Analysis of Chlamydia pneumoniae infection in mononuclear cells by reverse transcription-PCR targeted to chlamydial gene transcripts

Effect of Past Chlamydophila pneumoniae Infection on the Short-Time Mortality of COVID-19: A Retrospective Cohort Study

BACKGROUND

Although Chlamydophila pneumoniae (CP)is known to play a role in atherosclerosis and endothelial injury, its past infection on the mortality of coronavirus disease 2019 (COVID-19), which was also reported to be a vascular disease, remains unknown.

METHODS

In this retrospective cohort study, we examined 78 COVID-19 patients and 32 bacterial pneumonia patients who visited a tertiary emergency center in Japan between April 1, 2021, and April 30, 2022. CP antibody levels, including IgM, IgG, and IgA, were measured.

RESULTS

Among all patients, the CP IgA-positive rate was significantly associated with age (P = 0.002). Between the COVID-19 and non-COVID-19 groups, no difference in the positive rate for both CP IgG and IgA was observed (P = 1.00 and 0.51, respectively). The mean age and proportion of males were significantly higher in the IgA-positive group than in the IgA-negative group (60.7 vs. 75.5, P = 0.001; 61.5% vs. 85.0%, P = 0.019, respectively). Smoking and dead outcomes were significantly higher both in the IgA-positive group and IgG-positive group (smoking: 26.7% vs. 62.2, P = 0.003; 34.7% vs. 73.1%, P = 0.002, dead outcome: 6.5% vs. 29.8%, P = 0.020; 13.5% vs. 34.6%, P = 0.039, respectively). Although the log-rank test revealed higher 30-day mortality in the IgG-positive group compared to the IgG-negative group (P = 0.032), Cox regression analysis demonstrated no significant difference between the IgG-positive and negative groups (hazard ratio (HR) = 4.10, 95%CI = 0.94-18.0, P = 0.061).

CONCLUSION

The effect of past CP infection on 30-day mortality in COVID-19 patients was not obvious.

Effect of different reverse transcription aproaches in Pru p 3 transcripts semiquantitative amplification

Reverse transcriptase transcribes the cDNA based on its previous extraction and standardization. Reverse transcription step is considered to be critical in the workflow of quantification of transcribed genes. The aim of the study was to extract total RNA by different methods and to analyse the results of the subsequent reverse transcription reaction when different commercial RT kits were used to process RNA extracted from pulp of matured peach fruit. Mature peach pulp was used in the study. The fruit of variety Vistarich was collected in summer 2017 in the orchard of Dvory nad Žitavou. Two RNA extraction methods, TRIzol® Reagent and GeneJET Plant RNA Purification Kit, were tested in to determine the suitable method for peach fruit RNA extraction. Three different cDNA reagent sets were used to transcribe 115 ng/500 ng total RNA or 11 ng/115 ng, respectively. Both variants of the primers, random hexamers as well as oligo (dT) 18, were used to anneal the target mRNA of Pru p 3 allergen following the manufacturer instructions. No specific effect was obtained in the case of peach fruit when using ethanol-extracted tissue treatment and the effect of the used extraction method was more significant. The A260/230 ratios were similar for three from four tested methods. In the case of these three methods, the A260/A230 ratios for all the extracted samples were higher than 1.9 which indicates high purity without contamination by polyphenols and polysaccharides. The specificity of obtained amplicons was proved by restriction cleavage using Tse I restriction endonuclease. This provided the cleavage of the 179 bp long product in all amplicons. Working with mature fruit meet a specific situation in the field of RNA extraction and subsequently all the downstream applications. That is, why choosing the most fitting methods and kits is a crucial step. Here, the method for the semi-quantitative analysis of the Pru p 3 allergen expressions was set up in the way that will be directly applicable for Pru p 3 expression analyses. 

Chlamydia psittaci reference genes for normalisation of expression data differ depending on the culture conditions and selected time points during the chlamydial replication cycle

Introduction: Chlamydia psittaci is a gram-negative obligate intracellular pathogen of birds. Poultry infections lead to economic losses and can be transmitted to humans. No vaccine is available and the bacterium-host cell interaction is not completely understood. Replicating bacteria cause pneumonia, but C. psittaci can also be non-replicating and persistent inside the cytoplasm of avian cells. RT-qPCR provides insight into the molecular pathogenesis of both active replicating and persistent Chlamydia psittaci in birds, but requires identification of stably expressed reference genes to avoid biases. Material and Methods: We investigated the expression stability of 10 C. psittaci candidate reference genes for gene expression analysis during normal growth and penicillin-induced persistence. C. psittaci Cal10 was cultured in HeLa229 and RNA was extracted. The expression level of each candidate was examined by RT-qPCR and Cq values were analysed using geNorm. Results: The genes tyrS, gidA, radA, and 16S rRNA ranked among the most stably expressed. The final selected reference genes differed according to the bacterial growth status (normal growth versus persistent status), and the time points selected during the duration of the normal chlamydial developmental cycle. Conclusion: The study data show the importance of systematic validation of reference genes to confirm their stability within the strains and under the conditions selected.

Chlamydia pneumoniae-Mediated Inflammation in Atherosclerosis: A Meta-Analysis

Several studies have attempted to relate the C. pneumoniae-mediated inflammatory state with atherosclerotic cardiovascular diseases, providing inconsistent results. Therefore, we performed a meta-analysis to clarify whether C. pneumoniae may contribute to the pathogenesis of atherosclerosis by enhancing inflammation. 12 case-control, 6 cross-sectional, and 7 prospective studies with a total of 10,176 patients have been included in this meta-analysis. Odds Ratio (OR) with a 95% confidence interval was used to assess the seroprevalence of C. pneumoniae and differences between levels of inflammatory markers were assessed by standard mean differences. Publication bias was performed to ensure the statistical power. hsCRP, fibrinogen, interleukin- (IL-) 6, TNF-α, and IFN-γ showed a significant increase in patients with atherosclerosis compared to healthy controls (P < 0.05), along with a higher seroprevalence of C. pneumoniae (OR of 3.11, 95% CI: 2.88–3.36, P < 0.001). More interestingly, hsCRP, IL-6, and fibrinogen levels were significantly higher in C. pneumoniae IgA seropositive compared to seronegative atherosclerotic patients (P < 0.0001). In conclusion, the present meta-analysis suggests that C. pneumoniae infection may contribute to atherosclerotic cardiovascular diseases by enhancing the inflammatory state, and, in particular, seropositivity to C. pneumoniae IgA, together with hsCRP, fibrinogen, and IL-6, may be predictive of atherosclerotic cardiovascular risk.

Considerations for accurate gene expression measurement by reverse transcription quantitative PCR when analysing clinical samples

Reverse transcription quantitative PCR is an established, simple and effective method for RNA measurement. However, technical standardisation challenges combined with frequent insufficient experimental detail render replication of many published findings challenging. Consequently, without adequate consideration of experimental standardisation, such findings may be sufficient for a given publication but cannot be translated to wider clinical application. This article builds on earlier standardisation work and the MIQE guidelines, discussing processes that need consideration for accurate, reproducible analysis when dealing with patient samples. By applying considerations common to the science of measurement (metrology), one can maximise the impact of gene expression studies, increasing the likelihood of their translation to clinical tools.

Infection of human monocytes by Chlamydia pneumoniae and Chlamydia trachomatis: an in vitro comparative study

Background

An increasing number of studies suggest that chlamydiae can infect immune cells. The altered immune cell function could contribute to the progression of several chronic inflammatory diseases.

The aim of this study was to comparatively evaluate Chlamydia pneumoniae (CP) and Chlamydia trachomatis (CT) interactions with in vitro infected human blood monocytes.

Results

Fresh isolated monocytes were infected with viable CP and CT elementary bodies and infectivity was evaluated by recultivating disrupted monocytes in permissive epithelial cells.

The production of reactive oxygen and nitrogen species was studied in the presence of specific fluorescent probes. Moreover, TNF-α, INF-α, INF-β and INF-γ gene expression was determined.

CT clearance from monocytes was complete at any time points after infection, while CP was able to survive up to 48 hours after infection. When NADPH oxydase or nitric oxide synthase inhibitors were used, CT infectivity in monocytes was restored, even if at low level, and CT recovery’s rate was comparable to CP one.

CT-infected monocytes produced significantly higher levels of reactive species compared with CP-infected monocytes, at very early time points after infection. In the same meanwhile, TNF-α and INF-γ gene expression was significantly increased in CT-infected monocytes.

Conclusions

Our data confirm that CP, but not CT, is able to survive in infected monocytes up to 48 hours post-infection. The delay in reactive species and cytokines production by CP-infected monocytes seems to be crucial for CP survival.

Laboratory diagnosis of persistent human chlamydial infection

Diagnostic assays for persistent chlamydial infection are much needed to conduct high-quality, large-scale studies investigating the persistent state in vivo, its disease associations and the response to therapy. Yet in most studies the distinction between acute and persistent infection is based on the interpretation of the data obtained by the assays developed to diagnose acute infections or on complex assays available for research only and/or difficult to establish for clinical use. Novel biomarkers for detection of persistent chlamydial infection are urgently needed. Chlamydial whole genome proteome arrays are now available and they can identify chlamydial antigens that are differentially expressed between acute infection and persistent infection. Utilizing these data will lead to the development of novel diagnostic assays. Carefully selected specimens from well-studied patient populations are clearly needed in the process of translating the proteomic data into assays useful for clinical practice. Before such antigens are identified and validated assays become available, we face a challenge of deciding whether the persistent infection truly induced appearance of the proposed marker or do we just base our diagnosis of persistent infection on the presence of the suggested markers. Consequently, we must bear this in mind when interpreting the available data.

Neutrophil gelatinase-associated lipocalin and interleukin-10 regulate intramacrophage Chlamydia pneumoniae replication by modulating intracellular iron homeostasis

Neutrophil gelatinase-associated lipocalin (NGAL/Lipocalin-2/Lcn-2) is a 25 kDa protein which is involved in host defence against certain Gram negative bacteria upon binding of iron loaded bacterial siderophores thereby limiting the availability of this essential nutrient to bacteria resulting in inhibition of their growth and pathogenicity. As iron is important for the growth of the intracellular bacterium Chlamydia pneumoniae we questioned whether Lcn-2 affects the course of this infection. We employed primary peritoneal macrophages obtained from wildtype and Lcn-2 −/− mice and RAW 264.7 cells which were infected with C. pneumoniae. In addition, we studied C. pneumoniae multiplication in vivo in mice receiving diets with varying iron contents. We analyzed C. pneumoniae numbers by immunohistochemistry and RT-PCR and studied the expression of iron metabolism and cytokine genes by RT-PCR, Western blot or ELISA.

Infection with Chlamydiae ex vivo and in vivo revealed a significantly higher bacterial growth in peritoneal macrophages of Lcn-2 −/− than of wildtype mice. These differences were significantly more pronounced upon iron challenge, which stimulated bacterial growth. Accordingly, treatment with an anti-Lnc-2 antibody increased whereas addition of recombinant Lcn-2 reduced bacterial growth in infected macrophages. When investigating the underlying mechanisms we observed partly different expression of several iron metabolism genes between Lcn-2 +/+ and Lcn-2 −/− macrophages and most strikingly an increased formation of the anti-inflammatory cytokine IL-10 by Lcn-2 −/− macrophages. Upon treatment with an anti-IL10 antibody we experienced a significant increase of Chlamydial growth within Lcn-2 −/− macrophages along with a reduction of the major iron storage protein ferritin. Herein we provide first time evidence that Lcn-2 is involved in host defence against Chlamydia presumably by limiting the availability of iron to the pathogen. In the absence of Lcn-2, increased formation of IL-10 exerts protective effects by increasing the intracellular formation of ferritin, thereby reducing the access of iron for bacteria.

Recent publications in medical microbiology and immunology: a retrospective

A look back is done to some clinical and basic research activities recently published in medical microbiology and immunology. The review covers clinical experiences and in vitro experiments to understand the emergency, pathogenicity, epidemic spread, and vaccine-based prevention of avian and swine-origin flu. Some new developments and concepts in diagnosis, (molecular) epidemiology, and therapy of AIDS, viral hepatitis C, and herpesvirus-associated diseases are outlined. Regulation of immune system has been discussed in a special issue 2010 including some aspects of CNS affections (measles). Mycobacterial infection and its prevention by modern recombinant vaccines have reached new interest, as well as new concepts of vaccination and prophylaxis against several other bacteria. Adaptation to host niches enables immune escape (example brucella) and determines virulence (example N. meningitidis). Chlamydia pneumoniae, previously considered to trigger atherosclerosis, is hypothetically associated to Alzheimer disease, while CMV, another putative trigger of atherosclerosis, gains evidence of oncomodulation in CNS tumor diseases. In terms of globalization, exotic virus infections are increasingly imported from southern countries.