In Vitro Efficacy Evaluations
This service provides evaluation of products which already have been evaluated in a biochemical or cell-based assay and shown to possess an activity profile that warrants further development of the product as a microbicide. NIAID does NOT offer the primary screening of previously untested products via this service. Products must be single-component entities of known chemical structure; evaluation of multi-component natural product extracts is not supported.
Products are evaluated for topical microbicide potential using the following screening algorithm (published in Antimicrobial Agents and Chemotherapy. 2008 May; 52(5): 1768–1781).
Primary Assays
- CD4-dependent CCR5-tropic cell-associated HIV-1 transmission inhibition and cytotoxicity assays
- CD4-dependent CCR5-tropic cell-free HIV-1 entry inhibition and cytotoxicity assays
Decision Point: If Therapeutic Index (TI= TC50/IC50, where TC50 = 50% inhibitory concentration in cytotoxicity assay and IC50 = 50% inhibitory concentration in anti-HIV assay) for Primary Assay 1 is ≥10 for colorless products or ≥50 for colored products, Confirmatory Assays will be initiated. If TIs fail to meet these cutoffs, further evaluation of the product is terminated.
Confirmatory Assays
- Repeat of CD4-dependent CCR5-tropic cell-associated HIV-1 transmission inhibition and cytotoxicity assays
- Repeat of CD4-dependent CCR5-tropic cell-free HIV-1 entry inhibition and cytotoxicity assays
Decision Point: If TIs remain ≥10 for colorless products or ≥50 for colored products, Secondary Assays will be initiated. If TIs fail to meet these cutoffs, further evaluation of the product is terminated.
Secondary Assays
- CD4-dependent CCR5-tropic HIV-1 fusion inhibition assay
- CD4-dependent CXCR4-tropic cell-associated HIV-1 transmission inhibition assay
- CD4-dependent CXCR4-tropic HIV-1 entry inhibition assay
- CD4-dependent CXCR4-tropic HIV-1 fusion inhibition assay
- CD4-independent HIV-1 transmission inhibition assay (ME-180 assay)
- Primary assays modified to incorporate 25% seminal plasma
- Primary assays modified to incorporate a pH transition step
- Lactobacillus growth inhibition assay
Decision Point: The most highly ranked compounds from Secondary Assays are evaluated in Specialized Assays.
Specialized Assays
- Human cervical explant model
- Human PBMC clade panel testing
- Combination drug assays
- Specialized cytotoxicity (Vybrant and LIVE/DEAD) assays
The current contractor for this service is Southern Research Institute, Frederick, Maryland.