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bThe conventional hemagglutinin (HA)-and neuraminidase (NA)-based influenza vaccines need to be updated most years and are ineffective if the glycoprotein HA of the vaccine strains is a mismatch with that of the epidemic strain. Universal vaccines targeting conserved viral components might provide cross-protection and thus complement and improve conventional vaccines. In this study, we generated DNA plasmids and recombinant vaccinia viruses expressing the conserved proteins nucleoprotein (NP), polymerase basic 1 (PB1), and matrix 1 (M1) from influenza virus strain A/Beijing/30/95 (H3N2). BALB/c mice were immunized intramuscularly with a single vaccine based on NP, PB1, or M1 alone or a combination vaccine based on all three antigens and were then challenged with lethal doses of the heterologous influenza virus strain A/PR/8/34 (H1N1). Vaccines based on NP, PB1, and M1 provided complete or partial protection against challenge with 1.7 50% lethal dose (LD 50 ) of PR8 in mice. Of the three antigens, NP-based vaccines induced protection against 5 LD 50 and 10 LD 50 and thus exhibited the greatest protective effect. Universal influenza vaccines based on the combination of NP, PB1, and M1 induced a strong immune response and thus might be an alternative approach to addressing future influenza virus pandemics.T he conventional influenza vaccines that are available currently to prevent seasonal flu outbreaks depend mainly on the surface glycoproteins hemagglutinin (HA) and neuraminidase (NA) (1, 2). However, HA-and NA-based conventional influenza vaccines sometimes fail to prevent flu epidemics because the HA and/or NA in the vaccine strains is a mismatch with that in circulating virus strains (3-7). Universal influenza vaccines (UIVs) that induce effective and long-term cross-protection and address the risk of mismatch may overcome the shortcomings of conventional influenza vaccines. Therefore, the development of a UIV capable of inducing long-term immunity and cross-protection remains a priority in influenza vaccine research (8).Influenza viruses are classified as type A, B, or C based on their nucleoprotein (NP) and matrix protein (M). Among the three subtypes, influenza A virus has been the target of UIVs, because the diverse influenza A strains frequently trigger influenza epidemics and pandemics. A previous study indicated that humans mount a good response to the highly conserved internal proteins NP, M1, and polymerase basic 1 (PB1) of influenza A virus (9); therefore, these highly conserved influenza A virus antigens are the basis of UIVs. Multiple studies have investigated the potential of NP (10-13), matrix protein 1 (M1) (14-17), and ion channel (M2, mainly M2e) (18-27) as alternative vaccine antigens for the prevention of seasonal and pandemic flu outbreaks. PB1 has also shown protective potential but requires further investigation for inclusion in UIVs. Košík et al. (28) constructed a DNA vaccine based on PB1, which provided some protective immunity in a mouse model. We previously constructed DNA vaccines ...

The spike (S) glycoprotein of severe acute respiratory syndrome coronavirus (SARS-CoV) is a major target in the development of diagnostic assays and vaccines, but its antigenic and immunogenic properties remain unclear. Seven SARS-CoV spike proteins (S, SQ, S1, RBD, S2, S2Q, and CX) were generated using the modified vaccinia virus (Tiantan strain) as a vector, and their antigenicity and immunogenicity were evaluated. The secreted SQ protein in which the transmembrane domain was deleted, as well as the full-length spike protein, showed the most potential to induce the production of neutralizing antibody (nAb) in mice. S1 and RBD proteins initialized significantly lower levels of nAb production. In addition, the S proteins were recognized specifically by the sera of convalescent patients with SARS, and that of mice immunized with inactivated SARS-CoV, but did not react with anti-sera of HCoV-OC43 or HCoV-229E, or sera from healthy donors (although RBD showed a false-positive in 1 of 55 control samples of human sera). Our results demonstrate that SQ protein may be an effective vaccine candidate and a convenient and safe diagnostic antigen for SARS-CoV.

The structural gene encoding ApxII toxin (apxIIA) was amplified from the genomic DNA of Actinobacillus pleuropneumoniae (APP) strain HB08 (serotype 2) and cloned into the prokaryotic expression vector pET-28a. SDS-PAGE and Western blot analysis showed that the apxIIA gene was expressed in Escherichia coli BL21 (DE3) and the expressed products could react with ApxII antibodies. The recombinant ApxIIA was purified from the inclusion bodies. Kunming mice were intraperitoneally vaccinated twice, with an interval of 2 weeks, using unfolded/refolded recombinant proteins, the native ApxII toxin extracted from the cultural supernatant of a strain of APP serotype 7 (APP-7) or phosphate-buffered saline (PBS). Serum antibody was examined by ApxIIA-specific enzyme-linked immunosorbent assay (ELISA) 2 weeks after every vaccination. Two weeks after the second vaccination, mice were challenged intraperitoneally with a lethal dose of APP-7 (1.08 r 10 8 cfu per mouse). The protection rate reached 91.7% in the native ApxII group, 83.3% in the refolded recombinant protein group and 58.3% in the unfolded recombinant protein group, while all mice in the PBS group died within 36 h after challenge. Our data revealed that the refolded recombinant ApxIIA had excellent immunogenicity and could elicit protection against a lethal challenge of APP.