Alexander N. Zakhartchouk

Mucosal immunization of calves with recombinant bovine adenovirus-3: induction of protective immunity to bovine herpesvirus-1

To determine the potential of replication-competent (E3-deleted) bovine adenovirus-3 (BAV-3) as a delivery system for vaccine antigens in calves, we evaluated the ability of recombinant BAV-3 expressing different forms of of bovine herpesvirus-1 (BHV-1) glycoprotein gD to protect against BHV-1 infection in calves that had pre-existing BAV-3 specific antibodies. Three- to four-month-old calves, vaccinated intranasally with recombinant BAV-3 expressing full-length gD (BAV3.E3gD) or a truncated version of gD (gDt) (BAV3.E3gDt), or with E3-deleted BAV-3 (BAV3.E3d; control), were challenged with BHV-1 strain 108. Vaccination with BAV3.E3gD or BAV3.E3gDt induced gD-specific antibody responses in serum and nasal secretions, and primed calves for gD-specific lymphoproliferative responses. In addition, all calves developed complement-independent neutralizing antibodies against BHV-1. Protection against viral challenge was observed in calves vaccinated with recombinant BAV3.E3gD or BAV3.E3gDt as shown by a significant reduction in body temperature and clinical disease, and a partial reduction in the amount and duration of virus excretion in nasal secretions. These results indicate that replication-competent BAV-3-based vectors can induce protective immune responses in calves (the natural host) that have pre-existing BAV-3-specific antibodies.

Augmentation of immune responses to SARS coronavirus by a combination of DNA and whole killed virus vaccines

Abstract We studied the immunogenicity of a DNA SARS-vaccine, a whole killed virus, or a whole killed and DNA vaccine combination. The DNA vaccine contained a plasmid encoding the SARS coronavirus (SARS-CoV) S protein under the control of the human CMV promoter and intron A. The whole killed virus vaccine was comprised of SARS-CoV, propagated in Vero-E6 cells, with subsequent β-propilactone inactivation and formulated with aluminum hydroxide adjuvant. Mice immunized twice with the DNA vaccine and once with the whole killed virus elicited higher antibody responses than mice immunized three times with the DNA vaccine or once with the whole killed virus vaccine. Mice immunized twice with the whole killed virus vaccine elicited higher antibody responses than mice immunized three times with the DNA vaccine or once with the whole killed virus vaccine. However, a combination of the vaccines induced T-helper type 1 (Th1) immune responses while the whole killed virus vaccine induced T helper type 2 (Th2) immune response. These results demonstrate that combination of the DNA vaccine and the whole killed virus vaccine can be used to enhance the magnitude and change the bias of the immune responses to SARS-CoV.

The immunogenicity and efficacy of replication-defective and replication-competent bovine adenovirus-3 expressing bovine herpesvirus-1 glycoprotein gD in cattle.

Replication-competent and replication-defective bovine adenovirus type 3 recombinants expressing the bovine herpesvirus type 1 (BHV-1) glycoprotein D (gD) were tested for induction of gD specific immune responses in calves using intratracheal (1st and 2nd immunization) and sub-cutaneous (3rd immunization) route of immunization. The replication-defective recombinant BAV501 induced systemic immune responses against gD as low titers of anti gD-IgG were detected in the serum. However, the efficacy of the replication-competent BAV3.E3gD to induce gD-specific antibodies in the serum and the nasal secretions was superior to that of replication-defective BAV501 when both viruses were given at the same dosage. Partial protection from challenge was induced in calves immunized with replication-competent BAV3.E3gD. A dramatic increase in the titers of anti-gD IgG and IgA levels, both in serum and nasal secretions, following BHV-1 challenge (anamnestic response) suggested that the animals immunized with replication-defective BAV501 had been primed for gD-specific antibody responses.

Immunogenicity of a receptor-binding domain of SARS coronavirus spike protein in mice: Implications for a subunit vaccine

Abstract We studied the immunogenicity of an anti-SARS subunit vaccine comprised of the fragment of the SARS coronavirus (SARS-CoV) spike protein amino acids 318–510 (S318–510) containing the receptor-binding domain. The S protein fragment was purified from the culture supernatant of stably transformed HEK293T cells secreting a tagged version of the protein. The vaccine was given subcutaneously to 129S6/SvEv mice in saline, with alum adjuvant or with alum plus CpG oligodeoxynucleotides (ODN). Mice immunized with the adjuvanted antigen elicited strong antibody and cellular immune responses; furthermore, adding the CpG ODN to the alum resulted in increased IgG2a antibody titers and a higher number of INF-γ-secreting murine splenocytes. Mice vaccinated with S318–510 deglycosylated by PNGase F (dgS318–510) showed a lower neutralizing antibody response but had similar numbers of INF-γ-producing cells in the spleen. This finding suggests that carbohydrate is important for the immunogenicity of the S318–510 protein fragment and provide useful information for designing an effective and safe SARS subunit vaccine.

A recombinant E1-deleted porcine adenovirus-3 as an expression vector.

Replication-defective E1-deleted porcine adenoviruses (PAVs) are attractive vectors for vaccination. As a prerequisite for generating PAV-3 vectors containing complete deletion of E1, we transfected VIDO R1 cells (fetal porcine retina cells transformed with E1 region of human adenovirus 5) with a construct containing PAV-3 E1B(large) coding sequences under the control of HCMV promoter. A cell line named VR1BL could be isolated that expressed E1B(large) of PAV-3 and also complemented PAV214 (E1A+E1B(small) deleted). The VR1BL cells could be efficiently transfected with DNA and allowed the rescue and propagation of recombinant PAV507 containing a triple stop codon inserted in the E1B(large) coding sequence. In addition, recombinant PAV227 containing complete deletion of E1 (E1A+E1B(small) + E1B(large)) could be successfully rescued using VR1BL cell line. Recombinant PAV227 replicated as efficiently as wild-type in VR1BL cells but not in VIDO R1 cells, suggesting that E1B(large) was essential for replication of PAV-3. Next, we constructed recombinant PAV219 by inserting green fluorescent (GFP) protein gene flanked by a promoter and a poly(A) in the E1 region of the PAV227 genome. We demonstrated that PAV219 was able to transduce and direct expression of GFP in some human cell lines.

Vaccines for porcine epidemic diarrhea virus and other swine coronaviruses.

Abstract The recent introduction of the porcine epidemic diarrhea virus (PEDV) into the North American swine herd has highlighted again the need for effective vaccines for swine coronaviruses. While vaccines for transmissible gastroenteritis virus (TGEV) have been available to producers around the world for a long time, effective vaccines for PEDV and deltacoronaviruses were only recently developed or are still in development. Here, we review existing vaccine technologies for swine coronaviruses and highlight promising technologies which may help to control these important viruses in the future.

Role of phosphatidylinositol-3-kinase (PI3K) and the mammalian target of rapamycin (mTOR) signalling pathways in porcine reproductive and respiratory syndrome virus (PRRSV) replication.

Porcine Reproductive and Respiratory Syndrome Virus (PRRSV) is a positive sense, single-stranded RNA genome virus that has become a major infection in swine, exerting huge economic losses to the industry worldwide. Detailed knowledge concerning the molecular mechanisms by which the virus manipulates the host cell signals transduction machinery is not only critical to further our understanding of viral replication and pathogenesis, but also guides our efforts to design new and improved therapeutic strategies. The phosphatidylinositol-3-kinase (PI3K)-dependent Akt and the mammalian target of rapamycin (mTOR) (PI3K/Akt/mTOR) are major host cell signalling pathways that regulate protein synthesis, cell growth, proliferation, migration and survival. It is also established that many viruses exploit these signalling cascades for their own benefit, driving viral protein expression, replication, as well as the suppression of the hosts antiviral activities. In this article, we will review the role of these signalling pathways during PRRSV replication, and discuss some of our recent findings implicating mTOR.

Intracellular localization of the SARS coronavirus protein 9b: Evidence of active export from the nucleus

Abstract Open reading frame 9b (ORF 9b) encodes a 98 amino acid group-specific protein of severe acute respiratory syndrome (SARS) coronavirus (CoV). It has no homology with known proteins and its function in SARS CoV replication has not been determined. The N-terminal part of the 9b protein was used to raise polyclonal antibodies in rabbits, and these antibodies could detect 9b protein in infected cells. We analyzed the sub-cellular localization of recombinant 9b protein using fluorescence microscopy of live transfected cells and indirect immunofluorescence of transfected fixed cells. Our findings indicate that the 9b protein is exported outside of a cell nucleus and localizes to the endoplasmic reticulum. Our data also suggest that the 46-LRLGSQLSL-54 amino acid sequence of 9b functions as a nuclear export signal (NES).

Mucosal adenovirus-vectored vaccine for measles

Several problems associated with the available anti-measles vaccine emphasize the need for a single shot anti-measles vaccine which is efficacious by mucosal route of administration and functional in the presence of anti-measles neutralizing antibodies. To achieve these goals, we constructed two recombinant human adenoviruses (collectively designated Ad-F/H) carrying genes for measles virus (MV) fusion (F) and haemagglutinin (H) proteins. Single intranasal or intramuscular vaccination of mice and cotton rats with Ad-F/H elicited high MV-specific serum neutralizing-antibody titers. Furthermore, bronchoalveolar lavage samples from mice vaccinated intranasally with Ad-F/H showed a 100-fold increase in MV-specific IgA titers compared with intramuscularly vaccinated mice. Moreover, Ad-F/H vaccine administered intranasally, but not intramuscularly, completely protected challenged cotton rats from MV replication in the lungs.

Potential role of porcine reproductive and respiratory syndrome virus structural protein GP2 in apoptosis inhibition.

Porcine reproductive and respiratory syndrome virus (PRRSV) is a serious threat to the pork industry, and its pathogenesis needs further investigations. To study the role of two structural proteins of PRRSV in virus-host cells interactions, two stable cell lines (MARC-2a and MARC-N) expressing GP2 and N proteins, respectively, were established. We induced apoptosis in these cells by treating them with staurosporine and found a significant reduction in the number of apoptotic cells in MARC-2a as compared to MARC-N and MARC-145 cells. In addition, we found significantly higher activities of transcriptional factors (NF-κB and AP-1) in both cell lines as compared to MARC-145 (parent cells). Overall, our data suggest that, although both stable cell lines activate NF-κB and AP-1, GP2 triggers the antiapoptotic process through an intermediate step that needs to be further investigated.