Measles re-emergence in Northern Italy: Pathways of measles virus genotype D8, 2013-2014

Evaluation of the effect of maternally derived antibody on response to MMR vaccine in Thai infants

BACKGROUND

Although the number of measles cases declined globally in response to anti-measles immunisation campaigns, measles has re-emerged. A review of current vaccination policies is required to improve measles elimination strategies.

METHODS

A pseudotype-based virus neutralisation assay (PVNA) was used to measure neutralising antibody titres in serum samples collected from Thai infants at six timepoints before and after two-doses of MMR (1&2) vaccination (ClinicalTrials.gov no. NCT02408926). Vesicular stomatitis virus (VSV) luciferase pseudotypes bearing the haemaglutinin (H) and fusion (F) glycoproteins of measles virus (MeV) were prepared. Serial dilutions of serum samples were incubated with VSV (MeV) pseudotypes and plated onto HEK293-human SLAM1 cells; the neutralising antibody titre was defined as the dilution resulting in 90% reduction in luciferase activity.

RESULTS

Neutralising antibody titres in infants born with high levels of maternal immunity (H group) persisted at the time of the first MMR vaccination, and those infants did not respond effectively by developing protective titres. In contrast, infants with lower maternal immunity (L group) developed protective titres of antibody following vaccination. Responses to the second MMR vaccination were significantly higher (P = 0.0171, Wilcoxon signed-rank test) in the H group. The observed correlation between anti-MeV IgG level and neutralising antibody titre in Thai infants indicates the possibility of using rapid IgG testing as a surrogate measure for neutralising activity to define clinical protection levels within populations.

CONCLUSION

These results demonstrate that varying the timing of the first MMR immunisation according to the level of acquired maternal immunity could increase vaccination immunogenicity and hence accelerate measles eradication.

Molecular Epidemiology of B3 and D8 Measles Viruses through Hemagglutinin Phylogenetic History

Of the 24 known measles genotypes, only D8 and B3 are responsible for outbreaks in the last years in Europe, Asia, and America. In this study the H gene of 92 strains circulating between 2015 and 2019 in Lombardy, Northern Italy, and 1273 H sequences available in GenBank were analyzed in order to evaluate the genetic variability and to assess the conservation of the immunodominant sites. Overall, in Lombardy we observed the presence of four different B3 and three different D8 clusters, each one of them including sequences derived from viruses found in both vaccinated and unvaccinated subjects. Worldwide, the residue 400 within the H protein, a position located within the main immune epitope, is mutated in all circulating strains that belong to the two globally endemic genotypes, B3 and D8. Our data demonstrate the usefulness of measles virus (MV) H gene sequencing. Indeed, the monitoring the H protein epitopes of circulating strains could be included in the measles laboratory surveillance activities in order to improve and optimize strategies for measles control, as countries go towards elimination phase.

Healthcare Workers' Preparedness: An Exploratory Study for Measles Control in a Middle-Income Country

Background

Healthcare workers (HCWs) should have an active role in measles control.

Objective

This study aimed to assess the HCWs’ measles immune status and its influencing factors; to measure their knowledge, attitude, and practice toward measles infection/vaccination; and to identify factors predicting their vaccination status.

Methods

Data were collected using a semi-tailored questionnaire. Immunoglobulin G against measles was measured. Regression analysis for measles vaccination was performed.

Results

Approximately 97 HCWs (93.3%) were seropositive, 79 (76.0%) were vaccinated, 18 (17.3%) were previously infected, and 9 (8.7%) were both vaccinated and previously infected. One previously vaccinated participant was seronegative. The immune status was associated with marital status, residence, work duration, infection control training, and wearing personal protective equipment. Positive attitudes and practices were reported. Marital status and infection control training were predictors for measles vaccination.

Conclusion

HCWs showed readiness to control the spread of measles. National policies for compulsory HCWs’ vaccination and immune status check before training and employment are required.

Molecular mechanism by which residues at position 481 and 546 of measles virus hemagglutinin protein define CD46 receptor binding using a molecular docking approach

The hemagglutinin (H) protein of measles viruses (MeV) mediates binding to the cellular receptors, CD46,human signaling lymphocyte activation molecule and nectin-4. Vaccine strains primarily contain H-proteins possessing MeV-H: Y481 and can utilize CD46. Reports suggest that a single amino acid change in MeV-H at position 481 in wild type strains renders them inefficient in utilizing CD46. The in-depth molecular mechanism by which substitutions at 481 and another reported critical residue position 546 affects CD46 binding affinity however remains elusive. We used molecular docking studies of CD46 with MeV-H possessing Y481 N/D to understand the in-depth molecular mechanism involved. It was found that loss in either of the hydrogen bond (H-bond) contacts (MeV-H:481-CD46:65, MeV-H:546-CD46:63) in the central contact region prevented efficient CD46 binding. Y481 N could form the specific H-bond, while G546S H-bond could be formed only in conjunction with Y481, revealing the significance of these residues in determining CD46 receptor binding potential. Elucidating the underlying molecular mechanism of receptor usage by the MeV has implications to understanding cellular tropism, viral pathogenesis and therapy.

Genetic characterisation of Measles virus variants identified during a large epidemic in Milan, Italy, March-December 2017

In 2017, Italy experienced a large measles epidemic with 5408 cases and four deaths. As Subnational Reference Laboratory of the Measles and Rubella surveillance NETwork (MoRoNET), the EpiSoMI (Epidemiology and Molecular Surveillance of Infections) Laboratory (University of Milan) set up rapid and active surveillance for the complete characterisation of the Measles virus (Mv) responsible for the large measles outbreak in Milan and surrounding areas (Lombardy, Northern Italy). The aims of this study were to describe the genetic profile of circulating viruses and to track the pathway of measles transmission. Molecular analysis was performed by sequencing the highly variable 450 nucleotides region of the N gene (N-450) of Mv genome. Two-hundred and ninety-nine strains of Mv were analysed. The phylogenetic analysis showed five different variants, two not previously described in the studied area, belonging to D8 and B3 genotypes. Three events of continuous transmission of autochthonous variants (D8-Osaka, D8-London and B3-Milan variants) and two events of continuous transmission of imported variants (B3-Dublin and D8-Hulu Langat) tracked five different transmission pathways. These pathways outlined two epidemic peaks: the first in April and the second in July 2017. The correlation between Mv variant and the epidemiological data may enable us to identify the sources of virus importation and recognise long-lasting virus transmission pathways.

Case-based surveillance of measles in Sicily during 2012-2017: The changing molecular epidemiology and implications for vaccine strategies

Following the indication of the World Health Organization, a national plan for the elimination of measles was approved in Italy and this included the improvement of the molecular surveillance of measles viruses and the interruption of indigenous transmission of the disease. Nevertheless, large outbreaks continue to occur in almost all regions of the country, including Sicily. Here we describe the epidemiology and molecular dynamics of measles viruses as a result of the measles surveillance activity carried out by the "Reference Laboratory for Measles and Rubella" in Sicily over a 5-year period. Biological samples of 259 suspected measles cases were tested for viral RNA detection and a total of 223 (86.1%) were classified as laboratory confirmed. The median age of confirmed measles cases was 21.0 years and about half of them were adults aged 19 years and older. Overall, one-third of the patients showed clinical complications and these latter were more common among adults than children (44.9% vs. 25.7%). The vast majority of measles cases were unvaccinated (94.2%, n = 210). The phylogenetic analysis of 221 measles virus nucleotide sequences revealed sporadic detections of genotypes D4 and H1, while endemic circulation of genotypes D8 and B3 was documented. Genotype D8 was associated with epidemics occurred between 2013 and 2016, whereas genotype B3 was more recently introduced into Sicily characterizing the current measles outbreak. The results of this study confirm the autochthonous co-circulation of viral variants belonging to different genotypes during the study period, and emphasizes the need of measles surveillance programmes in order to investigate the viral dynamics, the pathways of disease transmission, and to eventually adapt the development of successfull vaccine formulations.

Ongoing large measles outbreak with nosocomial transmission in Milan, northern Italy, March-August 2017

A large measles outbreak has been ongoing in Milan and surrounding areas. From 1 March to 30 June 2017, 203 measles cases were laboratory-confirmed (108 sporadic cases and 95 related to 47 clusters). Phylogenetic analysis revealed the co-circulation of two different genotypes, D8 and B3. Both genotypes caused nosocomial clusters in two hospitals. The rapid analysis of epidemiological and phylogenetic data allowed effective surveillance and tracking of transmission pathways.

Towards measles elimination in Italy: Virological surveillance and genotypes trend (2013-2015)

In accordance with the goal of the World Health Organization Regional Office for Europe, the Italian National Measles and Rubella Elimination Plan aimed to interrupt indigenous measles transmission in Italy by the end of 2015. However, from 2013 to 2015, Italy experienced high measles burden with 4902 measles cases (49.3% laboratory-confirmed) reported to the enhanced measles surveillance system (cumulative incidence in the triennium reference period: 2.4/100,000 population). The measles elimination goal was not reached. Laboratory surveillance of measles circulating genotypes is performed by the Measles and Rubella National Reference Laboratory (NRL) at the Italian National Institute of Health (Istituto Superiore di Sanità - ISS), in Rome. Samples received from 1 January 2013-31 December 2015 were analysed. Those positive for measles genome by molecular tests were sequenced and phylogenetically analysed. Phylogenetic analysis performed by NRL identified that genotypes D4 and D8 were endemic and co-circulated in 2011-2013: study results show that genotype D4 disappeared during 2013. Sporadic cases were associated to genotype B3 during 2011-2013, which became endemic in Italy during 2014 and co-circulated with D8 until 2015. Sporadic cases were found belonging to genotypes D9 and H1 all over the period in exam. Similar trend has been observed in European WHO Region.

Knowledge, Attitude and Behaviours towards Recommended Vaccinations among Healthcare Workers

Healthcare workers (HCWs) are an important group of professionals exposed to biological risk during their work activities. So, the aim of this study is to perform a survey on the knowledge, attitude and behaviour of Italian HCWs towards the vaccinations recommended by the Ministry of Health. A cross-sectional study was carried out during the period September 2014–August 2015 in the Lazio region. The study was conducted by recruiting HCWs and biomedical students. The sample was comprised of 571 responders, of whom 12.4% were physicians, 18.9% were nurses, 34.3% were other HCW, and 34.3% were biomedical students (medical and nurses students). Hepatitis B virus (HBV) is perceived as a risk for personal health by 457 (80%) participants; TB is also worrying (434; 76%). Moreover, HBV (70.9%) and tuberculosis (TB) (79.2%) are perceived as a risk for health, while influenza is not considered so by most participants (46.2%). There is an underestimation of the role of influenza, perceived as a risk for 137 respondents (24%). The vaccination rate among these HCWs is highest for Hepatitis B virus (HBV) (82%), and lowest for influenza (28.5%) and varicella (40.3%). The vast majority of responders are in favour of HBV (77.8%) and TB (64.8%) vaccines. For other vaccinations there is less interest (between 33% and 40% for measles, mumps, rubella, pertussis and influenza). This study shows that knowledge of recommended occupational vaccinations is insufficient in HCWs, with few exceptions represented by HBV and TB. There is a need for novel approaches in this field, with the aim of enhancing vaccine coverage among HCW.