Effects of Antiretroviral Treatment on Central and Peripheral Immune Response in Mice with EcoHIV Infection

Abstract

HIV infection is an ongoing global health issue, despite increased access to antiretroviral therapy (ART). People living with HIV (PLWH) who are virally suppressed through ART still experience negative health outcomes, including neurocognitive impairment. It is increasingly evident that ART may act independently or in combination with HIV infection to alter the immune state, though this is difficult to disentangle in the clinical population. Thus, these experiments used multiplexed chemokine/cytokine arrays to assess peripheral (plasma) and brain (nucleus accumbens; NAc) expression of immune targets in the presence and absence of ART treatment in the EcoHIV mouse model. The findings identify the effects of EcoHIV infection and of treatment with bictegravir (B), emtricitabine (F), and tenofovir alafenamide (TAF) on the expression of numerous immune targets. In the NAc, this included EcoHIV-induced increases in IL-1α and IL-13 expression and B/F/TAF-induced reductions in KC/CXCL1. In the periphery, EcoHIV suppressed IL-6 and LIF expression, while B/F/TAF reduced IL-12p40 expression. In the absence of ART, IBA-1 expression was negatively correlated with CX3CL1 expression in the NAc of EcoHIV-infected mice. These findings identify distinct effects of ART and EcoHIV infection on peripheral and central immune factors and emphasize the need to consider ART effects on neural and immune outcomes.

Keywords: ART; EcoHIV; HIV; cytokine; immune response; microglia; mouse model; nucleus accumbens.

Figure 1

Mouse model of EcoHIV infection. (A) Timeline of experiments (created with Biorender.com). Mice were matched based on sex into EcoHIV or sham control groups and for treatment with B/F/TAF. (B) Copies of viral DNA at the euthanasia timepoint (week 5 of infection). The number of copies of viral DNA per 10⁶ spleen cells did not differ between EcoHIV-infected mice that were treated with vehicle (n = 11) versus B/F/TAF (n = 12). No DNA copies were detected in the seven representative sham mice. (C) Body weight changes versus baseline weight throughout 5 weeks of the experiment. No effects of EcoHIV infection or B/F/TAF treatment were observed on weight change. A main effect of day was observed, such that weight increased over time. Circles and square represent sham and EcoHIV mice; open and closed symbols represent B/F/TAF- and vehicle-treated mice, respectively. Bars represent mean ± SEM. n = 11–12/group.

Figure 2

EcoHIV infection and B/F/TAF impacted immune factors in the NAc. EcoHIV, but not B/F/TAF treatment, increased the expression of (A) IL-1α and (B) IL-13 in the NAc. (C) B/F/TAF treatment reduced expression of CXCL1/KC in the Nac, independent of EcoHIV infection. EcoHIV and B/F/TAF interacted to impact (D) IFNγ, (E) IL-7, (F) IL-10, and (G) RANTES expression levels, with selective reductions in IL-7 observed in B/F/TAF-treated mice with EcoHIV, and increased IL-10 expression levels only in vehicle-treated EcoHIV-infected mice. Square and circle symbols represent sham and EcoHIV mice; close and open symbols represent vehicle- and B/F/TAF-treated mice, respectively. Bars represent mean ± SEM. n = 5–6/group. * p < 0.05.

Figure 3

Principal component analysis (PCA) indicated distinct NAc immune profiles based on EcoHIV infection and B/F/TAF treatment. (A) Distribution along the first principal component (PC1) was driven by IL-1α, IFNγ, IL-10, and RANTES (“Neuroimmune Cluster”), explaining 52.9% of the cumulative variance. The second principal component (PC2) accounted for 19% of the variance and was positively correlated with IL-13, but negatively correlated with IL-7 expression. Sham vs. EcoHIV status is indicated by color. Vehicle vs. B/F/TAF treatment is indicated by symbol size. (B). The expression profiles of EcoHIV-infected and sham control mice are minimally overlapping, with distribution along the PC2 axis corresponding with EcoHIV infection status, with EcoHIV infection associated with High IL-13 and sham associated with High IL-7. Distribution along PC1 corresponded with B/F/TAF treatment and treatment shifted the immune profile to lower neuroimmune factor expression in EcoHIV-infected mice. n = 5–6/group.

Figure 4

EcoHIV infection and B/F/TAF impacted immune factors in week 5 plasma. EcoHIV infection suppressed the expression of (A) IL-6 and (B) LIF in the plasma, independent of B/F/TAF treatment. (C) B/F/TAF treatment reduced IL-12p40 expression in the plasma of mice, independent of EcoHIV infection. (D) EcoHIV and B/F/TAF interacted to alter plasma IL-5 expression, such that IL-5 was reduced only in EcoHIV-infected mice treated with B/F/TAF. Bars represent mean ± SEM. Square and circle symbols represent sham and EcoHIV mice; closed and open symbols represent vehicle- and B/F/TAF-treated mice, respectively. n = 11–12/group. * p < 0.05, ** p < 0.01.

Figure 5

EcoHIV infection determined the relationship between Iba-1 and NAc expression of immune factors. When compared using an ANOVA, no effect of EcoHIV infection or B/F/TAF was observed on NAc (A) Iba-1 expression or (B) CX3CL1 expression. (C) Representative Iba-1, CX3CL1, and internal control GAPDH Western blots. Based on an a priori hypotheses, the overall mean NAc expression of Iba-1 and CX3CL1 were compared between vehicle-treated, Sham- and EcoHIV-infected mice, then simple linear regression was performed between Iba-1 and CX3CL1 in sham-Veh and EcoHIV-Veh mice, respectively. There was no relationship between Iba-1 and CX3CL1 expression in sham mice (D), while expression was negatively correlated in EcoHIV-infected mice (E). n = 11–12/group. * p < 0.05.