Can a herpes simplex virus type 1 neuroinvasive score be correlated to other risk factors in Alzheimer's disease?

Herpes simplex virus type 1 (HSV-1) is latent in the nervous system of most humans. Ball [Can J Neurol Sci 9 (1982) 303] first suggested the hypothesis that HSV-1 could be involved in the pathogenesis of Alzheimer's Disease (AD) by noting that regions of the brain particularly and earliest affected in AD were the same as those most damaged during HSV encephalitis. Data from Itzhaki's research suggests that HSV-1 in the brain and the carriage of an apolipoprotein E allele 4 (ApoE e4) together confer risk for AD [J Pathol 97 (2002) 395], [Mol Chem Neuropathol 28 (1996) 135], [Alzheimer's Rep 1 (1998) 173], [Biochem Soc Trans 26 (1998) 273]. Of the two other studies based on Itzhaki's findings, one showed similar results [Lancet 349 (1997) 1102], and the other showed a similar trend [Lancet 351 (1998) 1330], [Lancet 352 (1998) 1312]. To further examine the role of HSV-1 in the etiology of AD, we have formulated a Neuroinvasive Score that quantifies the presence and viral load of HSV-1 in eight brain regions. These regions are: entorhinal cortex, hippocampus, pons, cerebellum, and neocortex (temporal, parietal, occipital, and frontal). We hypothesize that the Neuroinvasive Score that encompasses the presence, amount, and extent of HSV-1 spreading (neuroinvasiveness), will correlate with the genetic risk factor, ApoE e4, in the assessment of autopsy samples from AD patients. If the neuroinvasive score can be directly correlated to the different stages of AD (mild, moderate, severe), this will strengthen the hypothesis that HSV-1 is involved in AD and that ApoE e4 also confers risk for the development and progression of AD.

Murine keratocytes function as antigen-presenting cells.

Keratocytes express MHC class I molecules constitutively, and keratocytes stimulated with IFN-gamma express MHC class II molecules. Unstimulated keratocytes constitutively express B7-1 and ICAM-1, as well as low levels of CD40 and 4-1BBL. These findings indicate that keratocytes may deliver both antigen-specific and costimulatory signals to CD4(+) and CD8(+) T cells. To demonstrate that keratocytes expressing B7-1 provide a costimulatory signal to T cells, CD4(+) or CD8(+) mouse T cells were incubated with anti-CD3 mAb and irradiated keratocytes. Enhanced proliferation of both CD4(+) and CD8(+) T cells occurred, and could be inhibited by anti-B7-1 mAb, indicating T cell costimulatory activity by B7-1 on the keratocytes. To demonstrate that keratocytes can deliver an antigen-specific signal, CD4(+) and CD8(+) T cells from herpes-infected mice were incubated with HSV-1-infected, irradiated keratocytes. The resulting T cell proliferation and production of Th1 cytokines (IL-2, IFN-gamma) indicated T cell activation by antigens presented by the infected keratocytes. These results show that keratocytes in the corneal stroma of the mouse can function as antigen-presenting cells and, thus, may play a role in immune-mediated stromal inflammation such as herpetic stromal keratitis.

Growing vascular endothelial cells express somatostatin subtype 2 receptors.

We hypothesized that non-proliferating (quiescent) human vascular endothelial cells would not express somatostatin receptor subtype 2 (sst 2) and that this receptor would be expressed when the endothelial cells begin to grow. To test this hypothesis, placental veins were harvested from 6 human placentas and 2 mm vein disks were cultured in 0.3% fibrin gels. Morphometric analysis confirmed that 50-75% of cultured vein disks developed radial capillary growth within 15 days. Sst 2 gene expression was determined by reverse transcription-polymerase chain reaction (RT-PCR) analysis of the RNA from veins before culture and from tissue-matched vein disks that exhibited an angiogenic response. The sst 2 gene was expressed in the proliferating angiogenic sprouts of human vascular endothelium. The presence of sst 2 receptors on proliferating angiogenic vessels was confirmed by immunohistochemical staining and in vivo scintigraphy. These results suggest that sst 2 may be a unique target for antiangiogenic therapy with sst 2 preferring somatostatin analogues conjugated to radioisotopes or cytotoxic agents.

The immune response to ocular herpes simplex virus type 1 infection.

Herpes simplex virus type 1 (HSV-1) is a prevalent microbial pathogen infecting 60% to 90% of the adult world population. The co-evolution of the virus with humans is due, in part, to adaptations that the virus has evolved to aid it in escaping immune surveillance, including the establishment of a latent infection in its human host. A latent infection allows the virus to remain in the host without inducing tissue pathology or eliciting an immune response. During the acute infection or reactivation of latent virus, the immune response is significant, which can ultimately result in corneal blindness or fatal sporadic encephalitis. In fact, HSV-1 is one of the leading causes of infectious corneal blindness in the world as a result of chronic episodes of viral reactivation leading to stromal keratitis and scarring. Significant inroads have been made in identifying key immune mediators that control ocular HSV-1 infection and potentially viral reactivation. Likewise, viral mechanisms associated with immune evasion have also been identified and will be discussed. Lastly, novel therapeutic strategies that are currently under development show promise and will be included in this review. Most investigators have taken full advantage of the murine host as a viable working in vivo model of HSV-1 due to the sensitivity and susceptibility to viral infection, ease of manipulation, and a multitude of developed probes to study changes at the cellular and molecular levels. Therefore, comments in this review will primarily be restricted to those observations pertaining to the mouse model and the assumption (however great) that similar events occur in the human condition.

Gene expression analyzed by microarrays in HSV-1 latent mouse trigeminal ganglion following heat stress.

An understanding of the cellular genes whose expression is altered during HSV reactivation will enable us to better understand host responses and biochemical pathways involved in the process. Furthermore, this knowledge could allow us to develop gene-targeted inhibitors to prevent viral reactivation. Mice latent with HSV-1 strain McKrae and uninfected control mice were subjected to hyperthermic stress (43 degrees C for 10 min) and their trigeminal ganglia (TG) collected 1 h later. Two additional groups included HSV-1 latently infected and uninfected mice not subjected to hyperthermic stress. Poly A+ mRNA was enriched from total mouse TG RNA and reverse transcribed using MMLV RT. Radioactively labeled cDNAs were analyzed by microarray analysis. A stress/toxicology array of 149 mouse genes on a nylon membrane was used. The labeled cDNAs prepared from latently infected, stressed mice demonstrated 3-fold or greater increases in certain mRNA-early response genes (ERGs) compared to cDNAs from uninfected, stressed control mice. The ERG mRNAs that showed increases included two heat shock proteins (HSP60 and HSP40), a basic transcription factor (BTF T62), a DNA repair enzyme, two kinases [MAP kinase and a stress-induced protein kinase (SADK)], an oxidative stress-induced protein, a manganese superoxide dismutase precursor-2 (SOD-2), and cyclooxygenase 2 (COX-2). The gene expression in unstressed, infected TGs was similar to the gene expression in unstressed, uninfected controls. These results suggest that there is a significant difference in the ERG expression profile in latently infected TGs undergoing stress-induced reactivation compared to uninfected TGs.

Progressive nuclear translocation of somatostatin analogs.

UNLABELLED: Optimal cancer radiotherapy using Auger electron emitters requires selective localization of radionuclides in close proximity to tumor DNA. METHODS: Intracellular trafficking of (125)I-Tyr1-somatostatin-14 somatotropin-release inhibiting factor (SRIF) and 2 of its analogs, (125)I-WOC 4a and (111)In-pentetreotide, was studied in human neuroblastoma cells. RESULTS: After 24-h incubation, SRIF was degraded or recycled, whereas its protease-resistant analogs progressively accumulated in nuclear fractions. (111)In-pentetreotide binding to DNA increased over time in somatostatin receptor-positive cells but not in somatostatin receptor-negative cells. CONCLUSION: These in vitro studies show that prolonged exposure to radiolabeled SRIF analogs significantly increases their cellular internalization, nuclear translocation, and DNA binding. Clinically, infusion of radiolabeled somatostatin analogs may enhance tumor uptake and retention and provide more effective in situ radiotherapy.

Evidence for antigenic cross-reactivity between herpesvirus and the acetylcholine receptor.

Herpes simplex virus (HSV) is neurotropic and can pass from neuron to neuron at nerve terminals. During the long evolutionary relationship between HSV and vertebrates, this virus may have evolved surface ligands that mimic nerve cell receptors. The present study was undertaken to determine if herpes simplex virus type 1 (HSV-1) has an antigenic relationship with the acetylcholine receptor (AChR). Mice immunized with HSV-1 antigens or an AChR-expressing cell line were tested for antibodies directed against the AChR. By flow cytometry and ELISA, mouse anti-HSV-1 sera were found to contain antibodies that would bind to an epitope on the plasma membrane of AChR-expressing cells. Mice immunized with the AChR-expressing cells were tested for their resistance to HSV-1 infection. Statistically significantly more of the animals immunized with AChR-expressing cells resisted infection and fatal encephalitis, compared to control animals immunized with a cell line not expressing the AChR. Sera from AChR-immunized mice were tested for anti-HSV antibody by ELISA and were found to contain antibodies cross-reactive with HSV-1 antigens. These sera also neutralized virus in a plaque inhibition assay. The results indicate that there are one or more antigenic epitopes shared by herpesvirus and the AChR. Studies are in progress to define the pathogenetic significance of this molecular mimicry.

Persistent infection of a lymphoma cell line by herpes simplex virus.

The peripheral blood cells from a patient with a B-cell lymphoma were established in long-term tissue culture. Two years after establishment of the cells in culture they were infected with herpes simplex virus type 2 and the productivity and duration of viral persistence investigated. One week after infection the lymphoblastoid cells were productively infected and have remained so for a period of over 3 years. Expression of a viral glycoprotein antigen was evaluated by using a fluorescein-labeled monoclonal anti-herpes simplex virus type 2 antibody and revealed a spectrum of staining reactions grading from a lightly stippled to very intense pattern. Polymerase chain reaction analysis of the infected cells revealed the presence of the herpes simplex virus type 2 DNA polymerase gene in the infected cells that was absent from the uninfected lymphoblastoid cells. These results taken together with the long-term growth characteristics of both the infected and uninfected lymphoblastoid cells suggest that this cell line may be a good model system for studying viral infection, viral replication, viral latency, and clinical application for the isolation of human herpes virus.

Reactivation of herpes virus after lamellar keratoplasty.

PURPOSE: To determine if lamellar keratoplasty in rabbits latently infected with herpes simplex virus type 1 (HSV-1) would stimulate graft recipients to shed virus and induce viral-specific corneal lesions. METHODS: Rabbits latently infected with HSV-1 received lamellar allografts in one eye from normal uninfected rabbits and the contralateral eyes served as unoperated controls. Normal rabbits received lamellar grafts from rabbits latently infected with HSV-1. For 1 week after surgery, slit-lamp examination and ocular swab sampling were performed daily to assess viral reactivation. RESULTS: The occurrence of positive swab cultures and corneal epithelial lesions after lamellar keratoplasty was significantly higher in operated eyes of latently infected rabbits when compared to the control eyes. Ocular shedding or recurrent lesions were not observed in the normal rabbits receiving corneal grafts from latently infected donors. CONCLUSIONS: These results indicated that lamellar keratoplasty induces HSV-1 shedding and recurrent epithelial lesions in the eyes of rabbits latently infected with HSV-1, which received lamellar grafts, but not in the eyes of normal rabbits given lamellar grafts from HSV-1 latently infected rabbits. It seems that the site of viral latency is not the anterior corneal stroma or the epithelium.

The relationship between interleukin-6 and herpes simplex virus type 1: implications for behavior and immunopathology.

Cytokines are hormones once thought to be restricted to the immune system produced solely by hematopoietic-derived cells and acting on receptors expressed by cells of the immune system. However, it is now clear that many cytokines are produced not only by lymphocytes, monocytes, granulocytes, and dendritic cells but are also synthesized by cells outside the realm of the immune system in response to stimuli that may not be associated with immune homeostasis. In fact, there is evidence supporting a role of selected cytokines modifying behavior and neuroendocrine function. Recently, a potential relationship between the cytokine interleukin (IL)-6 and herpes simplex virus type 1 (HSV-1) reactivation has been found. This article discusses the relevance of these findings and considers the potential impact that HSV-1 infection has on behavior and chronic inflammatory processes that can occur in the nervous system during "latent" virus infection as a result of chronic IL-6 expression.

Protection of corneal allografts by CTLA4-Ig.

PURPOSE: CTLA4, a high-affinity ligand of B7, can, in soluble form, prevent antigen-driven T-cell activation by blocking CD28-B7 interaction and can thereby prevent immune graft rejection. In this study, we tested the capacity of soluble CTLA4-Ig alone or in combination with UV-B irradiation to suppress corneal allograft rejection in rabbits. METHODS: Corneas from Dutch belted rabbits were incubated in corneal storage medium containing 0, 1, 10, 25, or 250 microg/ml of CTLA4-Ig for 18 h and were then transplanted into the vascularized or nonvascularized corneas of New Zealand White rabbit recipients. A series of donor corneas were exposed to UV-B irradiation alone or a combination of irradiation and CTLA4-Ig to determine if these two treatments would have an additive effect in prolonging graft survival. The fate and clinical condition of the allografts were evaluated by slit-lamp photomicroscopic observation and corneal-thickness measurements. Grafts that were rejected were processed for histopathologic and immunohistochemical analysis to determine the characteristics of cells infiltrating the grafts. RESULTS: Grafts placed in nonvascularized corneas showed no differences in survival times, regardless of treatment. Among the grafts placed in vascularized corneas, those incubated with CTLA4-Ig at a concentration of 250 microg/ml failed within 7-14 days. Histopathologic and immunocytochemical examination revealed a dense accumulation of immune inflammatory cells, especially class II major histocompatibility complex (MHC)-expressing, antigen-presenting cells, in the failed grafts. Grafts incubated with CTLA4-Ig at concentrations of 1 and 10 microg/ml had mean survival times greater than the control, untreated corneal allografts. Some of the grafts in these two treatment groups survived for the 100-day observation period, whereas none of the grafts in the other treatment groups survived to this end point. UV-B irradiated grafts incubated with CTLA4-Ig at a concentration of 1 microg/ml appeared to have longer survival times and fewer rejections compared with control, untreated grafts and grafts treated with UV-B or CTLA4-Ig alone. CONCLUSION: The results show that the CTLA4-Ig coreceptor blocking agent can prolong corneal allograft survival in vascularized graft sites and that UV-B irradiation followed by incubation in CTLA4-Ig may prolong graft survival better than either treatment alone. These results suggest that agents that prevent second-signal interaction between antigen-presenting cells and T lymphocytes may be useful for inhibiting corneal allograft rejection.

Prolonged survival of corneal allografts incubated in alloantibody fragments.

BACKGROUND: In this study, we determined the binding characteristics of F(ab')2 alloantibody fragments to corneal antigens and assessed the capacity of these antibody fragments to protect corneal allografts from immune attack. METHODS: Goat anti-rabbit alloantibodies were pepsin-digested and labeled with 125I, and the time course of association and dissociation of the F(ab')2 fragments was determined. Corneal allografts were incubated in unlabeled F(ab')2 fragments and transplanted into allogeneic recipients, and the graft survival times were recorded. RESULTS: Binding of radiolabeled F(ab')2 fragments to rabbit cornea cells reached a maximum at 12 hr. At 32 degrees C (rabbit corneal temperature), the radiolabel eluted rapidly from the cornea, reaching baseline at 72 hr. At 4 degrees C (corneal graft storage temperature), significant amounts remained associated with the cornea at 96 hr. Mean survival time for grafts incubated in F(ab')2 anti-rabbit fragments was significantly greater than that of grafts incubated in nonimmune F(ab')2 fragments. Three of the corneal allografts incubated in goat F(ab')2 anti-rabbit fragments survived for 100 days, whereas the longest surviving control allograft incubated in goat F(ab')2 nonimmune fragments was rejected on day 24. Preincubation of corneas in unlabeled, immune F(ab')2 fragments followed by incubation in radiolabeled, immune F(ab')2 fragments suggested that antigen masking was not a factor in the prolongation of graft survival. CONCLUSION: Based on the binding and release kinetics and the graft survival times, it appears that the protective effect of immune F(ab')2 fragments extends well beyond the binding interval of the antibody fragments to corneal cell membranes.

The inherent quantitative capacity of the reverse transcription-polymerase chain reaction.

The quantitative capacity of the reverse transcription-polymerase chain reaction (RT-PCR) is generally underestimated. In this study, PCR and RT-PCR products were amplified from serially diluted DNA and RNA templates, respectively, using a 35-cycle PCR. In the approximate 30- to 100-fold range of template input above the lower limit of detection, herpes simplex virus ICP27 RT-PCR product yield was dependent on the logarithm of template mRNA input (r2 = 0.99). Likewise, regression analysis indicated that yields of interleukin-12 p40, herpes simplex virus DNA polymerase, and interferon-gamma PCR products were dependent on the logarithm of template DNA input over 40- (r2 = 0.98), 60- (r2 = 0.96), and 100-fold (r2 = 0.99) ranges, respectively. This quantitative relationship appears to derive from the competition for reactants between specific PCR products and nonspecific primer-dimers that occurs at limiting concentrations of template. Although primer-dimers are not generally considered a common feature of PCR, 30 of 32 primer pairs tested in this study produced primer-dimer amplification in the absence of template. Because the coefficient of variation in replicate PCRs was typically 10-20% in the linear range, the precision of PCR was sufficient to measure 4-fold differences in template concentration. Thus, with statistically adequate sample numbers, an appropriate standard curve, and the inherent quantitative capacity of the method, differences in the abundance of a mRNA species are measurable by 35-cycle RT-PCR.

Immunization with HSV-1 antigen rapidly protects against HSV-1-induced encephalitis and is IFN-gamma independent.

Herpes simplex virus type 1 (HSV-1) infection of mice frequently culminates in fatal encephalitis. Intraperitoneal administration of heat-inactivated HSV-1 0-5 days before infection (active immunization) protected mice from encephalitis. In addition, active immunization 2-5 days before ocular infection with HSV-1 reduced the frequency of establishment of latent HSV-1 infection in the trigeminal ganglion (TG). However, intraperitoneal administration of heat-inactivated HSV-1 did not induce interferon (IFN) production in the peritoneum or serum, as determined by bioassay and ELISA. Intraperitoneal administration of heat-attenuated HSV-1 elicited IFN-gamma but not type I IFN production in the peritoneum. The production of IFN-gamma correlated with the infiltration of CD4 and CD8 cells in the peritoneum as determined by RT-PCR. In addition, there was a significant increase in interleukin (IL)-12 p40, IL-12p35, IL-6, IL-10, and IFN-gamma mRNA in peritoneal cells, as determined by RT-PCR following immunization with heat-attenuated HSV-1, which was not observed using heat-inactivated HSV-1. The results suggest that resistance to HSV-1 is induced rapidly following immunization with viral antigen but that protection against encephalitis is independent of the cytokines that are generated in the peritoneum.

Acyclovir blocks cytokine gene expression in trigeminal ganglia latently infected with herpes simplex virus type 1.

We have previously found that interleukin (IL)-2, IL-10, interferon (IFN)-gamma, RANTES, and tumor necrosis factor (TNF)-alpha mRNA transcription remain elevated in the trigeminal ganglia (TG) of herpes simplex virus type 1 (HSV-1) latently infected mice up to 120 days postinoculation (p.i.). To determine if this phenomenon was dependent on HSV-1 DNA replication after the establishment of latency (i.e., reactivation), cytokine gene expression was compared in TG of acyclovir-treated and untreated latently infected mice. Oral acyclovir treatment (begun 16 days p.i.) had no effect on serum levels of total anti-HSV-1 antibodies. However, there was a significant reduction in the titer of antibody specific for glycoprotein D and glycoprotein B but not glycoprotein H/L 120 days PI in the acyclovir-treated compared to vehicle-treated mice. These differences were not significant at earlier time points (i.e., days 34 and 60 p.i.). Consistent with these findings, acyclovir had no effect on cytokine gene expression in latently infected TG 35 and 60 days p.i. However, 120 days p.i., IFN-gamma and TNF-alpha mRNA were approaching baseline levels in TG of acyclovir-treated mice, but remained significantly elevated in untreated controls (i.e., IFN-gamma mRNA levels were sixfold higher in TG of untreated mice). Therefore, viral DNA replication appears to provide an antigenic stimulus for persistent cytokine gene expression in latently infected TG.

Innate and acquired immunity to herpes simplex virus type 1.

Immunization with heat-inactivated herpes simplex virus type 1 (HSV-1) 2-5 days before ocular infection reduced the frequency of establishment of latent HSV-1 infection in the trigeminal ganglion (TG); this induction of resistance coincided with reduced expression of IFN-gamma mRNA in the TG. Immunization with unrelated antigens was not protective. In part, this resistance to nervous system invasion correlated with the appearance of serum antibody to HSV-1. Immunization reduced viral replication in the eye and trigeminal ganglion, and prevented HSV-1 spread to the cerebellum. IFN-gamma was detected in immunized mice 4 days postocular infection as determined by plaque reduction using neutralizing Ab to IFN-alpha/beta and IFN-gamma. Injection of antibody (Ab) to IFN-alpha/beta and IFN-gamma administered at the time of immunization did not affect survival. Anti-IFN-gamma-treated mice had significantly reduced levels of IFN in their serum. Treatment with anti-IFN-alpha/beta Ab resulted in an elevation in viral replication as determined by the expression of latency associated transcripts in the TG of mice. Likewise, there was a significant increase in the CD8, IL-12 (p40), and TNF-alpha mRNA levels in the TG of the anti-IFN-alpha/beta-treated mice TG explant cultures demonstrated that viral load was significantly increased in the TG of anti-IFN-alpha/beta-treated mice relative to TG of control mice 7 days after infection. The results suggest that exposure to viral antigens 2-5 days before infection is an important determinant of the extent of HSV-1 spread to the nervous system. Moreover, the data suggest that both an antibody response and IFN-alpha/beta play a role in limiting the progress of infection from the peripheral tissues to the central nervous system.

Detection of substance P in human tears by laser desorption mass spectrometry and immunoassay.

PURPOSE: To determine whether substance P is present in human tears. METHODS: Tear samples (1-2 microliters) were collected from one eye of each of 12 subjects. Two of the eyes had dry eye syndrome, two wore contact lenses and had dry eye syndrome, and eight were normal. Five of the eight normal eyes were scheduled to undergo excimer laser refractive surgery, and tears were collected from these eyes before and after surgery. Tear samples were analyzed by laser desorption mass spectrometry. Pooled samples from one individual were subjected to enzyme-linked immunoabsorbent assay. RESULTS: Laser desorption mass spectra of the 18 tear samples displayed well defined peaks with mass to charge (m/z) ratios ranging from 1343.7 to 1355.9 and/or 1356.9 to 1364.7, corresponding to an average m/z of 1349.8 +/- 1.13 for protonated substance P and 1361.2 +/- 0.54 for oxidized substance P obtained from 14 mass spectra of standards formulated with substance P concentrations ranging from 10(-4) M to 10(-12) M. As confirmation, an enzyme-linked immunoabsorbent assay performed twice on pooled tears from one eye detected substance P in both replicates at a concentration of 125 pg/ml (9.26 x 10(-11) M). CONCLUSIONS: These findings demonstrate that substance P is a component of tears obtained from normal eyes of men and women ranging in age from 26 to 60 years, from eyes fitted with contact lenses, from eyes with dry eye syndrome, and from eyes 1 and 2 days after excimer laser refractive surgery. Whether the concentration of substance P in tears varies with sex, age, or eye condition, the source of substance P in tears, and its role in tears remains to be discovered.

Breast cancer increases initiation of angiogenesis without accelerating neovessel growth rate.

BACKGROUND: Recurrence and mortality rates in patients with breast cancer correlate with the degree of tumor angiogenesis (angiogenic index). We have developed a novel angiogenesis model by using disks of fresh human placental vein that initiate an angiogenic response and exhibit linear radial capillary growth in culture. We hypothesized that the addition of human breast cancer cells to this human placental vein angiogenesis model would increase the incidence of angiogenesis and accelerate the rate of neovessel growth compared with vein disk cultured without tumor cells. METHODS: To test this hypothesis, vein explants from seven human placentas were incorporated into clots of 0.3% fibrin in Medium 199 and fetal bovine serum with or without 1.5 x 10(5) T-47D (n = 6 placentas) or MCF-7 (n = 1 placenta) breast cancer cells. Statistical differences between the experimental (with breast cancer cells) and control (no added cells) cultures were determined by repeated measures ANOVA. RESULTS: The proportion of disks exhibiting neovessel growth (initiation) by day 12 was significantly increased in the presence of T-47D cells (p < 0.05 at day 12, p < 0.001 at day 15). No statistical difference was seen in rates of neovessel growth (millimeters per day). Similar results were seen with MCF-7 cells. CONCLUSIONS: Tumor enhancement of angiogenesis may occur by increased initiation of the angiogenic response. Subsequent vessel growth rates may be tumor independent. We predict that effective antiangiogenic therapies will block a tumor's ability to augment angiogenesis initiation rather than subsequent neovessel growth.

Nerve growth factor antibody stimulates reactivation of ocular herpes simplex virus type 1 in latently infected rabbits.

Anti-nerve growth factor (anti-NGF) antibody has been shown to induce reactivation of latent herpes simplex virus type 1 (HSV-1) in vitro. We found that systemically administered anti-NGF induces ocular shedding of HSV-1 in vivo in rabbits harboring latent virus. Rabbits in which HSV-1 latency had been established were given intravenous injections of goat anti-NGF serum daily for 10 days beginning 42 days after primary viral infection. Tears were assayed for virus for 12 days beginning on the day of the first injection. All eight rabbits given high titer anti-NGF had infectious virus in their tears at least once during the 12-day period. Fifteen of 16 eyes were positive and the average duration of viral shedding for these eyes was 4.0 days. Latently infected rabbits receiving daily injections of nonimmune goat serum or saline for 10 consecutive days were controls. Only six of the 16 (38%) eyes from rabbits receiving nonimmune goat serum shed virus. Only one of 12 eyes from untreated rabbits shed virus. Sera from control rabbits had no detectable anti-NGF activity; titers in anti-NGF-treated rabbits ranged between 1:1000 and 1:10,000. NGF deprivation may act as a neuronal stressor and may share a common second messenger pathway with heat- or cold-stress induced reactivation of latent HSV-1.

Anti-interleukin-6 antibodies inhibit herpes simplex virus reactivation.

Herpes simplex viruses (HSVs) infect epithelial cells, become localized in neurons, and can reactivate in response to a variety of stimuli, including ultraviolet light and hyperthermia. The sequence of gene activation during viral replication is known, but the molecular linkage between exogenous stimuli and HSV reactivation has not been determined. It was hypothesized that interleukin (IL)-6 acts as a signal between exogenous stimuli and neurons, stimulating HSV reactivation from latency. Mouse corneas were infected with HSV-1, and ocular reactivation was induced 5-7 weeks later by thermal stress or corneal exposure to ultraviolet light. Anti-IL-6 monoclonal antibodies were administered to the latently infected mice 8-12 h before the reactivation stimulus. Treatment with anti-IL-6 antibodies resulted in significantly lower frequencies of ocular reactivation compared with those in mice treated with a control immunoglobulin. These results support the hypothesis that IL-6 plays a role in HSV reactivation from latency.