CD4 T-cell depletion prevents Lassa fever associated hearing loss in the mouse model

Abstract

Lassa virus (LASV) is the causative agent of Lassa fever (LF), which presents as a lethal hemorrhagic disease in severe cases. LASV-induced hearing loss in survivors is a huge socioeconomic burden, however, the mechanism(s) leading to hearing loss is unknown. In this study, we evaluate in a mouse LF model the auditory function using auditory brainstem response (ABR) and distortion product otoacoustic emissions (DPOAE) to determine the mechanisms underlying LASV-induced hearing loss. In the process, we pioneered measures of ABR and DPOAE tests in rodents in biosafety level 4 (BSL-4) facilities. Our T cell depletion studies demonstrated that CD4 T-cells play an important role in LASV-induced hearing loss, while CD8 T-cells are critical for the pathogenicity in the acute phase of LASV infection. Results presented in this study may help to develop future countermeasures against acute disease and LASV-induced hearing loss.

Depletion of CD4 and CD8 T Cells Reduces Acute Disease and Is Not Associated with Hearing Loss in ML29-Infected STAT1-/- Mice

“…Mice were intraperitoneally injected with either sterile PBS or up to 10 5 PFU of ML29 in 100 μL of sterile PBS. Mice that were depleted of T cells received 100 μg of InVivoPlus anti-mouse CD4 (GK1.5, BioXCell, Lebanon, NH, USA) and/or anti-mouse CD8a monoclonal antibodies (mAb) (53–6.7, BioXCell) intraperitoneally three and one day prior to infection as previously described [ 19 ]. Mock depletions were achieved using InVivoPlus rat IgG2b isotype control and/or InVivoPlus rat IgG2a isotype control (BioXCell).…”

“…The Auditory Brainstem Response (ABR) analysis was conducted using the Intelligent Hearing System SmartEP software as previously described [ 19 , 23 ]. In total, 256 responses elicited by a click stimulus (broad band frequency, peak range 0.5–16 kHz) were averaged and recorded in a series of descending 5–10 decibel (dB) steps.…”

“…The Distortion Product Otoacoustic Emission (DPOAE) analysis was conducted using the Starkey DP2000 system (Starkey Laboratories, Eden Prairie, MN, USA), as previously described [ 19 , 23 ]. A modified ear probe, adjusted to fit the mouse auditory canal, was used.…”

“…Current research into these mechanisms implicate the involvement of the immune response, notably the LASV-specific T cells, in the protection against disease and the development of SNHL. While an early and robust T cell response against LASV is known to be important for both protection against and recovery from LF in both humans and NHPs [ 13 , 14 , 15 ], these LASV-specific T cells have also been implicated in acute disease as well as sequela in several experimental models [ 16 , 17 , 18 , 19 ]. Previous work with nonhuman primates demonstrates that LF survivors may develop hearing loss, as measured by the Brainstem Auditory Evoked Response [ 16 ].…”

“…Currently, there is a reliable murine model for SNHL; STAT1-/- mice surviving LASV infection develop hearing loss at a high rate, as measured by the acoustic startle response [ 17 ]. Furthermore, we recently published that more clinically relevant testing methods, auditory brainstem response (ABR) and distortion product otoacoustic emission (DPOAE) testing, are able to detect hearing loss in STAT1-/- mice surviving LASV infection and that this hearing loss is likely CD4 T cell-mediated [ 19 ]. These studies suggest the involvement of the LASV-specific immune response in the development of this particular sequela.…”