Immunogenicity after outbreak response immunization activities among young healthcare workers with secondary vaccine failure during the measles epidemic in Korea, 2019

BACKGROUND

Despite high vaccination coverage, measles outbreaks have been reported in measles elimination countries, especially among healthcare workers in their 20 and 30 s. This study was designed to identify measles-susceptible individuals and to evaluate whether primary or secondary vaccine failure occurred during measles outbreak response immunization (ORI) activities.

METHODS

The study population was divided into three groups as follows: natural immunity group (Group 1), vaccine-induced immunity group (Group 2), and vaccine failure group (Group 3). We evaluated the immunogenicity of measles among healthcare workers using three methods-enzyme-linked immunoassays, plaque reduction neutralization tests, and avidity assays. The results were assessed at baseline, 4 weeks after, and 6 months after the completion of measles-mumps-rubella (MMR) vaccination.

RESULTS

In total, 120 subjects were enrolled, with 40 subjects in each group. The median age of Group 3 was 29 years, which was significantly lower than that of the other groups. The baseline negative measles virus (MeV) IgG in Group 3 increased to a median value of 165 AU/mL at 4 weeks after ORI and was lower than that in Groups 1 and 2. The median neutralizing antibody titer was highest in Group 1, and this was significantly different from that in Group 2 or Group 3 at 4 weeks (944 vs. 405 vs. 482 mIU/mL, P = 0.001) and 6 months (826 vs. 401 vs. 470, P = 0.011) after ORI. The rates of high MeV avidity IgG were highest in Group 2, and these were significantly different from those in Groups 1 or 3 at 4 weeks (77.5 vs. 90% vs. 88.6%, P = 0.03) and 6 months (81 vs. 94.8 vs. 82.1%, P = 0.01) after ORI.

CONCLUSIONS

Considering the MeV-neutralizing antibodies and IgG avidity after MMR vaccination in measles-susceptible group, vaccine failure is inferred as secondary vaccine failure, and further data regarding the maintenance of immunogenicity are needed based on long-term data. The MeV-neutralizing antibody levels were highest in the natural immunity group, and the primary vaccine-induced immunity group showed the highest rates of high MeV IgG avidity.

[The virology of SARS-CoV-2]

Das neue „severe acute respiratory syndrome coronavirus 2“ (SARS-CoV-2) hat tief greifende Auswirkungen auf Gesellschaft, Wirtschaft und medizinische Versorgung. Umso wichtiger ist es, die Eigenschaften des Virus zu verstehen und diagnostisch, therapeutisch wie auch epidemiologisch zu nutzen. Im vorliegenden Beitrag wird zunächst die medizinische Bedeutung der Coronaviren im Allgemeinen erläutert. Danach wird auf das „angiotensin-converting enzyme 2“ (ACE2) als Bindungsstelle von SARS-CoV‑2 sowie dessen möglichen Einfluss auf die Erkrankungssuszeptibilität eingegangen. Als diagnostischer Goldstandard für den Nachweis einer aktiven SARS-CoV-2-Infektion gilt der Erregerdirektnachweis mit Nukleinsäureamplifikationstechniken. Zu Beginn der Symptome ist ein Abstrich der oberen Luftwege aufgrund der dann hohen Viruslast besonders geeignet. Im späteren Verlauf kann der Direktnachweis über Proben aus den unteren Atemwegen oder über einen Stuhl- bzw. Analabstrich gelingen. Antigen- oder Antikörper(AK)-Tests können den Erregerdirektnachweis nicht ersetzen. Insbesondere für epidemiologische Fragestellungen ist aber der Nachweis von Immunglobulin-G-AK von Interesse (Serokonversionszeit von teils mehreren Wochen). Der „plaque reduction neutralization test“ weist ausschließlich AK nach, die Viren neutralisieren. Das Verfahren ist aber aufwendig. Zudem ist die Bedeutung dieser AK bezüglich der Immunität gegen eine Zweitinfektion unsicher. Dank moderner Technik sind bereits Tausende SARS-CoV-2-Sequenzen verfügbar, die eine Genomvariabilität zeigen. Die Mutation D614G in den „S spikes“ scheint eine höhere Infektiosität zu bedingen. Mutationen können die Diagnostik und Therapie beeinträchtigen, was ein Monitoring erforderlich macht.

Low seroprevalence of Zika virus infection among adults in Southern Taiwan

Background

We recently conducted a serosurvey of newly arrived workers in Taiwan from four Southeast Asian countries which revealed that 1% of the migrant workers had laboratory-confirmed recent Zika virus (ZIKV) infection. Taiwan, where Aedes mosquitoes are prevalent, has a close relationship with Southeast Asian countries. Up to now, 21 imported cases of ZIKV infection have been reported in Taiwan, but there has been no confirmed indigenous case. The aim of this serosurvey was to assess whether there was unrecognized ZIKV infections in Taiwan.

Methods

A total of 212 serum samples collected in a cross-sectional seroepidemiologic study conducted during the end of the 2015 dengue epidemic in Tainan, Taiwan, were analyzed. Anti-ZIKV IgM and IgG were tested using commercial enzyme-linked immunosorbent assays (ELISAs). Plaque reduction neutralization tests (PRNTs) for ZIKV and four dengue virus (DENV) serotypes were performed for samples with positive anti-ZIKV antibodies. A confirmed case of ZIKV infection was defined by ZIKV PRNT₉₀ titer ratio ≥ 4 compared to four DENV serotypes.

Results

The mean age of the 212 participants was 54.0 years (standard deviation 13.7 years), and female was predominant (67.0%). Anti-ZIKV IgM and IgG were detected in 0 (0%) and 9 (4.2%) of the 212 participants, respectively. For the 9 samples with anti-ZIKV IgG, only 1 sample had 4 times higher ZIKV PRNT₉₀ titers compared to PRNT₉₀ titers against four dengue virus serotypes; this individual denied having traveled abroad.

Conclusions

The results suggest that undetected indigenous ZIKV transmission might have occurred in Taiwan. The findings also suggest that the threat of epidemic transmission of ZIKV in Taiwan does exist due to extremely low-level of herd immunity. Our study also indicates that serological tests for ZIKV-specific IgG remain a big challenge due to cross-reactivity, even in dengue non-endemic countries.

[Establishment and evaluation of a triple-color human papillomavirus pseudovirion neutralization assay]

Objective: To establish a triple-color pseudovirion-based neutralization assay (PBNA) and evaluate its capability of detecting immunogenicity of the sera generated by the immunization of HPV 9-valent vaccine. Methods: HPV pseudovirus (PsVs) 6/11/16/18/31/33/45/52/58 with the encapsidated fluorescence expressing red fluorescent plasmid N31-MCHREEY, green fluorescent N31-EGFP or blue fluorescent N31-mTagBFP were generated. The concentration of HPV PsVs and the infection titers of HPV PsVs were detected by double-antibody sandwich ELISA and TCID(50), respectively. The single- and triple color HPV 16/33/45 PsVs were used to detect the neutralization titers of mice sera immunized with HPV 9-valent vaccine and confirmed the accuracy and specificity of the triple-color PBNAs. Then, the single- and triple color HPV 6/11/18/31/33/45/52/58 PsVs were employed to detect the neutralization titers of cynomolgus macaques sera immunized with HPV 9-valent vaccine and determined whether the triple-color PBNAs could be applied to evaluate the immunogenicity of the sera generated by the immunization of HPV9-valent vaccine. Results: The concentration of HPV16 PsVs encapsulating green, red or blue fluorescent plasmid was 5.0 to 6.0 μg/ml and HPV6/11/18/31/33/45/52/59 triple-color HPV PsVs was about 1.0 to 3.0 μg/ml. 9 types HPV PsVs containing EGFP, Mcherry or mTagBFP reporter plasmid were obtained and the concentration can meet the need of neutralization detection. 9 types single-color fluorescent HPV PsVs had similar infectivity against 293FT cells with the infection titer values between 1×10(4) and 1×10(5). The results of PBNAs showed that there was no significant difference in the anti-HPV neutralization titers of mice sera induced by HPV 9-valent vaccine between single-color and triple-color HPV16/33/45 PsVs (P>0.05). Similarly, there was also no significant difference in the anti-HPV neutralization titers of cynomolgus macaques sera induced by HPV 9-valent vaccine between single-color and triple-color HPV6/11/18/31/33/45/52/58 PsVs (P>0.05). Conclusion: We successfully established the triple-color PBNAs and verified the accuracy and specificity of triple-color PBNAs consistent with single-color PBNAs. The triple-color PBNAs can be applied to evaluate the immunogenicity of HPV 9-valent vaccine's immune serum.

Utility of Japanese encephalitis virus subgenomic replicon-based single-round infectious particles as antigens in neutralization tests for Zika virus and three other flaviviruses

The introduction of a foreign virus into an area may cause an outbreak, as with the Zika virus (ZIKV) outbreak in the Americas. Preparedness for handling a viral outbreak involves the development of tests for the serodiagnosis of foreign virus infections. We previously established a gene-based technology to generate some flaviviral antigens useful for functional antibody assays. The technology utilizes a Japanese encephalitis virus subgenomic replicon to generate single-round infectious particles (SRIPs) that possess designed surface antigens. In the present study, we successfully expanded the capacity of SRIPs to four human-pathogenic mosquito-borne flaviviruses that could potentially be introduced from endemic to non-endemic countries: ZIKV, Sepik virus, Wesselsbron virus, and Usutu virus. Flavivirus-crossreactive monoclonal antibodies dose-dependently neutralized these SRIPs. ZIKV-SRIPs also produced antibody-dose-dependent neutralization curves equivalent to those shown by authentic ZIKV particles using sera from a Zika fever patient. The faithful expression of designed surface antigens on SRIPs will allow their use in neutralization tests to diagnose foreign flaviviral infections.

Evaluation of immunogenicity of the 2008-2009 seasonal influenza vaccines by microneutralization test

Purpose

For evaluating the immunogenicity of an influenza vaccine, the microneutralization (MN) test has a higher sensitivity and specificity as compared to the hemagglutination inhibition (HI) test. However, the MN test is more time consuming and is difficult to standardize. We performed the MN test to determine its usefulness as an alternative or complementary test to the HI test for evaluating the immunogenicity of influenza vaccines.

Methods

We compared the MN test with the HI test using 50 paired samples taken from a previous clinical study (2008-2009) in Korean children under 18 years of age.

Results

The linear correlation coefficients of the 2 tests for H3N2, H1N1, and influenza B were 0.69, 0.70, and 0.66, respectively. We identified a high index of coincidence between the 2 tests. For an influenza vaccine, the postvaccination seroprotection rates and seroconversion rates determined by the MN test were 78.0% and 96.0%, 90% and 42.0%, and 42.0% and 48.0% for H3N2, H1N1, and influenza B, respectively. Geometric mean titer fold increases of H3N2, H1N1, and influenza B were 2.89, 5.04, and 4.29, respectively, and were 2.5-fold higher. We obtained good results in the evaluation of the immunogenicity of the 2008-2009 seasonal influenza vaccines.

Conclusion

We found that the MN test was as effective as the HI test. Therefore, we suggest that the MN test can be used as an alternative or complementary test to the HI test for evaluating the immunogenicity of influenza vaccines.