Human diploid cell culture rabies vaccine (HDCV) and purified chick embryo cell culture rabies vaccine (PCECV) both confer protective immunity against infection with the silver-haired bat rabies virus strain (SHBRV)

The demonstration of extensive differences in the antigenic makeups of the silver-haired bat rabies virus (SHBRV) and canine rabies virus (COSRV) strains raised concerns as to whether current licensed rabies vaccines are sufficiently protective against SHBRV. NIH mouse protection test results show that both the human diploid cell culture rabies vaccine (HDCV) and the purified chicken embryo cell rabies vaccine (PCECV) protected against lethal infection with SHBRV as well as the canine rabies strain COSRV. However, in this investigation, the potencies of both vaccines in mice were found to be significantly higher for COSRV than for SHBRV. The in vivo protection data are confirmed by in vitro virus neutralizing antibody (VNA) test results which demonstrate that mice immunized with HDCV or PCECV develop significantly higher VNA titres against COSRV than against SHBRV. In contrast, VNA tests of sera from individuals immunized with HDCV or PCECV showed that humans, as opposed to mice, develop significantly higher VNA titres against SHBRV than against COSRV. These data suggest that HDCV and PCECV will protect humans against infection with the silver-haired but rabies virus strain in addition to canine rabies virus strains.     

Effect of passive immunization or maternally transferred immunity on the antibody response to a genetic vaccine to rabies virus

A plasmid vector, termed pSG5rab.gp, expressing the glycoprotein of rabies virus was tested in young adult or neonatal mice in the presence of maternally transferred immunity or passively administered antibodies to rabies virus for induction of an antibody response. Mice born to rabies virus-immune dams developed an impaired antibody response to genetic immunization at 6 weeks of age, as had been previously observed upon vaccination with an inactivated viral vaccine. Similarly, mice passively immunized with hyperimmune serum showed an inhibited B-cell response upon vaccination with the pSG5rab.gp vector, resulting in both cases in vaccine failures upon challenge with a virulent strain of rabies virus. In contrast, the immune responses of mice vaccinated as neonates in the presence of maternal immunity or upon passive immunization to rabies virus with the pSG5rab.gp construct were only marginally affected.     

Apoptosis plays an important role in experimental rabies virus infection

Cultured rat prostatic adenocarcinoma (AT3) cells infected with the challenge virus standard (CVS) strain of fixed rabies virus showed characteristic morphologic features of apoptosis, evidence of oligonucleosomal DNA fragmentation, and expression of the Bax protein. CVS-infected Bcl-2-transfected AT3 cells did not demonstrate these features. Adult ICR mice inoculated intracerebrally with CVS showed morphologic changes of apoptosis, DNA fragmentation, and increased Bax expression in neurons, with changes most marked in the hippocampus and cerebral cortex. Ultrastructurally, some neurons demonstrated morphologic features more typical of necrosis. These studies provide evidence that apoptosis plays an important role in the pathogenesis of rabies virus infection.     

Mumps epidemic in vaccinated children in West Switzerland

Since 1991, 6 years after the recommendation of universal childhood vaccination against measles, mumps, and rubella (MMR triple vaccine), Switzerland is confronted with a large number of mumps cases affecting both vaccinated and unvaccinated children. Up to 80% of the children suffering from mumps between 1991 and 1995 had previously been vaccinated, the majority with the Rubini vaccine strain. On the basis of a case-control study including 102 patients and 92 controls from the same pediatric population, a study of the humoral immune-response following vaccination with the Rubini vaccine in 6 young adult volunteers, and two different genetic studies, we investigated the complex problem of large scale vaccine failure in Switzerland. We conclude that the recently reported large number of Swiss mumps cases was caused by at least four interacting factors: 1. A vaccine coverage of 90-95% at the age of 2 years is necessary to interrupt mumps wild virus circulation. The nationwide vaccine coverage in Switzerland of some 80% in 27-36 month-old children is too low. 2. Primary vaccine failures (absence of seroconversion or unprotective low levels of neutralizing antibodies), as well as secondary vaccine failures due to the rapid decline of antibodies to mumps virus in our volunteers and controls, seem to be frequent after vaccination with the Rubini strain. 3. Despite its reported Swiss origin, the Rubini strain does not belong to the mumps virus lineages recently circulating in this area but is closely related to American mumps virus strains. 4. Differences in protein structure between the vaccine strain and the circulating wild type strains, and in particular a different neutralization epitope in the hemagglutinin neuraminidase protein, may additionally contribute to the lack of protection in vaccinated individuals.     

Clinical study on air in epidural hematomas

Twenty 2nd specific pathogen-free pigs were divided into 4 groups: Group A were infected with porcine reproductive and respiratory syndrome (PRRS) virus at 6 weeks of age and treated with available swine erysipelas and swine fever combined vaccine (vaccinated) at 7 weeks of age; Group B were vaccinated at 7 weeks of age and infected with PRRS virus at 8 weeks of age; Group C were vaccinated at 7 weeks of age: Group D were neither vaccinated nor infected with PRRS virus. All pigs were challenged to Erysipelothrix rhusiopathiae C42 strain at 10 weeks of age. No clinical signs appeared after vaccination of group A and B pigs, thus confirming that the safety of the vaccine was not influenced by infection with PRRS virus. None of the pigs in Groups A and C developed erysipelas after challenge exposure to E. rhusiopathiae. In contrast, fever and/or urticaria appeared transiently in all pigs of Group B after challenge exposure. At the time of challenge exposure to E. rhusiopathiae, the PRRS virus titer was high in sera of Group B, but was low in those from Group A. However, vaccination of pigs with attenuated E. rhusiopathiae was effective in dual infection with PRRS virus and E. rhusiopathiae, because the clinical signs were milder and the E. rhusiopathiae strain was less recovered from these pigs compared to pigs of group D.     

The importance of MHC-I and MHC-II responses in vaccine efficacy against lethal herpes simplex virus type 1 challenge

To investigate the importance of major histocompatability complex (MHC) class I- and MHC class II-dependent immune responses in herpes simplex virus-1 (HSV-1) vaccine efficacy, groups of beta 2% (MHC I-) and Ab% (MHC II-) mice were inoculated with various vaccines, and then challenged intraperitoneally with HSV-1. Following vaccination with either live avirulent HSV-1, expressed HSV-1 glycoprotein D (gD), or a mixture of seven expressed HSV-1 glycoproteins (7gPs), Ab% (MHC-II-) mice developed no enzyme-linked immunosorbent assay (ELISA) or neutralizing antibody titres. In contrast, significant ELISA and neutralizing antibody titres were induced in beta 2m% (MHC-I-) mice by all three vaccines. The neutralizing antibody titres were similar for all three vaccines, but were only approximately 1/4 to 1/3 of that developed in C57BL/6 (parental) mice vaccinated with the same antigens. All three vaccines protected 100% of the wild-type C57BL/6 mice against lethal challenge with 2 x 10(7) plaque-forming units (PFU) of HSV-1. The live virus vaccine and the 7gPs vaccine also protected 80% of the beta 2m% mice against the same lethal HSV-1 challenge dose. In contrast, in Abo/o mice, none of the vaccines provided significant protection against the same lethal challenge dose of HSV-1. However, at a lower challenge dose of 2 x 10(6) PFU, all three vaccines protected 70-80% of the vaccinated Ab% mice (compared to only 10% survival in mock vaccinated controls). Thus, vaccination provided some protection against lethal HSV-1 challenge in both beta 2m% and Ab% mice; however, the protection was less than that seen in the parental C57BL/6 mice. In addition, Ab% mice were less well protected by vaccination than were beta 2m% mice. Our results suggest that (1) both MHC-I and MHC-II are involved in vaccine efficacy against HSV-1 challenge; (2) both types of responses must be present for maximum vaccine efficacy: and (3) the MHC-II-dependent immune response appeared to be more important than the MHC-I-dependent immune response for vaccine efficacy against HSV-I challenge.     

Gap junctional communication and the tyrosine phosphorylation of connexin 43 in interaction between breast cancer and endothelial cells

An antigenic double mutant of rabies virus (challenge virus standard [CVS] strain) was selected by successive use of two neutralizing antiglycoprotein monoclonal antibodies, both specific for antigenic site III. This mutant differed from the original virus strain by two amino acid substitutions in the ectodomain of the glycoprotein. The lysine in position 330 and the arginine in position 333 were replaced by asparagine and methionine, respectively. This double mutant was not pathogenic for adult mice. When injected intramuscularly into the forelimbs of adult mice, this virus could not penetrate the nervous system, either by the motor or by the sensory route, while respective single mutants infected motoneurons in the spinal cord and sensory neurons in the dorsal root ganglia. In vitro experiments showed that the double mutant was able to infect BHK cells, neuroblastoma cells, and freshly prepared embryonic motoneurons, albeit with a lower efficiency than the CVS strain. Upon further incubation at 37 degrees C, the motoneurons became resistant to infection by the mutant while remaining permissive to CVS infection. These results suggest that rabies virus uses different types of receptors: a molecule which is ubiquitously expressed at the surface of continuous cell lines and which is recognized by both CVS and the double mutant and a neuron-specific molecule which is not recognized by the double mutant.     

Vaccine genotype and route of administration affect pseudorabies field virus latency load after challenge

The influence of vaccine genotype and route of administration on the efficacy of pseudorabies virus (PRV) vaccines against virulent PRV challenge was evaluated in a controlled experiment using five genotypically distinct modified live vaccines (MLVs) for PRV. Several of these MLVs share deletions in specific genes, however, each has its deletion in a different locus within that gene. Pigs were vaccinated with each vaccine, either via the intramuscular or intranasal route, and subsequently challenged with a highly virulent PRV field strain. During a 2-week period following challenge with virulent PRV, each of the vaccine strains used in this study was evaluated for its effectiveness in the reduction of clinical signs, prevention of growth retardation and virulent virus shedding. One month after challenge, tissues were collected and analyzed for virulent PRV latency load by a recently developed method for the electrochemiluminescent quantitation of latent herpesvirus DNA in animal tissues after PCR amplification. It was determined that all vaccination protocols provided protection against clinical signs resulting from field virus challenge and reduced both field virus shedding and latency load after field virus challenge. Our results indicated that vaccine efficacy was significantly influenced by the modified live vaccine strain and route of administration. Compared to unvaccinated pigs, vaccination reduced field virus latency load in trigeminal ganglia, but significant differences were found between vaccines and routes of administration. We conclude that vaccine genotype plays a role in the effectiveness of PRV MLVs.     

Vaccination against tick-borne encephalitis virus, a flavivirus, prevents disease but not infection, although viremia is undetectable

By adoptive transfer of sera or immunoglobulin preparations, vaccine-induced protection against TBEV has been demonstrated to be mediated by antibodies to the surface protein of TBEV, glycoprotein E. Nevertheless, the mechanism of vaccine-induced protection against TBEV remains unclear. Protection by E antibodies without in vitro neutralization was shown by one group, whereas others found a correlation between protection in vivo and neutralization in vitro. Here, the authors confirm in a mouse model of tick-borne encephalitis (TBE) that immunization with the whole-killed virus vaccine protects mice against a subsequent challenge with a highly lethal dose of virus, i.e. 250 LD50 doses. Vaccine-induced immunity, however, is not completely neutralizing as demonstrated by the development of immune responses to a non-structural virus protein absent from the vaccine, yet expressed in the course of virus replication. Antibodies specific for the non-structural protein 1 (NS1) and cytotoxic T-cells could be detected after, but not prior to, virus challenge of vaccinated animals, establishing that protection by this highly effective vaccine is not equivalent with complete neutralization of the challenge virus.     

Effect on viraemia of an American and a European serotype PRRSV vaccine after challenge with European wild-type strains of the virus

Three groups of 10 pigs were vaccinated with an American serotype porcine reproductive and respiratory syndrome virus (PRRSV) vaccine and three groups of 10 pigs were vaccinated with a European serotype PRRSV vaccine. A control group of 12 pigs was left unvaccinated. Four weeks after vaccination the PRRSV-specific antibody titres were determined and each group was challenged with either a Spanish, German or Dutch PRRSV wild-type strain. The serological responses four weeks after vaccination confirmed that the two vaccines were of different serotypes. Vaccination with the American serotype vaccine hardly reduced the level of viraemia after challenge with the European PRRSV wild-type strains, and only after challenge with the Spanish PRRSV strain was a moderate, statistically significant reduction in viraemia observed. In contrast, after vaccination with the European serotype vaccine, viraemia was completely suppressed after challenge with the German PRRSV isolate and almost completely suppressed after challenge with the Spanish and Dutch PRRSV isolates.     

Assay of oral vaccination of dogs against rabies in Tunisia with the vaccinal strain SADBern

The possibility of immunizing dogs orally against rabies, using SADBern, an attenuated strain, was tested on dogs in the field in Tunisia. This strain induced high neutralizing antibody titres and conferred to all vaccinated dogs total resistance against a challenge with a Maghrebian strain. However, an excretion of virus of vaccinal origin was observed in one dog, hampering the use of SADBern in dogs. Nevertheless, this work demonstrates for the first time that dogs in developing countries, especially those which are inaccessible to parenteral vaccination, could be efficiently immunized against rabies by the oral route.     

Vaccine protection by a triple deletion mutant of simian immunodeficiency virus

Twelve rhesus monkeys were vaccinated with SIVmac316 delta nef (lacking nef sequences), and 12 were vaccinated with SIVmac239 delta3 (lacking nef, vpr, and upstream sequences in U3). SIVmac316 and SIVmac239 differ by only eight amino acids in the envelope; these changes render SIVmac316 highly competent for replication in macrophages. Seventeen of the animals developed persistent infections with the vaccine viruses. Seven of the 24 vaccinated animals, however, developed infections that were apparently transient in nature. Six of these seven yielded virus from peripheral blood when tested at weeks 2 and/or 3, three of the seven had transient antibody responses, but none of the seven had persisting antibody responses. The 24 monkeys were challenged in groups of four with 10 rhesus monkey infectious doses of wild-type, pathogenic SIVmac251 at weeks 8, 20, and 79 following receipt of vaccine. None of the seven with apparently transient infections with vaccine virus were protected upon subsequent challenge. Analysis of cell-associated viral loads, CD4+ cell counts, and viral gene sequences present in peripheral blood in the remainder of the monkeys following challenge allowed a number of conclusions. (i) There was a trend toward increased protection with length of time of vaccination. (ii) Solid vaccine protection was achieved by 79 weeks with the highly attenuated SIV239 delta3. (iii) Solid long-term protection was achieved in at least two animals in the absence of complete sterilizing immunity. (iv) Genetic backbone appeared to influence protective capacity; animals vaccinated with SIV239 delta3 were better protected than animals receiving SIV316 delta nef. This better protection correlated with increased levels of the replicating vaccine strain. (v) The titer of virus-neutralizing activity in serum on the day of challenge correlated with protection when measured against a primary stock of SIVmac251 but not when measured against a laboratory-passaged stock. The level of binding antibodies to whole virus by enzyme-linked immunosorbent assay also correlated with protection.     

Postinfectious antirabic vaccination of children with duck embryo vaccine and heterologous rabies hyperimmunity serum (author's transl)

After contact with a rabies-infected rabbit, 31 Persons were submitted to complete vaccination treatment with duck embryo vaccine, comprising of injections of 1.0 ml each every fast night and two booster injections of 1.0 ml each, which were administered 10 and 20 days, respectively, after the end of the 14 days' vaccination series. After performance of intracutaneous and ophthalmic tests, 18 children received heterologous rabies immunserum (Behring) in a dose of 0.2 ml per kg of body weight before the beginning of the vaccination series. Six weeks after the start of the vaccination series neutralizing and complement-fixing antibodies (rate of conversion 100 per cent) were detected in all patients. The mean titre of neutralizing antibodies (mouse test 200 LD 50 Fixed virus, strain CVS) amounted to 1:140, that of complement-fixing antibodies to 1:41. Severe incompatibility reactions were not observed. Outpatient treatment with duck embryo vaccine therefore seems to be fully justified.     

Onset of protective immunity in chicks after vaccination with a recombinant herpesvirus of turkeys vaccine expressing Newcastle disease virus fusion and hemagglutinin-neuraminidase antigens

The onset of protective immunity from lethal Newcastle disease virus (NDV) challenge of chicks was determined after vaccination with a recombinant herpes virus of turkeys (HVT) expressing the fusion and hemagglutinin-neuraminidase proteins of NDV. One-day-old specific-pathogen-free chicks devoid of maternal antibodies to NDV were vaccinated with 130 to 3300 plaque forming units of HVT (depending on the trial) and then challenged at 4, 7, 10, and 14 days postvaccination (DPV) with a neurotropic velogenic strain of NDV (GB Texas). The recombinant vaccine afforded 0%, 35-75%, 85%, and 94-100% protection when the vaccinated birds were challenged at 4, 7, 10, and 14 DPV, respectively. In all trials, challenge caused 100% mortality in unvaccinated control chicks. Newcastle disease virus was reisolated from the lung, liver, spleen, and brain of birds dying in all trials regardless of vaccine dosage or time of challenge, except when challenge occurred at 14 DPV.     

The vaccine efficacy of native paramyosin (Sj-97) against Chinese Schistosoma japonicum

One of the promising anti-schistosome vaccine candidates currently under investigation is paramyosin, a 97-kDa myofibrillar protein located in the muscles and tegument of schistosome worms. Here we describe the results of two vaccination/challenge experiments undertaken in mice using native paramyosin isolated from adult worms of a Chinese strain of Schistosoma japonicum. In both sets of experiments, a relatively low but consistent and significant reduction in worm burden was evident in mice vaccinated subcutaneously with S. japonicum paramyosin and Freund's adjuvant. In contrast, intraperitoneal vaccination of mice with Chinese strain S. japonicum paramyosin without adjuvant did not result in any reduction in worm numbers when compared with a saline control group. These data contrast with the impressive protection figures reported by another group who used a similar intraperitoneal vaccination protocol with native paramyosin extracted from Philippine strain S. japonicum.     

Characterization of a live-attenuated retroviral vaccine demonstrates protection via immune mechanisms

Live-attenuated retroviruses have been shown to be effective retroviral vaccines, but currently little is known regarding the mechanisms of protection. In the present studies, we used Friend virus as a model to analyze characteristics of a live-attenuated vaccine in protection against virus-induced disease. Highly susceptible mice were immunized with nonpathogenic Friend murine leukemia helper virus (F-MuLV), which replicates poorly in adult mice. Further attenuation of the vaccine virus was achieved by crossing the Fv-1 genetic resistance barrier. The minimum dose of vaccine virus required to protect 100% of the mice against challenge with pathogenic Friend virus complex was determined to be 10(3) focus-forming units of attenuated virus. Live vaccine virus was necessary for induction of immunity, since inactivated F-MuLV did not induce protection. To determine whether immune cells mediated protection, spleen cells from vaccinated donor mice were adoptively transferred into syngeneic recipients. The results indicated that immune mechanisms rather than viral interference mediated protection.     

Prediction of microcirculatory oxygen transport by erythrocyte/hemoglobin solution mixtures

Vaccination with naked DNA may be an alternative to conventional vaccines because it combines the efficacy of attenuated vaccines with the biological safety of inactivated vaccines. We recently showed that the vaccination with naked DNA coding for the immunorelevant glycoprotein D (gD) of pseudorabies virus (PRV) induced both antibody and cell-mediated immunity in pigs and provided protection against challenge infection. To determine whether the efficacy of the naked DNA vaccination against PRV could be improved, we compared three sets of variables. First, the efficacy of the naked DNA vaccine coding only for the immunorelevant gD was compared with a cocktail vaccine containing additional plasmids coding for two other immunorelevant glycoproteins, gB and gC. Second, the intramuscular route of vaccination was compared with the intradermal route. Third, the commonly used needle method of inoculation was compared with the needleless Pigjet injector method. Five groups of five pigs were vaccinated three times at 4-weeks intervals and challenged with the virulent NIA-3 strain of PRV 6 weeks after the last vaccination. Results showed that although the cocktail vaccine induced stronger cell-mediated immune responses than the vaccine containing only gD plasmid, both vaccines protected pigs equally well against challenge infection. Intradermal inoculation with a needle induced significantly stronger antibody and cell-mediated immune responses and better protection against challenge infection than intramuscular inoculation. Our data show that the route of administering DNA vaccines in pigs is important for an optimal induction of protective immunity.     

Local periocular vaccination protects against eye disease more effectively than systemic vaccination following primary ocular herpes simplex virus infection in rabbits

Vaccination of experimental animals can provide efficient protection against ocular herpes simplex virus type 1 (HSV-1) challenge. Although it is suspected that local immune responses are important in protection against ocular HSV-1 infection, no definitive studies have been done to determine if local ocular vaccination would produce more efficacious protection against HSV-1 ocular challenge than systemic vaccination. To address this question, we vaccinated groups of rabbits either systemically or periocularly with recombinant HSV-2 glycoproteins B (gB2) and D (gD2) in MF59 emulsion or with live KOS (a nonneurovirulent strain of HSV-1). Three weeks after the final vaccination, all eyes were challenged with McKrae (a virulent, eye disease-producing strain of HSV-1). Systemic vaccination with either HSV-1 KOS or gB2/gD2 in MF59 did not provide significant protection against any of the four eye disease parameters measured (conjunctivitis, iritis, epithelial keratitis, and corneal clouding). In contrast, periocular vaccination with gB2/gD2 in MF59 provided significant protection against conjunctivitis and iritis, while ocular vaccination with live HSV-1 KOS provided significant protection against all four parameters. Thus, local ocular vaccination provided better protection than systemic vaccination against eye disease following ocular HSV-1 infection. Since local vaccination should produce a stronger local immune response than systemic vaccination, these results suggest that the local ocular immune response is very important in protecting against eye disease due to primary HSV-1 infection. Thus, for clinical protection against primary HSV-1-induced corneal disease, a local ocular vaccine may prove more effective than systemic vaccination.     

Mechanomyography and oxygen consumption during incremental cycle ergometry

Brucella abortus strain RB51 was recently approved as an official brucellosis calfhood vaccine for cattle by the Animal and Plant Health Inspection Service branch of the United States Department of Agriculture. Currently available serologic surveillance tests for B. abortus do not detect seroconversion following SRB51 vaccination. The purpose of this study was to evaluate a dot-blot assay using gamma-irradiated strain RB51 bacteria for its specificity and sensitivity to detect antibody responses of cattle vaccinated with strain RB51. Dot-blot titers of sera at a recommended dosage (10(10) colony-forming units) were similar to those of sera from cattle vaccinated with similar numbers of B. abortus strain 19 and greater (P < 0.05) than titers of nonvaccinated cattle. In the first 12 weeks after vaccination with 10(10) colony-forming units of strain RB51, the RB51 dot-blot assay had 100% specificity for titers of 80 or less and a 53% sensitivity for titers of 160 or greater. Sensitivity of the RB51 dot-blot assay peaked at 4 weeks after vaccination with 10(10) colony-forming units of strain RB51. Dot-blot responses of sera from cattle vaccinated with a reduced dosage of strain RB51 (10(9) colony-forming units) did not differ (P > 0.05) from titers of sera from nonvaccinated cattle. Following intraconjunctival challenge with B. abortus strain 2308, titers on the RB51 dot-blot assay did not differ (P > 0.05) between nonvaccinated cattle and cattle vaccinated at calfhood with strain 19 or strain RB51.     

Efficacy of intratracheal administration of Newcastle disease vaccine in day-old chicks

Groups of day-old chicks with varying levels of parental antibody were vaccinated against Newcastle disease (B1 strain) with a commercially available device which simultaneously debeaks the chick and emits a fine spray of vaccine into its trachea. Some groups were also vaccinated (B1 or Lasota strain) with a commercially available vaccine sprayer at 9 days, 14 days, or 9 and 25 days of age. Response to vaccine was evaluated once each week during the experimental period of approximately 8 weeks HI titers were determined and 10 chicks were challenged with the Texas GB strain of Newcastle disease virus. In chicks with low to moderate levels of maternal antibody a satisfactory antibody response was attained by vaccination at 1 day of age, and in most cases resistance to challenge was evident by 3 weeks of age. Intratracheal vaccination of chicks with extremely high levels of maternal antibody had a minimal antibody response. All groups of chicks spray vaccinated at 9, 14, or 9 and 25 days of age showed a marked increase in antibody titer regardless of whether they had been vaccinated at 1 day of age.