Poxvirus as Vaccine-vectors

Poxvirus vectors are one of the most commonly used viral vectors for the development of preventive vaccines against infectious diseases and therapeutic cancer vaccines. These vectors are typically attenuated or engineered to safely deliver genes encoding antigens of different pathogens. Creative Biolabs has mass-produced and purified poxvirus vectors through mature cell culture technology to meet the needs of various applications, greatly promoting the development of new vaccine vectors.

Background of Poxvirus

Poxviruses, which are from the Poxviridae family and more specifically the Chordopoxvirinae subfamily, contain linear double-stranded DNA genomes and have a relatively narrow host range and morphology is similar for all species in the subfamily. Poxvirus is considered one of the most promising vectors for vaccines against a variety of infectious pathogens, including malaria, tuberculosis, HIV, and cancer. Poxvirus immunomodulatory proteins provide a broad rationale for the development of novel therapeutic agents for the treatment of chronic inflammation and autoimmune diseases in humans. From these aspects, of greatest interest are the closely related viruses of the genus Orthopoxvirus.

Poxvirus as Vaccine-vectors

One of the main features of poxvirus is that a large number of exogenous DNA sequences can be inserted into their genome, allowing them to serve as vectors for heterologous gene sequences encoding several pathogens (e.g., parasites, bacteria, and virus), antigens of tumor cells or other foreign sequences. Therefore, they are ideal vectors to be used as recombinant poxvirus vaccines. Attenuated vaccinia viruses such as Modified Vaccinia virus Ankara (MVA) and NYVAC, or avipoxviruses such as canarypox virus and fowlpox viruses are used as backbones to produce recombinant poxvirus vaccines. These backbone viruses have favorable properties including acceptable safety profiles in animals and/or humans, proven immunogenicity as a vaccine without the need for adjuvants and established procedures for large-scale production.

Common Types of Poxvirus Vector

Modified Vaccinia virus Ankara (MVA), derived from the parental Chorioallantois Vaccinia virus Ankara (CVA) by more than 570 passages in chicken embryo fibroblast (CEF) cells, is now considered an attractive and promising candidate viral vector for the expression of foreign genes of interest because of its unique properties.
NYVAC is an attenuated derivative of the VACV strain Copenhagen (CopV), produced by the specific deletion of 18 ORFs from the genome of the parental virus, involved in host range, virulence and pathogenesis, NYVAC provides a high level of foreign gene expression and efficiently triggers specific immune responses to these antigens in both experimental animals and humans. NYVAC-derived vectors are able to express antigens from a broad range of species and have been used as recombinant vaccines against numerous pathogens and tumors
ALVAC, generated by serial passages in CEF, is a plaque-purified clone derived from an attenuated canarypox virus. ALVAC is significantly different from MVA in terms of genome size (approximately 365 kbp versus approximately 178 kbp, respectively) and the number of open readings (ORFs). Many ALVAC ORFs may not function in mammalian cells, such as fowlpox virus, which cannot replicate in mammalian cells, and this feature may underlie its improved safety profile as a vaccine vector.

Advantages of Poxvirus Vectors

The use of recombinant poxvirus as an ideal vaccine vector has several advantages:

Packing flexibility of the genome
Lack of persistence or genomic integration in the host due to their cytoplasmic replication
Ability to induce both antibody and cytotoxic T cell responses against the heterologous antigens with long-lasting immunity
Thermostability of freeze-dried vaccine, low cost, and ease of manufacture and administration
Low prevalence of anti-vector immunity in the global population due to the interruption of smallpox vaccination in the 1970s following its eradication

Methods for Improving Immunogenicity of Poxvirus Vector

In addition to some conventional poxvirus vectors, Creative Biolabs offers a variety of methods to enhance the immunogenicity of poxvirus vectors, including the following:

Heterologous priming/boosting protocols
The use of costimulatory molecules
The absence of viral immunoregulatory genes in the poxvirus genome
Enhanced viral promoter strength
Optimization of expression of exogenous heterologous sequences
The combined use of adjuvants.

Poxviral vectors form a prominent platform for the development of vaccines that induce T cell immunity against various infectious agents and tumor antigens. Creative Biolabs has sought an optimized poxvirus vector in a variety of ways that can elicit long-acting immunity with high protective efficacy against selective diseases. If you are interested in any of the poxvirus vectors, please feel free to contact us.

All of our products can only be used for research purposes. These vaccine ingredients CANNOT be used directly on humans or animals.