The role of scavenger receptor BI in hepatitis - eTheses Repository ...

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162 undergo proteolytic cleavage during egress, leading to a particle rearrangement and maturation, however this process is not essential for infectivity. Nelson et. al. demonstrated that mature WNV particles are up to 95-fold more resistant to anti-envelope mAb and that this could be attributed to reduced exposure of certain epitopes (228). However, describing HCV by analogy with other viruses only extends so far, our data suggests that HCV association with lipoproteins renders particles more resistant to neutralisation (Figure 5-8). We do not know whether lipoprotein components themselves obscure epitopes or if they simply stabilise particle structure, in either case HCV appears to have adopted a unique mechanism of evading host humoral responses. Lipoprotein association and epitope concealment, however, are not the only strategies employed by HCV to avoid nAbs. Recent reports indicate that B cells and dendritic cells are capable of uptake and cross-presentation of HCV, interestingly, SR-BI has been implicated in both cases (21, 23, 294). In B cells, internalised particles are shielded from nAbs and transfer of HCV from B cells to human hepatoma cells enhances infectivity by 30 fold (294), indicating that B cells may offer HCV safe and efficient passage to the liver. As discussed previously, HCV is also capable of direct cell-cell transmission (314), similar to that reported for other viruses (134, 137, 284). It is conceivable that in an organ such as the liver, cell-cell transmission may represent the major route of infection within a host, indeed if this is the case it will have major implications for those hoping to treat HCV with monoclonal antibody therapies (146).
163 Given our and other’s findings regarding the ability of HCV to evade nAb responses, the lack of clear evidence supporting a role for humoral immunity in controlling infection is unsurprising (87, 140, 182, 295, 327). Indeed the relatively late development of anti-HCV antibodies (64), may be partly attributable to the low availability of critical epitopes on circulating particles. However, there remains a discrepancy between in vivo studies and experiments using the HCVpp and HCVcc models of virus entry. Antibodies isolated from patients have been shown to efficiently neutralise HCVpp (182, 245), moreover there have been numerous accounts of anti-E2 mAbs inhibiting both HCVpp and HCVcc infectivity (130, 145, 172, 236, 307, 308). However, observations in vivo (87, 140, 182, 295) and our findings using JFH- 1 wt suggest that HCV may be relatively resistant to humoral immunity, indicating that more work is necessary to understand the relationship between authentic HCV particles and neutralising antibodies. Our findings using JFH-1 G451R demonstrate a link between particle sensitivity to neutralising antibodies and SR-BI dependency. Therefore, we are interested in examining the relationship between these two characteristics in different strains of HCVcc; J6/JFH exhibits a lower dependence for SR-BI (Figure 4-2), this phenotype may also reflect particle sensitivity to neutralisation. HCVpp are unlikely to mimic the structure of lipo-viro-particles and recapitulate natural HCV envelope protein conformation(s). Consequently they may not be suitable for assessing antibody mediated neutralisation. Indeed, experiments using HCVpp have suggested that blocking epitopes necessary
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The role of scavenger receptor B-I
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i Abstract. With 170 million infect
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iii Acknowledgements. I would like
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v 5 Results: Identification of a re
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vii Figure 5-5 Analysis of JFH-1 wt
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1 Introduction 1.1 The disease. 1 D
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3 predominantly immuno-pathogenic i
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5 Aside from considerations of the
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7 Current attempts to design a HCV
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1.2 An elusive pathogen. 9 The emer
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11 PCR). This technique is highly s
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13 Within six years of the descript
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1.3 Basic virology. 15 Like other m
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17 Figure 1-2 HCV genome and polypr
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19 241). E1 and E2 are anchored to
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21 The characterisation of HCV geno
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23 in the E1 and E2 glycoprotein ge
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25 The solution reached by a great
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27 binding to mouse cells. sE2 inte
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29 density lipoprotein (HDL), allow
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31 blood brain barrier is permeable
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33 act as receptors for viral entry
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1.4.2 Attachment factors 35 The tru
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1.4.3 Endocytosis and fusion 37 Aft
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39 1.4.4 Co-receptor interplay and
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41 inhibition of protein kinase A (
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1.5 Lipoproteins 43 Since 1992 ther
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45 Lipoproteins exist in a dynamic
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47 and delivers its cargo via the w
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49 uptake of cholesterol from LDL (
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Figure 1-4 SR-BI-lipoprotein intera
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53 In summary the class B scavenger
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55 In 1992 Thomssen et. al. demonst
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57 lipoprotein association promotes
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59 Figure 1-5 Lipo-viro-particle as
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61 In vitro culture medium, into wh
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2 Materials and methods. 2.1 Cell l
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Preparation of rat anti-E2 mAbs. 65
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2.4 Basic techniques. Flow cytometr
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69 6. Finally, the cells were washe
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71 (Promega, WI, USA) kits accordin
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73 proteins and are incapable of fu
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75 spectrophotometer (Amersham), we
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77 Figure 2-2 Electroporated Huh-7.
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79 5. Data is expressed as percenta
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81 (Invitrogen). The samples to be
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83 1. The SR-BII coding region was
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2.7 Cloning and synthesis of JFH-1
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The sequence encoding amino acids 3
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Figure 2-6 sE2 sequencing. 89 JFH-1
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91 7. Large scale transfections wer
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93 3 Results: Investigations using
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95 3.2 CHO cells expressing human S
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Figure 3-3 Ability of anti-E2 mAb t
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99 3.3 The interaction of sE2 with
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101 Figure 3-5 Position of SR-BI mu
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103 Table 3-2 Investigation of cell
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105 3.4 Expression of SR-BII in CHO
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3.5 Discussion. 107 We have demonst
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109 may offer a tool to study the i
Page 121 and 122: 111 Figure 4-1A displays endogenous
Page 123 and 124: 113 4.2 Exogenous expression of SR-
Page 125 and 126: 115 4.3 Evidence of enhanced JFH-1
Page 127 and 128: 117 4.4 SR-BI expression levels lim
Page 129 and 130: 119 4.5 Murine SR-BI does not enhan
Page 131 and 132: 121 4.6 SR-BI/II expression levels
Page 133 and 134: 123 Figure 4-5 Over expression of S
Page 135 and 136: 125 Figure 4-6 Anti-SR-BI serum inh
Page 137 and 138: 127 Figure 4-7 Infection of Huh-7.5
Page 139 and 140: 129 cells is largely manifested in
Page 141 and 142: 131 5 Results: Identification of a
Page 143 and 144: 133 Figure 5-1 JFH-1 G451R has an a
Page 145 and 146: 135 Figure 5-2 CD81 dependence of J
Page 147 and 148: 137 G451R sE2 with hCD81 LEL we com
Page 149 and 150: 139 Figure 5-4 JFH-1 wt and G451R s
Page 151 and 152: 141 demonstrated a lower dependence
Page 153 and 154: 143 Figure 5-6 Relationship between
Page 155 and 156: 145 flow cytometry (data not shown)
Page 157 and 158: 147 5.6 Low density JFH-1 particles
Page 159 and 160: 5.7 Discussion. 149 We have demonst
Page 161 and 162: 151 Numerous reports have used dens
Page 163 and 164: 153 demonstrate that low density JF
Page 165 and 166: 155 to over express SR-BI we were a
Page 167 and 168: 157 5-1), better able to engage CD8
Page 169 and 170: 159 Figure 6-1 An overview of antib
Page 171: 161 it is believed that ligation of
Page 175 and 176: 6.3 HCV lipo-viro-particles. 165 As
Page 177 and 178: 167 represent the hyper-variable re
Page 179 and 180: 169 The G451R mutation disrupts the
Page 181 and 182: 7 Bibliography 171 1. Acton, S., D.
Page 183 and 184: 173 include the CD81 tetraspanin an
Page 185 and 186: 175 receptor class B type I and inh
Page 187 and 188: 177 83. Drummer, H. E., K. A. Wilso
Page 189 and 190: 179 KewalRamani, D. R. Littman, C.
Page 191 and 192: 181 King. 1996. Efficient infection
Page 193 and 194: 183 hepatitis C virus envelope glyc
Page 195 and 196: 185 recovered chimpanzees exhibit r
Page 197 and 198: 187 218. Monazahian, M., I. Bohme,
Page 199 and 200: 189 243. Perez-Berna, A. J., J. Gui
Page 201 and 202: 191 single-cycle production assay t
Page 203 and 204: 193 298. Strickland, G. T., S. S. E
Page 205 and 206: 195 Remaley, G. Csako, T. L. Eggerm
Page 207: 197 2007. Scavenger receptor class
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