Mammalian virus vectors

Do you know papova virus ?

The first animal vector was devised from the primate named papova virus and siman Virus 40 as we know ( SV40); this virus user in 1979 for cloning. But according to time virus are subsequently developed  into many other viruses for example

1-Papilloma virus 

2-Adenovirus ( this virus have so many derivatives)

3-The Epstein Barr herpes virus ( derived from herpes virus)

4-Vaccinia virus (used for all mammals)

5- Baculoviruses (for inserts) 

During 1990s mammalian artificial chromosomes as this name as (MACs) and human artificial chromosomes we can say (HACs) have been developed for human wellfare

SV40 vectors

As we know this vector have several uses as vectors. It is found in spherical shape with circular and double - stranded 5,243 base pair chromosome. Which coded with 5 proteins as 

Small-T, large-T , VP1 , VP2 and VP3 

Small-T large-T are both early proteins and these VP(1,2,3) are virions protein. These has an origin of replication and it is complexed with histone to form chromatin and we can say the virus protein incoded with protein function. Where Large-T is essential for viral replication while VP1(1,2,3) form the viral capsid. 

 Culture 

For culture it is multiplied I'm kidney cells of African green money in the laboratory. Due to that the infected cells lyse after 4days . It's realised 5000 times of virions or we can say cells. 

Types of SV40 genome

 

The types of SV40 has been developed mainly three types:-

1 transducing vectors

2 transforming vectors

3 plasmid vectors

Transducing SV40 vectors

As we know this vectors use by infecting monkey cells. After infecting monkey cells these vectors produce some viral particles and with this the have three features:- 

(1) the transcriptional regulatory signals containing arround the SV40 origin region and there surrounding regions. 

(2) total size between 3,900bp and 5,300bp for packaging into virions 

(3) gene coding with large -T , VP1, VP2, abd VP3.

Late region replacement vectors

Late region replacement vectors are those region which encoding VP1,VP2 and VP3 are replaced in the vectors by DNA inserting. e.g SVGT-5 . 

The SVGT-5 is the an improved SV40 vectors. As we know the all viruses which we used as a vectors the more and more verified Verity are regenerated from them . And they used as more profitable way. 

And same as above this kind of these vector contain following things -

(1) the origin of replication (with easy way)

(2) the region where the splicing and poly-adenylation Is occur

(3) the entire early region of SV40 genome.

Helper Virus  these kind of above virus is used for infection the host cells in conjunction with another Virus is called helper Virus. In this virus has the VP1, VP2, VP3 genes intact but has a defective large -T gene. 

In additional knowledge why late region replacement vectors used?

So this is used to study post transcriptional RNA processing and stability. In some cases the presence of an intron in the late - region primary transcript was necessary , for the production of cytoplasmic mRNA .

Early replacement vectors

If we can say , the early genes missing from the vector may be present within the genome of host cells e.g COS which is CV-1 , origin of SV40. And CV-1 is a monkey cell line of African green monkey kidney cell cultures contains in its genome. 

Therefore, the origin of replication will replicate and produce virions in COS cell line. In such cases no helper Virus is required as above case.

In this case early genes such as Large -T are replaced by the DNA insert is called early -region replacement vector.