PROJECT SUMMARY: In the general population, IgG glycomic alterations correlate with and drive inflammatory responses during aging (inflammaging). However, it was previously unknown whether living with antiretroviral therapy (ART)-suppressed HIV infection is associated with changes in these markers of inflammaging. During the last funding cycle, we found that living with ART-suppressed HIV infection is associated with an acceleration in the accumulation of pro-aging IgG glycomic alterations. Specifically, antibodies from people with HIV (PWH) on ART show a more significant loss of the anti-inflammatory glycans galactose (agalactosylation) and sialic acid (hypo-sialylation) compared to antibodies from HIV-negative controls. These glycomic alterations were linked to higher inflammation and increased severity of inflammaging-associated comorbidities in PWH. In a proof-of-concept study, we also found that these alterations might precede the development of such comorbidities by years, making them excellent candidates for discovering biomarkers to predict these conditions. In addition to their associations with inflammaging in PWH on ART, these glycomic alterations during ART correlated with a faster HIV rebound after stopping ART. Consistently, levels of these glycans correlate with elevated levels of HIV DNA during ART. This intriguing correlation between these markers of inflammaging and HIV persistence prompted us to investigate the mechanisms by which these alterations might contribute to larger HIV reservoirs and greater inflammaging: 1) Agalactosylation: The loss of galactose reduces the ability of IgGs to elicit Fc-mediated anti-viral innate immune function. This reduced function could result in a larger HIV reservoir and, consequently, greater inflammation. Our data support this mechanism, as glycoforms of the HIV antibody 10-1074 engineered to lack galactose exhibited significantly lower anti-HIV immune function than glycoforms with high galactose. 2) Hypo-sialylation: The loss of sialic acid prevents a potent anti-inflammatory mechanism by myeloid cells. Our data support this mechanism by showing that treating HIV-infected viremic humanized mice with sialidase inhibitors (to prevent hypo-sialylation) attenuates HIV-mediated inflammation. Our current aims capitalize on these findings to start delineating their translational potential with the overarching hypothesis that agalactosylation and hypo-sialylation: 1) can serve as predictive biomarkers for inflammaging- associated comorbidities in PWH (Aim 1a); 2) are mechanistically linked to HIV persistence and inflammation by compromising anti-viral innate immune functions (Aim 1b and Aim 2a); and 3) can be normalized to enhance immunity and inhibit inflammaging (Aim 2a and Aim 2b). In Aim 1 (human samples aim), we will test the hypothesis that IgG agalactosylation and hypo-sialylation can predict inflammaging-associated comorbidities in PWH and are linked to compromised anti-HIV innate immune fun...