[27] consistent with a role for phagocytosis in the disappearance of virion–IgG complexes in Fiebig Stage IV.[27] This hypothesis is supported by the finding that phagocytosis by both monocytes and dendritic cells is increased in acute

infection and impaired in chronic infection.[27] The impairment in chronic infection was tightly associated with down-regulation of FcγR2a and FcγR3a on monocytes and dendritic cells.[27] The expansion of circulating natural killer cells expressing FcγR3 in Fiebig Stages II and III,[56] immediately before check details or at the beginning of seroconversion, suggests that ADCC responses might occur concomitant with emergence of free IgG antibodies to gp41 and gp120. The involvement of Fc-mediated effector function before Fiebig Stage V where ADCC responses are first detectable[24, 26] is hypothetical and based on indirect indications. This hypothesis can be tested readily with infection OTX015 in vitro models in NHPs where effector cells and antibodies can

be quantified at defined times post-infection. Despite the uncertainty about the role of Fc-mediated effector function in acute infection, a large body of data has accumulated over the years demonstrating correlations between clinical outcome and ADCC titres in HIV-infected individuals. These studies are summarized in Table 1. The earliest report of a correlation between ADCC titres and clinical stage appeared in 1987[57] and studies with similar conclusions continue to appear Roflumilast up to the time of writing.[58] Of the 19 studies listed in Table 1, three failed to detect correlations between ADCC and clinical outcomes whereas the other 16 reported correlations between ADCC and positive clinical outcomes. Further, the negative studies were in the early years of the epidemic when methodology

was more challenging. The 15 positive studies, spanning 26 years and involving different cohorts and methods, provide compelling support for the involvement of Fc-mediated effector function, particularly ADCC, and post-infection control of HIV. This conclusion is supported also by similar studies in NHPs, although they are fewer in number. The first NHP study, which appeared in 2002, reported an inverse correlation between ADCC titres and progression to simian AIDS in the simian immunodeficiency virus model of infection.[59] A second study appeared in 2011 and reported similar conclusions in the same model.[60] A third study reported an inverse correlation between another Fc-mediated effector function, antibody-dependent cellular viral inhibition (ADCVI),[24, 61] which has elements similar to ADCC, and viral control.[62] Collectively, studies in both HIV-infected individuals and simian immunodeficiency virus-infected rhesus macaques strongly support a role for Fc-mediated effector function, and ADCC in particular, in post-infection control of viraemia.