Role of gut microbiota in infectious and inflammatory diseases

Thousands of microorganisms compose the human gut microbiota, fighting pathogens in infectious diseases and inhibiting or inducing inflammation in different immunological contexts. The gut microbiome is a dynamic and complex ecosystem that helps in the proliferation, growth, and differentiation of epithelial and immune cells to maintain intestinal homeostasis. Disorders that cause alteration of this microbiota lead to an imbalance in the host’s immune regulation. Growing evidence supports that the gut microbial community is associated with the development and progression of different infectious and inflammatory diseases. Therefore, understanding the interaction between intestinal microbiota and the modulation of the host’s immune system is fundamental to understanding the mechanisms involved in different pathologies, as well as for the search of new treatments. Here we review the main gut bacteria capable of impacting the immune response in different pathologies and we discuss the mechanisms by which this interaction between the immune system and the microbiota can alter disease outcomes.

A 28-year study of human parainfluenza in Rio Grande do Sul, Southern Brazil

PROBLEM

Human parainfluenza virus (hPIV) is an important pathogen in respiratory infections, however the health burden of hPIV is underestimated. This study describes the infections by hPIV1-3 in Rio Grande do Sul, Brazil, from 1990 to 2017, providing data of the frequency and seasonality of cases and associated clinical symptoms.

METHOD OF STUDY

Nasopharyngeal samples of patients with respiratory infection were collected, clinical data were analyzed, and immunofluorescence was used to detect hPIV.

RESULTS

Respiratory viruses were detected in 33.63% of respiratory infections. In a total of 11 606 cases of viral respiratory infection, 781 were positive for hPIV; hPIV prevalence ranged from 2.14% to 27% of viral respiratory infections. hPIV1 circulates mainly during fall; hPIV3 circulation, in turn, starts in fall and peaks during spring; and cases of hPIV2 are reported along the year, with peaks in fall and early spring. The most affected age group was children, with hPIV prevalence of 74.23% in patients for less than 1 year. A higher proportion of girls were infected than boys, however, no difference by sex was observed considering all age groups. The most frequent type was hPIV3, especially in hospitalized patients. Both hPIV1 and 3 were associated with dyspnea, while hPIV2 caused mild symptoms mainly in nonhospitalized patients. Nineteen fatalities occurred, 89.5% of them associated with risk factors (prematurity; chronic diseases; age, <1 or >60 years).

CONCLUSION

hPIV causes a high number of respiratory infections, leading to hospitalization especially in children; epidemiological and surveillance studies are important for the control and management of respiratory infections.

The inverted CD4:CD8 ratio is associated with gender-related changes in oxidative stress during aging

Aging has been associated with increased generation of free radicals as well as immunosenescence. Previous studies have identified older individuals with inverted T CD4:CD8 cell ratio and increased immunity to cytomegalovirus (CMV). Here, we investigated markers of oxidative stress and antioxidant defences in older individuals with inverted CD4:CD8 T-cell ratio. Sixty-one subjects were identified with inverted CD4:CD8 ratio. Older individuals with a CD4:CD8 ratio <1 had increased levels of plasma advanced oxidation protein products (AOPP) and ferric reducing ability of plasma (FRAP), but reduced levels of thiobarbituric acid reactive substances (TBARS) as compared to subjects with normal CD4:CD8 ratio. The CMV IgG serology was negatively correlated with CD4:CD8 ratio. These markers were more evident among elderly men than women. Our data suggest a close relationship between chronic CMV infection and oxidative profile in older individuals in the midst of its influence on the peripheral T-cell subsets.

The inverted CD4:CD8 ratio is associated with cytomegalovirus, poor cognitive and functional states in older adults

BACKGROUND

Some premature features of immunosenescence have been associated with persistent viral infections and altered populations of T cells. In particular, the inverted T CD4:CD8 ratio has been correlated with increased morbidity and mortality across different age groups.

OBJECTIVE

Here, we investigated the role of persistent viral infections, cognitive and functional states as predictors of inverted CD4:CD8 ratio of older adults in a developing country.

METHODS

Three hundred and sixty community-dwelling older adults (aged 60-103 years) were recruited. Cognitive function was evaluated by the Instrument of Brief Neuropsychological Assessment and Mini-Mental State Examination inventory. Functional Activities Questionnaire was used to determine activities of daily living. Cytomegalovirus (CMV) and Epstein-Barr virus (EBV) serologies were determined by ELISAs. Peripheral blood was assessed for lymphocyte subsets by flow cytometry (CD4+, CD8+, NK, NKT, B and CD8+CD28-).

RESULTS

Fifty-nine individuals were identified with CD4:CD8 ratio <1, and had increased IgG titers to CMV (p < 0.01), but not to EBV, compared to subjects with CD4:CD8 ratio >1. The older adults with inverted CD4:CD8 ratio had impairments in some cognitive dimensions and had more functional disability and dependency (p = 0.01) than subjects with CD4:CD8 ratio >1. The lymphocyte subsets did not vary between groups. The increased CMV-IgG titers alone contributed to 8× higher chance to invert CD4:CD8 T cell ratio (OR 8.12, 95% CI 1.74-37.88, p < 0.01).

CONCLUSION

Our data further indicate the role of CMV on circulating T cells, poor cognition and functional disability/dependency during aging.