Single immunization with MF59-adjuvanted inactivated whole-virion H7N9 influenza vaccine provides early protection against H7N9 virus challenge in mice

H7N9 influenza infection in humans would result in severe respiratory illness. Vaccination is the best way to prevent influenza virus. In this paper, we investigated the effect of early protection provided by inactivated whole-virion H7N9 influenza vaccine in a mouse model.Mice were immunized intramuscularly once with different doses of inactivated whole-virion H7N9 influenza vaccine alone or in combination with MF59 adjuvant. Specific IgM and IgG antibody titers in sera of mice were detected by ELISA 3, 5 and 7days after immunization. To evaluate the early protection provided by the vaccine, mice were challenged with lethal dose (40LD₅₀) of homologous virus 3, 5 and 7 days after immunization respectively. The survival rate and body weight change of mice during 21 days after challenge and the residual lung virus titer on 3rd day after challenge were determined. The results demonstrated that mice could obtain effective protection 3 days after immunization with the vaccine at a high dose, and 5–7 days after immunization even at a low dose. Thus early immune responses induced by inactivated whole-virion H7N9 vaccine could provide effective protection.     

Immunologic response to the influenza virus neuraminidase is influenced by prior experience with the associated viral hemagglutinin. I. Studies in human vaccinees

Analysis of an earlier study of H3N2 and H7N2 inactivated influenza vaccines in schoolchildren demonstrated a greater viral neuraminidase (NA) immunogenicity of the vaccine containing the H7 hemagglutinin (HA) antigen to which they had not been primed, despite the lesser NA antigen content of that vaccine. Thus, prior experience with the influenza viral HA appeared to have a negative influence on immune response to NA, the associated external glycoprotein, presumably on the basis of intermolecular antigenic competition. In a second study, sequential immunologic response to influenza viral NA was compared in college students who were immunized with either conventional commercial vaccine or an antigenic reassortant H7N1 vaccine, and who subsequently experienced natural infection with an H1N1 influenza virus. Although both vaccines were only marginally immunogenic in inducing NA antibody response in seronegative subjects, in vaccinees initially seropositive for HA antibody significant NA antibody titer increases occurred with H7N1 vaccine. Subsequent natural infection boosted NA antibody less effectively in the population previously primed by natural infection than in initially seronegative subjects primed by H7N1 vaccination. It is suggested that primary immunization monospecific for influenza viral NA may alter the subsequent pattern of immune response to one more favorable to the induction of NA antibody when virus is encountered.     

甲型H1N1流感病毒佐剂疫苗小鼠免疫效果

为了探讨甲型H1N1流感病毒氢氧化铝佐剂疫苗对小鼠的免疫作用及对小鼠繁殖性能的影响,以不同剂量、不同免疫程序免疫小鼠后定期采血;用血凝抑制(HI)方法检测血清H1N1流感病毒HI抗体滴度,观察H1N1流感病毒佐剂疫苗对小鼠受孕、产仔、哺乳的影响;比较孕鼠及非孕鼠的抗体滴度,免疫后孕鼠所产仔鼠的体重及H1N1胎传抗体水平。结果显示,以0.5μg组开始的不同剂量、不同免疫程序均可使小鼠产生90倍以上水平的H1N1流感病毒抗体;免疫后的小鼠不影响受孕、产仔及哺乳;仔鼠保护性抗体可持续1个月以上。H1N1流感病毒佐剂疫苗是一种高免疫原性的制剂,用低剂量免疫,即可产生90倍以上持续时间较长的保护性抗体。这种佐剂疫苗对小鼠的繁殖性能无明显影响,免疫产生的抗体经胎盘可垂直传递给仔鼠。     

Evaluation of influenza vaccine Vaxigrip in the combined immunization of conscripts during influenza seasons of 2002-2003

The immunization properties of the influenza vaccine Vaxigrip, used in combination with vaccines against pneunococcal infection and hepatitis A (respectively, Pneumo 23 and Avaxim), were evaluated. In Central Russia in one of the units of the internal forces of the RF Ministry of Internal Affairs 3 groups totaling 755 servicemen were formed, depending on the complex of the introduced vaccines. Active medical observation and the registration of the complaints of the vaccinees at the postvaccinal period did not reveal unusual reactions and complications in none of the groups under observation. In the evaluation of the level of specific antibodies to the circulating influenza viruses prior to vaccination the low level of collective protection to influenza B virus was determined: protective antibody levels were registered only in 14-18% of the servicemen, while the corresponding data with respect of influenza viruses A(H1N1) and A(H3N2) were 45-50% and 56-63% respectively. At the same time, in seronegative persons the vaccine Vaxigrip exhibited high immunogenic activity with respect of all 3 influenza strains; seroconversion to them was determined in 84-92% of the vaccines, and the level of protective antibody titers before the beginning of the epidemic season was 86-99% in the whole of the group. The characteristics of the prophylactic effectiveness of the vaccine Vaxigrip in relation to the influenza virus infection level 1 were 4.7 (index) and 79% (coefficient). In addition, the frequency of influenza cases, clinically pronounced and confirmed by laboratory methods, in patients who had been immunized with 3 vaccines was 6.7%, which was 10.3 times less frequent than number of cases in the groups of comparison (68.2% on the average). The coefficient of epidemiological effectiveness of the prophylaxis of influenza was 90.2%. The complex use of 3 preparations did not affect the immunization properties of the vaccine Vaxigrip.     

Regulation of antinucleoprotein IgG by systemic vaccination and its effect on influenza virus clearance

Seasonal influenza epidemics recur due to antigenic drift of envelope glycoprotein antigens and immune evasion of circulating viruses. Additionally, antigenic shift can lead to influenza pandemics. Thus, a universal vaccine that protects against multiple influenza virus strains could alleviate the continuing impact of this virus on human health. In mice, accelerated clearance of a new viral strain (cross-protection) can be elicited by prior infection (heterosubtypic immunity) or by immunization with the highly conserved internal nucleoprotein (NP). Both heterosubtypic immunity and NP-immune protection require antibody production. Here, we show that systemic immunization with NP readily accelerated clearance of a 2009 pandemic H1N1 influenza virus isolate in an antibody-dependent manner. However, human immunization with trivalent inactivated influenza virus vaccine (TIV) only rarely and modestly boosted existing levels of anti-NP IgG. Similar results were observed in mice, although the reaction could be enhanced with adjuvants, by adjusting the stoichiometry among NP and other vaccine components, and by increasing the interval between TIV prime and boost. Importantly, mouse heterosubtypic immunity that had waned over several months could be enhanced by injecting purified anti-NP IgG or by boosting with NP protein, correlating with a long-lived increase in anti-NP antibody titers. Thus, current immunization strategies poorly induce NP-immune antibody that is nonetheless capable of contributing to long-lived cross-protection. The high conservation of NP antigen and the known longevity of antibody responses suggest that the antiviral activity of anti-NP IgG may provide a critically needed component of a universal influenza vaccine.     

用电穿孔方法研究 H5N1 禽流感病毒DNA 疫苗对动物的免疫保护作用

为了研究 H5N1 DNA 疫苗对小鼠和鸡的保护效率,用 H5N1 禽流感病毒 HA DNA 疫苗免疫 BALB/c 小鼠和 SPF 鸡 . 小鼠和鸡分别经电穿孔和肌肉注射免疫两次,间隔为 3 周 . 二次免疫后,用致死量的同源病毒进行攻毒实验 . 空白对照组在攻毒后全部死亡,而经电穿孔免疫的小鼠和鸡均获得了完全的保护,并能有效地抑制病毒在小鼠肺脏和鸡泄殖腔的繁殖 . 同时,电穿孔免疫的小鼠和鸡均产生了高水平的特异性抗体 . 经电穿孔免疫的小鼠攻毒后 CTL 反应明显加强 . 这些结果表明, HA DNA 疫苗能有效地保护小鼠和鸡对禽流感病毒的感染,同时也表明电穿孔免疫是 DNA 疫苗免疫的有效途径之一 .     

Protection of inactivated influenza virus vaccine against lethal influenza virus infection in diabetic mice

Influenza virus infection frequently causes complications and some excess mortality in the patients with diabetes. Vaccination is an effective measure to prevent influenza virus infection. In this paper, antibody response and protection against influenza virus infection induced by vaccination were studied in mouse model of diabetes. Healthy and diabetic BALB/c mice were immunized once or twice with inactivated influenza virus vaccine at various dosages. Four weeks after the first immunization or 1 week after the second immunization, the mice were challenged with influenza virus at a lethal dose. The result showed that the antibody responses in diabetic mice were inhibited. Immunization once with high dose or twice with low dose of vaccine provided full protection against lethal influenza virus challenge in diabetic mice, however, in healthy mice, immunization only once with low dose provided a full protection.     

Heterosubtypic antibody response elicited with seasonal influenza vaccine correlates partial protection against highly pathogenic H5N1 virus

Background

The spread of highly pathogenic avian influenza (HPAI) H5N1 virus in human remains a global health concern. Heterosubtypic antibody response between seasonal influenza vaccine and potential pandemic influenza virus has important implications for public health. Previous studies by Corti et al. and by Gioia et al. demonstrate that heterosubtypic neutralizing antibodies against the highly pathogenic H5N1 virus can be elicited with a seasonal influenza vaccine in humans. However, whether such response offers immune protection against highly pathogenic H5N1 virus remained to be determined.

Methodology/Principal Findings

In this study, using a sensitive influenza HA (hemagglutinin) and NA (neuraminidase) pseudotype-based neutralization (PN) assay we first confirmed that low levels of heterosubtypic neutralizing antibody response against H5N1 virus were indeed elicited with seasonal influenza vaccine in humans. We then immunized mice with the seasonal influenza vaccine and challenged them with lethal doses of highly pathogenic H5N1 virus. As controls, we immunized mice with homosubtypic H5N1 virus like particles (VLP) or PBS and challenged them with the same H5N1 virus. Here we show that low levels of heterosubtypic neutralizing antibody response were elicited with seasonal influenza vaccine in mice, which were significantly higher than those in PBS control. Among them 2 out of 27 whose immune sera exhibited similar levels of neutralizing antibody response as VLP controls actually survived from highly pathogenic H5N1 virus challenge.

Conclusions/Significance

Therefore, we conclude that low levels of heterosubtypic neutralizing antibody response are indeed elicited with seasonal influenza vaccine in humans and mice and at certain levels such response offers immune protection against severity of H5N1 virus infection.     

人参多糖对新甲型H1N1流感病毒灭活疫苗的免疫增强作用

在流感灭活疫苗中添加佐剂可以提高疫苗的免疫原性,节约抗原用量。一些天然中草药多糖具有潜在的佐剂效应。本文探讨了人参多糖（ginseng polysaccharide,GPS）在新甲型H1N1流感病毒裂解型灭活疫苗中的佐剂效应。将不同剂量GPS与新甲型H1N1流感病毒灭活疫苗混合,共同免疫小鼠一次,通过检测免疫后在小鼠体内诱导产生的疫苗特异性IgM、IgG、IgG1和IgG2a抗体情况来评价GPS作为流感病毒灭活疫苗佐剂的免疫增强效果,并与不添加佐剂的疫苗和加有铝佐剂的疫苗的免疫效果作比较。结果显示,GPS与铝佐剂一样能显著提高和维持疫苗特异性IgG抗体滴度,同时提高IgM抗体水平,其中800μgGPS的佐剂效果最好。因此我们认为GPS可以作为流感病毒灭活疫苗的一种候选佐剂。     

Virus-like particle vaccine induces protective immunity against homologous and heterologous strains of influenza virus

Recurrent outbreaks of highly pathogenic avian influenza virus pose the threat of pandemic spread of lethal disease and make it a priority to develop safe and effective vaccines. Influenza virus-like particles (VLPs) have been suggested to be a promising vaccine approach. However, VLP-induced immune responses, and their roles in inducing memory immune responses and cross-protective immunity have not been investigated. In this study, we developed VLPs containing influenza virus A/PR8/34 (H1N1) hemagglutinin (HA) and matrix (M1) proteins and investigated their immunogenicity, long-term cross-protective efficacy, and effects on lung proinflammatory cytokines in mice. Intranasal immunization with VLPs containing HA induced high serum and mucosal antibody titers and neutralizing activity against PR8 and A/WSN/33 (H1N1) viruses. Mice immunized with VLPs containing HA showed little or no proinflammatory lung cytokines and were protected from a lethal challenge with mouse-adapted PR8 or WSN viruses even 5 months postimmunization. Influenza VLPs induced mucosal immunoglobulin G and cellular immune responses, which were reactivated rapidly upon virus challenge. Long-lived antibody-secreting cells were detected in the bone marrow of immunized mice. Immune sera administered intranasally were able to confer 100% protection from a lethal challenge with PR8 or WSN, which provides further evidence that anti-HA antibodies are primarily responsible for preventing infection. Taken together, these results indicate that nonreplicating influenza VLPs represent a promising strategy for the development of a safe and effective vaccine to control the spread of lethal influenza viruses.     

Microneedle Vaccination Elicits Superior Protection and Antibody Response over Intranasal Vaccination against Swine-Origin Influenza A (H1N1) in Mice

Influenza is one of the critical infectious diseases globally and vaccination has been considered as the best way to prevent. In this study, immunogenicity and protection efficacy between intranasal (IN) and microneedle (MN) vaccination was compared using inactivated swine-origin influenza A/H1N1 virus vaccine. Mice were vaccinated by MN or IN administration with 1 μg of inactivated H1N1 virus vaccine. Antigen-specific antibody responses and hemagglutination-inhibition (HI) titers were measured in all immunized sera after immunization. Five weeks after an immunization, a lethal challenge was performed to evaluate the protective efficacy. Furthermore, mice were vaccinated by IN administration with higher dosages (> 1 μg), analyzed in the same manner, and compared with 1 μg-vaccine-coated MN. Significantly higher antigen-specific antibody responses and HI titer were measured in sera in MN group than those in IN group. While 100% protection, slight weight loss, and reduced viral replication were observed in MN group, 0% survival rate were observed in IN group. As vaccine dose for IN vaccination increased, MN-immunized sera showed much higher antigen-specific antibody responses and HI titer than other IN groups. In addition, protective immunity of 1 μg-MN group was similar to those of 20- and 40 μg-IN groups. We conclude that MN vaccination showed more potential immune response and protection than IN vaccination at the same vaccine dosage.     

Characterization of cross protection of Swine-Origin Influenza Virus (S-OIV) H1N1 and reassortant H5N1 influenza vaccine in BALB/c mice given a single-dose vaccination

Background

Influenza virus has antigen drift and antigen shift effect, vaccination with some influenza vaccine might not induce sufficient immunity for host to the threat of other influenza virus strains. S-OIV H1N1 and H5N1 influenza vaccines in single-dose immunization were evaluated in mice for cross protection to the challenge of A/California/7/2009 H1N1 or NIBRG-14 H5N1 virus.

Results

Both H1N1 and H5N1 induced significant homologous IgG, HAI, and microneutralization antibody responses in the mice, while only vaccines plus adjuvant produced significant heterogeneous IgG and HAI antibody responses. Both alum and MPLA adjuvants significantly reduced the S-OIV H1N1 vaccine dose required to elicit protective HAI antibody titers from 0.05 μg to 0.001 μg. Vaccines alone did not protect mice from challenge with heterogeneous influenza virus, while H5N1 vaccine plus alum and MPLA adjuvants did. Mouse body weight loss was also less significant in the presence of adjuvant than in the vaccine without adjuvant. Furthermore, both H1N1 and H5N1 lung viral titers of immunized mice were significantly reduced post challenge with homologous viruses.

Conclusion

Only in the presence of MPLA adjuvant could the H5N1 vaccine significantly reduce mouse lung viral titers post H1N1 virus challenge, and not vice versa. MPLA adjuvant induced cross protection with a single dose vaccination to the challenge of heterogeneous influenza virus in mice. Lung viral titer seemed to be a better indicator compared to IgG, neutralization antibody, and HAI titer to predict survival of mice infected with influenza virus.     

枸杞多糖对H5N1流感全病毒灭活疫苗的体液免疫增强作用

探讨枸杞多糖(Lycium barbarum polysaccharide,LBP)作为佐剂对H5亚型流感病毒全病毒灭活疫苗的体液免疫增强效果。将流感病毒A/Vietnam/1194/2004(H5N1)灭活疫苗与不同剂量的枸杞多糖混合后以腹腔注射的方式共同免疫小鼠,免疫后三周收集血清用于特异性抗体检测。实验中设立氢氧化铝佐剂组作对照共同评价LBP作为佐剂的免疫增强效果。结果显示,小鼠血清中针对H5灭活疫苗的特异性抗体水平在一定范围内随着LBP剂量的增加而提高。LBP在800μg剂量时血清特异性抗体水平较无佐剂组显著增强,并与氢氧化铝佐剂组大致相当。因而,LBP有可能成为一种有效的流感灭活疫苗免疫佐剂。     

Enhancement of the Immunogenicity and Protective Efficacy of a Mucosal Influenza Subunit Vaccine by the Saponin Adjuvant GPI-0100

Identification of safe and effective adjuvants remains an urgent need for the development of inactivated influenza vaccines for mucosal administration. Here, we used a murine challenge model to evaluate the adjuvant activity of GPI-0100, a saponin-derived adjuvant, on influenza subunit vaccine administered via the intranasal or the intrapulmonary route. Balb/c mice were immunized with 1 µg A/PR/8 (H1N1) subunit antigen alone or in combination with varying doses of GPI-0100. The addition of GPI-0100 was required for induction of mucosal and systemic antibody responses to intranasally administered influenza vaccine and significantly enhanced the immunogenicity of vaccine administered via the intrapulmonary route. Remarkably, GPI-0100-adjuvanted influenza vaccine given at a low dose of 2×1 µg either in the nares or directly into the lungs provided complete protection against homologous influenza virus infection.     

Assessment of the prophylactic effectiveness of an inactivated influenza vaccine by immunizing schoolchildren in the springtime

To evaluate the prophylactic effectiveness of influenza inactivated chromatographic vaccine, limited epidemiological observations were made on school children aged 11-14 years in Leningrad, in the autumn of 1981 and the spring of 1982. For immunization, made in a single administration, the vaccine composed of A (H3N2) + +A (H1N1) and containing 3.0-3.4 micrograms of hemagglutinin of each component per 0.2 ml of the preparation was used. Altogether 6928 schoolchildren were under observation; of these, 3686 children were immunized and 3242 children received placebo. The results of questioning and the analysis of morbidity rate among the schoolchildren, both immunized and receiving placebo, showed the safety and low reactogenicity of the vaccine irrespective of the time of the immunization campaign. The immunogenic potency of the preparation, as indicated by all observation results, proved to be higher in spring, than in autumn. The data thus obtained indicate that children immunized in spring were better protected and retained a higher level of protection within 12 months after immunization. The shift of the time of the immunization campaign from autumn to spring increased the immune layer in the groups of children by 16.5%. In 10 months after spring immunization the morbidity rate in influenza and acute respiratory diseases among the vaccinees was found to decrease 1.7 times.     

Sublingual immunization with a live attenuated influenza a virus lacking the nonstructural protein 1 induces broad protective immunity in mice

The nonstructural protein 1 (NS1) of influenza A virus (IAV) enables the virus to disarm the host cell type 1 IFN defense system. Mutation or deletion of the NS1 gene leads to attenuation of the virus and enhances host antiviral response making such live-attenuated influenza viruses attractive vaccine candidates. Sublingual (SL) immunization with live influenza virus has been found to be safe and effective for inducing protective immune responses in mucosal and systemic compartments. Here we demonstrate that SL immunization with NS1 deleted IAV (DeltaNS1 H1N1 or DeltaNS1 H5N1) induced protection against challenge with homologous as well as heterosubtypic influenza viruses. Protection was comparable with that induced by intranasal (IN) immunization and was associated with high levels of virus-specific antibodies (Abs). SL immunization with DeltaNS1 virus induced broad Ab responses in mucosal and systemic compartments and stimulated immune cells in mucosa-associated and systemic lymphoid organs. Thus, SL immunization with DeltaNS1 offers a novel potential vaccination strategy for the control of influenza outbreaks including pandemics.     

Intranasal Immunization of Baculovirus Displayed Hemagglutinin Confers Complete Protection against Mouse Adapted Highly Pathogenic H7N7 Reassortant Influenza Virus

Background

Avian influenza A H7N7 virus poses a pandemic threat to human health because of its ability for direct transmission from domestic poultry to humans and from human to human. The wide zoonotic potential of H7N7 combined with an antiviral immunity inhibition similar to pandemic 1918 H1N1 and 2009 H1N1 influenza viruses is disconcerting and increases the risk of a putative H7N7 pandemic in the future, underlining the urgent need for vaccine development against this virus.

Methodology/Principal Findings

In this study, we developed a recombinant vaccine by expressing the H7N7-HA protein on the surface of baculovirus (Bac-HA). The protective efficacy of the live Bac-HA vaccine construct was evaluated in a mouse model by challenging mice immunized intranasally (i.n.) or subcutaneously (s.c.) with high pathogenic mouse adapted H7N7 reassorted strain. Although s.c. injection of live Bac-HA induced higher specific IgG than i.n. immunization, the later resulted in an elevated neutralization titer. Interestingly, 100% protection from the lethal viral challenge was only observed for the mice immunized intranasally with live Bac-HA, whereas no protection was achieved in any other s.c. or i.n. immunized mice groups. In addition, we also observed higher mucosal IgA as well as increased IFN-γ and IL-4 responses in the splenocytes of the surviving mice coupled with a reduced viral titer and diminished histopathological signs in the lungs.

Conclusion

Our results indicated that protection from high pathogenic H7N7 (NL/219/03) virus requires both mucosal and systemic immune responses in mice. The balance between Th1 and Th2 cytokines is also required for the protection against the H7N7 pathogen. Intranasal administration of live Bac-HA induced all these immune responses and protected the mice from lethal viral challenge. Therefore, live Bac-HA is an effective vaccine candidate against H7N7 viral infections.     

H3N2 influenza infection elicits more cross-reactive and less clonally expanded anti-hemagglutinin antibodies than influenza vaccination

Background

During the recent H1N1 influenza pandemic, excess morbidity and mortality was seen in young but not older adults suggesting that prior infection with influenza strains may have protected older subjects. In contrast, a history of recent seasonal trivalent vaccine in younger adults was not associated with protection.

Methods and Findings

To study hemagglutinin (HA) antibody responses in influenza immunization and infection, we have studied the day 7 plasma cell repertoires of subjects immunized with seasonal trivalent inactivated influenza vaccine (TIV) and compared them to the plasma cell repertoires of subjects experimentally infected (EI) with influenza H3N2 A/Wisconsin/67/2005. The majority of circulating plasma cells after TIV produced influenza-specific antibodies, while most plasma cells after EI produced antibodies that did not react with influenza HA. While anti-HA antibodies from TIV subjects were primarily reactive with single or few HA strains, anti-HA antibodies from EI subjects were isolated that reacted with multiple HA strains. Plasma cell-derived anti-HA antibodies from TIV subjects showed more evidence of clonal expansion compared with antibodies from EI subjects. From an H3N2-infected subject, we isolated a 4-member clonal lineage of broadly cross-reactive antibodies that bound to multiple HA subtypes and neutralized both H1N1 and H3N2 viruses. This broad reactivity was not detected in post-infection plasma suggesting this broadly reactive clonal lineage was not immunodominant in this subject.

Conclusion

The presence of broadly reactive subdominant antibody responses in some EI subjects suggests that improved vaccine designs that make broadly reactive antibody responses immunodominant could protect against novel influenza strains.     

Intranasal immunization with influenza VLPs incorporating membrane-anchored flagellin induces strong heterosubtypic protection

We demonstrated previously that the incorporation of a membrane-anchored form of flagellin into influenza virus-like particles (VLPs) improved the immunogenicity of VLPs significantly, inducing partially protective heterosubtypic immunity by intramuscular immunization. Because the efficacy of mucosal vaccination is highly dependent on an adjuvant, and is particularly effective for preventing mucosal infections such as influenza, we determined whether the membrane-anchored flagellin is an efficient adjuvant for VLP vaccines by a mucosal immunization route. We compared the adjuvant effect of membrane-anchored and soluble flagellins for immunization with influenza A/PR8 (H1N1) VLPs by the intranasal route in a mouse model. The results demonstrate that membrane-anchored flagellin is an effective adjuvant for intranasal (IN) immunization, inducing enhanced systemic and mucosal antibody responses. High cellular responses were also observed as shown by cytokine production in splenocyte cultures when stimulated with viral antigens. All mice immunized with flagellin-containing VLPs survived challenge with a high lethal dose of homologous virus as well as a high dose heterosubtypic virus challenge (40 LD(50) of A/Philippines/82, H3N2). In contrast, no protection was observed with a standard HA/M1 VLP group upon heterosubtypic challenge. Soluble flagellin exhibited a moderate adjuvant effect when co-administered with VLPs by the mucosal route, as indicated by enhanced systemic and mucosal responses and partial heterosubtypic protection. The membrane-anchored form of flagellin incorporated together with antigen into influenza VLPs is effective as an adjuvant by the mucosal route and unlike standard VLPs, immunization with such chimeric VLPs elicits protective immunity to challenge with a distantly related influenza A virus.     

Induction of interferon in man by vaccines.

The purpose of this study was to extend the spectrum of vaccines with interferon-inducing potential in man. The vaccines selected for study were the commercially available attenuated poliomyelitis vaccine type 2 (Sabin strain) and the new live attenuated influenza A/England/42/72 (H3N2) vaccine ("Alice" strain). Five subjects, two of whom had low or undetectable polio type 2 neutralizing antibody levels were given the type 2 vaccine (10-4.7 TCID50) in the standard manner orally. Even though the two individuals with low titers experienced a fourfold or greater antibody rise and one of them shed the virus in his stool, neither they nor the remaining three volunteers developed detectable levels of interferon in their sera obtained at very closely spaced intervals from day 0 to day 25 following immunization. Fifteen subjects were given approximately 10-7.5 TCID50 of influenza A/England/42/72 (H3N2) by nasal drops. Specimens consisting of sera and nasal washings were obtained at closely timed intervals for 23 days, starting with day 3 following immunization. Interferon could be detected in three of nine (33.3%) subjects who had fourfold or greater HI antibody rises. No interferon was detected in nasal washings, however. It is concluded that poliomyelitis is not a good interferon inducers in man. Live attenuated influenza vaccine does induce an interferon response in subjects with low initial serum antibody titers. This response is at best modest. The latter finding also suggests that the attenuation of the Alice strain of influenza A vaccine is not dependent on its interferon inducing potential.