Close Encounters of the Viral Kind: Cross-Kingdom Synergies at the Host-Pathogen Interface

Secondary streptococcal infection following influenza

Secondary bacterial infection following influenza A virus (IAV) infection is a major cause of morbidity and mortality during influenza epidemics. Streptococcus pneumoniae has been identified as a predominant pathogen in secondary pneumonia cases that develop following influenza. Although IAV has been shown to enhance susceptibility to the secondary bacterial infection, the underlying mechanism of the viral-bacterial synergy leading to disease progression is complex and remains elusive. In this review, cooperative interactions of viruses and streptococci during co- or secondary infection with IAV are described. IAV infects the upper respiratory tract, therefore, streptococci that inhabit or infect the respiratory tract are of special interest. Since many excellent reviews on the co-infection of IAV and S. pneumoniae have already been published, this review is intended to describe the unique interactions between other streptococci and IAV. Both streptococcal and IAV infections modulate the host epithelial barrier of the respiratory tract in various ways. IAV infection directly disrupts epithelial barriers, though at the same time the virus modifies the properties of infected cells to enhance streptococcal adherence and invasion. Mitis group streptococci produce neuraminidases, which promote IAV infection in a unique manner. The studies reviewed here have revealed intriguing mechanisms underlying secondary streptococcal infection following influenza. This article is protected by copyright. All rights reserved.

Associations Between Salivary Bacteriome Diversity and Salivary Human Herpesvirus Detection in Early Childhood: A Prospective Cohort Study

BACKGROUND

The bacteriome is associated with susceptibility to some eukaryotic viruses, but no study has examined associations between the salivary bacteriome and human herpesviruses (HHVs). We provide new prevalence and incidence estimates for salivary herpesviruses detection and estimate associations with bacteriome diversity in young children.

METHODS

Salivary samples collected at ages ~2, 8, 12, and 24 months from 153 children participating in the Center for Oral Health Research in Appalachia cohort 2 (COHRA2) were screened for HHVs using the Fast-Track Neuro9 multiplex PCR assay, and for the bacteriome using 16S rRNA amplicon sequencing. We used Cox proportional hazard models to test for associations between the salivary bacteriome and hazards of cytomegalovirus (CMV) and human herpesvirus-6 (HHV6).

RESULTS

CMV, HHV6, and Epstein-Barr virus (EBV) were detected at all visits. Human herpesvirus-7 (HHV7) was first detected at the 8-month visit and herpes simplex virus 1 (HSV1) was only detected at the 12-month visit. Varicella-zoster virus, herpes simplex virus 2, and human herpesvirus-8 were never detected. HHV6 (24-month cumulative incidence: 73.8%) and CMV (24-month cumulative incidence: 32.3%) were detected most frequently. Increasing salivary bacteriome diversity was associated with longer survival to first detection of CMV (hazard ratio [95% CI]: 0.24 [0.12, 0.49]) and HHV6 (hazard ratio [95% CI]: 0.24 [0.13, 0.44]).

CONCLUSION

CMV, HHV6, EBV, HHV7, and HSV1 were detected in the saliva during the first 2 years of life. Time to first detection of CMV and HHV6 was associated with salivary bacteriome diversity, suggesting a possible interaction between HHVs and the salivary bacteriome.