Majority Of Vaccinees Research Articles

Three-Year Durability of Immune Responses Induced by HIV-DNA and HIV-Modified Vaccinia Virus Ankara and Effect of a Late HIV-Modified Vaccinia Virus Ankara Boost in Tanzanian Volunteers.

We explored the duration of immune responses and the effect of a late third HIV-modified vaccinia virus Ankara (MVA) boost in HIV-DNA primed and HIV-MVA boosted Tanzanian volunteers. Twenty volunteers who had previously received three HIV-DNA and two HIV-MVA immunizations were given a third HIV-MVA immunization 3 years after the second HIV-MVA boost. At the time of the third HIV-MVA, 90% of the vaccinees had antibodies to HIV-1 subtype C gp140 (median titer 200) and 85% to subtype B gp160 (median titer 100). The majority of vaccinees had detectable antibody-dependent cellular cytotoxicity (ADCC)-mediating antibodies, 70% against CRF01_AE virus-infected cells (median titer 239) and 84% against CRF01_AE gp120-coated cells (median titer 499). A high proportion (74%) of vaccinees had IFN-γ ELISpot responses, 63% to Gag and 42% to Env, 3 years after the second HIV-MVA boost. After the third HIV-MVA, there was an increase in Env-binding antibodies and ADCC-mediating antibodies relative to the response seen at the time of the third HIV-MVA vaccination, p < .0001 and p < .05, respectively. The frequency of IFN-γ ELISpot responses increased to 95% against Gag or Env and 90% to both Gag and Env, p = .064 and p = .002, respectively. In conclusion, the HIV-DNA prime/HIV-MVA boost regimen elicited potent antibody and cellular immune responses with remarkable durability, and a third HIV-MVA immunization significantly boosted both antibody and cellular immune responses relative to the levels detected at the time of the third HIV-MVA, but not to higher levels than after the second HIV-MVA.

Safety and immunogenicity of modified vaccinia Ankara as a smallpox vaccine in people with atopic dermatitis

BackgroundFollowing vaccination with traditional smallpox vaccines or after exposure to vaccinated individuals, subjects with atopic dermatitis (AD) can develop eczema vaccinatum, a severe disease with disseminated eruption of pustular contagious lesions. Alternative smallpox vaccines with an improved safety profile would address this unmet medical need. MethodsAn open-label controlled Phase I clinical trial was conducted to investigate the safety and immunogenicity of modified vaccinia Ankara (MVA) in 15 healthy subjects compared to 45 subjects with either mild allergic rhinitis, a history of AD or presenting with mild active AD. MVA was given (Week 0 and 4) by a subcutaneous injection during a 28-week observation period. ResultsNo serious adverse event was reported and vaccinations with MVA did not lead to any clinically relevant skin reactions in AD subjects. Unsolicited administration site reactions did not show any trends compared to the healthy subject group. The majority of adverse reactions were mild to moderate, and all reactions were transient and resolved without intervention. The majority of vaccinees had seroconverted by ELISA (80–93%) and PRNT (69–79%) already two weeks after the first vaccination, increasing to 100% after the second immunization, with peak GMT above 1000 and 145 for ELISA and PRNT, respectively. ConclusionsMVA was equally well tolerated and immunogenic in all enrolled subjects with mild to moderate pain and redness at the injection site being the most frequent adverse reactions. There were no differences in the safety or immunogenicity profile of MVA in healthy subjects or those with AD or allergic rhinitis. The study has confirmed MVA as a promising smallpox vaccine candidate and demonstrated in a small study population that the vaccine has a similar safety and immunogenicity profile in healthy subjects and people with active AD.Clinical trials registration: NCT00189917.

Acceptability of Intanza® 15 μg intradermal influenza vaccine in Belgium during the 2010–2011 influenza season

Intradermal (ID) influenza vaccination induces an enhanced immune response in the elderly when compared with intramuscular (IM) vaccination. In 2009, an ID seasonal influenza vaccine (Intanza(®) [Sanofi Pasteur MSD, Lyon, France] 15 μg) was approved for use in individuals aged ≥ 60 years in Europe. This survey conducted in Belgium was the first in Europe to assess the acceptability of this vaccine in routine clinical practice by vaccinees and their general practitioners (GPs). GPs willing to use both the ID and IM influenza vaccines were selected during the 2010-2011 influenza season. Each GP recruited ≤ 10 patients aged ≥ 60 years who received the ID vaccine. Vaccinees and GPs completed questionnaires about their opinions on influenza vaccination and the acceptability of the ID influenza vaccine. In total, 105 GPs and 837 vaccinees completed questionnaires. A high proportion of vaccinees (40.3%) was aged ≥ 75 years, and 95.5% had been vaccinated the previous year. The majority of vaccinees was very satisfied (70.0%) or satisfied (27.9%) with the ID vaccine. The main reasons for the high satisfaction rate were that the injection was not very painful, administration was quick, and the vaccinee felt confident about the micro-needle injection system. Most vaccinees (91.1%) who had previously received IM influenza vaccination preferred the ID vaccine, and 98.5% of vaccinees reported they would consider receiving the ID vaccine the following year. The majority of GPs was very satisfied (78.6%) or satisfied (18.4%) with the ID vaccine, and most GPs (87.6%) expressed a preference for the ID vaccine over IM influenza vaccine. The ID influenza vaccine was well accepted by vaccinees and their GPs, who expressed a preference for the ID vaccine over conventional IM influenza vaccine. The availability of the ID influenza vaccine may help to improve uptake of seasonal influenza vaccination in the elderly.

A virosomal formulated Her-2/neu multi-peptide vaccine induces Her-2/neu-specific immune responses in patients with metastatic breast cancer: a phase I study

We have previously shown in mice that vaccination with three Her-2-peptides representing B-cell epitopes of the extracellular domain of Her-2/neu induces Her-2/neu-specific IgG antibodies with strong anti-tumor activity in vitro and in vivo. We have now finalized a phase I clinical trial with an anti-Her-2/neu vaccine-construct of immunopotentiating reconstituted influenza virosomes with the three peptides in patients with metastatic breast cancer (MBC). Ten MBC patients with low protein overexpression of Her-2/neu of MBC (+ or ++ upon immunohistochemistry, FISH negative) and positive hormone receptor status were enrolled in a single center phase I study. The virosomal formulated vaccine, consisting of 10 microg/peptide, was intramuscularly applied three times on days 1, 28, and 56. The primary endpoint of the study, which lasted 12 weeks, was safety, the secondary endpoint immunogenicity. Local erythema at the injection site was the only vaccine-related side effect occurring in four patients. In 8 of 10 patients an increase in peptide-specific antibody titer measured by ELISA was found. Importantly, the induced antibodies were also directed against the native Her-2/neu protein. Cellular immune responses, as measured by in vitro production of IL-2, IFN-c, and TNF-a of PBMCs showed a marked increase after vaccination in the majority of vaccinees. Notably, the number of CD4+CD25+Foxp3+T regulatory cells, which were significantly increased compared to healthy controls prior to vaccination, was markedly reduced following vaccination. In all, the immunological responses after vaccination indicated that the patients in stage IV of disease were immunocompetent and susceptible to vaccination. The Her-2/neu multipeptide vaccine was safe, well tolerated and effective in overcoming immunological tolerance to Her-2/neu. The induction of anti-Her-2-specific antibodies could result in clinical benefit comparable to passive anti-Her-2 antibody therapy.

Tetanus and Pertussis vaccines: their usefulness in the aging population

Immunization is a safe, effective and simple way of preventing life-threatening tetanus infection in children and adults, and is therefore recommended for all age groups in all European countries. In older persons, despite waning immunity with increasing age, the majority of vaccinees attain protective tetanus immunity under a proper vaccination schedule. Based on the scientific evidence, decennial boosters are recommended for elderly persons who have received primary tetanus vaccination in the past. Until recently, pertussis vaccination was understood as an early childhood intervention. Due to decreasing immunity, re-vaccination of youngsters and adults is recommended and is also considered for seniors 60 years and over. Routine immunization of seniors against pertussis every ten years yields a high level of protection of older individuals, and at the same time contributes to epidemiological control of pertussis in the population.

Can Specific Heterologous Immunity Boost Hepatitis B Vaccine Responses?

The currently licensed hepatitis B vaccines, consisting of recombinant hepatitis B surface antigen (HBsAg) and alum, are highly effective and induce protective antibody titers in 95% of vaccinees after 3 immunizations. Therefore, testing of titers of antibody to HBsAg (anti-HBs) is performed only in high-risk populations (such as health care workers) or poor vaccine responders (such as patients undergoing dialysis). Although a 5% nonresponse rate among healthy vaccinees would appear to be a small percentage, in absolute terms it leads to a substantial number of individuals who may not be protected while working in a high-risk environment. Moreover, nonresponse is associated with considerable uncertainty and anxiety. How can the immunogenicity of the vaccine be increased for vaccine nonresponders? Several strategies have been studied in this population: higher vaccine dose [1], different mode of application (e.g., intradermal) [2], additional vaccinations [3], inclusion of additional antigens (such as pre-S1 and pre-S2) [4], and the use of more potent adjuvants [5]. Currently, a higher vaccine dose is recommended for immunocompromised patients, such as dialysis patients. Intradermal injections are technically demanding and allow the application of lower doses of vaccine only; this route has not been consistently shown to be superior to intramuscular injection. New vaccines incorporating additional portions of the HBsAg (such as pre-S1 and pre-S2) have been developed, and increased immunogenicity has been clearly demonstrated [4, 6]. Although one of these vaccines apparently has not been further developed, a second is currently available in Israel and East Asia and is still in clinical development in the United States and Europe. The use of a more potent adjuvant, monophosphoryl lipid A, has led to a vaccine that induces protective antibody titers in the majority of vaccinees after only 2 injections and that leads to a high response rate in prior nonresponders to the HBsAg vaccine formulated with alum [5]. In Europe, this vaccine is licensed for use in dialysis patients but has not yet been licensed for use in healthy vaccine nonresponders [7]. Another approach has been the addition of CpG oligonucleotides, which, via stimulation of Toll-like receptor (TLR) 9, activate innate immune responses to the standard alum formulation of HBsAg [8]. Again, higher and earlier anti-HBs titers were induced in vaccinees, with protective anti-HBs titers occurring in the majority of vaccinees after a single inoculation. However, a clinical trial of a different TLR9 agonist was halted in March 2008 by the US Food and Drug Administration, for safety concerns [9]. A major reason for this slow development may lie in the heated debate regarding the safety of the standard hepatitis B vaccine that occurred during the late 1990s, when concern about an association of the vaccine with multiple sclerosis was raised. Although only trends for such an association had been reported in studies from France and the United Kingdom, it was not until 2001 that a large casecontrol study from the United States refuted a causal relationship [10]. Manufacturers, however, may have been worried that such allegations could arise again if a more immunogenic vaccine were to be used in the general population, and against this background it may have appeared overambitious and unrewarding to further improve a vaccine that was already 95% effective. So, what can be offered to current hepatitis B vaccine nonresponders? Most guidelines recommend a repeated course of vaccinations with the standard hepatitis B vaccine [11]. This approach leads to protective antibody titers in 50%–100% Received 7 April 2008; accepted 8 April 2008; electronically published 10 June 2008. Potential conflicts of interest: none reported. Financial support: This work is part of the activities of the VIRGIL European Network of Excellence on Antiviral Drug Resistance, which is supported by a grant (LSHM-CT-2004503359) from the Priority 1 “Life Sciences, Genomics and Biotechnology for Health” Programme of the 6th Framework Programme of the European Union. Reprints or correspondence: Dr. Helmut Diepolder, Dept. of Medicine II, University of Munich, Klinikum Grosshadern, Marchioninistr. 15, Munich, Bavaria D-81377, Germany (Helmut.Diepolder@med.uni-muenchen.de). The Journal of Infectious Diseases 2008; 198:297– 8 © 2008 by the Infectious Diseases Society of America. All rights reserved. 0022-1899/2008/19803-0001$15.00 DOI: 10.1086/589721 E D I T O R I A L C O M M E N T A R Y

Persistence of Antibodies Induced by Measles-Mumps-Rubella Vaccine in Children in India

Antibody levels in 41 Indian girls were measured 6 years after measles-mumps-rubella (MMR) vaccination. Rates of seropositivity were 88% (measles antibodies), 95% (mumps antibodies), and 100% (rubella antibodies). The MMR vaccine induces long-term immunity in a majority of vaccinees; however, due to the observation of some seronegative vaccinees, the policy of administering a second dose of the MMR vaccine seems appropriate.

Persistence of the immune response induced by BCG vaccination

BackgroundAlthough BCG vaccination is recommended in most countries of the world, little is known of the persistence of BCG-induced immune responses. As novel TB vaccines may be given to boost the immunity induced by neonatal BCG vaccination, evidence concerning the persistence of the BCG vaccine-induced response would help inform decisions about when such boosting would be most effective.MethodsA randomised control study of UK adolescents was carried out to investigate persistence of BCG immune responses. Adolescents were tested for interferon-gamma (IFN-γ) response to Mycobacterium tuberculosis purified protein derivative (M.tb PPD) in a whole blood assay before, 3 months, 12 months (n = 148) and 3 years (n = 19) after receiving teenage BCG vaccination or 14 years after receiving infant BCG vaccination (n = 16).ResultsA gradual reduction in magnitude of response was evident from 3 months to 1 year and from 1 year to 3 years following teenage vaccination, but responses 3 years after vaccination were still on average 6 times higher than before vaccination among vaccinees. Some individuals (11/86; 13%) failed to make a detectable antigen-specific response three months after vaccination, or lost the response after 1 (11/86; 13%) or 3 (3/19; 16%) years. IFN-γ response to Ag85 was measured in a subgroup of adolescents and appeared to be better maintained with no decline from 3 to 12 months. A smaller group of adolescents were tested 14 years after receiving infant BCG vaccination and 13/16 (81%) made a detectable IFN-γ response to M.tb PPD 14 years after infant vaccination as compared to 6/16 (38%) matched unvaccinated controls (p = 0.012); teenagers vaccinated in infancy were 19 times more likely to make an IFN-γ response of > 500 pg/ml than unvaccinated teenagers.ConclusionBCG vaccination in infancy and adolescence induces immunological memory to mycobacterial antigens that is still present and measurable for at least 14 years in the majority of vaccinees, although the magnitude of the peripheral blood response wanes from 3 months to 12 months and from 12 months to 3 years post vaccination. The data presented here suggest that because of such waning in the response there may be scope for boosting anti-tuberculous immunity in BCG vaccinated children anytime from 3 months post-vaccination. This supports the prime boost strategies being employed for some new TB vaccines currently under development.

Persistence of Antibodies Induced by Measles-Mumps-Rubella Vaccine in Children in India

Antibody levels in 41 Indian girls were measured 6 years after measles-mumps-rubella (MMR) vaccination. Rates of seropositivity were 88% (measles antibodies), 95% (mumps antibodies), and 100% (rubella antibodies). The MMR vaccine induces long-term immunity in a majority of vaccinees; however, due to the observation of some seronegative vaccinees, the policy of administering a second dose of the MMR vaccine seems appropriate.

Hemagglutinin Protein Is a Primary Target of the Measles Virus–Specific HLA‐A2–Restricted CD8+T Cell Response during Measles and after Vaccination

To characterize the measles virus (MV)-specific T cell responses important for evaluation of measles vaccines, human leukocyte antigen (HLA)-A2-positive and -negative adults immunized with measles-mumps-rubella vaccine were studied. Both groups developed increases in antibody and in interferon (IFN)- gamma -producing cells in response to pooled hemagglutinin (H) and fusion peptides. HLA-A2-binding peptides were predicted for all MV-encoded proteins and confirmed by T2 cell stabilization. Twenty-nine peptides were tested, and 19 (6 from H) stimulated increased IFN- gamma secretion in a majority of vaccinees. Peptide-loaded HLA-A2 tetramers or immunoglobulin dimers documented MV-specific CD8+ T cell responses after vaccination and during measles and confirmed new A2 epitopes in H (250-259 and 516-525 aa) and matrix (M; 50-58 aa) protein and previously described epitopes in H (30-38 aa), M (211-219 aa), and nonstructural protein C (84-92 aa). No single peptide dominated the response. We conclude that H is an important stimulus for CD8+ T cell as well as for antibody responses in HLA-A2-positive individuals.

Study of the serological response after vaccination against tick-borne encephalitis in Sweden

The antibody response to vaccination against tick-borne encephalitis (TBE) with FSME-Immun™ Inject (Immuno AG/Baxter) was studied in 535 persons, mainly adults, attending a vaccination centre in Stockholm, Sweden. Emphasis was laid on long-term follow-up. Antibody activity was measured by three different serological test systems: a commercial ELISA kit, a hemagglutination inhibition (HI) test and a neutralization test (RFFIT). The neutralization test proved to be the most sensitive assay for the detection of the vaccine response, which was demonstrable in the majority of vaccinees (>90% after three and >98% after four and five vaccinations, respectively). ELISA and HI were less sensitive for antibody measurement during primary immunization. Neutralizing antibody activity persisted prior to the third dose in 77% of the vaccinees and prior to the fourth to sixth doses in 89–95% of the vaccinees. ELISA activity, but no neutralizing activity, was found in some individuals. Based on our data and previous experience of vaccine failures after two doses, a more condensed three-dose vaccination schedule may be advantageous and ought to be tested. The persistence of neutralizing antibodies justifies further studies of the antibody responses after the fourth dose for periods beyond the recommended 3-year booster intervals.

Induction of Multifunctional Human Immunodeficiency Virus Type 1 (HIV-1)-Specific T Cells Capable of Proliferation in Healthy Subjects by Using a Prime-Boost Regimen of DNA- and Modified Vaccinia Virus Ankara-Vectored Vaccines Expressing HIV-1 Gag Coupled to CD8+T-Cell Epitopes

A double-blind randomized phase I trial was conducted in human immunodeficiency virus type 1 (HIV-1)-negative subjects receiving vaccines vectored by plasmid DNA and modified vaccinia virus Ankara (MVA) expressing HIV-1 p24/p17 gag linked to a string of CD8(+) T-cell epitopes. The trial had two groups. One group received either two doses of MVA.HIVA (2x MVA.HIVA) (n=8) or two doses of placebo (2x placebo) (n=4). The second group received 2x pTHr.HIVA followed by one dose of MVA.HIVA (n=8) or 3x placebo (n=4). In the pTHr.HIVA-MVA.HIVA group, HIV-1-specific T-cell responses peaked 1 week after MVA.HIVA vaccination in both ex vivo gamma interferon (IFN-gamma) ELISPOT (group mean, 210 spot-forming cells/10(6) cells) and proliferation (group mean stimulation index, 37), with assays detecting positive responses in four out of eight and five out of eight subjects, respectively. No HIV-1-specific T-cell responses were detected in either assay in the 2x MVA.HIVA group or subjects receiving placebo. Using a highly sensitive and reproducible cultured IFN-gamma ELISPOT assay, positive responses mainly mediated by CD4(+) T cells were detected in eight out of eight vaccinees in the pTHr.HIVA-MVA.HIVA group and four out of eight vaccinees in the 2x MVA.HIVA group. Importantly, no false-positive responses were detected in the eight subjects receiving placebo. Of the 12 responders, 11 developed responses to previously identified immunodominant CD4(+) T-cell epitopes, with 6 volunteers having responses to more than one epitope. Five out of 12 responders also developed CD8(+) T-cell responses to the epitope string. Induced T cells produced a variety of anti-viral cytokines, including tumor necrosis factor alpha and macrophage inflammatory protein 1 beta. These data demonstrate that prime-boost vaccination with recombinant DNA and MVA vectors can induce multifunctional HIV-1-specific T cells in the majority of vaccinees.

Rational Design of AIDS Vaccines

Development of an effective vaccine against HIV has posed significant challenges to the scientific community. Lack of knowledge about the molecular pathogenesis of this disease, and the absence of naturally occurring, protective immune responses, which is attributed in large part to the diversity of the viral envelope and multiple escape mechanisms, have made it difficult to design successful candidates. Recent studies of the envelope have suggested that it is possible to enhance immunogenicity of the envelope by improving the breadth of the neutralizing antibody response and by stimulating cell-mediated immunity. This relies on an understanding of the structure of HIV Env and the use of site-specific mutation to create novel immunogens. Based on structural and functional data, our lab has developed DNA and adenoviral vectors which express envelope proteins containing alterations to regions in the variable loop to better control tropism and improve immunogenicity. These modified HIV genetic vaccine candidates have been tested in combination with Gag, Pol, and Nef immunogens, and shown to improve the potency of cellular and humoral immune responses in primates. An initial Phase I trial (VRC 004) dose escalation study to test a DNA vaccine composed of a 4-plasmid combination of clade B gag/pol/nef with clades A, B, and C envelope was recently completed in 50 healthy adults in the U.S. CD4+ and CD8+ T cell responses were detected in the majority of vaccinees using IFN-(ELISpot) and flow cytometric detection of intracellular IL-2 or IFN-γ. HIV-specific antibody response was detected in about one third of vaccinees. Combination modality regimens using a DNA vaccine prime followed by a viral vector boost have shown promise in nonhuman primate models of HIV infection. Phase I clinical trials to test the safety and immunogenicity of an adenoviral vaccine expressing proteins similar to the DNA, and a DNA prime, adenoviral boost regimen are in progress. The initial adenoviral vector vaccine uses an Ad5 serotype vector. However, pre-existing immunity can mitigate the efficacy, so alternate serotypes and modifications to the adenoviral fiber regions are being explored. from 2005 International Meeting of The Institute of Human Virology Baltimore, USA, 29 August – 2 September 2005

Prävention der Frühsommer-Meningoenzephalitis (FSME)

Active immunization is the only reliable means of preventing TBE. Evidence suggests that effectiveness is greater than 95%. Breakthrough infections in fully immunized individuals, however, do occur. Recent data indicate that the duration of protection following basic immunization is substantially longer than previously appreciated. The vast majority of vaccinees are still seropositive > or = 8 years after the last dose. Thus, the current practice of administering booster doses every 3 years is a topic of intense debate. Until it is resolved, patients can be offered the determination of a serum anti-TBE IgG titre as an alternative to "blind" administration of a booster dose. It has recently been shown that seropositivity determined by some commonly used commercial ELISA tests correlates closely with the presence of protective antibody. In Switzerland, TBE vaccination is currently recommended for individuals older than 6 years of age who frequently dwell in endemic areas. Since 2005, health care insurances are required to cover for costs incurred by immunization according to these recommendations.

Vaccination of yeast sensitive individuals: review of safety data in the US vaccine adverse event reporting system (VAERS)

The preparation of recombinant hepatitis B vaccines involves using cellular cultures of Saccharomyces cerevisiae, otherwise known as baker's yeast. Prior to vaccine licensure, clinical trials were performed to address whether residual yeast proteins in the vaccines could induce anaphylaxis, including testing for IgE anti-yeast antibody levels. 1–2% of subjects had anti-yeast IgE antibodies before immunization, but demonstrated no significant rise in IgE after HBV. We searched reports in the Vaccine Adverse Event Reporting System (VAERS) for those that mentioned a history of allergy to yeast and then reviewed the adverse events described in these reports for potential anaphylactic reactions. Probable anaphylaxis was defined as the presence of one or more dermatologic symptoms and one or more respiratory, gastrointestinal, or cardiovascular symptoms with onset within 4 h of Hepatitis B vaccination. Possible anaphylaxis was defined in one of two ways: (1) cases that described dermatologic or respiratory symptoms (but not both) occurring within 4 h of vaccination; or (2) cases that described one or more dermatologic and/or respiratory symptoms occurring 4–12 h post vaccination. Among the 107 reports of pre-existing “yeast allergies,” 11 reports described probable or possible anaphylaxis after HBV. Four additional cases were described after other vaccines. The majority of vaccinees who met the case definitions and had a history of yeast allergies were female, ages ranged from 10 to 64, and symptom onset ranged from 15 min to 5 h after vaccination. No deaths were reported. The small number of reports to VAERS may be partly due to health care professionals observing current contraindications by not vaccinating yeast sensitive individuals. Nevertheless, yeast associated anaphylaxis after HBV in sensitized patients appears to be a rare event.

Differential Regulation of Granzyme and Perforin in Effector and Memory T Cells following Smallpox Immunization

Primary immunization of healthy adults with vaccinia virus induces a local vesicle or "take" in the majority of vaccinees that previously has been shown to correlate with protection against smallpox. However, the immunologic mechanisms underlying this protective response in humans are not well characterized. We have studied human CD8+ T cells for the expression patterns of phenotypic markers and cytolytic effector molecules before and after primary smallpox immunization using nine-color polychromatic flow cytometry. One month after immunization, vaccinees developed vaccinia virus-specific CD8+ T cells with an effector cell phenotype containing both granzyme A and granzyme B. One year after immunization, we found a significant decrease in granzyme B containing cells and an increased memory cell phenotype in virus-specific CD8+ T cells. Perforin was rarely expressed directly ex vivo, but was highly expressed after Ag-specific activation in vitro. Together, these data suggest an important role for effector CD8+ T cells in controlling poxvirus infection, and have implications for our understanding of human CD8+ T cell differentiation.

C-reactive protein and vaccinia specific lymphocyte proliferative responses following smallpox immunization

Rationale An understanding of the immune response to smallpox vaccination is needed for evaluation of adverse events and for development of new vaccines. Methods Lymphocyte proliferative responses (LPA) to UV-irradiated vaccinia and serum C-reactive protein (CRP) were measured for 51 smallpox vaccine (Dryvax®) recipients at three time points: before, 11-16 and 28-30 days after immunization. Subjects included 21 primary vaccinees and 30 re-vaccinees (prior vaccination ≥10 years). All subjects developed vaccination site major reactions (or “takes”). Results An LPA stimulation index (SI) >3 post-immunization was observed in 44 (86.3%) total, 17 (81.0%) primary, and 27 (90.0%) re-vaccinees. The mean SI was greater for primary than for re-vaccinees at all time points: 11.5 (0.4-43.9) versus 9.2 (0.4-35.1) on day 11-16 and 15.1 (0.2-76.9) versus 9.8 (0.55-38.0) on day 28-30. Pre-immunization LPA responses with a SI >3 were observed in 11 (52.4%) primary and 9 (30.0%) re-vaccinees. Post-immunization serum CRP levels increased to above the normal range (<0.8mg/dl) in only 1 subject. Conclusions Significant LPA responses more than 10 days following vaccination were observed in the majority of vaccinees, but not all. This may reflect the timing of sample acquisition post-immunization or the relocation of reactive lymphocytes to extravascular spaces. Some patients, particularly re-vaccinees, may have undetected early peak LPA responses. Elevated CRP levels greater than 10 days post-immunization do not appear to be part of the normal immune response.

Perspectives for a vaccine against hepatitis C virus

There is no vaccine for HCV and the only available treatment, IFNα alone or in combination with ribavirin, has proven efficacious in less than 50% of patients. Given that approximately 200 million chronic HCV infections have been estimated worldwide, there is a pressing need to develop vaccination strategies aimed at preventing and possibly eradicating HCV infection. However, several major practical and scientific problems arise in designing an HCV vaccine. First, HCV is only readily detected as RNA by PCR. Second, the only species that can be infected by HCV are humans and chimpanzees. Third, the virus does not replicate efficiently in vitro. Fourth, some viral proteins have very high mutability. Last, there is little information on correlates of immunity. Although an ideal vaccine should protect from infection, in that it should elicit sterilizing immunity, this is quite an ambitious goal in the PCR era. In the case of HCV, where acute HCV infection is a very limited health problem and infection can only be assessed by PCR, a more realistic goal might be to look for vaccines capable of protecting from chronic infection. We have preliminary evidence in chimpanzees that an HCV vaccine consisting of recombinant envelope proteins can elicit antibodies and inflammatory CD4+ T cell responses which can prevent chronic infection in the majority of vaccinees. Although the scientific and clinical challenges that need to be addressed are still substantial, advances in recombinant protein technology, novel adjuvants, and DNA vaccines, will be key in developing strategies to generate protective immunity against chronic HCV infection.

Annual influenza vaccination: immune response in patients over 10 years

Objective: To determine the effect of repeated annual influenza immunization on the host's serum antibody. Design: Ten year observational study with cohort design. Setting: Cystic Fibrosis Center at St. Vincent's Hospital and Medical Center, New York City, NY. Patients: Thirty-eight children and young adults with cystic fibrosis (CF). Measurements: Serum hemagglutination inhibition (HI) antibody titers were determined at the time of vaccination and 4 weeks later each year in the fall before the influenza epidemic. Shwachman scores were determined each year. Results: While the pre-vaccination and post-vaccination geometric mean serum HI antibody titers varied from year to year, no upward or downward trend was evident over the 10 year period. The reciprocal of the post-vaccination geometric mean HI titers ranged annually from 32 to 74 for the influenza A (H3N2) vaccine strains, from 53 to 133 for the influenza A (H1N1) strains, and from 18 to 174 for influenza B strains. In addition, the majority of vaccinees had a presumably protective post-vaccination serum HI titer ≥1:40 each year for all three vaccine strains. The initial mean Shwachman score of the group was 77. The final score of 76 after 10 years was not significantly different. Conclusions: Annual influenza vaccination appears to regularly induce presumably protective serum antibody levels in most CF children and young adults studied over a 10 year period.

Dissection of the human antibody response to the malaria antigen Pf155/RESA into epitope specific components

The development of vaccines is presently receiving major attention in malaria research. As it is not possible to base malaria vaccines on the use of killed or attenuated organisms, the vaccines which are being developed are subunit vaccines in which the immunogens consist of defined parasite antigens or antigenic fragments. Since protective immunity to malaria involves both antibody-dependent and antibody-independent mechanisms, the immunogens in a subunit vaccine must have the capacity to induce relevant B- and T-cell responses in the majority of vaccinees. In turn, this requires good knowledge of these responses in humans who have acquired immunity through natural infection. In this paper we have summarized our recent work on the dissection into epitope-specific components of the human antibody response to the Plasmodium falciparum antigen Pf155/RESA, a recognized candidate for a vaccine against the asexual blood stages of this parasite. Epitope mapping of the antigen by means of short synthetic peptides led to the identification in several molecular regions of short amino acid sequences constituting linear and probably immunodominant B-cell epitopes. The antigenically most active region was located in the C-terminus of the molecule. This region, which consists of approximately 40 related, 4- or 8-amino acid long repeats, induced higher antibody concentrations in a larger number of malaria-immune donors than any of the other regions. A large fraction of these antibodies bound to short synthetic peptides representing the major repeat motifs of Pf155/RESA. Although these repeats are made up of closely related amino acid sequences, the antibody response to them was highly polyclonal, indicating the presence of several linear and probably also conformational epitopes which gave rise to a variety of cross-reacting as well as monospecific antibodies. Further analysis revealed that the levels of antibodies differing in specificity and/or avidity for different peptides varied independently of each other in individual donors. In an area (Liberia) where malaria transmission is holoendemic and perennial, these antibody profiles remained constant when individual donors were followed over several years. Since the C-terminal repeat region of Pf155/RESA is conserved in different P. falciparum strains, the results reflect differences in the genetic regulation of epitope-specific host responses rather than antigenic differences between infecting parasites. In donors living in an area with high but seasonal malaria transmission, antibody levels usually drop to lower levels when there is no transmission.(ABSTRACT TRUNCATED AT 400 WORDS)