing seven of the herpes simplex virus type 1 (HSV-1) glycoproteins (gB, gC, gD, gE, gG, gH, and gI). Vaccination of mice with gB, gC, gD, gE, or gI resulted in production of high neutralizing antibody titers to HSV-1 and protection against intraperitoneal and ocular challenge with lethal doses of HSV-1. This protection was statistically significant and similar to the protection provided by vaccination with live nonvirulent HSV-1 (90 to 100% survival). In contrast, vaccination with gH produced low neutralizing antibody titers and no protection against lethal HSV-1 challenge. Vaccination with gG produced no significant neutralizing antibody titer and no protection against ocular challenge. However, gG did provide modest, but statistically significant, protection against lethal intraperitoneal challenge (75% protection). Compared with the other glycoproteins, gG and gH were also inefficient in preventing the establishment of latency. Delayed-type hypersensitivity responses to HSV-1 at day 3 were highest in gG-, gH-, and gE-vaccinated mice, while on day 6 mice vaccinated with gC, gE, and gI had the highest delayed-type hypersensitivity responses. All seven glycoproteins produced lymphocyte proliferation responses, with the highest response being seen with gG. The same five glycoproteins (gB, gC, gD, gE, and gI) that induced the highest neutralization titers and protection against lethal challenge also induced some killer cell activity. The results reported here therefore suggest that in the mouse protection against lethal HSV-1 challenge and the establishment of latency correlate best with high preexisting neutralizing antibody titers, although there may also be a correlation with killer cell activity.

Characterization of baculovirus-expressed herpes simplex virus type 1 glycoprotein K

The DNA region encoding the complete herpes simplex virus type 1 (HSV-1) glycoprotein K (gK) was inserted into a baculovirus transfer vector, and recombinant viruses expressing gK were isolated. Four gK-related recombinant baculovirus-expressed peptides of 29, 35, 38, and 40 kDa were detected with polyclonal antibody to gK. The 35-, 38-, and 40-kDa species were susceptible to tunicamycin treatment, suggesting that they were glycosylated. The 38- and 40-kDa species corresponded to partially glycosylated precursor gK (pgK) and mature gK, respectively. The 29-kDa peptide probably represented a cleaved, unglycosylated peptide. The 35-kDa peptide probably represented a cleaved, glycosylated peptide that may be a precursor to pgK. Indirect immunofluorescence with polyclonal antibody to gK peptides indicated that the recombinant baculovirus-expressed gK was abundant on the surface of the insect cells in which it was expressed. Mice vaccinated with the baculovirus-expressed gK produced very low levels (< 1:10) of HSV-1 neutralizing antibody. Nonetheless, these mice were partially protected from lethal challenge with HSV-1 (75% survival). This protection was significant (P = 0.02). Despite some protection against death, gK-vaccinated mice showed no protection against the establishment of latency. Surprisingly, gK-vaccinated mice that were challenged ocularly with a stromal disease-producing strain of HSV-1 had significantly higher levels of ocular disease (herpes stromal keratitis) than did mock-vaccinated mice. In summary, this is the first report to show that vaccination with HSV-1 gK can provide protection against lethal HSV-1 challenge and that vaccination with an HSV-1 glycoprotein can significantly increase the severity of HSV-1-induced ocular disease.

An improved method for cloning portions of the repeat regions of herpes simplex virus type 1

The use of a low copy number plasmid to enhance greatly the ability to clone herpes simplex virus type 1 (HSV-1) DNA is described. Certain regions of the HSV-1 DNA have been extremely difficult to clone. Particular difficulties have often been encountered in the long and short viral repeats. Attempts to clone certain HSV-1 sequences using common plasmids produced plasmids containing inserts of unusual size and/or plasmids smaller than the original plasmid. The reason for these cloning difficulties is unclear. However, the difficulties may be related to the high overall GC content of the HSV-1 genome, the even higher GC content of the repeats, small direct and inverted repeats within the viral repeats, or uncharacterized secondary DNA structure. We show that the use of the low copy number plasmid pEV-vrf3 greatly enhanced our ability to clone and subclone 'difficult' HSV-1 restriction fragments, including restriction fragments that we were unable to clone using other plasmids.

Baculovirus-expressed glycoprotein G of herpes simplex virus type 1 partially protects vaccinated mice against lethal HSV-1 challenge

The DNA sequence encoding the complete HSV-1 glycoprotein G (gG) was inserted into a baculovirus transfer vector and recombinant viruses expressing gG were isolated. Three gG-related recombinant baculovirus expressed peptides of 37, 42, and 44 kDa were detected by Western blotting using monoclonal antibody to gG. The 42- and 44-kDa species were susceptible to tunicamycin, Endoglycosidase H (Endo-H), and N-glycosidase F (PNGase F) treatments, suggesting that they were glycosylated. Although only very low levels (approximately 1:10) of HSV-1-neutralizing antibody were produced in mice vaccinated with the baculovirus gG, these mice were partially protected from lethal challenge with HSV-1 (75-78% survival) and this level of protection was highly significant (P = 0.002). This is the first report to show that vaccination with HSV-1 gG can provide mice with any level of protection against lethal HSV-1 challenge.

Baculovirus expressed herpes simplex virus type 1 glycoprotein C protects mice from lethal HSV-1 infection

A recombinant baculovirus (vAc-gC1) was constructed that expresses the glycoprotein C (gC) gene of herpes simplex virus type 1 (HSV-1). When Sf9 cells were infected with this recombinant, a protein that was smaller in size than authentic HSV-1 gC was detected by Western blotting using anti-gC polyclonal antibody. The recombinant gC was susceptible to tunicamycin, partially resistant to Endo-H, and was found on the membrane of Sf9 cells. Antibodies raised in mice to recombinant gC reacted with gC from HSV-1 infected cells and neutralized the infectivity of HSV-1 in vitro. Immunized mice were protected from lethal challenge with HSV-1.

Baculovirus-expressed glycoprotein E (gE) of herpes simplex virus type-1 (HSV-1) protects mice against lethal intraperitoneal and lethal ocular HSV-1 challenge

We have constructed a recombinant baculovirus expressing high levels of the herpes simplex virus type 1 (HSV-1) glycoprotein E (gE) in Sf9 cells. The expressed gE migrated on gels as a double band with apparent molecular weights of 68 and 70 kDa. The recombinant gE was glycosylated based on its susceptibility to tunicamycin treatment and was transported to the membrane of Sf9 cells based on indirect immunofluorescence. Mice vaccinated with gE developed high serum titers of HSV-1-neutralizing antibodies based on plaque reduction assays. gE vaccination also induced a strong delayed type hypersensitivity (DTH) response to HSV-1. In addition, mice vaccinated with the recombinant gE were protected from both intraperitoneal and ocular lethal HSV-1 challenge. To our knowledge, this is the first report in which vaccination with gE was shown to induce high neutralizing antibody titers, a DTH response, or protection against lethal HSV-1 challenge.

Expression of herpes simplex virus type 1 glycoprotein I in baculovirus: preliminary biochemical characterization and protection studies

We have constructed a recombinant baculovirus expressing the herpes simplex virus type 1 (HSV-1) glycoprotein I (gI). Sf9 cells infected with this recombinant virus synthesized gI-related polypeptides with apparent molecular sizes of 52 and 56 kDa. The recombinant gI appeared to be glycosylated, since it was susceptible to both tunicamycin and endoglycosidase H, and the expressed gI was transported to the surface of infected cells as judged by indirect immunofluorescence. Antibodies to the recombinant gI raised in mice neutralized HSV-1 infectivity. Finally, we show here for the first time that vaccination with gI can protect mice against HSV-1 challenge.