1. Antibody and B cell responses may control circulating lipopolysaccharide in patients with HIV infection Lim A 1, Amini A 1, D’Orsogna L 2, Rajasuriar R 3, Lewin S 3,4, Purcell D 5, Price P 1, French MA 1,2 1. School of Pathology and Laboratory Medicine, University of Western Australia 2. Department of Clinical Immunology, Royal Perth Hospital, Perth 3. Alfred Hospital, Melbourne 4. Monash University, Melbourne 5. Department of Microbiology and Immunology, University of Melbourne

2. Marginal zone (IgM + memory) B cells and IgA antibodies respond to gut microbial products Cerutti A, Rescigno M. Immunity 2008; 28:740-50 Kraal G. Nature Immunol 2008; 9:11-12

3. Plasma levels of LPS are inversely correlated with serum levels of antibodies to LPS in ART-naïve HIV patients

4. LPS-specific IgG antibodies correlate with IgM + memory B cell counts in ART-naïve patients

5. Better immune reconstitution on ART is associated with lower plasma LPS and serum anti-LPS

6. Summary In ART-naïve patients: Serum levels of IgG and IgA antibodies to LPS are negatively correlated with plasma LPS levels Serum levels of IgG anti-LPS are positively correlated with circulating IgM + memory B cell counts Serum IgA levels are strongly correlated with serum levels of IgA antibodies to LPS In ART-treated patients: Better immune reconstitution (higher CD4 + T cell and switched memory B cell counts) is associated with lower levels of LPS and antibodies to LPS

7. Conclusions Plasma LPS levels in ART-naive HIV patients may be determined by immune responses against LPS, as well as by increased gut permeability High serum IgA levels in untreated HIV infection may reflect an IgA antibody response against LPS