Zika Virus Mucosal Infection Provides Protective Immunity

Abstract

Zika virus (ZIKV) is a major human pathogen. ZIKV can replicate in female and male reproductive organs, thus facilitating the human-human transmission cycle. Viral shedding in the semen can increase the risk of ZIKV transmission through sexual mode. Therefore, the vaginal and anorectal mucosa are relevant sites for ZIKV infection. However, the pathobiology of ZIKV transmission through the rectal route is not well understood. Here, we utilize a mouse model system to investigate the immunopathological consequences following ZIKV infection of the rectal mucosa compared to a subcutaneous route of infection. We show that ZIKV-rectal inoculation results in viremia with subclinical infection. ZIKV infects the mucosal epithelium and submucosal dendritic cells, inducing immune and inflammatory cell infiltration. Rectal transmission of ZIKV resulted in the generation of serum-neutralizing antibody responses. Mass cytometry analyses of splenocytes showed a significantly reduced level of inflammatory monocyte and neutrophil cellular responses in the rectal route group. Furthermore, immunological priming through the rectal mucosa with an attenuated ZIKV strain resulted in significant protection from lethal subcutaneous ZIKV challenge, further eliciting robust memory CD4-positive (CD4⁺) and CD8⁺ T-cell and ZIKV-specific serum-neutralizing antibody responses. Thus, our study provides deeper immunopathobiological insights on rectal transmission and highlights a rational strategy for mucosal immunization. This model system recapitulates clinical aspects of human ZIKV disease outcome, where most infections are well controlled and result in subclinical and asymptomatic outcomes.IMPORTANCE Zika virus is a clinically significant human pathogen that is primarily transmitted and spread by Aedes species mosquitoes but is also sexually transmissible. The recent pandemic in the Americas led to an unprecedented increase of newborn babies with developmental brain and eye abnormalities. To date, there is no licensed vaccine or therapeutic intervention available for the fight against ZIKV. Understanding the sexual transmission of ZIKV through vaginal and rectal routes is necessary to restrict virus transmission and spread. This study examines the early immunological and pathological consequences of rectal and subcutaneous routes of ZIKV infection using a mouse model. We characterized the primary target cells of ZIKV infection and the subsequent mucosal immune responses to infection, and we demonstrate the protective effect of mucosal rectal immunization using an attenuated ZIKV strain. This mucosal vaccination approach can be further developed to prevent future ZIKV outbreaks.

Keywords: Zika virus; immunization; rectal infection.