Immunogenicity and protective efficacy of a recombinant filamentous haemagglutinin from Bordetella pertussis

Bordetella pertussis is the causative agent of whooping cough, a major childhood pathogen; acellular vaccines consisting of purified B. pertussis antigens such as filamentous haemagglutinin (FHA) are commonly used to prevent pertussis. Despite the importance of FHA in B. pertussis pathogenesis and its inclusion in most acellular vaccines, the functional importance of individual domains in the induction of protective immunity is largely unknown. In this study, we have purified a recombinant FHA protein from Escherichia coli consisting of a 42 kDa maltose binding domain of E. coli and the 43 kDa type I immunodominant domain of FHA. The fusion protein (Mal85) was purified from E. coli cell lysates via affinity chromatography with an amylose column. Mal85 was then delivered to BALB/c mice intranasally encapsulated in liposomes, formulated with Protollin(TM) or in conjunction with an immunostimulatory CpG oligonucleotide. Mice were also vaccinated intraperitoneally with alum-adsorbed Mal85. Sera from all treatment groups showed strong IgG responses to Mal85 and recognized native FHA. Specific salivary IgA was induced in mice vaccinated with Mal85 in liposomes, Protollin(TM) and delivered with CpG. Vaccination with Mal85 encapsulated in liposomes or formulated with Protollin(TM) provided protection against aerosol challenge with B. pertussis in BALB/c mice. These data indicate that the type I domain of FHA is a protective antigen in mice and may serve as a candidate for inclusion in new acellular pertussis vaccines.

CpG-C ISS-ODN activation of blood-derived B cells from healthy and chronic immunodeficiency virus-infected macaques

Cytosine-phosphate-guanine class C (CpG-C) immunostimulatory sequence oligodeoxynucleotides (ISS-ODNs) activate human B cells and dendritic cells (DCs), properties that suggest potential use as a novel adjuvant to enhance vaccine efficacy. After demonstrating that the CpG-C ISS-ODN C274 activates macaque DCs, we examined in vitro activation of macaque B cells by C274 as a prelude to evaluation of this molecule as an adjuvant in the testing of candidate human immunodeficiency virus vaccines in the rhesus macaque-simian immunodeficiency virus (SIV) model. C274 induced macaque CD20(+) B cells to proliferate more strongly than CD40 ligand or CpG-B ISS-ODN. C274 enhanced B cell survival; increased viability was most evident after 3-7 days of culture. Increased expression of CD40, CD80, and CD86 by B cells was apparent within 24 h of exposure to C274 and persisted for up to 1 week. C274-stimulated, B cell-enriched and peripheral blood mononuclear cell suspensions from naïve and immunodeficiency virus-infected monkeys secreted several cytokines [e.g., interleukin (IL)-3, IL-6, IL-12, interferon-alpha] and chemokines [e.g., monocyte chemoattractant protein-1/CC chemokine ligand 2 (CCL2), macrophage-inflammatory protein-1alpha/CCL3, IL-8/CXC chemokine ligand 8]. In comparison, exposure of macaque B cells to SIV had minimal impact on surface phenotype, despite inducing cytokine and chemokine production in cells from infected and uninfected animals. These observations emphasize the need to identify strategies to optimally boost immune function, as immunodeficiency viruses themselves only partially activate B cells and DCs. The ability of C274 to stimulate B cells and DCs in healthy and infected monkeys suggests its possible use as a broad-acting adjuvant to be applied in the rhesus macaque model for the development of preventative and therapeutic vaccines.

Immunostimulatory sequence DNA linked to the Amb a 1 allergen promotes T(H)1 cytokine expression while downregulating T(H)2 cytokine expression in PBMCs from human patients with ragweed allergy

BACKGROUND

Recent studies have demonstrated that bacterially derived immunostimulatory sequences (ISSs) of DNA can activate the mammalian innate immune system and promote the development of T(H)1 cells. Promotion of T(H)1 immunity by means of immunotherapy in allergic patients has led to the alleviation of symptoms that result from allergen-specific T(H)2 responses.

OBJECTIVE

Our purpose was to investigate whether the T(H)1-enhancing properties of ISSs could be used to alter the T(H)2-dominated immune response of allergic PBMCs in vitro.

METHODS

Ragweed protein-linked ISS (PLI) was generated from a specific, highly active 22-base ISS and Amb a 1, the immunodominant allergen in ragweed pollen, to combine the T(H)1-enhancing properties of ISSs with allergen selectivity, and its activity was investigated in PBMC cultures from subjects with ragweed allergy.

RESULTS

PLI was markedly successful at reversing the dominant allergen-induced T(H)2 profile while greatly enhancing IFN-gamma production. Delivering ISSs in a linked form proved to be much more effective at modulating the resulting cytokine profile than delivering free ISSs in a mixture with unlinked Amb a 1. PLI also demonstrated cytokine-modulating properties, even when used to stimulate cells that had already been primed for 6 days with Amb a 1. The antigen specificity of the action of PLI was confirmed by the observations that PLI enhances Amb a 1--specific T-cell proliferation.

CONCLUSION

These data indicate that delivery of ISSs within an antigen-specific context exhibits potent cytokine-modulating activity and, combined with its reduced allergenicity, makes this molecule a strong candidate for use in improved immunotherapy applications.

The comparison of the effect of LTR72 and MF59 adjuvants on mouse humoral response to intranasal immunisation with human papillomavirus type 6b (HPV-6b) virus-like particles

Infections with genital human papillomaviruses (HPV) are likely to be neutralised more efficiently if a mucosal immune response can be elicited at the viral entry site. Local IgA antibodies are highly induced when antigens are co-administered with mucosal adjuvants, such as cholera toxin (CT) and Escherichia coli heat labile enterotoxin (LT) which, however, are not expected to have wide application because of their pronounced toxicity. We have immunised mice intranasally with HPV-6b virus-like particles (VLPs) and a genetically modified LT-derived molecule with only residual toxicity, LTR72, and compared the humoral responses with those obtained following systemic immunisation with VLPs and the MF59 adjuvant. Titration of anti-HPV antibodies in sera and vaginal secretions established that LTR72 was able to elicit higher serum and mucosal IgA titers, in addition to IgG serum levels, comparable to those obtained by parenteral immunisation. These results confirm the potential of toxin-derived adjuvants and extend their use in combination with HPV antigens.

Conjugation of immunostimulatory DNA to the short ragweed allergen amb a 1 enhances its immunogenicity and reduces its allergenicity

BACKGROUND

Allergen immunotherapy is inconvenient and associated with the risk of anaphylaxis. Efforts to improve the safety of immunotherapy by means of chemical modification of allergens have not been successful because it greatly reduced their antigenicity. Recently, immunostimulatory DNA sequences (ISS or CpG motifs) have been shown to act as strong T(H)1 response-inducing adjuvants.

OBJECTIVE

We sought to determine whether conjugation of ISS to the major short ragweed allergen Amb a 1 results in enhanced immunotherapeutic potential in mice and decreased allergenicity in human subjects.

METHODS

A 22-mer ISS oligodeoxynucleotide (ISS-ODN) was coupled to Amb a 1 and used for immunization of mice, rabbits, and monkeys.

RESULTS

In mice the Amb a 1-ISS conjugate induced a T(H)1 response (IFN-gamma secretion), whereas Amb a 1 induced a T(H)2 response (IL-5 secretion). The T(H)1 response was not observed with an Amb a 1-non-ISS conjugate. Coinjection of Amb a 1 with ISS-ODN was much less effective in inducing a T(H)1 response. In mice primed for a T(H)2 response, injection with Amb a 1-ISS conjugate induced a de novo T(H)1 response and suppressed IgE antibody formation after challenge with Amb a 1. Amb a 1-ISS conjugate induced high-titer anti-Amb a 1 IgG antibodies in rabbits and cynomolgus monkeys, whereas Amb a 1 alone or Amb a 1 coinjected with ISS-ODN did not induce a detectable response. Amb a 1-ISS conjugate was less allergenic than Amb a 1 alone, as shown by a 30-fold lower histamine release from human basophils of patients with ragweed allergy, whereas mixing ISS-ODN with Amb a 1 did not reduce histamine release.

CONCLUSION

Amb a 1-ISS conjugate has an enhanced T(H)1-biased immunogenicity and reduced allergenicity. It may offer a more effective and safer approach for allergen immunotherapy than currently available methods.

PCPP as a parenteral adjuvant for diverse antigens

The adjuvanticity of the phosphazene polymer, poly[di(carboxylatophenoxy) phosphazene] (PCPP) was examined with a diverse collection of immunogens. PCPP proved to be a potent adjuvant for trivalent influenza virus vaccine, tetanus toxoid, hepatitis B surface antigen, herpes simplex virus glycoprotein gD2 and the capsular polysaccharide, polyribosylribitolphosphate, from Haemophilus influenzae type b. Taken together these results clearly demonstrate the general utility of PCPP as an adjuvant. Furthermore, PCPP was a superior adjuvant at least with TT compared to similar negatively charged polyanions, polymethylacrylic acid and polyacrylic acid.

The adjuvant MF59 increases the immunogenicity and protective efficacy of subunit influenza vaccine in mice

The immunogenicity and protective efficacy of influenza vaccine with and without the adjuvant MF59 was determined in mice. The addition of MF59 significantly increased the antibody response to the vaccine antigens over a wide dose range. Equivalent antibody titres were seen using 50- to 200-fold lower antigen concentrations when combined with MF59 compared with vaccine alone. The humoral response was sustained for at least 6 months after immunization. The addition of MF59 increased the protective efficacy of the vaccine: the amount of live virus detectable in the lungs of mice challenged with virus 1-6 months after immunization was reduced and the rate of survival was significantly increased. Influenza vaccine combined with MF59 gave full protection from viral challenge at antigen doses 65- to 80-fold lower than with vaccine alone.

Isolation and characterization of human papillomavirus type 6-specific T cells infiltrating genital warts

The potential role of T cells in the control of human papillomavirus type 6 (HPV-6) infections is an appealing premise, but their actual role has been sparsely investigated. Since HPV-6 infections are confined to the epithelium, such an investigation should focus on the T cells present at the site of infection (i.e., the warts). Therefore, we isolated wart-infiltrating lymphocytes (WIL) from patients with clinically diagnosed anogenital warts. These WIL were characterized by their phenotype and their specificity for E7 and L1 proteins of HPV-6. The phenotype of WIL varied drastically from patient to patient, as determined by their expression of CD4, CD8, T-cell receptor alpha/beta chain (TCR alpha beta), and TCR gamma delta. Despite this heterogeneity in phenotype, HPV-6 E7 and/or L1-specific WIL, as determined by lymphoproliferation, could be isolated from more than 75% of the patients studied. Among all L1 peptides recognized by WIL, peptides 311-330 and 411-430 were the most consistently detected, with seven of nine patients for whom L1 peptide reactivity was observed responding to at least one of them. Moreover, the HPV-6 epitopic peptides recognized by WIL differed to some extent from those recognized by peripheral T cells.

Recent advances in vaccine adjuvants: the development of MF59 emulsion and polymeric microparticles

Vaccines produced by recombinant DNA technology are safer than 'traditional' vaccines but they are often poorly immunogenic, requiring adjuvants to enhance their immunogenicity. Particulate adjuvants of defined dimensions (< 5 microns) have been shown to be effective in enhancing the immunogenicity of 'weak' antigens in animal models. Two novel adjuvants that possess significant potential for the development of new vaccines are the MF59 sub-microemulsion and polymeric microparticles. MF59 is an oil-in-water emulsion and has been shown to be both potent and safe in human subjects with several vaccines. Microparticles prepared from the biodegradable polymer poly(lactide-co-glycolide) have been shown to enhance immunogenicity when administered by mucosal routes, such as oral and intranasal, and they also possess considerable potential for the development of single-dose vaccines through the use of controlled-release technology.

MF59 adjuvant enhances the antibody response to recombinant hepatitis B surface antigen vaccine in primates

The effect of the proprietary adjuvant MF59 on the immunogenicity of a recombinant hepatitis B virus (HBV) vaccine, PreS2+SAg, was investigated in baboons. The magnitude and duration of the antibody response to hepatitis B surface antigen (anti-HBs) induced by the HBV/MF59 vaccine was compared with the same antigen combined with alum and with two licensed alum vaccines. After one immunization, the HBV/MF59 vaccine generated anti-HBs titers >10 mIU/mL in a greater proportion of animals, and mean titers were 26- to 84-fold higher than titers from alum vaccines. After a third immunization, the HBV/MF59 vaccine generated titers 38- to 127-fold higher than alum vaccines. Seven months after the third immunization, HBV/MF59 elicited titers 75- to 472-fold higher than alum vaccines. The dramatic immune response elicited by HBV/MF59 in baboons suggests that MF59 may be a desirable adjuvant for use in improved HBV vaccines for humans.

MF59 adjuvant enhances the immunogenicity of influenza vaccine in both young and old mice

The responses of young (8 week) and old (18 month) mice to influenza vaccine with and without the potent emulsion adjuvant MF59 were compared. In influenza naive mice, vaccine-specific antibody and T-cell proliferation were significantly lower in the old group compared to the young group. Post-immunization cytokine levels and antibody isotype profiles were different in the old compared to the young mice. The addition of the adjuvant MF59, a submicron oil-in-water emulsion composed of 5% v/v squalene, 0.5% v/v Tween 80 and 0.5% v/v Span 85, significantly increased the immune responses of both the young and old naive mice to the vaccine. The responses of the old mice given adjuvant increased to levels equivalent to those of young mice with vaccine alone. In mice previously infected with influenza virus, similarly depressed immune responses to vaccination were detected in the old mice. While the addition of MF59 to the vaccine had little effect on antibody titres of the previously infected young mice, the adjuvant significantly increased the antibody responses of the previously infected old mice. These results suggest that influenza vaccine combined with MF59 may significantly improve immune responses of elderly humans to influenza vaccination.

Enhancement of humoral response against human influenza vaccine with the simple submicron oil/water emulsion adjuvant MF59

Human influenza subunit vaccines are not fully protective in either the very young or elderly populations where risk is greatest. The use of an adjuvant to enhance antibody titer is an attractive option to increase vaccine efficacy. A series of squalene/H2O emulsions stabilized either by the amphipathic muramyl peptide MTP-PE (sodium N-acetyl-muramyl-L-alanyl-D-isoglutaminyl-L-alanyl-2-(1',2'-dipalmitoyl- sn- glycero-3'phospho) ethylamide) or by mixtures of the sorbitan oleate surfactants Tween 80 and Span 85 have been tested as adjuvants with influenza vaccine. Combination of influenza vaccine with the Tween/Span stabilized emulsions has resulted in significantly higher antibody titers to vaccine in an extensive series of naive animal models. The use of submicron emulsion droplets is significant in determination of adjuvant activity while the presence of the muramyl peptide is not required for adjuvant activity. The 200-300 nm diameter emulsion formulation MF59 containing only the low toxicity components squalene, Tween 80 and Span 85 has been shown to enhance titers from 5 to 250 times that achievable with vaccine alone.

MF59. Design and evaluation of a safe and potent adjuvant for human vaccines

MF59 is a safe, practical, and potent adjuvant for use with human vaccines. The formulation is easily manufactured, may be sterilized by filtration, and is both compatible and efficacious with all antigens tested to date. MF59 has been shown to be a potent stimulator of cellular and humoral responses to subunit antigens in both animal models and clinical studies. Toxicology studies in animal models and Phase I-III studies in humans have demonstrated the safety of MF59 with HSV, HIV, and influenza vaccines.

The influence of adjuvant on the therapeutic efficacy of a recombinant genital herpes vaccine

The potential use of vaccines for treatment of chronic or persistent virus infections is an area of great interest and controversy. Previous experiments have shown that the incidence and severity of spontaneous recurrent genital herpes in latently infected guinea pigs could be significantly reduced by vaccination with herpes simplex virus glycoprotein subunit vaccines. The current study shows the critical role of adjuvant in an effective formulation. Immunization of previously infected guinea pigs with a subunit vaccine containing a muramyl peptide derivative, MTP-PE, in a low-oil emulsion as adjuvant reduced the incidence of recurrent disease up to 80% compared with formulations lacking MPT-PE. Vaccines containing adjuvant alone failed to modify recurrences. Alum, the traditional adjuvant, was not effective. Glycoprotein subunit vaccines elicited high-titer ELISA and neutralizing antibody responses far greater than those generated by virus infection. However, neither antibody titers nor lymphoproliferative responses reproducibly correlated with the pattern of recurrent disease.

Vaccination of chimpanzees against infection by the hepatitis C virus

A high incidence of community-acquired hepatitis C virus infection that can lead to the progressive development of chronic active hepatitis, liver cirrhosis, and primary hepatocellular carcinoma occurs throughout the world. A vaccine to control the spread of this agent that represents a major cause of chronic liver disease is therefore needed. Seven chimpanzees (Pan troglodytes) have been immunized with both putative envelope glycoproteins [E1 (gp33) and E2 (gp72)] that were copurified from HeLa cells infected with a recombinant vaccinia virus expression vector. Despite the induction of a weak humoral immune response to these viral glycoproteins in experimentally infected chimpanzees, a strong humoral immune response was obtained in all vaccines. The five highest responders showed complete protection against an i.v. challenge with homologous hepatitis C virus 1. The remaining two vaccines became infected, but both infection and disease may have been ameliorated in comparison with four similarly challenged control chimpanzees, all of which developed acute hepatitis and chronic infections. These results provide considerable encouragement for the eventual control of hepatitis C virus infection by vaccination.

Pilot evaluation of influenza virus vaccine (IVV) combined with adjuvant

The safety of licensed influenza virus vaccine (IVV) combined with a novel adjuvant containing muramyl tripeptide (MTP) conjugated to phosphatidylethanolamine (PE) was evaluated in a randomized pilot study. Ten healthy 23-30-year-old men were given a single intramuscular dose of IVV combined with saline (n = 5) or with 100 micrograms of MTP-PE in the MF59 adjuvant emulsion (MF59-100) (n = 5). Evaluations were performed on days 0, 1, 2, 4, 7 and 28 after inoculation. IVV alone was well tolerated. All volunteers immunized with IVV/MF59-100 experienced moderate to severe local and systemic reactions which interfered with usual activities. Discomfort at the injection site was first noted at 2-6 h; induration (5/5), erythema (3/5), and regional adenopathy (3/5) persisted for up to 4 days. Systemic symptoms including chills (5/5), fever (3/5), nausea (3/5) and/or dizziness (2/5) developed within 12 h of inoculation and resolved by 48 h. Elevated white blood cell count (days 1 and 2), erythrocyte sedimentation rate and serum fibrinogen were transiently observed. Although peak serum neutralizing antibody titres versus influenza A/H3N2 and influenza B antigens were higher in the group given IVV with MF59-100, these unexpected reactions indicate that this dose of adjuvant is unsuitable for use in combination with this IVV.

The effect of adjuvants on the efficacy of a recombinant herpes simplex virus glycoprotein vaccine

A recombinant, truncated HSV type 1 glycoprotein D secreted by Chinese hamster ovary cells (rgD1) was used to compare the ability of several adjuvants to stimulate protective immunity in guinea pigs. Adjuvants tested included CFA, aluminum hydroxide (alum), a lipophilic derivative of muramyl tripeptide (MTP-PE), and a muramyl dipeptide (MDP) covalently conjugated to rgD1. Animals were immunized three times with rgD1 plus the various adjuvants and antibody titers were determined by ELISA. Four weeks after the last immunization, the animals were challenged intravaginally with HSV type 2 and were monitored daily for clinical signs of disease, including frequency and severity of herpetic lesions, incidence of urinary retention, and mortality during the 14-day post-challenge observation period. Animals immunized in the foot-pad with rgD1 formulated with CFA showed the highest antibody titers. Animals immunized in the footpad with rgD1 using MTP-PE in a 4% squalene formulation, alum, or rgD1 conjugated to MDP showed mean antibody titers that were 57, 16, and 13% of the CFA titers, respectively. Immunization with rgD1 plus MTP-PE, alum, or rgD1-MDP conjugate by the i.m. route elicited lower antibody titers than the footpad route of immunization. Results of the viral challenge indicated that clinical symptoms of the groups immunized with rgD1 with CFA or MTP-PE as adjuvant were similar in magnitude and were markedly reduced compared with unimmunized control groups. Animals immunized with rgD1 combined with alum or rgD1-MDP conjugate showed clinical symptoms significantly more severe than the CFA or MTP-PE groups. The protective immunity observed after i.m. immunization of animals with rgD1 and MTP-PE was only slightly lower than animals immunized with the same Ag-adjuvant combination in the footpad. The results indicate that MTP-PE is an effective adjuvant for the recombinant herpes gD vaccine.

The effect of adjuvants on the efficacy of a recombinant herpes simplex virus glycoprotein vaccine

A recombinant, truncated HSV type 1 glycoprotein D secreted by Chinese hamster ovary cells (rgD1) was used to compare the ability of several adjuvants to stimulate protective immunity in guinea pigs. Adjuvants tested included CFA, aluminum hydroxide (alum), a lipophilic derivative of muramyl tripeptide (MTP-PE), and a muramyl dipeptide (MDP) covalently conjugated to rgD1. Animals were immunized three times with rgD1 plus the various adjuvants and antibody titers were determined by ELISA. Four weeks after the last immunization, the animals were challenged intravaginally with HSV type 2 and were monitored daily for clinical signs of disease, including frequency and severity of herpetic lesions, incidence of urinary retention, and mortality during the 14-day post-challenge observation period. Animals immunized in the foot-pad with rgD1 formulated with CFA showed the highest antibody titers. Animals immunized in the footpad with rgD1 using MTP-PE in a 4% squalene formulation, alum, or rgD1 conjugated to MDP showed mean antibody titers that were 57, 16, and 13% of the CFA titers, respectively. Immunization with rgD1 plus MTP-PE, alum, or rgD1-MDP conjugate by the i.m. route elicited lower antibody titers than the footpad route of immunization. Results of the viral challenge indicated that clinical symptoms of the groups immunized with rgD1 with CFA or MTP-PE as adjuvant were similar in magnitude and were markedly reduced compared with unimmunized control groups. Animals immunized with rgD1 combined with alum or rgD1-MDP conjugate showed clinical symptoms significantly more severe than the CFA or MTP-PE groups. The protective immunity observed after i.m. immunization of animals with rgD1 and MTP-PE was only slightly lower than animals immunized with the same Ag-adjuvant combination in the footpad. The results indicate that MTP-PE is an effective adjuvant for the recombinant herpes gD vaccine.

Expression of cell-associated and secreted forms of herpes simplex virus type 1 glycoprotein gB in mammalian cells

The gene for glycoprotein gB1 of herpes simplex virus type 1 strain Patton was expressed in stable Chinese hamster ovary cell lines. Expression vectors containing the dihydrofolate reductase (dhfr) cDNA plus the complete gB1 gene or a truncated gene lacking the 194 carboxyl-terminal amino acids of gB1 were transfected into CHO DHFR-deficient cells. Radioimmunoprecipitation demonstrated that the complete gB1 protein expressed in CHO cell lines was cell associated, whereas the truncated protein was secreted from the cells due to deletion of the transmembrane and C-terminal domains of gB1. Cells expressing the truncated gB1 protein were subjected to stepwise methotrexate selection, and a cell line was isolated in which the gB1 gene copy number had been amplified 10-fold and the level of expression of gB1 had increased over 60-fold. The truncated gB1 protein was purified from medium conditioned by the amplified cell line. N-terminal amino acid sequence analysis of this purified protein identified the signal peptide cleavage site and predicted the cleavage of a 30-amino-acid signal sequence from the primary protein. The immunogenicity of the truncated gB1 protein was also tested in mice, and high levels of antibody and protection from virus challenge were observed.

Structure of the hepatitis A virion: peptide mapping of the capsid region

Milligram amounts of highly purified hepatitis A virus (HAV) were obtained from persistently infected cell cultures. The HAV polypeptides were separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and transferred to nitrocellulose for detection by an enzyme-linked immunotransfer blot procedure. The HAV nucleotide-derived amino acid sequence was subjected to computer analysis to identify potential immunogenic regions within the HAV capsid polypeptides. Synthetic peptides corresponding to selected regions of each of the larger putative capsid polypeptides were coupled to keyhole limpet hemocyanin and used to immunize rabbits. Four of six anti-HAV peptide sera were strongly reactive. Antipeptide serum generated against amino acids (a.a.) 75 through 82 reacted with the 27,000-molecular-weight (MW) polypeptide; serum against a.a. 279 through 285 reacted with the 29,000-MW HAV polypeptide; and sera against a.a. 591 through 602 and 606 through 618 reacted with the 33,000-MW HAV polypeptide. These reactions enabled the identification of the gene order of the larger HAV P1 region gene products. Our data indicate the following molecular weights: HAV VP2 or 1B, 27,000; HAV VP3 or 1C, 29,000; and HAV VP1 or 1D, 33,000.

Recombinant DNA approaches to feline leukemia virus immunization

We have utilized 2 recombinant DNA strategies for immunization against FeLV in cats: (a) modified live virus was attenuated by mutation and recombination, and (b) an immunogen, consisting of subunit envelope protein, was prepared in genetically engineered yeast. Results indicated that the genetically manipulated live virus preparations were not protective against FeLV challenge because they were either not attenuated in virulence or were not sufficiently antigenic. Immunization with yeast-synthesized FeLV envelope protein followed by the modified live virus gave protective immunity in cats under experimental conditions. Future immunization attempts will concentrate on enhancing the immunogenic potency of the yeast- synthesized FeLV envelope protein.

Effects of dexamethasone and 5-bromodeoxyuridine on protein synthesis and secretion during in vitro pancreatic development

Protein synthesis and secretion during in vitro pancreatic development and after treatment with the glucocorticoid dexamethasone and the thymidine analog 5-bromodeoxyuridine (BrdU) was monitored using two-dimensional gel electrophoresis. At 14 days gestation, the synthesis of more than 200 proteins and the secretion of a complex set of proteins was detected. The relative rate of synthesis and secretion of the majority of this set of proteins decreased dramatically during development; after 6 days of culture most were no longer detected. In contrast, the synthesis and secretion of pancreas-specific exocrine proteins amylase, a Sepharose binding protein (protein 2), and chymotrypsinogen first detected after one day in culture, increased throughout the 6-day culture period. Other pancreatic digestive (pro)enzymes normally found in the adult such as the basic form of chymotrypsinogen, lipase, ribonuclease, and trypsinogen were not detected during the culture period. Thus at least two distinct regulatory events are involved in the expression of the exocrine genes during development. Dexamethasone treatment during the 6-day culture period selectively increased the synthesis of amylase and several other minor secretory proteins. BrdU treatment caused major changes in the protein synthetic and secretory patterns of the pancreas as well as in morphogenesis. BrdU treated pancreases showed greatly reduced synthesis of amylase, protein 2, and chymotrypsinogen and prolonged synthesis of many proteins normally detected only at early stages of pancreatic development. BrdU treatment also stimulated the secretion of a set of proteins ostensibly associated with duct cells. Thus, BrdU specifically alters the developmental program of the pancreas.