An RNA Vaccine Based on Recombinant Semliki Forest Virus Particles Expressing the Cu,Zn Superoxide Dismutase Protein of Brucella abortus Induces Protective Immunity in BALB/c Mice

Abstract

We constructed infectious but replication-deficient Semliki Forest virus (SFV) particles carrying recombinant RNA encoding Brucella abortus Cu,Zn superoxide dismutase (SOD). The recombinant SFV particles (SFV-SOD particles) were then evaluated for their ability to induce a T-cell immune response and to protect BALB/c mice against a challenge with B. abortus 2308. Intraperitoneal injection of mice with recombinant SFV-SOD particles did not lead to the induction of SOD-specific antibodies, at least until week 6 after immunization (the end of the experiment). In vitro stimulation of splenocytes from the vaccinated mice with either recombinant Cu,Zn SOD (rSOD) or crude Brucella protein resulted in a T-cell proliferative response and the induction of gamma interferon secretion but not interleukin-4. In addition, the splenocytes exhibited significant levels of cytotoxic T-lymphocyte activity against Brucella-infected cells. The SFV-SOD particles, but not the control virus particles, induced a significant level of protection in BALB/c mice against challenge with B. abortus virulent strain 2308. These findings indicated that an SFV-based vector carrying the SOD gene has potential for use as a vaccine to induce resistance against B. abortus infections.Brucella abortus is gram-negative, facultative intracellular bacterial pathogen that causes brucellosis in humans and cattle. In the infected host B. abortus multiplies within the phagosomes of reticuloendothelial cells, avoiding the killing effect of the macrophage cells by inhibiting phagosome-lysosome fusion (22). Like resistance to other facultative intracellular bacterial pathogens, resistance to B. abortus depends on acquired cellmediated immunity (CMI) (51). In this respect, the development of the Th1 subset of CD4 ϩ lymphocytes that secrete gamma interferon (IFN-␥), a crucial cytokine that up-regulates the macrophage anti-Brucella activity, and the development of CD8 ϩ T lymphocytes that are able to lyse Brucella-infected cells (33,34) are the two main components of the protective response. Live, attenuated vaccines, such as B. abortus strains S19 and RB51, that can stimulate a strong CMI response are usually very effective against brucellosis and have been used to control brucellosis in domestic animals. However, these vaccine preparations are far from ideal, since they have disadvantages; e.g., they are considered virulent or unsafe for human use, and they induce abortion in pregnant cattle (43). In the search for methods that can provide immunity against brucellosis, DNA-based vaccines have been shown to be effective for the delivery of antigenic proteins (3, 22) and to generate a strong cellular response (28). In previous reports, we showed that a DNA vaccine encoding the Cu,Zn superoxide dismutase (SOD) protein of B. abortus is able to induce cytotoxic Tlymphocyte (CTL) activity, high levels of IFN-␥ production, and a significant level of protection against challenge with B.abortus virulent strain 2308 in BALB/c mice (30, 37). However, repeated doses and high c...

Vaccination with recombinant Semliki Forest virus particles expressing translation initiation factor 3 of Brucella abortus induces protective immunity in BALB/c mice

“…Perusal of the published literature indicates that the induction of antigen-specific antibodies upon SFV particle immunization appears to be highly variable. In some cases strong antibody response were obtained (Brand et al, 1998;Berglund et al, 1999;Fleeton et al, 2000;Yu et al, 2006), whereas in other cases very weak or no antibody responses were detected (Andersson et al, 2001;Penttila et al, 2004;Koopman et al, 2004;Oñate et al, 2005;Li et al, 2007). Probably the nature of the antigen, the immunization interval and, in some cases, the boosting with recombinant proteins, may influence the outcome of the antibody responses following immunization with recombinant SFV particles.…”

“…The recombinant plasmid, named pSFV-IF3, was electroporated into E. coli DH5a, and a single recombinant colony was selected. The in vitro transcription and packaging of SFV particles was performed under the same protocol described by Oñate et al, 2005. Immunization Mice were immunized by intraperitoneal route with 10 6 infectious units of recombinant SFV-IF3 particles in 200 ml of PBS at day 1 and 21. Mice in the negative control group received PBS only.…”

“…After cell infection by viral particles, RNA replication allows expression of the foreign gene in infected cells, thereby resulting in the induction of strong humoral and CMI (Berglund et al, 1999;Fleeton et al, 1999;Fleeton et al, 2000;Nilsson et al, 2001). Our previous research showed that the recombinant SFV particles containing the gene for Cu-Zn superoxide dismutase of Brucella can induce significant levels of protection in mouse and bovine models of brucellosis (Oñate et al, 2005;Saez et al, 2008). We have previously demonstrated that a 22.9-kDa protein of B. abortus can induce CMI and protection in mice (Céspedes et al, 2000).…”

“…Hence, a vaccine that is not infectious for humans but remains able to stimulate strong protective responses is necessary to control brucellosis. To develop the next generation of Brucella vaccines, several research groups are pursing different strategies including the development of subunit vaccines (Oliveira and Splitter, 1996), utilization of bacterial vectors (Oñate et al, 1999), DNA vaccines (Velikovsky et al, 2002;Al-Mariri et al, 2001;Oñate et al, 2003), and RNA vaccine (Oñate et al, 2005).…”

Sindbis virus replicon particles encoding calreticulin linked to a tumor antigen generate long-term tumor-specific immunity

“…This is particularly important for vaccines targeting proteins that are potentially oncogenic, such as the HPV E6 and E7. In addition, alphavirus-based vaccines have been utilized in the many diseases such as bacterial infection, 15 malignant tumors, 16,17 and viral encephalitis. 18 Alphavirus replicon particle vaccines typically are produced using trans-complementing defective helper constructs that separately express the capsid and envelope glycoproteins from distinct cassettes as a means to minimize the risk of RNA recombination leading to the formation of replication-competent virus (RCV).…”