High-yield transgenic mammalian expression system for generating virus-like particles

1. A method of preparing an influenza virus-like particle (VLP), the method comprising:

obtaining a founder Vero cell stably transfected with a sequence encoding an influenza M1 and a sequence encoding an influenza M2;

transfecting the Vero cells with one or more recombinant DNA molecules, which collectively encoding a first influenza hemagglutinin (HA) and a first influenza neuraminidase (NA)

to obtain a first co-expression Vero cell that expresses the influenza M1, the influenza M2, the first influenza HA, and the first influenza NA, wherein the expressions of the influenza M1, M2, HA and NA proteins in the first co-expression Vero cell are controlled by one or more inducible expression systems;

culturing the first co-expression Vero cell under conditions to allow expressions of the influenza M1, the influenza M2, the first influenza HA and the first influenza NA, and assembly of the VLP comprising the influenza M1, the influenza M2, the first influenza HA and the first influenza NA, wherein the VLP lacks viral genetic materials; and

isolating the VLP from the culture supernatant of the first co-expression Vero cell.

2. The method according to claim 1 , wherein the founder Vero cell is a Vero E6 cell.

3. The method according to claim 1 , wherein the influenza HA and the influenza NA are of one or more pandemic or seasonal influenza virus strains.

4. The method according to claim 1 , wherein

the first co-expression Vero cell is further transfected with one or more recombinant DNA molecules, which collectively encode a second influenza HA and a second influenza NA to form a second co-expression Vero cell, wherein the first influenza HA and the second influenza HA are of different influenza virus strains, and the first influenza NA and the second influenza NA are of different influenza virus strains; and

culturing the second co-expression Vero cell to express the influenza M1, the influenza M2, the first influenza HA, the first influenza NA, the second influenza HA and the second influenza NA, and assembly of the VLP comprising the influenza M1, the influenza M2, at least one of the first influenza HA and the second influenza HA, and at least one of the first influenza NA and the second influenza NA.

5. An influenza virus-like particle (VLP), comprising:

an influenza M1, an influenza M2, a first influenza hemagglutinin (HA) and a second influenza neuraminidase (NA), wherein the influenza proteins are recombinantly expressed from a Vero cell; and

at least one cellular protein of the Vero cell;

wherein the VLP lacks viral genetic materials.

6. The influenza VLP of claim 5 , wherein the Vero cell is Vero E6 cell.

7. The influenza VLP of claim 5 , wherein the first influenza HA and the first influenza NA are of one or more pandemic or seasonal influenza virus strains.

8. The influenza VLP of claim 5 , further comprising a second influenza HA and a second influenza NA, wherein the first influenza HA and the second influenza HA are of different influenza virus strains, and the first influenza NA and the second influenza NA are of different influenza virus strains.

9. The influenza VLP of claim 5 , comprising M1 and M2 of influenza A/Taiwan/083/2006, and H3 and N2 of influenza A/Taiwan/083/2006, or H5 and N1 of influenza A/Hanoi/30408/2005(H5N1), respectively.

10. The influenza VLP of claim 5 , wherein the at least one cellular protein is selected from the group consisting of clathrin heavy chain 1, spectrin beta, plexin B2, CD109 homolog, prostaglandin F2 receptor negative regulator, Na+/K+-ATPase alpha 1, tumor rejection antigen (gp96) 1 and flotillin I.

11. An immunogenic composition comprising an immunogenic effective amount of the influenza VLP of claim 5 and a pharmaceutically acceptable excipient.

12. The immunogenic composition of claim 11 further comprising an adjuvant.

13. A method of inducing immunity against an influenza virus in a subject, the method comprising administering to the subject the immunogenic composition of claim 11 .

14. A method of providing protection against an influenza virus in a subject, the method comprising vaccinating the subject with a vaccine comprising the influenza VLP of claim 5 .

15. A method of diagnosing infection by an influenza virus in a subject, the method comprising:

obtaining a biological sample from the subject;

contacting the biological sample with the influenza VLP of claim 5 , wherein the influenza VLP comprises the HA and the NA derived from the influenza virus; and

measuring in the biological sample the amount of an antibody that forms an antibody-antigen complex with the influenza VLP,

wherein a higher than a threshold amount of the antibody indicates that the subject has ever been infected by the influenza virus or vaccinated by a similar strain of virus.