Recovery and characterization of a chimeric rinderpest virus with the glycoproteins of peste-des-petits-ruminants virus: homologous F and H proteins are required for virus viability

Rinderpest (RP) and peste-des-petits-ruminants (PPR) are two important diseases of domestic ruminants. To improve on currently available vaccines against PPR, we have created cDNA copies of the RP virus genome in which either the fusion (F) or hemagglutinin (H) gene, or both, was replaced with the corresponding gene from PPR virus. It was necessary to develop a modified rescue system in which the T7 RNA polymerase was provided by a recombinant fowlpox virus and the entire rescue procedure took place in Vero cells before we could obtain live virus from these chimeric constructs. No virus was recovered when only one of the glycoprotein genes was changed, but a chimeric virus containing both F and H genes from PPR virus was reproducibly rescued from cDNA, indicating that a virus-specific functional interaction takes place between the F and H proteins. The rescued virus expressing the PPR glycoproteins grew more slowly in tissue culture than either parental virus and formed abnormally large syncytia. Goats infected with the chimera showed no adverse reaction, as assessed by clinical signs, temperature, leukocyte count, virus isolation, and serology, and were protected from subsequent challenge with wild-type PPR virus.

Rinderpest virus infection in primary bovine skin fibroblasts

Rinderpest virus (RPV) replicated to a high titre in primary bovine skin fibroblasts. The course of infection was similar to that seen in established cell lines. Virulent field virus grew at a faster rate than the fully attenuated vaccine strain of the virus. Virus antigen expression, as measured by FACScan analysis, correlated with the time course of infection for the two strains in cell cultures. Wild type virus, obtained directly from cattle, infected cells at a slower rate than virus passaged even once in primary bovine skin fibroblasts. This is the first report of a productive infection of primary bovine skin fibroblasts by wild type RPV.

Improved technique for transient expression and negative strand virus rescue using fowlpox T7 recombinant virus in mammalian cells

The suitability of recombinant T7 polymerase produced using either the highly attenuated MVA strain of vaccinia (MVA-T7) or fowlpox virus (FP-T7) for transient expression and negative strand virus rescue was compared in two mammalian cell lines (MDBK and Vero) and in primary cells of bovine, ovine and caprine origin. Such primary cells are more permissive for the growth of wild type strains of morbilliviruses, such as Rinderpest virus and Peste des petits ruminants virus. MVA-T7 was found to be highly cytopathic in the primary cells, multiplying rapidly and killing the cells within 3-5 days of infection, even when very low multiplicities of infection (MOI) were used. In contrast, FP-T7, which appeared to express similar amounts of T7 polymerase, was found to be non-cytopathic in a variety of primary and established cell lines of mammalian origin and was suitable for use in virus rescue experiments. MDBK cells and primary cells, unlike Vero cells, could not be efficiently transfected and so were unsuitable for virus rescue. Optimal conditions for rinderpest virus rescue in Vero cells were established using FP-T7 in place of MVA-T7. This system will be suitable for rescuing other viruses which grow in Vero cells.

The spectrum of mutations, including four novel ones, in the thiamine-responsive megaloblastic anemia gene SLC19A2 of eight families

Thiamine responsive megaloblastic anemia (TRMA) is an autosomal recessive disorder with a triad of symptoms: megaloblastic anemia, deafness, and non-type 1 diabetes mellitus. Occasionally, cardiac abnormalities and abnormalities of the optic nerve and retina occur as well. Patients with TRMA often respond to treatment with pharmacological doses of thiamine. Recently, mutations were found in patients with TRMA in a thiamine transporter gene (SLC19A2). We here describe the mutations found in eight additional families. We found four novel mutations and three that were previously described. Of the novel ones, one is a nonsense mutation in exon 1 (E65X), two are missense mutations in exon 2 (S142F, D93H), and another is a mutation in the splicing donor site at the 5' end of intron 4 (C1223+1G>A). We also summarize the state of knowledge on all mutations found to date in TRMA patients. SLC19A2 is the first thiamine transporter gene to be described in humans. Reviewing the location and effect of the disease causing mutations can shed light on the way the protein functions and suggest ways to continue its investigation.

EIF2AK3, encoding translation initiation factor 2-alpha kinase 3, is mutated in patients with Wolcott-Rallison syndrome

Wolcott-Rallison syndrome (WRS) is a rare, autosomal recessive disorder characterized by permanent neonatal or early infancy insulin-dependent diabetes. Epiphyseal dysplasia, osteoporosis and growth retardation occur at a later age. Other frequent multisystemic manifestations include hepatic and renal dysfunction, mental retardation and cardiovascular abnormalities. On the basis of two consanguineous families, we mapped WRS to a region of less than 3 cM on chromosome 2p12, with maximal evidence of linkage and homozygosity at 4 microsatellite markers within an interval of approximately 1 cM. The gene encoding the eukaryotic translation initiation factor 2-alpha kinase 3 (EIF2AK3) resides in this interval; thus we explored it as a candidate. We identified distinct mutations of EIF2AK3 that segregated with the disorder in each of the families. The first mutation produces a truncated protein in which the entire catalytic domain is missing. The other changes an amino acid, located in the catalytic domain of the protein, that is highly conserved among kinases from the same subfamily. Our results provide evidence for the role of EIF2AK3 in WRS. The identification of this gene may provide insight into the understanding of the more common forms of diabetes and other pathologic manifestations of WRS.

Identification of T-helper cell epitopes in the hypervariable region of the nucleocapsid (N) protein of rinderpest virus (RPV) in cattle

The proliferative responses to synthetic peptides by lymphocytes derived from rinderpest virus (RPV)-infected cattle, the natural host for RPV, were assayed by determining [3H]thymidine incorporation into the DNA. In eight out of twelve cattle tested, significant responses were detected to peptides representing amino acids 452-501 in the C-terminal hypervariable region of the virus nucleocapsid (N) protein. It appears that helper T-cell epitope(s) for cattle which can be broadly recognized within an MHC diverse population, exists in this region of the protein.

Long-term protective immunity to rinderpest in cattle following a single vaccination with a recombinant vaccinia virus expressing the virus haemagglutinin protein

A recombinant vaccine, produced by using a highly attenuated smallpox vaccine (LC16mO) as a vector and which expresses the rinderpest virus (RPV) haemagglutinin protein, has been developed. The properties of this vaccine, including its heat stability, efficacy in short-term trials, safety and genetic stability, have been confirmed in an earlier report. In the present study, the duration of the protective immunity generated by the vaccine in cattle was examined for up to 3 years following the administration of a single vaccination dose of 10(8) p.f.u. The vaccinated cattle were kept for 2 (group I) or 3 years (group II) and then challenged with a highly virulent strain of RPV. Four of five vaccinated cattle in group I and all six cattle in group II survived the challenge, some showing solid immunity without any clinical signs of rinderpest. Neutralizing antibodies were maintained at a significant level for up to 3 years and they increased rapidly following challenge. Lymphocyte proliferative responses to RPV were examined in group II cattle and were observed in four of the six vaccinated cattle in this group. The long-lasting protective immunity, in addition to the other properties confirmed previously, indicate the practical usefulness of this vaccine for field use.

Does melatonin modulate beta-endorphin, corticosterone, and pain threshold?

Converging lines of evidence suggest that the pineal hormone, melatonin, may regulate changes in pain threshold by modulating fluctuations in opioid receptor expression and levels of beta-endorphin (beta-END). This study investigated whether the circadian oscillation in plasma melatonin is involved in the modulation of plasma beta-END immunoreactivity (beta-END-ir), and whether fluctuations in pain threshold measured using the hotplate test are contingent upon the fluctuation of these two hormones in Rattus Norvegicus. The role of melatonin was explored using light-induced functional pinealectomy (LFPX) to suppress nocturnal melatonin release. Pinealectomized rats were found to have significantly elevated levels of beta-END-ir compared to control animals at both photophase (398 +/- 89 pg/ml versus 180 +/- 23 pg/ml) and scotophase (373 +/- 45 pg/ml versus 203 +/- 20 pg/ml) test-periods, thus supporting the putative melatonin-opioid axis. Similarly, latency to pain threshold of LFPX rats was significantly longer when compared to control animals at photophase (7.3 +/- 1.4 sec versus 4.8 +/- 0.7 sec) and scotophase (6.3 +/- 0.7 sec versus 5.1 +/- 0.7 sec). Previous studies have produced conflicting data regarding the role of the pineal system in modulating levels of corticosterone (CORT). We observed a moderate, but non-significant, increase in the CORT concentration of LFPX rats during the photophase test period.

Bipolar disorder and variation at a common polymorphism (A1832G) within exon 8 of the Wolfram gene

A number of linkage studies provide evidence consistent with the existence of a bipolar susceptibility gene on chromosome 4p16. The gene for Wolfram syndrome, a rare recessive neurodegenerative disorder, lies in this region and has recently been cloned. Psychiatric disturbances including psychosis, mood disorder, and suicide have been reported at increased frequency in Wolfram patients and in heterozygous carriers of a Wolfram mutation. In the current investigation we have undertaken a case-control association study using a single nucleotide polymorphism (causing an amino acid change) in exon 8 of the Wolfram gene in a UK Caucasian sample of 312 Diagnostic and Statistical Manual of Mental Disorders (fourth edition; DSM IV) bipolar I probands and 301 comparison individuals. We found no evidence that variation at this polymorphism influences susceptibility to bipolar disorder. It remains possible that variation at other sites within or near the Wolfram gene plays important roles in determining susceptibility to affective illness. Am. J. Med. Genet. (Neuropsychiatr. Genet.) 96:154-157, 2000.

Spontaneous conception after a successful attempt at in vitro fertilization/intracytoplasmic sperm injection

OBJECTIVE

To determine the incidence of spontaneous pregnancy in women who were not actively undergoing therapy after a successful attempt at IVF/intracytoplasmic sperm injection and to characterize its pattern of occurrence.

DESIGN

Retrospective postal questionnaire.

SETTING

An assisted reproduction unit at a university-based teaching hospital.

PATIENT(S)

Five hundred thirteen replies were received from 530 questionnaires mailed.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Spontaneous pregnancy. Women who did and did not conceive spontaneously after successful IVF treatment were compared in terms of their age, duration of infertility, previous reproductive history, and indication for treatment at the time of assisted reproduction.

RESULT(S)

The rate of spontaneous conception among the survey respondents was 20.7%. Younger women (</=34 years of age) had a higher rate of spontaneous conception, as did those with a shorter duration of infertility. Women with unexplained infertility and endometriosis also were more likely to conceive. Few of those who had undergone intracytoplasmic sperm injection conceived, whereas 21.6% of those whose partners had had sperm quality sufficient for IVF later conceived spontaneously.

CONCLUSION(S)

The chances of spontaneous conception after successful ART therapy are significant in some groups of patients. This has implications for the practice of assisted reproduction and the obstetric care of patients who conceive with treatment. Contraceptive advice may need to be provided to couples who undergo IVF/intracytoplasmic sperm injection.

Rinderpest viruses lacking the C and V proteins show specific defects in growth and transcription of viral RNAs

Rinderpest virus is a morbillivirus and the causative agent of an important disease of cattle and wild bovids. The P genes of all morbilliviruses give rise to two proteins in addition to the P protein itself: use of an alternate start translation site, in a second open reading frame, gives rise to the C protein, while cotranscriptional insertion of an extra base gives rise to the V protein, a fusion of the amino-terminal half of P to a short, highly conserved, cysteine-rich zinc binding domain. Little is known about the function of either of these two proteins in the rinderpest virus life cycle. We have constructed recombinant rinderpest viruses in which the expression of these proteins has been suppressed, individually and together, and studied the replication of these viruses in tissue culture. We show that the absence of the V protein has little effect on the replication rate of the virus but does lead to an increase in synthesis of genome and antigenome RNAs and a change in cytopathic effect to a more syncytium-forming phenotype. Virus that does not express the C protein, on the other hand, is clearly defective in growth in all cell lines tested, and this defect appears to be related to a decreased transcription of mRNA from viral genes. The phenotypes of both individual mutant virus types are both expressed in the double mutant expressing neither V nor C.

Development of a genetically marked recombinant rinderpest vaccine expressing green fluorescent protein

In order to effectively control and eliminate rinderpest, a method is required to allow serological differentiation between animals that have been vaccinated and those which have recovered from natural infection. One way of doing this would be to engineer the normal vaccine to produce a genetically marked rinderpest virus (RPV) vaccine. We constructed two modified cDNA clones of the RPV RBOK vaccine strain with the coding sequence of the green fluorescent protein (GFP) gene inserted as a potential genetic marker. RPVINS-GFP virus was designed to produce independent and high level expression of GFP inside infected cells, whilst the GFP expressed by RPVSIG-GFP virus was designed to be efficiently secreted. Infectious recombinant virus was rescued in cell culture from both constructs. The effectiveness of these viruses in stimulating protective immunity and antibody responses to the marker protein was tested by vaccination of cattle and goats. All of the vaccinated animals were completely protected when challenged with virulent virus: RPV in cattle or peste-des-petits ruminants virus in the goats. ELISA showed that all of the animals produced good levels of anti-RPV antibodies. Three of the four cattle and the two goats vaccinated with RPVSIG-GFP produced detectable levels of anti-GFP antibodies. In contrast, no anti-GFP antibodies were produced in the four cattle and two goats vaccinated with RPVINS-GFP. Therefore, secretion of the GFP marker protein was absolutely required to elicit an effective humoral antibody response to the marker protein.

Rinderpest: the disease and its impact on humans and animals

Rinderpest is an ancient plague of cattle and other large ruminants, with descriptions of its effects dating back to Roman times. It is caused by a morbillivirus closely related to human measles virus. Although a very effective vaccine is available, it is heat labile, and logistical and financial problems hamper its delivery to the remote areas of Africa and Asia where enzootic foci remain. Periodic epizootics emerge from these foci and spread into neighboring areas, mainly as a result of uncontrolled livestock movement and trading. This is particularly true during wars or civil disturbances when normal veterinary controls do not operate. The disease continues to cause devastating economic losses in domestic livestock in areas of the world where it remains endemic.

Mass die-Off of Caspian seals caused by canine distemper virus

Thousands of Caspian seals (Phoca caspica) died in the Caspian Sea from April to August 2000. Lesions characteristic of morbillivirus infection were found in tissue specimens from dead seals. Canine distemper virus infection was identified by serologic examination, reverse transcriptase- polymerase chain reaction, and sequencing of selected P gene fragments. These results implicate canine distemper virus infection as the primary cause of death.

Rinderpest epidemic in wild ruminants in Kenya 1993-97

A severe epidemic of rinderpest, affecting mainly wild ruminants, occurred between 1993 and 1997 in East Africa. Buffalo (Syncerus caffer), eland (Taurotragus oryx) and lesser kudu (Tragelaphus imberbis) were highly susceptible. The histopathological changes, notably individual epithelial cell necrosis with syncytia formation, were consistent with an infection with an epitheliotrophic virus. Serology, the polymerase chain reaction, and virus isolation confirmed the diagnosis and provided epidemiological information. The virus was related to a strain which was prevalent in Kenya in the 1960s, of a second lineage (II), and distinct from isolations of rinderpest virus in the region since 1986. The source of the virus was presumed to be infected cattle from the Eastern region of Kenya and Somalia. The pathogenicity of the virus varied during the epidemic. The mortality in buffalo populations was estimated to be up to 80 per cent, and population data suggested that the virus had an adverse effect on a wide range of species. The virus caused only a mild disease in cattle, with minimal mortality. The results confirmed the importance of wildlife as sentinels of the disease, but although wildlife were important in the spread of the virus, they did not appear to act as reservoirs of infection.

Morbillivirus infections, with special emphasis on morbilliviruses of carnivores

Morbilliviruses infections cause significant mortality in human beings and animals. Measles virus is responsible for up to two million childhood deaths annually in the developing world, while rinderpest and peste des petits ruminants cause severe epizootics in domestic and wild ruminants in areas of the world where they remain endemic. Canine distemper virus (CDV) is a cause of fatal disease in many species of carnivores. Distemper is controlled by vaccination in domestic dogs and farmed mink, but it may be impossible to eradicate the virus because of its global distribution and wide variety of susceptible host species, which includes both freshwater and marine seals. Research is currently under way to develop new recombinant vaccines, since the currently available live attenuated vaccines for CDV are not safe for use for all species and many valuable zoo animals need to be protected from CDV. New morbilliviruses with potentially disastrous ecological consequences for marine mammals have been discovered in the past decade; phocid distemper virus (PDV) in seals and the cetacean morbillivirus (CMV) has been found in dolphins, whales and porpoises. Reverse transcription, coupled with the polymerase chain reaction (RT/PCR) and nucleic acid sequencing, has been used to characterise the morbilliviruses and has given insights into the evolution of this virus genus.

Analysis of the H gene, the central untranslated region and the proximal coding part of the F gene of wild-type and vaccine canine distemper viruses

This paper summarizes the results of the genetic analysis of several parts of the genome of canine distemper virus (CDV) field isolates and vaccine viruses. The haemagglutinin (H) gene analysis showed that recent viruses did not differ significantly from vaccine strains. The analysis of the long untranslated region between the matrix (M) and fusion (F) gene revealed distinct genetic heterogeneity. The putative F protein start codon AUG461 of vaccine strain Onderstepoort was found to be mutated in all wild-type isolates and in another vaccine strain. The proximal coding part of the F gene was well conserved. Phylogenetic analysis of this segment showed the presence of several cocirculating CDV genotypes.

Mutations in SLC19A2 cause thiamine-responsive megaloblastic anaemia associated with diabetes mellitus and deafness

Thiamine-responsive megaloblastic anaemia (TRMA), also known as Rogers syndrome, is an early onset, autosomal recessive disorder defined by the occurrence of megaloblastic anaemia, diabetes mellitus and sensorineural deafness, responding in varying degrees to thiamine treatment (MIM 249270). We have previously narrowed the TRMA locus from a 16-cM to a 4-cM interval on chromosomal region 1q23.3 (refs 3,4) and this region has been further refined to a 1.4-cM interval. Previous studies have suggested that deficiency in a high-affinity thiamine transporter may cause this disorder. Here we identify the TRMA gene by positional cloning. We assembled a P1-derived artificial chromosome (PAC) contig spanning the TRMA candidate region. This clarified the order of genetic markers across the TRMA locus, provided 9 new polymorphic markers and narrowed the locus to an approximately 400-kb region. Mutations in a new gene, SLC19A2, encoding a putative transmembrane protein homologous to the reduced folate carrier proteins, were found in all affected individuals in six TRMA families, suggesting that a defective thiamine transporter protein (THTR-1) may underlie the TRMA syndrome.

Cell-mediated immune responses in cattle vaccinated with a vaccinia virus recombinant expressing the nucleocapsid protein of rinderpest virus

Rinderpest virus (RPV) is a member of the genus Morbillivirus in the family Paramyxoviridae which causes an acute and often fatal disease in large ruminants. To examine the immune response to the virus nucleocapsid (N) protein, a recombinant vaccinia virus expressing RPV nucleocapsid protein (rVV-RPV-N) was used to vaccinate cattle. The recombinant vaccine induced low levels of non-neutralizing anti-N antibodies. RPV-specific cell-mediated immunity induced by the recombinant was assessed by measuring both the lymphocyte proliferation and cytotoxic T-lymphocyte responses. The protective immune response was examined by challenging the vaccinated cattle with either a highly virulent (Saudi 1/81) or a mild (Kenya/eland/96) strain of the virus. The vaccinated cattle were not protected against challenge with the virulent RPV strain, except they showed a slight delay in the onset of disease when compared with the unvaccinated controls. In cattle challenged with the mild strain, apart from a transient fever, no clinical signs of rinderpest infection were seen in the vaccinated cattle. One out of two control cattle showed a similar response but the other died from classic rinderpest disease. Virus-neutralizing antibodies were induced more quickly following challenge with the mild strain in vaccinated cattle compared to the control animals. These data suggested that the cell-mediated immunity induced by rVV-RPV-N could stimulate the rapid production of neutralizing antibodies following RPV challenge but this response was not sufficient to protect against challenge with a virulent strain of the virus. Protection was seen in one of three animals challenged with a mild strain of the virus; however, a greater number of animals would need to be tested to estimate the significance of the protection afforded by the N protein.

Trimethylamine and foetor hepaticus

BACKGROUND

In patients with various degrees of hepatocellular failure and portosystemic shunting of blood, the breath may acquire a sweet, musty, or even slightly faecal aroma, termed foetor hepaticus, which has been attributed mainly to volatile sulphur compounds with contributions from various nitrogenous substances. Not infrequently in such patients, unusual body odours are also encountered and, by analogy with the 'fish-odour syndrome' known to be caused by excessive trimethylamine, the availability of this latter graveolent amine to potentially contribute to odours associated with hepatic disease was investigated.

METHODS

Urine (0-24 h) was collected from 63 patients with various liver diseases previously confirmed in hospital by means of various biochemical, immunologic, pathologic, and radiologic investigations. Total trimethylamine and trimethylamine N-oxide levels in urine were measured with head-space gas chromatography.

RESULTS

In total, 50% (32 of 63) of the patients (primary liver disease, 25 of 47, or 53.2%; secondary liver disease, 7 of 16, or 43.8%) had urinary trimethylamine levels greater than the upper end of the range considered normal (0.08-1.84 microg/ml). Seventeen patients excreted large amounts of free trimethylamine (more than 10 microg/ml), above the threshold usually associated with the appearance of a 'fish-like' body odour and tainted breath.

CONCLUSIONS

Excessive amounts of trimethylamine may well contribute to the overall body odour problems encountered among patients with severe hepatic disease, precipitating in these individuals a secondary form of the 'fish-odour syndrome'.

Guideline for i.v. infiltrations in pediatric patients

A large Midwestern tertiary care center used a multidisciplinary approach to develop an intravenous infiltration/extravasation guideline for pediatric patients, ages 0-18 years old, using the Iowa Model for research utilization. This infiltration clinical practice guideline included a site appearance staging tool, decision algorithm, research-based antidotes, and standard of care. The goal of the guideline was to prevent or minimize adverse occurrences for pediatric patients at risk for intravenous infiltrations. Quality assessment and improvement tracking suggested that there was an increased consistency in use of practice guideline interventions for and reporting of the infiltration event, a reduction in adverse patient outcomes and potential cost savings.

The MKK7 gene encodes a group of c-Jun NH2-terminal kinase kinases

The c-Jun NH2-terminal protein kinase (JNK) is a member of the mitogen-activated protein kinase (MAPK) group and is an essential component of a signaling cascade that is activated by exposure of cells to environmental stress. JNK activation is regulated by phosphorylation on both Thr and Tyr residues by a dual-specificity MAPK kinase (MAPKK). Two MAPKKs, MKK4 and MKK7, have been identified as JNK activators. Genetic studies demonstrate that MKK4 and MKK7 serve nonredundant functions as activators of JNK in vivo. We report here the molecular cloning of the gene that encodes MKK7 and demonstrate that six isoforms are created by alternative splicing to generate a group of protein kinases with three different NH2 termini (alpha, beta, and gamma isoforms) and two different COOH termini (1 and 2 isoforms). The MKK7alpha isoforms lack an NH2-terminal extension that is present in the other MKK7 isoforms. This NH2-terminal extension binds directly to the MKK7 substrate JNK. Comparison of the activities of the MKK7 isoforms demonstrates that the MKK7alpha isoforms exhibit lower activity, but a higher level of inducible fold activation, than the corresponding MKK7beta and MKK7gamma isoforms. Immunofluorescence analysis demonstrates that these MKK7 isoforms are detected in both cytoplasmic and nuclear compartments of cultured cells. The presence of MKK7 in the nucleus was not, however, required for JNK activation in vivo. These data establish that the MKK4 and MKK7 genes encode a group of protein kinases with different biochemical properties that mediate activation of JNK in response to extracellular stimuli.

New approaches to the development of virus vaccines for veterinary use

The marked progress in recombinant deoxyribonucleic acid (DNA) technology during the past decade has led to the development of a variety of safe new vaccine vectors which are capable of efficiently expressing foreign immunogens. These have been based on a variety of virus types--poxviruses, herpesviruses and adenoviruses--and have led to the production of many new potential recombinant vaccines. Of these recombinant vaccines, the rabies vaccine, in which the rabies G protein is expressed in a vaccinia vector, has been widely used in the field to prevent the spread of rabies both in Europe and in the United States of America. A recombinant Newcastle disease virus vaccine, using fowlpox virus as the vector to express immunogenic proteins from the Newcastle disease virus, has been licensed as the first commercial recombinant vectored vaccine. Many other recombinant virus vaccines are still at the stage of laboratory or field testing. The most recent breakthrough in vaccinology has been the success with the use of naked DNA as a means of vaccination. This approach has shown great promise in mouse model systems and has now become the most active field in new vaccine development. Molecular redesigning of conventional ribonucleic acid (RNA) viruses to obtain more stable attenuated vaccines was previously possible only for positive-strand RNA viruses, such as poliovirus. However, recent advances in molecular biological techniques have enabled the rescuing of negative-strand viruses from DNA copies of their genomes. This has made it possible to engineer specific changes in the genomes of Rhabdoviridae and Paramyxoviridae, both of which include several viruses of veterinary importance. The authors describe the current progress in the development of vector vaccines, DNA vaccines and vaccines based on engineered positive- and negative-strand RNA virus genomes, with special emphasis on their application to diseases of veterinary importance.

Morbillivirus downregulation of CD46

There is evidence that CD46 (membrane cofactor protein) is a cellular receptor for vaccine and laboratory-passaged strains of measles virus (MV). Following infection with these MV strains, CD46 is downregulated from the cell surface, and consequent complement-mediated lysis has been shown to occur upon infection of a human monocytic cell line. The MV hemagglutinin (H) protein alone is capable of inducing this downregulation. Some wild-type strains of MV fail to downregulate CD46, despite infection being prevented by anti-CD46 antibodies. In this study we show that CD46 is also downregulated to the same extent by wild-type, vaccine, and laboratory-passaged strains of rinderpest virus (RPV), although CD46 did not appear to be the receptor for RPV. Expression of the RPV H protein by a nonreplicating adenovirus vector was also found to cause this downregulation. A vaccine strain of peste des petits ruminants virus caused slight downregulation of CD46 in infected Vero cells, while wild-type and vaccine strains of canine distemper virus and a wild-type strain of dolphin morbillivirus failed to downregulate CD46. Downregulation of CD46 can, therefore, be a function independent of the use of this protein as a virus receptor.