IgG subclass reactivity against human immunodeficiency virus (HIV) and cytomegalovirus in cerebrospinal fluid and serum from HIV-infected patients.

Cerebrospinal fluid (CSF) and serum samples from 17 patients seropositive for the human immunodeficiency virus (HIV) were analysed for specific IgG1-4 against HIV and cytomegalovirus (CMV). Measles IgG was studied as a reference to detect blood-brain barrier (BBB) defects. All patients had IgG1 antibodies against HIV in both CSF and serum, and all had CMV IgG1 in serum (16 in CSF). Anti-HIV IgG was synthesised intrathecally in 11 patients, IgG3 in three patients, and IgG4 in three patients. Intrathecal production of anti-CMV IgG1 was found in three patients, IgG2 in one, IgG3 in three, and IgG4 in one. Intrathecal anti-HIV IgG synthesis could be demonstrated in all stages of the disease. Analysis of all IgG subclasses allowed intrathecal HIV and/or IgG production to be detected also in patients in whom intrathecally synthesised IgG was restricted to IgG2, 3, or 4. The expression of HIV-specific IgG subclasses in CSF and serum was more restricted in AIDS patients than in HIV-infected persons without clinical AIDS. On the contrary, the largest number of CMV-specific IgG subclasses was found in AIDS patients. Intrathecal HIV or CMV IgG subclass production was seen both with and without neurological symptoms. The peripheral T4 cell counts were not obviously related to neurological symptoms. Even patients with low peripheral T4 cell counts had evidence of intrathecal antibody synthesis against HIV and sometimes CMV, suggesting a retained helper function of T cells in the central nervous system.