Enhancement of anti-influenza A virus cytotoxicity following influenza A virus vaccination in older, chronically ill adults.

We studied anti-influenza cytotoxicity by bulk peripheral blood mononuclear leukocyte (PBL) cultures derived from older, chronically ill volunteers undergoing vaccination. Vaccinees received either cold-recombinant, live-attenuated influenza A/Korea/1/82 (H3N2) virus intranasally or inactivated monovalent influenza A/Taiwan/1/86 (H1N1) subvirion vaccine intramuscularly. PBL were collected pre- and postvaccination and in vitro stimulated by autologous PBL infected with influenza A virus homologous and heterosubtypic to the respective vaccine strain. Cytotoxicity was measured against influenza A virus-infected autologous and human leukocyte antigen (HLA)-mismatched PBL targets infected with influenza A virus homologous or heterosubtypic to the vaccine virus strain. Vaccinees infected with the live-attenuated virus developed significant rises in mean anti-influenza, HLA-restricted cytotoxicity that was cross-reactive against influenza A viruses homologous and heterosubtypic to the vaccine virus. The enhanced cross-reactive cytotoxicity was inducible postvaccination by in vitro stimulation with autologous PBL infected with the homologous influenza A (H3N2) virus and with influenza A (H1N1) virus. In contrast, after vaccination with inactivated monovalent subvirion vaccine, volunteers developed significant increases in mean anti-influenza, HLA-restricted cytotoxicity only against autologous PBL infected with homologous influenza A (H1N1) virus. Increased cytotoxicity occurred only after in vitro stimulation with autologous cells infected with homologous influenza A (H1N1) virus. Mean gamma interferon levels in supernatant fluids of influenza A virus-stimulated effector PBL did not increase postvaccination, despite increased levels of anti-influenza cytotoxicity displayed by the effector cells. We conclude that the live-attenuated influenza A virus infection induced a broader range of enhanced anti-influenza cytotoxicity than did the inactivated subvirion vaccine.     

Lymphocyte cytotoxicity to influenza virus-infected cells: response to vaccination and virus infection

Peripheral blood leukocytes obtained from volunteers at various times following influenza vaccine or live influenza virus infection were assayed for cytotoxicity against influenza virus-infected cells. Cytotoxicity was highest on days 3 and 7 following vaccination with commercial A/Port Chalmers/1/73 inactivated influenza virus vaccine. Maximal cytotoxicity was found 9 days after infection induced by intranasal inoculation of a strain of A/Scotland/840/74 influenza virus. Individuals naturally infected with A/Victoria/3/75 were also found to have elevated cytotoxicity approximately 1 week after onset of illness. Cytotoxicity levels decreased toward base line approximately 30 days after the virus exposure. The effector mechanism(s) responsible for the early, transient elevation in specific immune release to influenza virus-infected cells may be different from the antibody-dependent cell cytotoxicity demonstrated in the peripheral blood leukocytes from volunteers who had a remote experience with influenza virus.     

Decreased cell-mediated cytotoxicity against virus-infected cells in systemic lupus erythematosus.

Cell-mediated cytotoxicity, directed against virus-infected tissue culture cells, was studied with peripheral blood mononuclear cells from 11 patients with systemic lupus erythematosus (SLE) and 12 matched, normal subjects in a 51Cr release assay. Baseline (preimmunization) levels of cytotoxicity against target cells infected with influenza A/Victoria, influenza B/Hong Kong, Newcastle disease virus, and herpes simplex virus were significantly decreased in patients with SLE compared to normal subjects (P less than 0.001), although serum antibody levels to the respective viruses were similar in both groups. After intramuscular administration of inactivated influenza A/Victoria vaccine, SLE patients failed to generate elevated levels of cytotoxicity against A/Victoria-infected cells, in contrast to normal subjects. SLE patients responded with levels of serum hemagglutination-inhibition antibody which were similar to those of normal subjects. Thus, SLE patients manifest decreased cell-mediated cytotoxicity against virus-infected target cells, although humoral antibody responses appeared to be intact. Studies of SLE patients with influenza may help to define the role of cell-mediated immunity in the pathogenesis of certain viral infections.     

The immunological response of pigs and Guinea pigs to antigens of African swine fever virus

Summary Pigs vaccinated with glutaraldehyde-fixed alveolar macrophages (AM) infected with African swine fever virus (ASFV) had an accelerated serological response after subsequent challenge and a slight reduction in levels of viraemia. Vaccination of pigs with detergent-treated infected AM produced no detectable serological response and no protection against homologous challenge.Guinea pigs were vaccinated with glutaraldehyde-fixed ASFV-infected cells, detergent-treated infected cells, detergent-treated infected spleen homogenate, purified ASFV or sonicated infected cells. Antibody was detectable by ELISA after vaccination with all preparations except the detergent-treated infected spleen vaccine. However, vaccination with purified ASFV or sonicated infected cells induced antibodies that were also strongly reactive in antibody-dependent cell-mediated cytotoxicity and complement-mediated lysis assays. If such antibodies are protective, immunization of pigs with purified ASFV or sonicated infected cells may induce a protective immunity.     

Gamma interferon-mediated cytotoxicity related to murine Chlamydia trachomatis infection.

After infection with the mouse pneumonitis agent (MoPn; murine Chlamydia trachomatis), heterozygous (nu/+) but not nude athymic (nu/nu) mice produced enhanced amounts of gamma interferon (IFN-gamma) in vitro in response to MoPn antigen that exhibited cytotoxic activity when added to host cells already infected with chlamydiae. Antibody-complement lysis showed the cytotoxic activity to be dependent, at least in part, on L3T4+ T cells for production. The cytotoxic responses were directed primarily against Chlamydia-infected target cells, but a second type of toxicity was demonstrable against uninfected target cells after treatment of the generating cell population with anti-Lyt-2 antibody plus complement at certain time points after infection. This additional nonspecific cytotoxic activity was presumably due to a second factor (factor X) acting in concert with IFN-gamma. Lyt-2+ cells, however, also were shown to play a role in IFN-gamma production and cytotoxicity directed against infected targets at later time points after infection. Neutralization of IFN-gamma in the samples containing cytotoxic activity abrogated the cytotoxicity against both infected and uninfected targets, but cloned murine IFN-gamma exhibited toxicity in a dose-dependent manner only against infected target cells. The data provides evidence that cytotoxicity against infected targets is due to antigen-specific induction of IFN-gamma, but other cytokine activity, most demonstrable after removal of Lyt-2.2+ cells and cytotoxic to uninfected targets, also is present.     

Cytomegalovirus-specific cytotoxicity mediated by non-T lymphocytes from peripheral blood of normal volunteers.

The cytotoxicity of circulating mononuclear cells from normal volunteers was determined using human leukocyte antigen (HLA)-typed, low-passaged human skin fibroblasts infected with cytomegalovirus as target cells. Peripheral blood lymphocytes from both seropositive and seronegative individuals possessed virus specific cytotoxicity. Although all target cells used were susceptible to virus specific lysis, lymphocytes from some individuals were more active against some target cells than others. This differential cytotoxicity did not follow a consistent pattern of HLA restriction. Some variations in cytotoxic activity were noted on sequential studies of individual volunteers. Studies of fractionated lymphocytes from selected immune and nonimmune individuals demonstrated that cytotoxicity of lymphocytes from both groups was mediated by nonadherent, Fc receptor bearing cells which did not form rosettes with sheep erythrocytes. Repeated washing sometimes decreased cytotoxicity of lymphocytes from immune individuals, and addition of serum containing antibody to cytomegalovirus enhanced cytotoxicity, suggesting antibody dependence. It is concluded that cytotoxic lymphocytes from nonimmune volunteers possessed characteristics of natural killer cells, whereas those from immune volunteers probably consisted of both natural killer cells and antibody-dependent killer cells.     

Aujeszky's disease vaccination and infection of pigs with maternal immunity: Effects on cell- and antibody-mediated immunity

Summary SCC, ADV-SCC, ADV-ADCC and ADV-LYST as well as ND₅₀-titres of neutralizing serum antibodies were examined in 36 passively immune pigs, 25 of which were vaccinated at 3 weeks of age and partly revaccinated 3 weeks later. Twenty-five vaccinated animals and 8 non-immune control pigs were challenged with infectious ADV.Independent of the state of maternal immunity the cytotoxic response of the white blood cells from all the animals was low at WPP 3 but rose with increasing age. ADV-LYST occurred only in some of the animals. A single vaccination evoked no significant effect on our immune parameters, but revaccination led to higher ADV-LYST and ADV-ADCC. In pigs vaccinated at WPP3 the neutralizing serum titres decreased gradually, similar to unvaccinated animals, indicating that the antibodies were of maternal origin. However, after vaccination at WPP6, no further decline of ND₅₀-titres could be detected, pointing to a limited antibody production. Animals vaccinated at WPP3 and revaccinated 3 weeks later showed a significant increase of serum neutralizing titres.Whereas the controls showed typical symptoms of Aujeszky's disease, the immune animals, especially the unvaccinated passively immune pigs, showed only elevated temperatures and most of them excreted small amounts of ADV.The development of cellular immunity after infection was rather similar within the maternally immune group independent whether the animals had been vaccinated or not, but ADV-ADCC and ADV-LYST showed a more rapid progress within the vaccinated group than in the non-vaccinated group and the non-immune control group. Infection resulted in significantly higher ND₅₀ titres in vaccinated and revaccinated animals than in unvaccinated animals, indicating a secondary response in those pigs. Thus, ADV sensitization of lymphocytes had been evoked by vaccination despite the presence of maternal antibody.The interpretation of the results was complicated by great individual and litter-dependent variations of the immune parameters.Abbreviations ADV Aujeszky's disease virus - ADV-ADCC antibody-dependent cell-mediated cytotoxicity against ADV infected cells - ADV-LYST lymphocyte stimulation by ADV - ADV-SCC spontaneous cell-mediated cytotoxicity against ADV infected cells - CTI cytotoxic index(ices) - DPI day post infection - LYST lymphocyte stimulation - SCC spontaneous cell-mediated cytotoxicity - SI stimulation index(ices) - WPP week post partum - WPV week post vaccination - WPRV week post revaccination With 5 Figures     

Cellular Changes in Lungs of Mice Infected with Influenza Virus: Characterization of the Cytotoxic Responses

Transpleural lavage of lungs from uninfected C3H mice yielded an average of 300,000 leukocytes per mouse. This number increased eightfold within 6 days after intranasal inoculation with virulent influenza A/Hong Kong/68 (H3N2) virus. Macrophages and lymphocytes in approximately equal numbers comprised 90% or more of the leukocytes both before and during infection. B, T, and null lymphocytes comprised, respectively, 9, 21, and 18% of the leukocytes before infection and 7, 26, and 5% by day 6. In absolute numbers, macrophages and T lymphocytes provided the major increments during infection. Cytotoxic activity of mononuclear cells from lung lavages was compared in a chromium release assay using syngeneic L929 target cells with the activity of mediastinal lymph nodes, spleens, and peripheral blood of uninfected and infected C3H mice. Nonspecific cytotoxicity for target cells infected with H3hkNeq1 or B/Lee influenza virus was found with mononuclear cells from uninfected mice. This activity tended to be highest with lavage leukocytes and was associated with adherent cells, presumably macrophages. Increased virus-specific cytotoxicity was detected with lavage cells by day 6 and persisted through day 9, the period of maximal pneumonia. Similar cytotoxic activity also appeared in cells from the nodes and spleen at this same time but was not detected in peripheral blood cells. The virus-specific cytotoxicity of lavage cells was due largely to a nonadherent cell possessing Fc receptors and theta antigen but lacking C3 receptors; these properties are compatible with actively cytotoxic T lymphocytes. The cytological characteristics of the infiltrating leukocytes and the cytotoxicity data suggest that the local T cell response to influenza virus infection in the lung is a major contributor to the pneumonia observed in this mouse model.     

Herpes simplex virus-1-specific human cytotoxic T lymphocytes are induced in vitro by autologous virus-infected mononuclear cells.

A new technique for in vitro activation of cytotoxic T lymphocytes (CTLs) specific for herpes simplex virus type 1 (HSV-1) is described. Autologous phytohemagglutinin (PHA)-activated, HSV-1-infected peripheral blood mononuclear cells (PBMC) were used, after fixation with 1% paraformaldehyde, to activate virus-specific CTLs in short-term cultures. The same unfixed PBMC were used as target cells in the cytotoxicity assay. By using this technique high levels of HSV-1-specific cytotoxic activity (50.06 +/- 16.76% at 30:1 effector:target ratio) were repeatedly obtained in 24 experiments using PBMC from 16 HSV-1 antibody-positive healthy donors, while no cytotoxic activity was observed using PBMC from 3 HSV-1 antibody-negative donors. HSV-1-induced CTLs were shown to be virus-specific as they did not lyse autologous, PHA-activated PBMC infected with influenza A virus or autologous Epstein-Barr virus (EBV) lymphoblastoid cell line (LCL), while they were able to lyse both HSV-1-infected, autologous PHA-activated PBMC and EBV-LCL. HSV-1-specific cytotoxicity was mediated by T lymphocytes, since depletion of CD3-positive cells from the effector population completely removed the killing of HSV-1-infected target cells. CD8-positive CTLs were primarily involved in the killing of HSV-1-infected targets since depletion of CD8-positive cells caused a strong reduction of virus-specific cytotoxic activity while elimination of CD4-positive lymphocytes increased killing capacity. Finally, this technique has proven to be highly reproducible, easy to perform, and thus suitable for clinical investigations.     

Generation of virus-specific cytolytic activity in human peripheral lymphocytes after vaccination with vaccinia virus and measles virus

Human peripheral blood lymphocytes (PBL) harvested after vaccination with vaccinia or measles virus showed a specific activity against virusinfected target cells. This activity peaked on day 7 and was specific for the target cells infected with the virus used for the vaccination. The cytotoxic activity was not related to HLA markers. The cells involved in the cytolytic process were lymphocytes bearing Fc receptors. In addition, the cytotoxic activity was abrogated by more than 90% by rabbit Fab'2 anti-human IgG. It is therefore likely that two subpopulations of lymphocytes are involved: an antibody-secreting cell providing specific antiviral antibody and an effector cell bearing Fc receptor (K cells). Finally, these experiments suggest that antibody-dependent cell cytotoxicity may play a major role in the recovery from virus infection in man.     

Specificity in the immunosuppression induced by avian reticuloendotheliosis virus.

Several parameters of the cellular and humoral immune responses of chickens infected with reticuloendotheliosis virus (REV-T), an avian defective acute leukemia virus, or with its helper virus, reticuloendotheliosis-associated virus (REV-A), were evaluated. Spleen cells from chickens infected with REV-T (REV-A) or REV-A exhibited depressed mixed lymphocyte and mitogen responses in vitro. Allograft rejection was delayed by 6 to 14 days in birds infected with REV-A. The specific antitumor cell immune response was also studied by a 51Cr-release cytotoxicity assay. Lymphocytes from chickens infected with low numbers of the REV-T-transformed cells exhibited significant levels of cytolytic reactivity against the 51Cr-labeled REV-T tumor cells in vitro. The mitogen response of lymphocytes from these injected birds was similar to that of uninjected chickens. In contrast, lymphocytes from chickens injected with higher numbers of REV-T-transformed cells exhibited suppressed mitogen reactivity and failed to develop detectable levels of cytotoxic activity directed against the REV-T tumor cells. These results suggest that the general depression of cellular immune competence which occurs during REV-T (REV-A) infection could contribute to the development of this acute leukemia by inhibiting the proliferation of cytotoxic cells directed against the tumor cell antigens. The cytotoxic effect observed after the injection of chickens with non-immunosuppressive levels of REV-T-transformed cells appears to be specific for the REV-T tumor cell antigens since cells transformed by Marek's disease virus or avian erythroblastosis virus were not lysed. In marked contrast, birds whose cellular immune responses were suppressed by infection with REV-A were capable of producing a humoral immune response to viral antigens. Detectable levels of viral antibody, however, did not appear until 12 to 15 days after REV-A infection. Since REV-T (REV-A) induced an acute leukemia resulting in death within 7 to 14 days, it appears unlikely that the ability of chickens to make antiviral antibody influences the development of lethal reticuloendotheliosis.     

Lymphocyte blastogenic responses to influenza virus antigens after influenza infection and vaccination in humans.

Virus-specific in vitro cell-mediated immune responses were investigated in 20 normal volunteers who were challenged with liver influenza A/VIC/3/75 (H3N2) virus and in 13 volunteers who were vaccinated with inactivated vaccine containing A/VIC and A/NJ/8/76 (HswN1) antigens. Lymphocyte cultures were established from peripheral blood samples obtained prior to and at various times after infection or vaccination. Blastogenesis was determined by [3H]thymidine incorporation after stimulation of cultures with purified, inactivated, whole influenza viruses. Six days after infection, significantly elevated levels of blastogenesis were observed after in vitro stimulation with A viruses of hemagglutinin and neuraminidase subtypes that were the same as (H3N2) or antigenically distinct from (Heq1Neq1 or HswN1) those of the challenge virus, although maximum stimulation was noted with virus of the same hemagglutinin subtype (H3) as the challenge virus. Similar although more prolonged blastogenic responses were noted in lymphocyte cultures from vaccinees who had serum antibody rises after vaccination. The kinetics of these responses suggest that cell-mediated immunity may play a role in early events after infection and vaccination with influenza virus.     

Elicitation of broadly neutralizing influenza antibodies in animals with previous influenza exposure

The immune system responds to influenza infection by producing neutralizing antibodies to the viral surface protein, hemagglutinin (HA), which regularly changes its antigenic structure. Antibodies that target the highly conserved stem region of HA neutralize diverse influenza viruses and can be elicited through vaccination in animals and humans. Efforts to develop universal influenza vaccines have focused on strategies to elicit such antibodies; however, the concern has been raised that previous influenza immunity may abrogate the induction of such broadly protective antibodies. We show here that prime-boost immunization can induce broadly neutralizing antibody responses in influenza-immune mice and ferrets that were previously infected or vaccinated. HA stem-directed antibodies were elicited in mice primed with a DNA vaccine and boosted with inactivated vaccine from H1N1 A/New Caledonia/20/1999 (1999 NC) HA regardless of preexposure. Similarly, gene-based vaccination with replication-defective adenovirus 28 (rAd28) and 5 (rAd5) vectors encoding 1999 NC HA elicited stem-directed neutralizing antibodies and conferred protection against unmatched 1934 and 2007 H1N1 virus challenge in influenza-immune ferrets. Indeed, previous exposure to certain strains could enhance immunogenicity: The strongest HA stem-directed immune response was observed in ferrets previously infected with a divergent 1934 H1N1 virus. These findings suggest that broadly neutralizing antibodies against the conserved stem region of HA can be elicited through vaccination despite previous influenza exposure, which supports the feasibility of developing stem-directed universal influenza vaccines for humans.     

Cytotoxic T lymphocyte recognition sites on influenza virus hemagglutinin

When influenza virus infection occurs, part of the cytotoxic T lymphocyte responses induced are directed to the major surface molecule of the virus, the hemagglutinin. However, despite their potential use as a peptide vaccine, little information is available concerning the submolecular areas in the hemagglutinin that are responsible for its immunologic recognition by cytotoxic T lymphocytes. The primary goal of this study is to determine whether submolecular areas recognized by antibodies and helper T cells are also important in the virus-specific, T lymphocyte-mediated cytotoxic responses generated towards virus-infected cells. A panel of synthetic peptides representing areas of the hemagglutinin, homologous to those in influenza AX-31 virus which have previously been shown to bind anti-influenza virus antibodies and provoke proliferation of virus-primed T-helper lymphocytes, was tested in two different cytotoxicity assays. In the experiments presented here, it was found that when selected peptides were incubated with appropriate L929 target cells, lysis by virus-specific cytotoxic T cells was observed. In addition, AX-31-primed lymphocytes preincubated with these synthetic peptides (both individually and as an equimolar mixture) exhibited enhanced lysis of virus-infected syngeneic targets. The cytotoxic responses showed dose-response characteristics in all cases, and in each of the two assays used the same patterns of cytotoxic induction were observed. The recognition of peptides was MHC-restricted since virus-specific cytotoxic T cells from C3H/He mice (H-2k) lysed L929 (H-2k) target cells after incubation with peptides or viruses, but did not lyse P815 (H-2d) targets under the same conditions.     

穿孔素介导的细胞凋亡机制在抗流感病毒感染免疫防御中作用的研究

目的：穿孔素介导的细胞凋亡机制在流感病毒初次感染中作用的研究。方法：用流感病毒A／PR／8／34经鼻感染穿孔素基因敲除鼠和同源对照C57BL／6小鼠，采用PFU方法测定肺内流感病毒增殖状况；免疫组织化学染色方法观察小鼠病毒感染后感染细胞的凋亡情况；利用乳酸脱氢酶释放法检测感染鼠脾淋巴细胞NK活性及CTL杀伤活性。结果：穿孔素基因缺乏导致流感病毒在小鼠肺内大量增殖；小鼠清除感染病毒所需时间延长；病毒感染细胞发生凋亡的时间亦因穿孔素的缺乏而延迟；感染小鼠脾淋巴细胞NK活性及CTL杀伤活性均显著降低。结论：穿孔素依赖的细胞介导的细胞毒效应在控制流感病毒初次感染，快速清除感染病毒方面起重要作用。     

Natural cytotoxic cell activity linked to time of recurrence of herpes labialis

Peripheral blood mononuclear leucocytes from patients with recurrent oral herpes labialis showed an enhanced spontaneous cytotoxic activity against HSV-1 infected target cells during the acute episode. A heightened cytotoxicity persisted for several weeks during prospective follow-up study of the donors, but fell to low levels during the last week before the next episode of herpes labialis. A correlation between natural cytotoxicity against HSV infected targets and pre-recurrence intervals was noted (r = 0.715, P less than 0.05). In parallel, recurrence of herpes labialis was accompanied by a marked increase in the percentage of T cells with Fc IgG receptors and in the percentage of natural cytotoxic lymphocytes, as defined by a newly described monoclonal antibody, HNC-1A3. Both these populations were significantly decreased during the last week before the next herpes labialis episode, suggesting a role for these cells in defence mechanisms involved in anti-HSV immunity.     

Increased influenza pneumonia mortality of mice adoptively immunized with node and spleen cells sensitized by inactivated but not live virus.

Syngeneic mice adoptively immunized intravenously with 25 million washed node and spleen cells from donors vaccinated subcutaneously with formolized influenza A PR8 had a higher mortality with influenza pneumonia after challenge with homologous virus than occurred in recipients of similar cells from unsensitized donors, and this increased mortality was prevented by treatment of the sensitized cells with antithymocyte serum. Mice adoptively immunized with cells from donors vaccinated with formolized influenza A PR8 also had a higher mortality than recipients of unsensitized cells after challenge with heterologous influenza B Lee. Mice who received PR8-sensitized cells and survived challenge with influenza B Lee developed antibody only to the challenge virus, and serum antibody titers to the challenge virus in surviving recipients of sensitized cells were similar to those of recipients of unsensitized cells in all studies. Influenza mortality of recipients of antibody-containing mouse serum after homologous virus challenge was similar to that of recipients of antibody-free mouse serum in this model. Washed node and spleen cells from donor mice who had survived respiratory infection or received subcutaneous vaccination with live influenza A PR8 and those from donor mice given typhoid vaccine subcutaneously all failed to alter mortality from that observed in recipients of unsensitized cells after challenge with influenza A PR8. These results suggest that subcutaneous vaccination with inactivated influenza establishes a reactivity of the cell-mediated immunologic system which can increase the severity of influenza infection of the respiratory tract under certain conditions, and that sensitization by live influenza fails to produce this effect.     

Anti-influenza human T killer cells present an intertypic activity anti-A and -B type viruses in a secondary reaction in vitro.

In man influenza viruses induce a cytolytic T lymphocyte (CTL) activity directed against autologous or HLA-A or -B compatible target cells infected with the immunizing virus. While only type specific CTL are characterized in man, we report here experiments showing intertypic activities of human CTL from donors vaccinated with both A and B type influenza viruses. Their peripheral blood leucocytes (PBL) restimulated in vitro with live influenza virus of one type gave rise to both anti-A and -B activities, when non-infected or Sendaï infected target cells were not lysed. These intertypic activities were restricted by HLA-A or -B antigens and were inhibited by OKT3 antibody. When u.v.-inactivated viruses were used as restimulating antigen, no intertypic CTL were obtained. The results of competition experiments with cold targets show that no common antigens were recognized by anti-A and anti-B CTL. Moreover the restricting HLA-A or -B molecules seen in association with A or B types viruses appeared different in the same experiment, confirming that different antigens were probably involved for the agents of A and B subgroups. This influenza specific intertypic activity was therefore probably due to an intertypic stimulation of type specific CTL activities, possibly arising at the level of T helper cells.     

Cross-protection and cross-reactive cytotoxic T cells induced by influenza virus vaccines in mice

Subunit and intact influenza A virus vaccines have been compared with infectious virus in a mouse model for their ability to induce memory for cross-reactive cytotoxic T cell responses and to protect mice from challenge with different subtypes of influenza A virus. There is an overall correlation between secondary cytotoxic T cell responses and cross-protection. The most long-lasting and successful cross-protection was observed after intranasal infection with influenza virus A/X31 (H3N2) that replicates efficiently in mice and induces high levels of memory for cross-reactive cytotoxic T cell responses. Short-lasting cross-protection and low levels of T cell-mediated cytotoxicity were associated with infection by A/USSR (H 1N1) virus, that replicates to lower titers in mice, or after multiple injections of inactivated whole virus vaccine. No cross-protection to challenge with heterologous influenza virus was detectable after 1-2 injections of HANA influenza subunit vaccine which failed to prime hosts for cytotoxic T cell responses. These findings may have important implications for vaccination strategy. If cytotoxic T cells play a role in the protection of humans from influenza, live attenuated vaccines should be considered instead of the currently recommended inactivated virus or subunit vaccines.     

Cytolysis of Junin infected target cells by immune guinea pig spleen cells

Spleen cells from guinea pigs infected with an attenuated strain of Junin virus (the causative agent of Argentine hemorrhagic fever) specifically lysed virus-infected syngeneic target cells in vitro. This activity was detected as early as 6 days after infection, reached a maximum on days 10-13, and persisted at lower levels, at least through day 30. Monoclonal antibody to guinea pig T cells had no effect on the activity. After B or T cell enrichment techniques, the cytolysis was found with the B cell fraction. Aggregated IgG blocked the cytolysis. These characteristics suggested lytic activity was mediated at least in part by an antibody-dependent cell-mediated cytotoxicity (ADCC) mechanism. Although some cytolysis could be detected by using exogenously added antiserum and normal spleen effector cells, such reconstruction showed less efficient killing than when spleen cells from Junin-infected guinea pigs were used. This apparent discrepancy was resolved when spleen cells from these infected animals exhibited enhanced activity in non-viral ADCC systems as well. The cytotoxic activity by spleen cells against Junin-infected targets was detected only with non-fatal Junin infections. Cytolysis could not be measured in spleen cell suspensions from guinea pigs lethally infected with Junin virus; i.e. adults infected with a virulent strain of Junin and baby guinea pigs or immunosuppressed adult animals infected with an attenuated strain. However, spleen cells from both the immunosuppressed, infected adults and the adult guinea pigs infected with a virulent strain of Junin were able to mediate cytotoxicity in a nonviral system (antibody-sensitized Vero cells). The development of spleen cell cytotoxicity by Junin-infected guinea pigs against Junin-infected target cells correlated with whether the infection was resolved or was lethal.