Samar Ojaimi

Eliminating hepatitis B by antagonizing cellular inhibitors of apoptosis

Significance Current antiviral treatments for chronic hepatitis B virus (HBV) infection are effective in suppressing production of virus, but they have poor efficacy in promoting the elimination of infection. Hence, most patients with chronic HBV infection are maintained on antiviral therapies indefinitely. There is much interest in identifying treatments that promote the clearance of infected hepatocytes, thus purging the HBV DNA reservoir in the liver. Here, we show that the clinical-stage drug birinapant, which antagonizes host cell inhibitor of apoptosis proteins (cIAPs), preferentially promotes the killing of HBV-infected hepatocytes in a mouse model of HBV. Therefore, birinapant and other antagonists of cIAPs may be efficacious in the treatment of chronic HBV infection and may promote elimination of virus. We have shown that cellular inhibitor of apoptosis proteins (cIAPs) impair clearance of hepatitis B virus (HBV) infection by preventing TNF-mediated killing/death of infected cells. A key question, with profound therapeutic implications, is whether this finding can be translated to the development of drugs that promote elimination of infected cells. Drug inhibitors of cIAPs were developed as cancer therapeutics to promote TNF-mediated tumor killing. These drugs are also known as Smac mimetics, because they mimic the action of the endogenous protein Smac/Diablo that antagonizes cIAP function. Here, we show using an immunocompetent mouse model of chronic HBV infection that birinapant and other Smac mimetics are able to rapidly reduce serum HBV DNA and serum HBV surface antigen, and they promote the elimination of hepatocytes containing HBV core antigen. The efficacy of Smac mimetics in treating HBV infection is dependent on their chemistry, host CD4+ T cells, and TNF. Birinapant enhances the ability of entecavir, an antiviral nucleoside analog, to reduce viral DNA production in HBV-infected animals. These results indicate that birinapant and other Smac mimetics may have efficacy in treating HBV infection and perhaps, other intracellular infections.

Cellular inhibitor of apoptosis proteins prevent clearance of hepatitis B virus

Significance Hepatitis B virus (HBV) causes substantial morbidity and mortality. A large proportion of infected individuals controls infection but does not completely eradicate HBV DNA from the liver, and flares in hepatitis can be precipitated by immunosuppression. A proportion of individuals never controls infection, and these people are at substantial risk of developing liver failure and liver cancer. Current therapies are not effective at eliminating virus, and there is a major interest in developing functional cures for HBV infection. We identified host cell signaling molecules that can restrict the ability to eradicate infected cells. These molecules can be therapeutically targeted, and drugs that interfere with the function of these host cell proteins may be useful therapies to promote clearance of HBV infection. Hepatitis B virus (HBV) infection can result in a spectrum of outcomes from immune-mediated control to disease progression, cirrhosis, and liver cancer. The host molecular pathways that influence and contribute to these outcomes need to be defined. Using an immunocompetent mouse model of chronic HBV infection, we identified some of the host cellular and molecular factors that impact on infection outcomes. Here, we show that cellular inhibitor of apoptosis proteins (cIAPs) attenuate TNF signaling during hepatitis B infection, and they restrict the death of infected hepatocytes, thus allowing viral persistence. Animals with a liver-specific cIAP1 and total cIAP2 deficiency efficiently control HBV infection compared with WT mice. This phenotype was partly recapitulated in mice that were deficient in cIAP2 alone. These results indicate that antagonizing the function of cIAPs may promote the clearance of HBV infection.

Quadrivalent Human Papillomavirus recombinant vaccine associated lipoatrophy.

Involutional lipoatrophy, a loss of subcutaneous fat, may be idiopathic, associated with inflammatory skin conditions, or trauma, and has also been reported following injections of medications including insulin, corticosteroids and penicillin. There have also been reports in association with Diptheria Pertussis Tetanus (DPT) vaccine. We report on two cases of lipoatrophy associated with the new Quadrivalent Human Papillomavirus (HPV) recombinant vaccine (Gardasil).

Curtobacterium flaccumfaciens septic arthritis following puncture with a Coxspur Hawthorn thorn.

ABSTRACT Curtobacterium species are recognized plant pathogens. We report the first well-documented case of Curtobacterium human infection, a child with septic arthritis following puncture with a Coxspur Hawthorn plant thorn. The organism isolated from synovial tissue and the plant thorn was identified as Curtobacterium flaccumfaciens by 16S rRNA gene sequence analysis.

Successful carboplatin desensitization by using omalizumab and paradoxical diminution of total IgE levels

Carboplatin is an important chemotherapeutic agent that is frequently used in the management of ovarian cancer. Hypersensitivity reactions, which occur in up to 20% of patients, with reactions typically coinciding with reintroduction of the drug after relapse, however, can limit its use. Successful desensitization has been achieved by using premedication and slow, graded infusion of carboplatin over periods that vary from a few hours to a few days. In our institution, we historically used a 4-day protocol but subsequently found that a 2-day infusion was equally safe and more convenient. However, our first failure prompted us to explore the addition of omalizumab. In May 2011, a 63-year-old woman who was nonatopic was diagnosed with a serous adenocarcinoma of ovarian origin. Due to extensive peritoneal disease, debulking surgery was followed by 6 cycles of paclitaxel and carboplatin without event. Despite an initial response, local recurrence and hepatic metastases developed within 3 months of the completion of chemotherapy, and she was recommenced on a course of carboplatin, on this occasion with gemcitabine. Within hours of completing her first carboplatin dose (seventh exposure, 450 mg), she developed transient itchiness of her hands and feet, and the next dose, 3 weeks later (eighth exposure), was complicated by itchy erythroderma and hypotension, which commenced soon after initiation of the infusion. An intradermal skin test, performed 2 weeks after her reaction, was strongly positive (Table I), and desensitization was planned. Although some groups advocate the use of a 6-hour protocol, there is a significant rate of recurrent anaphylaxis when the drug is infused over this short time period, hence it has been our policy to follow a 2-day desensitization regimen. We had seen no recurrent reactions in the first 12 consecutive patients nor subsequently, until May 2012, when the above patient failed this regimen and developed generalized urticaria and, 3 weeks later, developed the same reaction while receiving the 4-day protocol. Given the extreme sensitivity of this patient to carboplatin and the strong evidence for IgE-mediated pathophysiology in carboplatin allergy, we considered the use of omalizumab, a recombinant humanized monoclonal antibody, which binds to the FceR binding domain of soluble IgE and blocks the interaction with its receptors on mast cells and basophils. Based on reports of its use in the treatment of other IgE-mediated allergic disorders and in the prophylaxis of systemic reactions during desensitization to aeroallergens and bee venom, we devised the protocol depicted in Figure 1. After consent, the patient was commenced on a series of 9 fortnightly doses of 300 mg of omalizumab given subcutaneously. Immediately after the third omalizumab dose, carboplatin was administered over 4 days, along with the usual premedications (Figure 1) and was tolerated without event. A further 4 cycles of carboplatin, in conjunction with liposomal doxorubicin at 40 mg/m, were administered under these conditions without reaction. Skin testing became negative at the completion of desensitization (Table I), as has previously been reported in other patients who received this protocol. Cancer antigen 125 levels responded appropriately, which confirmed a tumor response (Figure 1), whereas serum mast cell tryptase levels, performed immediately after completion of each carboplatin infusion, remained within the normal range. Intriguingly, total IgE levels fell during the desensitization period (Figure 1). This was unexpected, because omalizumab usually causes an elevation of total IgE levels due to slower clearance of the omalizumab-IgE complexes in comparison with free, unbound, IgE. Although such an increase was indeed initially observed over the first 6 weeks of omalizumab therapy (Figure 1), thereafter levels steadily fell to eventually lie within the normal range. Taken together with the development of skin test negativity at the end of the treatment period (Table I), we speculate that much of the total serum IgE in this patient may have been specific for carboplatin and that graduated carboplatin exposure itself resulted in clearing of the IgE, thereby resulting in reduction of total IgE levels. If true, this method of desensitization contrasts with traditional subcutaneous or sublingual immunotherapy, in whichmultiple immunemechanisms appear to be involved and an effect on specific and total IgE levels is much less apparent. Such a contention could have been supported by an in vitro assay for specific IgE to carboplatin, by solid phase or basophil release assay but ismethodologically difficult given the small molecular, haptenic nature of this allergen, and remains the subject of ongoing research. In any case, the efficacy of omalizumab in this patient provides additional supportive evidence for a type I, IgEmediated mechanism for carboplatin allergy. This is one of very few reported cases of the use of omalizumab to overcome IgE-mediated drug allergy, the only published case to our knowledge being for desensitization to insulin. For carboplatin desensitization, omalizumab may have a role in the patient who is exquisitely allergic and who fails standard desensitization protocols and, indeed, may help simplify or shorten such protocols in patients with lesser degrees of carboplatin

Necroptotic signaling is primed in Mycobacterium tuberculosis -infected macrophages, but its pathophysiological consequence in disease is restricted

Mixed lineage kinase domain-like (MLKL)-dependent necroptosis is thought to be implicated in the death of mycobacteria-infected macrophages, reportedly allowing escape and dissemination of the microorganism. Given the consequent interest in developing inhibitors of necroptosis to treat Mycobacterium tuberculosis (Mtb) infection, we used human pharmacologic and murine genetic models to definitively establish the pathophysiological role of necroptosis in Mtb infection. We observed that Mtb infection of macrophages remodeled the intracellular signaling landscape by upregulating MLKL, TNFR1, and ZBP1, whilst downregulating cIAP1, thereby establishing a strong pro-necroptotic milieu. However, blocking necroptosis either by deleting Mlkl or inhibiting RIPK1 had no effect on the survival of infected human or murine macrophages. Consistent with this, MLKL-deficiency or treatment of humanized mice with the RIPK1 inhibitor Nec-1s did not impact on disease outcomes in vivo, with mice displaying lung histopathology and bacterial burdens indistinguishable from controls. Therefore, although the necroptotic pathway is primed by Mtb infection, macrophage necroptosis is ultimately restricted to mitigate disease pathogenesis. We identified cFLIP upregulation that may promote caspase 8-mediated degradation of CYLD, and other necrosome components, as a possible mechanism abrogating Mtb’s capacity to coopt necroptotic signaling. Variability in the capacity of these mechanisms to interfere with necroptosis may influence disease severity and could explain the heterogeneity of Mtb infection and disease.

The two-edged sword: vasculitis associated with HIV and hepatitis C coinfection

Vasculitis has long been associated with chronic viral infections, thus the twin perils of the infection and the immune response against it that bedevils the specialties of infection and immunity. After HIV was identified, it too became associated with vasculitic syndromes. Later, hepatitis C virus was also isolated, identified and described with its own spectrum of vasculitic diseases, including hepatitis C virus-associated cryoglobulinaemia. With the increasing prevalence of HIV and hepatitis C virus coinfection, there has come an increasing recognition of the range of vasculitides that can occur in this population leading to significant morbidity, diagnostic and treatment challenges. In this review, we examine the epidemiology, pathogenesis and general principles of treatment of these systemic diseases in HIV/hepatitis C virus coinfected individuals.

Treatment outcomes in a cohort of patients with mucosal-predominant pemphigus vulgaris

Pemphigus vulgaris (PV) is a rare autoimmune blistering condition. Treatment typically combines corticosteroids with another immunosuppressive agent, such as azathioprine, mycophenolate mofetil (MMF) or rituximab.

Is Receptor-Interacting Protein Kinase 3 a Viable Therapeutic Target for Mycobacterium tuberculosis Infection?

The dwindling list of antimicrobial agents exhibiting broad efficacy against clinical strains of Mycobacterium tuberculosis (Mtb) has forced the medical community to redefine current approaches to the treatment of tuberculosis (TB). Host receptor-interacting protein kinase 3 (RIPK3) has been flagged recently as a potential target, given that it is believed to regulate necroptosis-independent signaling pathways, which have been implicated in exacerbating several inflammatory conditions and which reportedly play a role in the necrosis of Mtb-infected macrophages. To examine the therapeutic potential of inhibiting RIPK3, we infected RIPK3-deficient mice with aerosolized Mtb. We found that the loss of RIPK3 did not alter overall disease outcomes, with deficient animals harboring similar bacterial numbers in the lungs and spleens compared to their wild-type counterparts. Mtb-infected macrophages were not rescued from dying by Ripk3 deletion, nor did this affect production of the pro-inflammatory cytokine IL-1β, both in vitro and in vivo. Infiltration of immune cells into the lungs, as well as the activation of adaptive immunity, similarly was not overtly affected by the loss of RIPK3 signaling. Collectively, our data argue against a role of RIPK3 in mediating pathological inflammation or macrophage necrosis during Mtb disease pathogenesis and thus suggest that this host protein is unlikely to be an attractive therapeutic target for TB.

Impact of a spleen registry on optimal post-splenectomy vaccination and care

ABSTRACT Objective: To evaluate quality of patient knowledge and rates of adherence to guidelines amongst splenectomised patients registered to the Spleen Australia registry. Method: Registrants recruited for assessment of residual splenic function post-splenectomy also underwent an assessment of quality of knowledge and a review of their long-term management. Eligible patients were ≥ 18 years of age, registered to the Spleen Australia clinical registry and had been splenectomised at least 1 year prior to their visit. Quality of knowledge was assessed using a validated questionnaire used in similar studies. Receipt of immunisations was validated by record review. Chemoprophylaxis use was self-reported by patients. Adherence was evaluated using Australian guidelines. Results: 77 patients were evaluated for education and adherence. 58% were female, mean age was 58 years, and median duration since splenectomy was 14 years. Most common indications for splenectomy were trauma and haematological conditions. 77% had good knowledge of key educational points to reduce chances of infection. Adherence to immunisations varied with poor adherence to vaccines introduced after 2010. Only 6 patients were adherent to all recommended immunisations. Increasing duration since registration was associated with poorer 13vPCV (p = 0.008) and 4vMenCV adherence (p = 0.001). Over 70% either currently or had previously used daily chemoprophylaxis and 66% had a supply of emergency antibiotics. Conclusions: Although registrants are receiving initial and booster vaccinations, they do not receive newly recommended vaccines. In order to maintain long-term adherence, we recommend streamlining health information systems, improving awareness strategies and improving financial access to vaccinations in the community with additional awareness of the activities of the registry.