A replication competent luciferase-secreting DENV2 reporter for sero-epidemiological surveillance of neutralizing and enhancing antibodies

Dengue virus (DENV) specific neutralizing and enhancing antibodies play crucial roles in dengue disease prevention and pathogenesis. DENV reporters are gaining popularity in the evaluation of these antibodies; their accessibility and acceptance may improve with more efficient production systems and indications of their antigenic equivalence to the wild-type virus. This study aimed to generate a replication competent luciferase-secreting DENV reporter (LucDENV2) and evaluate its feasibility in neutralizing and infection-enhancing antibody assays in comparison with wild-type DENV2, strain 16681, and a luciferase-secreting, single-round infectious DENV2 reporter (LucSIP). LucDENV2 replicated to similarly high levels as that of the parent 16681 virus in a commonly used mosquito cell line. LucDENV2 was neutralized in an antibody concentration-dependent manner by a monoclonal antibody specific to the flavivirus fusion loop and two antibodies specific to the E domain III, which closely resembled the neutralization patterns employing the LucSIP and wild-type DENV2. Parallel analysis of LucDENV2 and wild-type DENV2 revealed good agreement between the luciferase-based and focus-based neutralization and enhancement assays in a 96-well microplate format when employed against a set of clinical sera, suggesting comparable antigenic properties of LucDENV2 with those of the parent virus. The high-titer, replication competent, luciferase-secreting DENV reporter presented here should be a useful tool for fast and reliable quantitation of neutralizing and infection-enhancing antibodies in populations living in DENV-endemic areas.

Generation and characterization of luciferase-secreting, single-round infectious DENV-2 reporter for functional antibody assays

Flavivirus reporters provide a robust tool for viral pathogenesis studies, anti-viral drug screening, disease diagnosis and functional antibody assays. In this study, we generated a luciferase-secreting, single-round reporter virus by replacing the capsid coding region in a DENV-2 genome with the secretory form of Lucia luciferase gene to produce infectious viral particles in a stable capsid-expressing mosquito cell line. Replication of the reporter virus in trans-complementing mosquito cells was sustained for up to two weeks. There were strong correlations between the extracellular luciferase activity and infectious reporter virus inocula upon infection of mosquito and mammalian cell lines with graded quantities of the reporter virus. A set of anti-E and anti-prM monoclonal antibodies affected the infectivity of reporter virus with similar dose-effect relationships as the parent virus. This simplified version of DENV-2 reporter provides a rapid and reliable method for the detection of neutralizing and infection-enhancing antibodies against dengue virus.

Ellagic acid inhibits HIV-1 infection in vitro: Potential role as a novel microbicide

OBJECTIVE

To investigate the in vitro effects of ellagic acid on HIV-1 replication.

METHODS

Anti-HIV-1 activity of ellagic acid was determined in vitro using X4-tropic HIV-1_NPO3 and R5-tropic pBaL Env-recombinant virus. Anti-HIV-1_NPO3 activity of ellagic acid was investigated at a multiplicity of infection (MOI) of 0.01. Anti-HIV-1 integrase and protease activities of ellagic acid were tested using in vitro integration and proteolytic cleavage assays.

RESULTS

Ellagic acid, added either before or after HIV-1_NPO3 exposure, suppressed replication of the virus in C8166 cells up to 34%. Ellagic acid showed an anti-integrase IC₅₀ of 8.7 μM. No cytotoxicity of ellagic acid at concentrations ranging from 12.5 to 100 μM was observed.

CONCLUSION

We conclude that ellagic acid can inhibit HIV-1 infection without cytotoxicity. Thus, it may be a new effective agent that has potential to be developed as a novel microbicide against HIV-1.