Our previous demonstration of the potential for host response based

Our previous demonstration of the potential for host response-based pre-symptomatic detection of H3N2 infection using blood RNA myeloperoxidase (McClain et al., 2016) raises the intriguing possibility that an NPL protein host response assay might be useful in early detection of ARV infection, and should be evaluated. The availability of a proteomic ‘signature’ that accurately classifies ARV infection and might be migrated to simple and inexpensive antibody-based tests that are routinely used in both clinical laboratory and over-the-counter diagnostic applications represents an important advance, and may one day yield a ARV host response test that is safe, simple, rapid, inexpensive, and accurate.

Support for this work was provided by the U.S. Defense Advanced Research Projects Agency (DARPA) through contract N66001-07-C-2024. E.L.T. and M.T.M. were supported by award numbers 1IK2CX000530 and 1IK2CX000611, respectively, from the Clinical Science Research and Development Service of the VA Office of Research and Development. The funders had no role in the preparation of this manuscript.

Conflict of Interest

Author Contributions


Influenza A virus possesses eight segmented, negative-sense viral RNAs (vRNAs) as its genome. Two of these vRNAs encode hemagglutinin (HA) and neuraminidase (NA), which are major viral antigenic proteins on the virus particle. The trimeric type I transmembrane glycoprotein HA is classified into 18 subtypes (H1 to H18) that can be combined into two separate phylogenetic groups: group 1 encompasses H1, H2, H5, H6, H8, H9, H11, H12, H13, H16, H17, and H18, whereas group 2 includes H3, H4, H7, H10, H14, and H15 (Gamblin and Skehel, 2010; Tong et al., 2013; Webster et al., 1992). HA is produced as HA0, which is then cleaved into HA1 and HA2. The HA1-HA2 monomer assembles as trimers consisting of an apical globular head, which is derived from the central region of HA1, and a stem region, which consists of HA2 and the N- and C-terminus of HA1 (Wilson et al., 1981). The globular head and stem regions are involved in receptor binding and membrane fusion, respectively. Antibodies against the highly antigenic region around the receptor-binding site on the globular head ordinarily inhibit receptor binding steps, and therefore virus infectivity is neutralized (Caton et al., 1982). Because of the high immunological pressure imposed by these antibodies, the antigenicity of the globular head varies by accumulating mutations that allow escape from recognition by these antibodies. In contrast, a limited number of antibodies against the HA stem are present in ordinary human sera because the HA stem is not highly immunogenic under normal circumstances (Sui et al., 2011), and is, in fact, highly conserved among heterotypic HAs. The antibodies against the HA stem typically neutralize virus by inhibiting membrane fusion steps (Brandenburg et al., 2013). The vast majority of anti-HA globular head antibodies are strain or subtype-specific, whereas many anti-HA stem antibodies recognize several subtypes of HA. Therefore, antibodies against the HA stem are highly desired as a novel antiviral therapy and a target for a universal vaccine.
Known human monoclonal antibodies against the heterotypic HA stem are classified into 3 types based on their reactivity. The first type recognizes several subtypes of HA that belong to group 1; CR6261 (Ekiert et al., 2009; Throsby et al., 2008), F10 (Sui et al., 2009), 3.1 (Wyrzucki et al., 2014), FE43, FE17 (Corti et al., 2010), PN-SIA49 (De Marco et al., 2012), and A06 (Kashyap et al., 2010) are member of this type. The second type of antibodies includes CR8020 (Ekiert et al., 2011), and CR8043 (Friesen et al., 2014), which react with several subtypes of HA belonging to group 2. The third and final type binds to many subtypes of HA belonging to both groups 1 and 2; CR9114 (Dreyfus et al., 2012), FI6v3 (Corti et al., 2011), 39.29, 81.39 (Nakamura et al., 2013), CT149 (Wu et al., 2015), VIS410 (Tharakaraman et al., 2015), 1.12 (Wyrzucki et al., 2015), 1C4, 3C4 (Hu et al., 2013), 05-2G02 (Li et al., 2012), 045-05310-2B06, S6-B01 (Henry Dunand et al., 2015), PN-SIA28 (Clementi et al., 2011), MEDI8852 (Kallewaard et al., 2016), 56.a.09, 31.b.09, 16.a.26, and 31.a.83 (Joyce et al., 2016) belong to this type. CR9114 also reacts with the HA stem of influenza B virus (Dreyfus et al., 2012). Many of these antibodies inhibit viral growth in vitro by predominantly interfering with viral membrane fusion during viral entry. Some of the anti-HA stem antibodies require Fcγ receptor-mediated antibody-dependent cellular cytotoxicity (ADCC) to afford efficient protection in vivo to reduce the number of infected cells (DiLillo et al., 2014; DiLillo et al., 2016; Jegaskanda et al., 2014). Thus, several antibody-dependent inhibitory mechanisms serve to protect against influenza A virus infection in vivo. Therefore, the characterization of inhibitory mechanisms utilized by human antibodies should help in the development of a universal vaccine.

myeloperoxidase A membranaceus Leguminosae is a very well known and

A. membranaceus (Leguminosae) is a very well-known and widely used herbal medicine in China. The dried root of A. membranaceus has a long history of medical use. It is traditionally prepared as a tonic that can improve the functioning of the lungs, adrenal glands, and gastrointestinal tract; increase metabolism; promote healing; and reduce fatigue. The active pharmacological constituents of A. membranaceus include polysaccharides, saponins, flavonoids, l-arginine, and l-canavanine. Astragalus polysaccharides (APS), the primary active extract from A. membranaceus, exert diverse biological effects through regulating immune responses such as cellular and humoral immunity, nonspecific immune functions, and cytokine production. It reduced cell accumulation, swelling, and the arthritic index of the joints and serum levels of inflammatory mediators in adjuvant arthritic rats. The in vivo injection of A. membranaceus suppresses the proliferation and differentiation of autoreactive T-cells by elevating Treg IL-10 and reducing IL-6. Astragalus polysaccharides regulate the effects of Thl/Th2 imbalance and secreted cytokines as well as promote the phenotypic and functional maturation of dendritic cells. In addition to their immunomodulatory and hypoglycemic activities, several studies have revealed that APS can be used for treating inflammatory diseases such as intestinal inflammation and for inhibiting tumor growth and metastasis in nude mice with cancer cell xenografts. Astragalus polysaccharides interestingly reverse multidrug resistance and inhibit P-gp expression in the colon. The combination of APS with conventional Western medicine has clinically been shown to prolong survival in patients with lung cancer.
Some more recent studies have investigated the efficacy of A. membranaceus as a complementary and palliative medicine for treating CRF. PG2 significantly improved CRF in the NS-primed group. In the initial 4-week cycle, APS injection exhibited a higher fatigue-improvement response rate than that observed with NS alone. In addition, approximately 82% of the patients who reported improved fatigue symptoms after the first APS myeloperoxidase experienced sustained benefits after the second treatment cycle. Among the patients treated with APS who did not report any improvement in their symptoms throughout the first treatment cycle, approximately 71% of the patients reported a significant improvement in their symptoms after the second treatment cycle. No major or irreversible toxicities were observed with APS treatment. Thus, APS may be an effective and safe treatment for CRF among patients with advanced cancer.
Tumor metastasis is the primary cause of cancer-related mortality. The inflammatory cells in the tumor microenvironment have a crucial role in tumor growth, progression, and metastasis. Within the tumor stroma, TAMs constitute a pivotal class of inflammatory cells, and compelling evidence suggests that TAMs have a promoting role in various processes such as carcinogenesis, tumor growth, angiogenesis, and lymphangiogenesis, and TAMs are the key regulators of the metastatic phenotype of cancer cells. Tumor-associated macrophages regulate cancer progression and metastases in the tumor microenvironment. Furthermore, TAMs are a crucial component of the leukocyte infiltrate. Tumor-associated macrophage infiltrates are correlated with tumor progression and poor prognosis in patients with lung cancer. In breast cancer, macrophage infiltration is correlated with a poor prognosis. Metastatic breast cancer exhibits poor prognosis with severe mortality, and the available therapeutic options remain limited. In addition, numerous studies have indicated that cancer-related inflammation promotes the development of tumors. Certain proinflammatory cytokines such as IL-8, -6, and TNF-α activate epithelial–mesenchymal transition and eventually facilitate cell invasion and metastasis. However, the activated phenotype and polarization status of TAMs in solid tumors are not completely understood, and the anticancer mechanism of APS and their involvement in the reversal of TAMs remain unclear. Woo et al demonstrated that KSG-002, a new herbal composition of the radices A. membranaceus and Angelica gigas, suppresses breast cancer by inhibiting TAM recruitment. KSG-002 furthermore decreased the infiltrated macrophage numbers in xenograft tumor cohorts, inhibited cell proliferation and migration, and reduced TNF-α production by inhibiting the NF-κB pathway. Based on these findings, we conclude that TCMs can suppress CRF by targeting cancer-related inflammation and inhibiting TAMs.

br Conflicts of interest br Introduction

Conflicts of interest

Childhood nephrotic syndrome (NS) is defined by nephrotic-range proteinuria, generalized edema, hypoalbuminuria, and hyperlipidemia with normal renal function. Idiopathic nephrotic syndrome (INS) is the most frequent renal disease in children. Childhood NS typically follows a relapsing-remitting course, often requiring recurrent courses of myeloperoxidase (GC), but with low systemic inflammation during remission.
Bone mass deposition begins during fetal life and continues during infancy and adolescence, stabilizing at the beginning of adulthood. During childhood and adolescence, skeletal modeling results in sex- and maturation-specific increases in bone density. Metabolic bone disease (MBD) is characterized by changes in skeletal mineralization due to poor bone mineral content (BMC). Children may be especially vulnerable to the effects of GC on bone formation and peak bone mass.
Prednisone is the first-line treatment for INS to induce remission, to prevent relapses and to avoid side effects of the disease. Prolonged administration of prednisone interferes with growth and bone mineralization, and has deleterious effect on basic cellular mechanisms that are important in the development and maintenance of bone strength. Steroids are known to cause osteoporosis and affect BMC and bone mineral density (BMD) in children. Glucocorticoids have a suppressive effect on osteoblastogenesis in the bone marrow and promote the apoptosis of osteoblasts and osteocytes, thus leading to decreased bone formation. There is some evidence to suggest that GC may increase bone resorption by extending the lifespan of pre-existing osteoclasts. Glucocorticoids may also promote calcium loss through the kidneys and gut, and this negative calcium balance can itself lead to increased bone remodeling and osteoclastic activity due to secondary hyperparathyroidism.
Children with INS are at risk for MBD, accompanied by important alterations of mineral and bone metabolism.


Demographic and anthropometric characteristics of the participants with steroid-sensitive nephrotic syndrome (SSNS), steroid-resistant nephrotic syndrome (SRNS), and the control groups are summarized in Table 1. Weight and BMI Z-scores were significantly higher in the SSNS and SRNS patients than the controls, with no significant difference between them regarding the height Z-scores. In terms of serum markers of bone turnover, serum Ca (total and ionized) were significantly lower, while serum phosphorus and alkaline phosphatase were significantly higher in both SSNS and SRNS patients vs. the controls. Bone aches were found in eight patients (32%).
No significant statistical differences were found between SSNS and SRNS patients regarding the drugs received and DXA measurements (Table 2). Seventy-two percent of SSNS patients received immunosuppressive drugs, as follows: 48% were cyclosporine therapy, 4% on Mycophenolate Mofetil, 8% on cyclophosphamide, and 12% on mixed immunosuppressive therapy.
Bone mineral density (BMD) and fracture risk between nephrotic syndrome participants are given in Table 3. Osteopenia was documented by DXA scan in 11 patients (44%) (seven SDNS, four SRNS), and osteoporosis in two patients (8%) (two SDNS). Fracture risk was mild in six patients (24%) (one IFRNS, two SDNS, three SRNS), moderate in two (8%) (one SDNS, one SRNS), and marked in three (12%) (two SDNS, one SRNS).
A significant statistical correlation was observed between BMD Z-scores and age of patients (r=0.43; p<0.05), weight Z-score (r=0.56; p<0.001), height Z-score (r=0.57; p<0.05), BMI (r=0.34; p<0.05), duration (r=−0.46; p<0.05), and cumulative dose of GC therapy(r=−0.88; p<0.001). Linear regression analyses in Table 4 show that the steroid cumulative dose was the only significant independent risk factor.
Although GCs are the treatment of choice for children with idiopathic NS, obesity and bone mineralization side effects should be considered. In this study, the analyses clearly showed an impact of GCs on body weight and BMI in nephrotic syndrome participants. Not surprisingly, the SSNS and SDNS patients had significantly higher weight and BMI Z-scores than the controls, but with insignificant statistical difference between SSNS and SDNS. Similar results were reported by Lestari et al. and Ribeiro et al. in their analyses of obesity in SSNS and SDNS. The use of high-dose and long-term steroids leads to increased food intake and inhibited energy expenditure through stimulation of neuropeptide-Y and inhibited release of corticotrophin hormone. The process triggers an anabolic process and leads to obesity. Hypocalcemia in patients with NS reported in this study was in line with Koşan et al. GCs cause hypocalcemia by decreased Ca adsorption from gut and kidneys.

The mean BWT was mm in all KC patients

The mean BWT was 10.7 ± 3.44 mm in all KC patients, 9.5 ± 3.81 mm in the five KC patients without AE, and 11.5 ± 3.21 mm in the eight KC patients with AE. The mean BWT of the focal thickening was 8.91 ± 2.67 mm in ulcer type IC patients. There was no difference in BWT between the controls and nonulcer type IC patients (p = 1.00). The total BMV was significantly greater in KC patients with AE than in other groups (p < 0.001), but was not significantly different among the control, nonulcer IC, ulcer type IC, and KC patients without AE. Although the BWT in ulcer type IC was thicker than in nonulcer IC, the BMV showed no significant difference between the two IC groups (p = 0.104), indicating that the increased maximal BWT in ulcer type IC was due to focal inflammation at focal Hunner\'s lesion. The BWT in other parts of the myeloperoxidase wall was similar to that in nonulcer IC. Although an increased BMT was also noted in KC without AE, it was likely attributable to a smaller intravesical volume in patients of KC without AE during CT scan.
The bladder wall in patients with nonulcer type IC was homogenously thin without focal thickening or perivesical infiltration (Fig. 1A). The bladder wall in eight of nine patients (89%) with ulcer type IC showed focal thickening, and the location of the focal bladder wall thickening was compatible with cystoscopic findings of Hunner\’s lesion (Fig. 1B). The bladder wall in patients with KC was significantly thicker than that in the other groups, and diffuse thickening of the bladder wall was present in every patient with KC (Fig. 1C). Diffuse thickening of the bladder wall was found in four of the eight KC patients with AE and two of five KC patients without AE. Fig. 2 shows significant correlations between the BWT and VAS, FBC, and MBC. Patients with thicker bladder walls had higher VAS (R2 = 0.484, p < 0.001), smaller FBC (R2 = 0.31, p = 0.002), and smaller MBC (R2 = 0.469, p < 0.001).
In previous studies, patients with IC or KC were found to have inflammatory changes in the bladder wall and elevated serum inflammatory biomarkers. The severity of bladder inflammation as shown by increased mast cell activities has been associated with increased urothelial apoptosis, and defective E-cadherin has been associated with severe clinical pain symptoms. Significantly more bladder inflammation, urothelial apoptosis, and defective E-cadherin have also been reported in patients with KC than in those with IC. This study further demonstrates that a thicker bladder wall on CT scan is also associated with increased bladder pain symptoms and reduced bladder capacity in patients who presented with bladder pain. In ulcer type IC, focal thickening of the bladder wall was noted, which was associated with the location of Hunner\’s lesion. In KC patients, by contrast, diffused thickening of the bladder wall was commonly seen. Perivesical infiltration was also remarkable in KC patients, in both those who had and those who did not have AE for intractable pain. These results provide evidence that BWT might be a good biomarker in the differential diagnosis of disease with bladder pain and might be a predictor of selecting patients for surgical intervention such as AE in patients with KC.
The differential diagnosis of diffused bladder wall thickening on radiology includes both neoplastic and nonneoplastic conditions. Neoplastic conditions that may demonstrate diffuse bladder wall thickening include transitional cell carcinoma and squamous cell carcinoma. Nonneoplastic conditions causing small bladder capacity and bladder wall thickening include IC, tuberculous cystitis, cystitis cystica, and schistosomiasis. Bladder wall thickening is also seen following the use of chemotherapeutic agents such as cyclophosphamide and radiation therapy. BWT has been reported to increase in patients with bladder outlet obstruction and overactive bladder. The detrusor is thought to increase in weight after long-term increased workload due to bladder outlet obstruction. However, in one study in patients with idiopathic overactive bladder, BWT was not different from that of controls.

br Future directions Practical applications of CTC and ctDNA

Future directions: Practical applications of CTC and ctDNA
Although these studies foreshadow the promise of personalized medicine for patient with urothelial cancer, improvements still lag behind progress made in other malignancies. To illustrate this point, one can look to progress achieved in lung cancer (characterized by a similar cornucopia of targetable alterations), for which EGFR and anaplastic lymphoma kinase inhibitors have become the epitome of precision medicine. As treatment with EGFR-inhibiting therapies has evolved to a more precision-based approach, efficacy/toxicity ratio and survival have increased. More recently, the state of the art has evolved from tissue-based markers to ctDNA to predict and monitor response [22,54], identify molecular progression before radiologic progression [22], and even to identify mechanisms of EGFR inhibitor resistance beyond EGFR-T790M [55]. In addition, at least one study has shown that sometimes EGFR mutations can be detected in serum when they are not present in biopsy, possibly owing to technical artifacts or sampling of a heterogenous tumor [54]. This case study highlights some of the positive developments that have occurred in lung cancer, as the field has progressed to clinical decision making based on tissue-based than circulating biomarkers which are still lacking in the care of patient with urothelial cancer. Similar progress has been made for other malignancies as well [56,57]. The recognized potential for ctDNA currently resides in the ability to safely access the tumor genome for quantification of residual disease and identification of therapeutic vulnerability- and resistance-conferring mutations. The yet-to-be recognized potential may lie in pharmacodynamic measurement of drug efficacy in real time using serial sampling and the possibility of reducing or eliminating sampling bias inherent to tissue biopsy.
What role do CTCs play then? As alluded to previously, ctDNA is probably more sensitive than CTCs for detecting disease and probably tell the clinician more about “what to do next.”Although clinically CTCs are probably used more often than ctDNA, some CTC assays still have not conclusively shown that the identified myeloperoxidase are true CTCs, limiting use. Assuming that these obstacles can be overcome, CTC-based biomarkers may still provide use. Sequencing of the CTC genome may be obviated by ctDNA, but expression markers are unique to CTCs. Tumor PD-L1 expression has been nominated as a predictive marker of immune checkpoint monoclonal antibodies, but it is not yet known whether tumor and CTC PD-L1 would correlate [16,23,24]. Circulating markers predicting immune response (or more generally chemoresponse) would be an excellent addition to the diagnostic armamentarium. Another potential role for CTCs may be in assessing the risk of subclinical metastasis. In patients undergoing complete tumor resection, ctDNA has been shown to have a short half-life, possibly less than 2 hours [58]. In contrast, CTCs may linger for years after curative-intent surgery in prostate cancer, for example [29]. It is not clear, however, whether ctDNA, CTCs, or a combination of both would be the best method for detecting minimal residual disease when patients show benignity on examination and imaging results. To date, it is also still not clear what the clinician should do if subclinical disease is detected.

Although used in other malignancies such as lung cancer and melanoma, biomarkers are scarce in bladder cancer and would provide better tools to assess disease stage and risk of metastasis, predict and monitor response to therapy, and identify recurrence at early stages. With the constant improvement in detection that new technologies provide, comes a need for an increased understanding of the basis of therapeutic vulnerability to cytotoxic and targeted agents and their acquired resistance mechanisms. The direction that successful research can take to translate into meaningful oncologic control and cure is clear. The recognized and yet-to-be recognized potential of circulating biomarkers would be realized when oncologists can detect aberrancies and have therapies that would change the trajectory of the patient׳s course. These emerging detection technologies are akin to Laënnec and the first stethoscope. Identifying an abnormal heart sound was probably quite exciting, but valve surgery would not evolve for more than a century later. The interval between reliable diagnostic tests and therapy would surely be shorter for circulating biomarkers, but thoughtful and innovative clinical trial design would be necessary to determine what effect and cost additional diagnostic tests will have.

The molecules of both HIV RT

The molecules of both HIV-1 RT and HIV-2 RT are heterodimers, consisting of two subunits (p66/p51 and p68/p54, for these two RTs, respectively) (Coffin et al., 1997; Herschhorn and Hizi, 2010; Hizi and Herschhorn, 2008). The three dimensional structures of both HIV-1 and HIV-2 RTs have been resolved in a number of forms (Ding et al., 1998; Huang et al., 1998; Jacobo-Molina et al., 1993; Kohlstaedt et al., 1992; Ren et al., 2002). The larger subunit in these highly-related RTs is composed of two domains, myeloperoxidase and RNase H. The DNA polymerase domain, which resembles a right hand (with fingers, palm and thumb subdomains), is joined to the RNase H domain by a connection subdomain. The polymerase active site is located within the palm subdomain of the larger subunit, whereas the RNase H domain is located at the C-terminus of this subunit. The smaller RT subunit is a limited proteolytic cleavage product of the larger subunit (from which the whole C-terminal segment is removed); therefore, it lacks the RNase H domain, while DNA polymerase domain of this subunit has the same subdomains as the larger one (though the relative folding in the heterodimers is different).
The specific DNA polymerase activities myeloperoxidase of purified recombinant RTs of HIV-1 and HIV-2 are similar. Nevertheless, the RNase H specific activity of HIV-1 RT was shown to be about 10-fold higher than that of HIV-2 RT, generated from both the ROD and D194 strains of HIV-2 (Hizi et al., 1991; Shaharabany and Hizi, 1992). This difference in the RNase H activity between the two HIV RTs is quantitative rather than qualitative, since the pattern of RNA cleavage by the two RTs is indistinguishable (Sevilya et al., 2003). Selective chimeric recombinant RTs, derived from both HIV-1 and HIV-2, have revealed that the protein׳s RNase H domain by itself does not affect the level of RNase H activity. Instead, the RT׳s polymerase domain in the smaller subunit has a major role in determining this RNase H level (Shaharabany and Hizi, 1992). The protein segment responsible for this difference was traced to the thumb subdomain in the small subunit; thus affecting the RNase H activity presumably through interactions with the RNase H catalytic domain of the larger subunit (Sevilya et al., 2001; Shaharabany and Hizi, 1992). Only a single amino acid, residue 294, in the thumb of the smaller RT subunit of the HIV RTs is responsible for the reported difference in the RNase H activity (Sevilya et al., 2003). At this position (located in the loop between helices aI and aJ in HIV-1 RT), there is a proline in HIV-1 RT and a glutamine in HIV-2 RT. Thus, a HIV-2 RT mutant, in which a proline substituted for the glutamine in only the p54 subunit, exhibited in vitro an RNase H activity (and, hence, a strand transfer activity) that is almost 10-fold higher than that of the wild-type (WT) HIV-2 RT (and approximately as high as WT HIV-1 RT). Steady-state kinetics of the RNase H activity indicated substantial differences in the apparent K values of the RTs (with similar turnover numbers, k values). Thus, both WT HIV-1 RT and the Q294P mutant of HIV-2 RT have an enhanced affinity towards the RNA-DNA substrate relative to WT HIV-2 RT, with no significant differences in the rates of the RNase H catalytic process (Sevilya et al., 2003).
A parallel conversion of Pro294 in p51 of HIV-1 RT to a glutamine caused a substantial decrease (by about 70%) in the specific RNase H activity of the RT, suggesting that, as in HIV-2 RT, residue 294 in HIV-1 RT is also critical for the RNase H function (Sevilya et al., 2003). Interestingly, a systematic mutagenesis of the Gln294 to ten different residues (in addition to Pro), representing different chemical types of amino acid side chains, showed that all modifications in the p54 subunit induced significant increases of the RNase H activity without affecting the polymerase activity (Bochner et al., 2008). These overall in vitro results represent a unique and rare case, in which every mutation introduced in a specific residue of an active enzyme induces an increase rather than a decrease in an enzyme׳s specific activity. Moreover, since the balance between the RNase H and polymerase activity of all Gln294 HIV-2 RT mutants was increased, an expected parallel rise in the strand transfer function was also observed (Sevilya et al., 2003).

While a role for H somni in

While a role for H. somni in BRD has been long recognised (Gogolewski et?al., 1987), emerging awareness of the virulence factors which aid its pathogenesis has highlighted the potential importance of that role. H. somni can adhere to endothelial cells causing the activation of platelets which promotes thrombus formation while lipooligosaccharide production can induce apoptosis of endothelial cells (Sylte et?al., 2001; Kuckleburg et?al., 2008) and help the pathogen to evade host defences through phase variation (Inzana et?al., 1992). Immunoglobulin binding proteins (Ibps), which are secreted from the surface of the pathogen, bind the Fc region of IgG2b (Bastida-Corcuera et?al., 1999) and may also facilitate bacterial dissemination from the lungs across the alveolar barrier; Agnes et?al. (2013) proposed a mechanism for dissemination which was mediated by retraction of alveolar type 2 cells, in response to Ibp A, and degradation of the basement membrane.
Biofilm formation by H. somni has also been recognised in vitro in both commensal and pathogenic strains. Bacterial biofilms are highly structured and organised myeloperoxidase of bacteria connected by an extracellular matrix which enable bacteria to colonise and persist in sites, enhancing their resistance to antibiotics and host defence mechanisms. As there are substantial differences in the amount and architecture of biofilm formed by commensal and pathogenic strains it has been suggested that the differences in biofilm structure may correlate with pathogenicity (Sandal et?al., 2007). Polymicrobial biofilms of commensal H. somni and Pasteurella multocida have been described (Elswaifi et?al., 2012). Transferring-binding proteins, which allow H. somni acquire iron from host components (Ekins et?al., 2004), histamine release, which causes vasoconstriction and increased permeability (Ruby et?al., 2002), and the resistance to killing by phagocytes (Siddaramppa and Inzana, 2004), also contribute to H. somni survival. This latter attribute, together with its ability to destroy macrophages within hours in vivo (Gogolewski et?al., 1987), has led to the suggestion by Corbeil (2007) that H. somni behaves more like an extracellular parasite than a facultative intracellular parasite which multiplies over time inside macrophages. Animal defence against H. somni appears to rely on antibody responses, particularly IgG2 (Gogolewski et?al., 1989; Corbeil et?al., 1997), however, IgE responses are also sometimes induced and were suggested by Gershwin et?al. (2005) to have a role in the pathogenesis of the more severe BRD in some animals. In studies using Western blotting, Corbeil et?al. (2006) demonstrated that the predominant H. somni antigen recognised by IgE was major outer membrane protein (MOMP), a virulence factor of H. somni, the precise functional role of which is still uncertain, but a role similar to bacterial porins has been proposed (Ueno et?al., 2014).
O\’Toole and Sondgeroth (2016) outlined three approaches to H. somni control in cattle: mass medication with antimicrobials, vaccination for H. somni or vaccination for other agents of the BRD complex that predispose to BRD. Mass medication with antimicrobials is discussed in detail in Part 2 of this review (Murray et?al., 2016b). Relevant to mass medication is the challenge potentially posed by an apparent trend of decreasing susceptibility of H. somni and other BRD pathogens to most of the antimicrobials used for the treatment and control of BRD (DeDonder and Apley, 2015). Antimicrobial resistance in BRD pathogens, including H. somni, mediated by plasmids and other integrative and conjugative elements (ICE) was evaluated by Klima et?al. (2014) in a study of isolates from US feedlots. Four of 10 H. somni lung isolates harboured multi-resistant genes. They demonstrated the presence of ICE in H. somni and the capacity for transfer of ICE from H. somni to P. multocida. Although plasmids have not been frequently isolated from H. somni, 15% of H. somni isolates from pneumonic lungs in one study in Denmark contained plasmids (Fussing and Wegener, 1993). In contrast, no plasmids were observed in any of 606 nasal isolates of H. somni from randomly selected healthy animals in a feedlot study by D\’Amours et?al. (2011). This led them to suggest that strains having plasmids may have virulence genes although this has not yet been proven. Portis et?al. (2012) recorded a decrease in the proportion of susceptible H. somni isolates, over a 10-year period from 2000 to 2009, which was most notable with enrofloxacin, florfenicol and tetracycline. Their report, which examined isolates from both sick and deceased animals, suggested that H. somni resistance was relatively low. This apparent divergence from the findings of Klima et?al. (2014) may be, in part, due to selection bias towards resistant pathogens in studies based on samples from BRD fatalities.