Measles Virus IgG Avidity Assay for Use in Identification of Measles Vaccine Failures in Tianjin, China

Objective To identify measles vaccine failures in Tianjin, China using a measles virus Ig G avidity assay.Methods The China Information System for Disease Control and Prevention(CISDCP) was used to collect information about measles cases and blood specimens in Tianjin from 2013 to 2015. Measlesspecific Ig M and Ig G antibodies were detected using Enzyme-Linked Immunosorbent Assay(ELISA).Avidity testing for measles Ig G was performed using a commercial enzyme immunoassay(EIA).Results A total of 284 confirmed measles cases were identified. Of this total, 262(92.25%) were in patients aged ≥ 20 years. High avidity was exhibited in 172(60.56%) cases, while 80(28.17%) cases demonstrated low avidity. High avidity was detected in only 21.43% of cases in patients aged < 1 year.The proportion of high avidity increased with age, and was significantly higher in patients aged 30–39 years at 70.07%(χ~2 = 17.27, P = 0.002). Of the 52 measles cases in patients with a history of vaccinations,41(78.85%) cases showed high avidity, indicating secondary vaccine failures(SVF). In these vaccinations,there was no significant difference(P > 0.05) in clinical severity between high avidity and low avidity cases. However, regardless of vaccination status, clinical severity was significantly lower in high avidity cases(P < 0.001) than in low avidity cases. The percentages of positive measles Ig M results in high avidity and low avidity cases were 66.28% and 91.25%, respectively. Geometric Mean Concentration(GMC) was significantly lower in high avidity cases at 33.73 U/m L, compared to 166.07 U/m L in low avidity cases.Conclusions Low clinical severity and inconclusive Ig M antibody results are more likely in high avidity measles cases. Measles cases were more common in adults. Therefore, a further dose of vaccines should be recommended for 30–39 years in Tianjin.

Diagnosis of West Nile virus infections:Evaluation of different laboratory methods

BACKGROUND The diagnosis of West Nile virus(WNV)is challenging due to short-term and low-level viremia,flavivirus cross-reactivity,and long immunoglobulin M(IgM)persistence.AIM To evaluate different methods for WNV detection[reverse transcription-polymerase chain reaction(RT-PCR),IgM/IgG antibodies,IgG avidity]in serum,cerebrospinal fluid(CSF),and urine samples of patients with confirmed WNV infection.METHODS The study included patients with confirmed WNV neuroinvasive infection(n=62),asymptomatic WNV seropositive individuals(n=22),and individuals with false-positive WNV IgM antibodies(n=30).WNV RNA was detected using RT-PCR.A commercial ELISA was used to detect WNV IgM/IgG antibodies with confirmation of cross-reactive samples using a virus neutralization test(VNT).IgG-positive samples were tested for IgG avidity.RESULTS The WNV-RNA detection rates were significantly higher in the urine(54.5%)/serum(46.4%)than in CSF(32.2%).According to the sampling time,the WNV-RNA detection rates in urine collected within 7 days/8-14/≥15 days were 29.4/66.6/62.5%(P=0.042).However,these differences were not observed in the CSF.The median RT-PCR cycle threshold values were significantly lower in urine(32.5,IQR=28-34)than in CSF(34.5,IQR=33-36).The frequency of positive WNV IgM and IgG significantly differed according to the sampling time in serum but not in CSF.Positive IgM/IgG antibodies were detected in 84.3/9.3%of serum samples collected within 7 days,100/71.1%of samples collected 8-14,and 100%samples collected after≥15 days.Recent WNV infection was confirmed by low/borderline avidity index(AI)in 13.6%of asymptomatic individuals.A correlation between ELISA and AI was strong negative for IgM and strong positive for IgG.No significant correlation between ELISA IgG and VNT was found.CONCLUSION The frequency of WNV RNA and antibody detection depends on the sampling time and type of clinical samples.IgG avidity could differentiate recent WNV infections from long-persisting IgM antibodies.

The dilemma of cytomegalovirus and hepatitis B virus interaction

Hepatitis B virus(HBV)remains a global public health problem despite the availability of effective vaccine and antiviral therapy.Cytomegalovirus(CMV),another hepatotropic virus,is also very prevalent in the general population worldwide.Both HBV and CMV can persist in the host and have potential to reactivate especially with weakened host cellular immunity.Superimposed CMV infection can lead to severe HBV reactivation.The pathogenesis of the co-infection of HBV and CMV remains poorly understood.Studies reported conflicting results regarding the inhibitory effect of CMV on HBV replication.There is an unmet need on the management of co-infection of HBV and CMV;research initiatives dedicated to understanding their interactions are urgently needed.