Role of B Lymphocytes In HIV Infection And Pathogenesis

National Institute Of Allergy And Infectious Diseases

Investigators

Linked publications & trials

Abstract

In 2021, we pursued studies encompassing three major themes: 1) investigating B cells in the peripheral blood and in lymph nodes of HIV-infected individuals to identify differences in immune function associated with disease progression; 2) evaluating the role of immunoglobulin IgG3 and other soluble factors in regulating B cells in HIV infection; and 3) performing studies on B cells in non-HIV diseases. Enrollment of HIV participants in our various clinical protocols continued to be stalled in 2021 due to COVID-19 restrictions. Nonetheless, the studies affected were redesigned using stored clinical specimens or data previously acquired were reanalyzed with new tools. As part of a longstanding collaboration, we have been investigating B and T cells in advanced HIV disease in collaboration with Dr. Sereti, under her clinical research protocol NCT02147405. The goal of a recently completed study was to evaluate immune reconstitution following initiation of antiretroviral therapy (ART) in individuals with advanced HIV disease. Participants underwent lymph node biopsies at the time of enrollment and again 6-8 weeks post ART. These paired biopsies offered a unique opportunity to investigate immunologic changes that occur over a short period of time after the immune system begins to recover from advanced HIV disease. Several important insights gained have implications for other immune deficiencies. However, given the complexity of advanced HIV disease, the past year was spent trying to identify which changes were associated with immune reconstitution and which were associated with advanced HIV disease itself. The changes in B and T cells following initiation of ART and reduction in viremia suggest that both types of changes were occurring during the period of analysis. This study has been completed and submitted to a peer-reviewed journal. One unexpected observation among B cells was the expansion in advanced disease of a population of memory B cells that expressed IgM as the B-cell receptor in the absence the other isotype, IgD, that is usually expressed with IgM. Ongoing efforts are aimed at understanding this population and whether it explains the depletion of IgM/D memory B cells that occurs with HIV disease progression. In a related lymph node study on the Th1-polarizing transcription factor T-bet, previously shown to be overexpressed in B cells of HIV-infected individuals who do not mount an effective antibody response against the virus, the planned follow-up study could not be pursued due to our inability to perform lymph node biopsies at the clinical center during the pandemic. In lieu, an alternative approach was designed using stored peripheral blood-derived B cells as they are not as affected by cryopreservation as their lymph node counterparts. Accordingly, B cells of individuals with and without HIV-neutralizing antibody profiles are being analyzed to determine whether T-bet regulation and other transcriptional and epigenetic features differ between these two groups of individuals. In the second major theme, we continued to investigate the role of IgG3 in binding and regulating B cells of HIV-infected individuals by evaluating 1) the kinetics of IgG3 binding patterns in individuals who underwent analytical treatment interruption (ATI) of ART; and 2) IgG3 glycan profiles in our cohorts of HIV-infected and uninfected individuals. Regarding the first project, we used spectral flow cytometry and high-dimensional analyses to evaluate the dynamics of IgG3 binding to B cells in the peripheral blood of individuals undergoing ATI following administration of neutralizing anti-HIV antibodies, as part of therapeutic interventions to suppress HIV replication and induce immune responses against the virus. In particular, longitudinal analyses performed in HIV-infected individuals undergoing ATI under clinical research protocol NCT03831945 have confirmed and extended the observations that IgG3 binding to B cells increases during chronic HIV viremia and decreases when viremia is suppressed by ART. While these analyses were curtailed due to COVID-19, we hope to complete this project soon. Regarding the second related project, we previously demonstrated that IgG3 binds to B cells of HIV-infected individuals in vivo in a process that is glycan-dependent. We have pursued this line of investigation in collaboration with Dr. Heather Kalish in NIBIB by using high-throughput/low-input mass spectrometry to evaluate the highly conserved N-glycosylation site of IgG3 at amino acid position 297. We identified inflammatory IgG3 glycoforms enriched in the serum of HIV-infected individuals with chronic HIV viremia, consistent with the literature. We have also identified that a polymorphism in IgG3, adjacent to amino acid 297 and enriched in African Americans and certain individuals of Hispanic ethnicity, may be modulating the activity of IgG3. This would be consistent with our previous findings demonstrating that genetic background contributed to B-cell dysregulation in HIV disease due to cell-surface bound IgG3. We hope to complete a manuscript on these findings soon. In the third major theme, we have contributed to several collaborative efforts on HIV and other diseases of the immune system with colleagues in the LIR, as well as with other laboratories at NIAID. In 2021, these efforts have focused on COVID-19, details of which can be found in the annual report on COVID-19 research.