Minimal in vivo efficacy of iminosugars in a lethal Ebola virus guinea pig model

The antiviral properties of iminosugars have been reported previously in vitro and in small animal models against Ebola virus (EBOV); however, their effects have not been tested in larger animal models such as guinea pigs. We tested the iminosugars N-butyl-deoxynojirimycin (NB-DNJ) and N-(9-methoxynonyl)-1deoxynojirimycin (MON-DNJ) for safety in uninfected animals, and for antiviral efficacy in animals infected with a lethal dose of guinea pig adapted EBOV. 1850 mg/kg/day NB-DNJ and 120 mg/kg/day MON-DNJ administered intravenously, three times daily, caused no adverse effects and were well tolerated. A pilot study treating infected animals three times within an 8 hour period was promising with 1 of 4 infected NB-DNJ treated animals surviving and the remaining three showing improved clinical signs. MON-DNJ showed no protective effects when EBOV-infected guinea pigs were treated. On histopathological examination, animals treated with NB-DNJ had reduced lesion severity in liver and spleen. However, a second study, in which NB-DNJ was administered at equally-spaced 8 hour intervals, could not confirm drug-associated benefits. Neither was any antiviral effect of iminosugars detected in an EBOV glycoprotein pseudotyped virus assay. Overall, this study provides evidence that NB-DNJ and MON-DNJ do not protect guinea pigs from a lethal EBOV-infection at the dose levels and regimens tested. However, the one surviving animal and signs of improvements in three animals of the NB-DNJ treated cohort could indicate that NB-DNJ at these levels may have a marginal beneficial effect. Future work could be focused on the development of more potent iminosugars

Protective effects of a Modified Vaccinia Ankara-based vaccine candidate against Crimean-Congo Haemorrhagic Fever virus require both cellular and humoral responses.

Crimean-Congo Haemorrhagic Fever (CCHF) is a severe tick-borne disease, endemic in many countries in Africa, the Middle East, Eastern Europe and Asia. There is no approved vaccine currently available against CCHF. The most promising candidate, which has previously been shown to confer protection in the small animal model, is a modified Vaccinia Ankara virus vector expressing the CCHF viral glycoprotein (MVA-GP). It has been shown that MVA-GP induces both humoral and cellular immunogenicity. In the present study, sera and T-lymphocytes were passively and adoptively transferred into recipient mice prior to challenge with CCHF virus. Results demonstrated that mediators from both arms of the immune system were required to demonstrate protective effects against lethal challenge

Normalised viral load analysis of CCHFv RNA by RT-PCR.

<p>A129 mice vaccinated with MVA-1974, MVA-GP or which received sera, CD3⁺ T cells, or both from MVA-GP immunised animals were challenged with CCHFv either 14 days after the booster vaccination or 1 day after transfer of immune mediators. Four days post-challenge, three randomly selected animals from each group were killed humanely and analysed by RT-PCR for levels of CCHFv gene expression (normalised to mouse HPRT gene expression). Each point represents the mean value of triplicate measurements in an individual animal. Lines show mean values and error bars denote standard error.</p

Measurement of antibody binding to CCHF virus Gn protein from mice immunised with MVA-GP.

<p>The absorbance readings from an ELISA assay using the Gn protein as antigen were plotted from all individual donor animals (n = 36). A control antibody preparation from a mouse hybridoma cell line developed against the Gn protein was used as a positive control. The error bar denotes the mean and standard error. The dotted line represents the cut-off level based on mean absorbance + 2 standard deviations of unvaccinated guinea pig control sera.</p

Weight changes, temperature changes and clinical signs of A129 mice vaccinated with MVA-1974, MVA-GP or which received sera, CD3⁺ T cells, or both from MVA-GP immunised animals after challenge with CCHF virus.

<p>(A) Weight changes were assessed as percentage change compared to the day of challenge. (B) Temperature changes were analysed as the °C difference compared to the day of challenge. (C) Clinical score was a numerical value based on signs recorded each morning of the study. Symbols show the mean value from all surviving animals from each group alive at that time (n = 6 per group challenged with CCHF virus) and error bars denote the standard error.</p

Normalised viral load analysis of CCHFv RNA by RT-PCR.

<p>A129 mice vaccinated with MVA-1974, MVA-GP or which received sera, CD3⁺ T cells, or both from MVA-GP immunised animals were challenged with CCHFv either 14 days after the booster vaccination or 1 day after transfer of immune mediators. Four days post-challenge, three randomly selected animals from each group were killed humanely and analysed by RT-PCR for levels of CCHFv gene expression (normalised to mouse HPRT gene expression). Each point represents the mean value of triplicate measurements in an individual animal. Lines show mean values and error bars denote standard error.</p

Severity of microscopic lesions and presence of viral antigen in tissues from vaccinated and recipient mice 3 days post-challenge with CCHFv.

<p>Severity of microscopic lesions and presence of viral antigen in tissues from vaccinated and recipient mice 3 days post-challenge with CCHFv.</p

Survival of A129 mice vaccinated with MVA-1974, MVA-GP or which received sera, CD3⁺ T cells, or both from MVA-GP immunised animals after challenge with CCHF virus.

<p>Animals were challenged with 200 ffu of CCHF virus 14 days after the booster vaccination or 1 day post-transfer of sera, CD3⁺ T cells, or both. Six animals from each group were used to assess survival post-challenge.</p