Four-gene-combination DNA vaccine protects mice against a lethal vaccinia virus challenge and elicits appropriate antibody responses in nonhuman primates

Abstract

Two major infectious forms of vaccinia virus (VACV) have been described: the intracellular mature virion (IMV), and the extracellular enveloped virion (EEV). Due to their stability in the environment, IMVs play a predominant role in host-to-host transmission, whereas EEVs play an important role in dissemination within the host. In a previous report, we demonstrated that mice vaccinated with VACV L1R (IMV immunogen) and A33R (EEV immunogen) were protected from a lethal poxvirus challenge. Vaccination with a combination of both genes conferred greater protection than either gene alone, suggesting that an immune response against both IMV and EEV is advantageous. Here, we report that in mice individually administered DNA vaccines with two different VACV immunogens, A27L (IMV immunogen) or B5R (EEV immunogen), failed to significantly protect; however, vaccination with a combination of both genes conferred a high level of protection. Mice were completely protected when vaccinated with a combination of four VACV genes (A27L + A33R + L1R + B5R). Rhesus macaques vaccinated with this four-gene-combination developed appropriate antibody responses to each protein. Antibody responses elicited by this vaccine cross-reacted with monkeypox virus orthologous proteins. These data indicate that a gene-based vaccine comprised of the VACV A27L + A33R + L1R + B5R genes may be a useful candidate to protect against other orthopoxviruses, including those that cause monkeypox and smallpox.

Differential efficacy of vaccinia virus envelope proteins administered by DNA immunisation in protection of BALB/c mice from a lethal intranasal poxvirus challenge

“…Consistent sero-conversion was obtained with all four DNA vaccines studied by [17,18] and strong neutralising antibody titres were achieved for A27L and L1R, which implies that gene-gun administration improves the humoral immune response. The gene gun injects DNA efficiently into subcutaneous tissues, where dendritic cells may be expected to encounter the DNA and any antigen that is produced from it.…”

“…In our own study, and that of [16] immunisation was by intramuscular injection. This places the antigen source in an immunologically different environment to that used by Hooper et al [17,18] and this may be a significant factor in the differential induction of antibody, and survival post-challenge in the three studies.…”

“…Hooper et al [17,18] looked at the individual and the combined effects of A27L, A33R, L1R and B5R by gene-gun immunisation in a challenge model that used 5×10 8 pfu VACV (WR strain) cell lysate (12 LD 50 ) administered by the intraperitoneal route. After three gene-gun immunisations with 0.5-1 g of DNA, only 10% of A27L, 40% of B5R [18] and 70% of A33R [17] DNA vaccine recipients survived the challenge. The A27L gene product (p14k fusion protein) stimulates neutralising antibody in the context of an infection with live VACV.…”

A protein-based smallpox vaccine protects mice from vaccinia and ectromelia virus challenges when given as a prime and single boost

“…While the current licensed live vaccinia virus-based vaccine is extremely effective [3] and results in remarkably long-lived immune responses (e.g., [4]), it has an unacceptable safety profile [5,6] for wide use when considered in today's setting of global eradication of active smallpox disease. Approaches to develop safer smallpox vaccines have ranged from the study of more attenuated live vaccinia viruses (such as MVA [7][8][9] or LC16m8 [10,11]) to subunit vaccines that rely on specific viral targets delivered either as DNA plasmids [12][13][14][15] or purified proteins [16][17][18][19].…”

“…Some key targets on the EV envelope that are important for protection are encoded by the A33R [29] and B5R [30,31] genes. Because the viral proteins present on MV and EV envelopes differ, there is rationale and evidence [12][13][14]17] to include proteins from both virion forms to confer maximal protection. Theoretically, antibody responses to MV proteins could neutralize some of the initial infecting inoculum, while antibodies to EV targets would then limit spread of the progeny virus within the infected host.…”