Immunization Procedures Research Articles

Ammodytoxin content of Vipera ammodytes ammodytes venom as a prognostic factor for venom immunogenicity

Venoms are complex mixtures of proteins, peptides and other compounds whose biochemical and biological variability has been clearly demonstrated. These molecules have been used as antigens for immunization of anti-venom-producing animals (horses or sheep). Ammodytoxins (Atx) are potently neurotoxic compounds, and the most toxic compounds isolated so far from the Vipera ammodytes ammodytes (Vaa) venom. Recently we have shown that the level of antibodies specific to Vaa venom's most toxic component, ammodytoxin A (AtxA), (anti-AtxA IgG) in Vaa venom immunized rabbit sera highly correlated to the venom toxicity–neutralization potential of these sera. Here we investigated whether Atx content of Vaa venom could influence the outcome of immunization procedure. The novel ELISA was developed for precise determination of Atx content and Atx was quantified in venom samples used for immunization of rabbits. We clearly showed that animals immunized with the venom containing lower amount of Atx produced sera with significantly lower venom toxicity–neutralizing power and, vice versa, animals immunized with venoms containing higher amount of Atx produced sera with higher venom toxicity–neutralizing ability. Thus, the content of Atx in Vaa venom is a relevant parameter of its suitability in the production of highly protective Vaa anti-venom.

Immunizing Children Who Fear and Resist Needles: Is It a Problem for Nurses?

Despite increasing evidence that immunization procedures can be stressful for children, little is known about what the experience of immunizing frightened and needle-resistant children can be like for nurses. This article presents findings from a qualitative research project designed to explore public health nurses' feelings toward immunizing needle-resistant children. A constructivist theoretical perspective and an action research approach framed the study. Data sources included two survey questions and audio-recorded transcribed data from three focus groups. Participants included 35 public health nurses from five different health units in one Canadian province. The data were analyzed for themes and were confirmed with participants through ongoing member checking. The following four overarching themes were identified and are used to explain and describe significant features of the immunization experience that were stressful and problematic for nurses: (a) nurses experience stress when immunizing children who fear and resist needle injection; (b) the strength of child resistance and some adult behavior creates an ethical dilemma for nurses; (c) some adult responses make immunizing difficult and unsafe; and (d) resources to help nurses cope with these situations are inconsistent.

Investigation of the causative agents for community-acquired pneumonia in adult patients

Community-acquired pneumonia (CAP) is a common condition in healthy people, causing morbidity and mortality worldwide despite latest advances in therapy and immunization procedures. Causative agents cannot be detected in approximately 50% of CAP episodes and therapy is initiated empirically. We aimed to determine the spectrum and frequency of the causative agents in patients with CAP in a university hospital. Materials and methods: Seventy seven adult patients hospitalized with CAP from November 2007 to March 2008 were included. CAP was diagnosed with clinical, radiological, and laboratory signs. Results: Sputum and blood cultures grew Streptococcus pneumoniae in 15 specimens; Haemophilus influenzae in 4, Klebsiella pneumoniae in 4, Staphylococcus aureus in 3, and Escherichia coli in 2. Mycoplasma pneumoniae DNA was detected in serum from 10 patients with RT-PCR. Legionella pneumophila urinary antigen was detected in 5 patients. Serological IgM antibodies to Chlamydia pneumoniae in 7 patients and Respiratory Syncytial Virus in 2 patients were observed. Etiology was not determined in 32.5% of patients. The most frequently identified pathogens causing CAP were S. pneumoniae, M. pneumoniae, and C. pneumoniae in descending order in our hospital. Conclusion: Although determination of causative agents in all CAP patients has not been accomplished, knowledge of the spectrum and frequency of local causative agents are valuable for targeted therapy.

The Human UGT1A3 Enzyme Conjugates Norursodeoxycholic Acid into a C23-ester Glucuronide in the Liver

Norursodeoxycholic acid (norUDCA) exhibits efficient anti-cholestatic properties in an animal model of sclerosing cholangitis. norUDCA is eliminated as a C(23)-ester glucuronide (norUDCA-23G) in humans. The present study aimed at identifying the human UDP-glucuronosyltransferase (UGT) enzyme(s) involved in hepatic norUDCA glucuronidation and at evaluating the consequences of single nucleotide polymorphisms in the coding region of UGT genes on norUDCA-23G formation. The effects of norUDCA on the formation of the cholestatic lithocholic acid-glucuronide derivative and of rifampicin on hepatic norUDCA glucuronidation were also explored. In vitro glucuronidation assays were performed with microsomes from human tissues (liver and intestine) and HEK293 cells expressing human UGT enzymes and variant allozymes. UGT1A3 was identified as the major hepatic UGT enzyme catalyzing the formation of norUDCA-23G. Correlation studies using samples from a human liver bank (n = 16) indicated that the level of UGT1A3 protein is a strong determinant of in vitro norUDCA glucuronidation. Analyses of the norUDCA-conjugating activity by 11 UGT1A3 variant allozymes identified three phenotypes with high, low, and intermediate capacity. norUDCA is also identified as a competitive inhibitor for the hepatic formation of the pro-cholestatic lithocholic acid-glucuronide derivative, whereas norUDCA glucuronidation is weakly stimulated by rifampicin. This study identifies human UGT1A3 as the major enzyme for the hepatic norUDCA glucuronidation and supports that some coding polymorphisms affecting the conjugating activity of UGT1A3 in vitro may alter the pharmacokinetic properties of norUDCA in cholestasis treatment.

Mucosal Immunity: Induction, Dissemination, and Effector Functions

Prevention of infections by vaccination remains a compelling goal to improve public health. Most infections involve the mucosae, but the development of vaccines against many of these pathogens has yet to be successful. Mucosal vaccines would make immunization procedures easier, be better suited for mass administration, and most efficiently induce immune exclusion - a term coined for non-inflammatory antibody shielding of internal body surfaces - mediated principally by secretory immunoglobulin A (SIgA). The exported antibodies are polymeric, mainly IgA dimers (pIgA) - produced by local plasma cells stimulated by antigens that target the mucosae. SIgA was early shown to be complexed with an epithelial glycoprotein - the secretory component (SC). In 1974, a common SC-dependent transport of pIgA and pentameric IgM was proposed. From the basolateral surface, pIg-SC complexes are taken up by endocytosis and finally extruded into the lumen. Membrane SC is now referred to as polymeric Ig receptor (pIgR). In 1980, it was shown to be synthesized as a larger transmembrane protein - first cloned from rabbit and then from human. Mice deficient for pIgR showed that this is the only receptor responsible for epithelial transport of IgA and IgM. In the gut, induction of B cells occurs in gut-associated lymphoid tissue, particularly the Peyer's patches, but also in mesenteric lymph nodes. Plasma cell differentiation is accomplished in the lamina propria to which the memory/effector cells home. The airways also receive such cells from nasopharynx-associated lymphoid tissue - but by different homing receptors. Such compartmentalization is a challenge for development of mucosal vaccines.

Characterization and in vitro activities of cell-free antigens from Histoplasma capsulatum-loaded biodegradable microspheres

In the last decades, the incidence of histoplasmosis, a pulmonary fungal disease caused by Histoplasma capsulatum, has increased worldwide. In this context, vaccines for the prevention of this infection or therapies are necessary. Cell-free antigens (CFAgs) from H. capsulatum when administered for murine immunization purposes are able to confer protection and control of the infection, since they activate cellular immunity. However, the most of vaccination procedures need several antigens administrations and immunoadjuvants, which are not approved for use in humans. The aim of this study was to develop and characterize a vaccination approach using biodegradable PLGA microspheres (MS) that could allow the controlled and/or sustained release of the encapsulated antigens from H. capsulatum. CFAgs-loaded MS presented a size less than 10 μm, were marked engulfed by bone marrow-derived macrophages (BMDMϕ) and induced the nitric oxide (NO) and tumor necrosis factor-α (TNF-α) production by these cells. Our data show that CFAgs-loaded MS induce cell activation, suggesting an immunostimulant effect to be further investigated during immunization procedures. CFAgs-loaded MS present potential to be used as vaccine in order to confer protection against H. capsulatum infection.

Combined immersion and oral vaccination of Vietnamese catfish ( Pangasianodon hypophthalmus) confers protection against mortality caused by Edwardsiella ictaluri

Edwardsiella ictaluri septicemia occurs worldwide and causes high mortality and considerable economic damage to the catfish industry especially in Vietnam and the USA. To control Edwardsiella septicemia farmers extensively use antibiotics and various vaccination methods. Vaccination with inactivated vaccines has come with variable efficacy. In this trial the results of an approach of controlling Edwardsiella septicemia of Tra catfish ( Pangasianodon hypophthalmus) in Vietnam through vaccination via mucosal surfaces are presented. The results show that a combination of primary vaccination by immersion with inactivated E. ictaluri followed by an oral boost with a formulated antigen preparation induces a statistically significant level of protection against mortality caused by experimental infection 4 weeks post-boost. Fish immunized by immersion only show significantly lower level of protection but significantly higher than the controls. Repeated boosts result in improved duration of immunity with a relative percent survival (RPS) of 47% at 90% control mortality. The immunization procedure provides an alternative for disease control through vaccination.

Assessment of Monoclonal Gammopathies by Nephelometric Measurement of Individual Immunoglobulin κ/λ Ratios

Currently, monoclonal immunoglobulins are identified and quantified from bands on electrophoretic gels. As an alternative, clonality might be determined by measuring the separate light chain types of each Ig class to allow numerical assessment of Ig'kappa/Ig'lambda ratios, analogous to free light chain kappa/lambda ratios. Using immunization, tolerization, and adsorption procedures, we prepared sheep antibodies against each of the 6 separate molecules, IgGkappa, IgGlambda, IgAkappa, IgAlambda, IgMkappa, and IgMlambda. Antibody targets comprised the junctional epitopes between the heavy chain and light chain domains. After purification, we assessed the antisera on a Siemens Dade-Behring BN II nephelometer for analytical quality and clinical utility. High-avidity, specific antibodies allowed the production of automated nephelometric immunoassays for each Ig light chain type. Laboratory comparison with serum protein electrophoresis, using dilution experiments, showed lower analytical sensitivity for monoclonal IgG detection but similar or greater sensitivity for IgA and IgM, particularly when the monoclonal bands overlaid transferrin. Results obtained from typing of monoclonal proteins into IgG, A, or M types were comparable with results obtained by immunofixation-electrophoresis methods. Initial clinical studies, in multiple myeloma patients, indicated that Ig'kappa/Ig'lambda ratios were sometimes more sensitive than immunofixation electrophoresis, provided numerical results, and correlated with changes in disease. Immunoassays for intact Ig kappa/lambda pairs are possible and should assist in the management of patients with monoclonal gammopathies.

Murine Monoclonal Antibodies Generated Against Mouse/Rat Hemokinin-1

The mouse/rat hemokinin-1 (m/rHK-1) was discovered nearly 9 years ago. This molecule is a peptide comprising 11 amino acids. The m/rHK-1 was found to be mainly expressed in central immune organs like bone marrow, and was proven to have lymphopoietic roles in B and T lymphocyte development. m/rHK-1was also reported to have analgesic roles in rat spinal cord, in addition to other functions such as relaxing activity on coronary artery. Unlike its analogues SP, NKA, and NKB, m/rHK-1 does not express in the nervous system. To further study the distribution and function of m/rHK-1, we carried out conventional immunization and cell fusion procedures to acquire the hybridomas secreting specific monoclonal antibodies to m/rHK-1. In the 17 positive clones obtained, three antibodies named 1B12, 2B4, and 4G5 were shown representative in cross-reactivity against m/rHK-1 and its analogues by indirect ELISA, competitive indirect ELISA, and immunofluorescence assays. Among the three clones, the 2B4 monoclonal antibody appeared to be the high-titered and specific clone to m/rHK-1. Monoclonal antibodies to m/rHK-1 will function as good tools in the physiological study of m/rHK-1 in the near future.

A hybrid immune simulated annealing algorithm for the job shop scheduling problem

A hybrid simulated annealing algorithm based on a novel immune mechanism is proposed for the job shop scheduling problem with the objective of minimizing total weighted tardiness. The proposed immune procedure is built on the following fundamental idea: the bottleneck jobs existing in each scheduling instance generally constitute the key factors in the attempt to improve the quality of final schedules, and thus, the sequencing of these jobs needs more intensive optimization. To quantitatively describe the bottleneck job distribution, we design a fuzzy inference system for evaluating the bottleneck level (i.e. the criticality) of each job. By combining the immune procedure with a simulated annealing algorithm, we design a hybrid optimization algorithm which is subsequently tested on a number of job shop instances. Computational results for different-sized instances show that the proposed hybrid algorithm performs effectively and converges fast to satisfactory solutions.

Age-dependent systemic antibody responses and immunisation-associated changes in mice orally and nasally immunised with Lactococcus lactis expressing a malaria parasite protein

Gram positive food-grade bacteria such as lactococci have significant advantages over attenuated pathogens as vaccine delivery vehicles because of their inherently greater safety. Plasmodium falciparum merozoite surface antigen 2 (MSA2) was expressed in recombinant Lactococcus lactis both intracellularly and covalently anchored to the peptidoglycan of the cell wall (MSA2cP). Balb/c mice of different ages were immunised with the MSA2cP expressing L. lactis in a combined oral and nasal immunisation procedure. Serum IgG antibody responses to MSA2 were higher in young adult Balb/c mice compared to old mice and neonates. The elicited serum IgG antibodies reacted with native MSA2 on the surface of P. falciparum merozoites in an immunofluorescence assay. The serum IgG antibody isotypes in young adult mice were mainly IgG1, IgG2a and IgG2b, while IgG3 tended to be higher in old mice. IgA antibodies to MSA2 were also produced in young mice. Enlarged mesenteric lymph nodes, and more prominent lymphoid tissue in the lamina propria of the ileum and lymphoid follicles in the spleen, were observed in mice fed L. lactis. These findings are relevant for developing L. lactis as a vector to deliver vaccines in human populations.

Study on rhGM-CSF as adjuvant in revaccination among adults of non-and hyporesponders to hepatitis B vaccine

To investigate the effect of recombinant human granulocyte macrophage colony stimulating factor (rhGM-CSF) as adjuvant on immune response in adults of non-and hyporesponders to hepatitis B vaccine. Those who were once immunized with recombined yeast gene hepatitis B vaccine more than one standard scheme in two years and negative for hepatitis B markers were randomly sorted as group A and group B. 33 adults of group A were given hepatitis B vaccine 10 microg each time. The immune procedure was 0, 1 and 6 month. 34 adults of group B were given rhGM-CSF 300 microg for the first day, then 10 microg each time for routine immune. The blood samples were collected before the first injection and in 1, 2 and 8 months (T1, T2, T8) following the first injection to test Anti-HBs. Anti-HBs positive conversion rates of group A and B at T8 was 39.39% and 64.71% respectively (P = 0.038). Anti-HBs levels of group B at T1, T2, T8 were (113.85 +/- 198.56) mIU/ml, (312.40 +/- 349.44) mIU/ml, (427.74 +/- 411.58) mIU/ml (P = 0.001). There was significant difference between group A and B in T8 Anti-HBs levels (P = 0.010). Better immune response was found in the group of rhGM-CSF with hepatitis B vaccine. So rhGM-CSF can induce the immune respond to hepatitis B vaccine.

Die Therapie der schweren Sepsis

The sepsis syndrome is defined as a clinically suspected infection accompanied by systemic manifestations. The emergence of one or multiple organ dysfunctions is the hallmark of severe sepsis. The significance of sepsis in pulmonary medicine is highlighted by the fact that severe pneumonia is the most prevalent cause of sepsis in non-surgical intensive care medicine and that acute lung injury is among the prominent manifestations of severe sepsis. The formation of major study groups and competence centres during the last decade has made meaningful prospective interventional studies possible that, in turn, have resulted in the development of clinical treatment algorithms. Today, the multidisciplinary treatment of severe sepsis includes haemodynamic, respiratory, endocrine, immune, and coagulation aspects besides the control of the underlying infection. While new concepts of shock treatment and mechanical ventilation have been established by means of confirmatory studies, endocrine interventions as well as immune and anticoagulation procedures are still under investigation.

Immunosenescence and cancer vaccines.

Experimental and clinical data demonstrate that ageing is associated with the gradual deterioration of the immune system, generally referred to as immunosenescence. Age-related immune dysfunction may have an impact not only on the incidence of cancer, but also on the preventive and therapeutic approaches, which are based on immune system activation. Over the last few years the use of immunological measures to prevent cancer in experimental mouse models involving preimmunization with new vaccines against even a poor or apparently non-immunogenic tumour has yielded worse outcomes in older age than in young adults. Different mechanisms, which may be due to age-related numerical or functional dysfunction of immune cells and/or to tumour microenvironmental changes, could be responsible for this defect. This review summarises the impact of immunosenescence on the effectiveness of cancer vaccines, knowledge of cancer immunisation in old age and the potential mechanisms implicated in the poorer effectiveness of anticancer immune-based approaches in advanced age. Several approaches to, and possibilities of correcting the low effectiveness of immunisation procedures in old age are described.

Cytokine expression in colostrum-deprived pigs immunized and challenged with Haemophilus parasuis

The expression of several cytokines in spleen, pharyngeal lymph nodes, lung and brain after different immunization procedures and a challenge with 5 × 10 9 CFU of Haemophilus parasuis was compared. Five groups of colostrum-deprived pigs were used: vaccinated with (I) a bacterin, (II) an outer-membrane-protein-vaccine, (III) a recombinant transferring-binding protein B, (IV) exposed to a total dose of 10 5 CFU, and (V) not previously immunized. All pigs in groups III and V died, while all animals in group I, most of group IV and half of group II survived until the end of the experiment. IL-1α was found in significantly higher levels ( p < 0.05) in spleen, lymph nodes and brain of dead pigs, which could be explained by the major severity of lesions in these animals. However, IL-4, IL-10, TNF-α and IFN-γ were expressed in significantly higher levels by survivors (for all the four cytokines in lymph nodes; for IL-4, IL-10 and TNF-α in spleen; for IL-4, TNF-α and IFN-γ in lung, and only for TNF-α in brain), thus suggesting a role of these four cytokines in the adaptive response, which might contribute to protection against H. parasuis infection.

Transcutaneous immunization by lipoplex-patch based DNA vaccines is effective vaccination against Japanese encephalitis virus infection

Skin, the biggest organ of human body, contains antigen presenting cells such as Langerhans cells (LCs) that modulate various immune responses. The skin therefore is an ideal venue to effect the transcutaneous immunization (TCI). Most current immunization procedures make use of needles and syringes for vaccine administration, which however have raised many safety concerns. To overcome the stratum corneum barrier of the skin without carrying out any skin penetration, cationic liposomes, DC-Chol/DOPE and DOTAP, were employed as vehicles for the transdermal antigen DNA delivery in this study. The optimal ratio of liposomes to DNAs for maximal transfection efficiency was determined to be 5:1 (w/w) for both formulas in BHK-21 cell transfection assays. This ratio was applied to lipoplex in tests on the dorsal skin of hair-removed mice. Reporter genes were found expressed in epidermis and spleen over 3 days. C3H/HeN mice transcutaneously immunized with the skin patch containing liposome-pCJ-3/ME (lipoplex-patch; pCJ-3/ME expressing the whole membrane and envelope protein genes of Japanese encephalitis virus (JEV)) can induce effective and protective antibodies against the infection with 50 times the 50% lethal dose (LD 50) of JEV. The developed lipoplex-patch DNA vaccines have proven to be simple and noninvasive, by which the antibodies incurred provide marked therapeutic effects in test animals.

Oral Vaccination Against Lactococcosis in Rainbow Trout (Oncorhynchus mykiss) Using Sodium Alginate and Poly (lactide-co-glycolide) Carrier

Summary As an alternative immunization procedure against lactococcosis in rainbow trout, encapsulated antigens immobilized in sodium alginate (SA) and poly lactide-co-glycolide (PLGA) polymers were administrated as a feed additive. Positive controls were intraperitoneally (IP) administered with aqueous-based bacterin (vaccine) while negative controls were not vaccinated. Positive control groups were immunized intraperitoneally by using the aqueous-based bacterin. Relative percentage survival (RPS) values of groups immunized orally with SA and (PLGA) encapsulated vaccines were not significantly different and was 53.48% and 62.79% respectively (on the 30 th day). No statistically significant difference was determined between the SA and (PLGA) vaccine groups and relative percentage survival (RPS) values of the two groups determined to be 53.48% and 62.79%, respectively. To determine the effect of the booster immunization by using encapsulated immobilized vaccines, booster immunization was performed on the 61 st day after oral administration of the same vaccines and RPS value was more than 60% on the 90 th 120 th days. After an aqueous-based vaccine followed by an immobilized vaccine for booster, the RPS value has increased over more than 80% indicating that booster application has increased the protection of rainbow trout against lactococcosis. It can be suggested that both SA and PLGA oral vaccines can be effectively used in rainbow trout against lactococcosis and there was no significant differences between the protection levels, however, since the preparation costs of SA oral vaccines are relatively lower compared to PLGA ones its usage for vaccination appears more appropriate.

Does the Neonatal Facial Coding System Differentiate Between Infants Experiencing Pain-Related and Non-Pain-Related Distress?

The Neonatal Facial Coding System (NFCS) is widely accepted as a measure of infant pain-related distress in known pain-specific contexts. It has clearly shown the ability to distinguish between facial reactivity in no-pain and pain-related situations. The primary purpose of this study was to explore whether NFCS differentiates between pain-related and non-pain-related distress. Two groups of 35 infants (1 group was distressed before injection whereas the other group was not distressed before injection) were coded using NFCS before and after an immunization procedure. Within-group analyses of infants who were distressed before immunization suggested that NFCS was not able to discriminate between pain-related and non-pain-related distress. However, between-group analyses showed NFCS discriminated between potential gradations of distress in infants after immunization. Results suggest that NFCS has the ability to discriminate between intensities of distress but not between pain-related and non-pain-related distress. Adding to the NFCS validity literature, this study suggests that while able to distinguish between no-distress and pain-related distress, facial actions of NFCS may not distinguish between pain-related and non-pain-related distress expressions. However, NFCS was able to discern infants presumed to have higher pain-related distress due to experiencing pre-needle distress.

Reduction of Plasma Levels of Soluble Tumor Necrosis Factor and Interleukin‐2 Receptors by Means of a Novel Immunoadsorption Column

This non-randomized open clinical study investigated the safety and efficacy of extracorporeal fractionated plasma adsorption using the Oncosorb immune adsorption column. The column selectively bound soluble tumor necrosis factor receptors 1 and 2 (sTNF-R1 and sTNF-R2) and soluble interleukin-2 receptors (sIL2-R) by lowering plasma levels in patients with metastatic cancer. Nine patients (three men and six women; mean age 48 years, aged 41-68 years) with metastatic cancer received at least 12 immune adsorption procedures. Thrice-weekly immune adsorption separated a low molecular weight (150 000 D) plasma fraction from the patients' blood, passing the plasma fraction through the column in an extracorporeal plasma perfusion circuit. Respective plasma receptor mean concentrations before and after 167 procedures were: sTNF-R1: 1936 +/- 788 pg/mL before treatment vs. 1312 +/- 989 pg/mL after treatment; sTNF-R2: 3140 +/- 1173 pg/mL before treatment vs. 1816 +/- 1 +/- 1677 pg/mL after treatment (P < 0.01 for each inhibitor). Mean reductions in sTNF-R1 (48%), sTNF-R2 (55%), and sIL2-R levels (72%) were observed for treatments 3-12 (P < 0.001). Clinical findings indicated tumor inflammation and necrosis in most patients. Side-effects were low-grade fever, flu-like symptoms; tumor pain and redness, warmth, tenderness, and edema. The column demonstrated safety and efficacy in lowering plasma sTNF-R1, sTNF-R2, and sIL2-R levels. Minor clinical adverse effects common to the use of extracorporeal devices were seen.

Generating antibodies against the native form of the human prion protein (hPrP) in wild-type animals: A comparison between DNA and protein immunizations

Generation of therapeutic antibodies against human proteins is hampered by the difficulty of obtaining large quantities of correctly folded immunogens when following classic immunization procedures. Here we compared several genetic immunization protocols for their potential ability to generate high levels of antibodies against proteins expressed in their native form. We chose as a model the prion protein (PrP) because it has been demonstrated that the recognition of the native conformation of PrP is an absolute prerequisite for anti-PrP antibodies to be used as therapeutic tools for prion diseases, a group of lethal neurodegenerative disorders. We designed two human PrP-DNA vectors, containing or not a stimulatory T cell epitope, which were injected into mice following four different protocols: in the naked form with or without electroporation, or protected by cationic polymers or block copolymers. For comparison, other animals received conventional injections of recombinant human PrP with Freund's adjuvant or alum. We found that genetic immunization, carried out especially through DNA electroporation and, to a lesser extent, through injection of block copolymer-protected DNA, was able to generate high amounts of antibodies recognizing native PrP as expressed on the cell surface. Conversely, protein immunizations led to very high levels of antibodies against PrP immobilized on microtiter plates, but unable to recognize the native cell membrane-bound PrP. This clearly demonstrates the usefulness of genetic immunization, when performed under well defined conditions, in raising antibodies to native proteins. These results are of interest not only in view of passive immunotherapy of prion diseases, but also, more generally, in view of generating antibodies to human membrane proteins for immunotherapeutic or immunodiagnostic purposes.