Avian Paramyxoviruses as Vectors for Vaccine Development.

Avian paramyxoviruses (APMVs) have gained a great attention to be developed as vaccine vectors against human and veterinary pathogens. Avirulent APMVs are highly safe to be used as vaccine vectors for avian and non-avian species. APMV vectored vaccines induce robust cellular and humoral immune responses in a broad range of hosts. APMV vectors can be a good platform by facilitating rapid generation of vaccines against emerging pathogens. In this chapter, we discuss application of reverse genetics of APMVs for vaccine development, design of APMV vectored vaccines, cloning of protective antigen(s) into a vector, recovery of vectored vaccines and characterization of generated vaccine viruses.

Newcastle Disease Virus as a Vaccine Vector for SARS-CoV-2.

The emergence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has resulted in more than 16 million infections and more than 600,000 deaths worldwide. There is an urgent need to develop a safe and effective vaccine against SARS-CoV-2. Currently, several strategies are being pursued to develop a safe and effective SARS-CoV-2 vaccine. However, each vaccine strategy has distinct advantages and disadvantages. Therefore, it is important to evaluate multiple vaccine platforms to select the most efficient vaccine platform for SARS-CoV-2. In this regard, Newcastle disease virus (NDV), an avian virus, has several well-suited properties for development of a vector vaccine against SARS-CoV-2. Here, we elaborate on the idea of considering NDV as a vaccine vector for SARS-CoV-2.

Comparative Protective Efficacies of Novel Avian Paramyxovirus-Vectored Vaccines against Virulent Infectious Bronchitis Virus in Chickens.

Viral vectored vaccines are desirable alternatives for conventional infectious bronchitis virus (IBV) vaccines. We have recently shown that a recombinant Newcastle disease virus (rNDV) strain LaSota expressing the spike (S) protein of IBV strain Mass-41 (rLaSota/IBV-S) was a promising vaccine candidate for IBV. Here we evaluated a novel chimeric rNDV/avian paramyxovirus serotype 2 (rNDV/APMV-2) as a vaccine vector against IBV. The rNDV/APMV-2 vector was chosen because it is much safer than the rNDV strain LaSota vector, particularly for young chicks and chicken embryos. In order to determine the effectiveness of this vector, a recombinant rNDV/APMV-2 expressing the S protein of IBV strain Mass-41 (rNDV/APMV-2/IBV-S) was constructed. The protective efficacy of this vector vaccine was compared to that of the rNDV vector vaccine. In one study, groups of one-day-old specific-pathogenic-free (SPF) chickens were immunized with rLaSota/IBV-S and rNDV/APMV-2/IBV-S and challenged four weeks later with the homologous highly virulent IBV strain Mass-41. In another study, groups of broiler chickens were single (at day one or three weeks of age) or prime-boost (prime at day one and boost at three weeks of age) immunized with rLaSota/IBV-S and/or rNDV-APMV-2/IBV-S. At weeks six of age, chickens were challenged with a highly virulent IBV strain Mass-41. Our challenge study showed that novel rNDV/APMV-2/IBV-S provided similar protection as rLaSota/IBV-S in SPF chickens. However, compared to prime-boost immunization of chickens with chimeric rNDV/APMV-2, rLaSota/IBV-S and/or a live IBV vaccine, single immunization of chickens with rLaSota/IBV-S, or live IBV vaccine provided better protection against IBV. In conclusion, we have developed the novel rNDV/APMV-2 vector expressing S protein of IBV that can be a safer vaccine against IB in chickens. Our results also suggest a single immunization with a LaSota vectored IBV vaccine candidate provides better protection than prime-boost immunization regimens.

Contributions of HA1 and HA2 Subunits of Highly Pathogenic Avian Influenza Virus in Induction of Neutralizing Antibodies and Protection in Chickens.

Highly pathogenic avian influenza virus (HPAIV) subtype H5N1 causes a devastating disease in poultry. Vaccination is an effective method of controlling avian influenza virus (AIV) infection in poultry. The hemagglutinin (HA) protein is the major determinant recognized by the immune system of the host. Cleavage of the HA precursor HA0 into HA1 and HA2 subunits is required for infectivity of the AIV. We evaluated the individual contributions of HA1 and HA2 subunits to the induction of HPAIV serum neutralizing antibodies and protective immunity in chickens. Using reverse genetics, recombinant Newcastle disease viruses (rNDVs) were generated, each expressing HA1, HA2, or HA protein of H5N1 HPAIV. Chickens were immunized with rNDVs expressing HA1, HA2, or HA. Immunization with HA induced high titers of serum neutralizing antibodies and prevented death following challenge. Immunization with HA1 or HA2 alone neither induced serum neutralizing antibodies nor prevented death following challenge. Our results suggest that interaction of HA1 and HA2 subunits is necessary for the display of epitopes on HA protein involved in the induction of neutralizing antibodies and protection. These epitopes are lost when the two subunits are separated. Therefore, vaccination with either a HA1 or HA2 subunit may not provide protection against HPAIV.

Author Correction: A recombinant avian paramyxovirus serotype 3 expressing the hemagglutinin protein protects chickens against H5N1 highly pathogenic avian influenza virus challenge.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

A recombinant avian paramyxovirus serotype 3 expressing the hemagglutinin protein protects chickens against H5N1 highly pathogenic avian influenza virus challenge.

Highly pathogenic avian influenza (HPAI) is a devastating disease of poultry and a serious threat to public health. Vaccination with inactivated virus vaccines has been applied for several years as one of the major policies to control highly pathogenic avian influenza virus (HPAIV) infections in chickens. Viral-vectored HA protein vaccines are a desirable alternative for inactivated vaccines. However, each viral vector possesses its own advantages and disadvantages for the development of a HA-based vaccine against HPAIV. Recombinant Newcastle disease virus (rNDV) strain LaSota expressing HA protein vaccine has shown promising results against HPAIV; however, its replication is restricted only to the respiratory tract. Therefore, we thought to evaluate avian paramyxovirus serotype 3 (APMV-3) strain Netherlands as a safe vaccine vector against HPAIV, which has high efficiency replication in a greater range of host organs. In this study, we generated rAPMV-3 expressing the HA protein of H5N1 HPAIV using reverse genetics and evaluated the induction of neutralizing antibodies and protection by rAPMV3 and rNDV expressing the HA protein against HPAIV challenge in chickens. Our results showed that immunization of chickens with rAPMV-3 or rNDV expressing HA protein provided complete protection against HPAIV challenge. However, immunization of chickens with rAPMV-3 expressing HA protein induced higher level of neutralizing antibodies compared to that of rNDV expressing HA protein. These results suggest that a rAPMV-3 expressing HA protein might be a better vaccine for mass-vaccination of commercial chickens in field conditions.

Author Correction: A Recombinant Newcastle Disease Virus (NDV) Expressing S Protein of Infectious Bronchitis Virus (IBV) Protects Chickens against IBV and NDV.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

A Recombinant Newcastle Disease Virus (NDV) Expressing S Protein of Infectious Bronchitis Virus (IBV) Protects Chickens against IBV and NDV.

Infectious bronchitis virus (IBV) causes a highly contagious respiratory, reproductive and urogenital tract disease in chickens worldwide, resulting in substantial economic losses for the poultry industry. Currently, live-attenuated IBV vaccines are used to control the disease. However, safety, attenuation and immunization outcomes of current vaccines are not guaranteed. Several studies indicate that attenuated IBV vaccine strains contribute to the emergence of variant viruses in the field due to mutations and recombination. Therefore, there is a need to develop a stable and safe IBV vaccine that will not create variant viruses. In this study, we generated recombinant Newcastle disease viruses (rNDVs) expressing the S1, S2 and S proteins of IBV using reverse genetics technology. Our results showed that the rNDV expressing the S protein of IBV provided better protection than the rNDV expressing S1 or S2 protein of IBV, indicating that the S protein is the best protective antigen of IBV. Immunization of 4-week-old SPF chickens with the rNDV expressing S protein elicited IBV-specific neutralizing antibodies and provided complete protection against virulent IBV and virulent NDV challenges. These results suggest that the rNDV expressing the S protein of IBV is a safe and effective bivalent vaccine candidate for both IBV and NDV.

Serological surveillance of bluetongue virus in cattle in central Iran.

The aim of this study was to evaluate the seroprevalence and distribution of antibodies to the bluetongue virus (BTV) among dairy Holstein cattle of central Iran. From September 2010 to August 2011, 892 blood samples from Holstein dairy cattle were collected from healthy animals. Blood samples were divided according to type of farm (industrial and non-industrial), season (warm and cold), location (North, South, East, and West), cattle production groups (calf, heifer, dairy and dry) and age groups (under 6 months, 6 months-2 years and over 2 years). The sera were screened using a commercially competitive enzyme-linked immunosorbent assay (c-ELISA) kit. Twenty-four sera (2.69 %) were found to be positive for BTV. Bluetongue virus seroprevalence was significantly higher (χ(2)=8.29, df=3, p < 0.05) in cattle in southern locations as compared to those in other locations. Older animals (>2 years) showed a relatively higher seroprevalence, but the difference was not statistically significant (p=0.06). No statistically significant difference in BTV seroprevalence was noted between farming systems, seasons and cattle production groups (p > 0.05). The results demonstrate that the seroprevalence of BTV is low in cattle from the Isfahan province, central Iran. Further studies are needed to determine the serotypes and vectors of BTV in the central region of Iran.

Seroprevalence of bovine leukemia virus (BLV) infection in dairy cattle in Isfahan Province, Iran.

Bovine leukemia virus (BLV), the causative agent of enzootic bovine leukosis (EBL) is an exogenous C-type oncovirus in the Retroviridae family. It causes significant economic losses associated with the costs of control and eradication programs due to carcass condemnation at slaughter and restrictions of export of cattle and semen to importing countries. The main objective of this research was to determine the seroprevalence of BLV infection in cattle herds in central region of Iran (Isfahan province) using a commercial enzyme-linked immunosorbent assay (ELISA) to detect serum antibodies against BLV. Samples of blood serum were collected from 403 female dairy cattle (Holstein-Friesian) from 21 livestock farms and 303 animals (81.9%) were BLV seropositive. A significant association was found between age as a potential risk factor and BVL seroprevalence with animals ≥ 4 years (86.6%) having a significantly (χ(2) = 35.6, p < 0.001) higher seroprevalence compared to those < 4 years (54.2%). We found no significant statistical association between seroprevalence and pregnancy, lactation status and farming systems as potential risk factors in this study (p > 0.1). It is concluded that BLV infection is a very common problem in the study area. Hence, control measures should be instituted to combat the disease and further studies are required to investigate the impact of this disease on dairy production in the country.

Seroepidemiological study of bovine respiratory viruses (BRSV, BoHV-1, PI-3V, BVDV, and BAV-3) in dairy cattle in central region of Iran (Esfahan province).

Respiratory diseases in calves are responsible for major economic losses in both beef and dairy production. Several viruses, such as bovine respiratory syncytial virus (BRSV), bovine herpes virus-1 (BoHV-1), bovine parainfluenza virus-3 (BPI-3V), bovine viral diarrhea virus (BVDV), and bovine adenoviruses (BAV), are detected in most clinical cases with respiratory signs. The aim of this study is to define seroprevalences of five major viral causes of bovine respiratory infections in cattle in central region of Iran (Esfahan province). The population targeted was 642 dairy cows (Holstein-Friesian) from 25 farms. Samples of blood serum from female cattle were examined. Sera were tested by commercial ELISA kits to detect antibody against BRSV, BoHV-1, BPI-3V, BVDV, and BAV-3. The results were analyzed by Chi-square test. In the present study, seroprevalences of BRSV, BoHV-1, PI3V, BVDV, and BAV-3 were 51.1%, 72%, 84.4%, 49.2%, and 55.6%, respectively. The present study shows that infections of bovine respiratory viruses are very common in cattle in Esfahan.

Copper, zinc, and iron concentrations in blood serum and diet of dairy cattle on semi-industrial farms in central Iran.

The aim of this study was to evaluate the blood serum and diet concentrations of copper, zinc, and iron in Holstein dairy cattle kept under semi-industrial farming in Isfahan province, central Iran. Moreover, the effects of season, pregnancy, and daily milk yield on serum Cu, Zn, and Fe concentrations were also evaluated. The study was carried out on 12 semi-industrial Holstein dairy cattle farms. A total of 120 blood serum samples (60 in each season) and 24 diet samples (12 in each season) were collected in the summer and winter. The Cu, Fe, and Zn contents were assessed in samples using atomic absorption spectrophotometer. In the summer, the mean concentrations of Cu and Fe in serum samples were lower and higher than the critical level, respectively (P < 0.05). In total diet samples, the mean concentrations of Zn were significantly higher than critical level (P < 0.05). In summer, winter, and total diet samples, the mean concentrations of Fe were significantly higher than critical level (P < 0.05). The serum Cu and Zn concentrations were significantly higher in the winter than those determined in the summer (P < 0.05). The serum Cu concentrations were significantly higher in nonpregnant than those in pregnant dairy cattle (P < 0.05). No significant difference was observed in serum Cu, Zn, and Fe concentrations of dairy cattle in different daily milk yield groups. It can be concluded that Holstein dairy cattle reared under semi-industrial dairy farming were deficient in serum Cu concentrations, especially in summer. Further, high level of Fe in blood serum might be due to feeding of cattle with diet containing excess quantity of Fe.