Xiaoning Xu

Chelsea and Westminster Hospital NHS Foundation Trust, Londinium, England, United Kingdom

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Publications (15)129.65 Total impact

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    ABSTRACT: During HIV type-1 (HIV-1), hepatitis C virus (HCV), and hepatitis B virus (HBV) infections, altered iron balance correlates with morbidity. The liver-produced hormone hepcidin dictates systemic iron homeostasis. We measured hepcidin, iron parameters, cytokines, and inflammatory markers in three cohorts: plasma donors who developed acute HIV-1, HBV, or HCV viremia during the course of donations; HIV-1-positive individuals progressing from early to chronic infection; and chronically HIV-1-infected individuals (receiving antiretroviral therapy or untreated). Hepcidin increased and plasma iron decreased during acute HIV-1 infection, as viremia was initially detected. In patients transitioning from early to chronic HIV-1 infection, hepcidin in the first 60 d of infection positively correlated with the later plasma viral load set-point. Hepcidin remained elevated in individuals with untreated chronic HIV-1 infection and in subjects on ART. In contrast to HIV-1, there was no evidence of hepcidin up-regulation or hypoferremia during the primary viremic phases of HCV or HBV infection; serum iron marginally increased during acute HBV infection. In conclusion, hepcidin induction is part of the pathogenically important systemic inflammatory cascade triggered during HIV-1 infection and may contribute to the establishment and maintenance of viral set-point, which is a strong predictor of progression to AIDS and death. However, distinct patterns of hepcidin and iron regulation occur during different viral infections that have particular tissue tropisms and elicit different systemic inflammatory responses. The hypoferremia of acute infection is therefore a pathogen-specific, not universal, phenomenon.
    Proceedings of the National Academy of Sciences of the United States of America. 08/2014;
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    ABSTRACT: HLA class I alleles have been shown to have differential impacts on the viral load and the outcome of HIV-1 disease progression. In this study, HLA class I types from residents of China with acute HIV-1 infection, diagnosed between 2006 and 2011, were identified and the association among expression of individual HLA alleles and level of set-point viral load was analyzed. A lower level of set-point viral load was found to be associated with the Bw4 homozygote on HLA-B alleles. B*44 and B*57 alleles have also been found to be associated with lower set-point viral load. The set-point viral load of B*44-positive individuals homozygous for Bw4 was significantly lower than that of B*44-negative individuals homozygous for Bw4 (P=0.030). CD4 count declined to <350 in fewer B*44-positive individuals than in B*44-negative individuals (X(2)=7.295, P=0.026). B*44-positive individuals had a weaker magnitude of p24 pool-specific T cell responses than that of B*44-negative individuals homozygous for Bw4, though this was not significant. The p24 pool-specific T cell responses were also inversely correlated with lower viral load (rs=-0.88, P=0.033). Six peptides within p24 were recognized to induce the specific-T cell response in B*44-positive individuals and the peptide breadth was same as that in B*44-negative individuals, but the median magnitude of specific-T cell responses to the recognized peptides in B*44-positive individuals was weaker than that of B*44-negative individuals homozygous for Bw4 (P=0.049). These findings imply that weak p24-specific CD8(+) T cell responses might play an important role in the control of HIV viremia in B*44 allele individuals. Such studies might contribute to the development of future therapeutic strategies that take into account the genetic background of the patients.
    Clinical and vaccine Immunology: CVI 05/2013; · 2.60 Impact Factor
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    ABSTRACT: OBJECTIVE:: Little is known about the natural history of the HIV infection in men who have sex with men (MSM) in China. METHODS:: We compared changes in CD4 T cell count and HIV-RNA following seroconversion prior to starting antiretroviral-therapy between MSM in China andin resource-rich countries using data from the Beijing PRIMO cohort and CASCADE, respectively. Linear mixed models were used to compare rates of CD4 decline (cubic root scale) and changes in HIV-RNA (log10 scale) in the first 3 years following seroconversion. RESULTS:: For 131 PRIMO and 3171 CASCADE MSM infected 2001-2010, estimated CD4 T cell count at seroconversion was lower in PRIMO (504 cells/mm; 95% CI: 463-547) compared to CASCADE (554 cells/mm; 544-564). CD4 decline was significantly faster for PRIMO men (-0.59, [-0.72 to -0.47], and -0.41 [-0.44 to -0.38] cubic root of CD4 count/ year for PRIMO and CASCADE, respectively), even after restricting to subtype B (p=0.01). HIV-RNA at seroconversion was lower in PRIMO compared to CASCADE MSM (difference 0.425 log10/ml [0.249-0.603], P<0.001). After the first year of seroconversion, PRIMO MSM experienced a faster increase in HIV-RNA (0.830 log10/ml per year; [0.484-1.168] compared with CASCADE (0.018 [-0.035-0.067] (p<0.001). CONCLUSIONS:: CD4 decline and HIV-RNA increase are faster among MSM in China compared to MSM from resource-rich settings. Whether this is due to differences in host immunity or viral characteristics requires further exploration.
    JAIDS Journal of Acquired Immune Deficiency Syndromes 12/2012; · 4.65 Impact Factor
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    ABSTRACT: OBJECTIVE:: The HIV viral load set point has long been used as a prognostic marker of disease progression and more recently as an end-point parameter in HIV vaccine clinical trials. The definition of set point, however, is variable. Moreover, the earliest time at which the set point is reached after the onset of infection has never been clearly defined. METHODS:: In this study, we obtained sequential plasma viral load data from 60 acutely HIV-infected Chinese patients among a cohort of men who have sex with men, mathematically determined viral load set point levels, and estimated time to attain set point after infection. We also compared the results derived from our models and that obtained from an empirical method. RESULTS:: With novel uncomplicated mathematic model, we discovered that set points may vary from 21 to 119 days dependent on the patients' initial viral load trajectory. The viral load set points were 4.28 ± 0.86 and 4.25 ± 0.87 log10 copies per milliliter (P = 0.08), respectively, as determined by our model and an empirical method, suggesting an excellent agreement between the old and new methods. CONCLUSIONS:: We provide a novel method to estimate viral load set point at the very early stage of HIV infection. Application of this model can accurately and reliably determine the set point, thus providing a new tool for physicians to better monitor early intervention strategies in acutely infected patients and scientists to rationally design preventative vaccine studies.
    JAIDS Journal of Acquired Immune Deficiency Syndromes 12/2012; 61(4):448-454. · 4.65 Impact Factor
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    ABSTRACT: Cytokines play key roles in modulating disease progression in simian immunodeficiency virus/human immunodeficiency virus (SIV/HIV) infection. There are a few studies on the relationship between early cytokines and HIV disease prognosis. In this study, we first report the relationship based on two groups with clearly different disease progression. We found that IP-10 was the only cytokine among the 26 cytokines tested that was always positively correlated with disease progression, and was associated with the time for CD4 counts to fall below 200 cells/μL during Fiebig stages III-V in HIV-1 infection. This suggests that high IP-10 levels in the blood are associated with rapid disease progression during Fiebig stages III-V in HIV-1 infection.
    Viral immunology 07/2012; 25(4):333-7. · 1.78 Impact Factor
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    ABSTRACT: Rare human immunodeficiency virus type 1 (HIV-1)-infected individuals who maintain control of viremia without therapy show potent CD8+ T-cell-mediated suppression of viral replication in vitro. Whether this is a determinant of the rate of disease progression in viremic individuals is unknown. We measured CD8+ T-cell-mediated inhibition of a heterologous HIV-1 isolate in 50 HIV-1-seropositive adults with diverse progression rates. Linear mixed models were used to determine whether CD8+ T-cell function could explain variation in the rate of CD4+ T-cell decline. There was a significant interaction between CD8+ T-cell antiviral activity in vitro and the rate of CD4+ T-cell decline in chronically infected individuals (P < .0001). In a second prospective analysis of recently infected subjects followed for up to 3 years, CD8+ T-cell antiviral activity strongly predicted subsequent CD4+ T-cell decline (P < .0001) and explained up to 73% of the interindividual variation in the CD4+ T-cell slope. In addition, it was inversely associated with viral load set point (r = -0.68 and P = .002). The antiviral inhibitory capacity of CD8+ T cells is highly predictive of CD4+ T-cell loss in early HIV-1 infection. It has potential as a benchmark of effective immunity in vaccine evaluation.
    The Journal of Infectious Diseases 06/2012; 206(4):552-61. · 5.85 Impact Factor
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    ABSTRACT: Abstract Cellular immune responses play a critical role in the control of human immunodeficiency virus type 1 (HIV-1), but less is known about the impact of transmission routes on immune defenses against HIV-1. Here, we report that subjects infected with HIV-1 through contaminated blood showed stronger HIV-specific T cell responses than those infected through mucosa, both in breadth (6.9±2.5 vs. 2.3±0.5, p=0.0293) and in magnitude [1270.0±544.9 vs. 409.5±121.3 SFU per million peripheral blood mononuclear cells (PBMCs), p=0.0223], by using a matrix of 404 overlapping peptides spanning all expressed HIV-1 proteins in an interferon (IFN)-γ enzyme-linked immunospot (ELISpot) assay. Our observation indicates that different mechanisms might be involved in the priming/generating of anti-HIV-specific T cell responses through different transmission routes.
    AIDS research and human retroviruses 06/2012; · 2.18 Impact Factor
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    ABSTRACT: Polymorphism in the HLA region of a chromosome is the major source of host genetic variability in HIV-1 outcome, but there is limited understanding of the mechanisms underlying the beneficial effect of protective class I alleles such as HLA-B57, -B27, and -B51. Taking advantage of a unique cohort infected with clade B' HIV-1 through contaminated blood, in which many variables such as the length of infection, the infecting viral strain, and host genetic background are controlled, we performed a comprehensive study to understand HLA-B51-associated HIV-1 control. We focused on the T cell responses against three dominant HLA-B51-restricted epitopes: Gag327-345(NI9) NANPDCKTI, Pol743-751(LI9) LPPVVAKEI, and Pol283-289(TI8) TAFTIPSI. Mutations in all three dominant epitopes were significantly associated with HLA-B51 in the cohort. A clear hierarchy in selection of epitope mutations was observed through epitope sequencing. L743I in position 1 of epitope LI9 was seen in most B51(+) individuals, followed by V289X in position 8 of the TI8, and then, A328S, in position 2 of the NI9 epitope, was also seen in some B51(+) individuals. Good control of viral load and higher CD4(+) counts were significantly associated with at least one detectable T cell response to unmutated epitopes, whereas lower CD4(+) counts and higher viral loads were observed in patients who had developed escape mutations in all three epitopes or who lacked T cell responses specific to these epitope(s). We propose that patients with HLA-B51 benefit from having multiple layers of effective defense against the development of immune escape mutations.
    The Journal of Immunology 06/2011; 187(2):684-91. · 5.52 Impact Factor
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    ABSTRACT: Obstacles to developing an HIV-1 vaccine include extensive viral diversity and lack of correlates of protective immunity. High mutation rates allow HIV-1 to adapt rapidly to selective forces such as antiretroviral therapy and immune pressure, including HIV-1-specific CTLs that select viral variants which escape T-cell recognition. Multiple factors contribute to HIV-1 diversity, making it difficult to disentangle the contribution of CTL selection without using complex analytical approaches. We describe an HIV-1 outbreak in 231 former plasma donors in China, where a narrow-source virus that had contaminated the donation system was apparently transmitted to many persons contemporaneously. The genetic divergence now evident in these subjects should uniquely reveal how much viral diversity at the population level is solely attributable to host factors. We found significant correlations between pair-wise divergence of viral sequences and HLA class I genotypes across epitope-length windows in HIV-1 Gag, reverse transcriptase, integrase, and Nef, corresponding to sites of 140 HLA class I allele-associated viral polymorphisms. Of all polymorphic sites across these 4 proteins, 24%-56% were sites of HLA-associated selection. These data confirm that CTL pressure has a major effect on inter-host HIV-1 viral diversity and probably represents a key element of viral control.
    Blood 05/2011; 118(1):98-106. · 9.06 Impact Factor
  • International Journal of Infectious Diseases - INT J INFECT DIS. 01/2009; 13.
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    ABSTRACT: Identification of the nature of severe acute respiratory syndrome (SARS)-infected cells is crucial toward understanding the pathogenesis. Using multicolor colocalization techniques, we previously reported that SARS(+) cells in the lung of fatally infected patients expressed the only known functional receptor, angiotensin-converting enzyme 2, and also a binding receptor, liver/lymph node-specific ICAM-3-grabbing non-integrin (CD209L). In this study, we show that SARS-infected cells also express the stem/progenitor cell markers CD34 and Oct-4, and do not express cytokeratin or surfactant. These putative lung stem/progenitor cells can also be identified in some non-SARS individuals and can be infected by SARS-coronavirus ex vivo. Infection of these cells may contribute to the loss of lung repair capacity that leads to respiratory failure as clinically observed.
    Journal of Experimental Medicine 11/2007; 204(11):2529-36. · 13.21 Impact Factor
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    ABSTRACT: Dengue virus infection poses a growing public health and economic burden in a number of tropical and subtropical countries. Dengue circulates as a number of quasispecies, which can be divided by serology into four groups or serotypes. An interesting feature of Dengue, recognized over five decades ago, is that most severe cases that show hemorrhagic fever are not suffering from a primary infection. Instead, they are reinfected with a virus of different serotype. This observation poses considerable problems in vaccine design, and it is therefore imperative to gain a full understanding of the mechanisms underlying this immunological enhancement of disease. In this study, we examined a T cell epitope restricted by HLA-A*24, a major MHC class I allele, in Southeast Asia in a cohort of children admitted to a hospital with acute Dengue infection. The cytokine profiles and the degranulation capacity of T cells generated to this epitope are defined and compared across different viral serotypes. Cross-reactive Dengue-specific T cells seem to show suboptimal degranulation but high cytokine production, which may contribute to the development of the vascular leak characteristic of Dengue hemorrhagic fever.
    The Journal of Immunology 04/2006; 176(6):3821-9. · 5.52 Impact Factor
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    ABSTRACT: Cytotoxic T lymphocytes (CTLs) are critical for the control of human immunodeficiency virus, but containment of virus replication can be undermined by mutations in CTL epitopes that lead to virus escape. We analyzed the evolution in vivo of an immunodominant, HLA-A2-restricted CTL epitope and found two principal, diametrically opposed evolutionary pathways that exclusively affect T cell-receptor contact residues. One pathway was characterized by acquisition of CTL escape mutations and the other by selection for wild-type amino acids. The pattern of CTL responses to epitope variants shaped which variant(s) prevailed in the virus population. The pathways notably influenced the amount of plasma virus, as patients with efficient CTL selection had lower plasma viral loads than did patients without efficient selection. Thus, viral escape from CTL responses does not necessarily correlate with disease progression.
    Nature Immunology 03/2006; 7(2):179-89. · 26.20 Impact Factor
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    ABSTRACT: Severe acute respiratory syndrome (SARS) is caused by infection of a previously undescribed coronavirus (CoV). L-SIGN, encoded by CLEC4M (also known as CD209L), is a SARS-CoV binding receptor that has polymorphism in its extracellular neck region encoded by the tandem repeat domain in exon 4. Our genetic risk association study shows that individuals homozygous for CLEC4M tandem repeats are less susceptible to SARS infection. L-SIGN is expressed in both non-SARS and SARS-CoV-infected lung. Compared with cells heterozygous for L-SIGN, cells homozygous for L-SIGN show higher binding capacity for SARS-CoV, higher proteasome-dependent viral degradation and a lower capacity for trans infection. Thus, homozygosity for L-SIGN plays a protective role during SARS infection.
    Nature Genetics 02/2006; 38(1):38-46. · 35.21 Impact Factor
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    ABSTRACT: HIV-specific cytotoxic T lymphocytes (CTL) are important in controlling HIV replication, but the magnitude of the CTL response does not predict clinical outcome. In four donors with delayed disease progression we identified Vbeta13.2 T cell receptors (TCRs) with very similar and unusually long beta-chain complementarity determining region 3 (CDR3) regions in CTL specific for the immunodominant human histocompatibility leukocyte antigens (HLA)-B8-restricted human immunodeficiency virus-1 (HIV-1) nef epitope, FLKEKGGL (FL8). CTL expressing Vbeta13.2 TCRs tolerate naturally arising viral variants in the FL8 epitope that escape recognition by other CTL. In addition, they expand efficiently in vitro and are resistant to apoptosis, in contrast to FL8-specific CTL using other TCRs. Selection of Vbeta13.2 TCRs by some patients early in the FL8-specific CTL response may be linked with better clinical outcome.
    Journal of Experimental Medicine 01/2005; 200(12):1547-57. · 13.21 Impact Factor

Publication Stats

385 Citations
129.65 Total Impact Points

Institutions

  • 2014
    • Chelsea and Westminster Hospital NHS Foundation Trust
      Londinium, England, United Kingdom
  • 2013
    • Oxford University Hospitals NHS Trust
      • Nuffield Department of Medicine
      Oxford, England, United Kingdom
  • 2007
    • University of Oxford
      • MRC Human Immunology Unit
      Oxford, ENG, United Kingdom