The role of vascular endothelial growth factor A in physiological and pathological angiogenesis

Vascular endothelial growth factor A (VEGF-A) is a major contributor to physiological and pathological angiogenesis in the body. VEGF-A exists as several isoforms varying significantly in their function and angiogenic potential due to their different exon compositions. VEGF111, the most recently discovered isoform, has unique characteristics, being the only isoform resistant to proteolytic cleavage by plasmin and is also freely diffusable. This thesis aimed to investigate the role and regulation of these isoforms in three major conditions, ovarian hyperstimulation (OH), endometriosis, and tumour invasion metastasis. There are currently limited studies available analysing the expression of VEGF-A isoforms in these conditions and how this may impact angiogenesis. This is especially true for VEGF111 where research is greatly limited, and until now, it has not been identified in any human tissue. Thus, we hypothesised that the expression of VEGF111 and the other VEGF-A isoforms may be upregulated and/or disturbed in these conditions and contribute to their progression. This study aimed to advance our current understanding behind VEGF111 mediated angiogenesis and determine if VEGF111 plays a significant role in human disease. While VEGF111 is present in the rat uterus, during early pregnancy its levels fall below the limit of detection of conventional qPCR assays. But, analysis of the more common isoforms revealed the downregulation of VEGF188 specifically at the time of uterine receptivity following OH procedures in the rat. This downregulation was also associated with abnormal and enlarged vessels in the OH uterus at this time. Our studies on the human endometrium were more promising and for the first time we have identified the natural expression of VEGF111 in human tissue, specifically within the human endometrium. Furthermore, we showed that these levels of VEGF111, as well as the other VEGF-A isoforms, are upregulated during menstruation in women with endometriosis, highlighting the importance of specifically studying the menstrual phase in endometriosis. To investigate the angiogenic effects of VEGF111 we analysed the effects of VEGF-A isoforms in a three-dimensional cell culture model and confirmed that VEGF111 is highly angiogenic compared to the better known isoforms VEGF121 and VEGF165

Herpes Simplex Virus Type 1 Interactions with the Interferon System

The interferon (IFN) system is one of the first lines of defense activated against invading viral pathogens. Upon secretion, IFNs activate a signaling cascade resulting in the production of several interferon stimulated genes (ISGs), which work to limit viral replication and establish an overall anti-viral state. Herpes simplex virus type 1 is a ubiquitous human pathogen that has evolved to downregulate the IFN response and establish lifelong latent infection in sensory neurons of the host. This review will focus on the mechanisms by which the host innate immune system detects invading HSV-1 virions, the subsequent IFN response generated to limit viral infection, and the evasion strategies developed by HSV-1 to evade the immune system and establish latency in the host

Interferon inhibits the release of herpes simplex virus-1 from the axons of sensory neurons

ABSTRACT Herpes simplex virus-1 (HSV-1) has evolved mechanisms to evade the host immune system and limit the antiviral effects induced by interferon (IFN) produced by local epithelial and immune cells. In this study, we determined the effects of type I, II, and III IFNs on HSV-1 release from sensory axons. Using compartmentalized microfluidic devices separating axons from the neuronal cell bodies, we showed that treating axons with type I (IFNα and IFNβ), type II (IFNγ), and type III (IFNλ) IFNs inhibited the release of HSV-1 from axons, without altering the anterograde axonal transport of viral components. Furthermore, we showed that only type II IFN induced a cell-wide response following axonal treatment, with phosphorylated STAT1 and STAT3 present along axons and in the neuronal cell body, whereas type I and III IFNs only induced a local STAT1 and STAT3 response in axons. We also showed that HSV-1 infection alone, in the absence of exogenous IFN, activated STAT1 and STAT3 in both neuronal cell bodies and along axons. However, HSV-1 infection restricted the translocation of pSTAT1 and pSTAT3 to the nucleus even in the presence of IFNs, suggesting viral evasion mechanisms are involved in limiting the IFN response in the neuronal cell body. Overall, our study indicates a key and greater antiviral role of IFNs in inhibiting HSV-1 release from axon termini than in the ganglia during recurrent infections and identifies a novel intervention site, the neuro-epidermal junction, for the development of new immunotherapies. IMPORTANCE Herpes simplex virus-1 (HSV-1) is a human pathogen known to cause cold sores and genital herpes. HSV-1 establishes lifelong infections in our sensory neurons, with no cure or vaccine available. HSV-1 can reactivate sporadically and travel back along sensory nerves, where it can form lesions in the oral and genital mucosa, eye, and skin, or be shed asymptomatically. New treatment options are needed as resistance is emerging to current antiviral therapies. Here, we show that interferons (IFNs) are capable of blocking virus release from nerve endings, potentially stopping HSV-1 transmission into the skin. Furthermore, we show that IFNγ has the potential to have widespread antiviral effects in the neuron and may have additional effects on HSV-1 reactivation. Together, this study identifies new targets for the development of immunotherapies to stop the spread of HSV-1 from the nerves into the skin

Herpes Simplex Virus type 1 infects Langerhans cells and the novel epidermal dendritic cell, Epi-cDC2s, via different entry pathways.

Skin mononuclear phagocytes (MNPs) provide the first interactions of invading viruses with the immune system. In addition to Langerhans cells (LCs), we recently described a second epidermal MNP population, Epi-cDC2s, in human anogenital epidermis that is closely related to dermal conventional dendritic cells type 2 (cDC2) and can be preferentially infected by HIV. Here we show that in epidermal explants topically infected with herpes simplex virus (HSV-1), both LCs and Epi-cDC2s interact with HSV-1 particles and infected keratinocytes. Isolated Epi-cDC2s support higher levels of infection than LCs in vitro, inhibited by acyclovir, but both MNP subtypes express similar levels of the HSV entry receptors nectin-1 and HVEM, and show similar levels of initial uptake. Using inhibitors of endosomal acidification, actin and cholesterol, we found that HSV-1 utilises different entry pathways in each cell type. HSV-1 predominantly infects LCs, and monocyte-derived MNPs, via a pH-dependent pathway. In contrast, Epi-cDC2s are mainly infected via a pH-independent pathway which may contribute to the enhanced infection of Epi-cDC2s. Both cells underwent apoptosis suggesting that Epi-cDC2s may follow the same dermal migration and uptake by dermal MNPs that we have previously shown for LCs. Thus, we hypothesize that the uptake of HSV and infection of Epi-cDC2s will stimulate immune responses via a different pathway to LCs, which in future may help guide HSV vaccine development and adjuvant targeting