Emergency Medical Service Personnel Recognize Pediatric Concussions.

Concussions are a major cause of morbidity in pediatrics. Many concussions occur during activities with emergency medical service (EMS) providers present to determine if a higher level of care is needed. Data are limited on how capable these providers are. We assessed the ability of EMS providers to recognize pediatric concussions. Fifty-six total responses were included, 38 from EMS and 18 from our MD/RN (medical doctor/registered nurse) group. No statistical differences were found between the 2 groups when adjusted for age, gender, number of years in practice, and number of pediatric concussions managed. This first of its kind pilot study was designed to assess EMS personnel's ability to recognize and triage pediatric concussions. Our findings show EMS providers are statistically identical in their ability to recognize and triage concussions to physicians. The performance of our MD participants was lower than expected. Larger studies are needed to further investigate EMS providers' ability to recognize a concussion.

Influenza viral neuraminidase: the forgotten antigen.

Influenza is the most common cause of vaccine-preventable morbidity and mortality despite the availability of the conventional trivalent inactivated vaccine and the live-attenuated influenza vaccine. These vaccines induce an immunity dominated by the response to hemagglutinin (HA) and are most effective when there is sufficient antigenic relatedness between the vaccine strain and the HA of the circulating wild-type virus. Vaccine strategies against influenza may benefit from inclusion of other viral antigens in addition to HA. Epidemiologic evidence and studies in animals and humans indicate that anti-neuraminidase (NA) immunity will provide protection against severe illness or death in the event of a significant antigenic change in the HA component of the vaccine. However, there is little NA immunity induced by trivalent inactivated vaccine and live-attenuated influenza vaccine. The quantity of NA in influenza vaccines is not standardized and varies significantly among manufacturers, production lots and tested strains. The activity and stability of the NA enzyme is influenced by concentration of divalent cations. If immunity against NA is desirable, a better understanding of how the enzymatic properties affect the immunogenicity is needed.

Recombinant influenza B virus HA and NA antigens administered in equivalent amounts are immunogenically equivalent and induce equivalent homotypic and broader heterovariant protection in mice than conventional and live influenza vaccines.

Influenza B virus is an important cause of acute upper respiratory disease in humans. Vaccination is the primary method of control of influenza related disease, yet vaccine methodology and production technology have not changed in over 40 years. In this study, we compare the efficacy of recombinant baculovirus produced protein based neuraminidase containing influenza B vaccines with conventional inactivated influenza vaccine (CIV) and live-attenuated influenza vaccine (LAIV) in a murine model. All HA containing vaccines stimulated antibody and protected against an infectious challenge with homotypic virus (B/Harbin/7/94), only recombinant protein based (rHA + rNA and rNA) vaccines containing immunogenic amounts of influenza neuraminidase (NA) protected against challenge with a significantly antigenically different heterovariant virus (B/Beijing/243/1997), as measured by a reduction in mean pulmonary virus titers. This report demonstrates with influenza B virus, in a side-by-side comparison with CIV and LAIV in a murine model system the superiority of vaccines containing immunogenic NA over currently approved CIV and LAIV vaccines.

A call to cellular & humoral arms: enlisting cognate T cell help to develop broad-spectrum vaccines against influenza A.

Influenza A is an important cause of morbidity and mortality worldwide. In the United States alone influenza kills 30,000 to 50,000 people in a non-epidemic year and significantly more in an acute epidemic.(1) An emerging pandemic influenza virus, such as H5N1, could have a devastating economic and social impact. The Surgeon General estimates that at least 43 million Americans, especially those younger than 1 and older than 60, are at risk of death from influenza. Antigenically distinct influenza virus strains emerge regularly, mandating changes in influenza vaccine antigenic composition. Consequently, the immunity engendered by the conventional influenza vaccines is relevant only for a short time. However, by incorporating conserved influenza T cell epitopes, it may be possible to develop more immunogenic, broader-spectrum vaccines that may be efficacious over a longer period. This review summarizes the critical components of effective influenza vaccines, a rational vaccine design approach, and the pertinent influenza immunology.

Changing perspective on immunization against influenza.

Current vaccination strategies against influenza rely on decades old technology of strain selection and prolonged labor-intensive, embryonated chicken-egg based production methods. Although, containing both major surface glycoproteins, hemagglutinin (HA) and neuraminidase (NA), the immunity engendered by these vaccines is dominated by the anti-HA response. Consequently, current vaccines are susceptible to failure resulting from significant antigenic drift or shift in the time elapsing from the selection of the vaccine candidate strain and wild-type virus exposure. Therefore, immunity may be of short duration. There must be a change in vaccine strategy to include immunization with both HA and NA to broaden the immune response against influenza. Inclusion of the more slowly evolving NA in a vaccine against influenza will reduce the vulnerability to antigenic changes in a potential emerging influenza virus. Alternative production technologies such as recombinant baculovirus and yeast should be explored to decrease vaccine production times.

Variation in the divalent cation requirements of influenza A virus N1 neuraminidases.

Enzymatic kinetic parameters of influenza A virus N1 neuraminidases (NA) chromatographically purified from several vaccine candidate strains were tested. With ionic strength held constant, Ca2+ or Mg2+ increased the initial rate of enzymatic activity. The 1934 and 1943 strains had statistically significant highest initial velocities, V(max)/K(m) and V(max). There were no significant differences among the influenza virus strains from 1947 to 1991. Measured K(m) for the 1943 strain (6.2 x 10(-5) M) was significantly higher than other strains (3.1-4.7 x 10(-5) M). V(max)/K(m) varied from 0.78 M(-1) s(-1) to 0.91 M(-1) s(-1) and V(max) varied from 3.0 s(-1) to 5.5 s(-1) before the addition of a divalent cation and increased approximately 2-fold for each of these kinetic parameters for each strain after the addition of exogenous Ca2+ or Mg2+. Dialysis reduced the initial velocity and immunogenicity of each strain with significant differences found among strains. Enzymatic activity and immunogenicity were partially restored by the addition of exogenous Ca2+. Nucleic acid sequence analysis could not predict these differences. Selection of vaccine strains must include analysis of antigenic changes, but also enzymatic studies and determination of the requirement of divalent cations to maintain immunogenicity and activity during production.

Immunization against influenza A virus: comparison of conventional inactivated, live-attenuated and recombinant baculovirus produced purified hemagglutinin and neuraminidase vaccines in a murine model system.

To simulate the 2003-2004 influenza season and compare available vaccination methods, immunologically naive mice were immunized with: influenza A virus hemagglutinin (rHA) and neuraminidase (rNA) from A/Panama/2007/99 H3N2 or A/Fujian/411/2002 H3N2 expressed by recombinant baculovirus, chromatographically purified, either as single antigens (rHA or rNA) or in combination (rHArNA); conventional inactivated monovalent (CIV) vaccines from each heterotypic strain; or a live-attenuated influenza (LAV) vaccine derived from the A/Panama/2007/99 strain. HA containing vaccines were highly immunogenic for the HA antigen, with no statistically significant differences among groups in the amount of homotypic anti-HA antibody induced. Little cross-reactive anti-HA antibody was induced by any vaccine, including LAV. Statistically, the greatest amount of anti-NA antibody was induced by the purified NA alone or in combination with purified HA; the least amount of anti-NA antibody was found in mice immunized with LAV or CIV. Immunization with vaccines immunogenic for both HA and NA resulted in an immune response to both surface glycoproteins that suppressed homotypic, closely related heterotypic infection and had a greater reduction in mPVT following an infectious challenge by a distantly related heterotypic strain. These studies suggest that vaccines immunogenic for both HA and NA offer an increased level of protection from influenza.

Protection of mice with recombinant influenza virus neuraminidase.

Contemporary influenza vaccines are standardized with respect to their content of hemagglutinin, the major virus antigen. Although the immunizing effect of viral neuraminidase--the less abundant of the 2 major surface glycoproteins--has been well documented in experimental animals, the importance of the purified recombinant protein has not yet been adequately assessed in animals or humans. We demonstrate that different lots of a baculovirus-derived recombinant N2 protein, in the absence of other influenza virus proteins, can induce neuraminidase-specific antibodies, reduce the replication of both homologous and heterovariant virus in mice, and suppress disease, as it is manifested by total body weight loss.

Variation in the divalent cation requirements of influenza a virus N2 neuraminidases.

Influenza virus N2 neuraminidases were chromatographically purified from several vaccine candidate strains from 1957 to 1994. Enzymatic kinetic parameters and immunogenicity were tested for each strain. For each NA tested, with ionic strength held constant, Ca(2+) or Mg(2+) increased the initial rate of enzymatic activity. Earlier N2-NA strains had the highest initial velocity, V(max)/K(m) and V(max). There were significant differences among the influenza virus strains in enzymatic activity before and after addition of Ca(2+) or Mg(2+): V(max)/K(m) varied from 0.54 M(-1) s(-1) to 0.88 M(-1) s(-1) and V(max) varied from 2.45 s(-1) to 4.3 s(-1) before the addition of a divalent cation; and increased approximately 2-fold each of these kinetic parameters for each strain after the addition of exogenous Ca(2+) or Mg(2+). Exhaustive dialysis with EDTA reduced the initial velocity of each strain with significant differences found among strains, with a range of 0.1% to 8% of original activity. Activity was partially restored by the addition of exogenous Ca(2+) or Mg(2+), varying from 8% to 60% of pre-dialysis levels, but original rates were not achieved. This reduction in enzymatic activity for the tested strains (i.e., A/Japan/57 and A/Johannesburg/94) was accompanied by a parallel decrease in NA-immunogenicity, with antibody response decreasing by as much as 76% as measured by NI titer, and ELISA titer decreasing by as much as 68%. The addition of Ca(2+) or Mg(2+) to the post-dialysis sample restored immunogenicity to as much as 80% of pre-dialysis NI titers and as much as 78% of pre-dialysis ELISA titers. Dialysis had the least effect on early strains as measured by enzymatic kinetic parameters and immunogenicity studies. Zn(2+) had a slight inhibitory effect on the activity of all tested strains. Review of the nucleic acid sequence of each of these strains could not predict their enzymatic activity, immunogenicity or response to dialysis. If immunity against neuraminidase is desirable in vaccination against influenza, selection of vaccine candidate strains must include not only analysis of antigenic changes and sequence analysis but also enzymatic studies and determination of the requirement of divalent cations to maintain immunogenicity and activity during production.

The total influenza vaccine failure of 1947 revisited: major intrasubtypic antigenic change can explain failure of vaccine in a post-World War II epidemic.

Although vaccine-induced immunity to influenza A virus is continually challenged by progressively selected mutations in the virus's major antigens (antigenic drift), virus strains within a subtype (e.g., H1N1) are antigenically cross-reactive. Although cross-immunity diminishes as further mutations accumulate, necessitating frequent changes in vaccine strains, older vaccines are usually partially protective. The post-World War II epidemic of 1947 is notable for the total failure of a vaccine previously effective in the 1943-44 and 1944-45 seasons. We have combined extensive antigenic characterization of the hemagglutinin and neuraminidase antigens of the 1943 and 1947 viruses with analysis of their nucleotide and amino acid sequences and have found marked antigenic and amino acid differences in viruses of the two years. Furthermore, in a mouse model, vaccination with the 1943 vaccine had no effect on infection with the 1947 strain. These findings are important, because complete lack of cross-immunogenicity has been found previously only with antigenic shift, in which antigenically novel antigens have been captured by reassortment of human and animal strains, sometimes leading to pandemics. Although the 1947 epidemic lacked the usual hallmarks of pandemic disease, including an extensive increase in mortality, it warns of the possibility that extreme intrasubtypic antigenic variation (if coupled with an increase in disease severity) could produce pandemic disease without the introduction of animal virus antigens.

Supplementation of conventional trivalent influenza vaccine with purified viral N1 and N2 neuraminidases induces a balanced immune response without antigenic competition.

Influenza viruses neuraminidase (NA) were chromatographically extracted from influenza viruses A/Nanchang/933/95 H3(NC)N2(NC) [R] and A/Johannesburg/82/96 H1(JH)N1(JH) [R] and used to supplement conventional inactivated trivalent influenza vaccine. Immunization of mice with this preparation resulted in high titers of antibodies to both hemagglutinins (HA) and neuraminidases (NA); there were no significant differences in the anti-HA antibody titers between the conventional and the supplemented vaccine preparation. Likewise, there were no significant differences in anti-NA antibody titers between the supplemented vaccine and titers from mice immunized with a neuraminidase vaccine containing a mixture of N1-NA and N2-NA. There was no evidence of a diminution of the immune response to the HA components of the vaccine despite the presence of antigenically equivalent amounts of both N1-NA and N2-NAs. Homotypic and distantly related heterotypic infections for both H1, N1 and H3N2 subtypes were suppressed and greater reduction in pulmonary virus titers (PVT) were observed in the trivalent vaccine supplemented with purified neuraminidase from each subtype, N1 and N2. Effects on the influenza B viral components were not studied. Previous studies on supplementation of conventional influenza vaccine focused only on monovalent H3N2 vaccine preparations; this study demonstrates in a mouse model system that supplementation of trivalent influenza vaccine with both influenza A subtype neuraminidases, N1 and N2 is highly immunogenic for HA and NA of each subtype and efficacious in protecting against influenza from homotypic and heterotypic infectious challenges of either subtype.