Secretory component is bound to the paraproteins in sera of IgA and IgM gammopathies

Infection of macrophages and dendritic cells with primary R5-tropic human immunodeficiency virus type 1 inhibited by natural polyreactive anti-CCR5 antibodies purified from cervicovaginal secretions

Heterosexual contact is the primary mode of human immunodeficiency virus (HIV) type 1 (HIV-1) transmission worldwide. The chemokine receptor CCR5 is the major coreceptor that is associated with the mucosal transmission of R5-tropic HIV-1 during sexual intercourse. The CCR5 molecule is thus a target for antibody-based therapeutic strategies aimed at blocking HIV-1 entry into cells. We have previously demonstrated that polyreactive natural antibodies (NAbs) from therapeutic preparations of immunoglobulin G and from human breast milk contain NAbs directed against CCR5. Such antibodies inhibit the infection of human macrophages and T lymphocytes by R5-tropic isolates of HIV in vitro. In the present study, we demonstrate that human immunoglobulins from the cervicovaginal secretions of HIV-seronegative or HIV-seropositive women contain NAbs directed against the HIV-1 coreceptor CCR5. Natural affinity-purified anti-CCR5 antibodies bound to CCR5 expressed on macrophages and dendritic cells and further inhibited the infection of macrophages and dendritic cells with primary and laboratory-adapted R5-tropic HIV but not with X4-tropic HIV. Natural anti-CCR5 antibodies moderately inhibited R5-tropic HIV transfer from monocyte-derived dendritic cells to autologous T cells. Our results suggest that mucosal anti-CCR5 antibodies from healthy immunocompetent donors may hamper the penetration of HIV and may be suitable for use in the development of novel passive immunotherapy regimens in specific clinical settings of HIV infection.

Immunoglobulins of the human amniotic fluid

PROBLEM

Except for the description of a secretory immunoglobulin (S-Ig) of a low size, no recent study has investigated the molecular status of antibodies in the human amniotic fluid.

METHOD

After separation with a high performance chromatography, we analyzed the different isotypes of amniotic Igs by immunoblotting and ELISA.

RESULTS

IgG is found to be the major isotype and to contain mother-derived tetanus antitoxins. IgA is much less abundant, whereas no IgM can be detected. IgA is monomeric, with a low level of secretory IgA and with various amounts of free secretory component (SC). The presence of a low level of SC-containing immunoglobulin of a low size is confirmed during the last trimester of pregnancy. This molecule contains no alpha chain but includes a Fabgamma fragment noncovalently associated with SC. IgG, IgA, and SC are detected in the fetal urine and, therefore, can reach the amniotic fluid by this route.

CONCLUSION

In addition to the predominant maternal IgG, the amniotic fluid contains different molecular forms of fetal immunoglobulins. Their function as an immune barrier against infection and against mother-derived autoantibodies is discussed.

Local synthesis of IgG antibodies to HIV within the female and male genital tracts during asymptomatic and pre-AIDS stages of HIV infection

Paired sera and cervicovaginal secretions or seminal fluids, obtained from HIV-1-infected, clinically asymptomatic women (n = 41) and men (n = 12), were investigated in order to test the hypothesis of a local synthesis of IgG to HIV in the female and male reproductive tracts. Anti-gp41 + p24 IgG was evaluated by an IgG immunocapture assay, and anti-gp160 IgG by an indirect ELISA. Estimation of anti-HIV IgG-specific activities was carried out after ponderal determination of total IgG and evaluation of anti-HIV IgG activity. IgG to gp41 + p24, as well as IgG to gp160, were specifically detected in all sera, cervicovaginal secretions, and seminal fluid samples from all tested HIV-1-infected subjects. The mean specific activities of IgG to gp41 + p24 in cervicovaginal secretions and in seminal fluids were about 33-fold (in women) and 16-fold (in men) that of the corresponding sera; similarly, the mean specific activities of IgG to gp160 in genital secretions were about 17-fold (in women) and 10-fold (in men) that of the corresponding sera. IgGs to HIV are constantly detected in genital secretions from HIV-1-infected subjects, and appear to be largely synthesized in situ within the genital tract of both genders.

Increased levels of serum IgA as IgA1 monomers in ankylosing spondylitis

The various subsets of serum IgA were determined in 43 patients with ankylosing spondylitis to investigate the putative mucosal origin of increased IgA concentrations in this disease. Total IgA was shown to be increased and weakly correlated with the erythrocyte sedimentation rate (ESR). In contrast, although the mean concentration (but not the median) of secretory IgA (SIgA) was slightly increased, no correlation was found with total IgA nor the ESR. Moreover, molecular sieving of nine serum samples selected for their high concentrations of total IgA, and absorption with insoluble jacalin showed these immunoglobulins to be essentially monomers of the IgA1 subclass. These results are consistent with a non-secretory origin of the increase of serum IgA, which must be ascribed to the central immune system.