Serum levels of immunoglobulin free light chains in patients with chronic hepatitis C presenting cryoglobulinemia

Detection of hepatitis C virus (HCV) RNA in the peripheral blood mononuclear cells of HCV-infected patients following sustained virologic response

It is unclear whether direct-acting antiviral drugs (DAAs) result in the complete eradication of HCV infection or whether some quantities of the virus may persist after achieving a sustained virologic response (SVR). Aim The aim of this work was to study the possibility of the persistence of HCV RNA in peripheral blood mononuclear cells (PBMCs) after achieving SVR following DAA treatment. This study included 100 patients infected with HCV genotype 4, who were candidates for receiving DAAs and who achieved SVR during follow-up, as determined at 12 and/or 24 weeks following the end of treatment. All patients were subjected to demographic, biochemical and hematological assessments. Detection of HCV RNA in the serum and PBMCs and determination of the HCV genotype were performed with real-time PCR. We detected HCV RNA in the PBMCs of 20 out of 100 (20%) patients infected with HCV genotype 4, who achieved SVR. However, the persistent viral load in the PBMCs was very low (range: 400-900 U/mL; mean ± SD: 645.45 ± 153 U/mL). Multiple logistic regression analysis showed that only the higher posttreatment levels of aspartate transaminase (AST) were significantly predictive of HCV RNA persistence in the PBMCs (OR: 1.29; 95% CI: 1.08-1.55). Additionally, according to the Cox proportional hazard model, liver cirrhosis was the only significant risk factor for the persistence of HCV infection in PBMCs (HR: 5.8; 95% CI: 1.3-26.1; P < 0.02). Our results indicated the persistence of HCV RNA in some HCV patients who achieved SVR after treatment with DAAs.

Mono/polyclonal free light chains as challenging biomarkers for immunological abnormalities

Free light chain (FLC) kappa (k) and lambda (λ) consist of low molecular weight proteins produced in excess during immunoglobulin synthesis and secreted into the circulation. In patients with normal renal function, over 99% of FLCs are filtered and reabsorbed. Thus, the presence of FLCs in the serum is directly related to plasma cell activity and the balance between production and renal clearance. FLCs are bioactive molecules that may exist as monoclonal (m) and polyclonal (p) FLCs. These have been detected in several body fluids and may be key indicators of ongoing damage and/or illness. International guidelines now recommend mFLC for screening, diagnosis and monitoring multiple myeloma and other plasma cell dyscrasias. In current clinical practice, FLCs in urine indicate cast nephropathy and other renal injury, whereas their presence in cerebrospinal fluid is important for identifying central nervous system inflammatory diseases such as multiple sclerosis. Increased pFLCs have also been detected in various conditions characterized by B cell activation, i.e., chronic inflammation, autoimmune disease and HCV infection. Monitoring the coronavirus (COVID-19) pandemic by analysis of salivary FLCs presents a significant opportunity in clinical immunology worthy of scientific pursuit.

Cell Population Data and Serum Polyclonal Immunoglobulin Free Light Chains in the Assessment of COVID-19 Severity

Distinguishing between severe and nonsevere COVID-19 to ensure adequate healthcare quality and efficiency is a challenge for the healthcare system. The aim of this study was to assess the usefulness of CBC parameters together with analysis of FLC serum concentration in risk stratification of COVID-19. Materials and methods: CBC was analyzed in 735 COVID ICU, COVID non-ICU, and non-COVID ICU cases. FLC concentration was analyzed in 133 of them. Results: COVID ICU had neutrophils and lymphocytes with the greatest size, granularity, and nucleic acid content. Significant differences in concentrations of κ and λ FLCs were shown between COVID ICU and COVID non-ICU. However, no difference was found in the κ/λ ratio between these groups, and the ratio stayed within the reference value, which indicates the presence of polyclonal FLCs. FLC κ measurement has significant power to distinguish between severe COVID-19 and nonsevere COVID-19 (AUC = 0.7669), with a sensitivity of 86.67% and specificity of 93.33%. The κ coefficients’ odds ratio of 3.0401 was estimated. Conclusion: It can be concluded that the results obtained from the measure of free light immunoglobulin concentration in serum are useful in distinguishing between severe and nonsevere COVID-19.

An elevated polyclonal free light chain level reflects a strong interferon signature in patients with systemic autoimmune diseases

High amount of polyclonal free light chains (FLC) are reported in systemic autoimmune diseases (SAD) and we took advantage of the PRECISESADS study to better characterize them. Serum FLC levels were explored in 1979 patients with SAD (RA, SLE, SjS, Scl, APS, UCTD, MCTD) and 614 healthy controls. Information regarding clinical parameters, disease activity, medications, autoantibodies (Ab) and the interferon α and/or γ scores were recorded. Among SAD patients, 28.4% had raised total FLC (from 12% in RA to 30% in SLE and APS) with a normal kappa/lambda ratio. Total FLC levels were significantly higher in SAD with inflammation, active disease in SLE and SjS, and an impaired pulmonary functional capacity in SSc, while independent from kidney impairment, infection, cancer and treatment. Total FLC concentrations were positively correlated among the 10/17 (58.8%) autoantibodies (Ab) tested with anti-RNA binding protein Ab (SSB, SSA-52/60 kDa, Sm, U1-RNP), anti-dsDNA/nucleosome Ab, rheumatoid factor and negatively correlated with complement fractions C3/C4. Finally, examination of interferon (IFN) expression as a potential driver of FLC overexpression was tested showing an elevated level of total FLC among patients with a high IFNα and IFNγ Kirou's score, a strong IFN modular score, and the detection in the sera of B-cell IFN dependent factors, such as TNF-R1/TNFRSF1A and CXCL10/IP10. In conclusion, an elevated level of FLC, in association with a strong IFN signature, defines a subgroup of SAD patients, including those without renal affectation, characterized by increased disease activity, autoreactivity, and complement reduction.

Prevalence of cryoglobulinemia and cryoglobulinemic vasculitis in chronically HCV-infected Brazilian patients

INTRODUCTION AND OBJECTIVES

Cryoglobulinemia is one of the most frequent extrahepatic manifestations of chronic hepatitis C virus (HCV) infection and it may evolve to cryoglobulinemic vasculitis (CryoVas) which is a systemic vasculitis that affects small-sized vessels. The objective of this study was to evaluate the prevalence of cryoglobulinemia and CryoVas in HCV patients in São Paulo, Brazil.

MATERIALS AND METHODS

A cross-sectional study was conducted and included sixty-eight viremic HCV patients, without HIV or hepatitis B coinfection. A thorough clinical and laboratory evaluation was performed including the detection of serum cryoglobulins and measurement of serum complement components. The classification criteria for CryoVas were applied.

RESULTS

The study population comprised mainly women (61.8%) with long term HCV infection (median 11.0 years). Advanced hepatic fibrosis was detected in 20.6% (14/68) of cases. Cryoglobulins were detected in 48.5% (33/68) of HCV-patients with type III cryoglobulinemia being the most frequent. CryoVas was present in 10.3% (7/68) and the main manifestations were peripheral neuropathy (85.7%), palpable purpura (42.8%), arthralgias (42.8%) and renal involvement (42.8%). Life-threatening manifestations were rare. Low hemolytic C2, C4 and total hemolytic complement (CH100) levels were common findings in the cryoglobulinemia group. Low C4 levels were independently associated with the development of CryoVas.

CONCLUSION

A high prevalence of cryoglobulinemia and CryoVas was found in Brazilian HCV-patients. CryoVas patients mostly presented non-life-threatening manifestations, especially peripheral neuropathy. Complement abnormalities were common in patients with cryoglobulinemia and low serum C4 levels were associated with CryoVas.

Comparative Proteomic Analysis of Serum from Pigs Experimentally Infected with Trichinella spiralis, Trichinella britovi, and Trichinella pseudospiralis

Although the available proteomic studies have made it possible to identify and characterize Trichinella stage-specific proteins reacting with infected host-specific antibodies, the vast majority of these studies do not provide any information about changes in the global proteomic serum profile of Trichinella-infested individuals. In view of the above, the present study aimed to examine the protein expression profile of serum obtained at 13 and 60 days postinfection (d.p.i.) from three groups of pigs experimentally infected with Trichinella spiralis, Trichinella britovi, and Trichinella pseudospiralis and from uninfected, control pigs by two-dimensional gel electrophoresis (2-DE) followed by matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry. The comparative proteomic analysis of the T. spiralis group vs. the control group revealed 5 differently expressed spots at both 13 and 60 d.p.i. Experimental infection with T. britovi induced significant expression changes in 3 protein spots at 13 d.p.i. and in 6 protein spots at 60 d.p.i. in comparison with the control group. Paired analyses between the group infected with T. pseudospiralis and the uninfected control group revealed 6 differently changed spots at 13 d.p.i. and 2 differently changed spots at 60 d.p.i. Among these 27 spots, 15 were successfully identified. Depending on the Trichinella species triggering the infection and the time point of serum collection, they were IgM heavy-chain constant region, antithrombin III-precursor, immunoglobulin gamma-chain, clusterin, homeobox protein Mohawk, apolipoprotein E precursor, serum amyloid P-component precursor, Ig lambda chains, complement C3 isoform X1, and apolipoprotein A-I. Our results demonstrate that various Trichinella species and different phases of the invasion produce a distinct, characteristic proteomic pattern in the serum of experimentally infected pigs.

Free light chains: Eclectic multipurpose biomarker

The production of antibodies is accompanied by a slight excess of synthesis of κ and λ immunoglobulin light chains; small amounts of them are released in the peripheral blood and can also be found in various body fluids, such as synovial fluid, cerebrospinal fluid, urine and saliva. They are rapidly filtered by the glomerulus and >99% are reabsorbed from the cells of the proximal convoluted tubule, making them present in the urine in only trace amounts. The production of an excess of protein without a reason or a specific function in a biological system is rare. Free light chains, considered for years a waste product of Ig synthesis, are currently known to be very active molecules, able to bind antigens as well as whole immunoglobulin and helping to develop specific antibody affinity. The ability of free light chains to activate mast cells and then become an active part of the pathogenic mechanisms of chronic inflammatory diseases has increased interest in their clinical use, both as an attractive therapeutic target or as a biochemical marker of disease evolution or remission. This is an overview of relevant scientific interest that immunoglobulin light chains κ and λ have attracted over the years, a report on the progress in knowledge about their structure and function, with a special focus on their biological meaning and potential clinical utility in different diseases.