Keeping the memory of influenza viruses

Physical activity and sleep relate to antibody maintenance following naturalistic infection and/or vaccination in older adults

Health behaviours such as being physically active and having good quality sleep have been associated with decreased susceptibility to infection and stronger antibody responses to vaccination. Less is known about how such factors might influence the maintenance of immunity following naturalistic infection and/or prior vaccination, particularly among older adults who may have formed initial antibodies some time ago. This analysis explored antibody levels against a range of common infectious diseases in 104 older adults (60 women) aged 65+ years, and whether these relate to self-reported physical activity (PA) and sleep. PA and sleep were measured subjectively through standardized questions. Antibody levels to a range of common pathogens, including pneumococcal (Pn) and meningococcal (Men) serotypes, Haemophilus influenza type b, diphtheria, and tetanus were assayed using Multiplex technology. Higher PA at baseline related to higher antibody levels against three Pn serotypes and MenY, and higher PA at one month with higher levels against six Pn serotypes. Longer time in bed related to higher antibody levels against Pn4, and longer sleep related to higher levels against Pn19f. More difficulty staying awake in the day related to lower antibodies against Pn19a, Pn19f, MenA and MenY, and more frequent daytime napping related to lower levels against three Pn serotypes and MenY. Using clinically protective antibody thresholds as an outcome showed similar results for PA, but effects for sleep became non-significant, with the exception of time in bed. This extends beyond existing literature demonstrating associations between PA and sleep and peak antibody response to vaccination to antibody maintenance. Longitudinal research with objective measures of health behaviours is warranted.

A plant-derived VLP influenza vaccine elicits a balanced immune response even in very old mice with co-morbidities

BACKGROUND

The elderly are at high risk from influenza, in part because immunity wanes with age and through the accumulation of comorbidities. A novel plant-derived virus-like-particle (VLP) vaccine bearing influenza hemagglutinin can induce a balanced humoral and cellular response in old mice (16-18 months) while split virion vaccines elicit mostly antibodies. Because mice also collect comorbidities and lose immune competence as they age, we wished to determine how the plant-derived VLP vaccine would perform in animals approaching the end of their life-span.

MATERIALS AND METHODS

Old (24-26 months) female BALB/c mice received two intramuscular doses of H1-VLP vaccine, an inactivated H1N1 vaccine (IIV) (both based on A/H1N1/California/07/09) (3μg each) or PBS. Serum was collected on day 42 and humoral responses were measured by enzyme-linked immunosorbent assay (ELISA), microneutralization (MN) and hemagglutination inhibition (HI) assays. Influenza-specific splenocyte CD4+ & CD8+ T cell responses were measured by flow cytometry. Full body computed tomography (CT) and structured necropsies were performed on day 42. Comorbidities including reduced lung volume (kyphosis), masses, abscesses, etc. were assessed using a standard scoring system (1-21) and mice with scores ≥5 were considered to have important comorbidities.

RESULTS

Overall, 53.3% of the animals had significant comorbidities. Three weeks post-boost, HI and MN titres were mostly undetectable but ELISA titres were significantly higher in the H1-VLP animals compared to the IIV group (GMT (95% CI): 961 (427, 2163) vs 425 (200, 903): p = 0.03). Both CD4+(TNFα, IFNγ) and CD8+ (IFNγ) T cell responses were also greater in the H1-VLP group than the IIV.

CONCLUSIONS

Even in very old mice with comorbidities, the plant-made H1-VLP vaccine elicited a stronger and more balanced immune response than IIV. Animals with fewer comorbidities tended to have the better composite (humoral and cellular) responses. These novel vaccines have the potential to address some of the limitations of current vaccines in the elderly.

[Epithelial dysfunction associated with pyo-inflammatory diseases of the ENT organs]

The modern concept of epithelial-endothelial dysfunction and epithelial-endothelial distress-syndrome associated with pyo-inflammatory ENT diseases is presented. It has provided a basis for the analysis of the initial stages of etiopathogenesis of acute and chronic inflammation in the ENT system including the mucous and associated lymphoid tissues as well as the Pirogov-Waldeyer limphopharyngeal ring making up the first protective barrier. The leading role of dysbiosis of synanthropic microflora and endotoxins of the Gram-negative bacteria in the mechanisms of regional responsiveness of the organism to the infection and chronic endotoxic aggression is demonstrated. The regional and synthetic mechanisms underlying the interaction between the external and internal media of the organism are subjected to the analysis with special reference to those operating in epithelium. The possible variants of the outcome of these processes are considered including both the recovery and the development of chronic inflammation. It has been proved that the exhaustion of the internal reserves for the stabilization of the epithelium-associated lymphoid tissue system including the Pirogov-Waldeyer limphopharyngeal ring leads to the formation of epithelial dysfunction as the initial stage of epithelial-endothelial dysfunction and epithelial-endothelial distress-syndrome. It is concluded that the modern concept of epithelial-endothelial dysfunction and epithelial-endothelial distress-syndrome is a fundamental interdisciplinary phenomenon.

Control of influenza infection is impaired by diminished interferon-γ secretion by CD4 T cells in the lungs of toddler mice

Respiratory viral infections, such as influenza, can lead to delayed viral clearance in toddlers, possibly exacerbating disease morbidity. We hypothesized that defective CD4 T cells in toddlers may contribute to a failure to clear virus at a similar rate to adults. Thus, we developed a young mouse model to examine potential divergent responses between toddlers and adults. We determined that young mice (toddler mice, 21 d old) were actively generating and recruiting effector/memory T cells, whereas memory populations were firmly established in older, adult mice (8-10 wk old). We infected toddler and adult mice with influenza A/PR8/34 (H1N1) and found young mice had elevated morbidity, as measured by enhanced weight loss and lower partial pressure of oxygen levels, throughout the infection, thus, modeling the higher morbidity observed in children (<2 y old) during infection. Early viral loads were comparable to adult mice, but toddler mice failed to clear virus by 10 d postinfection. This delayed clearance corresponded to poor lung recruitment of CD4 T cells, lower antiviral T cell responses, and lower B cell/antibodies in the lungs. Mechanistically, diminished interferon-γ was detected in the lungs of toddler mice throughout the infection and corresponded to intrinsic, rather than extrinsic, CD4 T cell limitations in interferon-γ transcription. Moreover, defects in interferon-γ production appeared downstream from signal transducer and activator of transcription 4 in the interleukin-12 signaling pathway, suggesting maturational delays different from neonates. Importantly, recombinant interferon-γ supplementation rescued CD4 T cell numbers in the lungs and influenza-specific antibody formation. This study highlights the intrinsic limitations in CD4 T cell effector functions that may arise in toddlers and contribute to disease pathology.

Short-term exposure to environmental parameters and onset of ST elevation myocardial infarction. The CARDIO-ARSIF registry

BACKGROUND

Environmental parameters have been reported to be triggers of acute myocardial infarction (MI). However, the individual role of each parameter is unknown. We quantified the respective association of climate parameters, influenza epidemics and air pollutants with the onset of ST elevation MI (STEMI) in Paris and the surrounding small ring.

METHODS

Data from the CARDIO-ARSIF registry (Paris and small ring STEMI population), Météo France (Climate), GROG (Influenza epidemic) and AIRPARIF (Air Pollution) were analyzed. The association between short-term exposure (1 day lag time) to environmental parameters and STEMI occurrence was quantified by time series modeling of daily STEMI count data, using Poisson regression with generalized additive models.

RESULTS

Between 2003 and 2008, 11,987 <24H STEMI confirmed by angiography were adjudicated. There was a 5.0% excess relative risk (ERR) of STEMI per 10°C decrease in maximal temperature (95% CI 2.1% to 7.8%: p=0.001) and an 8.9% ERR (95% CI 3.2% to 14.9%: p=0.002) during an influenza epidemic after adjustment on week-days and holidays. Associations were consistent when short-term exposure varied from 2 to 7 days. Associations between lower temperatures and STEMI were stronger in magnitude when influenza epidemic was present. Short-term exposure to climatic parameters or pollutants was not associated with STEMI.

CONCLUSIONS

The present population based registry of STEMI suggests that short-term exposure to lower temperature and influenza epidemic is associated with a significant excess relative risk of STEMI. Subjects at risk for MI may benefit from specific protections against cold temperature and influenza infection.

Trivalent inactivated influenza vaccines induce broad immunological reactivity to both internal virion components and influenza surface proteins

There are a number of related goals of influenza vaccination, including elicitation of protective antibodies and induction of cellular CD4 and CD8+ T cell responses. Because CD4+ T cell expansion and functionality are influenced by peptide specificity and T cell gene expression can be modified by repeated re-stimulations, it is important to evaluate how frequent influenza vaccinations affect CD4+ T cell dependent functions in protective immunity to influenza. Trivalent influenza vaccines (TIV) have production of neutralizing antibodies to HA as their primary goal and main criteria for efficacy. Accordingly, they are not characterized for any other viral components. In the current study, we evaluated whether other influenza virus proteins were present in commercial TIV at levels sufficient for immunogenicity in vivo. Mice that differed with regard to their expressed class II molecules were used in concert with peptide-stimulated cytokine ELISPOT assays to comprehensively evaluate the CD4+ T cell antigen specificity induced by the TIV. Our studies revealed that NA, NP, M1 and NS1 were present in sufficient quantities in the TIV to prime and boost CD4+ T cells. These results suggest that in humans, the broad CD4+ T cell repertoire induced by live infection is continually boosted and maintained throughout life by regular vaccination with licensed intramuscular split vaccines. The implications raised by our findings on CD4+ T cell functionality in influenza are discussed.

Antibody response of healthy children to pandemic A/H1N1/2009 influenza virus

Background

Little is known about the proportion of pediatric pandemic A/H1N1/2009 influenza cases who showed seroconversion, the magnitude of this seroconversion, or the factors that can affect the antibody level evoked by the pandemic A/H1N1/2009 influenza. Aims of this study were to analyse antibody responses and the factors associated with high antibody titres in a cohort of children with naturally acquired A/H1N1/2009 influenza infection confirmed by reverse-transcriptase polymerase chain reaction (RT-PCR).

Results

Demographic, clinical and virologic data were collected from 69 otherwise healthy children with pandemic A/H1N1/2009 influenza (27 females, mean age ± SD: 5.01 ± 4.55 years). Their antibody levels against pandemic A/H1N1/2009 and seasonal A/H1N1 influenza viruses were evaluated by measuring hemagglutination-inhibiting antibodies using standard assays. Sixty-four patients (92.8%) with pandemic A/H1N1/2009 influenza had A/H1N1/2009 antibody levels of ≥40, whereas only 28/69 (40.6%) were seroprotected against seasonal A/H1N1 influenza virus. Those who were seroprotected against seasonal A/H1N1 virus were significantly older, significantly more often hospitalised, had a diagnosis of pneumonia significantly more frequently, and were significantly more often treated with oseltamivir than those who were not seroprotected (p < 0.05). The children with the most severe disease (assessed on the basis of a need for hospitalisation and a diagnosis of pneumonia) had the highest antibody response against pandemic A/H1N1/2009 influenza virus.

Conclusions

Otherwise healthy children seem to show seroprotective antibody titres after natural infection with pandemic A/H1N1/2009 influenza virus. The strength of the immune response seems to be related to the severity of the disease, but not to previous seasonal A/H1N1 influenza immunity.

Infection with seasonal influenza virus elicits CD4 T cells specific for genetically conserved epitopes that can be rapidly mobilized for protective immunity to pandemic H1N1 influenza virus

In recent years, influenza viruses with pandemic potential have been a major concern worldwide. One unresolved issue is how infection or vaccination with seasonal influenza virus strains influences the ability to mount a protective immune response to novel pandemic strains. In this study, we developed a mouse model of primary and secondary influenza infection by using a widely circulating seasonal H1N1 virus and the pandemic strain of H1N1 that emerged in Mexico in 2009, and we evaluated several key issues. First, using overlapping peptide libraries encompassing the entire translated sequences of 5 major influenza virus proteins, we assessed the specificity of CD4 T cell reactivity toward epitopes conserved among H1N1 viruses or unique to the seasonal or pandemic strain by enzyme-linked immunospot (ELISpot) assays. Our data show that CD4 T cells reactive to both virus-specific and genetically conserved epitopes are elicited, allowing separate tracking of these responses. Populations of cross-reactive CD4 T cells generated from seasonal influenza infection were found to expand earlier after secondary infection with the pandemic H1N1 virus than CD4 T cell populations specific for new epitopes. Coincident with this rapid CD4 T cell response was a potentiated neutralizing-antibody response to the pandemic strain and protection from the pathological effects of infection with the pandemic virus. This protection was not dependent on CD8 T cells. Together, our results indicate that exposure to seasonal vaccines and infection elicits CD4 T cells that promote the ability of the mammalian host to mount a protective immune response to pandemic strains of influenza virus.

Serological memory and long-term protection to novel H1N1 influenza virus after skin vaccination

BACKGROUND

A major goal in influenza vaccine development is induction of serological memory and cellular responses to confer long-term protection and limit virus spread after infection. Here, we investigate induction of long-lived immunity against the 2009 H1N1 virus after skin vaccination.

METHODS

BALB/c mice received a single dose of 5 μg inactivated A/California/04/09 virus via coated metal microneedles (MN) applied to skin or via subcutaneous injection.

RESULTS

MN or subcutaneous vaccination elicited similar serum IgG and hemagglutination inhibition titers and 100% protection against lethal viral challenge 6 weeks after vaccination. Six months after vaccination, the subcutaneous group exhibited a 60% decrease in functional antibody titers and extensive lung inflammation after challenge with 10 × LD(50) of homologous virus. In contrast, the MN group maintained high functional antibody titers and IFN-γ levels, inhibition of viral replication, and no signs of lung inflammation after challenge. MN vaccination conferred complete protection against lethal challenge, whereas subcutaneous vaccination induced only partial protection. These findings were further supported by high numbers of bone marrow plasma cells and spleen antibody-secreting cells detected in the MN group.

CONCLUSIONS

A single skin vaccination with MN induced potent long-lived immunity and improved protection against the 2009 H1N1 influenza virus, compared with subcutaneous injection.

Characterization of antibodies specific for hemagglutinin and neuraminidase proteins of the 1918 and 2009 pandemic H1N1 viruses

Serologic studies have detected protective immunity against 2009 pandemic H1N1 influenza virus (H1N1-2009) in some people. However, further study of preexisting immunity has been complicated by the complexity of the human immunological background. Here, we immunized mice with HA- and NA-encoding plasmids. The cross-neutralizing activity of the anti-HA antisera and the effect of the anti-NA antisera on viral infectivity were evaluated using H1N1-1918- and 2009-pseudotyped particles (pps) and an H1N1-2009 isolate. Antibodies to H1N1-2009 HA (09HA) neutralized pps harboring 09HA or H1N1-1918 HA (18HA); similarly, antibodies to 18HA neutralized pps harboring 18HA or 09HA. Antibodies to 09HA and 18HA also neutralized the H1N1-2009 virus with high efficiency. Antibodies to H1N1-1918 NA (18NA) or H1N1-2009 NA (09NA) both enhanced the infectivity of pps harboring 09NA and 18NA. Although anti-09NA and -18NA antibodies significantly reduced cytopathic effects in multiple-cycle infection assays, conversely, these antibodies enhanced the infectivity of H1N1-2009 in single-cycle infection assays. Our study demonstrates the existence of cross-protection between antibodies against these two antigenically related virus strains and shows that anti-NA antibodies have a dual effect that requires reexamination of their role in human immunity.