Elevated serum pregnancy zone protein levels in HIV-1-infected men

Pregnancy zone protein (PZP), also known as pregnancy-associated alpha sub(2) macroglobulin, is elevated in the sera of pregnant and estrogen-treated women and both men and women with a variety of malignant and inflammatory diseases. This indicates that the induced appearance of PZP is not restricted to pregnancy as its name implies. Only low levels of PZP are detected in normal healthy adults and children of both sexes. Although human PZP and its constitutively expressed counterpart, serum alpha sub(2) macroglobulin, share a significant 71% amino acid homology, these molecules are immunologically distinct. Both human PZP and serum alpha sub(2) macroglobulin have proteinase inhibitory activity. Peripheral blood lymphocytes and monocyte/macrophages synthesize PZP and are also primary targets for HIV-1 infection. This suggested that elevated serum PZP levels may also exist in HIV-1-infected individuals. To answer this question we measured PZP concentrations using a sensitive enzyme-linked immunosorbent assay in three experimental groups: (i) 36 sera from normal healthy adult male volunteers not known to be at risk of HIV-1 infection (aged 21-45 years); (ii) 13 sera from HIV-1-seropositive AIDS-free men not receiving antiretroviral therapy (aged 18-42 years); and (iii) 50 sera from HIV-1-seropositive men with clinical and laboratory documented AIDS (aged 25-53 years). Many patients in group (iii) suffered from opportunistic infections associated with AIDS and were all receiving combination antiretroviral therapy. We recognize that including a second control group consisting of healthy HIV-1-seronegative high-risk homosexual men would have provided additional valuable information; however, such sera were unavailable at the time of this preliminary study.