Two replication-defective adenoviral vaccine vectors for the induction of immune responses to PPRV

Peste des petits ruminants is a highly contagious disease of small ruminants caused by a Morbillivirus, peste des petits ruminants virus (PPRV). Two recombinant replication-defective human adenovirus serotype 5 (Ad5) containing the highly immunogenic fusion protein (F) and hemaglutinine protein (H) genes from PPRV were constructed. HEK293A cells infected with either virus (Ad5-PPRV-F or -H) express F and H proteins respectively. These viruses were used to vaccinate mice by intramuscular inoculation. Both viruses elicited PPRV-specific B- and T-cell responses. Thus, after two immunizations, sera from immunized mice elicited neutralizing antibody response, indicating that this approach has the potential to confer protective immunity. In addition, we detected a significant antigen specific CD4⁺ and CD8⁺ T-cell response in mice vaccinated with either virus. These results indicate that these adenovirus constructs offer a promising alternative to current vaccine strategies for the development of PPRV DIVA vaccines.     

Emergence of peste des petits ruminants virus lineage IV in Ismailia Province,Egypt

Peste des petits ruminants (PPR) is an acute, highly contagious fatal disease of small ruminants characterized by high fever, ocular and nasal discharge, pneumonia, erosive stomatitis and severe enteritis that ultimately results in high mortalities. Peste des petits ruminants virus (PPRV) is widely distributed and endemic in several African, middle eastern and south Asian countries and it poses a threat to European countries. Egyptian veterinary medical authorities stated that Egypt is free from PPRV and the only measures for disease control are test and slaughter of infected population to maintain the free status. The aim of our investigation was to detect PPRV in Ismailia province as an indicator of the infection status in Egypt and perform molecular characterization of the emerging virus to gain insight into the origin of circulating virus. A total of 40 representative clinical samples, from a single goat case and goat flock in 2010 and sheep flock in 2012, were tested for PPRV by RT-PCR. About 21 (52.5%) samples were positive. The phylogenetic analysis of the detected viruses revealed circulation of PPRV lineage IV. The circulating viruses are closely related to Sudanese and Saudia Arabian strains with nucleotide identity ranged from 99.2% to 99.6%, respectively. Also, it is closely related to Moroccan 2008 viruses with identities ranged from 97.6% to 98%. Epidemiological investigation at the national level is recommended for monitoring PPRV spread and implementing an appropriate control program.     

Enhanced immunosurveillance for animal morbilliviruses using vesicular stomatitis virus (VSV) pseudotypes

The measurement of virus-specific neutralising antibodies represents the “gold-standard” for diagnostic serology. For animal morbilliviruses, such as peste des petits ruminants (PPRV) or rinderpest virus (RPV), live virus-based neutralisation tests require high-level biocontainment to prevent the accidental escape of the infectious agents. In this study, we describe the adaptation of a replication-defective vesicular stomatitis virus (VSVΔG) based pseudotyping system for the measurement of neutralising antibodies against animal morbilliviruses. By expressing the haemagglutinin (H) and fusion (F) proteins of PPRV on VSVΔG pseudotypes bearing a luciferase marker gene, neutralising antibody titres could be measured rapidly and with high sensitivity. Serological responses against the four distinct lineages of PPRV could be measured simultaneously and cross-neutralising responses against other morbilliviruses compared. Using this approach, we observed that titres of neutralising antibodies induced by vaccination with live attenuated PPRV were lower than those induced by wild type virus infection and the level of cross-lineage neutralisation varied between vaccinates. By comparing neutralising responses from animals infected with either PPRV or RPV, we found that responses were highest against the homologous virus, indicating that retrospective analyses of serum samples could be used to confirm the nature of the original pathogen to which an animal had been exposed. Accordingly, when screening sera from domestic livestock and wild ruminants in Tanzania, we detected evidence of cross-species infection with PPRV, canine distemper virus (CDV) and a RPV-related bovine morbillivirus, suggesting that exposure to animal morbilliviruses may be more widespread than indicated previously using existing diagnostic techniques.     

Immune responses in goats to recombinant hemagglutinin-neuraminidase glycoprotein of Peste des petits ruminants virus: identification of a T cell determinant

Peste des petits ruminants virus (PPRV), a member of the genus Morbillivirus within the family Paramyxoviridae, causes a fatal disease ‘peste des petits ruminants’ in goats and sheep. This enveloped virus is antigenically closely related to rinderpest virus (RPV), which causes a similar but distinct disease in large ruminants. PPRV harbors two major surface glycoproteins, the hemagglutinin-neuraminidase (HN) and the fusion (F) proteins. The surface glycoproteins of morbilliviruses are highly immunogenic and confer protective immunity. In this study, we investigated the immune responses generated in goats immunized with low doses of purified recombinant extracellular baculovirus carrying a membrane bound form of the HN protein of PPRV without any adjuvant. We report that the immunized goats develop both humoral and cell-mediated immune responses. Antibodies generated in the immunized animals could neutralize both PPRV and RPV in vitro. Further, using a combination of Escherichia coli expressed deletion mutants of PPRV-HN and RPV-H proteins, and synthetic peptides corresponding to the highly conserved N-terminal sequences of MV-H protein, we have mapped an N-terminal T cell determinant (amino acids 123–137) and a C-terminal domain (amino acids 242–609) harboring potential T cell determinant(s) in goats.     

Immune responses in goats to recombinant hemagglutinin-neuraminidase glycoprotein of Peste des petits ruminants virus: identification of a T cell determinant

Peste des petits ruminants virus (PPRV), a member of the genus Morbillivirus within the family Paramyxoviridae, causes a fatal disease ‘peste des petits ruminants’ in goats and sheep. This enveloped virus is antigenically closely related to rinderpest virus (RPV), which causes a similar but distinct disease in large ruminants. PPRV harbors two major surface glycoproteins, the hemagglutinin-neuraminidase (HN) and the fusion (F) proteins. The surface glycoproteins of morbilliviruses are highly immunogenic and confer protective immunity. In this study, we investigated the immune responses generated in goats immunized with low doses of purified recombinant extracellular baculovirus carrying a membrane bound form of the HN protein of PPRV without any adjuvant. We report that the immunized goats develop both humoral and cell-mediated immune responses. Antibodies generated in the immunized animals could neutralize both PPRV and RPV in vitro. Further, using a combination of Escherichia coli expressed deletion mutants of PPRV-HN and RPV-H proteins, and synthetic peptides corresponding to the highly conserved N-terminal sequences of MV-H protein, we have mapped an N-terminal T cell determinant (amino acids 123–137) and a C-terminal domain (amino acids 242–609) harboring potential T cell determinant(s) in goats.     

Interference in the vaccination of cattle against rinderpest virus by antibodies against peste des petits ruminants (PPR) virus

The ability of the attenuated vaccine 75/1 of peste des petits ruminants to interfere with rinderpest vaccination in cattle was investigated experimentally. Young cattle (93) were selected and tested as being negative for antibodies against RP or PPR viruses. These were vaccinated with the peste des petits ruminants attenuated vaccine strain PPR75/1. All animals produced specific antibodies against the peste des petits ruminants vaccine after one or two doses. The cattle were then vaccinated with attenuated rinderpest vaccine. Two months later, 88 of these animals were sampled and 21/88 were positive for antibodies specific for rinderpest. The 67 negative animals received a second rinderpest vaccine dose after which 31seroconverted. The 36 animals which failed to seroconvert were re-vaccinated, of these 28 seroconverted. This study highlights the interference by peste des petits ruminants vaccination, presumably through production of antibodies that cross react with the live rinderpest virus in the vaccine used. This interference is also observed after vaccination against rinderpest followed by subsequent administration of peste des petits ruminants vaccine.     

Molecular Evolution of Peste des Petits Ruminants Virus

Despite safe and efficacious vaccines against peste des petits ruminants virus (PPRV), this virus has emerged as the cause of a highly contagious disease with serious economic consequences for small ruminant agriculture across Asia, the Middle East, and Africa. We used complete and partial genome sequences of all 4 lineages of the virus to investigate evolutionary and epidemiologic dynamics of PPRV. A Bayesian phylogenetic analysis of all PPRV lineages mapped the time to most recent common ancestor and initial divergence of PPRV to a lineage III isolate at the beginning of 20th century. A phylogeographic approach estimated the probability for root location of an ancestral PPRV and individual lineages as being Nigeria for PPRV, Senegal for lineage I, Nigeria/Ghana for lineage II, Sudan for lineage III, and India for lineage IV. Substitution rates are critical parameters for understanding virus evolution because restrictions in genetic variation can lead to lower adaptability and pathogenicity.     

Spillover of Peste des Petits Ruminants Virus from Domestic to Wild Ruminants in the Serengeti Ecosystem,Tanzania

We tested wildlife inhabiting areas near domestic livestock, pastures, and water sources in the Ngorongoro district in the Serengeti ecosystem of northern Tanzania and found 63% seropositivity for peste des petits ruminants virus. Sequencing of the viral genome from sick sheep in the area confirmed lineage II virus circulation.     

The detection of peste des petits ruminants (PPR) virus antigen by agar gel precipitation test and counter-immunoelectrophoresis.

The detectability of peste des petits ruminants (PPR) viral antigen in both ante-mortem secretions and necropsy samples from experimentally infected goats was investigated by both the agar gel precipitation test (AGPT) and counter-immunoelectrophoresis (CIE). Viral antigen was detected from 42.6% of the samples tested by the AGPT and 80.3% by CIE. The detection of viral antigen in a high proportion of the ocular and nasal secretions as well as the faeces and buccal scrapings, particularly from those collected within seven days of the onset of fever, by both techniques, would seem to obviate the need for lymph node biopsies or post-mortem samples in order to make a diagnosis of PPRV infection.     

The detection of peste des petits ruminants (PPR) virus antigen by agar gel precipitation test and counter-immunoelectrophoresis

The detectability of peste des petits ruminants (PPR) viral antigen in both ante-mortem secretions and necropsy samples from experimentally infected goats was investigated by both the agar gel precipitation test (AGPT) and counter-immunoelectrophoresis (CIE). Viral antigen was detected from 42.6% of the samples tested by the AGPT and 80.3% by CIE. The detection of viral antigen in a high proportion of the ocular and nasal secretions as well as the faeces and buccal scrapings, particularly from those collected within seven days of the onset of fever, by both techniques, would seem to obviate the need for lymph node biopsies or post-mortem samples in order to make a diagnosis of PPRV infection.     

Mumps-specific cross-neutralization by MMR vaccine-induced antibodies predicts protection against mumps virus infection

BackgroundSimilar to other recent mumps genotype G outbreaks worldwide, most mumps patients during the recent mumps genotype G outbreaks in the Netherlands had received 2 doses of measles, mumps and rubella (MMR) vaccine during childhood. Here, we investigate the capacity of vaccine-induced antibodies to neutralize wild type mumps virus strains, including mumps virus genotype G.MethodsIn this study, we tested 105 pre-outbreak serum samples from students who had received 2 MMR vaccine doses and who had no mumps virus infection (n = 76), symptomatic mumps virus infection (n = 10) or asymptomatic mumps virus infection (n = 19) during the mumps outbreaks. In all samples, mumps-specific IgG concentrations were measured by multiplex immunoassay and neutralization titers were measured against the Jeryl Lynn vaccine strain and against wild type genotype G and genotype D mumps virus strains.ResultsThe correlation between mumps-specific IgG concentrations and neutralization titers against Jeryl Lynn was poor, which suggests that IgG concentrations do not adequately represent immunological protection against mumps virus infection by antibody neutralization. Pre-outbreak neutralization titers in infected persons were significantly lower against genotype G than against the vaccine strain. Furthermore, antibody neutralization of wild type mumps virus genotype G and genotype D was significantly reduced in pre-outbreak samples from infected persons as compared with non-infected persons. No statistically significant difference was found for the vaccine strain. The sensitivity/specificity ratio was largest for neutralization of the genotype G strain as compared with the genotype D strain and the vaccine strain.ConclusionsThe reduced neutralization of wild type mumps virus strains in MMR vaccinated persons prior to infection indicates that pre-outbreak mumps virus neutralization is partly strain-specific and that neutralization differs between infected and non-infected persons. Therefore, we recommend the use of wild type mumps virus neutralization assays as preferred tool for surveillance of protection against mumps virus infection.     

A vero cell derived combined vaccine against sheep pox and Peste des Petits ruminants for sheep

The combined sheep pox and Peste des Petits ruminants (PPR) vaccine was prepared in lyophilized form containing recommended doses of both vaccine viruses. Safety and immunogenicity of this combined vaccine was evaluated in sheep. Sheep immunized subcutaneously with 1 ml of live attenuated vaccine consisting of 10³ TCID₅₀ each of sheep pox virus (SPV) Romanian Fanar (RF) strain and Peste des Petits ruminants virus (PPRV-Sungri/96 strain) were monitored for clinical and serological responses for a period of four weeks post immunization (pi) and two week post challenge (pc). Specific antibodies directed to sheep pox virus could be demonstrated by indirect ELISA and serum neutralization test (SNT). Competitive ELISA and SNT were used for demonstration of antibodies to PPR virus. All the immunized animals resisted challenge with virulent SPV or PPRV on day 30 pi, while control animals developed characteristic signs of disease. Specific virus could be detected in the unvaccinated control animals after challenge but not from any of the immunized sheep. Combined vaccine was found to be safe and potent as evident from sero conversion as well as challenge studies in sheep. This indicates that component vaccines did not interfere each other and can be used in target population for economic vaccination strategies.     

Morbillivirus vaccines: Recent successes and future hopes

The impact of morbilliviruses on both human and animal populations is well documented in the history of mankind. Indeed, prior to the development of vaccines for these diseases, morbilliviruses plagued both humans and their livestock that were heavily relied upon for food and motor power within communities. Measles virus (MeV) was responsible for the death of millions of people annually across the world and those fortunate enough to escape the disease often faced starvation where their livestock had died following infection with rinderpest virus (RPV) or peste des petits ruminants virus (PPRV). Canine distemper virus has affected dog populations for centuries and in the past few decades appears to have jumped species, now causing disease in a number of non-canid species, some of which are been pushed to the brink of extinction by the virus. During the age of vaccination, the introduction and successful application of vaccines against rinderpest and measles has led to the eradication of the former and the greater control of the latter. Vaccines against PPR and canine distemper have also been generated; however, the diseases still pose a threat to susceptible species. Here we review the currently available vaccines against these four morbilliviruses and discuss the prospects for the development of new generation vaccines.     

Efficient generation of vesicular stomatitis virus (VSV)-pseudotypes bearing morbilliviral glycoproteins and their use in quantifying virus neutralising antibodies

Morbillivirus neutralising antibodies are traditionally measured using either plaque reduction neutralisation tests (PRNTs) or live virus microneutralisation tests (micro-NTs). While both test formats provide a reliable assessment of the strength and specificity of the humoral response, they are restricted by the limited number of viral strains that can be studied and often present significant biological safety concerns to the operator. In this study, we describe the adaptation of a replication-defective vesicular stomatitis virus (VSVΔG) based pseudotyping system for the measurement of morbillivirus neutralising antibodies. By expressing the haemagglutinin (H) and fusion (F) proteins of canine distemper virus (CDV) on VSVΔG pseudotypes bearing a luciferase marker gene, neutralising antibody titres could be measured rapidly and with high sensitivity. Further, by exchanging the glycoprotein expression construct, responses against distinct viral strains or species may be measured. Using this technique, we demonstrate cross neutralisation between CDV and peste des petits ruminants virus (PPRV). As an example of the value of the technique, we demonstrate that UK dogs vary in the breadth of immunity induced by CDV vaccination; in some dogs the neutralising response is CDV-specific while, in others, the neutralising response extends to the ruminant morbillivirus PPRV. This technique will facilitate a comprehensive comparison of cross-neutralisation to be conducted across the morbilliviruses.     

Peste des Petits Ruminants Virus in Heilongjiang Province,China, 2014

During March 25–May 5, 2014, we investigated 11 outbreaks of peste des petits ruminants in Heilongjiang Province, China. We found that the most likely source of the outbreaks was animals from livestock markets in Shandong. Peste des petits ruminants viruses belonging to lineages II and IV were detected in sick animals.     

Molecular insights into peste des petits ruminants virus identified in Bangladesh between 2008 and 2020

An in-depth knowledge of the molecular evolution of the peste des petits ruminants virus (PPRV) is critical for the success of the current global eradication program. For this reason, a molecular evolutionary analysis of PPRVs circulating in Bangladesh over a decade (2008–2020) was performed. The complete genome sequencing of three PPRV isolates from 2008 (BD2), 2015 (BD12) and 2017 (BD17) as well as full length nucleocapsid (N), matrix (M) and fusion (F) gene sequencing of seven more samples from 2015 to 2020 was performed. Phylogenetic analysis classified all ten PPRVs from Bangladesh as members of lineage IV and showed that they were closely related to PPRV strains detected in China and Tibet during 2007–2008, and India during 2014–2018. Time scale Bayesian Maximum Clade Credibility (MCC) phylogenetic analysis of the three complete genomes revealed a mean Time to Most Recent Common Ancestor (TMRCA) of 2000. Comparative deduced amino acid residue analysis at various functional motifs of PPRVs related to virus structure and function, virulence and host adaptation, receptor binding sites and polymerase activity revealed conserved residues among the PPRVs from Bangladesh. In total sixteen epitopes were predicted from four immunogenic proteins i.e. N, M, F and haemagglutinin (H). Interestingly, the predicted epitopes from the N and M proteins shared conserved epitopes with two vaccine strains currently being used, indicating that the strains from Bangladesh could be potentially used as alternative local vaccines.     

Sero-epidemiological study of peste des petits ruminants in sheep and goats in India between 2003 and 2009

This study describes the serosurveillance of peste des petits ruminants (PPR) in sheep and goats that was carried out between 2003 and 2009 using serum samples from animals suspected of PPR that were submitted to the Rinderpest and Allied Disease Laboratory (Division of Virology of the Indian Veterinary Research Institute [IVRI]). A total of 2,197 serum samples from sheep and 2,687 from goats were screened for PPR virus (PPRV) antibody using a monoclonal antibody-based competitive enzyme-linked immunosorbent assay developed at IVRI. Screening of the 4,884 serum samples showed that the prevalence of PPRV antibody in sheep and goats was 41.01% (95% confidence interval [CI]: 31.86 to 50.16) and 46.11% (95% CI: 37.18 to 55.04), respectively, with an overall prevalence of 43.56% (95% CI: 36.78 to 50.34) during the period. This indicates increased and widespread infection with the virus in India compared with earlier reports, which is attributed to the variations in sheep and goat husbandry practices in different regions, the agro-climatic conditions, the topography of different states, the socio-economic status of individual farmers and the migration of livestock in India.