Table 5.

In vitro antiviral screening assaysa

Determination of viral infectivity under two conditions: I. In cultured cells during virus multiplication in the presence of a single compound (A-S) or a mixture of compounds, e.g., plant extracts (A-M). II. After extracellular incubation with a single compound (V-S) or a mixture of compounds (V-M).
Plaque inhibition assay (only for viruses which form plaques in suitable cell systems)
 Titer determination of a limited number of viruses in the presence of a nontoxic dose of the test substance
 Applicability: A-S
Plaque reduction assay (only for viruses which form plaques in suitable cell systems)
 Titer determination of residual virus infectivity after extracellular action of test substance(s) (see reference for comments on cytotoxicity)
 Applicability: V-S, V-M
Inhibition of virus-induced cytopathic effect (for viruses that induce cytopathic effect but do not readily form plaques in cell cultures)
 Determination of virus-induced cytopathic effect in cell monolayers cultured in liquid medium, infected with a limited dose of virus, and treated with a nontoxic dose of the test substance(s)
 Applicability: A-S, A-M
Virus yield reduction assay
 Determination of the virus yield in tissues cultures infected with a given amount of virus and treated with a nontoxic dose of the test substance(s)
 Virus titer determination carried out after virus multiplication by the plaque test or the 50% tissue culture infective dose end-point test
 Applicability: A-S, A-M
End-point titer determination technique
 Determination of virus titer reduction in the presence of twofold dilutions of test compound(s)
 This method especially designed for the antiviral screening of crude extracts (238)
 Applicability: A-S, A-M
Assays based on measurement of specialized functions and viral products (for viruses that do not induce cytopathic effects or form plaques in cell cultures)
 Determination of virus specific parameters, e.g., hemagglutination and hemadsorption tests (myxoviruses), inhibition of cell transformation (Epstein-Barr virus), immunological tests detecting antiviral antigens in cell cultures (Epstein-Barr virus, HIV, HSV, cytomegalovirus)
 Applicability: A-S, A-M, V-S, V-M
 Reduction or inhibition of the synthesis of virus specific polypeptides in infected cell cultures, e.g., viral nucleic acids, determination of the uptake of radioactive isotope-labelled precursors or viral genome copy numbers
 Applicability: A-S, A-M, V-S, V-M
  • a Reprinted from reference238 with permission of the publisher.