Impact of erythrocyte species on assays for influenza serology.

The influenza viruses have the ability to agglutinate erythrocytes by binding to sialic acid receptors on the host cell. Human influenza viruses preferentially bind to sialic acid linked to galactose by α 2.6 linkage, while avian influenza viruses preferentially bind to sialic acid linked to Gal by α 2.3 linkage. There is a close correlation between the ability of influenza A viruses to agglutinate erythrocytes from different animal species and their receptor specificity. The haemagglutination and haemagglutination inhibition assays are influenced by the species of erythrocytes. To provide an overview of the expression of sialic acid receptors on different erythrocytes, avian (turkey, chicken, pigeon) and mammalian (sheep, horse, human) species have been analysed by flow cytometry. Chicken, turkey and human erythrocytes display both types of linkages. Horse and sheep erythrocytes show almost exclusively α 2.3 Gal linkages, while pigeon erythrocytes express almost exclusively α 2.6 Gal linkages. The erythrocytes from the same avian and mammalian species have been evaluated by haemagglutination and haemagglutination inhibition assays with seasonal and avian strains. Chicken and turkey erythrocytes seem to be the most appropriate for both assays with seasonal influenza strains, in addition to pigeon erythrocytes, particularly for the B strains. In the case of the avian strain, chicken erythrocytes are suitable for haemagglutination assay and horse erythrocytes for haemagglutination inhibition assay. The choice of erythrocytes has a significant impact on the titres measured by both assays.

New candidate vaccines against blood-stage Plasmodium falciparum malaria: prime-boost immunization regimens incorporating human and simian adenoviral vectors and poxviral vectors expressing an optimized antigen based on merozoite surface protein 1.

Although merozoite surface protein 1 (MSP-1) is a leading candidate vaccine antigen for blood-stage malaria, its efficacy in clinical trials has been limited in part by antigenic polymorphism and potentially by the inability of protein-in-adjuvant vaccines to induce strong cellular immunity. Here we report the design of novel vectored Plasmodium falciparum vaccines capable of overcoming such limitations. We optimized an antigenic insert comprising the four conserved blocks of MSP-1 fused to tandemly arranged sequences that represent both allelic forms of the dimorphic 42-kDa C-terminal region. Inserts were expressed by adenoviral and poxviral vectors and employed in heterologous prime-boost regimens. Simian adenoviral vectors were used in an effort to circumvent preexisting immunity to human adenoviruses. In preclinical studies these vaccines induced potent cellular immune responses and high-titer antibodies directed against MSP-1. The antibodies induced were found to have growth-inhibitory activity against dimorphic allelic families of P. falciparum. These vectored vaccines should allow assessment in humans of the safety and efficacy of inducing strong cellular as well as cross-strain humoral immunity to P. falciparum MSP-1.

Influence of ageing on antibody formation in vivo after immunisation with the primary T-cell dependent antigen Helix pomatia haemocyanin.

The in vivo antibody response to the primary T-cell dependent antigen Helix pomatia Haemocyanin (HPH) was studied, in order to detect the possible presence of a humoral immune deficiency in ageing. The IgG subclass distribution of the specific antibodies was also determined. In order to define a dose of HPH which could be used to discriminate between the responsiveness of healthy and immunocompromised individuals, we first established a dose-response curve for this antigen in 60 healthy young volunteers. Their responses were compared with the responses of a group of patients suffering from end stage renal failure. The patients who were treated with haemodialysis showed a significantly lower IgM, IgG and IgA anti-HPH antibody response after immunisation with a dose of 30 micrograms HPH, which could be restored by increasing the antigen dose. Patients treated with continuous ambulant peritoneal dialysis and a group of elderly persons, selected according to the Senieur protocol, showed no impairment of antibody formation after immunisation with 30 micrograms HPH, but in the non-Senieur elderly the anti-HPH antibody response was significantly lower. Furthermore, Senieur and non-Senieur elderly persons showed a diminished IgG2 anti-HPH antibody formation, whereas in the elderly non-Senieur individuals and in the patients with renal insufficiency, IgG1 and IgG3 anti-HPH antibodies were also diminished. This study clearly shows that the so-called age-associated immune deficiency can be the result of disease and is not necessarily due to the ageing process itself.

Reduced IFN-gamma production in elderly people following in vitro stimulation with influenza vaccine and endotoxin.

Cytokine interferon gamma (IFN-gamma) is pivotal in the defence against viruses and intracellular pathogens and an age-related decreased IFN-gamma production may explain the increased infectious disease morbidity and mortality in the elderly. Therefore, we performed a series of clinical experiments evaluating the influence of age and health status on IFN-gamma production following in vitro stimulation with influenza vaccine or endotoxin. Both healthy and frail elderly people produced significantly lower amounts of IFN-gamma following ex vivo stimulation with influenza vaccine or endotoxin. We conclude that ageing is accompanied by a decreased capacity to produce IFN-gamma. This may explain the increased incidence and case-fatality caused by viruses and intracellular pathogens in the elderly.

Innate cytokine profile in patients with complex regional pain syndrome is normal.

Complex regional pain syndrome (CRPS) is a disabling disease characterized by the classic symptoms and signs of inflammation. In this study we investigated the innate cytokine profile in patients with CRPS to determine a possible role of the immune system in the pathophysiology of CRPS. The cytokine profile before and after lipopolysaccharide and thrombin stimulation was determined in 26 severely affected CRPS patients and 20 healthy controls. No difference in the production of pro- and anti- inflammatory cytokines between patients and controls was found. Hence, our results do not support a role of genetic factors responsible for the cytokine profile in the pathophysiology of CRPS. These findings encourage further investigations of mechanisms responsible for neurogenic-induced inflammation.

Influenza vaccination in elderly people.

Influenza is an important cause of morbidity and mortality in the elderly. Influenza vaccine has been shown to successfully reduce influenza- and pneumonia-associated hospitalizations and deaths, but the antibody induction by influenza vaccines is not always optimal in the elderly. The lower serological efficacy of influenza vaccines that is often observed in the elderly may be due to a multitude of factors. Here we will discuss some of these factors. These include health status and previous exposures to influenza viruses. In addition, we will discuss possibilities to improve antibody responses to influenza vaccination.

Interaction of indomethacin with cytokine production in whole blood. Potential mechanism for a brain-protective effect.

Both Alzheimer's disease and vascular dementia are featured by inflammatory responses and it is known that non-steroidal anti-inflammatory drugs (NSAIDs) decrease the risk and severity of these diseases. To study the effect of NSAIDs on PGE2 levels and pro- and anti-inflammatory cytokine levels in the whole blood assay, blood samples from 23 elderly persons aged 85 years were stimulated with thrombin or LPS as primary stimulus. Indomethacin was added in concentrations ranging from 0.4 to 16 microg/ml and acetylsalicylic acid was added to in concentrations ranging from 0.5 to 8.0 microg/ml. Indomethacin abrogated thrombin- and LPS-induced PGE2 production at all concentrations tested. In addition, indomethacin reduced the production of thrombin-induced IL-6 and IL-10 (p<0.05) at physiological concentrations. Indomethacin reduced the production of LPS-induced IL-6, IL-1 beta and IL-10 (p<0.05) at the highest indomethacin concentration tested. Similar results were obtained upon incubation with acetylsalicylic acid. It is concluded that indomethacin may reduce the thrombin-induced inflammatory reaction by decreasing IL-6 through inhibition of PGE2 synthesis. This IL-6 reduction may be relevant for the ability of indomethacin to reduce the risk of Alzheimer's disease. However, the decrease in IL-10 production due to indomethacin suggests a more inflammatory state.

Patients with Alzheimer's disease display a pro-inflammatory phenotype.

BACKGROUND: Inflammation plays a pivotal role in amyloid plaque progression thereby contributing to Alzheimer's disease-related neurodegeneration. We hypothesized that patients with Alzheimer's disease have an innate pro-inflammatory phenotype, as compared to control subjects without dementia. METHODS: Patients with a diagnosis of probable Alzheimer's disease (n=12) and control subjects without signs of dementia (n=18) were enrolled. Whole blood samples were stimulated ex vivo with endotoxin under standard conditions. Cytokine levels were assessed by ELISA and compared by Mann-Whitneyll-test after log transformation. RESULTS: Patients with Alzheimer's disease had seven- to ten-fold higher IL-1beta production relative to the amount of IL-10 both at the low (p=0.006) and high concentration of endotoxin (p=0.007). Subjects who display a pro-inflammatory phenotype as defined by a high IL-1beta/IL-10 ratio had 13.0-fold higher odds (95% CI: 2.1-82) to have dementia. CONCLUSION: The data support the hypothesis that a pro-inflammatory phenotype contributes to the development of Alzheimer's disease.

Dose-dependent antibody response to influenza H1N1 vaccine component in elderly nursing home patients.

The effects of an increased antigen dose on HI, IgG, IgA, and IgM antibody responses to influenza A/Taiwan/1/86 (H1N1) were investigated in 92 elderly nursing-home residents (mean age 81 years) and 104 young subjects (mean age 20 years). At a standard 10-microg dose, HI and IgG titer rises were lower in the elderly. HI titers did not improve at higher vaccine dosages. By contrast, influenza-specific IgG and IgA antibody responses were dose dependent in elderly subjects, but not in young. In the young subjects, IgM antibody responses were dose dependent. The improved antibody responses in the elderly as observed in IgG and IgA were not reflected in the HI response. Therefore, the evaluation of antibody production by HI only may lead to an underestimate of the immune response in elderly people.

Idiopathic senile gait disorders are signs of subclinical disease.

OBJECTIVES: To evaluate survival and causes of death in subjects with idiopathic senile gait disorders. DESIGN: A population-based longitudinal study. SETTING: Survival analysis of the oldest old within the Leiden 85-plus Study. PARTICIPANTS: We distinguished three different groups according to their gait: subjects with a normal gait (n = 25), subjects with senile gait disorders (n = 14), and subjects with gait disorders due to known disease (n = 87). The mean age was 90 years in all groups (range 87 to 97 years). MEASUREMENTS: The risk of all cause mortality and cardiovascular mortality was estimated over 5 years of follow-up in a Cox-proportional hazards model, adjusted for age and sex. RESULTS: Eighty-nine of 126 subjects died during follow-up. Mean survival differed among the three groups (P log-rank = .01). All cause mortality risk was increased in subjects with senile gait disorders compared with subjects with a normal gait (RR = 2.8; 95% CI, 1.1-7.3, P = .03) and was similar to subjects with gait disorders caused by known disease (RR = 1.2; 95% CI: .6-2.5, P = .6). Mortality caused by cardiovascular disease also differed among the three groups (P log-rank = .03). The risk of cardiovascular death in subjects with senile gait disorders was twofold greater than in subjects with a normal gait (RR = 2.1; 95% CI, 0.4-10.3). CONCLUSIONS: Senile gait disorders are related to subclinical, perhaps cardiovascular, disease. Senile gait disorders should not be accepted as an inevitable, benign concomitant of the normal aging process.

Heritability estimates of innate immunity: an extended twin study.

Cytokines are key players in numerous inflammatory processes. Demonstration of a heritable component in the variation of cytokine production would indicate that simultaneous occurrence of conditions might be caused by a heritable inflammatory characteristic. We applied an extended twin study approach to assess heritability estimates of interleukin (IL)-1beta, IL-1ra, IL-10, IL-6, and TNF-alpha production capacity after ex vivo stimulation with lipopolysaccharide. Cytokine production capacity was assessed in 42 monozygotic pairs, 52 dizygotic pairs, one trizygotic triplet, 33 single twins, and 83 additional siblings. Heritability estimates were derived from variance decomposition models using maximum likelihood estimation. For all cytokines, over 50% of the variance was genetically determined. IL-1ra and TNF-alpha had the lowest heritability estimate of 53%. Estimates for IL-6 and IL-10 were 57 and 62%, respectively. IL-1beta had the highest estimate of 86%. We conclude that the production of cytokines is under tight genetic control.

The effect of geographic origin on the frequency of HLA antigens and their association with ageing.

The association between HLA antigens and ageing is not clear. Ageing in women was associated with B40 and DR5 in a recent study, but other studies yielded conflicting results. In none of the studies, however, did the young and elderly samples originate from the same homogeneous population. Homogeneity is dependent on geographic origin. The aim of this study was to investigate whether differences in geographic origin between age groups could explain the age-associated differences in the frequencies of B40 and DR5. The authors used the new design of a 'birth-place-restricted comparison' in which the origin of all subjects was ascertained. The total study population comprised 1010 young women aged 25-40 years and 660 elderly women aged 85 years and older. The 'birth-place-restricted comparison' included 66 young and 285 elderly women from one geographic area (Leiden, the Netherlands). Men were not included because ageing in men was not associated with HLA antigens in a recent study. In the total population, the frequency of B40 in young women of different origin varied between 16 and 28%, and the frequency of DR5 between 11 and 23%. Similar differences were observed in the elderly women. In the 'birth-place-restricted comparison', the frequency of B40 was 15% in the young women and 11% in the elderly women (difference 4%, 95% confidence interval, -5 to 13%). The frequency of DR5 was 20% in the young women, and 28% in the elderly women (difference 8%, 95% confidence interval, -4 to 19%). Thus, marked differences in HLA antigen frequency were found between populations of various geographic origins. Definition and ascertainment of the target population are therefore necessary in genetic studies of ageing. In such a 'birth-place-restricted comparison', the authors confirmed that ageing in women was negatively associated with HLA-B40 and positively associated with HLA-DR5.

Correlation between the antibody response to influenza vaccine and helper T cell subsets in healthy aging.

To investigate the effects of the altered composition of the helper T cell compartment in ageing on the humoral response to influenza vaccine, we investigated correlations between helper T cell subsets and anti-influenza antibody responses in 23 JUNIEUR healthy young and 41 SENIEUR healthy elderly subjects. Naive helper T cell numbers (CD4+ CD45RA+) were negatively correlated with antibody production to two of the four strains investigated in JUNIEURS only. By contrast, memory helper T cell numbers (CD4+CD45ROhi) were positively correlated with in vivo IgG antibody titres to three of the four vaccine strains. Age-related differences in the composition of the helper T cell compartment, however, did not explain the lower IgG antibody response that was observed to two of the four vaccine strains examined.

Altered antibody response to influenza H1N1 vaccine in healthy elderly people as determined by HI, ELISA, and neutralization assay.

To determine the influence of ageing per se as well as of priming histories on the antibody response to influenza vaccination, haemagglutination inhibition (HI), ELISA IgG, IgA, IgM and neutralizing antibody titres were studied in 43 healthy young subjects (mean age 23 years) and 55 healthy elderly people (mean age 79 years). The HI and ELISA lgG responses to the A/Guizhou/54/89 strain (H3N2) for which both the young and the elderly had similar priming histories were equal. By contrast, the HI and IgG responses to A/Taiwan/1/86 (H1N1), where the priming histories were different, were lower in the elderly (P < 0.05). Influenza-specific IgA responses in the elderly tended to be higher for all vaccine strains. Influenza-specific postvaccination IgM titres were similar or tended to be higher in the elderly. A subgroup of elderly subjects (18%) who did not express HI activity to the A/Taiwan/1/86 (H1N1) vaccine strain, reacted in the HI assay with the closely related A/Singapore/6/86 (H1N1) strain. These elderly people, however, produced lgG antibodies which neutralized A/Taiwan/1/86 virus in vitro. It is concluded that the elderly are capable of mounting antibody responses similar to those observed in the young. Moreover, the observed age-related differences in antibody responses to H1N1 strains are probably not due to ageing of the immune system itself, but are determined by differences in priming histories.

Annually repeated influenza vaccination improves humoral responses to several influenza virus strains in healthy elderly.

The benefit of annually repeated influenza vaccination on antibody formation is still under debate. In this study the effect of annually repeated influenza vaccination on haemagglutination inhibiting (HI) antibody formation in the elderly is investigated. Between 1990 and 1993 healthy young and elderly, both selected by the SENIEUR protocol, were vaccinated consecutively with commercially available influenza vaccines. The elderly had a lower HI antibody response after one vaccination as compared to the young against the A/Taiwan/1/86 (HINI), B/Yamagata/16/88 and B/Panama/45/90 strains. Annually repeated vaccination did not result in a decrease of the HI antibody titres against the A and B vaccine strains in both age groups. Moreover, the elderly had a significantly higher HI titre against the B strains after the second vaccination as compared to the first, resulting in comparable HI titres for young and elderly. Thus, annually repeated vaccination has a beneficial effect on the antibody titre against influenza virus and can contribute to a better antibody-response in the elderly.