Fang Fang Yuan

Immunological responses to pneumococcal vaccine in frail older people.

UNLABELLED Advanced age has been associated with a wide range of defects in both the innate and adaptive immune systems including diminished specific antibody responses that increase the risk of invasive pneumococcal disease (IPD) and limit the effectiveness of vaccines. However, the elderly are a heterogeneous group and measures of overall frailty may be a better indicator of disease susceptibility (or vaccine response) than chronological age alone. AIM To evaluate the immunogenicity of the 7-valent conjugated pneumococcal vaccine (PCV7) versus 23-valent polysaccharide vaccine (23vPPV) and compare the immune response to four serotypes (4, 6B, 18C and 19F), with respect to age or frailty in an elderly population of previously unvaccinated hospitalized patients. METHOD 241 patients aged 60 years and over, recruited between 16 May 2005 and 20 February 2006, were randomised to 23PPV or PCV7 vaccine. We measured Frailty Index (FI), Barthel index and the MiniMental State. Serotype-specific IgG was measured by ELISA at base line and 6 months after vaccination. Antibody responses were defined by the ratio of post-vaccination to pre-vaccination IgG antibody concentration (poor < 2-fold increase, acceptable > or = 2.0 to 3.99-fold and strong > or = 4.0-fold increase). RESULTS Pre-immunization IgG was generally low and did not differ significantly by age or frailty. Post-immunization, IgG increased to all four serotypes; acceptable or strong response ranged between 29% for (6B) and 57% for (18C). There was no significant difference between the two vaccine types (23PPV versus PCV7). At 6 months post-vaccination, the highest geometric mean IgG concentrations (GMCs) were seen for serotype 19F and the lowest for serotype 4. Although there was some variation by serotype, responses after vaccination were lowest in the most frail or aged subjects. CONCLUSIONS Pneumococcal vaccines are perceived to offer low protection in the frail elderly, but our study showed that the proportion of this vulnerable population with acceptable responses is encouraging. Frailty, as measured by the Frailty Index, appears to be a better predictor of immune response to pneumococcal vaccines than age alone.

Clinical relevance of TLR2, TLR4, CD14 and FcγRIIA gene polymorphisms in Streptococcus pneumoniae infection

Streptococcus pneumoniae is the most common cause of community‐acquired pneumonia and a major cause of morbidity and mortality throughout the world. It has been a major research priority to identify gene polymorphisms responsible for/associated with susceptibility and severity of S. pneumoniae infection to gain a better understanding of host genetic variants and their influence and clinical relevance to pneumococcal infections. In the present study, polymorphisms in several candidate genes, including TLR2‐Arg/Gln753, TLR4‐Asp/Gly299, TLR4‐Thr/Ile399, CD14‐159C/T and FcγRIIA‐R/H131, were examined in 85 children with pneumococcal sepsis as an invasive pneumococcal disease and 409 healthy blood donors as controls. The prevalence of the TLR4‐299/399 polymorphisms was significantly lower in the patient population than in controls (4 vs 11%; P<0.05; odds ratio (OR) 0.3; 95% confidence interval (CI) 0.1–1), while the prevalence of the CD14‐159CC and FcγRIIA‐R/R131 genotypes was significantly higher (35 vs 25%; P<0.05; OR 1.7; 95% CI 1–2.8 and 39 vs 21%; P<0.001; OR 2.5; 95% CI 1.4–4, respectively). Further, only 35% of patients carried either low‐risk genotypes or protective genotypes in contrast to 61% of controls (P<0.0001; OR 2.8; 95% CI 1.7–4.6). We conclude that genetic variability in the TLR4, CD14 and FcγRIIA genes is associated with an increased risk of developing invasive disease in patients who are infected with S. pneumoniae.

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.

FcγRIIA polymorphisms in Streptococcus pneumoniae infection

Invasive pneumococcal disease continues to be a major cause of morbidity and mortality among children and adults worldwide. Effective host defence against Streptococcus pneumoniae depends on immunoglobulin G‐mediated phagocytosis of the bacteria and it has been shown in vitro that the FcγRIIA polymorphism (FcγRIIA‐R131 vs FcγRIIA‐H131) determines the capacity of immunoglobulin G2‐mediated phagocytosis via this receptor. In this study, we evaluated FcγRIIA polymorphisms in children with pneumococcal sepsis and a number of control groups in order to investigate a possible association of FcγRIIA genotypes with Streptococcus pneumoniae infection. The distribution of the genotypes differed in these populations. The frequency of homozygosity for FcγRIIA‐R/R131 in the patients was significantly higher than that in the healthy random donor population (43%vs 21%, P < 0.05). The frequencies of FcγRIIA‐H/H131 were similar among all groups of individuals, while the incidence of the heterozygous FcγRIIA‐R/H131 was lower (35%vs 52%, P < 0.05). Thus, it appears that the FcγRIIA‐H131 polymorphic form, even in the heterozygous form, may be protective for pneumococcal sepsis and children with FcγRIIA‐R/R131 genotype could be more at risk of infection with invasive Streptococcus pneumoniae.

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.

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.

Detection of prion epitopes on PrPc and PrPsc of transmissible spongiform encephalopathies using specific monoclonal antibodies to PrP

Amino acid residues 90–120 of the prion protein (PrP) are likely to be critical for the conversion of PrPc to PrPsc in the transmissible spongiform encephalopathies. We raised 10 monoclonal antibodies against the 90–120 amino acid region, mapped the epitope specificity of these anti‐PrP antibodies, and investigated the expression of epitopes recognized by the antibodies in both PrPc and PrPsc. Four out of five of the anti‐PrP antibodies raised in a prion knockout mouse immunized with the linear peptide of PrP90–120 could detect PrPsc in ‘native’ and denatured forms and PrPc in normal cells, as well as recognize epitopes within PrP93–112 residues. In contrast, the other six anti‐PrP reagents, including five raised from the two knockout mice immunized with conformationally modified PrP90–120 peptide, could detect PrPc and recognize epitopes within PrP93–107 residues. Four of these reagents could also detect denatured PrPsc on western blots but not PrPsc plaques in brain tissue. The results indicate that residues PrP93–102 are exposed in PrPc but are buried upon conversion to the PrPsc isoform. Furthermore, PrP103–107 residues are partially buried in PrPsc while only the PrP107–112 epitope remains exposed, suggesting that the region PrP93–112 undergoes conformational changes during its conversion to PrPsc.

High Prevalence of the CD14-159CC Genotype in Patients Infected with Severe Acute Respiratory Syndrome-Associated Coronavirus

ABSTRACT To investigate whether genetic factors of innate immunity might influence susceptibility and/or progression in individuals infected with SARS, we evaluated the CD14 gene polymorphism in 198 Hong Kong blood donors and 152 Hong Kong severe acute respiratory syndrome (SARS) patients who were previously genotyped for FcγRIIA polymorphisms. The prevalence of the CD14-159CC polymorphism was significantly higher in the patients with severe SARS than in the those with mild SARS or controls (31% versus 15% [mild SARS] or 20% [controls]; mild SARS: P = 0.029; odds ratio, 2.74; 95% confidence interval, 1.15 to 6.57; controls, P = 0.04; odds ratio, 2.41; 95% confidence interval, 1.05 to 5.54), and both CD14-159CC and FcγRIIA-RR131 are risk genotypes for severe SARS-CoV infection.

Identification of genetic polymorphisms that predict responder/non-responder profiles to the RhD antigen.

BACKGROUND Regular plasma donors who produce high titre anti-D immunoglobulin (Ig) are overseen by the Australian Red Cross Blood Service RhD Program. New donors to the program are immunised with small amounts of RhD-positive RBCs, whilst donors who have developed anti-D due to previous RhD-incompatible blood transfusion or pregnancy are boosted with RhD-positive RBCs to maintain a high level of serum anti-D Ig. A significant proportion of primarily immunised individuals do not respond to RhD immunisation and are therefore unnecessarily exposed to the risks involved in RBC sensitisation. STUDY DESIGN AND METHODS We genotyped 184 anti-D donors for ∼9000 immunological and inflammatory genetic polymorphisms on an Affymetrix GeneChip, and validated the results with a High-Resolution Melt analysis assay. We built and validated a predictive logistic regression model using High Responder and Non-Responder anti-D donors that incorporated highly-associated polymorphisms and gender. RESULTS High Responder and Non-Responder profiles in anti-D donors were significantly associated with a shortlist of 13 genetic polymorphisms and sex of the donor. The derivation of a logistic regression model showed an accuracy rate of 92.6% that was subsequently validated as 60.0% with an independent set of donor samples. CONCLUSION This study has developed a logistic regression model and a genotyping assay that can predict the responder profiles of anti-D donors and could potentially be applied to new donors and transfusion-dependent patients in a clinical setting. Additionally, target polymorphisms identified in immunological genes could help to elucidate the immunomodulatory pathways regulating the immune response to the RhD antigen, and to other RBC antigens.

Evidence of heterogeneity in the antibody response against the platelet antigen 3a; recognition of an 11-mer peptide carrying the HPA-3a polymorphic determinant

Background  The immune processes involved in the development of alloantibodies against the human platelet antigens in alloimmune disorders remain unclear. Antibody recognition of the platelet antigens on their respective platelet glycoproteins has been shown to be dependent on glycoprotein conformation. Furthermore, the post‐translational modification of glycoproteins adds complexity to the alloantigenic determinants.