Role of Lyt-1 positive immune T cells in recovery from herpes simplex virus infection in mice

Presence of CD80 and Absence of LAT in Modulating Cellular Infiltration and HSV-1 Latency

CD80 is the best-known costimulatory molecule for effective T cell functions. Many different reports have summarized the role of CD80 in HSV-1 and its functions in maintaining adaptive immunity, which is the main player in causing herpes stromal keratitis (HSK). To determine the effects of absence or overexpression of CD80 in HSV-1 infection, we infected CD80-/- and WT mice with a recombinant HSV-1 expressing murine CD80 (HSV-CD80) in place of the latency associated transcript (LAT). Parental dLAT2903 virus lacking LAT was used as a control. After infection, critical components of infection like virus replication, eye disease, early cellular infiltrates into the corneas and trigeminal ganglia (TG), latency-reactivation in the infected mice were determined. Our findings reveal that the absence of CD80 in the CD80-/- mice infected with both viruses did not affect the viral titers in the mice eyes or eye disease, but it played a significant role in critical components of HSV-induced immunopathology. The WT mice infected with dLAT2903 virus had significantly higher levels of latency compared with the CD80-/- mice infected with dLAT2903 virus, while levels of latency as determined by gB DNA expression were similar between the WT and CD80-/- mice infected with HSV-CD80 virus. In contrast to the differences in the levels of latency between the infected groups, the absence of CD80 expression in the CD80-/- mice or its overexpression by HSV-CD80 virus did not have any effect on the time of reactivation. Furthermore, the absence of CD80 expression contributed to more inflammation in the CD80-/--infected mice. Overall, this study suggests that in the absence of CD80, inflammation increases, latency is reduced, but reactivation is not affected. Altogether, our study suggests that reduced latency correlated with reduced levels of inflammatory molecules and blocking or reducing expression of CD80 could be used to mitigate the immune responses, therefore controlling HSV-induced infection.

Role of TH17 Responses in Increasing Herpetic Keratitis in the Eyes of Mice Infected with HSV-1

Purpose

T_H17 cells play an important role in host defense and autoimmunity yet very little is known about the role of IL17 in herpes simplex virus (HSV)-1 infectivity. To better understand the relationship between IL17 and HSV-1 infection, we assessed the relative impact of IL17A-deficiency and deficiency of its receptors on HSV-1 responses in vivo.

Methods

We generated IL17RA^−/− and IL17RA^−/−RC^−/− mice in-house and infected them along with IL17A^−/− and IL17RC^−/− mice in the eyes with 2 × 10⁵ PFU/eye of wild type (WT) HSV-1 strain McKrae. WT C57BL/6 mice were used as control. Virus replication in the eye, survival, corneal scarring (CS), angiogenesis, levels of latency-reactivation, and levels of CD8 and exhaustion markers (PD1, TIM3, LAG3, CTLA4, CD244, and CD39) in the trigeminal ganglia (TG) of infected mice were determined on day 28 postinfection.

Results

No significant differences in virus replication in the eye, survival, latency, reactivation, and exhaustion markers were detected among IL17A^−/−, IL17RA^−/−, IL17RC^−/−, IL17RA^−/−RC^−/−, and WT mice. However, mice lacking IL17 had significantly less CS and angiogenesis than WT mice. In addition, angiogenesis levels in the absence of IL17RC and irrespective of the absence of IL17RA were significantly less than in IL17A- or IL17RA-deficient mice.

Conclusions

Our results suggest that the absence of IL17 protects against HSV-1-induced eye disease, but has no role in protecting against virus replication, latency, or reactivation. In addition, our data provide rationale for blocking IL17RC function rather than IL17A or IL17RA function as a key driver of HSV-1-induced eye disease.

Herpes Simplex Virus 1 ICP22 Suppresses CD80 Expression by Murine Dendritic Cells

Herpes simplex virus type 1 (HSV-1) has the ability to delay its clearance from the eye during ocular infection. Here, we show that ocular infection of mice with HSV-1 suppressed expression of the costimulatory molecule CD80 but not CD86 in the cornea. The presence of neutralizing anti-HSV-1 antibodies did not alleviate this suppression. At the cellular level, HSV-1 consistently downregulated the expression of CD80 by dendritic cells (DCs) but not by other antigen-presenting cells. Furthermore, flow cytometric analysis of HSV-1-infected corneal cells during a 7-day period reduced CD80 expression in DCs but not in B cells, macrophages, or monocytes. This suppression was associated with the presence of virus. Similar results were obtained using infected or transfected spleen cells or bone marrow-derived DCs. A combination of roscovitine treatment, transfection with immediate early genes (IE), and infection with a recombinant HSV-1 lacking the ICP22 gene shows the importance of ICP22 in downregulation of the CD80 promoter but not the CD86 promoter in vitro and in vivo At the mechanistic level, we show that the HSV-1 immediate early gene ICP22 binds the CD80 promoter and that this interaction is required for HSV-1-mediated suppression of CD80 expression. Conversely, forced expression of CD80 by ocular infection of mice with a recombinant HSV-1 exacerbated corneal scarring in infected mice. Taken together, these studies identify ICP22-mediated suppression of CD80 expression in dendritic cells as central to delayed clearance of the virus and limitation of the cytopathological response to primary infection in the eye.IMPORTANCE HSV-1-induced eye disease is a major public health problem. Eye disease is associated closely with immune responses to the virus and is exacerbated by delayed clearance of the primary infection. The immune system relies on antigen-presenting cells of the innate immune system to activate the T cell response. We found that HSV-1 utilizes a robust and finely targeted mechanism of local immune evasion. It downregulates the expression of the costimulatory molecule CD80 but not CD86 on resident dendritic cells irrespective of the presence of anti-HSV-1 antibodies. The effect is mediated by direct binding of HSV-1 ICP22, the product of an immediate early gene of HSV-1, to the promoter of CD80. This immune evasion mechanism dampens the host immune response and, thus, reduces eye disease in ocularly infected mice. Therefore, ICP22 may be a novel inhibitor of CD80 that could be used to modulate the immune response.

Role of CD8+ T cells and lymphoid dendritic cells in protection from ocular herpes simplex virus 1 challenge in immunized mice

The development of immunization strategies to protect against ocular infection with herpes simplex virus 1 (HSV-1) must address the issue of the effects of the strategy on the establishment of latency in the trigeminal ganglia (TG). It is the reactivation of this latent virus that can cause recurrent disease and corneal scarring. CD8(+) T cells and dendritic cells (DCs) have been implicated in the establishment and maintenance of latency through several lines of inquiry. The objective of the current study was to use CD8α(-/-) and CD8β(-/-) mice to further evaluate the contributions of CD8(+) T cells and the CD8α(+) and CD8α(-) subpopulations of DCs to the protection afforded against ocular infection by immunization against HSV-1 and their potential to increase latency. Neutralizing antibody titers were similar in immunized CD8α(-/-), CD8β(-/-), and wild-type (WT) mice, as was virus replication in the eye. However, on day 3 postinfection (p.i.), the copy number of HSV-1 glycoprotein B (gB) was higher in the corneas and TG of CD8α(-/-) mice than those of WT mice, whereas on day 5 p.i. it was lower. As would be anticipated, the lack of CD8α(+) or CD8β(+) cells affected the levels of type I and type II interferon transcripts, but the effects were markedly time dependent and tissue specific. The levels of latent virus in the TG, as estimated by measurement of LAT transcripts and in vitro explant reactivation assays, were lower in the immunized, ocularly challenged CD8α(-/-) and WT mice than in their CD8β(-/-) counterparts. Immunization reduced the expression of PD-1, a marker of T-cell exhaustion, in the TG of ocularly challenged mice, and mock-immunized CD8α(-/-) mice had lower levels of PD-1 expression and latency than mock-immunized WT or CD8β(-/-) mice. The expansion of the CD8α(-) subpopulation of DCs through injection of WT mice with granulocyte-macrophage colony-stimulating factor (GM-CSF) DNA reduced the amount of latency and PD-1 expression in the TG of infected mice. In contrast, injection of FMS-like tyrosine kinase 3 ligand (Flt3L) DNA, which expanded both subpopulations, was less effective. Our results suggest that the absence of both CD8α(+) T cells and CD8α(+) DCs does not reduce vaccine efficacy, either directly or indirectly, in challenged mice and that administration of GM-CSF appears to play a beneficial role in reducing latency and T-cell exhaustion. Importance: In the past 2 decades, two large clinical HSV vaccine trials were performed, but both vaccine studies failed to reach their goals. Thus, as an alternative to conventional vaccine studies, we have used a different strategy to manipulate the host immune responses in an effort to induce greater protection against HSV infection. In lieu of the pleiotropic effect of CD8α(+) DCs in HSV-1 latency, in this report, we show that the absence of CD8α(+) T cells and CD8α(+) DCs has no adverse effect on vaccine efficacy. In line with our hypothesis, we found that pushing DC subpopulations from CD8α(+) DCs toward CD8α(-) DCs by injection of GM-CSF reduced the amount of latent virus and T-cell exhaustion in TG. While these studies point to the lack of a role for CD8α(+) T cells in vaccine efficacy, they in turn point to a role for GM-CSF in reducing HSV-1 latency.

Recurrent herpes simplex virus infection in a patient with autoimmune polyendocrinopathy-candidiasis-ectodermal dystrophy associated with L29P and IVS9-1G>C compound heterozygous autoimmune regulator gene mutations

Autoimmune polyendocrinopathy-candidiasis-ectodermal dystrophy (APECED) has characteristic clinical features with organ-specific autoimmune polyendocrine diseases and candidiasis, caused by the mutations of autoimmune regulator (AIRE) gene. Although almost all patients are complicated with mucocutaneous candidiasis, no apparent susceptibility to other infections has yet been reported. We herein report that a patient with APECED suffered from recurrent herpes simplex virus type 1 (HSV-1) infection after severe primary herpetic stomatitis, associated with sequential HSV-1 isolates of the same genomic profile, consistent with endogeneous recurrence. Thus, not only candidiasis but also HSV infection should receive more attention in patients with APECED, with treatment being administered accordingly.

Developments in herpes simplex virus vaccines: old problems and new challenges

Vaccination has remained the best method for preventing virus spread. The herpes simplex virus (HSV) candidate vaccines tested till now were mostly purified subunit vaccines and/or recombinant envelope glycoproteins (such as gB and gD). In many experiments performed in mice, guinea pigs and rabbits, clear-cut protection against acute virus challenge was demonstrated along with the reduction of the extent of latency, when established in the immunized host. The immunotherapeutic effect of herpes vaccines seems less convincing. However, introduction of new adjuvants, which shift the cytokine production of helper T-cells toward stimulation of cytotoxic T-cells (TH1 type cytokine response), reveals a promising development. Mathematical analysis proved that overall prophylactic vaccination of seronegative women, even when eliciting 40-60 % antibody response only, would reduce the frequency of genital herpes within the vaccinated population. Even when partially effective, immunotherapeutic vaccination might represent a suitable alternative of chronic chemotherapy in recurrent labial and genital herpes.

Disruption of virion host shutoff activity improves the immunogenicity and protective capacity of a replication-incompetent herpes simplex virus type 1 vaccine strain

The virion host shutoff (vhs) protein encoded by herpes simplex virus type 1 (HSV-1) destabilizes both viral and host mRNAs. An HSV-1 strain with a mutation in vhs is attenuated in virulence and induces immune responses in mice that are protective against corneal infection with virulent HSV-1, but it has the capacity to establish latency. Similarly, a replication-incompetent HSV-1 strain with a mutation in ICP8 elicits an immune response protective against corneal challenge, but it may be limited in viral antigen production. We hypothesized therefore that inactivation of vhs in an ICP8(-) virus would yield a replication-incompetent mutant with enhanced immunogenicity and protective capacity. In this study, a vhs(-)/ICP8(-) HSV-1 mutant was engineered. BALB/c mice were immunized with incremental doses of the vhs(-)/ICP8(-) double mutant or vhs(-) or ICP8(-) single mutants, or the mice were mock immunized, and protective immunity against corneal challenge with virulent HSV-1 was assessed. Mice immunized with the vhs(-)/ICP8(-) mutant showed prechallenge serum immunoglobulin G titers comparable to those immunized with replication-competent vhs(-) virus and exceed those of mice immunized with the ICP8(-) single mutant. Following corneal challenge, the degrees of protection against ocular disease, weight loss, encephalitis, and establishment of latency were similar for vhs(-)/ICP8(-) and vhs(-) virus-vaccinated mice. Moreover, the double deleted vhs(-)/ICP8(-) virus protected mice better in all respects than the single deleted ICP8(-) mutant virus. The data indicate that inactivation of vhs in a replication-incompetent virus significantly enhances its protective efficacy while retaining its safety for potential human vaccination. Possible mechanisms of enhanced immunogenicity are discussed.

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.

Efficacy of kakkon-to, a traditional herb medicine, in herpes simplex virus type 1 infection in mice

Kakkon-to is one of the representative traditional herb medicines (Kampo formulae) and has been used historically for the treatment of infectious diseases in China and Japan. The efficacy of this preparation was characterised using a cutaneous herpes simplex virus type 1 (HSV-1) infection in mice as a model for human viral infection. Kakkon-to at a dose corresponding to human use reduced significantly the mortality of HSV-1-infected mice and localised skin lesions. Delayed type hypersensitivity (DTH) response to HSV-1 antigen was significantly stronger in treated mice than in untreated mice. However, no histopathological difference was noted in the skin lesions between treated and untreated mice except for the size of the lesions. Kakkon-to did not inhibit the growth of HSV-1 in vitro. Natural killer cell activity, natural cytotoxic killer cell activity, and the population of T-cell subsets in spleen cells of infected mice were not affected by the drug. Kakkon-to did not augment interferon induction and anti-HSV-1 antibody production, nor increased cytokine levels such as interleukin-1 alpha, interleukin-2, interferon-gamma, and tumour necrosis factor-alpha in sera of infected mice. Thus, Kakkon-to induced strong DTH to HSV-1 in infected mice, which may have caused localisation of skin lesions and reduction in the mortality of treated mice.

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.

Interference with major histocompatibility complex class II-restricted antigen presentation in the brain by herpes simplex virus type 1: a possible mechanism of evasion of the immune response

Host survival of herpes simplex virus type 1 (HSV-1) infection depends on the establishment of latent infections in both peripheral and central nervous systems. Strains of HSV-1 that are successful in escaping the immune response produce a lethal infection. We now report a possible mechanism of immune response evasion used by HSV-1. After intraocular inoculation of mice, HSV-1 strain F established a latent infection in the brain, whereas strain KOS did not. The immune response to HSV-1 infection (strains KOS and F) in the brain was characterized by induction of major histocompatibility complex class II expression and recruitment of CD4+ and CD8+ cells to highly restricted sites of intracerebral viral infection. Major histocompatibility complex class II antigen expression was primarily intracellular in strain KOS infection centers and at the cell surface in strain F infection centers. We propose that major histocompatibility complex class II-restricted viral-antigen presentation to T cells is interrupted during strain KOS infections, thereby allowing KOS infection to evade T-cell-mediated events that would normally protect the host from a lethal infection. Immunocompromised mice (athymic or irradiate mice) could not survive strain F infections; however, latent F infections were established in irradiated mice reconstituted with naive lymph node and spleen cells. These data suggest that class II-restricted presentation of viral antigens is required for the control of HSV-1 infections in the nervous system.

Anti-glycoprotein D monoclonal antibody protects against herpes simplex virus type 1-induced diseases in mice functionally depleted of selected T-cell subsets or asialo GM1+ cells

Passive transfer of a monoclonal antibody (MAb) specific for glycoprotein D (gD) is highly effective in preventing the development of herpes simplex virus type 1-induced stromal keratitis. In the present study, we investigated whether animals which had been functionally depleted of T-cell subsets or asialo GM1+ cells would continue to be responsive to MAb therapy. BALB/c mice were depleted of CD4+, CD8+, or asialo GM1+ cells by treatment with anti-L3T4, anti-Lyt 2.2, or anti-asialo GM1 antibodies, respectively. Functional depletion of CD4+ cells was documented by the loss of delayed-type hypersensitivity responsiveness, while CD8+ cell depletion was accompanied by abrogation of cytotoxic lymphocyte activity. Anti-asialo GM1 treatment led to the loss of natural killer cell lytic activity. Mice depleted of the desired cell population and infected on the scarified cornea with herpes simplex virus type 1 uniformly developed necrotizing stromal keratitis by 3 weeks postinfection. A single inoculation of anti-gD MAb (55 micrograms) given intraperitoneally 24 h postinfection strongly protected hosts depleted of CD4+ cells against stromal keratitis. Likewise, antibody treatment in CD8+ or asialo GM1+ cell-depleted hosts was as therapeutically effective as that seen in non-cell-depleted mice. We also observed that in cell-depleted mice, the virus spread into the central nervous system and caused encephalitis. The CD4+ cell-depleted mice were the most severely affected, as 100% developed fatal disease. Anti-gD MAb treatment successfully protected all (32 of 32) CD4+-, CD8+-, or asialo GM1(+)-depleted hosts against encephalitis. We therefore conclude that antibody-mediated prevention of stromal keratitis and encephalitis does not require the obligatory participation of CD4+, CD8+, or asialo GM1+ cells. However, when mice were simultaneously depleted of both CD4+ and CD8+ T-cell subsets, antibody treatment could not prevent fatal encephalitis. Thus, antibody can compensate for the functional loss of one but not two T-lymphocyte subpopulations.

Protection of mice from herpes simplex virus-induced retinitis by in vitro-activated immune cells

A form of acute retinal necrosis occurred in the contralateral eyes of susceptible mice 1 week after each received a uniocular injection of live herpes simplex virus type 1 (HSV-1) in the anterior chamber. Although these mice did not develop systemic delayed hypersensitivity to virus antigens, their sera contained virus-specific antibodies at the time contralateral retinitis occurred. These findings suggest that systemic immunity might not be able to protect against contralateral retinitis. To explore this possibility further, we examined lymph nodes and spleens of intraocularly infected mice to determine whether their lymphoid tissues contained primed HSV-1-specific cytotoxic T cells. Virus-specific cytotoxic T cells were readily identified in these mice. We wondered why successful immune priming did not confer protection against HSV-1 retinitis. We examined this issue by evaluating the capacity of in vitro-generated, HSV-1-specific effector T cells to prevent retinitis by infusing these cells by various routes and at various times into mice that received an intracameral injection of HSV-1. The results revealed that virus-specific effector cells could prevent contralateral retinitis if injected intravenously or into the anterior chamber of the contralateral eye at the same time that virus was injected into one eye. However, the effector cells failed to prevent retinitis if they were injected into the same eye that received HSV-1 or if their intravenous administration was delayed until 24 h after the HSV-1 injection into the eye. We concluded that immune T cells can protect against contralateral retinal necrosis caused by uniocular injection of HSV-1 into the anterior chamber but only if they are administered during the first 24 h after virus infection. We propose that a retinitis-inducing process is set in motion during this early time interval postinfection. Once the process has been initiated and established, it is no longer susceptible to immune intervention. It would appear that mice that are susceptible to contralateral retinitis fail to mobilize a protective response quickly enough to ward off the establishment of the retinitis-inducing process and its disastrous eventuality.

Infiltration of immune T cells in the brain of mice with herpes simplex virus-induced encephalitis

Herpes simplex virus (HSV) infection of mice can induce viral encephalitis. Using two-fluorochrome immunofluorescence, our present study shows that though there is extensive myelin loss and necrosis in the brain stem of mice with HSV encephalitis, only some oligodendrocytes, astrocytes and microglial cells are infected. T cells that express CD4 or CD8 and a large number of CD4+, F4/80+ macrophages are present in perivascular infiltrates close to and in contact with HSV-infected cells in areas of massive myelin loss. These findings suggest that the resultant infiltration of immune cells into the brain during HSV-1 infection may cause as much damage as the virus itself.

Immunogenicity of herpes simplex virus glycoprotein gB-1-related protein produced in yeast

A protein related to glycoprotein B of herpes simplex virus type 1 (HSV-1) produced in yeast (ygB-1) was purified with an immunoadsorbent. The molecular weight of the purified ygB-1 as determined by sodium dodecyl sulphate polyacrylamide gel electrophoresis was 96,000. Mice injected twice with ygB-1 adsorbed to alum developed ELISA antibody to ygB-1, neutralizing antibody to HSV-1 and a lymphoproliferative response to ygB-1 and HSV-1. The immunized mice were protected against intraperitoneal and corneal challenge with HSV-1. Latent infection in the trigeminal ganglia after corneal challenge was also inhibited by immunization with ygB-1. Guinea-pigs pigs immunized with ygB-1 adsorbed to alum also developed ELISA antibody to to ygB-1 and neutralizing antibody to both types of HSV. After the second dose, strong lymphoproliferative responses were seen upon stimulation with HSV-2. Animals were protected against intravaginal challenge with HSV type 2.

Immunohistochemical evaluation of murine HSV-1 keratouveitis

The intraocular inflammatory reaction in a murine model of herpes simplex keratouveitis was studied using immunohistochemical techniques. 5 x 10(5) PFU of HSV-1 (Stewart strain) was applied to the abraded cornea of BALB/c mice. The subsequent development of keratouveitis was documented by sequential examination, conventional histology and immunohistochemical staining of frozen sections with the following monoclonal antibodies: Thy-1, Lyt-1, Lyt-2, Ia, Mac-1 and Lyb-8.2. At one week (in the early stage) there was moderate central corneal edema with inflammatory cell infiltration, consisting of a predominance of polymorphonuclear leukocytes, with the appearance of helper/inducer T-cells(Th/i). At two weeks (in the middle stage), a geographic corneal ulcer developed and the majority of inflammatory cells were still polymorphonuclear leukocytes. However, there was a further increase in the Th/i cell population, with the first appearance of B-cells. At three weeks (in the late stage), a dense stromal corneal scar was observed and there was a decrease in the inflammatory cell population, with the predominant cell being the B-cell. Throughout the evolution of HSV-1 keratouveitis, a mild inflammatory reaction was observed in the uvea. However, the number of inflammatory cells present was too small to allow more definitive characterization. Patchy Ia staining which is noted in the normal choroid increased markedly throughout the keratouveitis.

Role of epidermal Langerhans cells in resistance to herpes simplex virus infection

To investigate the role of epidermal Langerhans cells (LC) in resistance to herpes simplex virus (HSV) infection, nonadherent spleen cells taken from BALB/c mice immunized with HSV were cultured with syngeneic epidermal cells (EC) and ultraviolet light-inactivated HSV antigen. After five days of culture, T cell-dependent proliferative response was determined by 3H-thymidine incorporation. Treatment of EC with anti-Iad monoclonal antibody plus complement before cultivation prevented this proliferation, which suggested that LC induced stimulation of immune T cells. When these stimulated spleen cells were transferred to intracutaneously infected nude mice, the virus titer in the skin was reduced markedly and the formation of zosteriform skin lesions was completely inhibited. On the other hand, transfer of unstimulated cells, which were cultured with HSV antigen only or with HSV antigen and EC treated with anti-Iad monoclonal antibody plus complement, resulted in delayed viral clearance and development of the lesions. These results indicate that LC are of importance as accessory cells in the control of cutaneous HSV infection. Furthermore, Lyt 1+ T cells in the stimulated population were shown to have greater protective activity than Lyt 2+ T cells.

Genetic studies on murine susceptibility to herpes simplex keratitis

We studied the influence of lgh-linked genes on the development of keratopathy after corneal inoculation with herpes simplex virus (HSV). Using congenic strains of mice, we found that the lgh-1 gene locus, or genes closely linked to it, influence the clinical expression of HSV infection. Mice with the lgh-1e or lgh-1d allotype routinely developed severe keratopathy after HSV corneal inoculation, whereas congenic strains with lgh-1a or lgh-1b allotype were less susceptible. Cell-mediated immune responses to HSV also differed between susceptible and resistant murine strains. We interpret our results to imply a genetic influence on cell-mediated, acquired immune responses to HSV infection.

Previous immunization of mice with herpes simplex virus type-1 strain MP protects against secondary corneal infection

Herpes simplex virus (HSV)-induced ocular disease is occurring in epidemic proportions throughout the world, and is the number one cause of unilateral corneal blindness in all developed countries. We have found, in a mouse model of herpes simplex keratitis (HSK), that products encoded by the Igh-1 locus on chromosome 12 exert a profound influence on the immune/inflammatory response in the cornea after HSV inoculation in the cornea. Thus, mice with Igh-1c or Igh-1d phenotype routinely develop extreme keratopathy and loss of corneal clarity after HSV encounter in the eye, while congenic strains expressing other Igh-1 phenotypes develop substantially less keratopathy. We examined the effect of previous subcutaneous immunization with the mutant, less virulent, MP strain of HSV on the development of keratitis and encephalitis after secondary corneal inoculation with strains MP, mP, F, and KOS. A/J mice (Igh-1c), 5-6 weeks old, were injected sc with live HSV-1 strain MP. Controls were injected with culture media without virus. Three weeks later both immunized and control nonimmunized animals were challenged in the cornea with HSV-1, strains MP, mP, F, and KOS. The animals were clinically scored for keratitis and encephalitis at regular intervals for 21 days following corneal challenge. None of the immunized animals challenged in the cornea with strain MP, 5 X 10(4) plaque-forming units (PFU), developed clinical signs of encephalitis compared to 86% of unimmunized controls. Of the immunized animals challenged in the cornea with strain MP, 5 X 10(4) PFU, only 18% developed a mild keratitis, while 96% of unimmunized controls developed severe keratitis. Mice immunized subcutaneously with MP and subsequently challenged corneally with other HSV-1 strains (mP, F, or KOS) were also protected from development of severe keratopathy.

Clonal analysis of T cell responses to herpes simplex virus: a HSV-specific, non cytolytic T cell clone displays specific helper activity for T cell response in vitro

A HSV-specific, Lyt 1+2- T cell clone (D7.1) was established by repetitive in vitro restimulation of in vivo HSV-1 primed draining lymph node cells with UV-inactivated homologous virus. Earlier work had shown that this clone could provide specific helper activity for HSV-1 primed B cells for antibody production in vivo. In this paper, further functional analysis has demonstrated that this clone and its subclones could also help unprimed T cells in the generation of effector DTH T cells in vitro. The helper activity was found to be antigen-specific and cell dose-dependent. In addition, this helper T cell clone showed little, if any, natural killer-like activity and was non-cytolytic towards both HSV-infected and uninfected syngeneic targets. However, they could exert potent cytotoxic activity towards P815 and EL-4 tumour targets in the presence of lectins.

Human T-lymphocyte response in vitro to synthetic peptides of herpes simplex virus glycoprotein D

Immunization of mice with a synthetic peptide that corresponds to a murine antibody-defined immunodominant domain of herpes simplex virus (HSV) glycoprotein D (gD) induced neutralizing antibodies against HSV types 1 and 2 and protected animals against a lethal challenge with HSV type 2 (Dietzschold, B., Eisenberg, R., Ponce de Leon, M., Golub, E., Hudecz, F., Varicchio, A. & Cohen, G. (1984) J. Virol. 52, 431-435). We report here that human peripheral blood T cells from HSV-seropositive and -seronegative adult donors are activated by this synthetic peptide in vitro. Interleukin-2-dependent T-cell lines established from these cultures respond specifically to peptides containing residues 1-23 of HSV gD and to a panel of overlapping peptides within this domain. The T-cell proliferative response was maximal when the majority of interleukin-2-propagated T cells were of the helper phenotype and the peptides were at least 16 amino acids long. Peptides of 8 or 12 amino acids from the carboxyl terminus were nonstimulatory. Peptide-activated T-cell lines from sero-negative donors less than 11 years old could be established in vitro, but most cells were of the suppressor/cytotoxic phenotype and demonstrated no antigen-specificity when tested with the panel of synthetic peptides.

Production of lymphokines and interferon by immune cells involved in recovery of mice from herpes simplex virus type 2 hepatitis

Adoptive transfer of spleen cells from mice 4 days after infection with herpes simplex virus type 2 (HSV-2) reduced the virus titer in the liver of recipient mice infected 24 h before transfer. Macrophage chemotactic factor (CF) and macrophage migration inhibition factor (MIF) were produced by day 3 of infection in spleen cell cultures stimulated with HSV-2, but not with control antigen, i.e. 1 day before the cells are active in adoptive transfer. Interferon was produced in cultures established throughout the infection but not in normal spleen cells. From days 1 to 5 of infection interferon was produced irrespective of in vitro restimulation, although the highest amounts were always produced after stimulation with the specific antigen. Spleen cells from mice infected for 6 days produced interferon only when stimulated with HSV-2. The cells from 6-day-immune mice active in adoptive transfer and CF and MIF production were found to be Thy 1+, Ig- and Lyt2-. Both Thy 1+ and plastic adherent cells were necessary for interferon production, whereas Ig+ and Lyt2+ cells did not produce interferon. The interferon was acid stable and neutralized by antiserum against alpha/beta-interferon and thus has the characteristics of alpha-interferon. The data indicate that a delayed type hypersensitivity reaction with lymphokine-induced macrophage recruitment into infectious foci may be a central feature of the recovery process in HSV-2-induced hepatitis. A possible role of interferon produced by the accumulated cells needs further investigation.

Zosteriform spread of herpes simplex virus as a model of recrudescence and its use to investigate the role of immune cells in prevention of recurrent disease

During the development of a zosteriform rash, which occurs after flank inoculation of BALB/c mice with herpes simplex virus, clinically normal skin becomes infected via nerve endings. This is analogous to the final step in the development of a recrudescent lesion, which may occur after reactivation of latent virus. Therefore, the zosteriform reaction has potential as a model with which to study the modification of such a recrudescent infection by immune processes. Using an adoptive transfer system, we confirmed that immune lymph node cells are potent in accelerating the clearance of virus from the primary site of replication (the inoculation site). This effect was T cell dependent. However, if injection of the same cell population was delayed until ganglionic infection was established, the appearance of the zosteriform rash was not prevented, and the virus titer recovered from the lower flank was not reduced. Immunoperoxidase studies showed that virus is at first highly localized to the epidermis after it emerges from nerves. As determined by conventional histology, little cellular infiltration was seen until clinical lesions were apparent. These observations indicate that recrudescent lesions appear in the presence of cell populations normally associated with rapid virus clearance; cellular immune mechanisms may be rendered ineffective owing to the lack of recruitment to the site of recrudescence until tissue breakdown instigates an inflammatory response.

Recovery from lethal herpes simplex virus type 1 infection is mediated by cytotoxic T lymphocytes

The ability of herpes simplex virus (HSV)-specific, cytotoxic T lymphocytes to mediate recovery of mice lethally infected with HSV was examined. Adoptive transfer of splenocytes from mice that had been primed in vivo with HSV and restimulated with HSV in vitro protected lethally infected normal and cyclophosphamide-immunosuppressed mice from death. In contrast, equal numbers of normal splenocytes or immune splenocytes cultured without antigen failed to mediate recovery. Recovery was also transferred by noncultured, primary immune splenocytes, although the protective efficacy of these cells was 10-fold less than when immune splenocytes restimulated in vitro were used. Treatment of the cells with anti-Thy 1 or anti-Lyt 2.1 plus complement before adoptive transfer abrogated recovery. No decrease in protection was seen when in vitro-restimulated splenocytes were treated with anti-Lyt 1.1 plus complement. Splenocytes expression natural killer activity also failed to effect recovery. The administration of hyperimmune anti-HSV antibody to normal, immunocompetent mice resulted in recovery, whereas no significant protection of immunosuppressed mice by anti-HSV was observed. When antibody was given concurrently with cultured immune splenocytes, the percentage of mice that recovered from infection was greater than that seen with either antibody or cultured immune splenocytes alone. These experiments demonstrate that Lyt 2-positive cells with cytotoxic activity generated by in vitro immunization can mediate recovery from lethal HSV infection, whereas, under the conditions chosen, Lyt 1-positive cells were unable to mediate recovery.