Immune Response to Marburg Virus Angola Infection in Nonhuman Primates.

BACKGROUND: The 2005 outbreak of Marburg virus (MARV) infection in Angola was the most lethal MARV infection outbreak in history, with a case-fatality rate (90%) similar to that for Zaire ebolavirus (EBOV) infection. However, very little is known about the pathogenicity of MARV Angola, as few studies have been conducted to date. Therefore, the immune response was examined in MARV Angola-infected nonhuman primates. METHODS: Cynomolgus macaques were infected with MARV Angola and monitored for survival. The effect of MARV Angola on the immune system was examined by immunophenotyping whole-blood and by analyzing cytokine and chemokine levels in plasma and spleen specimens, using flow cytometry. RESULTS: The prominent clinical findings were rapid onset of disease and death (mean time after infection, 6.7 days), fever, depression, anorexia, petechial rash, and lymphopenia. Specifically, T, B, and natural killer cells were severely depleted in the blood by day 6. The typical cytokine storm was present, with levels of interferon γ, tumor necrosis factor, interleukin 6, and CCL2 rising in the blood early during infection. CONCLUSIONS: MARV Angola displayed the same virulence and disease pathology as EBOV. MARV Angola appears to cause a more rapid onset and severe outcome of infection than other MARV strains.

Characterization of Zaire ebolavirus glycoprotein-specific monoclonal antibodies.

Zaire ebolavirus (ZEBOV) can be transmitted by human-to-human contact and causes acute haemorrhagic fever with case fatality rates up to 90%. There are no effective therapeutic or prophylactic treatments available. The sole transmembrane glycoprotein (GP) is the key target for developing neutralizing antibodies. In this study, recombinant VSVΔG/ZEBOVGP was used to generate monoclonal antibodies (MAbs) against the ZEBOV GP. A total of 8 MAbs were produced using traditional hybridoma cell fusion technology, and then characterized by ELISA using ZEBOV VLPs, Western blotting, an immunofluorescence assay, and immunoprecipitation. All 8 MAbs worked in IFA and IP, suggesting that they are all conformational MAbs, however six of them recognized linearized epitopes by WB. ELISA results demonstrated that one MAb bound to a secreted GP (sGP 1-295aa); three bind to a part of the mucin domain (333-458aa); three MAbs recognized epitopes on the C-terminal domain of GP1 (296-501aa); and one bound to full length GP (VLPs/GP1,2 ΔTm). Using a mouse model these MAbs were evaluated for their therapeutic capacity during a lethal infection. All 8 MAb improved survival rates by 33%-100% against a high dose lethal challenge with mouse-adapted ZEBOV. This work has important implications for further development of vaccines and immunotherapies for ZEBOV infection.

Ebola GP-specific monoclonal antibodies protect mice and guinea pigs from lethal Ebola virus infection.

Ebola virus (EBOV) causes acute hemorrhagic fever in humans and non-human primates with mortality rates up to 90%. So far there are no effective treatments available. This study evaluates the protective efficacy of 8 monoclonal antibodies (MAbs) against Ebola glycoprotein in mice and guinea pigs. Immunocompetent mice or guinea pigs were given MAbs i.p. in various doses individually or as pools of 3-4 MAbs to test their protection against a lethal challenge with mouse- or guinea pig-adapted EBOV. Each of the 8 MAbs (100 µg) protected mice from a lethal EBOV challenge when administered 1 day before or after challenge. Seven MAbs were effective 2 days post-infection (dpi), with 1 MAb demonstrating partial protection 3 dpi. In the guinea pigs each MAb showed partial protection at 1 dpi, however the mean time to death was significantly prolonged compared to the control group. Moreover, treatment with pools of 3-4 MAbs completely protected the majority of animals, while administration at 2-3 dpi achieved 50-100% protection. This data suggests that the MAbs generated are capable of protecting both animal species against lethal Ebola virus challenge. These results indicate that MAbs particularly when used as an oligoclonal set are a potential therapeutic for post-exposure treatment of EBOV infection.

Mucosal immunization of cynomolgus macaques with the VSVDeltaG/ZEBOVGP vaccine stimulates strong ebola GP-specific immune responses.

BACKGROUND: Zaire ebolavirus (ZEBOV) produces a lethal viral hemorrhagic fever in humans and non-human primates. METHODOLOGY/PRINCIPAL FINDINGS: We demonstrate that the VSVDeltaG/ZEBOVGP vaccine given 28 days pre-challenge either intranasally (IN), orally (OR), or intramuscularly (IM) protects non-human primates against a lethal systemic challenge of ZEBOV, and induces cellular and humoral immune responses. We demonstrated that ZEBOVGP-specific T-cell and humoral responses induced in the IN and OR groups, following an immunization and challenge, produced the most IFN-gamma and IL-2 secreting cells, and long term memory responses. CONCLUSIONS/SIGNIFICANCE: We have shown conclusively that mucosal immunization can protect from systemic ZEBOV challenge and that mucosal delivery, particularly IN immunization, seems to be more potent than IM injection in the immune parameters we have tested. Mucosal immunization would be a huge benefit in any emergency mass vaccination campaign during a natural outbreak, or following intentional release, or for mucosal immunization of great apes in the wild.