Generation of high affinity monoclonal antibodies for the prevention of HIV infection

Dynamic appearance of antigenic epitopes effective for viral neutralization during membrane fusion initiated by interactions between HIV-1 envelope proteins and CD4/CXCR4

HIV-1 entry into cells is mediated by interactions between the envelope (Env) gp120 and gp41 proteins with CD4 and chemokine receptors via an intermediate called the viral fusion complex (vFC). Here, mAbs were used to find the dynamic changes in expression of antigenic epitopes during vFC formation. A CD4-specific mAb (R275) and anti-vFC mAbs, designated F12-1, F13-6 and F18-4 that recognize the epitopes only appeared by the co-culture of env-transfected 293FT and CD4-transfected 293 cells, were developed by immunizing ganp-gene transgenic mice with an vFC-like structure formed by the same co-culture. The epitopes recognized by the mAbs appeared at different time points during vFC formation: F18-4 appeared first, followed by F13-6, and finally F12-1. The anti-vFC mAbs had little effect on vFC formation or virus neutralization; however, interestingly F12-1 and F18-4 increased exposure of the OKT4-epitope on the domain 3 in the extracellular region of CD4. R275, which recognizes the epitope closely associated with the OKT4-determinant on the domain 3, showed the marked inhibition of vFC formation and viral neutralization activity. The Ab binding to the epitopes appeared during viral membrane fusion might reinforce the appearance of the target epitopes for effective neutralization activity.

The novel use of a routine quantitative system to analyze the activity, content and affinity of an antibody to hepatitis B core antigen

BACKGROUND

Currently, quantitative measurement of serum markers of HBV infection has been widely used, but commonly used analysis for specific antibodies only involves the measurement of the total antibody activity, and the binding affinity or protein content is rarely analyzed.

OBJECTIVE

To investigate the detailed features of an antibody to hepatitis B core antigen (anti-HBc) during different periods of hepatitis B virus (HBV) infection with a new method of analysis.

STUDY DESIGN

Serum samples were collected from patients that were positive for the anti-HBc antibody. On the basis of the other serological markers in the samples, all patients were divided into a hepatitis B surface antigen (HBsAg)-positive group and an antibody to hepatitis B surface antigen (anti-HBs)-positive group. All samples were diluted 2-, 20- and 200-fold. Anti-HBc quantification was measured with a chemiluminescent microparticle immunoassay; total anti-HBc activity, protein content and affinity were calculated according to a measured value of each dilution. Serum HBV DNA load and alanine aminotransferase (ALT) levels were also measured.

RESULTS

The total anti-HBc activity in the HBsAg-positive group was statistically higher than that in the anti-HBs-positive group (p<0.05). The anti-HBc protein content during active HBV infection was statistically higher than during the convalescence stage (p<0.05), while anti-HBc affinity during HBV infection was lower than during recovery. There were correlations among total activity, affinity, protein content of anti-HBc, and ALT, HBV-DNA (p<0.05).

CONCLUSIONS

It is potentially possible to predict the status of HBV infection by measuring total activity, protein content and affinity of anti-HBc.