Methods for Evaluation of Humoral Immune Responses in Human Genital Tract Secretions

Abstract

Citation Mestecky J, Alexander RC, Wei Q, Moldoveanu Z. Methods for evaluation of humoral immune responses in human genital tract secretions. Am J Reprod Immunol 2011; 65: 361–367 The compilation of epidemiological, virological, and immunological data clearly indicates that HIV‐1 infection must be considered primarily as a disease of the mucosal immune system. The earliest and most dramatic alterations of the immune system occur in the mucosal compartment. However, the mucosal immune systems of the genital and intestinal tracts display remarkable immunological differences that must be considered in the evaluation of humoral immune responses in HIV‐1‐infected individuals or in volunteers immunized with experimental HIV vaccines. In this regard, marked differences in the dominant Ig isotypes, molecular forms of HIV‐1‐specific antibodies, and their distinct effector functions in the genital versus intestinal tracts must be carefully evaluated and considered in the measurement and interpretation of humoral immune responses. Appropriate controls and alternative immunochemical assays should be used to complement and confirm results generated by ELISA, which are prone to false positivity. Special precautions and rigorous controls must be used in the evaluation of antibody‐mediated virus neutralization in external secretions of the genital and intestinal tracts.

Detection of Mycoplasma genitalium-Reactive Cervicovaginal Antibodies among Infected Women

“…In contrast, IgG4 lacks such effector functions (16), and IgG2 has low levels of complement activation (17), which is interesting given our negative results with these subtypes. We also failed to detect an IgM response, which may be explained by the low levels of IgM in genital secretions (14). Alternatively, these observations could be influenced by the timing of sample collection in the course of infection, as IgM is a short-lived isotype typically produced early in infection (17).…”

“…IgA serves as a first line of defense by preventing binding (17), interfering with motility, and enhancing opsonization through agglutination (21). The dominant isotype in cervicovaginal secretions is IgG (12,14). Of the four isotypes, IgG1 and IgG3 are the most biologically active and proinflammatory through complement activation (15).…”

Experimental Infection of Pig-Tailed Macaques (Macaca nemestrina) with Mycoplasma genitalium

“…Cervical infection alone induced specific antibodies in only one of three persistently infected animals, and these arose after 4 weeks of infection, perhaps unsurprising given that the lower genital tract lacks well-developed inductive immune sites (55). Similarly, in previous experiments with male chimpanzees, serum antibodies were detectable at 5 to 11 weeks after intraurethral infection (42,43) and 3 to 4 weeks after vaginal inoculation of female chimpanzees (42).…”

“…The low rate of persistence in these pockets may indicate failure to establish an infection or rapid clearance by specific antibodies arising by week 1 in these heavily inoculated animals. The persistence of infection in the genital tracts of these same animals may indicate that M. genitalium can avoid clearance by the lower concentration of antibodies present in cervicovaginal secretions than in serum (55).…”

Relationship of the quaternary structure of human secretory IgA to neutralization of influenza virus

“…These polymeric IgA forms are associated with the extracellular portion of the polymeric Ig receptor, generating a complex (receptor + polymeric IgA) called S-IgA (9). S-IgA primarily corresponds to dimeric IgA, although low levels of some larger polymeric forms, particularly tetramers, are also present (9)(10)(11)(12)(13)(14)(15). Polymeric S-IgA has been shown (both in vitro and in experimental animal models) to be more effective than monomeric IgA or IgG for the neutralization of influenza viruses (16)(17)(18)(19).…”