Inexpensive vaccines and rapid diagnostic kits tailor-made for the global eradication of rinderpest, and technology transfer to Africa and Asia

Rinderpest is an acute and highly contagious viral disease of ruminants, often resulting in greater than 90% mortality. We previously reported the development of first- and second-generation recombinant vaccinia virus vaccines which provide complete protection against rinderpest virus (RPV) and peste-des-petits ruminants virus (PPRV). These vaccines are safe even for immunodeficient mice and macaques with acquired immunodeficiency syndrome. We developed a third-generation recombinant vaccinia virus vaccine (v2RVFH) that expresses the fusion and haemagglutinin genes of RPV under strong synthetic vaccinia virus promoters. Cattle vaccinated intramuscularly with as little as 10(3) plaque-forming units (PFU) of v2RVFH were completely protected from rinderpest. Vaccinated animals did not develop pock lesions or transmit v2RVFH to contact animals. Cattle vaccinated with a standard dose of 10(8) PFU of v2RVFH developed long-term, sterilizing immunity against rinderpest. Thus, v2RVFH is safe, efficacious, heat stable, inexpensive, easily administered, and allows serological differentiation between vaccinated and infected animals. To aid in diagnosis and differentiation of vaccinated from infected animals, we developed indirect ELISAs (iELISAs) that use baculovirus-expressed RPV or PPRV nucleoprotein as coating antigens. A single larva contains enough viral antigen to test more than 10,000 serum samples, in duplicate. African scientists trained at the ILMB successfully transferred the iELISA kit technology to more than 30 countries in Africa, providing a model for technology transfer among developing countries. Vaccination with v2RVFH, in conjunction with the iELISA kits, greatly enhances the prospects for global eradication of rinderpest, as developing nations achieve independence in control efforts.

Enhanced safety and efficacy of live attenuated SIV vaccines by prevaccination with recombinant vaccines

The only vaccines shown to be protective against intravenous challenge with virulent virus in the simian immunodeficiency virus (SIV)/macaque model are attenuated live SIVs. However, these vaccines have several disadvantages: 1) they persist indefinitely in vaccinated macaques; 2) they are pathogenic to neonatal macaques; and 3) they are lethal in some adult macaques. To enhance the safety and efficacy of these vaccines, we immunized macaques first with recombinant vaccines and then inoculated the animals with SIV(delta(nef)). In the first experiment, preimmunized macaques advanced to disease slower than controls after challenge with virulent SIV; five animals survived for 3 years without disease and only the vaccine virus (SIV(delta(nef)) could be isolated at this time. In the second experiment, preimmunized animals had lower virus loads and no disease compared to controls.

Immunization with live attenuated simian immunodeficiency virus induces strong type 1 T helper responses and beta-chemokine production

Immunization with live attenuated simian immunodeficiency virus (SIV) strains has proved to be one of the most effective strategies to induce protective immunity in the SIV/macaque model. To better understand the role that CD4(+) T helper responses may play in mediating protection in this model, we characterized SIV-specific proliferative and cytokine responses in macaques immunized with live attenuated SIV strains. Macaques chronically infected with live attenuated SIV had strong proliferative responses to SIV proteins, with stimulation indices of up to 74. The magnitude of the proliferative response to SIV Gag varied inversely with the degree of attenuation; Gag-specific but not envelope-specific responses were lower in animals infected with more highly attenuated SIV strains. SIV-specific stimulation of lymphocytes from vaccinated macaques resulted in secretion of interferon-gamma, IL-2, regulated-upon-activation, normal T cells expressed and secreted (RANTES), macrophage inflammatory protein (MIP)-1alpha, and MIP-1beta but not IL-4 or IL-10. Intracellular flow cytometric analysis documented that, in macaques vaccinated with SIVmac239Deltanef, up to 2% of all CD4(+)T cells were specific for SIV p55. The ability of live attenuated SIV to induce a strong, sustained type 1 T helper response may play a role in the success of this vaccination approach to generate protection against challenge with wild-type SIV.

Characterization of SIV-specific CD4+ T-helper proliferative responses in macaques immunized with live-attenuated SIV

Analysis of immune responses generated by live-attenuated simian immunodeficiency virus (SIV) strains may provide clues to the mechanisms of protective immunity induced by this approach. We examined SIV-specific T-helper responses in macaques immunized with the live-attenuated SIV strains SIVmac239deltanef and SIVmac239delta3. Optimization of the concentration and duration of antigenic stimulation resulted in the detection of relatively strong SIV-specific proliferative responses, with peak stimulation indices of up to 84. SIV-specific proliferative responses were mediated by CD4+ T cells and were major histocompatibility (MHC) class II restricted. Limiting dilution analysis revealed SIV-specific T-helper precursor frequencies of up to 96 per 10(6) peripheral blood mononuclear cells (PBMC). Intracellular flow-cytometric analysis demonstrated the production of interleukin (IL)-2, interferon (IFN)-gamma, RANTES and macrophage inhibitory protein-1alpha (MIP-1alpha) by T lymphocytes from SIVmac239deltanef-vaccinated animals following SIV p55 stimulation. Induction of strong SIV-specific T-helper responses by live-attenuated SIV vaccines may play a role in their ability to induce protective immunity.

Structural and functional studies of the measles virus hemagglutinin: identification of a novel site required for CD46 interaction

The entry of measles virus (MV) into human cells is mediated by the initial attachment of the viral hemagglutinin (HA) to the complement regulatory protein CD46. Two subdomains, one each within CD46 short consensus repeats (SCRs) 1 and 2, are responsible for this interaction. However, little is known about the regions within MV HA needed for a high-affinity CD46 interaction. To better define the HA-CD46 interaction, we took three approaches: chimeric domain swapping, peptide scanning, and alanine scanning mutagenesis. Chimeras of MV HA and the closely related rinderpest virus (RPV) HA were generated and tested for cell surface expression and the ability to hemadsorb CD46+ red blood cells (RBC). Exchanges with the N terminus of RPV were tolerated as MV HA could be replaced with RPV HA up to amino-acid position 154. However, both larger swaps with RPV and a small RPV HA replacement at the C terminus aborted cell-surface expression. Peptide scanning with 51 overlapping peptides derived from three MV HA regions showed one peptide, corresponding to MV HA amino acids 468-487, blocked hemagglutination of African green monkey (AGM) RBCs and inhibited MV infection of Chinese hamster ovary cells (CHO) expressing human CD46. Alanine scanning mutants mapped sites on the MV HA that were not required for trafficking to the cell surface or function in hemagglutination as well as a novel site required for CD46 interaction, amino acids 473-477.

Detection of antibodies to equine arteritis virus by enzyme linked immunosorbant assays utilizing G(L), M and N proteins expressed from recombinant baculoviruses

Indirect enzyme linked immunosorbant assays (ELISAs) utilizing the three major structural proteins (M, N, and G(L)) of equine arteritis virus (EAV) expressed from recombinant baculoviruses were developed. A large panel of sera collected from uninfected horses, and from animals experimentally and naturally infected with EAV or vaccinated with the modified live virus vaccine against equine viral arteritis, were used to characterize the humoral immune response of horses to the three major EAV structural proteins. The data suggest that the M protein was the major target of the equine antibody response to EAV. The responses of individual animals varied and ELISAs that utilized individual EAV structural proteins were not reliable for detecting antibodies in all sera that contained neutralizing antibodies to EAV. An ELISA based on a cocktail of all three EAV structural proteins, however, was used successfully to detect antibodies in most equine sera that were positive in the standard serum neutralization assay following natural or experimental EAV infection (100% specificity, 92.3% sensitivity). In contrast, this ELISA did not reliably detect antibodies in the sera of vaccinated horses. EAV frequently causes a persistent infection in stallions and all sera from carrier stallions evaluated in this study had obvious reactivity with the N protein, whereas seropositive non-carrier stallions, mares and geldings did not respond consistently to the N protein.

Altered plaque formation by recombinant vaccinia virus expressing simian immunodeficiency virus Nef

The nef gene of primate lentiviruses encodes a myristoylated protein that is important for pathogenicity and the maintenance of high virus loads. A deletion in nef leads to a significant reduction of the pathogenicity of simian immunodeficiency virus (SIV) in macaques. At the cellular and biochemical levels, Nef has been shown to down-regulate CD4 and major histocompatibility complex class I molecules and to interact with cellular protein kinases. The importance of these activities for Nef function remains uncertain. We have prepared vaccinia virus recombinants expressing different alleles of SIV nef. When grown on TK- 143 cells, recombinants constructed with the nef allele from SIVmac1A11 produced typical plaques while recombinants expressing the nef allele from SIVmac239-R1 gave rise to plaques with altered morphology. By using chimeric Nef proteins and site-directed mutagenesis, the amino acid responsible for altered plaque formation was mapped to a leucine at residue 211. In vitro phosphorylation of immunoprecipitates prepared from cells infected with the vaccinia virus recombinants resulted in labeled proteins of 62 and 90 kDa. The recombinants differed in the ability to stimulate phosphorylation, and the leucine at residue 211 was again found to be the determining amino acid. These results might help elucidate the role of nef in the pathogenesis of SIV.

Protective vaccination of ferrets against canine distemper with recombinant pox virus vaccines expressing the H or F genes of rinderpest virus

OBJECTIVE

To investigate the ability of rinderpest virus (RPV) antigens, expressed in pox virus vectors, to protect against canine distemper virus (CDV) infection in ferrets.

ANIMALS

Ferrets (Mustela putorius; n = 27) with no previous exposure to CDV.

PROCEDURE

Ferrets were inoculated intradermally with recombinant vaccinia viruses expressing the H gene of RPV, the F gene of RPV, the H and F genes of RPV, or fowlpox virus recombinant expressing both genes. Two ferrets were vaccinated s.c. with CDV vaccine as positive controls, and 1 group was left unvaccinated as a negative control. Blood was obtained from ferrets biweekly; antibody titer to RPV was detected by ELISA, and CDV antibody titer was measured by serum neutralization testing and ELISA.

RESULTS

Partial protection was seen in all groups, with vRVFH vaccination being the most protective (60%).

CONCLUSIONS AND CLINICAL RELEVANCE

A single inoculation with a vaccinia virus expressing the H and F genes of RPV was able to protect 60% of the vaccinated ferrets challenge exposed with a high dose of CDV. These results indicate the ability of RPV antigens expressed by vaccinia virus to protect ferrets against a related morbillivirus. Further, they document the safety and efficacy of a recombinant vaccinia virus vaccine for ferrets. Such vaccines may be useful given the susceptibility of ferrets to CDV and the problem of maternal antibody interfering with vaccination of young animals.

Expression of gamma interferon by simian immunodeficiency virus increases attenuation and reduces postchallenge virus load in vaccinated rhesus macaques

Simian immunodeficiency virus (SIV) infection of macaques is a model for human immunodeficiency virus (HIV) infection. We have previously reported the construction and characterization of an SIV vector with a deletion in the nef gene (SIV(delta nef)) and expressing gamma interferon (SIV(HyIFN)) (L. Giavedoni and T. Yilma, J. Virol. 70:2247-2251, 1996). We now show that rhesus macaques vaccinated with SIV(HyIFN) have a lower viral load than a group similarly immunized with SIV(delta nef). Viral loads remained low in the SIV(HyIFN)-vaccinated group even though SIV expressing gamma interferon could not be isolated after 6 weeks postimmunization in these animals. All immunized and two naive control macaques became infected when challenged with virulent SIV(mac251), at 25 weeks postvaccination. In contrast to the two naive controls that died by 12 and 18 weeks postchallenge, all vaccinated animals remained healthy for more than 32 weeks. In addition, postchallenge cell-associated virus load was significantly lower in SIV(HyIFN)-immunized animals than in the group vaccinated with SIV(delta nef). These findings indicate that cytokine-expressing viruses can provide a novel approach for development of safe and efficacious live attenuated vaccines for AIDS.

Phylogenetic comparison of the S3 gene of United States prototype strains of bluetongue virus with that of field isolates from California

To better define the molecular epidemiology of bluetongue virus (BTV) infection, the genetic characteristics and phylogenetic relationships of the S3 genes of the five U.S. prototype strains of BTV, the commercially available serotype 10 modified live virus vaccine, and 18 field isolates of BTV serotypes 10, 11, 13, and 17 obtained in California during 1980, 1981, 1989, and 1990 were determined. With the exception of the S3 gene of the U.S. prototype strain of BTV serotype 2 (BTV 2), these viruses had an overall sequence homology of between 95 and 100%. Phylogenetic analyses segregated the prototype U.S. BTV 2 strain to a unique branch (100% bootstrap value), whereas the rest of the viruses clustered in two main monophyletic groups that were not correlated with their serotype, year of isolation, or geographical origin. The lack of consistent association between S3 gene sequence and virus serotype likely is a consequence of reassortment of BTV gene segments during natural mixed infections of vertebrate and invertebrate hosts. The prototype strain of BTV 13, which is considered an introduction to the U.S. like BTV 2, presents an S3 gene which is highly homologous to those of some isolates of BTV 10 and especially to that of the vaccine strain. This finding strongly suggests that the U.S. prototype strain of BTV 13 is a natural reassortant. The different topologies of the phylogenetic trees of the L2 and S3 genes of the various viruses indicate that these two genome segments evolve independently. We conclude that the S3 gene segment of populations of BTV in California is formed by different consensus sequences which cocirculate and which cannot be grouped by serotype.

Strong cytotoxic T cell and weak neutralizing antibody responses in a subset of persons with stable nonprogressing HIV type 1 infection

Some individuals in well-defined cohorts have now been infected with HIV-1 for well over a decade and yet remain clinically asymptomatic with normal CD4 counts. To determine immunologic and virologic parameters in these individuals, we examined 10 persons from the San Francisco City Clinic with firmly documented infection of 11-15 years duration who had maintained stable CD4 counts above 500 cells/microliters. Our results indicate that long-term nonprogressors are a heterogeneous group with respect to viral load and HIV-1-specific immune responses, and that progression can occur even after 15 years of stable infection. However, in a subset of persons with the lowest viral loads and persistent nonprogressive infection, we detected strong CTL responses, whereas neutralizing antibody studies revealed weak to undetectable titers against a panel of 10 primary isolates. This study demonstrates that a vigorous in vivo activated HIV-1-specific CTL response can be part of the host immune response in stable nonprogressive HIV-1 infection, and that circulating activated CTL can be detected in the setting of an extremely low viral load. These results also indicate that long-term nonprogressing HIV-1 infection does not require the presence of broadly cross-reactive neutralizing antibodies.

Construction and characterization of replication-competent simian immunodeficiency virus vectors that express gamma interferon

We report the construction and characterization of several replication-competent simian immunodeficiency virus (SIV) vectors with a deletion in the viral nef gene (SIV(delta nef)) that express gamma interferon (IFN-gamma). The expression of the cytokine gene was controlled either by the simian virus 40 early promoter or by the SIV 5' long terminal repeat regulatory sequences, utilizing the nef gene splice signals. To enhance the expression of IFN-gamma, the two in-frame nef start codons were mutated without altering the Env amino acid sequence (SIV(HyIFN)). Plasmids containing full-length proviral genomes were used to obtain high-titer stocks of each recombinant virus in cell cultures. Expression of IFN-gamma by SIV(HyIFN) reached levels as high as 10(6) U/ml after 11 days in culture. The IFN-gamma gene was unstable and sustained deletions after serial passage of SIV(delta nef) vectors in CEM-X-174 cells. The degree of instability appears to depend on size and orientation of the insert and the expression of IFN-gamma. Only one virus, SIV(HyIFN), expressed detectable levels of IFN-gamma up to the sixth passage. Prospects for the use of IFN-gamma and other lymphokines to enhance the safety and efficacy of live attenuated vaccines are discussed.

Cloning and expression of the nucleoprotein of peste des petits ruminants virus in baculovirus for use in serological diagnosis

Peste des petits ruminants (PPR) is a viral disease of goats and sheep characterized by erosive stomatitis, enteritis, and pneumonia. The virus is a member of the family Paramyxoviridae and the genus Morbillivirus. The disease has high morbidity and mortality rates and has a substantial economic impact in developing countries. We have cloned and sequenced the cDNA of the nucleocapsid (N) gene of the Nigeria 75/1 strain of PPR virus (PPRV). A comparison of its nucleotide and deduced amino acid sequence with those of the N gene of the tissue culture-attenuated strain of PPRV was performed. A divergence of 8.9 and 5.0% was found at the nucleotide and amino acid level, respectively. A recombinant baculovirus that expresses the N protein in insect cells and larvae (Spodoptera frugiperda) was generated. The recombinant protein, characterized by Western blot analysis, was shown to have a molecular weight of 58 kDa and was recognized by anti-PPRV antibodies. The recombinant protein was used successfully as a coating antigen in an enzyme-linked immunosorbent assay for the serological diagnosis of PPRV.

Antibodies to the putative SIV infection-enhancing domain diminish beneficial effects of an SIV gp160 vaccine in rhesus macaques

OBJECTIVE

To demonstrate that antibodies against amino acids (aa) 603-622 of the SIV gp41 transmembrane glycoprotein enhance infection of SIV in vivo.

DESIGN

A synthetic peptide derived from aa 603-622 of SIVmac251 gp41 was synthesized and tested for immunogenicity in rabbits and SIV-infected rhesus macaques. Next, SIV-naive animals were immunized with either a recombinant vaccinia virus expressing the SIV gp160 envelope glycoprotein (VVrgp160) and boosted three times with aa 603-622 (group 1, four animals), wild-type vaccinia virus and boosted with aa 603-622 (group 2, two animals), or VVrgp160 followed by three doses of an irrelevant peptide (group 3, two animals). Animals were challenged with SIVmac251.

RESULTS

Peptide aa 603-622 was immunogenic in rabbits. SIV-infected rhesus monkeys immunized with the peptide developed two-three log increases in antibodies to this peptide and antibodies that could enhance SIV infection in vitro. SIV-naive rhesus macaques in group 1 had higher levels of antibody to the peptide by enzyme-linked immunosorbent assay and higher levels of enhancing antibodies at the time of SIV challenge than the animals in groups 2 or 3. Following challenge with SIVmac251 the group 1 animals had detectable p27 antigen longer than animals in group 2 and 3 and died of simian AIDS before the respective animals in the two control groups (P < 0.05 by log-rank test).

CONCLUSIONS

aa 603-622 of SIV gp41, like aa 579-613 of HIV gp41, can stimulate production of antibodies that enhance SIV and HIV infection in vitro. Furthermore, immunization with this peptide suppressed beneficial effects of a gp160 vaccine and appeared to enhance SIV infection in vivo.

Reduced virus load in rhesus macaques immunized with recombinant gp160 and challenged with simian immunodeficiency virus

As a safe alternative to inactivated and live-attenuated whole-virus SIV vaccines, we have evaluated the potential of SIVmac239 gp160 expressed by recombinant vaccinia virus (vSIVgp160) and baculovirus (bSIVgp160) to protectively immunize rhesus macaques against intravenous (i.v.) infection with pathogenic SIVmac isolates. Macaques were immunized with live vSIVgp160 and/or bSIVgp160 protein partially purified from insect cells. The challenge viruses, propagated in rhesus peripheral blood mononuclear cells, consisted of the molecular clone SIVmac239 and another genetically similar, uncloned isolate, SIVmac251. Although antibodies that bind gp130 were induced in all animals following immunization with SIVgp160, neutralizing antibodies were undetectable 1 week prior to virus challenge. These results differ from those for macaques vaccinated with inactivated, whole SIV. All animals became infected after i.v. inoculation with 1-10 AID50 of either challenge virus. For animals challenged with SIVmac251, but not those challenged with SIVmac239, the cell-free infectious virus load in plasma of vSIVgp160-primed, bSIVgp160-boosted macaques was significantly lower than in unimmunized controls at 2 weeks postchallenge. Virus virulence, immunization regimen, and challenge with homologous or heterologous virus are factors critical to the outcome of the study. Immunization with surface glycoprotein may not necessarily provide protective immunity against infection but may reduce virus load. The relationship between reduction in virus load by vaccination and delay in onset of disease remains to be determined.

Cloning and expression of the nucleocapsid gene of virulent Kabete O strain of rinderpest virus in baculovirus: use in differential diagnosis between vaccinated and infected animals

Rinderpest (RP) is a viral disease of ruminants with > 95% morbidity and mortality. We have cloned the cDNA of the nucleocapsid (N) gene of the virulent Kabete O strain of rinderpest virus (RPVK) and compared its nucleotide and deduced amino acid sequences with those of the N genes of the lapinized strain of rinderpest virus (RPVL), measles virus (MV), and canine distemper virus (CDV). The gene has an open reading frame of 1575 nucleotides and encodes a protein of 525 amino acids with a molecular weight of 59 kDa. The nucleotide sequence of the coding region of the N gene of RPVK is 88.6, 68.9, and 63.2% homologous with N genes of RPVL, MV, and CDV, respectively. We have developed a recombinant baculovirus that expresses the N protein (rRVN) of RPVK in insect cells (Sf9) and larvae (Spodoptera frugiperda). rRVN was used as a coating antigen in an ELISA to distinguish vaccinated animals from those infected with RPV and was also used successfully in the diagnosis of two other morbilliviruses, MV and peste des petits ruminants (PPRV). Crude lysate of a single infected larva (0.2-0.3 g) was sufficient to coat 150 ELISA plates for serological diagnosis of 7200 serum samples in duplicate.

Immunological responses of mice and cattle to baculovirus-expressed F and H proteins of rinderpest virus: lack of protection in the presence of neutralizing antibody

Rinderpest is a highly contagious viral disease of ruminants and has greater than 95% morbidity and mortality. The etiological agent, rinderpest virus (RPV), is a member of the family Paramyxoviridae and the genus Morbillivirus. Immune responses to both the hemagglutinin (H) and the fusion (F) antigens of morbilliviruses play an important role in the prevention of infection, and only attenuated live vaccines have been shown to provide protective immunity against the group. The lack of protection with inactivated vaccines has been attributed to the denaturation of the F glycoprotein of the virus. Our previous study, however, demonstrated complete protection of cattle vaccinated with infectious vaccinia virus recombinants expressing the H (vRVH) or F (vRVF) protein alone, even in the presence of only 4 U of serum-neutralizing (SN) antibody to RPV (T. Yilma, D. Hsu, L. Jones, S. Owens, M. Grubman, C. Mebus, M. Yamanaka, and B. Dale, Science 242:1058-1061, 1988). We have constructed recombinant baculoviruses that express the F (Fb) and H (Hb) glycoproteins of RPV. Furthermore, we have analyzed the immune responses of mice and cattle to these antigens. Cattle vaccinated with Fb or Hb or a mixture of both antigens were not protected from challenge inoculation with RPV, even when the SN titer was greater than in cattle vaccinated with vRVF alone. This lack of protection, in the presence of SN antibody, would indicate that live attenuated and recombinant vaccines induce immune responses necessary for protection (e.g., cell-mediated immunity) that are not generated by subunit or inactivated whole-virus vaccines.

Immunological characterization of the VSV nucleocapsid (N) protein expressed by recombinant baculovirus in Spodoptera exigua larva: use in differential diagnosis between vaccinated and infected animals

Vesicular stomatitis is a viral disease of cattle, pigs, and horses. The disease is characterized by vesicular lesions on the epithelium of the mouth, feet, and teats. The pathological lesions are virtually indistinguishable from that of foot-and-mouth disease. We have developed a recombinant baculovirus that expresses the nucleocapsid (N) protein of the New Jersey serotype of vesicular stomatitis virus (VSVNJ) in insect cells (Sf9) and larvae (Spodoptera exigua). The gene was expressed under control of the polyhedrin promoter as a fusion or nonfusion protein. The recombinant N protein expressed in insect cells could not be distinguished from N protein produced in VSVNJ-infected CHO cells by immunological and biochemical analyses. The level of expression of N as a percentage of the total protein in Sf9 cells was 41% for the fusion and 60% for the nonfusion protein. Higher level (68%) of expression of the nonfusion N protein was obtained in larvae. Recombinant N protein was used in an ELISA to distinguish animals vaccinated with a recombinant VSV glycoprotein from those exposed to the whole virus by infection or classical vaccine. Lysate of a single infected larva (0.2-0.3 g) was adequate for coating ELISA plates to perform 10,000 serum assays in duplicate.

Protection of goats against peste des petits ruminants with a vaccinia virus double recombinant expressing the F and H genes of rinderpest virus

Peste des petits ruminants (PPR) is a viral disease of goats and sheep characterized by necrotizing and erosive stomatitis, enteritis and pneumonia. The causative agent, PPRV, is a member of the family Paramyxoviridae and the genus Morbillivirus. Other members of the genus include rinderpest (RPV), measles, canine distemper and phocid distemper viruses. PPR has a very high rate of morbidity and mortality, and effective control of this disease is of economic importance in Africa, Asia and the Middle East. Currently, there is no safe and effective vaccine available against the disease. The tissue culture rinderpest vaccine (TCRV) protects small ruminants against severe disease; there are, however, clinical problems associated with vaccination. This laboratory has recently developed several effective vaccinia virus recombinant vaccines for rinderpest. These vaccines are easy to administer, inexpensive to produce and heat-stable. Goats were vaccinated with a vaccinia virus double recombinant expressing the haemagglutinin and fusion genes of RPV. Although vaccinated animals developed antibodies (neutralizing and ELISA) to RPV, and not to PPRV, they were completely protected against challenge inoculation with virulent PPRV. This would indicate that protection is most probably due to cell-mediated immunity. Use of the rinderpest double recombinant vaccinia virus in areas of the world where PPRV is endemic would aid in the control and eradication of PPR.

Sequence analysis and editing of the phosphoprotein (P) gene of rinderpest virus

We have cloned the cDNA of the phosphoprotein (P) gene of the virulent (Kabete "O") strain of rinderpest virus and provided a comparative analysis of its sequence with that of the P genes of measles, canine distemper, and phocid distemper viruses. The gene encodes two overlapping open reading frames of 1521 and 531 nucleotides. Use of the first ATG would produce a P polypeptide of 507 amino acids with a calculated molecular weight of 54,344. The second ATG would produce a C polypeptide of 177 residues with a predicted molecular weight of 19,927. In addition, the insertion of a G residue at position 740 generates an alternative mRNA potentially encoding the V polypeptide of rinderpest virus. The homology comparisons in P amino acid sequences between rinderpest and measles, between rinderpest and canine distemper, and between rinderpest and phocid distemper viruses are 60, 44, and 46%, respectively. A four-way comparison shows an identity of 34%. Similar homology comparisons with the C amino acid sequence between rinderpest and measles, rinderpest and canine distemper, and rinderpest and phocid distemper viruses are 56, 42, and 40%, respectively. A homology of 31% is found in a four-way comparison for the C polypeptide. From the point of the insertion of the G residue, there is a homology of 78% between the V polypeptides of rinderpest and measle viruses.

Vaccinia virus recombinants expressing chimeric proteins of human immunodeficiency virus and gamma interferon are attenuated for nude mice

We have developed a method for attenuating vaccinia virus recombinants by expressing a fusion protein of a lymphokine and an immunogen. Chimeric genes were constructed that coded for gamma interferon (IFN-gamma) and structural proteins of the human immunodeficiency virus type 1 (HIV-1). In this study, we describe the biological and immunological properties of vaccinia virus recombinants expressing chimeric genes of murine or human IFN-gamma with glycoprotein gp120, gag, and a fragment of gp41. All fusion proteins retained the antigenic characteristics of both IFN-gamma and HIV as shown by immunoblot analysis. However, the antiviral activity of IFN-gamma could be demonstrated only for the IFN-gamma-gag fusion protein. In contrast, the attenuating activity of IFN-gamma for nude mice was retained by all of the recombinants, albeit at various rates. Unlike the antiviral activity, the attenuating activity of IFN-gamma was not species specific. Implications for the development of attenuated live recombinant vaccines for AIDS are discussed.

Characterization of group specific antibodies in primates: studies with SIV envelope in macaques

Sera from SIV-infected macaques were found to contain antibodies that reacted with conformation-dependent, group-specific determinants on the SIV envelope protein gp130. These conformation-dependent antibodies exhibited virus neutralizing activity; their presence was associated with protection in vaccine studies. The properties of these antibodies are quite similar to those that have been identified in sera from HIV-infected human subjects. These data suggest that the SIV envelope gp130 remains a candidate for subunit vaccine studies.

A vaccinia virus double recombinant expressing the F and H genes of rinderpest virus protects cattle against rinderpest and causes no pock lesions

Rinderpest is a highly contagious viral disease of ruminants with greater than 95% morbidity and mortality. We have constructed an infectious vaccinia virus recombinant that expresses both the fusion (F) gene and the hemagglutinin (H) gene of rinderpest virus. The Wyeth strain of vaccinia virus was used for the construction of the recombinant. Cattle vaccinated with the recombinant virus were 100% protected from challenge inoculation with greater than 1000 times the lethal dose of rinderpest virus. No transmission of recombinant vaccinia virus from vaccinated animals to contact animals was observed. The lyophilized form of vaccinia virus is thermostable and allows circumvention of the logistical problems associated with the distribution and administration of vaccines in the arid and hot regions of Asia and Africa. The insertional inactivation of both the thymidine kinase and the hemagglutinin genes of vaccinia virus led to increased attenuation of the virus; this was manifested by the lack of detectable pock lesions in vaccinated animals. This approach may have wide application in the development of safe and efficacious recombinant vaccines for humans and animals. This becomes quite relevant with the concern of the use of vaccinia virus in a population with high incidence of the human immunodeficiency virus.

Propagation of recombinant vaccinia virus in HeLa cells: adsorption kinetics and replication in batch cultures

The influence of various culture parameters on infection and replication of recombinant vaccinia virus in HeLa cells was examined during various phases of viral replication. A modified form of the model of Valentine and Allison (Biochim. Biophys. Acta 1960, 40, 393-399) model was used to predict successfully the viral adsorption rates in cell suspensions. An experimentally determined aggregation factor, epsilon, was included in the model to account for deviations of the observed adsorption rates from those predicted by the earlier model. It was also shown that the ionic strength, ionic species, and serum proteins present in the medium significantly altered the adsorption kinetics of the virus. The lysosomotropic base chloroquine was found to enhance viral infection more than 2-fold during the penetration step of viral infection. It was also demonstrated that cells infected during the exponential growth phase gave higher viral yields than those infected during the lag or stationary growth phases and the initial viral MOI did not significantly alter viral yields. Finally, it was demonstrated that viral infection of HeLa cells grown in 4-L bioreactor batch cultures resulted in increased death and glucose uptake rates and significantly lower growth rates.

Molecular cloning of the rinderpest virus matrix gene: comparative sequence analysis with other paramyxoviruses

The nucleotide sequence of the gene encoding the matrix or membrane (M) protein of the virulent (Kabete-O) strain of rinderpest virus (RPV) has been determined. The M gene is 1457 nucleotides long with a single, large open reading frame. The derived polypeptide has 335 amino acids, corresponding to a calculated molecular weight of 38,289 and contains both small hydrophobic regions and many basic residues. The predicted amino acid sequence was compared to the M proteins of paramyxoviruses. Sequence comparison and hydropathy profiles among the morbilliviruses revealed that the M protein of RPV exhibits features similar to those of the M protein of MV and CDV. There is 78.2% homology at the amino acid level between the M protein of RPV and MV, and 77.6% between RPV and CDV. This indicates that a high degree of homology exists among the members of the genus Morbillivirus. In contrast, there is only 37.3 and 18% homology between RPV and bovine parainfluenza type 3 (BPV3), and RPV and Newcastle disease virus (NDV) M proteins, respectively. Thus the M proteins of the morbilliviruses are highly conserved whereas the M proteins of the genus Paramyxovirus show more divergence.

The effect of interferon-gamma intramammary administration on mammary phagocyte function

The effect of recombinant bovine interferon-gamma on intramammary phagocyte function of mammary gland was studied in 4 Holstein cows (Study 1) and 7 Holstein cows (Study 2). Recombinant bovine interferon-gamma was intramammarily infused on day 6 of the dry period and phagocytes were collected from lacteal secretions and tested in vitro 24 hours later. Results from Study 1 indicate that phagocytosis of Escherichia coli and Staphylococcus aureus was significantly increased after than before interferon treatment. Similarly, the number of bacteria killed/active phagocyte was enhanced by treatment. Results from Study 2 suggested a trend towards increased production of oxygen dependent bactericidal components and increased killing ability by phagocytes exposed to interferon as compared to control phagocytes. These results from both studies suggest that intramammary infusions of bovine interferon-gamma can stimulate phagocyte function during the early phase of the dry period.

Enhancement of primary and secondary immune responses by interferon-gamma

We have investigated the effects of interferon-gamma (IFN-gamma) administered with "G" glycoprotein of vesicular stomatitis virus (VSV), on the neutralizing antibody response. Treatment of mice or cattle with recombinant DNA-derived IFN-gamma at the time of primary immunization with "G" glycoprotein enhanced the secondary virus-neutralizing antibody response that followed a booster administration of the same antigen without IFN-gamma treatment. Enhancement was statistically significant, and occurred at relatively low doses of IFN-gamma in the absence of any additional adjuvants. Cattle treated with IFN-gamma at the time of primary immunization were also more resistant to VSV challenge than those immunized without IFN-gamma treatment. Such treatment in conjunction with primary immunization may therefore provide a practical means of enhancing protection from viral challenge without inflammatory adjuvants or boosters.

Protection of cattle against rinderpest with vaccinia virus recombinants expressing the HA or F gene

Rinderpest is a highly contagious ruminant viral disease manifested by a rapid course and greater than 90% mortality. Infectious vaccinia virus recombinants were constructed that express either the hemagglutinin or the fusion gene of rinderpest virus. All cattle vaccinated with either recombinant or with the combined recombinants produced neutralizing antibodies against rinderpest virus and were protected against the disease when challenged with more than 1000 times the lethal dose of the virus.

Cloning of the fusion gene of rinderpest virus: comparative sequence analysis with other morbilliviruses

We have cloned the cDNA of the fusion (F) gene of the virulent (Kabete O) strain of rinderpest virus and provided a comparative analysis of its sequence with that of the F genes of measles and distemper viruses. The gene has an open reading frame of 2241 nucleotides with two potential initiation codons in-frame. Use of the first ATG would produce a polypeptide 747 amino acids long with a calculated molecular weight of 81,068. However, we suggest that the second ATG is used to generate the Fo protein, which is 546 amino acids long with a calculated molecular weight of 58,754. During maturation, the cleavage of F0 gives rise to the functional F1 and F2 polypeptides. The F1 polypeptide is 438 amino acids long and has a calculated molecular weight of 46,791, with a single (potential) glycosylation site in its cytoplasmic domain. The F2 polypeptide, probably 89 amino acids long after the signal sequence is cleaved, is estimated to be 9,800 Da and has three potential glycosylation sites. There is a divergence of 18.7% in amino acid sequences between rinderpest and measles virus F0 polypeptides; between distemper and rinderpest viruses the divergence is 31.8%. No significant homology in nucleotide sequences of rinderpest DNA to measles or distemper DNA was found in the 5' and 3' untranslated regions.

Cloning and sequence analysis of the hemagglutinin gene of the virulent strain of rinderpest virus

We have cloned the cDNA of the hemagglutinin (HA) gene of the virulent (Kabete O) strain of rinderpest virus and produced a comparative analysis of its sequence with that of the HA genes of rinderpest (lapinized strain) and measles viruses. The gene has an open reading frame of 1827 nucleotides, and the derived protein is 609 amino acids long with a calculated molecular weight of 68,006. The Kabete O HA polypeptide is identical in length to the HA of the lapinized strain of rinderpest virus and has a similar hydropathy profile. The nucleotide divergence between the lapinized and the Kabete O HA genes is 11.4% within the coding region, and 34.3% in the 3' untranslated region. The two rinderpest HA polypeptides differ at 74 amino acid residues for a divergence of 12.2%. Three-way comparison of the two rinderpest HA molecules with the measles virus HA polypeptide indicates that 56.6% of the residues are conserved.

Identification of a neutralizing epitope shared by bluetongue virus serotypes 2 and 13

The serotypes of bluetongue virus (BTV) are classified by differences in neutralization commonly induced by P2, a major surface protein. A BTV serotype 13 (BTV-13) monoclonal antibody, 4B13-207A, immunoprecipitated P2s of BTV-13 and BTV-2 and also neutralized both viruses. These data indicate that P2s from BTV-13 and BTV-2 share a common neutralizing epitope that is not detected by neutralizing polyclonal antibody to BTV-13.

Enhancement of a secondary antibody response to vesicular stomatitis virus "G" protein by IFN-gamma treatment at primary immunization

IFN-gamma is a secreted polypeptide product of stimulated T lymphocytes with immunomodulatory properties as well as antiviral activity. We have investigated the effects of IFN-gamma treatment on a neutralizing antibody response to vesicular stomatitis virus (VSV) when administered in conjunction with immunization using purified envelope glycoprotein "G" of VSV. Administration of rIFN-gamma to mice or cattle at the time of primary immunization with VSV G glycoprotein enhanced the magnitude of a secondary virus-neutralizing antibody response after a booster administration of the same Ag without IFN-gamma treatment. Enhancement was statistically significant and occurred at relatively low doses of IFN-gamma in the absence of any additional adjuvants. Furthermore, cattle treated with IFN-gamma at the time of a single primary immunization were more resistant to VSV challenge than those immunized without IFN-gamma treatment. IFN-gamma treatment in conjunction with a single primary immunization may therefore provide a practical means of enhancing protection from a viral challenge without the use of inflammatory adjuvants or booster immunizations.

Enhancement of a secondary antibody response to vesicular stomatitis virus "G" protein by IFN-gamma treatment at primary immunization

IFN-gamma is a secreted polypeptide product of stimulated T lymphocytes with immunomodulatory properties as well as antiviral activity. We have investigated the effects of IFN-gamma treatment on a neutralizing antibody response to vesicular stomatitis virus (VSV) when administered in conjunction with immunization using purified envelope glycoprotein "G" of VSV. Administration of rIFN-gamma to mice or cattle at the time of primary immunization with VSV G glycoprotein enhanced the magnitude of a secondary virus-neutralizing antibody response after a booster administration of the same Ag without IFN-gamma treatment. Enhancement was statistically significant and occurred at relatively low doses of IFN-gamma in the absence of any additional adjuvants. Furthermore, cattle treated with IFN-gamma at the time of a single primary immunization were more resistant to VSV challenge than those immunized without IFN-gamma treatment. IFN-gamma treatment in conjunction with a single primary immunization may therefore provide a practical means of enhancing protection from a viral challenge without the use of inflammatory adjuvants or booster immunizations.

Analysis of the polypeptides synthesized in rinderpest virus-infected cells

We have identified, by [35S]methionine labeling, eight major induced proteins and a number of minor proteins in rinderpest virus-infected bovine kidney cells. The polypeptides ranged in molecular weight from 212 to 21.5 kDa. The majority of these polypeptides are virus specific, as demonstrated by immunoprecipitation with rabbit hyperimmune serum against rinderpest. Infected cells radiolabeled with glucosamine contained a 75-kDa polypeptide and a broad band migrating at 80 kDa, both identified as virus specific by immunoprecipitation. Phosphorylated virus-specific proteins of 65 kDa and a complex of polypeptides at 92.5 kDa were also identified. Monospecific and monoclonal antibodies against measles virus and canine distemper virus hemagglutinin, fusion protein, nucleocapsid protein, and phosphoproteins confirmed the identity of the corresponding rinderpest virus-specific polypeptides.

High levels of interferon in synovial fluid of retrovirus-infected goats

A high level of interferon (IFN) was found in the synovial fluid of goats with naturally acquired caprine arthritis-encephalitis (CAE), a disease caused by caprine arthritis-encephalitis virus (CAEV), a nononcogenic retrovirus of the lentivirus group. Intraarticular injection of CAEV or control inoculum in the joints of affected goats caused increased amounts of IFN production in synovial fluid.

A novel approach for the production of monoclonal antibodies using infectious vaccinia virus recombinants

We describe a novel approach of producing monoclonal antibodies (MABs) to one specific protein of a virus or other agent consisting of several proteins, without the use of purified antigen in either the immunization or screening phase of the procedure. This method has general application in the production of MABs when the antigen cannot be obtained in a pure form, but the gene is available. We illustrate this application by producing MAB specific to the nucleocapsid protein (N) of vesicular stomatitis virus serotype Indiana (VSV-IN) from BALB/c mice immunized with an infectious vaccinia virus recombinant vector (v38) that expresses the N gene of VSV-IN. This novel method of immunization obviates the need for initial purification of the protein antigen and injection of adjuvants with the isolated protein as is done in traditional MAB production.

An enzyme-linked immunosorbent assay for the detection of bovine antibodies to vesicular stomatitis virus

An indirect enzyme-linked immunosorbent assay (ELISA) was developed to detect bovine antibody to vesicular stomatitis virus (VSV). Serum samples from cows experimentally infected with the New Jersey serotype of VSV (VSV-NJ) were assayed by the ELISA and serum-neutralization (SN) assay. The ELISA was as sensitive as the SN assay in detecting bovine antibody to VSV. The correlation between SN titers and ELISA values at absorbance at 405 nm was statistically significant. The ELISA was not specific for VSV-NJ, however, and could detect serum samples positive to the Indiana serotype of VSV that had SN titers of greater than or equal to 480. Nonspecific reactions were due to cross-reactive group-specific viral proteins that are shared by both serotypes. The cross-reactivity allows the use of a single rapid test in identifying both serotypes of VSV from the other exotic vesicular diseases, especially foot-and-mouth disease. The ELISA titers of serum samples positive for VSV-NJ were comparable with the corresponding SN titers of each sample. The sensitivity, rapidity, and ease of the ELISA system and the use of a single test in identifying both serotypes of VSV from the other exotic vesicular diseases make this ELISA suitable as a rapid diagnostic assay for VS.

Characterization of virulent isolates of vesicular stomatitis virus in relation to interference by defective particles

To investigate the role that defective interfering (DI) particles might conceivably play in the epizootiology of vesicular stomatitis, two virulent New Jersey (NJ) isolates from the 1982-1983 epizootic in the United States (US) were compared with three laboratory adapted strains of vesicular stomatitis virus (VSV): NJ Hazelhurst, NJ Ogden and Indiana San Juan. Successive undiluted passages showed that the virulent isolates did not readily exhibit 'autointerference' because they did not readily generate and amplify DI particles. Viral RNA synthesis of isolates that were exposed to homotypic or heterotypic DI particles generated from the laboratory strains showed that the isolates were totally resistant to the heterotypic DI particle and partially resistant to the homotypic DI particle. In contrast, Indiana San Juan and NJ Ogden were inhibited by hetero- or homotypic DI particles. NJ Hazelhurst more closely resembled the isolates. This demonstrates that virulence of VSV in its natural setting may be related to a number of factors, including the slower generation and amplification of endogenous DI particles, as well as the increased resistance of the virus to some pre-existing DI particles.

Preliminary characterization of a serum viral inhibitor in goats

A serum viral inhibitor (SVI) was isolated from goats and partially characterized. The inhibitor prevented the cytopathic effects of vesicular stomatitis virus, encephalomyocarditis virus, and a caprine herpesvirus, indicating broad antiviral activity. The SVI was distinct from interferon because SVI did not induce an antiviral state in cells (ie, lack of protection of SVI-treated cells from virus challenge). The SVI had activity on heterologous cells, including human, bovine, and ovine cells. The lack of antiviral activity in mouse cells indicated that SVI was not an antibody. Like fibroblast interferon, however, SVI was sensitive to trypsin, was acid stable at pH 2 and 4 C for 4 days, was heat stable at 56 C for 1 hour, and could not be sedimented by centrifugation at 100,000 X g for 4 hours.

Vaccinia virus recombinants: expression of VSV genes and protective immunization of mice and cattle

Vesicular stomatitis virus (VSV) causes a contagious disease of horses, cattle, and pigs. When DNA copies of messenger RNA's for the G or N proteins of VSV were linked to a vaccinia virus promoter and inserted into the vaccinia genome, the recombinants retained infectivity and synthesized VSV polypeptides. After intradermal vaccination with live recombinant virus expressing the G protein, mice produced VSV-neutralizing antibodies and were protected against lethal encephalitis upon intravenous challenge with VSV. In cattle, the degree of protection against intradermalingually injected VSV was correlated with the level of neutralizing antibody produced following vaccination.

Immune responses of cattle and mice to the G glycoprotein of vesicular stomatitis virus

A subunit vaccine for vesicular stomatitis was developed from a purified vesicular stomatitis virus preparation by selectively removing the immunogenic G glycoprotein of the virus with the dialyzable, nonionic detergent, beta-D-octylglucoside. Cattle immunized intramuscularly with a single dose of 112 micrograms of G glycoprotein preparation in complete Freund's adjuvant did not develop vesicular disease following challenge by intralingual inoculation of 400 times the infectious dose of the virus. Similarly, mice vaccinated subcutaneously with a single dose of 10 micrograms of G glycoprotein preparation, with or without complete Freund's adjuvant, were protected from lethal encephalitis caused by vesicular stomatitis virus. A subunit vaccine for vesicular stomatitis of cattle, horses, and swine avoids the hazards associated with attenuated and inactivated vaccines, such as vaccine breaks, reversion to virulence, or introduction of virus into potential wild reservoirs or arthropod hosts. Further, it is possible to distinguish serologically animals vaccinated with the subunit preparation from those that have had the clinical disease or that have been vaccinated with whole virus. This is an essential consideration both for epidemiological studies and for disease control or establishment of quarantine programs.