Immunoglobulin G (IgG) Subclass Distribution and IgG1 Avidity of Antibodies in Human Immunodeficiency Virus-Infected Individuals after Revaccination with Tetanus Toxoid

In human immunodeficiency virus (HIV)-infected individuals the amount of antibodies formed after vaccination with T-cell-dependent recall antigens such as tetanus toxoid is proportional to the peripheral blood CD4⁺ T-lymphocyte counts. To investigate whether the immunoglobulin G (IgG) subclass distribution and avidity of the antibodies produced after vaccination are affected as well, we gave 13 HIV-infected adults with low CD4⁺ T-lymphocyte counts (<200 × 10⁶/liter; group I), 11 HIV-infected adults with intermediate CD4⁺ T-lymphocyte counts (≥200 × 10⁶/liter; group II), and 5 healthy controls booster immunizations with tetanus toxoid. The prevaccination antibody concentrations against tetanus toxoid were similar in the HIV-infected and healthy adults. After vaccination the total IgG and the IgG1 anti-tetanus toxoid antibody concentrations were significantly lower in group I than in group II and the controls. The avidity of the IgG1 anti-tetanus toxoid antibodies formed by HIV-infected adults was within the range for healthy controls, irrespective of their CD4⁺ T-lymphocyte counts.In human immunodeficiency virus (HIV)-infected individuals the amount of antibodies formed after vaccination with T-cell-dependent recall antigens, such as tetanus toxoid, is impaired in proportion to the number of CD4⁺ T cells and to the in vitro proliferative response of T lymphocytes to anti-CD3 monoclonal antibodies (7, 8). Protection against tetanus will depend on the total amount of antibodies, the subclass distribution, and the avidities of the antibodies that are formed. Avidity reflects the combined functional affinities of antibodies formed during a polyclonal humoral immune response and is considered to be a parameter for the efficacy of the antibodies at eliminating or neutralizing the antigen (12). The aim of the present study was to investigate whether, in addition to the concentration of antibodies, the subclass distribution and the avidity of the antibodies formed by HIV-infected individuals after booster vaccination are affected.(This study was presented in part at the 35th Annual Meeting of the Infectious Diseases Society of America, San Francisco, Calif., 13 to 16 September 1997.)