Multiple treatment interruptions and protecting HIV-specific CD4 T cells enable durable CD8 T cell response and viral control.

Human Immunodeficiency Virus (HIV) remains a global health challenge, and novel approaches to improve HIV control are significantly important. The cell and gene therapy product AGT103-T was previously evaluated (NCT04561258) for safety, immunogenicity, and persistence in seven patients for up to 180 days post infusion. In this study, we sought to investigate the impact of AGT103-T treatment upon analytical treatment interruptions (ATIs). Six patients previously infused with AGT103-T were enrolled into an ATI study (NCT05540964), wherein they suspended their antiretroviral therapy (ART) until their viral load reached 100,000 copies/mL in two successive visits, or their CD4 count was reduced to below 300 cells/µL. During the ATI, all patients experienced viral rebound followed by a notable expansion in HIV specific immune responses. The participants demonstrated up to a five-fold increase in total CD8 counts over baseline approximately 1-2 weeks followed by the peak viremia. This coincided with a rise in HIV-specific CD8 T cells, which was attributed to the increase in antigen availability and memory recall. Thus, the protocol was amended to include a second ATI with the first ATI serving as an "auto-vaccination." Four patients participated in a second ATI. During the second ATI, the Gag-specific CD8 T cells were either maintained or rose in response to viral rebound and the peak viremia was substantially decreased. The patients reached a viral set point ranging from 7,000 copies/mL to 25,000 copies/mL. Upon resuming ART, all participants achieved viral control more rapidly than during the first ATI, with CD4 counts remaining within 10% of baseline measurements and without any serious adverse events or evidence of drug resistance. In summary, the rise in CD8 counts and the viral suppression observed in 100% of the study participants are novel observations demonstrating that AGT103-T gene therapy when combined with multiple ATIs, is a safe and effective approach for achieving viral control, with viral setpoints consistently below 25,000 copies/mL and relatively stable CD4 T cell counts. We conclude that HIV cure-oriented cell and gene therapy trials should include ATI and may benefit from designs that include multiple ATIs when induction of CD8 T cells is required to establish viral control.

Targeting lymphocyte Peyer's patch adhesion molecule-1: a relay approach to gut immunization.

Targeting vaccines to dendritic cells (DCs) can enhance responses to weak vaccine antigens. Although there are molecules that are relatively specific for the various DC subsets, there are none that are both region-specific and DC-specific. This has provided some limitation to targeting regional DC populations. We proposed that these limits could be overcome by targeting antigens not to the DC subsets directly but to cells that persistently seek out and closely interact with DCs, namely lymphocytes. To investigate this hypothesis, we targeted antigens to a unique population of gut-homing lymphocytes and then looked at the induction of immune responses at this site. Using an anti-LPAM-1 (Lymphocyte Peyer's patch adhesion molecule-1; alpha(4)beta(7) integrin) monoclonal antibody (mAb) as a model antigen, we found that targeting gut-homing lymphocytes could significantly elevate the gut mucosal IgA response. Moreover, such a strategy greatly elevated the systemic IgG as well as IgA response. We found that LPAM-1-targeting enhanced the localization of antigen to both the systemic and mucosal lymphoid compartments where both IgA and IgG responses were induced. We also found that any parenteral route of delivery sufficed. Overall, targeting unique populations of lymphocytes may provide a strategy for ferrying antigen to sites that such lymphocytes home to.

Bypassing luminal barriers, delivery to a gut addressin by parenteral targeting elicits local IgA responses.

Induction of mucosal immunity, particularly to subunit vaccines, has been problematic. The primary hurdle to successful mucosal vaccination is the effective delivery of vaccine antigen to the mucosal associated lymphoid tissue. Physical and chemical barriers restrict antigen access and, moreover, immune responses induced in the mucosa can be biased towards tolerance or non-reactivity. We proposed that these difficulties could be circumvented by targeting antigen to the gastrointestinal associated lymphoid tissue via systemic (parenteral) rather than alimentary routes, using antibodies specific for the mucosal addressin cellular adhesion molecule-1 (MAdCAM). After intravenous or intramuscular injection of such rat antibodies in mice, we found a greatly enhanced (up to 3 logs) anti-rat antibody response. MAdCAM targeting induces a rapid IgA antibody response in the gut and vastly improves the systemic antibody response. Targeting also enhanced T cell proliferation and cytokine responses. Parenteral targeting of mucosal addressins may represent a generic technique for bypassing mucosal barriers and eliminating the need for adjuvants in the induction of proximal and systemic immunity.