Vaccinia virus-mediated damage of murine ovaries and protection by virus-expressed interleukin-2

Orally Administrated Recombinant Vaccinia Virus Displaying ROP4 Induces Protection against Toxoplasma gondii Challenge Infection

Recombinant vaccinia viruses (rVVs) are attenuated viruses and are widely utilized as vectored vaccine platforms against numerous diseases. However, the protective efficacy of these rVV vaccines against Toxoplasma gondii and the resulting mucosal immunity has not been thoroughly assessed. Here, rVVs expressing the rhoptry protein 4 (ROP4) of T. gondii were generated. To evaluate the protection induced by the vaccines, mice were orally immunized with the ROP4-rVVs and subsequently challenge-infected with a lethal dose of T. gondii ME49 strain. Immunization with the rVVs induced higher levels of parasite-specific IgG and IgA antibody responses in sera compared to unimmunized control (NC). Upon challenge infection, significantly higher levels of IgG or IgA antibody responses in the brain, intestines, and vaginal samples were found in the immunized mice compared to NC. The ROP4-rVV vaccination elicited potent IgG and IgA secreting cell (ASC) responses, while substantially enhancing germinal center B cell, as well as CD4⁺ and CD8⁺ T cell responses from lymphoid organs. The production of pro-inflammatory cytokines IFN-γ and IL-6 in the brains was markedly diminished following immunization. The immunized mice also experienced reduced bodyweight loss and possessed fewer brain cysts than the control group. These results suggest that oral delivery of ROP4 displaying rVVs induced mucosal and systemic immunities that contributed to protection against lethal T. gondii challenge infection.

Viral infection of the ovaries compromises pregnancy and reveals innate immune mechanisms protecting fertility

Viral infections during pregnancy are a considerable cause of adverse outcomes and birth defects, and the underlying mechanisms are poorly understood. Among those, cytomegalovirus (CMV) infection stands out as the most common intrauterine infection in humans, putatively causing early pregnancy loss. We employed murine CMV as a model to study the consequences of viral infection on pregnancy outcome and fertility maintenance. Even though pregnant mice successfully controlled CMV infection, we observed highly selective, strong infection of corpus luteum (CL) cells in their ovaries. High infection densities indicated complete failure of immune control in CL cells, resulting in progesterone insufficiency and pregnancy loss. An abundance of gap junctions, absence of vasculature, strong type I interferon (IFN) responses, and interaction of innate immune cells fully protected the ovarian follicles from viral infection. Our work provides fundamental insights into the effect of CMV infection on pregnancy loss and mechanisms protecting fertility.

Virus analog decreases estradiol secretion in FSH-treated human ovarian granulosa cells

The aim of this study was to evaluate the effect of virus infection on estradiol (E₂) production in human ovarian granulosa cells. Polyriboinosinic polyribocytidylic acid [Poly (I: C)], a synthetic analog of viral double stranded RNA that can be recognized by Toll like receptor 3 (TLR3), was used to imitate virus infection. Granulosa cells (GCs) obtained from patients undergoing in vitro fertilization and embryo transfer (IVF-ET) were cultured in vitro and treated with Poly (I: C), FSH, or both. Concentration of E₂ was assayed by electrochemiluminescence. The mRNA and protein expression of TLR3 and aromatase were determined by real-time quantitative PCR (qPCR) and Western blot, respectively. The results showed that expression of TLR3 mRNA was significantly increased after Poly (I: C) stimulation. Poly (I: C) decreased E₂ synthesis in FSH-treated GCs. Poly (I: C) inhibited the expression of aromatase in FSH-treated GCs. This study demonstrated that Poly (I: C) inhibits the synthesis of estradiol by granulosa cells under the stimulation of FSH, which might contribute to disturbance of follicular development and ovulation.

Safety of an Oncolytic Myxoma Virus in Dogs with Soft Tissue Sarcoma

Many oncolytic viruses that are efficacious in murine cancer models are ineffective in humans. The outcomes of oncolytic virus treatment in dogs with spontaneous tumors may better predict human cancer response and improve treatment options for dogs with cancer. The objectives of this study were to evaluate the safety of treatment with myxoma virus lacking the serp2 gene (MYXVΔserp2) and determine its immunogenicity in dogs. To achieve these objectives, dogs with spontaneous soft tissue sarcomas were treated with MYXVΔserp2 intratumorally (n = 5) or post-operatively (n = 5). In dogs treated intratumorally, clinical scores were recorded and tumor biopsies and swabs (from the mouth and virus injection site) were analyzed for viral DNA at multiple time-points. In all dogs, blood, urine, and feces were frequently collected to evaluate organ function, virus distribution, and immune response. No detrimental effects of MYXVΔserp2 treatment were observed in any canine cancer patients. No clinically significant changes in complete blood profiles, serum chemistry analyses, or urinalyses were measured. Viral DNA was isolated from one tumor swab, but viral dissemination was not observed. Anti-MYXV antibodies were occasionally detected. These findings provide needed safety information to advance clinical trials using MYXVΔserp2 to treat patients with cancer.

Development of a Safe and Effective Vaccinia Virus Oncolytic Vector WR-Δ4 with a Set of Gene Deletions on Several Viral Pathways

Despite the effectiveness of classic treatments and available diagnostic tools, cancer continues to be a leading world health problem, with devastating cancer-related death rates. Advances in oncolytic virotherapy have shown promise as potentially effective treatment options in the fight against cancer. The poxviruses have many features that make them an attractive platform for the development of oncolytic vectors, with some candidates currently in clinical trials. Here, we report the design and generation of a new oncolytic vector based on the vaccinia virus Western Reserve (WR) strain. We show that the WR-Δ4 virus, with the combined deletion of four specific viral genes that act on metabolic, proliferation, and signaling pathways (A48R, B18R, C11R, and J2R), has effective anti-tumor capabilities in vivo. In WR-Δ4-infected mice, we observed strong viral attenuation, reduced virus dissemination, and efficient tumor cell growth control in the B16F10 syngeneic melanoma model, with enhanced neutrophil migration and activation of tumor antigen-specific immune responses. This approach provides an alternative strategy toward ongoing efforts to develop an optimal oncolytic poxvirus vector.

Safety and Immunogenicity of Modified Vaccinia Ankara-Bavarian Nordic Smallpox Vaccine in Vaccinia-Naive and Experienced Human Immunodeficiency Virus-Infected Individuals: An Open-Label, Controlled Clinical Phase II Trial

Background.  First- and second-generation smallpox vaccines are contraindicated in individuals infected with human immunodeficiency virus (HIV). A new smallpox vaccine is needed to protect this population in the context of biodefense preparedness. The focus of this study was to compare the safety and immunogenicity of a replication-deficient, highly attenuated smallpox vaccine modified vaccinia Ankara (MVA) in HIV-infected and healthy subjects. Methods.  An open-label, controlled Phase II trial was conducted at 36 centers in the United States and Puerto Rico for HIV-infected and healthy subjects. Subjects received 2 doses of MVA administered 4 weeks apart. Safety was evaluated by assessment of adverse events, focused physical exams, electrocardiogram recordings, and safety laboratories. Immune responses were assessed using enzyme-linked immunosorbent assay (ELISA) and a plaque reduction neutralization test (PRNT). Results.  Five hundred seventy-nine subjects were vaccinated at least once and had data available for analysis. Rates of ELISA seropositivity were comparably high in vaccinia-naive healthy and HIV-infected subjects, whereas PRNT seropositivity rates were higher in healthy compared with HIV-infected subjects. Modified vaccinia Ankara was safe and well tolerated with no adverse impact on viral load or CD4 counts. There were no cases of myo-/pericarditis reported. Conclusions.  Modified vaccinia Ankara was safe and immunogenic in subjects infected with HIV and represents a promising smallpox vaccine candidate for use in immunocompromised populations.

IL-12 is required for mTOR regulation of memory CTLs during viral infection

The induction of functional memory CTLs is a major goal of vaccination against intracellular pathogens. IL-12 is critical for the generation of memory CTLs, and inhibition of mTOR by rapamycin can effectively enhance the memory CTL response. Yet, the role of IL-12 in mTOR’s regulation of memory CTL is unknown. Here, we hypothesized that the immunostimulatory effects of mTOR on memory CTLs requires IL-12 signaling. Our results revealed that rapamycin increased the generation of memory CTLs in vaccinia virus infection, and this enhancement was dependent upon the IL-12 signal. Furthermore, IL-12 receptor deficiency diminished the secondary expansion of rapamycin-regulated memory, and resultant secondary memory CTLs were abolished. Rapamycin enhanced IL-12 signaling by up regulating IL-12 receptor β2 expression and STAT4 phosphorylation in CTLs during early infection. In addition, rapamycin continually suppressed T-bet expression in both WT and IL-12 receptor knockout CTLs. These results indicate an essential role for IL-12 in the regulation of memory CTLs by mTOR, and highlight the importance of considering the interplay between cytokines and adjuvants during vaccine design.

Susceptibility of the wild-derived inbred CAST/Ei mouse to infection by orthopoxviruses analyzed by live bioluminescence imaging

Classical inbred mice are extensively used for virus research. However, we recently found that some wild-derived inbred mouse strains are more susceptible than classical strains to monkeypox virus. Experiments described here indicated that the 50% lethal dose of vaccinia virus (VACV) and cowpox virus (CPXV) were two logs lower in wild-derived inbred CAST/Ei mice than classical inbred BALB/c mice, whereas there was little difference in the susceptibility of the mouse strains to herpes simplex virus. Live bioluminescence imaging was used to follow spread of pathogenic and attenuated VACV strains and CPXV virus from nasal passages to organs in the chest and abdomen of CAST/Ei mice. Luminescence increased first in the head and then simultaneously in the chest and abdomen in a dose-dependent manner. The spreading kinetics was more rapid with VACV than CPXV although the peak photon flux was similar. These data suggest advantages of CAST/Ei mice for orthopoxvirus studies.

Effector-like CD8⁺ T cells in the memory population mediate potent protective immunity

The CD8⁺ memory T cell population is heterogeneous, and it is unclear which subset(s) optimally mediate the central goal of the immune system-protection against infection. Here we investigate the protective capacities of CD8⁺ T cell subsets present at the memory stage of the immune response. We show that a population of CD8⁺ T cells bearing markers associated with effector cells (KLRG1(hi), CD27(lo), T-bet(hi), Eomes(lo)) persisted to the memory phase and provided optimal control of Listeria monocytogenes and vaccinia virus, despite weak recall proliferative responses. After antigen-specific boosting, this population formed the predominant secondary memory subset and maintained superior pathogen control. The effector-like memory subset displayed a distinct pattern of tissue distribution and localization within the spleen, and their enhanced capacity to eliminate Listeria involved specialized utilization of cytolysis. Together, these data suggest that long-lived effector CD8⁺ T cells are optimal for protective immunity against certain pathogens.

Effects of postchallenge administration of ST-246 on dissemination of IHD-J-Luc vaccinia virus in normal mice and in immune-deficient mice reconstituted with T cells

Whole-body bioimaging was used to study dissemination of vaccinia virus (VACV) in normal and in immune deficient (nu(-)/nu(-)) mice protected from lethality by postchallenge administration of ST-246. Total fluxes were recorded in the liver, spleen, lungs, and nasal cavities of live mice after intranasal infection with a recombinant IHD-J-Luc VACV expressing luciferase. Areas under the flux curve were calculated for individual mice to assess viral loads. Treatment for 2 to 5 days of normal BALB/c mice with ST-246 at 100 mg/kg starting 24 h postchallenge conferred 100% protection and reduced viral loads in four organs compared to control mice. Mice also survived after 5 days of treatment with ST-246 at 30 mg/kg, and yet the viral loads and poxes were higher in these mice compared to 100-mg/kg treatment group. Nude mice were not protected by ST-246 alone or by 10 million adoptively transferred T cells. In contrast, nude mice that received T cells and 7-day treatment with ST-246 survived infection and exhibited reduced viral loads compared to nonreconstituted and ST-246-treated mice after ST-246 was stopped. Similar protection of nude mice was achieved using adoptively transferred 1.0 and 0.1 million, but not 0.01 million, purified T cells or CD4(+) or CD8(+) T cells in conjunction with ST-246 treatment. These data suggest that ST-246 protects immunocompetent mice from lethality and reduces viral dissemination in internal organs and poxvirus lesions. Furthermore, immune-deficient animals with partial T cell reconstitution can control virus replication after a course of ST-246 and survive lethal vaccinia virus challenge.

Generation and characterization of a Cowpox virus mutant lacking host range factor CP77

Cowpox virus (CPXV) host range factor CP77 was identified to be required for virus replication in Chinese hamster ovary (CHO) cells, but the underlying molecular mechanism by which CP77 modulates host range has remained unclear. Therefore, a CPXVΔCP77 deletion mutant was constructed by applying bacterial artificial chromosome (BAC) technology. Integrity of BAC-derived viral DNA was confirmed by whole genome sequencing. In vitro growth characteristics of CPXV wild type (WT), BAC-derived vCPXV WT and vCPXVΔCP77 were virtually indistinguishable in HEK293T cells, whereas in CHO-K1 cells replication of virus lacking CP77 was unambiguously attenuated. This block of viral replication was confirmed by lack of late viral protein expression. The replication defect of various Orthopoxviruses lacking CP77 in CHO cells could be restored by recombinant expression of CP77. Thus, for the first time, the described CP77-dependent host range effect in CHO cells was shown in the background of CPXV as well as Camelpox virus. To further characterize the mutant virus, cells of several different species were comparably infected with vCPXV WT and vCPXVΔCP77, respectively. Interestingly, except for CHO-K1 cells, vCPXV WT and vCPXVΔCP77 showed no significant difference in terms of morphology of cytopathic effects, expression of a late transcribed virus-encoded green fluorescent protein and virus reproduction, even in other hamster-derived cells. Additionally, in ovo inoculation with either virus revealed the same red-pock phenotype on chicken egg chorioallantoic membranes. Since the data presented indicate a CP77-dependent host range effect only for CHO cells, we conclude that the protein might mediate additional functions not identified yet. The vCPXVΔCP77 deletion mutant generated can now be applied as a useful tool to investigate the function of the putative host range protein CP77.

Preferential replication of vaccinia virus in the ovaries is independent of immune regulation through IL-10 and TGF-β

Vaccinia virus (VACV) exhibits a strong tropism for ovarian tissue and can cause ovary pathology and sterility. Why VACV preferentially accumulates in this organ is not known. Here we show that multiple immune cell populations infiltrated the ovaries following VACV infection, including virus-specific CD8 T cells making both IFN-γ and TNF. This was also accompanied by the induction of interleukin (IL)-10 and TGF-β, suggesting that VACV may exploit the ovarian environment for immune evasion via induction of these suppressive cytokines. To test this we used several strategies, including neutralizing these cytokines, and exogenous targeting of the T-cell response, to determine if this inhibited virus replication in the ovaries. We found that the VACV-specific CD8 T-cell immunity and the clearance of virus were not enhanced in the ovaries of infected mice in which IL-10 receptor (IL-10R) was blocked with antagonist antibody. VACV replication was also only moderately affected in the ovaries of infected IL-10 knockout mice. Similarly, blockade of TGF-β with antagonist antibody demonstrated no effect on CD8 T-cell immunity or VACV replication. Lastly, an agonist antibody targeting the tumor necrosis factor receptor superfamily member OX40 (TNFRSF4) enhanced the number of VACV-specific CD8 T cells producing IFN-γ in lymphoid tissue, but had no effect on CD8 T-cell infiltration of the ovaries or on the viral load. Collectively, the results indicate that preferential replication of VACV in the ovaries may not be dependent on immune suppressive mechanisms in this tissue.

Modulation of NKp30- and NKp46-mediated natural killer cell responses by poxviral hemagglutinin

Natural killer (NK) cells are an important element in the immune defense against the orthopox family members vaccinia virus (VV) and ectromelia virus (ECTV). NK cells are regulated through inhibitory and activating signaling receptors, the latter involving NKG2D and the natural cytotoxicity receptors (NCR), NKp46, NKp44 and NKp30. Here we report that VV infection results in an upregulation of ligand structures for NKp30 and NKp46 on infected cells, whereas the binding of NKp44 and NKG2D was not significantly affected. Likewise, infection with ectromelia virus (ECTV), the mousepox agent, enhanced binding of NKp30 and, to a lesser extent, NKp46. The hemagglutinin (HA) molecules from VV and ECTV, which are known virulence factors, were identified as novel ligands for NKp30 and NKp46. Using NK cells with selectively silenced NCR expression and NCR-CD3ζ reporter cells, we observed that HA present on the surface of VV-infected cells, or in the form of recombinant soluble protein, was able to block NKp30-triggered activation, whereas it stimulated the activation through NKp46. The net effect of this complex influence on NK cell activity resulted in a decreased NK lysis susceptibility of infected cells at late time points of VV infection when HA was expression was pronounced. We conclude that poxviral HA represents a conserved ligand of NCR, exerting a novel immune escape mechanism through its blocking effect on NKp30-mediated activation at a late stage of infection.

Evaluating vaccinia virus cytokine co-expression in TLR GKO mice

Using Toll-like receptor (TLR) and MyD88 gene knock-out (GKO) mice the effect of TLRs and MyD88 on virus replication, interferon (IFN)-β production, natural killer (NK) cell and CD8T cell responses were assessed following ectromelia virus (ECTV) and recombinant vaccinia virus (rVV) infection. The capacity for rVVs encoding cytokines to restore immune function in MyD88(-/-) mice was clearly demonstrated. Results showed that TLR2(-/-), TLR4(-/-)and TLR7(-/-) mice survived ECTV infection whereas MyD88(-/-) and TLR9(-/-)mice, in contrast, were highly susceptible. Next, following infection with rVV, MyD88(-/-) mice elicited reduced serum IFN-β, NK cell and CD8T cell responses compared with wild-type mice, whereas TLR9(-/-) mice showed elevated CD8T cell responses. When MyD88(-/-)mice were infected with rVV co-expressing IFN-β these mice were able to restore IFN-β levels and CD8T cell responses but not NK cell activation. Interestingly, even though rVV co-expressing interleukin (IL)-2 enhanced NK cell activation in MyD88(-/-) mice, this was not associated with an antiviral effect, as observed in normal mice. Surprisingly, co-infection with rVV IL-2/rVV IL-12, but not rVV IL-2/rVV IFN-β, restored the attenuated phenotype of rVV IL-2 in MyD88(-/-) mice indicating that the IL-2/IL-12 combination promotes antiviral responses. Our results clearly show that the CD8T cell defect observed in MyD88(-/-) mice to vaccinia virus infection can be restored by rVV-encoding IFN-β demonstrating the critical role of this cytokine in T cell mediated immunity and illustrates that the model can provide an effective platform for the elucidation of cytokine immunobiology.

Gamma interferon-induced interferon regulatory factor 1-dependent antiviral response inhibits vaccinia virus replication in mouse but not human fibroblasts

Vaccinia virus (VACV) replicates in mouse and human fibroblasts with comparable kinetics and efficiency, yielding similar titers of infectious progeny. Here we demonstrate that gamma interferon (IFN-gamma) but not IFN-alpha or IFN-beta pretreatment of mouse fibroblasts prior to VACV infection induces a long-lasting antiviral state blocking VACV replication. In contrast, high doses of IFN-gamma failed to establish an antiviral state in human fibroblasts. In mouse fibroblasts, IFN-gamma impeded the viral replication cycle at the level of late gene transcription and blocked the multiplication of VACV genomes. The IFN-gamma-induced antiviral state invariably prevented the growth of different VACV strains but was not effective against the replication of ectromelia virus. The IFN-gamma effect required intact IFN-gamma receptor signaling prior to VACV infection through Janus kinase 2 (Jak2) and signal transducer and activator of transcription 1 (STAT1). The permissive state of IFN-gamma-treated human cells was unrelated to the VACV-encoded IFN decoy receptors B8 and B18 and associated with a complete disruption of STAT1 homodimer formation and DNA binding. Unlike human fibroblasts, mouse cells responded with long-lasting STAT1 activation which was preserved after VACV infection. The deletion of the IFN regulatory factor 1 (IRF-1) gene from mouse cells rescued efficient VACV replication, demonstrating that IRF-1 target genes have a critical role in VACV control. These data have implications for the understanding of VACV pathogenesis and identify an incongruent IFN-gamma response between the human host and the mouse model.

Targeted delivery of a suicide gene to human colorectal tumors by a conditionally replicating vaccinia virus

We have generated a thymidine kinase gene-deleted vaccinia virus (VV) (Copenhagen strain) that expressed the fusion suicide gene FCU1 derived from the yeast cytosine deaminase and uracil phosphoribosyltransferase genes. Intratumoral inoculation of this thymidine kinase gene-deleted VV encoding FCU1 (VV-FCU1) in the presence of systemically administered prodrug 5-fluorocytosine (5-FC) produced statistically significant reductions in the growth of subcutaneous human colon cancer in nude mice compared with thymidine kinase gene-deleted VV treatments or with control 5-fluorouracil alone. A limitation of prodrug therapies has often been the requirement for the direct injection of the virus into relatively large, accessible tumors. Here we demonstrate vector targeting of tumors growing subcutaneously following systemic administration of VV-FCU1. More importantly we also demonstrate that the systemic injection of VV-FCU1 in nude mice bearing orthotopic liver metastasis of a human colon cancer, with concomitant administration of 5-FC, leads to substantial tumor growth retardation. In conclusion, the insertion of the fusion FCU1 suicide gene potentiates the oncolytic efficiency of the thymidine kinase gene-deleted VV and represents a potentially efficient means for gene therapy of distant metastasis from colon and other cancers.

CD62L (L-selectin) down-regulation does not affect memory T cell distribution but failure to shed compromises anti-viral immunity

The down-regulation of CD62L that accompanies T lymphocyte activation is thought to redirect cells away from lymph nodes to sites of infection. In this study, CD62L was maintained on Ag-activated T cells and their distribution, and ability to clear pathogen from peripheral sites determined. CD62L was down-regulated on Ag-specific CD8 T cells in lungs of C57BL/6 mice but maintained in CD62L transgenic mice at day 8 after influenza infection. However, the numbers of influenza-specific CD8 T cells recruited were similar in CD62L transgenic and C57BL/6 mice. Memory CD8 T cell numbers in the lungs and noninvolved organs 100 days after primary infection were similar in CD62L transgenic and C57BL/6 mice, despite differing CD62L expression. Transgenic mice expressing wild-type CD62L cleared a recombinant vaccinia virus expressing an influenza-derived CD8 T cell epitope as efficiently as C57BL/6 mice. However, transgenic mice expressing a protease resistant mutant of CD62L showed significantly delayed viral clearance, despite normal CTL generation and the presence of CD107a and IFN-gamma expressing influenza-specific CD8 T cells. These results demonstrate that CD62L down-regulation is not required for CD8 memory cells to home to sites of infection. However, their ability to clear virus is significantly compromised if CD62L shedding is abrogated.

Oncolytic virotherapy for ovarian carcinomatosis using a replication-selective vaccinia virus armed with a yeast cytosine deaminase gene

In this study, we assessed the ability of a highly tumor-selective oncolytic vaccinia virus armed with a yeast cytosine deaminase gene to infect and lyse human and murine ovarian tumors both in vitro and in vivo. The virus vvDD-CD could infect, replicate in and effectively lyse both human and mouse ovarian cancer cells in vitro. In two different treatment schedules involving either murine MOSEC or human A2780 ovarian carcinomatosis models, regional delivery of vvDD-CD selectively targeted tumor cells and ovarian tissue, effectively delaying the development of either tumor or ascites and leading to significant survival advantages. Oncolytic virotherapy using vvDD-CD in combination with the prodrug 5-fluorocytosine conferred an additional long-term survival advantage upon tumor-bearing immunocompetent mice. These findings demonstrate that a tumor-selective oncolytic vaccinia combined with gene-directed enzyme prodrug therapy is a highly effective strategy for treating advanced ovarian cancers in both syngeneic mouse and human xenograft models. Given the biological safety, tumor selectivity and oncolytic potency of this armed oncolytic virus, this dual therapy merits further investigation as a promising new treatment for metastatic ovarian cancer.

Vaccinia virus preferentially infects and controls human and murine ovarian tumors in mice

Vaccinia virus has been shown to efficiently infect tumor cells. Therefore, vaccinia virus represents a potentially safe and effective antitumor agent against ovarian cancer. Here, we assessed the ability of vaccinia virus to preferentially infect and control both human and murine ovarian tumors in vivo. We used the non-invasive luminescence imaging system to monitor the infection and suppression of ovarian tumors by vaccinia in live mice. Our data indicated that vaccinia was able to effectively infect and kill both human and murine ovarian tumors. Vaccinia virus administered to mice intraperitoneally was specifically targeted to the murine or human ovarian tumors and led to antitumor responses. These findings suggest that vaccinia virus is capable of selectively targeting and controlling ovarian tumors. Thus, intraperitoneal injection with vaccinia virus may provide a potentially effective strategy for treating advanced-stage ovarian cancers.

Virus-specific and bystander CD8 T cells recruited during virus-induced encephalomyelitis

Neurotropic coronavirus-induced encephalitis was used to evaluate recruitment, functional activation, and retention of peripheral bystander memory CD8+ T cells. Mice were first infected with recombinant vaccinia virus expressing a non-cross-reactive human immunodeficiency virus (HIV) epitope, designated p18. Following establishment of an endogenous p18-specific memory CD8+ T-cell population, mice were challenged with coronavirus to directly compare recruitment, longevity, and activation characteristics of both primary coronavirus-specific and bystander memory populations trafficking into the central nervous system (CNS). HIV-specific memory CD8+ T cells were recruited early into the CNS as components of the innate immune response, preceding CD8+ T cells specific for the dominant coronavirus epitope, designated pN. Although pN-specific T-cell numbers gradually exceeded bystander p18-specific CD8+ T-cell numbers, both populations peaked concurrently within the CNS. Nevertheless, coronavirus-specific CD8+ T cells were preferentially retained. By contrast, bystander CD8+ T-cell numbers declined to background numbers following control of CNS virus replication. Furthermore, in contrast to highly activated pN-specific CD8+ T cells, bystander p18-specific CD8+ T cells recruited to the site of inflammation maintained a nonactivated memory phenotype and did not express ex vivo cytolytic activity. Therefore, analysis of host CD8+ T-cell responses to unrelated infections demonstrates that bystander memory CD8+ T cells can comprise a significant proportion of CNS inflammatory cells during virus-induced encephalitis. However, transient CNS retention and the absence of activation suggest that memory bystander CD8+ T cells may not overtly contribute to pathology in the absence of antigen recognition.

TLR activation synergizes with Kilham rat virus infection to induce diabetes in BBDR rats

Virus infection is hypothesized to be an important environmental "trigger" of type 1 diabetes in humans. We used the BBDR rat model to investigate the relationship between viral infection and autoimmune diabetes. BBDR rats are diabetes-free in viral Ab-free housing, but the disease develops in approximately 30% of BBDR rats infected with Kilham rat virus (KRV) through a process that does not involve infection of pancreatic beta cells. Pretreatment with polyinosinic-polycytidylic (poly(I:C)), a ligand of TLR3, acts synergistically to induce diabetes in 100% of KRV-infected rats. The mechanisms by which KRV induces diabetes and TLR3 ligation facilitates this process are not clear. In this study, we demonstrate that activation of the innate immune system plays a crucial role in diabetes induction. We report that multiple TLR agonists synergize with KRV infection to induce diabetes in BBDR rats, as do heat-killed Escherichia coli or Staphylococcus aureus (natural TLR agonists). KRV infection increases serum IL-12 p40 in a strain-specific manner, and increases IL-12 p40, IFN-gamma-inducible protein-10, and IFN-gamma mRNA transcript levels, particularly in the pancreatic lymph nodes of BBDR rats. Infection with vaccinia virus or H-1 parvovirus induced less stimulation of the innate immune system and failed to induce diabetes in BBDR rats. Our results suggest that the degree to which the innate immune system is activated by TLRs is important for expression of virus-induced diabetes in genetically susceptible hosts.

Vaccinia virus infection during murine pregnancy: a new pathogenesis model for vaccinia fetalis

Vaccinia fetalis, the vertical transfer of vaccinia virus from mother to fetus, is a relatively rare but often fatal complication of primary vaccinia virus vaccination during pregnancy. To date there has been no attempt to develop an animal model to study the pathogenesis of this acute viral infection in vivo. Here we report that infection of gestating BALB/c mice by either intravenous or intraperitoneal routes with the Western Reserve strain of vaccinia virus results in the rapid colonization of the placenta and vertical transfer of virus to the developing fetus. Systemic maternal infections during gestation lead to the death of all offspring prior to or very shortly after birth. Using in situ hybridization for vaccinia virus mRNA to identify infected cells, we show that the virus initially colonizes cells lining maternal lacunae within the trophospongium layer of the placenta. The study of this model will significantly enhance our understanding of the pathogenesis of fetal vaccinia virus infections and aid in the development of effective treatments designed to reduce the risk of vaccinia virus-associated complications during pregnancy.

Evaluation of a recombinant Listeria monocytogenes expressing an HIV protein that protects mice against viral challenge

Vaccine strategies that utilize cell mediated immunity to control infection will be a necessary component of human immunodeficiency virus (HIV) vaccines. In previous studies we have shown that a Listeria monocytogenes recombinant expressing HIV-Gag elicits strong CD8+ and CD4+ T cell responses against HIV Gag in addition to its own secreted proteins. Here, we show that Lm-Gag can protect mice against a viral challenge with a recombinant vaccinia virus expressing Gag, in an antigen specific manner, and that this protection is T cell mediated. These results further support the use of L. monocytogenes as a vaccine approach for HIV through the induction of T cell immunity.

Insertion sites for recombinant vaccinia virus construction: effects on expression of a foreign protein

The expression of antigens or other molecules from recombinant vaccinia viruses requires the insertion of coding sequence at specific sites in the viral genome. Here we investigate the influence of two different sites on the level of protein expressed during a viral infection. The level of immune response in mice to vaccinia virus-expressed murine interleukin 2 (IL-2) or IL-4 varied depending on whether the coding sequence was inserted into the vaccinia virus thymidine kinase (tk) gene or into the HindIII F fragment of the viral genome where herpes simplex virus (HSV) tk was used as a selectable marker. In each case the intensity of the response was greater when the relevant gene was expressed from the HindIII F insertion site. In order to quantify these differences a series of recombinant viruses expressing luciferase was constructed. Luciferase activity from coding sequence inserted into the HindIII F fragment was significantly higher than that from the tk gene insertion, provided HSV tk(+) constructs were compared. Insertion of a marker gene (HSV tk) into the HindIII F site with disruption of the F7L open reading frame led to a reduced level of luciferase expressed from the tk insert, despite more than 45 kb of intervening sequence. In mice, luciferase expression was higher from the HindIII F inserted gene than from the tk insert in both lungs and ovaries.

IL-12 Delivery from Recombinant Vaccinia Virus Attenuates the Vector and Enhances the Cellular Immune Response Against HIV-1 Env in a Dose-Dependent Manner

To develop vaccination strategies against HIV-1 infection aimed to specifically enhance the cell-mediated immunity (CMI), we have engineered vaccinia virus (VV) recombinants expressing HIV-1 Env (rVVenv) and murine IL-12 (rVVlucIL-12) genes or coexpressing both genes (rVVenvIL-12). In mice inoculated with rVVlucIL-12 there is a rapid clearance of the virus, and this correlates with the induction of high levels of IL-12 and IFN-γ in serum and spleen early after infection. Enzyme-linked immunospot analysis of mice inoculated with rVVlucIL-12, revealed a nearly 2-fold increase in the number of specific anti-VV CD8+ T cells compared with that in mice given control rVV, and the serum Ab response was biased in favor of a Th1 response. An enhancement of about 2-fold in the number of anti-gp160 IFN-γ-secreting CD8+ T cells was observed in mice inoculated with rVVenvIL-12, when a dose of 1 × 107 PFU/mouse was used, but this enhancement was not observed when mice were given 5 × 107 PFU. This variation with virus dosage was confirmed in mice immunized simultaneously with different multiplicities of rVV expressing singly the env or IL-12 genes. The highest specific CMI was obtained in mice coadministered a low dose (2 × 104 PFU) of rVVlucIL-12 and 1 × 107 PFU of rVVenv. Our findings provide evidence for specific enhancement of the CMI to HIV-1 Env by the differential expression of IL-12 and env genes delivered from VV recombinants. This approach can be of wide vaccination interest as a means to improve immune responses to other Ags.

Recombinant vaccinia virus coexpressing the F protein of respiratory syncytial virus (RSV) and interleukin-4 (IL-4) does not inhibit the development of RSV-specific memory cytotoxic T lymphocytes, whereas priming is diminished in the presence of high levels of IL-2 or gamma interferon

In order to investigate if immune responses to the fusion (F) protein of respiratory syncytial virus (RSV) could be influenced by cytokines, recombinant vaccinia viruses (rVV) carrying both the F gene of RSV and the gene for murine interleukin-2 (IL-2), IL-4, or gamma interferon (IFN-gamma) were constructed. In vitro characterization of rVV revealed that insertion of the cytokine gene into the VP37 locus of the vaccinia virus genome resulted in 100- to 1,000-fold higher expression than insertion of the same gene into the thymidine kinase (TK) locus. In comparison, only a two- to fivefold difference in the level of expression of the F protein was observed when the gene was inserted into either of these two loci. Mice vaccinated with rVV expressing the F protein and high levels of IL-2 or IFN-gamma cleared rVV more rapidly than mice inoculated with a control rVV and developed only low levels of RSV-specific serum antibody. In addition, these recombinants were much less effective at priming RSV-specific memory cytotoxic T lymphocytes (CTL) and IFN-gamma production by spleen cells than rVV expressing the F protein alone. In contrast, mice vaccinated with rVV expressing high levels of IL-4 showed signs of delayed rVV clearance. RSV-specific serum antibody responses were biased in favor of immunoglobulin G1 (IgG1) in these mice, as there was a significant reduction in IgG2a antibody responses compared with serum antibody responses in mice vaccinated with rVV expressing the F protein alone. However, vaccination with rVV expressing the F protein together with high levels of IL-4 did not alter the development of RSV-specific memory CTL or IFN-gamma production by RSV-restimulated splenocytes.

In vivo delivery of interleukin-4 by a recombinant vaccinia virus prevents tumor development in mice

To study the immunotherapeutic potential of interleukin-4 (IL-4) delivered in vivo via a recombinant vaccinia virus, a thymidine kinase-negative (TK-) vaccinia virus that expressed the murine IL-4 gene (VV1/IL-4) was constructed. When mice were inoculated with 10(7) plaque-forming units (pfu) of VV1/IL-4 subcutaneously (s.c.), 10(5) pfu/cm2 were found in skin, and smaller numbers in liver and kidney between 1 and 7 days after infection; few viral pfu were found in spleen and lung, or in any organ after intravenous infection. This suggested that recombinant vaccinia viruses might be most efficient at delivery of cytokine genes to the skin. Because IL-4 has recently been found to have potent anti-tumor activity, the effect of recombinant virus infection on the development of s.c. tumors was studied. A single s.c. inoculation with VV1/IL-4 delayed the development of NCTC 2472 tumors, but when VV1/IL-4 was inoculated s.c. weekly for 8 weeks, tumor development was completely prevented in 93% of mice. Similarly, the development of M-3 melanoma tumors was also prevented by weekly s.c. inoculations of VV1/IL-4. About 40% of mice treated with control VV2/beta gal by the same regimen also failed to develop tumors. Weekly virus treatment did not prevent NCTC 2472 tumor development in athymic nu/nu mice, suggesting that mature T cells are required for expression of VV1/IL-4 induced antitumor activity. Thus, recombinant vaccinia viruses may be especially well suited for convenient therapeutic delivery of immunomodulator genes to skin-related sites.

Biological effects of recombinant vaccinia virus-expressed interleukin 4

Recombinant vaccinia viruses expressing murine interleukin 4 (IL-4), either alone or together with interleukin 2 (IL-2) or gamma interferon (gamma-IFN), were constructed. Unlike IL-2, IL-4 expressing viruses were not cleared from immunodeficient mice and the mice died. As they died more rapidly than immunodeficient mice inoculated with a control virus, it appeared that IL-4 contributed to their death and the IL-4 mediated toxicity was confirmed in normal immunocompetent mice. The toxicity was reversed by co-expression of either IL-2 or gamma-IFN, probably due to virus clearance and therefore lower levels of circulating IL-4. Vaccinia virus-expressed IL-4 did not increase antibody or natural killer cell levels and caused a slight decrease in cytotoxic T lymphocyte levels.

Vaccinia-rotavirus VP7 recombinants protect mice against rotavirus-induced diarrhoea

Recombinant vaccinia viruses expressing wild type intracellular VP7 (VP7wt) from rotavirus SA11 or VP7sc, a cell surface-anchored variant, boosted antibody titres in SA11-immune mice. Pups born to these mice were protected from diarrhoea following challenge with SA11. In rotavirus-naive mice, two immunizations with recombinant vaccinia virus expressing VP7sc stimulated protective immunity that could be transferred to pups, whereas viruses expressing VP7wt did not stimulate protective immunity. Recombinant vaccinia viruses expressing intracellular or cell surface-anchored VP6, the rotavirus group-reactive antigen from the inner capsid, did not stimulate protective immunity. These experiments demonstrate that a live viral vector expressing cell surface anchored VP7 may represent a strategy for the development of safe, effective vaccines against rotavirus-induced diarrhoea.

Anti-asialo-GM1 inhibits vaccinia virus infection of murine ovaries: asialo-GM1 as an additional virus receptor?

The neurovirulent strain of vaccinia virus, VV-WR, or recombinants derived from VV-WR, cause highly productive infection of murine ovaries, but infection could be partially inhibited in vivo using an antiserum to asialo-GM1 (as-GM1). In vitro analysis by flow cytometry revealed that murine ovarian cells expressed a cell surface antigen identical to or cross-reactive with as-GM1. The capacity of VV-WR to infect murine ovaries appears to depend in part upon as-GM1 expression on ovarian cells.