Neutralization of HIV-1 Infection of Human Peripheral Blood Mononuclear Cells (PBMC) : Infectivity Reduction Method.

Area of Science:

• Virology
• Immunology
• Assay Development

Background:

• Serum titration assays indirectly measure antibody neutralization by quantifying p24 antigen expression in infected cells.
• This indirect method assumes a direct correlation between p24 antigen levels and the number of infected cells, which can be influenced by virus growth kinetics.

Purpose of the Study:

• To evaluate the Infectivity Reduction Assay (IRA) for directly measuring antibody-mediated neutralization of HIV-1.
• To compare the IRA with traditional serum titration assays, highlighting the IRA's advantages in handling diverse virus isolates.

Main Methods:

• The IRA quantifies the reduction in virus median tissue culture infectious dose (TCID(50)) by serially diluting virus stocks with stimulated peripheral blood mononuclear cells (PBMC).
• HIV-1 infection is detected by measuring p24 antigen expression after eight days in culture.
• Results are reported as the ratio of virus TCID(50) in control sera versus test sera.

Main Results:

• The IRA directly measures the impact of antibodies on virus infectivity, providing a more direct assessment of neutralization.
• Unlike titration assays, the IRA is not affected by variations in virus growth kinetics, making it suitable for diverse viral isolates.
• The assay quantifies antibody-mediated reduction in virus TCID(50).

Conclusions:

• The Infectivity Reduction Assay (IRA) provides a direct and robust method for assessing HIV-1 neutralization by antibodies.
• The IRA's independence from virus growth kinetics makes it superior for comparing neutralization potency across a wide range of HIV-1 isolates.