Serological Response to the 2009 Pandemic Influenza A (H1N1) Virus for Disease Diagnosis and Estimating the Infection Rate in Thai Population

BACKGROUND: Individuals infected with the 2009 pandemic virus A(H1N1) developed serological response which can be measured by hemagglutination-inhibition (HI) and microneutralization (microNT) assays. METHODOLOGY/PRINCIPAL FINDINGS: MicroNT and HI assays for specific antibody to the 2009 pandemic virus were conducted in serum samples collected at the end of the first epidemic wave from various groups of Thai people: laboratory confirmed cases, blood donors and health care workers (HCW) in Bangkok and neighboring province, general population in the North and the South, as well as archival sera collected at pre- and post-vaccination from vaccinees who received influenza vaccine of the 2006 season. This study demonstrated that goose erythrocytes yielded comparable HI antibody titer as compared to turkey erythrocytes. In contrast to the standard protocol, our investigation found out the necessity to eliminate nonspecific inhibitor present in the test sera by receptor destroying enzyme (RDE) prior to performing microNT assay. The investigation in pre-pandemic serum samples showed that HI antibody was more specific to the 2009 pandemic virus than NT antibody. Based on data from pre-pandemic sera together with those from the laboratory confirmed cases, HI antibody titers ≥ 40 for adults and ≥ 20 for children could be used as the cut-off level to differentiate between the individuals with or without past infection by the 2009 pandemic virus. CONCLUSIONS/SIGNIFICANCE: Based on the cut-off criteria, the infection rates of 7 and 12.8% were estimated in blood donors and HCW, respectively after the first wave of the 2009 influenza pandemic. Among general population, the infection rate of 58.6% was found in children versus 3.1% in adults

Early Diagnosis of Leptospirosis by Immunoglobulin M Immunoblot Testing▿

There is an urgent need for the development of serodiagnostic approaches with improved sensitivity for patients with acute leptospirosis. Immunoblots were performed on 188 sera collected from 74 patients with laboratory-confirmed early leptospiral infection to detect immunoglobulin M (IgM) antibodies to antigens pooled from 10 leptospiral strains prevalent in Thailand. Sera from patients with other febrile diseases served as controls. IgM reactivity to seven distinct antigens, with apparent molecular masses of 14 to 18, 19 to 23, 24 to 30, 32, 35/36, 37, and 41/42 kDa, was observed. The low-molecular-mass 14- to 18-kDa band was the most frequently detected antigen, being recognized in sera from 82.4% of patients during the first 3 days after the onset of symptoms. We evaluated the accuracy of the IgM immunoblot (IgM-IB) test by using reactivity to the 14- to 18-kDa band and/or at least two bands among the 19- to 23-, 24- to 30-, 32-, 35/36-, 37-, and 41/42-kDa antigens as the diagnostic criterion. The sensitivities of the IgM-IB test and the microscopic agglutination test (MAT) were 88.2% and 2.0%, respectively, with sera from patients 1 to 3 days after the onset of symptoms. In contrast, the IgM-IB test was positive with only 2/48 (4.2%) sera from patients with other febrile illnesses. The high sensitivity and specificity of the IgM-IB test for acute leptospirosis would provide greatly improved diagnostic accuracy for identification of patients who would benefit from early antibiotic intervention. In addition, the antigens identified by the IgM-IB test may serve as components of a rapid, accurate, point-of-care diagnostic test for early leptospirosis

Comparison of immunogenicity between intradermal and intramuscular injections of repeated annual identical influenza virus strains post-pandemic (2011-2012) in COPD patients

We compared the antibody responses and persistence of the reduced-dose, 9 µg hemagglutinin (HA)/strain intradermal (ID) injection via the Mantoux technique and the 15 μg HA/strain intramuscular (IM) injection of the repeated annual identical trivalent, inactivated, split-virion vaccine 2011–2012 in chronic obstructive pulmonary disease (COPD) patients. Eighty patients were randomized to ID (n = 41) and IM (n = 39) groups. Four weeks post-vaccination, the antibody responses of the two groups were similar; those for influenza A(H1N1)pdm09 and influenza A(H3N2)–but not influenza B–met the criteria of the Committee for Proprietary Medicinal Products (CPMP). The antibody responses for influenza A(H1N1)pdm09 rapidly declined in both groups, especially with the ID injection, whereas those for influenza A(H3N2) maintained above the CPMP criteria throughout 12 months post-vaccination. The geometric mean titres for influenza A(H1N1)pdm09 persisted above the protective threshold (≥ 40) until 6 months post-vaccination in both the ID and IM groups. The seroprotection rates of the ID and IM groups were above 60% until 3 months and 6 months post-vaccination, respectively. In conclusion, the 9 μg HA/strain ID injection of vaccine 2011–2012 elicited antibody responses similar to the standard dose of 15 μg of the HA/strain IM injection at 4 weeks post-vaccination. However, the antibody responses for influenza A(H1N1)pdm09 rapidly declined, especially in the case of the ID injection, whereas they were comparable for influenza A(H3N2). Additional strategies for increasing vaccine durability should be considered, especially for new pandemic strains affecting elderly COPD patients

Prevalence of Hepatitis B Virus and Hepatitis C Virus Infections among Beauticians in Quy Nhon City, Binh Dinh Province, Vietnam

Objective: To determine the prevalence of hepatitis B virus (HBV) and hepatitis C virus (HCV) infections among beauticians and to identify occupational risk factors associated with the infections.Methods: The cross-sectional study of 247 randomly enrolled beauticians was conducted in Quy Nhon City, Viet Nam. Knowledge, perceptions, and practices towards occupational risk of HBV and HCV infections were evaluated using an anonymous questionnaire. Blood samples were tested for hepatitis B surface antigen (HBsAg) and antibodies against HBV and HCV by chemiluminescent microparticle immunoassay. Viral genotyping by real time quantitative PCR was performed for those testing positives for HBsAg and anti-HCV antibodies.Results: The prevalence of HBV and HCV infections was 7.3% (18/247, 95% CI: 4.4-11.3) and 0%, respectively. Among HBsAg(+) subjects, 72.2% (13/18) were identified as being infected with HBV genotype B. Overall, 198/247 (80.2%) perceived that they are at risk of being infected by hepatitis through work. Nearly half of participants (43.3%) were not immune to HBV.Discussions: The prevalence of HBV and HCV infections among beauticians was comparable to the general population previously of Vietnam; no occupational risk factors associated with infections were found. This finding proposed that beauticians might not be a high-risk group for HBV and HCV infections. However, the study revealed a high proportion of persons susceptible to HBV infections suggesting that public health preventive strategies and vaccination targeting these professionals should be implemented

Subjects and time of specimen collection.

<p>Subjects and time of specimen collection.</p

Estimation on the infection rates of the 2009 pandemic influenza in different groups of subjects after the first epide mic wave.

<p>Infection rate is determined by HI titer ≥40 in adults or ≥20 in children.</p

Comparison between HI antibody titers obtained from goose and turkey erythrocytes.

<p>Note: A/Thailand/104/2009(H1N1) was used as the test virus. GMT  =  geometric mean titer, CI  =  confidence intervals, RBC  =  red blood cells,</p><p>NA  =  Not applicable</p