Phagocytosis can be induced via the engagement of Fcγ receptors by antibody-opsonized material. Furthermore, the efficiency of antibody-induced effector functions has been shown to be dramatically modulated by changes in antibody glycosylation. Because infection can modulate antibody glycans, which in turn modulate antibody functions, assays capable of determining the induction of effector functions rather than neutralization or titer provide a valuable opportunity to more fully characterize the quality of the adaptive immune response. Here we describe a robust and high-throughput flow cytometric assay to define the phagocytic activity of antigen-specific antibodies from clinical samples. This assay employs a monocytic cell line that expresses numerous Fc receptors: including inhibitory and activating, and high and low affinity receptorsallowing complex phenotypes to be studied. We demonstrate the adaptability of this highthroughput, flow-based assay to measure antigen-specific antibody-mediated phagocytosis against an array of viruses, including influenza, HIV, and dengue. The phagocytosis assay format further allows for simultaneous analysis of cytokine release, as well as determination of the role of specific Fcγ-receptor subtypes, making it a highly useful system for parsing differences in the ability of clinical and vaccine induced antibody samples to recruit this critical effector function.

While development of an HIV vaccine that can induce neutralizing antibodies remains a priority, decades of research have proven that this is a daunting task. However, accumulating evidence suggests that antibodies with the capacity to harness innate immunity may provide some protection. While significant research has focused on the cytolytic properties of antibodies in acquisition and control, less is known about the role of additional effector functions. In this study, we investigated antibody-dependent phagocytosis of HIV immune complexes, and we observed significant differences in the ability of antibodies from infected subjects to mediate this critical effector function. We observed both quantitative differences in the capacity of antibodies to drive phagocytosis and qualitative differences in their Fc␥R usage profile. We demonstrate that antibodies from controllers and untreated progressors exhibit increased phagocytic activity, altered Fc domain glycosylation, and skewed interactions with Fc␥R2a and Fc␥R2b in both bulk plasma and HIV-specific IgG. While increased phagocytic activity may directly influence immune activation via clearance of inflammatory immune complexes, it is also plausible that Fc receptor usage patterns may regulate the immune response by modulating downstream signals following phagocytosis-driving passive degradation of internalized virus, release of immune modulating cytokines and chemokines, or priming of a more effective adaptive immune response.

The significance of hepatitis associated antigen (HAA) was studied by immunodiffusion techniques in 270 sporadic acute viral hepatitis cases in Greece. The antigen was detected in 94 (34.8%) cases. The incidence was higher in the early stages and declined later in the course of the disease. It was further demonstrated that there is no sex or age difference in the incidence of HAA, which is also independent from the severity of the disease as reflected in the SGPT activity. The cases were characterised by available detailed history as infectious hepatitis (IH) or serum hepatitis (SH). The HAA was detected in almost equal proportions in both types. Also, they did not differ in their mean geometrical titre of HAA or in the trend of decline of their incidence in the later stages of the disease.

No abstract

Hepatitis-associated antigen (HAA) was detected by immunodiffusion (ID) or complement-fixation (CF) test in 141 (47.3%) of 298 viral hepatitis patients. 35 cases were positive by the CF test only, while 2 cases by ID test only. However, CF test failed to detect HAA in a greater number of sera from 60 studied leprosy patients. CF HAA titers were highly correlated, but 15–25 times higher than ID titers. The increased sensitivity of the CF test especially in cases with low HAA titers may be the reason for the observed greater decline of the relative frequency of HAA, in relation to time of collection of sera after onset of jaundice, when sera were examined by ID rather than by CF test. In 39 (28.1%) cases, positive by the CF test, prozone reactions were observed at dilutions of 1 : 16 or higher, which stresses the necessity to examine a wide range of serum dilutions. The presence of anticomple-mentary activity had no diagnostic value and did not interfere substantially with the detection of HAA.