[The impact of conservative and hypervariable immunodominant epitopes in internal proteins of the influenza A virus on cytotoxic T-cell immune responses].

The cytotoxic T-cell immune response plays an important role in the prevention of influenza infection and reducing of the illness severity. The knowledge about mechanisms of the virus-specific CD8+ T-cell induction in humans is necessary for better understanding of influenza epidemiology and vaccine development. Due to application of new immunological and genetic methods in last years, considerable amount of.data became available in the literature about CD8+ T-cell immune responses to different influenza A viruses. This review summarizes these data. The main attention is paid to (i) heterosubtypic CTL responses to conservative immunodominant sites; (ii) mechanisms of viral escape from the virus-specific CTLs by means of evolutional escape-mutations; (iii) influence of the HLA haplotype on CD8+ T-cell immune responses. The importance of these data for immunology and vaccinology is discussed.

[Effect of Point Mutations in the Polymerase Genes of the Influenza A/PR/8/34 (H1N1) Virus on the Immune Response in a Mouse Model].

The vaccine strains for live attenuated influenza vaccines (LAIVs) have cold-adapted, temperature-sensitive, and attenuated phenotypes, which are guaranteed by the presence of specific mutations from the master donor virus in their internal genes. In this study, we used mutant viruses of the pathogenic A/Puerto Rico/8/34 (H1N1) that contained ts-mutations in PB1 (K265N, V591I), PB2 (V478L), and PA (L28P, V341L) genes along and/or in different combinations to evaluate the impact of these mutations in the immune responses. Sequential addition of tested mutations resulted in the stepwise decrease in virus-specific serum and, to a lesser extent, mucosal antibody levels. We demonstrated strong positive correlation between virus attenuation (virus titer in lung) and antibody titers. The ts-mutations in PB1, PB2, and PA genes are mostly involved in the modulation of the humoral immunity, but also have a moderate effect on the cellular adaptive immune response.

[Local antibody immune responses in influenza patients and persons vaccinated with seasonal, pre-pandemic, and pandemic live attenuated influenza vaccines].

Mucosal immunity is one of the most important factors of human anti-influenza defense. The data about local immune responses in influenza A (H3N2) patients and in persons vaccinated within 2000-2009 with different seasonal LAIVs, A (H1N1)pdm2009 LAIV, and A (H5N2) LAIV are discussed. The influenza infection resulted in the larger quantities of local IgA and IgG conversions than seasonal LAIV vaccination. 56% of young (18-21 y.o.) persons had high titers (> or = 1:64) of IgA to A (H1N1)pdm2009 virus before its circulation. 19% of persons had anti A (H5N2) IgA before vaccination. Two-fold vaccination with A (H1N1) pdm2009 and A (H5N2) LAIVs resulted in local antibody conversions in 54% and 27% of volunteers, respectively. Both these vaccines increased local IgA avidity. The number of antibody conversions after vaccination with seasonal LAIVs was in inverse dependence on their titers before vaccination. These results make it possible to conclude that the intensity of local antibody immune response to any LAIV depends on the state of local immunological memory, particularly on the presence of the crossreactive antibody-secreting B cells.

[Humoral and cell-mediated immune responses in humans to the A/California/07/ 2009 (H1N1) virus, A(H1N1)pdm2009].

During the twentieth century the world faced four influenza A pandemics: A (H1N1) in 1918, A (H2N2) in 1957, A (H3N2) in 1957 and A (H1N1) recirculation in 1977. In the beginning of 2009 the global spread of A(H1N1)pdm2009 virus was detected. In consideration of clinical evidences and genetic data analysis WHO declared as the novel pandemic of 21th century. However, the fact of exceedingly prolonged previous worldwide circulation of A (H1N1) influenza viruses was not taken into account. Further development showed epidemiological prognosis not to be accurate enough. The present work is an attempt to analyze this question from the immunological standpoint based on our studies of antibody and cellular immunity to A(H1N1)pdm2009 virus in vaccinated and non-vaccinated persons of different ages. The study results allow concluding that A(H1N1)pdm2009 is the drift variant of A (H1N1) viruses antigenically close to A/Swine/1976/1931 (H1N1). It was shown that the significant of persons have cross-reactive B and T cell immunological memory to A(H1N1)pdm2009 strain. This could be a reason of decreased A(H1N1)pdm2009 pandemic severity.

[Heterosubtypic immunity to influenza A viruses: epidemiological data, involvement of different immunological factors, vaccination].

The fact that the spread of new pandemic influenza A strains poses a constant threat to public health attracts the particular attention of scientists to heterosubtypic immunity (HIS) against different subtypes of this pathogen. This review summarizes data from the world scientific literature on studies of HIS. It presents HIS-related data on the epidemiology of influenza, immunity factors, and groundwork for the design of a universal influenza vaccine.

[Stimulation of homo- and heterologic T-cell immunological memory in volunteers inoculated with live influenza A (H5N2) reassortant vaccine].

The study deals with the ability of live attenuated reassortant influenza vaccine (LAIV) A (H5N2) to stimulate a CD4+ and CD8+ immunological memory T cell-mediated immune response in volunteers. These data were compared with the quantitative characteristics of a humoral immune response. A two-dose regimen of intranasal vaccination of avian influenza naïve people with A (H5N2) LAIV induced the production of circulating CD4+ and CD8+ memory cells specific to both A (H5N2) and seasonal A (H1N1) influenza strains. Some of the volunteers were not absolutely A (H5N2) influenza virus naïve since they had been found to have this virus-specific cross-reactive immunological memory T-cells in the prevaccination period. The content (%) of these cells varied significantly within the group. The quantitative values of postvaccination CD4+ and CD8+ memory cell accumulation were inversely related to their prevaccination level.

[Estimation of human and animal immunological memory by testing the trogocytosis of virus-specific T lymphocytes].

This study is the first attempt to evaluate the immunogenicity of Russian live attenuated influenza reassortant influenza vaccine (LAIV), by using a modified T-cell recognition of antigen presenting cells by protein capture (TRAP) method. Single vaccination of 18-20-year-old volunteers with LAIV causes an increase in the peripheral blood levels of virus-specific memory CD4+ T lymphocytes. Some (40-60%) LAIV-vaccination volunteers respond to immunization by showing a significant elevation in the peripheral blood level of memory CD4+ T cells without a systemic humoral immune response recorded in the passive hemagglutination test. Vaccination of mice with live attenuated A (H1N1) influenza reassortant virus stimulates the production of memory CD8+CD44hi T lymphocytes in the nasal-associated lymphoid tissue, the entry of infection, so does influenza infection. Vaccination with inactivated A (H1N1) influenza virus practically fails to induce these cells. A (H1N1) influenza virus-specific CD8+CD44hi T lymphocytes remain within at least 2 months (observation time). The authors' modified TRAP may be used to evaluate virus-specific immunological T-cell memory after vaccination.

[Significance of the functional activity of antibodies in influenza immunity]. / Znachenie funktsional'noi aktivnosti antitel v protivogrippoznom immunitete.

A simple and inexpensive test for mass examination of the functional activity of serum antibodies was developed. The test is based on a kinetic serologic reaction that reflects the time course of changes in antibody titers depending on the time of contact of the tested material with antigen. The curves of serum kinetic titration were processed on a computer by the special programme. As a result, an integral factor, an antibody functional activity index (AFAI) was calculated for each serum sample under study. The titers and AFAI were determined in more than 2,000 healthy persons, patients with influenza A and B, and those immunized with different influenza vaccines. The persons having similar antibody titers were demonstrated to greatly differ in AFAI. The functional activity of antibodies is a more precise marker of protection from influenza than the routine quantitative characteristics of antibodies, i.e. titers. The high baseline AFAI decreased the severity of influenza infection. Live influenza vaccines stimulated the production of antibodies having higher AFAI than inactivated ones. The live influenza strains (candidates for vaccine ones) significantly differed in their ability to stimulate the production of antibodies having a high functional activity.

[Immune response to live influenza vaccine]. / Immunnyi otvet na zhivuiu groppoznuiu vaktsinu.

Priority data on the induction, by using a Russian live cold-adapted reassortant influenza vaccine (LIV), of the cellular and humoral immunity with regard for attenuation and genetic reassortment of vaccine stains as well as with regard for the age of vaccinated persons and the production of Th1 (IFNY, IL-2) and Th2 (IL-4) cytokine markers in vitro are presented. It was demonstrated in vivo that a pathogenic virus of the A group by far more actively induced the lymphocyte apoptosis as compared with attenuated genetically reassorted stains. Unlike the influenza pathogenic virus, the genetically attenuated and reassorted strain did not produce any negative effects on the induction of cellular immunity. A comparative study of the LIV immunogenic properties in vaccinated persons showed an advantage of LIV over inactivated influenza vaccine (IIV) in stimulating the cellular and local immunity in the elderly. Unlike IIV, LIV induced an active and balanced immune response developing due to Th1 and Th2 activation. LIV was found to stimulate well enough the production of IFN and IL-2 in both young and old persons.

[Antineuraminidase serum antibodies in natural influenza A and immunization with influenza vaccines]. / Antineiraminidaznye syvorotochnye antitela pri estestvennom infitsirovanii grippom A i immunizatsii grippoznymi vaktsinami.

Parallel HI and virus-elution-from-erythrocytes-inhibition (a simplified method for titration of neuraminidase antibody) tests were used for examinations of 1117 blood serum specimens from 440 adults and children under study, 5250 single serum specimens from healthy subjects from birth to 65 years of age, 38 paired serum specimens from children who experienced influenza A/Texas/1/77 disease in the epidemic of 1979-1980, and 590 paired serum specimens from subjects immunized with influenza vaccines. In 7%-23% of influenza patients and immunized subjects antibody rise was observed to only one of the influenza A virus surface antigens, hemagglutinin or neuraminidase. The protective activity of antibody to influenza A virus neuraminidase was as good as that of antihemagglutinins. Both kinds of antibody interacted in protection against the disease. Antineuraminidase antibody was found to affect the decrease in severity of the infectious process in natural infection with influenza A. The formation of immunological memory in the system of synthesis of antihemagglutinins and antineuraminidase antibodies was shown to have features in common. The pattern of heterologous immune responses in immunized subjects and patients with influenza showed all antigenic varieties of neuraminidase N2 as well as neuraminidases N1 and N2 to share common cross-reacting determinants.

[Results of a study of collective immunity to influenza A virus (H1N1) from 1976 to 1980]. / Itogi izucheniia kollektivnogo immuniteta k virusu grippa A (H1N1) v 1976--1980 gg.

The time course of the levels of circulating antihemagglutinins to influenza A (H1N1) virus in the populations of the towns in different geographical zones of the USSR was shown to be similar. The intensity of herd immunity in some areas differed considerably, however. The population of older age groups most of whom had no clinically manifest diseases during the influenza A (H1N1) epidemic was shown to experience immunological changes upon exposure to this agent. The intensity and the rate of changes in the immunological structure of this portion of the human population exceeded similar parameters among the subjects under 20 years of age who had experienced manifest forms of infection. Some people with immunological memory to influenza A (H1N1) virus developed antibody in response to infection or immunization with influenza A (H3N2) strains.

[Specific immune response to vaccination with an inactivated flue vaccine depending on prevaccine status and age of the person vaccinated]. / Spetsificheskii immunnyi otvet na vaktsinatsiiu inaktivirovannoi grippoznoi vaktsinoi v zavisimosti ot prevaktsinal'nogo statusa i vozrasta vaktsiniruemykh.

Specific antibody immune response to vaccination with commercial inactivated trivalent vaccine A(H1N1) + A(H3N2) + B (IgA, IgG, IgG, subclasses G1, G3, G4, and accumulation of antiCD8) was studied in subjects aged 20-95 years. The initial immune status before vaccination is significant for a positive immune response to the vaccine. Subjects responding to immunization by an increment in specific IgG had a much lower prevaccination level of these antibodies than subjects without these Ig conversion. Antibody immune response to vaccination depended on patient's age. All vaccinees aged 20-25 years developed an increment in IgG to at least one of influenza antigens used. Specific postvaccinal immune response to inactivated influenza vaccine included accumulation of G1, G3, and A antibodies, but not G4 or E antibodies. This latter fact suggests the absence of sensitizing effect of vaccination. In elderly subjects an increment in G1, G3, and A antibodies may not involve an increase in the total level of IgG. In part of elderly subjects secretion of specific antibodies was observed in the presence of increased concentration of antilymphocytic antibodies (antiCD8), indicating a possibility of autoimmune reactions in subjects of this age after injection of inactivated influenza vaccine.

[Formation, persistence period and protective role of antihemagglutinins to earlier circulating influenza A viruses]. / Formirovanie, dlitel'nost' sokhraneniia i zashchitnaia rol' antigemagliutininov k ranee tsirkulirovavshim virusam grippa A.

Surveys of the population immunity as well as blood sera from human subjects vaccinated with vaccine strains done by the HI test showed the immunity to previously prevalent influenza A viruses to be maintained by anamnestic stimulation of immunogenesis occuring during circulation of the current agent. The intensity of anamnestic immunity stimulation is determined by the degree of relationship of the current strain hemagglutinin with the similar antigen of previously prevalent viruses. Circulating antibodies have a certain protective effect only against those influenza A viruses which are antigenically related within the drift alteration of hemagglutinin.

[Production and testing of lyophilized standard preparation for diagnosis of Mycoplasma pneumoniae infection by the indirect hemagglutination test]. / Prigotovlenie i ispytanie liofilizovannogo standartnogo preparata dlia diagnostiki v reaktsii nepriamoi gemaggliutinatsii Mikoplazmy pnevmonii.

A method for production of a reference lyophilized preparation for diagnosis of Mycoplasma pneumonia infections in the indirect hemagglutination (IHA) test has been developed. The method is based on conjugation using bi-diasotized benzidine of acrolein-treated sheep erythrocytes and ultrasonicated whole Mycoplasma antigen. After lyophilization the diagnostic preparation retained its standard properties for 1.5 years (the observation period). The sensitivity of the preparation in detection of antibody exceeded those of the CFT and the metabolism inhibition (MI) test 16--64-fold and the specificity was as good as in these tests. The diagnostic value of the preparation in the IHA was 78.1%, in the CFT--64.7%. As compared with the CFT and the MI test, the IHA with Mycoplasma diagnostic preparation is simple and reproducible.

[B-cell and cytotoxic lymphocyte immune response to virulent, attenuated and reassortant influenza viruses]. / B-kletochnyi i tsitotoksicheskii limfotsitarnyi immunnyi otvet na patogennye, attenuirovannye i reassortantnye virusy grippa.

The quantitative estimation of the production of the virus specific IgA-, IgM-, IgG1, IgG2a, IgG2b and IgG3-antibody secreting B-cells (ASC) and extent of the immune response of the cytotoxic T-lymphocytes was carried out in mice after primary and secondary immunization with the parental cold adapted (ca) virulent epidemic wild-type (wt) master strain viruses and their reassortant variant (RV) with the incorporated in their genom different genes from ca master strain. The chick embryo derived ca master strain virus A/Len/134/47/57 (H2N2) reduced or eliminated the viral potency to induce the primary B-cellular response. Reassortant incorporation of wt derived HA and NA genes into the ca virus genome restored the virus immunogenic activity concerning the ASC production, but at the lower level than parental virulent virus. Reassortance of the viruses according to generally accepted genom formula 6/2 was associated with decrement of the functional activity of the cytotoxic T-lymphocytes memory and of the primary immune response especially. The data obtain demonstrate the necessity for the control of the immunogenicity of the reassortant viruses at the cloning stage.

[Monoclonal immunoenzyme test-system for evaluating secretory immunity to influenza A and B viruses]. / Monoklonal'naia immunofermentnaia test-sistema dlia otsenki sekretornogo immuniteta k virusam grippa A i B.

Enzyme immunoassay system has been developed for measuring the titers of secretory IgA in secretion from the upper respiratory airways (SURA). Russian ingredients are used. The conjugate includes monoclonal antibodies to heavy chains of human secretory IgA. The sensitivity and specificity of the kit was tested with SURA of normal subjects and patients with influenza. The initial level of specific secretory IgA antibodies detected by the kit clearly correlated with defense from natural influenza infection. The protective concentrations of the antibodies corresponded to at least 1:64 dilutions. The titers of serum and secretory antibodies in convalescents after influenza A or B were virtually the same. The level of secretory antibodies dropped sooner than that of serum antibodies.

[Influenza vaccine stimulation of antibodies to different variants of influenza A virus]. / Stimuliatsiia grippoznymi vaktsinami antitel k razlichnym variantam virusa grippa A.

The capacity of live influenza type A (H3N2) vaccines to produce antihemagglutinins and antineuraminidase antibody to drift variants of a given serosubtype emerging later than the vaccine strain was studied. For this purpose, a wider set of antigens was used to examine retrospectively by the HI and virus elution from erythrocyte inhibition tests the paired sera from the subjects immunized in 1975 and 1976 with live vaccine virus strains similar to A/Port Chalmers/1/73 (H3N2) and A/Victoria/3/75. These vaccines were shown to actively stimulate antibody production in titres of 1:40 or higher to strains forestolling the vaccine strain by 1 (antihemagglutinins) and 2 (antineuraminidase antibody) degrees of the antigenic hierarchy. The intensity of production of both kinds of antibody to similar future strains depended on the intensity of immune response to the vaccine virus. By increasing the dose and frequency of administration of the virus serosubtype A (H3N2) to animals it was possible to intensify the production of antihemagglutinins and antineuraminidase antibodies to later drift variants of this agent with respect to the virus-immunogen. Volunteers immunized in 1983 with a commercial inactivated chromatographic bivaccine prepared from the strains similar to A/Bangkok/1/79 (H3N2) and A/Brazil/14/78 (H1N1) were found to intensively produce antihemagglutinins in titres of 1:40 or higher to viruses A/Philippines/2/84 (H3N2), A/Leningrad/167/83 (H3N2), A/Leningrad/3/82 (H1N1) but not to A/Dunedin/27/83 (H1N1) virus.

[Formation and protective functions of antibodies to neuraminidase of the influenza A virus]. / Formirovanie i zashchitnye funktsii antitel k neiraminidaze virusa grippa A.

The features of production and protective properties of antineuraminidase antibodies in subjects of various ages with influenza infection caused by currently important influenza A virus strains of H1N1 and H3N2 serosubtypes were studied. In children, antineuraminidase antibodies were found to accumulate less intensively than in adults and in infants under 1 year they were detected extremely rarely. In young infants, their titres after the disease decreased more rapidly than antihemagglutinin titres. As compared with adults, in younger children these antibodies have a higher protective role in modifying the severity of influenza infection. A direct correlation between the age of the children and the levels of antineuraminidase antibodies demonstrable in them was established. Within the same period of time, ratio of antihemagglutinins and antineuraminidase antibodies was shown to differ significantly in the population of different regions of the country. The results of trials in volunteers of 10 strains as candidates for a live influenza type A vaccine (H3N2) indicate considerable variability of the immunogenic potency of hemagglutinin and neuraminidase of these strains.

[The role of antibody functional activity in the protection of people against influenza]. / Rol' funktsional'noi aktivnosti antitel v zashchishchennosti liudei ot grippa.

Indices of the functional activity of specific serum antibodies (IFAA) before and after outbreaks of influenza A (H3N2) and B were determined in 164 subjects of 18-20 years of age from the military communities observed in 1987-1988. The IFAA were calculated on the basis of kinetic HI tests followed by computer processing according to the program developed by the authors. The IFAA were found to indicate the protection of human subjects against influenza, reflecting the state of resistance to influenza more exactly than antibody titres. High initial IFAA correlated with lower severity of influenza infection. The IFAA to the same strain may differ significantly in individual subjects. In patients with influenza the time course of antibody titres did not coincide with dynamic changes in IFAA.

[Indicators of collective immunity to influenza depending on the blood group and sex of the population]. / Pokazateli kollektivnogo immuniteta k grippu v zavisimosti ot gruppi krovi i pola obsleduemogo naseleniia.

Immunological investigations of the time course of serum anti-HA and anti-NA antibodies against influenza A and B viruses in the female and male population with blood groups 0(I), A(II), B(III), and AB(IV) were carried out for several months. The persons with the blood group AB (IV) were shown to be most sensitive to influenza A and B. They were affected by the epidemic virus earlier and more severely than those with the other blood groups. A special method is proposed for prediction of the etiology of the forthcoming epidemic. A correlation between blood groups and titres of anti-HA but not anti-NA antibodies was observed. The view on the lack of the genetic factor influence on the affliction with influenza and antibody response in persons of different sexes is substantiated.