Table 2 Some examples of M2e-based vaccines

Hepatitis B virus core protein

Mice

IP⁺ or IN

3 immunizations at 3-week intervals with 5, 10, or 50 μg led to the formation of M2e-antibodies in mice. Groups immunized with 10 μg IP and IN in subsequent vaccination studies were protected after challenge with 5 LD₅₀ of A/PR/8/34 (H1N1) and A/Victoria/3/75 (H3N2). The significant role of M2e antibodies in passive transfer experiments was shown.

[88]

Mice

IM⁺

3 immunizations at 2-week intervals with 50 μg induced high levels of M2e-antibodies. Challenge with 5 LD₅₀ of different heterologous viruses showed high degree of protection.

[122]

Modified form of the leucine zipper of the yeast transcription factor GCN4

Mice

IP⁺ or IN⁺

3 immunizations with 10 μg doses led to the formation of specific IgG1 and IgG2a M2e antibodies. The tetrameric M2e-tGCN4 vaccine induced M2e-specific IgG antibody that recognized natural M2 ectodomain. Immunized mice were fully protected against challenge with 4 LD₅₀ X47.

[17]

Prime with M2-DNA and boost with recombinant adenovirus expressing M2

Mice

IM

2 immunizations (50 μg each) led to the enhanced antibody response. Challenge with LD₅₀ of A/PR/8/34 (H1N1) and 10 LD₅₀ of A/FM/1/47-MA (H1N1) and LD₅₀ A/Thailand/SP-83/2004 (H5N1) showed the significant cross-protection of the vaccine. The important protective role of CD4 + and CD8 + cells was also shown.

[119]

T7 bacteriophage nanoparticles

Mice

SC⁺

3 immunizations (10⁹ PFU each) led to the formation of IgG1 and IgG2a M2e-antibodies, as well as a T-cell response. Challenge with 4 LD₅₀ of A/PR/8/34 (H1N1) and X47 showed a high degree of protection.

[38]

Rotavirus fragment NSP4_98–135

Mice

SC⁺

3 immunizations (10 μg each) with a chimeric protein resulted in the formation of an increased level of antibodies compared with immunization with M2e peptides. The formation of IgG1 M2e antibodies and to a lesser extent IgG2a was induced. Challenge using 3 LD₅₀ of A/PR/8/34 (H1N1) or A/equine/London/72 (H7N7) did not reveal significant differences between the chimeric and peptide vaccine, however lung virus titers 3 d.p.i. were significantly lower in the M2e-NSP4 group.

[3]

Keyhole limpet hemocyanin (KLH) or Neisseria meningitides outer membrane protein complex (OMPC)

Mice

SC or IM⁺

3 immunizations (20 μg each) at 4-week intervals led to the formation of high levels of antibodies with cross-reactivity. Challenge with LD₉₀ of A/Hong Kong/68xPR8 reassortant resulted in complete survival and lower weight loss in vaccinated mice compared with controls.

Ferrets

IM⁺

3 immunizations (100 μg each) at 4-week intervals showed that the OMPC-based vaccine was more immunogenic than the KHL-based vaccine. Challenge with 100 TCID₅₀ A/PR/8/34 (H1N1) revealed significantly lower replication of the challenge virus in the nasal turbinates and lungs.

Rhesus monkeys

IM⁺

3 immunizations (10 μg each) during 25 weeks (immunization on 0, 8, and 25 weeks) with an OMPC-based vaccine led to the formation of an increased level of M2e antibodies. Sera were examined after challenge with A/Hong Kong/68xPR8 after passive transfer immunization of mice, and protective efficacy was shown.

Brucella abortus lumazine synthase protein (BLS)

Mice

SC, SC⁺, IM, IM⁺, IN, IN⁺

3 immunizations (10 μg each) using various routes at 3-week intervals led to the formation of IgG1 and IgG2a M2e-antibodies in different ratios. SC+ immunization produced the highest level of antibodies and was chosen for further study. Challenge with 5 LD₅₀ of A/PR/8/34 (H1N1) showed the protective efficacy of the vaccine.

[2]

Malva mosaic virus nanoparticles

Mice

SC⁺

2 immunizations (20 μg each) at a 2-week interval led to the formation of IgG1 and IgG2a M2e-antibodies, whereas immunization with M2e peptides was not immunogenic. Significantly lower replication of the challenge virus in nasal turbinates and lungs was shown after challenge with A/WSN/1933 (H1N1).

Dogs

IM⁺

3 immunizations (80 μg each) at 3-week intervals led to the formation of cross-reactive M2e-antibodies and revealed the need for adjuvant. Challenge was not performed.

H1N1 HA DNA

Mice

IM⁺

2 immunizations (0.2 μg each) at a 3-week interval led to the formation of cross-reactive M2e-antibodies. High protection of immunized mice was shown against challenge with 5 LD₅₀ of A/Aquatic Bird/Korea/W81/2005. In addition, HA-specific CD8+ and M2e-specific T cell responses were elicited

[92]

Salmonella typhimurium flagellin

Mice

SC

3 immunizations (6 μg each) at 3-week intervals led to the formation of a high level of M2e-antibodies. Full protection of vaccinated mice was shown against challenge with 10 LD₅₀ of A/Aichi/2/68 (H3N2).

[113]

Mice

SC or IN

2 immunizations (3 μg each) at a 2-week interval led to the formation of a higher rate of M2e-antibodies than immunization with M2e-peptides. There was no decline in the following 10 months. High protection of immunized mice was shown against challenge with LD₉₀ of A/PR/8/34 (H1N1).

Rabbits

IM

2 immunizations (15 μg each) at a 3-week interval led to the formation of M2e-antibodies.

Multiple antigenic peptide

Mice

SC⁺

Single immunization led to the formation of high levels of M2e antibodies, which insignificantly declined in the following 6 months. 2 immunizations led to significant clearance of virus 3 days after challenge with 10 LD₅₀ A/Beijing/501/09 and protected against weight loss.

[141]

DNA expressing fusion M2e-NP protein

Pigs

SC⁺

3 immunizations (200 μg each) at 3-week intervals did not protect animals after challenge with 10⁸ TCID₅₀ of A/Sw/Best/96 (H1N1) but led to more serious signs of disease compared with the control group.

[41]

Lipopeptides

Mice

SC

2 immunizations (20 nmol each) at a 2-week interval with shortened form of M2e (a.a. 2–16) led to the same level of M2e antibody production as immunization with full-length M2e (a.a. 2–24), and led to lower viral titers in lungs and nasal turbinates after challenge with 10^4.5 PFU of A/Memphis/1/71xA/Bellamy/42 (H3N1) virus.

[94]

Keyhole limpet haemocyanin (KLH with full length M2e (M2e-KLH) and M2e_2–10 (SP1-KHL)

Mice

IP⁺

3 immunizations at 3-week intervals led to the formation of M2e-antibodies for both vaccines. Vaccinated groups were more protected than the control group against challenge with 4 LD₅₀ of A/PR/8/34 (H1N1). M2e-KLH was more immunogenic and protective than SP1-KHL.

Rabbits

n/m

3 immunizations at 3-week intervals showed greater immunogenicity of SP1-KHL. Serum from immunized rabbits provided protection in a mice passive transfer study against challenge with 4 LD₅₀ of A/PR/8/34 (H1N1). SP1-KHL was also more immunogenic in outbred New Zealand white rabbits than in inbred BALB/c mice.

VLP

Mice

IM

2 immunizations at a 4-week interval led to the formation of M2e-antibodies, and protected mice against challenge with 4 LD₅₀ of A/Philippines/2/82(H3N2) 4 weeks and 8 months after boost.

[58]

M13 phage

SPF chickens

IM⁺ (1st), IM (2nd)

2 immunizations with the hybrid phage expressing shortened form of M2e (a.a. 2–9) at a dose of 1 × 10¹⁰ phage/200 μL produced specific antibodies against M2e (2–9) in broiler chickens.

[80]

CTA1-DD

Mice

IN

2 immunizations at 3-week intervals induced strong M2e-specific serum antibody response and stimulated significant anti-M2e IgA antibody titers in bronchial lavage. Vaccination provided strong protective immunity against challenge with 4 LD₅₀ of X47 virus.

[25]

8C6 and 1B12 antibodies (recognize M2e_6–13)

Mice

IP (passive transfer)

Passive transfer with 8C6 and 1B12 led to the formation of a high level of M2e antibodies and 75% protection of vaccinated mice against challenge with 5 LD₅₀ of A/PR/8/34 (H1N1), compared with 0% protection in control group.

[78]

M2e-specific IgG2a MAb65

Mice

IP (passive transfer)

Passive immunization reduced transmission of A/Udorn/72 (H3N2) and A/Hong Kong/68 (H3N2) challenge viruses and led to lower viral titer in lungs and nasal turbinates.

[60]