Andrew F. Geczy

HLA-B27, Klebsiella and Ankylosing Spondylitis: Biological and Chemical Studies

Almost a decade has elapsed sitice the remarkable association between HLAB27 and ankylosing spondylitis (AS) was first reported {Brewerton et al. 1973, Schlosstein et al. 1973). Subsequent studies have revealed an association between HLA-B27 and other seronegative arthropathies (e.g. Reiters syndrome) and some forms of reactive arthritis which follow infection with certain enteric organisms (Aho et a!. 1973, 1974, Friis & Svejgaard 1974). Despite the striking correlation between this HLA specificity and the seronegative arthropathies, the underlying immunochemical basis of this association is still not understood. Studies during the past few years have shed light on some important elements of the association between B27 with certain rheumatic diseases: a) While B27 represents an important clue to genetic predisposition, this allele alone is insufficient to cause disease; b) environmental agents, probably certain enteric bacteria, are involved in the pathogenesis. This view is supported by the finding that identical twins may be discordant for the disease (Eastmond & Woodrow 1977) and by the recent demonstration that some Klebsiella products are antigenicaliy related to cell surface determinants on the tissues of HLA-B27positive patients with AS {Seager et a!. 1979, Geczy et al. 1980c). Furthermore, Yersinia, Shigella and Salmonella are capable of triggering arthritis in HLAB27-positive individuals (Aho et al. 1973, 1974, Friis & Svejgaard 1974, Calin & Fries 1976, Ford et al. 1977).

Lymphoproliferative immune function in the Sydney Blood Bank Cohort, infected with natural nef/long terminal repeat mutants, and in other long-term survivors of transfusion-acquired HIV-1 infection

Objectives:To assess T-helper cell immune function (proliferation) in members of the Sydney Blood Bank Cohort (SBBC) compared with other individuals with transfusion- and sexually acquired HIV-1 infection and with matched HIV-negative controls. Design and methods:Decreasing CD4 counts and T-helper cell function are associated with disease progression. Peripheral blood mononuclear cells (PBMC) from study subjects were assayed for in vitro proliferative responses to HIV-1-derived antigens, recall antigens and alloantigen. T-helper cell function and CD4 counts in members of the SBBC were followed longitudinally. Results:Proliferative responses and CD4 counts from members of the SBBC were similar to or better than those of other transfusion- or sexually-acquired HIV-1-positive long-term non-progressors (LTNP), including the HIV-negative matched SBBC control groups. However, individuals with disease progression had reduced or undetectable proliferative responses to recall antigens but a conserved response to alloantigen; they also had low CD4 counts and low CD4 : CD8 ratios. In the SBBC, these immune parameters were usually stable over time. Conclusions:The unique SBBC with natural nef/long terminal repeat deletions in the HIV-1 genome were genuine LTNP without showing signs of disease progression. They appeared to be a group distinct from the tail-end of the normal distribution of disease progression rates, and may remain asymptomatic indefinitely. The SBBC virus may form the basis of a live attenuated immunotherapeutic or immunoprophylactic HIV vaccine.

A Large, Single Center Investigation Of The Immunogenetic Factors Affecting Liver Transplantation

BACKGROUND Reports on the relevance of immunogenetic factors in liver transplantation are often conflicting or inconclusive. We have, therefore, investigated a range of factors that may underlie liver graft survival. METHODS The influences of HLA, flow cytometric, and enhanced cytotoxic crossmatching and immunoglobulin (Ig)A levels on graft survival, and acute and chronic rejection were investigated for a single center involving 446 patients over 13 years. RESULTS The effect of HLA mismatching on graft survival was significant (P<10(-2)) and was reversed in recipients with autoimmune diseases (P<0.5x10(-2)), whereas the effect of HLA mismatches on the level of acute rejection was detrimental in all recipients. There was a significant effect of a positive cytotoxic crossmatch on 3-month (P<10(-5)) and 1-year (P<10(-4)) graft survival, and an additional effect of the flow cytometric crossmatch was seen for chronic rejection (P<10(-2)) and acute rejection (P<10(-2)). Recipients with HLA-A1,B8,DRB1*0301 had higher levels of acute rejection (P<0.5x10(-2)), and recipients who received an ABO compatible-nonidentical transplant have a significantly higher risk (P<10(-2)) of developing chronic rejection. Finally, the beneficial effect of high serum IgA and, specifically, IgA anti Fab, seen in renal transplants was not evident in liver transplants, and in fact the opposite may be true, at least for acute rejection (P<0.5x10(-2)). CONCLUSIONS By separating the recipients with autoimmune disease from other patients and by including acute and chronic rejection as outcome parameters, we have used the power of a large single-centre study to delineate the significance of some of the important immunogenetic factors involved in liver transplantation.

Mechanisms of HIV non-progression; robust and sustained CD4+ T-cell proliferative responses to p24 antigen correlate with control of viraemia and lack of disease progression after long-term transfusion-acquired HIV-1 infection

BackgroundElite non-progressors (plasma viral load <50 copies/ml while antiretroviral naive) constitute a tiny fraction of HIV-infected individuals. After 12 years follow-up of a cohort of 13 long-term non-progressors (LTNP) identified from 135 individuals with transfusion-acquired HIV infection, 5 remained LTNP after 23 to 26 years infection, but only 3 retained elite LTNP status. We examined the mechanisms that differentiated delayed progressors from LTNP in this cohort.ResultsA survival advantage was conferred on 12 of 13 subjects, who had at least one host genetic factor (HLA, chemokine receptor or TLR polymorphisms) or viral attenuating factor (defective nef) associated with slow progression. However, antiviral immune responses differentiated the course of disease into and beyond the second decade of infection. A stable p24-specific proliferative response was associated with control of viraemia and retention of non-progressor status, but this p24 response was absent or declined in viraemic subjects. Strong Gag-dominant cytotoxic T lymphocyte (CTL) responses were identified in most LTNP, or Pol dominant-CTL in those with nef-defective HIV infection. CTL were associated with control of viraemia when combined with p24 proliferative responses. However, CTL did not prevent late disease progression. Individuals with sustained viral suppression had CTL recognising numerous Gag epitopes, while strong but restricted responses to one or two immunodominant epitopes was effective for some time, but failed to contain viraemia over the course of this study. Viral escape mutants at a HLA B27-restricted Gag-p24 epitope were detected in only 1 of 3 individuals, whereas declining or negative p24 proliferative responses occurred in all 3 concurrent with an increase in viraemia.ConclusionDetectable viraemia at study entry was predictive of loss of LTNP status and/or disease progression in 6 of 8, and differentiated slow progressors from elite LTNP who retained potent virological control. Sustained immunological suppression of viraemia was independently associated with preserved p24 proliferative responses, regardless of the strength and breadth of the CTL response. A decline in this protective p24 response preceded or correlated with loss of non-progressor status and/or signs of disease progression.

Donor Helper T-cell frequencies as predictors of acute graft-versus-host disease in bone marrow transplantation between HLA-identical siblings

BACKGROUND Despite the current level of sophistication of molecular typing for class I and class II alleles, a significant proportion (20-40%) of recipients of HLA-identical sibling marrow develop severe, acute graft-versus-host disease (GVHD) after bone marrow transplantation. It has been suggested that the frequency of patient-specific helper T lymphocyte precursors (HTLp) detected in the HLA-identical sibling donor correlates with the incidence and severity of acute GVHD after transplantation. METHODS This study group consisted of 42 patients who all received bone marrow from HLA-identical sibling donors from January 1990 to December 1996. Using a limiting dilution analysis, donor HTLp frequencies were determined on samples collected before transplantation. The HTLp assay used the cytotoxic T-cell line, CTLL-2, which proliferates in the presence of interleukin-2. The reliability and reproducibility of this assay was established by using cryopreserved batches of CTLL-2 cells of known sensitivity. RESULTS The recipient-directed HTLp frequencies detected in the donor before transplantation were correlated with the incidence and severity of acute GVHD experienced by the recipient after transplantation. Statistical analysis revealed an extremely significant correlation between donor precursor frequencies and the development of acute GVHD in the patient after transplantation (P<0.0001). CONCLUSIONS This study suggests that together with molecular typing the HTLp frequency should be considered when selecting the most suitable sibling donor for bone marrow transplantation.

Is a Klebsiella plasmid involved in the aetiology of Ankylosing Spondylitis in HLA-B27-positive individuals?

The possibility that plasmid genes, carried by enteric organisms previously indirectly implicated as disease agents, play a role in the pathogenesis of Ankylosing Spondylitis (AS) was explored. A particular Klebsiella isolate (K21) previously found to cross-react with cells from HLA-B27 positive (B27+) patients with AS, but not with cells from normal individuals, was found to contain a plasmid(s). This coded for the organisms ability to produce a factor which could modify B27+ normal cells (AS-) rendering them lysable by the anti-Klebsiella serum. Curing of this isolate resulted in the loss of the plasmid concerned and a loss of ability of its culture filtrate to modify B27+ lymphocytes of clinically healthy subjects. When plasmids from K21 were transferred to a plasmid free laboratory strain, E. coli JP995, the recipient strain acquired the ability to elaborate modifying factor. These data suggest that plasmids, harboured by some enteric bacteria, and their products, may be implicated in modifying cells bearing certain Major Histocompatibility Complex genes, and that such modification may be an important factor in the pathogenesis of a number of diseases including the seronegative arthropathies.

Association of Fc gamma receptor IIA polymorphisms with acute renal-allograft rejection.

Acute rejection is a leading cause of early renal-allograft failure. The human Fc gamma receptor IIA (Fc&ggr;RIIA) forms an essential link between the humoral branch and the effector cells of the immune system. In this study, we examined Fc&ggr;RIIA genotypes in renal-allograft recipients (rejectors) with acute graft rejection and in a number of control groups to investigate a possible association between Fc&ggr;RIIA polymorphism and acute renal-allograft rejection. The distribution of the genotypes in the study patient group differed from the control groups. The frequency of homozygosity for Fc&ggr;RIIA-R/R131 in the rejectors was significantly higher than that in the recipients (nonrejectors) with well-functioning renal allografts and in blood donors (P< 0.05). In comparison with the control groups, the rejectors displayed a higher R131 allele frequency (P< 0.05) and a lower H131 allele frequency (P< 0.05). These results reveal a significant association between Fc&ggr;RIIA-R/R131 and acute renal-graft rejection, and it is likely that Fc&ggr;RIIA polymorphisms could be useful markers for potential risk of rejection.

Effect of Long-Term Infection with nef-Defective Attenuated HIV Type 1 on CD4+ and CD8+ T Lymphocytes: Increased CD45RO+ CD4+ T Lymphocytes and Limited Activation of CD8+ T Lymphocytes

Members of the Sydney Blood Bank Cohort (SBBC) have been infected with an attenuated strain of HIV-1 with a natural nef/LTR mutation and have maintained relatively stable CD4+ T lymphocyte counts for 14-18 years. Flow cytometric analysis was used to examine the phenotype of CD4+ and CD8+ T lymphocytes in these subjects, including the immunologically important naive (CD45RA+CD62L+), primed (CD45RO+), and activated (CD38+HLA-DR+ and CD28-) subsets. The median values were compared between the SBBC and control groups, comprising age-, sex-, and transfusion-matched HIV-1-uninfected subjects; transfusion-acquired HIV-1-positive LTNPs; and sexually acquired HIV-1-positive LTNPs. Members of the SBBC not only had normal levels of naive CD4+ and CD8+ T lymphocytes, but had primed CD45RO+ CD4+ T lymphocytes at or above normal levels. Furthermore, these primed cells expressed markers suggesting recent exposure to specific antigen. SBBC members exhibited variable activation of CD8+ T lymphocytes. In particular, SBBC members with undetectable plasma HIV-1 RNA had normal levels of activated CD8+ T lymphocytes. Therefore, the result of long-term infection with natural nef/LTR mutant HIV-1 in these subjects suggests a decreased cytopathic effect of attenuated HIV-1 on susceptible activated CD4+ T lymphocyte subsets in vivo, and minimal activation of CD8+ T lymphocytes.

Influence of FcgammaRIIA and MBL polymorphisms on severe acute respiratory syndrome.

Abstract Polymorphisms of human Fc γ‐receptor IIA (FcγRIIA) and mannose‐binding lectin (MBL) genes have been associated with susceptibility to or severity of some infectious diseases. In order to investigate whether these genetic factors might influence susceptibility to infection with the severe acute respiratory syndrome‐associated coronavirus (SARS‐Cov) as well as the course and severity of the infection, we evaluated polymorphisms of FcγRIIA and MBL genes in DNA samples from a group of approximately 180 people from Hong Kong who were infected with SARS‐Cov. These included 132 patients who had moderate course of SARS infection (home subgroup), 26 patients with a severe course requiring treatment in an intensive care ward (ICU subgroup) and a subgroup of 22 patients who died from SARS (deceased subgroup). A total of 200 normal blood donors from the same region were used as controls. A significant association was found between the FcγRIIA‐R/R131 genotype and a severe course of SARS, with higher frequency of homozygosity for FcγRIIA‐R/R131 in the ICU subgroup of SARS patients when compared with controls (P = 0.03; odds ratio: 3.2; 95% confidence interval: 1.1–9.1). In comparison with controls, a significant difference in linear trend distribution of FcγRIIA genotypes was seen among the severe SARS patients (ICU and deceased subgroups) without co‐morbidity, and the incidence of FcγRIIA‐H/H131 was lower in these patients as well. There were no significant differences in MBL genotypes and allele frequencies among SARS patients and controls. The study reveals that in addition to age and co‐morbidity, FcγRIIA polymorphism of individuals may also influence outcome after infection with the SARS‐Cov.

HLA and other host factors in transfusion-acquired HIV-1 infection

The host and viral factors that underlie infection with HIV-1 vary considerably with some individuals progressing to AIDS within 3 to 5 years after infection, whereas others remain clinically asymptomatic for over 10 years. Host factors that may contribute to disease progression include HLA and allelic variants of the chemokine receptors CCR5 and CCR2, which have been shown to influence both long-term survival and rapid progression. In this study, we have examined the contribution of HLA and polymorphisms in CCR5 and CCR2 to long-term survival in transfusion-acquired HIV-1-infected individuals. We have found a higher number of HLA-A32 and -A25 alleles but a lower number of the HLA-B8 allele in the study group compared with the frequencies seen in the HIV-1-negative Australian caucasian population. However, there was no apparent contribution by allelic variants of CCR5 and CCR2 to long-term survival and the combined influence of HLA and CCR polymorphisms could not be evaluated in this relatively small (n = 20) group of study subjects. The results of this work support a role for HLA in long-term nonprogression though the presence in the Sydney Blood bank Cohort of nef-defective HIV-1 may confound associations between certain HLA alleles and long-term survival in the face of infection with HIV-1.