Paola Canepa

Adjuvanted seasonal influenza vaccines and perpetual viral metamorphosis: The importance of cross-protection

Vaccination is considered the most effective means of reducing influenza burden, providing substantial benefits in terms of reduction of morbidity, complications, hospitalizations and deaths, even if vaccines have been associated with a reduced immune response and lower effectiveness in older adults, in particular when a mismatch between the vaccine and the circulating virus strains occurred. Several strategies have been proposed to enhance vaccine protection against drifted strains, including the use of adjuvants. Among oil-emulsion adjuvants, MF-59 was approved for human use more than a decade ago and it is largely used for adjuvantation of influenza vaccine. Recent studies have demonstrated that addition of the MF-59 to subunit influenza vaccine can lead to higher haemagglutination-inhibiting seroprotection rates and to higher neutralization antibody titers against drifted strains not included in the vaccine respect to non-adjuvanted vaccine. Promising results were obtained using a new generation of oil-in-water emulsion adjuvants, named AS, offering cross-protection against heterologous challenge in ferrets.

Intanza® 15 mcg intradermal influenza vaccine elicits cross-reactive antibody responses against heterologous A(H3N2) influenza viruses

The aim of the present study was to explore the ability of Intanza(®) 15 μg, the intradermal (ID) trivalent inactivated split-virion influenza vaccine containing 15 μg hemagglutinin per strain, to enhance the antibody responses against heterologous circulating H3N2 strains in adults 60 years and older. During the 2006-2007 influenza season, subjects aged 60 years or older were randomly assigned to receive one dose of ID or an intramuscular (IM, Vaxigrip(®)) influenza vaccine, which contained the reassortant A/Wisconsin/67/05(H3N2) strain as the H3N2 component. Antibody responses were assessed against the homologous vaccine strain, against the A/Brisbane/10/07(H3N2) reassortant strain and against four heterologous H3N2 field isolates (A/Genoa/62/05(H3N2), A/Genoa/3/07(H3N2), A/Genoa/2/07(H3N2), A/Genoa/3/06(H3N2)). The viruses tested belonged to three different clades that were closely related antigenically to A/California/7/04(H3N2), A/Nepal/921/06(H3N2) and A/Brisbane/10/07(H3N2). Antibody responses to these viruses were measured in 25 subjects per group using both haemagglutination inhibition (HI) and neutralization (NT) assays. At least one Committee for Medicinal Products for Human Use (CHMP) immunogenicity criteria for vaccine approval in the elderly was reached by both vaccines against all the viruses used in the study. All three CHMP criteria were reached against A/California/7/04(H3N2)-like, A/Nepal/921/06(H3N2)-like and A/Brisbane/10/07(H3N2)-like viruses by Intanza(®) 15 μg ID vaccine, while IM vaccination did not meet seroprotection criteria against circulating A/Nepal/921/06(H3N2)-like and A/Brisbane/10/07(H3N2)-like viruses or seroconversion criteria against A/Brisbane/10/07(H3N2)-like viruses. Post-vaccination HI titer, seroconversion, and seroprotection rates were higher against all viruses in subjects who received Intanza(®) 15 μg. The superiority of the seroprotection rate against the A/Nepal/921/06(H3N2)-like strain attained statistical significance despite the small sample size. Upon Beyer correction for pre-vaccination status, post-immunization HI titers against A/California/7/04(H3N2)-like and A/Brisbane/10/07(H3N2)-like strains and NT post-immunization titers against A/Wisconsin/67/05(H3N2), A/California/7/04(H3N2)-like, A/Brisbane/10/07(H3N2)-like strains were significantly higher in subjects immunized with Intanza(®) 15 μg than in individuals receiving IM vaccine. This study, although limited in the size of study population, demonstrated the broader immune response elicited by an ID influenza vaccine vs. a standard IM influenza vaccine against heterologous viruses including field isolates.

Increasing Incidence of Streptococcus pneumoniae Serotype 19A and Emergence of Two Vaccine Escape Recombinant ST695 Strains in Liguria, Italy, 7 Years after Implementation of the 7-Valent Conjugated Vaccine

ABSTRACT Two serotype 19A (ST695) Streptococcus pneumoniae vaccine escape recombinant strains attributable to capsular switching events were detected by a laboratory surveillance system that is an integral part of a vaccination program begun in Liguria, Italy, in May 2003, an Italian administrative region with long-lasting high coverage, an unusual occurrence in Europe. To our knowledge, this is the first detection of an occurrence of capsular switching outside the United States.

Burden of the 1999-2008 seasonal influenza epidemics in Italy: comparison with the H1N1v (A/California/07/09) pandemic.

Despite preventive efforts, seasonal influenza epidemics are responsible for substantial morbidity and mortality every year worldwide, including developed countries. The A/H1N1v pandemic imposed a considerable healthcare and economic burden. In order to obtain an accurate estimate of the economic burden of influenza, and hence to guide policy-makers effectively, systematic studies are necessary. To this end, data from epidemiological surveillance are essential. To estimate the impact of the 1999-2008 seasonal influenza epidemics and the H1N1v pandemic, we analyzed data from the Italian Influenza Surveillance System (CIRINET). In the period 1999-2008, the Italian surveillance network consisted of sentinel general practitioners and pediatricians, who reported cases of Influenza-Like Illness (ILI) and Acute Respiratory Infections (ARI) observed during their clinical practice from mid-October to late April each year; reports were sent to the Center for Research on Influenza and other Viral Infections (CIRI-IV). CIRI-IV receives data from 9 of the 20 Italian Regions: Liguria, Abruzzo, Calabria, Friuli Venezia Giulia, Lombardy, Puglia, Sicily, Tuscany and Umbria. Previous estimates of influenza case costs were used in economic evaluations. Clinical-epidemiological and Virological surveillance of the seasonal epidemics from 1999-2008 showed that the highest epidemic period was 2004-2005, when a new variant of the H3N2 influenza virus subtype emerged (A/California/07/04). Indeed, the highest peak of morbidity in the decade occurred in February 2005 (12.6 per 1,000 inhabitants). In 1999-2008, H1N1 subtype strains circulated, and co-circulated with strains belonging to the H3N2 subtype and B type. Regarding B viruses in 2001-02, viruses belonged to the B/Victoria/02/07 lineage re-emerged, and in subsequent years co-circulated with viruses belonging to the B/Yamagata/lineage. The estimated costs of seasonal epidemics from 1999-2008 in Italy ranged from €15 to €20 billion, and the costs of the H1N1v pandemic ranged from €1.3 to €2.3 billion. This Italian study yields interesting conclusions: the results of Influenza surveillance in several developed countries vary markedly; influenza imposes a considerable social, healthcare and economic burden; most cases that occurred during the pandemic involved subjects under 14 years of age, and, although the clinical course of H1N1v influenza was usually mild, the related economic burden was heavy.

Molecular and serological diversity of Neisseria meningitidis carrier strains isolated from Italian students aged 14 to 22 years.

ABSTRACT Neisseria meningitidis is an obligate human commensal that commonly colonizes the oropharyngeal mucosa. Carriage is age dependent and very common in young adults. The relationships between carriage and invasive disease are not completely understood. In this work, we performed a longitudinal carrier study in adolescents and young adults (173 subjects). Overall, 32 subjects (18.5%) had results that were positive for meningococcal carriage in at least one visit (average monthly carriage rate, 12.1%). Only five subjects tested positive at all four visits. All meningococcal isolates were characterized by molecular and serological techniques. Multilocus sequence typing, PorA typing, and sequencing of the 4CMenB vaccine antigens were used to assess strain diversity. The majority of positive subjects were colonized by capsule null (34.4%) and capsular group B strains (28.1%), accounting for 23.5% and 29.4% of the total number of isolates, respectively. The fHbp and nhba genes were present in all isolates, while the nadA gene was present in 5% of the isolates. The genetic variability of the 4CMenB vaccine antigens in this collection was relatively high compared with that of other disease-causing strain panels. Indications about the persistence of the carriage state were limited to the time span of the study. All strains isolated from the same subject were identical or cumulated minor changes over time. The expression levels and antigenicities of the 4CMenB vaccine antigens in each strain were analyzed by the meningococcal antigen typing system (MATS), which revealed that expression can change over time in the same individual. Future analysis of antigen variability and expression in carrier strains after the introduction of the MenB vaccine will allow for a definition of its impact on nasopharyngeal/oropharyngeal carriage.

Cross-protection against drifted influenza viruses: Options offered by adjuvanted and intradermal vaccines

Antigenic drift, the evolutionary mechanism of influenza viruses, results in an increased susceptibility of vaccinated subjects against circulating viruses. New vaccines able to grant a broader and cross-reactive immune response against drifted influenza variants are needed. Several strategies were explored to enhance the immunogenicity of plain vaccines: adjuvants, carriers and intradermal administration of influenza vaccine emerge as a promising options. To evaluate the ability of a MF59™-adjuvanted and intradermal influenza vaccine to elicit an effective antibody response against circulating viruses presenting antigenic patterns different from those of the vaccine strains, we compared antibody responses elicited by “implemented” vaccines and conventional intramuscular trivalent inactivated vaccine against heterologous circulating influenza A viruses. Different studies, simulating different epidemiological pictures produced by the natural antigenic drift of seasonal influenza viruses, highlighted the superior cross-reactivity of the antibodies elicited by MF59™ and intradermal vaccines, compared with subunit or split vaccine against heterologous viruses.

Carriage of Streptoccoccus pneumoniae 7 years after implementation of vaccination program in a population with very high and long-lasting coverage, Italy

To evaluate how the 7-valent pneumococcal vaccine (PCV7) programme and the very high vaccination coverage reached for over 4 years affected the prevalence of Streptoccoccus pneumoniae serotypes in the paediatric population and to evaluate demographic, behavioural and risk factors for carriage in the post-vaccination era, a cross-sectional study on nasopharyngeal carriage was performed. Six hundred sixty-nine children under the age of 5, representative of the open population, were enrolled by cluster sampling. High sensitive techniques for detection of multi-serotype carriage, i.e. broth enrichment and real-time PCR and sequential PCRs for detection and typing, respectively, were used. Of the 669 enrolled children, 97.8% were compliant with the recommended PCV7 vaccination schedule. Post-stratification adjustment for age was applied considering the Ligurian population as standard population. Age-weighted carriage rate was 50.1% and 78% of carriers were colonized by more than one serotype. The prevalence of carriage increased with age from 22% in the first year of life, to 48.6% in the second year of life and to 60% in the 25-59 month age group. Age-weighted prevalence of any of the PCV7, PCV10 or PCV13 serotypes was 10.3%, 20.3% and 27.5%, respectively. PCV7 serotypes were mainly represented by serotype 4 that was carried since the 3rd year of life and was responsible for invasive pneumococcal disease (IPD) and non-IPD in adults, but not in children confirming the high vaccine effectiveness. Among the serotypes included in recently available vaccines, serotypes 5 and 19A showed a higher prevalence, being carried by 15.2% and 8.8% of the population, respectively. A multivariate analysis showed that age, the presence of child siblings at home and day care attendance covariates were strongly associated with S. pneumoniae carriage. In conclusion, over 7 years of vaccination with PCV7 and very high coverage in the last 4 years has led to low carriage prevalence in the first year of life rapidly increasing in the following years and high prevalence of non-PCV7 serotypes carriage.

Carriage of Streptoccoccus pneumoniae in healthy adults aged 60 years or over in a population with very high and long-lasting pneumococcal conjugate vaccine coverage in children: rationale and perspectives for PCV13 implementation.

A serial cross-sectional study of nasopharyngeal carriage among adults aged 60 y or over was conducted in winter-spring 2012 with the aim to describe circulating Streptococcus pneumoniae in an area, Liguria Administrative Region, where the vaccine was implemented for a decade and coverage in pediatric age group reached a value close to 100% for more than 5 y, determining a picture of very high vaccine immunological pressure. The serotype-specific carriage picture in adults was compared with that observed in children by means of a cross-sectional study performed one year before using the same sampling and laboratory methods. Cluster sampling enrolled 283 adults, representative of the open population. Detection of multi-serotype carriage was performed using, real-time PCR and primer specific PCRs. Carriage prevalence of participants with at least one positive sample adjusted for age, i.e., period prevalence, was 18.7%, considering the Ligurian population as standard population, showing that the pneumococcal carriage in the elderly is not a rare event as emerged in other surveys. The long-term use of PCV7 has resulted in strong decrease of vaccine types carriage among adults and children. A multivariate analysis showed that age class and contact with children attending day care covariates were strongly associated with Streptococcus pneumoniae carriage. A strong link between the picture observed in < 5-y-old children and ≥ 60-y-old adults emerged: a strong correlation of specific-serotype prevalence between adults and children and risk factor analysis supported the role played by inter-age-group transmission.

Epidemiological changes after PCV7 implementation in Italy: Perspective for new vaccines

The emergence of serotypes not included in 7-valent pneumococcal conjugate vaccine (PCV7), so-called “replacement”, could erode the great advantage offered by vaccination. The effect of the replacement phenomena is very variable in different Countries and depends on one or more of several factors i.e. serotype before PCV7 implementation, PCV7 coverage, period from PCV implementation, vaccination schedule, antibiotic use, etc. The long-term epidemiological picture in Europe regarding serotype change is limited because of the relatively recent introduction of PCV7 - the majority of European Countries have only experienced PCV implementation since 2006 - and the difficulty in reaching very high vaccination coverage. In May 2003, a large-scale program of vaccination against Streptococcus pneumoniae with PCV7 was started in Liguria achieving coverage higher than 90%. The results of this program anticipate the results likely to be achieved when high coverage has been reached in Europe for a period of several years. The project included the immunogenicity evaluation of the co-administration of PCV7 and exavalent vaccine using the 3-5-11 month schedule, effectiveness evaluation and the active and passive surveillance system of invasive pneumococcal disease (IPD) and non-IPD. Since the beginning of PCV7 implementation, the proportion of PCV7 serotype has declined and in 2009-10 it accounted for about 10% of all Streptocuccus pn responsible for IPD and non-IPD. The new 13-valent pneumococcal conjugate vaccine, available since July 2010, will offer a significant added benefit covering about 90%, 100% of IPD and more than 40% and 60% of non-IPD detected in pre-school and school children, respectively, after PCV7 introduction.

Trends of influenza B during the 2010–2016 seasons in 2 regions of north and south Italy: The impact of the vaccine mismatch on influenza immunisation strategy

ABSTRACT Influenza A and B viruses are responsible for respiratory infections, representing globally seasonal threats to human health. The 2 viral types often co-circulate and influenza B plays an important role in the spread of infection. A 6-year retrospective surveillance study was conducted between 2010 and 2016 in 2 large administrative regions of Italy, located in the north (Liguria) and in the south (Sicily) of the country, to describe the burden and epidemiology of both B/Victoria and B/Yamagata lineages in different healthcare settings. Influenza B viruses were detected in 5 of 6 seasonal outbreaks, exceeding influenza A during the season 2012–2013. Most of influenza B infections were found in children aged ≤ 14 y and significant differences were observed in the age-groups infected by the different lineages. B/Victoria strains prevailed in younger population than B/Yamagata, but also were more frequently found in the community setting. Conversely, B/Yamagata viruses were prevalent among hospitalized cases suggesting their potential role in the development of more severe disease. The relative proportions of viral lineages varied from year to year, resulting in different lineage-level mismatch for the B component of trivalent influenza vaccine. Our findings confirmed the need for continuous virological surveillance of seasonal epidemics and bring attention to the adoption of universal influenza immunization program in the childhood. The use of tetravalent vaccine formulations may be useful to improve the prevention and control of the influenza burden in general population.