Particle Agglutination Antibody Research Articles

Increasing seroprevalence but waning herd immunity against measles after elimination: Longitudinal seroepidemiology of measles in Osaka Prefecture, Japan, 2003–2020

Japan is one of the countries conducting longitudinal serosurveillance of vaccine-preventable diseases. We conducted surveillance of the local measles-specific antibody titer, calculated the effective reproduction number (Re), and compared data of four terms: term 1, 2003–2006 (before the introduction of the second shot of measles-containing vaccine); term 2, 2007–2010 (early term toward measles elimination); term 3, 2011–2014 (later term toward measles elimination); and term 4, 2015–2020 (after elimination of measles in Japan). Approximately 250 sera from volunteers aged 0 to ≥ 40 years were collected and examined for measles-specific IgG using the gelatin particle agglutination (PA) method annually from 2003 to 2020. Seroprevalence and the geometric mean of the PA antibody titer were examined by term. Re was calculated using the age-dependent proportion immune and contact matrix for each term. Of the 4,716 sera, 886 in term 1, 1,217 in term 2, 1,069 in term 3, and 1,544 in term 4 were collected. The seroprevalence gradually increased from term 1 (88.3% CI 86.0–90.3) to term 4 (95.7% CI 94.6–96.7), and the seroprevalence of term 1 was significantly lower than those of other terms (Fisher’s exact test, p < 0.001), with PA titer ≥ 16 as positive. By contrast, PA antibody titers significantly decreased from term 1 (median 1,024) to term 4 (median 256) (Mann–Whitney U test, p < 0.001). With the protection level (PA titer ≥ 128 and ≥ 256) as positive, Re gradually increased from term 1 (1.8 and 2.3) to term 4 (2.5 and 4.8, respectively). Waning levels of measles antibodies potentially increase the measles susceptibility in Osaka, Japan. This trend might imply a limitation of vaccine-induced immunity in the absence of a natural booster for wild strains after measles elimination. This study provides a cue for maintaining continuous measles elimination status in the future.

Immunochromatography test for rapid diagnosis of Mycoplasma pneumoniae infection.

The sensitivity and specificity of a new rapid Mycoplasma pneumoniae antigen immunochromatography (IC) test, DK-MP-001, were determined using particle agglutination (PA) antibody response and loop-mediated isothermal amplification (LAMP) gene detection as the gold standard. Of 165 patients, 59 were diagnosed with M. pneumoniae infection based on a ≥fourfold rise of serum PA antibody during the course of the illness. Of the first visit swabs, 60 were positive for M. pneumoniae on LAMP, and 49 were positive for M. pneumoniae antigen on IC test. Compared with PA antibody and LAMP, the sensitivity/specificity of the IC test were 81.4% (48/59) and 99.1% (105/106); and 81.7% (49/60) and 100% (105/105), respectively. IC test detected antigen in pharyngeal swabs more sensitively than in nasal swabs for the same subjects (P<0.05). The IC test performs well enough to be used with pharyngeal swabs at the first examination.

Measles elimination and immunisation: national surveillance trends in Japan, 2008-2015.

Measles elimination relies on vaccination programmes. In Japan, a major outbreak started in 2007. In response, 5-year two-dose catch-up vaccination programme was initiated in April 2008 for children 13-16-years-old. In this study, we analysed the epidemic curves, incidence rates for each age group, virus genotype, vaccination coverage and ratio of measles gelatin particle agglutination (PA) antibody using surveillance data for 2008-2015. Monthly case counts markedly decreased as vaccination coverage increased. D5, which is the endemic virus type, disappeared after 2011, with the following epidemic caused by imported viruses. Most cases were confirmed to have a no-dose or single-dose vaccination status. Although the incidence rate among all age groups ⩾5-years-old decreased during the study period, for children <5-years-old, the incidence rate remained relatively high and increased in 2014. The ratio of PA antibody (⩾1:128 titres) increased for the majority of age groups, but with a decrease for specific age groups: the 0-5 months and the 2-4, 14, 19 and most of the 26-55- and the 60-year-old groups (-1 to -9%). This seems to be the result of higher vaccination coverage, which would result in decreasing natural immunity booster along with decreasing passive immunity in infants whose mothers did not have the natural immunity booster. The 20-29- and 30-39-year-old age groups had higher number of cases, suggesting that vaccination within these age groups might be important for eliminating imported viruses.

学校教職員における麻疹の罹患歴，接種歴，抗体保有状況，および効果的ワクチン接種方式の検討

To determine an efficient measles vaccination program for school teachers, we studied knowledge about measles history, immunization, and immunity status among 269 school teachers in Ichihara City in 2009. We found that (1) many are uncertain about disease and immunization history, with neither history related to the immunity status of neutralizing antibody titer (NT), (2) particle agglutination (PA) and enzyme immunoassay (EIA) testing have replaced NT in commercial laboratories, but persons having antibodies fewer than 8-fold of the NT titer as a sensitivity desigration for measles, and 11 false-positive immunity results are indicated in PA testing (cutoff: 256-fold) and 140 false-positive sensitivity results in EIA testing (cutoff: 16.0 EIA), and (3) sensitivity cases are 7.1% in the naturally infected generation born before 1977 and 23.7% in the vaccinated generation born after 1978. Given "herd" immunity, we concluded that all vaccinated-generation persons should be administered additional vaccination regardless of sensitivity due to history, immunization, and PA or EIA antibody testing.

Four cases of arthritis associated with Mycoplasma pneumoniae infection

Mycoplasma pneumoniae infection is diagnosed commonly by marked elevation of serum antibodies, but this requires several days and consequently M. pneumoniae infection might be overlooked in some cases. Recently an ImmunoCard Mycoplasma rapid diagnosis test (IC) has been developed and used clinically. One of the advantages of this diagnosis test is that clinicians can recognize the infection by a single administration at the beginning of treatment. A total of 1033 children aged 1-15 years (average 2.0 years) were examined. The diagnosis of M. pneumoniae infection was made mainly on the basis of a positive reaction to the IC. Also where possible, particle agglutination (PA) was performed as a confirmatory test. Diagnosis was made on the basis of a fourfold or greater rise in the PA antibody titer by paired sera or an initial single PA titer >1:320. Arthritis was diagnosed mainly on clinical symptoms. Additionally, ultrasonography (US) was conducted to confirm arthritis. In using US, arthritis was defined as an enlargement of the low echoic section or fluid retention inside the articular capsule. IC was used in 1033 patients and results were positive in 348 (33.6%). Of these 348, there were 70 cases of pneumonia (20.1%) and four cases of arthritis (1.1%). IC was positive in all of the cases of arthritis, and in two of the four arthritis patients the PA titers were also useful for diagnoses. In three of four cases, US was performed and lesions were observed in two of three cases. Three of the four arthritis patients were infants and only one of these three had pneumonia. Using IC as a screening test, occult M. pneumoniae infections were discovered that would otherwise have been overlooked. These included two patients with US-proved arthritis. Arthritis in the absence of pneumonia may not be an unusual manifestation in infants infected by this organism.

麻疹ゼラチン粒子凝集 (PA) 抗体の特性-中和 (NT) 抗体及び血球凝集抑制 (HI) 抗体との比較並びにIgG avidityとの関連

Changes in gelatin particle agglutination (PA), hemagglutination inhibition (HI), and neutralization (NT) antibodies were compared using sera from 124 individuals collected between 3 weeks and 10 years after measles vaccination, and the relationship between these changes and IgG avidity was studied. PA, HI, and NT antibodies peaked 4-5 months after vaccination. The rate of increase in mean antibody titer from 0-1 months after vaccination to peak levels was 1.7-fold for NT, 1.5-fold for HI, and 7.4-fold for PA antibodies. Peak mean antibody titer was 2(11.8) for PA, 2(6.7) for NT and 2(6.7) for HI antibodies. After peaking PA antibodies changed in parallel with NT and HI antibody titers, and correlated strongly with both antibodies (r = 0.801 and 0.840). In contrast, NT and HI antibodies were consistent throughout the period. IgG avidity increased for 4-5 months following vaccination, peaking at 45%, and remaining constant at 40-50% for the next 10 years. PA antibody is strongly influenced by IgG avidity, unlike NT and HI antibodies. Due to the effects of IgG avidity, PA antibodies increase more significantly than NT and HI antibodies as IgG antibodies mature following vaccination, resulting in a weak correlation between PA and NT or HI antibodies. Following the increase in IgG avidity to maturation, PA antibodies correlated strongly with NT and HI antibodies. PA assay detected IgM antibodies against measles virus more efficiently than the NT test. The PA assay thus differs from conventional, commonly used NT and HI assays. PA assay is simple and rapid, making it very useful for detecting measles antibodies provided that its unique features are taken into accounts.

妊婦における麻疹中和抗体価, HI抗体価, PA抗体価の相関と各測定法の発症予防レベル

When measles antibody levels among pregnant women were measured with measles hemagglutinin inhibition (HI), 31% of subjects had negative HI antibody titers. When the same blood samples were tested with measles gelatin particle agglutination (PA) and neutralizing (NT), the percentages of those with negative antibody levels were 1% and 3%. We conducted the correlation between antibody titers measured by the three types of titration. Correlation between NT and HI antibody titers higher than 1:8 and that between NT and PA antibody titers were good, but 81% of subjects whose HI antibody titer was below 1:8 and all women with HI antibody of 1:8 were found to have NT antibody titer higher than 1:4. NT antibody titer higher than 1:4 was found in 95% of women having PA antibody titer of 1:256 and in 99% of those with PA antibody titer of 1:512. Based on the relationships to measles NT antibody level, the majority of subjects with HI antibody titer higher than 1:8 or PA antibody level higher than 1:512 was reasonably assumed to be protected against clinical measles. PA seemed superior to HI in finding subjects with insufficient immunity against measles, because the former detects weak immunity more efficiently than the latter.

Measles sero-surveillance during mass immunisation campaign in Malawi.

To determine age-specific measles antibody prevalence and serological response to vaccination during the first mass campaign against measles in Malawi. Cross-sectional study using a questionnaire and a serological particle agglutination (PA) test. Two health centres in Salima district, central Malawi during the national measles immunisation week, 1998. Two hundred forty six under-five year old children. Seventy four per cent of enrolled children (95% confidence interval, 69-80%) were measles PA antibody positive at the vaccination. The antibody positive rate was 17.4% in children aged 8-12 months and gradually increased up to 90% by four years-old, while the age-specific geometric mean titers (GMTs) in 48-59 months-old group were significantly lower than those in 24-35 months-old group, suggesting antibody waning after previous vaccination (p = 0.0047). Two hundred and thirty follow up specimens were obtained eight weeks after the vaccination. The sero-conversion rate was 100% in 58 children sero-negative at the vaccination and the GMTs in 172 children seropositive at the vaccination were significantly increased (p < 0.001). These results indicated that the first national measles immunisation campaign successfully immunised the enrolled children or gave a booster response of antibody levels. It was also confirmed that the PA test was easy to perform and most suitable for the field condition in developing countries.