Safety and immunogenicity of an inactivated split-virus influenza A/H1N1 vaccine in healthy children from 6 months to <18 years of age: A prospective, open-label, multi-center trial
Chi Eun OhJina LeeJin Han KangYoung-Jin HongYun Kyung KimHee Jin CheongYoung-Joo AhnSang‐Hoon KimHoan Jong Lee
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Hemagglutination assay
Regimen
Antibody titer
An ELISA-based method to estimate hemagglutination-inhibition (HI) titer was developed. Subtype specificity was obtained by using purified H1 and H3 hemagglutinin antigens. Using the linear relation that exists between ELISA and HI methods, regression lines for H1N1- and H3N2-monospecific porcine antisera were constructed. Approximation of actual HI titer could be obtained from insertion of ELISA values into the appropriate regression line. The HI estimations were within 50% of the actual measured HI value 84% of the time. In young pigs that had suckled immune sows, use of this ELISA revealed estimated HI titer > 320 at 2 and 4 weeks of age. After a typical farm outbreak of influenza A/swine (H1N1), estimated HI titers remain high for 4 to 6 months. Sub-type-specific estimation of the distribution frequency of positive influenza A (H1N1 or H3N2) results for sera from swine in regional herds indicated that 31.3 and 7.4% of the swine tested were positive (HI > 41) for H1N1 and H3N2, respectively. From these observations, we conclude that in many circumstances, an ELISA-based HI estimation method could be used as a substitute for the HI test.
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The rate of decline of antibody titers to influenza following infection can affect results of serological surveys, and may explain re-infection and recurrent epidemics by the same strain. We followed up a cohort who seroconverted on hemagglutination inhibition (HI) antibody titers (≥4-fold increase) to pandemic influenza A(H1N1)pdm09 during a seroincidence study in 2009. Along with the pre-epidemic sample, and the sample from 2009 with the highest HI titer between August and October 2009 (A), two additional blood samples obtained in April 2010 and September 2010 (B and C) were assayed for antibodies to A(H1N1)pdm09 by both HI and virus microneutralization (MN) assays. We analyzed pair-wise mean-fold change in titers and the proportion with HI titers ≥ 40 and MN ≥ 160 (which correlated with a HI titer of 40 in our assays) at the 3 time-points following seroconversion. A total of 67 participants contributed 3 samples each. From the highest HI titer in 2009 to the last sample in 2010, 2 participants showed increase in titers (by HI and MN), while 63 (94%) and 49 (73%) had reduction in HI and MN titers, respectively. Titers by both assays decreased significantly; while 70.8% and 72.3% of subjects had titers of ≥ 40 and ≥ 160 by HI and MN in 2009, these percentages decreased to 13.9% and 36.9% by September 2010. In 6 participants aged 55 years and older, the decrease was significantly greater than in those aged below 55, so that none of the elderly had HI titers ≥ 40 nor MN titers ≥ 160 by the final sample. Due to this decline in titers, only 23 (35%) of the 65 participants who seroconverted on HI in sample A were found to seroconvert between the pre-epidemic sample and sample C, compared to 53 (90%) of the 59 who seroconverted on MN on Sample A. We observed marked reduction in titers 1 year after seroconversion by HI, and to a lesser extent by MN. Our findings have implications for re-infections, recurrent epidemics, vaccination strategies, and for cohort studies measuring infection rates by seroconversion.
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Objectives To prepare a mask from extracts of Isatis leaf and root, filter a solution of influenza virus through it, and then detect viral activity in the filtrate in order to evaluate the mask's effectiveness against the influenza virus. Methods A solution of H1N1 influenza virus with a hemagglutination titer of 2-12 was filtered through the drug mask. After the filtrate was collected, the hemagglutination titer of the viral solution was determined by performing a hemagglutination test. Then the filtrate was inoculated into chick embryos. The hemagglutination test was performed with allantoic fluid collected after 48 h. Viral activity in the filtrate was analyzed via the hemagglutination titer and EID50. Results Compared to the unfiltered solution of influenza virus with a hemagglutination titer of 2-12, the hemagglutination titer of the filtrate was 2-3 (P0.01). The hemagglutination titer of allantoic liquid was 2-6 after inoculation with filtrate (P0.01). Compared to the unfiltered H1N1 solution with an EID50 of 10-4.95/0.1ml, the filtrate had an EID50 of 10-2.10/0.1ml (P0.01). Conclusion The influenza virus lost more than 93% of its infectivity after it was filtered through a mask made from extracts of Isatis leaf and root. This suggests that the drug mask could be used to prevent infection with the influenza virus.
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This study was conducted to investigate the similarity between hemagglutination inhibition (HI) test and enzyme-linked immunosorbent assay(ELISA) titers and sample to positive ratio (S/P ratio) of Newcastle disease(ND) virus. To perform this study, the 372 sera of broiler chicks and 120 sera of layers and breed chicks were collected from slaughter house and farms, respectively. As a result of HI test out of different chicks, the positive percentage of ND antibody titer of broiler, layer and breeder, when a standard positive HI titer were '2', was 84.4%, 100% and 100%, respectively. The positive percentage of ND antibody titer by ELISA was shown 38.4%, 100% and 100% and S/P ratio were also shown 81.5%, 98.2% and 99.2%, respectively. The results of comparative survey with same sera by two experimental methods were as follows; In low HI titer, ELISA titer was not similar to HI titer, but S/P ratio was similar to it. In high HI titer, ELISA titer was not similar to HI titer. Therefore, HI titer was more similar to S/P ratio than ELISA titer.
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OBJECTIVE To investigate the anti-influenza A3 effect of Qing Re He Ji(QRHJ)mixture.METHODS The techniques of chick embryo culture were used for evaluating antiviral activity of serum from the Wistar rats dosed with QRHJ by hemagglutination assay with the influenza virus hemagglutination titer as index.RESULTS The first,second,third and fouth hour's serum of the Wistar rats after oral administration of QRHJ by 24 g·kg-1 dose had antiviral effect.The inhibition rates(%)of hemagglutination titer were 86.37,82.32,80.72 and 72.74,respectively.The first,second and third hour's serum of the Wiistar rats after oral administration of QRHJ by 12 g·kg-1dose had antiviral effect.The inhibition rates(%)of hemagglutination titer were 71.53,67.58 and 66.14.QRHJ was found to be an inhibitor of influenza A3 virus in a concentration-dependent manner.CONCLUSION QRHJ has significant effect on influenza virus type A3 in the chick embryo.
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Determination of influenza-specific antibody titers is commonly done using the hemagglutination inhibition assay (HAI) and the viral microneutralization assay (MN). Both assays are characterized by high intra- and inter-laboratory variability. The HAI assay offers little opportunity for standardization. For the MN assay, variability might be due to the use of different assay protocols employing different readouts. We therefore aimed at investigating which of the MN assay readout methods currently in use would be the most suitable choice for a standardized MN assay that could serve as a substitute for the HAI assay. For this purpose, human serum samples were tested for the presence of influenza specific neutralizing antibodies against A/California/7/09 H1N1 (49 sera) or A/Hong Kong/4801/2014 (50 sera) using four different infection readout methods for the MN assay (cytopathic effect, hemagglutination, ELISA, RT qPCR) and using the HAI assay. The results were compared by correlation analysis and by determining the level of agreement before and after normalization to a standard serum. Titers as measured by the 4 MN assay readouts showed good correlation, with high Person's r for most comparisons. However, agreement between nominal titers varied with readouts compared and virus strain used. In addition, Pearson's correlation of MN titers with HAI titers was high but agreement of nominal titers was moderate and the average difference between the readings of two assays (bias) was virus strain-dependent. Normalization to a standard serum did not result in better agreement of assay results. Our study demonstrates that different MN readouts result in nominally different antibody titers. Accordingly, the use of a common and standardized MN assay protocol will be crucial to minimize inter-laboratory variability. Based on reproducibility, cost effectiveness and unbiased assessment of results we elected the MN assay with ELISA readout as most suitable for a possible replacement of the HAI assay.
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Objective:To investigate the Immunogenicity of VP2 hydrophilic coding-region of canine parvovirus and lay foundation for further study of Subunitvaccine.Method:Protein analysis software-PROTEAN was used to find VP2 major antigenic epitopes according to hydrophile and antigen character of VP2 amino acids and then the corresponding region of nucleotide was amplified by PCR and cloned into prokaryotic expression vector pQE-31.After transformation,the recombinant protein was analyzed by isopropy1β-D-1 thiogalactopyranoside(ITPG) induction.Finally,mice were immunized with VP2S and the antibody were measured by hemagglutination inhibition(HI) assay.Result:The hydrophilic and antigenic region from 293 to 520 amino acids of the VP2 protein of canine parvovirus,called VP2S,was located.After amplification the prokaryotic expression vector pQE-31-VP2S was obtained.The protein with molecular weight of 29kD,were detected in the lysates of the recombinant E.coli by IPTG induction.Western-blotting assay showed that the recombinant proteins were recognized by CPV antiserum.And VP2S-immunized mice appeared hemagglutination inhibition(HI) antibody compared to the control.which demonstrated the VP2S had good immunogenicity.Conclusion:These results indicated that the VP2S had good immunogenicity.
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Porcine parvovirus
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We aimed to determine antibody titers at six months and their percentage change from three to six months after the second dose of the BNT162b2 coronavirus disease 2019 (COVID-19) mRNA vaccine (Pfizer/BioNTech) and to explore clinical variables associated with titers in Japan.We enrolled 365 healthcare workers (250 women, 115 men) whose three-month antibody titers were analyzed in our previous study and whose blood samples were collected 183 ± 15 days after the second dose. Participant characteristics, collected previously, were used. The relationships of these factors with antibody titers at six months and percentage changes in antibody titers from three to six months were analyzed.Median age was 44 years. Median antibody titer at six months was 539 U/mL. Older participants had significantly lower antibody titers (20s, 752 U/mL; 60s-70s, 365 U/mL). In age-adjusted analysis, smoking was the only factor associated with lower antibody titers. Median percentage change in antibody titers from three to six months was -29.4%. The only factor significantly associated with the percentage change in Ab titers was not age or smoking, but sex (women, -31.6%; men, -25.1%).The most important factors associated with lower antibody titers at six months were age and smoking, as at three months, probably reflecting their effect on peak antibody titers. However, the only factor significantly associated with the attenuation in Ab titers from three to six months was sex, which reduced the sex difference seen during the first three months. Antibody titers may be affected by different factors at different time points.
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