IgM and IgG antibody responses after immunization of children with inactivated monovalent (A/New Jersey/76) and bivalent (A/New Jersey/76-A/Victoria/75) influenza virus vaccines

Efficient protection of mice from influenza A/H1N1pdm09 virus challenge infection via high avidity serum antibodies induced by booster immunizations with inactivated whole virus vaccine

The immunogenicities of inactivated whole and split virus vaccines derived from influenza A/H1N1pdm09 virus were compared in a mouse model. We demonstrated the unique properties of whole virus vaccine boosters on the serum memory antibody response in mice. Consistent with previous studies, booster immunization with either whole or split virus vaccines of A/H1N1pdm09 virus produced comparable titers of serum antibodies with hemagglutination inhibition and virus-neutralizing activities. However, superior protection against the challenge infection was unexpectedly observed in mice primed and boosted with whole virus vaccines compared with those treated with split virus vaccines, despite similar levels of antibody titers in each group. Immune serum antibodies were shown to be primarily responsible for this protection via passive transfer experiments of immune serum antibodies to naive recipient mice. Moreover, this protection correlated with elevated affinity maturation of the antibodies. Thus, booster immunization with whole virus vaccines elicited a robust serum antibody response with high avidity to the virus, which was not measurable via conventional serological assays.

Impact of Influenza Vaccine Formulation with a Detailed Analysis of the Cytokine Response

Vaccination provides the most effective method of limiting the impact of influenza. Inactivated influenza vaccines are available in three formulations and more information needs to be generated on how antigen presented in different vaccine formulations influences the subsequent immune response. In the present study, we have investigated the effect of two different influenza vaccine formulations on the resulting antibody and cytokine responses and compared these responses with influenza infection. Mice were vaccinated intramuscularly with one or two doses of whole or split virus vaccine or alternatively intranasally infected with influenza virus. Lymphocytes were isolated from spleen cells and stimulated in vitro for 24 or 72 h for analysis of cytokine profile at the gene expression and at the protein level. Additionally, whole blood was collected and the serum antibody response investigated by haemagglutination inhibition (HI) and enzyme-linked immunosorbent assay (ELISA). We found that one dose of whole virus vaccine induced higher antibody and cytokine responses and thus was more immunogenic in unprimed mice than split virus vaccine. Whole virus vaccine induced a strong IFN-gamma (type 1) immune response after one dose of vaccine and a more mixed cytokine response after the second dose. Split virus vaccine induced a type 2 response, particularly after two vaccine doses. Our results show that two doses of vaccine (both vaccine formulation) were more effective in induction of Th2 type of cytokines and thus indicate that both the formulation and also the number of vaccine doses substantially influences the magnitude and quality of the immune response.

Two Doses of Parenterally Administered Split Influenza Virus Vaccine Elicited High Serum IgG Concentrations which Effectively Limited Viral Shedding upon Challenge in Mice

We have previously found that whole influenza virus vaccine induced a more rapid and stronger humoral response, particularly after the first dose of vaccine, than split virus vaccine in mice. In this study, we have evaluated the protective efficacy of whole and split influenza virus vaccines in mice using a nonlethal upper respiratory tract challenge model. We have also investigated the immunological correlates associated with no or very little viral shedding after viral challenge. Vaccination resulted in reduced viral shedding and shortened the duration of infection by at least 2 days. After one dose of vaccine, whole virus vaccine generally resulted in less viral shedding than split virus vaccine. In contrast, two doses of split virus vaccine, particularly the highest vaccine strengths of 15 and 30 microg HA, most effectively limited viral replication and these mice had high concentrations of prechallenge influenza-specific serum IgG. The vaccine formulation influenced the IgG2a/IgG1 ratio, and this IgG subclass profile was maintained upon challenge to some extent, although it did not influence the level of viral shedding. The concentration of postvaccination serum IgG showed an inverse relationship with the level of viral shedding after viral challenge. Therefore, serum IgG is an important factor in limiting viral replication in the upper respiratory tract upon challenge of an antigenically similar virus.

Whole influenza virus vaccine is more immunogenic than split influenza virus vaccine and induces primarily an IgG2a response in BALB/c mice

The aim of this study was to compare the kinetics and the magnitude of the humoral immune response to two different influenza vaccine formulations, whole and split virus vaccines. BALB/c mice were immunized intramuscularly with one or two doses (3 weeks apart) of 7.5, 15 or 30 microg of haemagglutinin of monovalent A/Panama/2007/99 (H3N2) split or whole virus vaccine. The two vaccine formulations induced similar kinetics of the antibody-secreting cells response; however, differences in the magnitude were observed in the spleen and bone marrow. Vaccination with whole virus vaccine generally elicited a quicker and higher neutralizing antibody response, particularly after the first dose of vaccine. The two vaccine formulations gave different immunoglobulin G (IgG) subclass profiles. Split virus vaccine stimulated both IgG1 and IgG2a antibodies suggestive of mixed T-helper 1 (Th1) and Th2 response, whereas whole virus vaccine induced mainly an IgG2a antibody response, which is indicative of a dominant Th1 response. The increased immunogenicity of whole virus vaccine in a naïve population could reduce the vaccine concentration needed to provide protective immunity.

[Influenza]

Influenza is the last great uncontrolled plague of mankind. Pandemics and epidemics occur at regular time intervals. The influenza viruses are divided into the types A, B and C and show unique variability of their surface antigens (hemagglutinin and neuraminidase). Influenza viruses of type A show the largest degree of antigenic variation which, in turn, resulted in the definition of a number of subtypes, each comprising many strains. By comparison, influenza viruses of types B and C exhibit much less variation of their surface antigens. As a consequence, no subtypes but many different strains have been recognized. The degree of antigenic variation correlates with the epidemiologic significance of the virus types, type A being the most and type C the least important. Two different kinds of antigenic variation have been recognized: In the case of minor variation of one or both surface antigens, the term "antigenic drift" is employed. Antigenic drift occurs with all three types of virus, it is caused by point mutations which increase the chance of survival of mutants in the diseased host. In addition, influenza A viruses show sudden and complete changes of their surface antigens in regular time intervals, resulting in the appearance of new subtypes. This event is called "antigenic shift". The mechanisms responsible for antigenic shift are poorly understood, only. In addition to the recycling of preceding subtypes, reassortment resulting from double infection of cells with strains of human and animal origin are considered possible explanations. By use of modern DNA recombinant technology, the base sequences of a series of virus genes and, as a consequence, the amino acid sequence of the corresponding antigens have been determined. By means of monoclonal antibodies, the antigenic structure of many influenza antigens has been further elucidated. It can be expected that further research on the molecular basis of antigenic variation could finally result in an understanding of the causal mechanisms. It is an outstanding feature of the epidemiology of influenza A viruses that a family of related strains prevails for a certain period of time and disappears abruptly as a new subtype emerges.(ABSTRACT TRUNCATED AT 400 WORDS)

Vaccination against virus diseases

One of the most important and most lasting benefits of medicine to human health and health expenditure is the controlled immunological interruption of the vicious cycle of infectious disease such as smallpox, poliomyelitis, yellow fever, measles. Smallpox, with globally more than 2.5 million cases ten years ago, is gone. The incidence of infectious diseases with available immunoprophylaxis has been reduced by 90 % over the past two decades, while the incidence of diseases without vaccine has nearly tripled. By contrast, influenza, a disease against which there have been vaccines in existence for many years, demands more deaths than any other infectious disease. Reasons for this failure of influenza immunoprophylaxis are discussed and suggested to include: indiscriminate use of available vaccines of which some types are much less antigenic than others, the disappointment that influenza virus vaccines will not protect against influenza-like illnesses caused by noninfluenza virus pathogens and the concomitant indiscriminate rejection of all influenza vaccines as being of doubtful value; superficial vaccination policies which aim at narrow populations, leaving those most likely to spread the virus the full potential to do so; the unjustified fear of side reactions following vaccination which are considerably less severe than the disease this vaccination is attempting to prevent.

Antibody response to monovalent A/New Jersey/8/76 influenza vaccine in pregnant women

The decision to implement a mass immunization program with A/New Jersey/8/76 (Hsw1N1) influenza vaccine provided a unique opportunity to evaluate immunological responses during pregnancy. Fifty-nine pregnant and 27 nonpregnant women participated in this study. Influenza virus hemagglutination-inhhibition antibody titers were determined to A/New Jersey/8/76 (Hsw1N1), A/Japan/305/57 (H2N2), and A/Hong Kong/8/68 (H3N2) before and after a single dose of monovalent (200 chick cell agglutination units) influenza A/New Jersey/8/76 (Hsw1N1) vaccine. The difference in titers between pregnant and nonpregnant women was insignificant. Treatment of the sera with 2-mercaptoethanol disclosed a similar immunoglobulin M response to the vaccine in both groups. The mean fold rise in heterologous antibody titer was similar in pregnant and nonpregnant women. This study demonstrated that pregnant women were able to respond to an original myxovirus antigen, influenza A/New Jersey/8/76, in a manner equivalent to nonpregnant, age-matched controls.

Responses of patients with neoplastic diseases to influenza virus vaccine

Little information is available concerning influenza immunization in patients with malignancies receiving chemotherapy. A large number of ambulatory patients are receiving chemotherapy for metastatic disease as well as adjuvant chemotherapy for microscopic disease, and they should be considered at higher risk for complications should they contract influenza. Seventeen oncology patients and 15 control subjects were given bivalent influenza vaccine (A/NJ/76-A/Vic/75) and their serologic responses were monitored. Although their responses were less than controls, nearly 50% of the oncology patients had a greater than fourfold rise in antibody titer, suggesting that a humoral antibody response could be achieved in spite of their underlying disease and immunosuppressive chemotherapy. No adverse reactions or deterioration of patient's clinical status were noted with vaccination. We conclude that significant antibody titer responses can be achieved in this population of patients.