TCR-signals downstream adversely correlate with the survival signals of memory CD8+ T cells under homeostasis.

The significance of self-peptide-MHC-I/TCR (SMT) interaction in the survival of CD8+ T cells during naïve- and developmental-stages is well documented. However, the same for the memory stage is contentious. Previous studies have attempted to address the issue using MHC-I or TCR deficient systems, but inconsistent findings with memory CD8+ T cells of different TCR specificities have complicated the interpretation. Differential presence and/or processing of TCR-signals downstream in memory CD8+ T cells of different TCR specificities could be thought of as a reason. In this study, we examined the TCR-signals downstream in memory CD8+ T cells and compared them to the presence of survival-related signals (Annexin-V, Bcl-2, and Ki-67). We categorically tracked foreign antigen-experienced memory CD8+ T (TM) cells generated after Plasmodium pre-erythrocytic-stage malaria infection in C57BL/6 mice. Interestingly, we found that memory CD8+ T cells had more TCR-signals downstream than naive cells. We reasoned and attributed the increased expression of cell adhesion molecules to the enhanced TCR-signaling. TCR-signals downstream correlate more closely with survival signals in naive CD8+ T cells than with death signals in TM cells. Further investigation using antigen-specific CD8+ T cells and diverse infection systems would aid in conceptualizing the findings.

Infectious sporozoite challenge modulates radiation attenuated sporozoite vaccine-induced memory CD8+ T cells for better survival characteristics.

Radiation attenuated sporozoite (RAS), a whole-parasite vaccine approach, provides sterile protection against malaria. However, RAS immunization does not confer protection for long, and that has been correlated with the waning parasite-induced memory CD8+ T-cell responses. Interestingly, an intermittent infectious (wild type) sporozoite challenge to the RAS-vaccinated mice lengthened the protection period from 6 to 18 months. Herein, we have studied the changes induced by the infectious sporozoites in RAS-induced memory CD8+ T cells for conferring lengthened protection. We observed that the infectious sporozoite challenge boosted the frequency of foreign antigen-experienced memory CD8+ T cells. In those CD8+ T cells, it has reduced the Annexin-V reactivity, raised Bcl-2 expression, and also more cells undergo homeostatic proliferation (Ki-67+ ). It has also scaled down the frequency of Nur77 and CX3CR1 high expressing cells in those memory CD8+ T-cell populations which we further correlated with better survival signals.

Development of Stable Chimeric IL-15 for Trans-Presentation by the Antigen Presenting Cells.

IL-15 is one of the important biologics considered for vaccine adjuvant and treatment of cancer. However, a short half-life and poor bioavailability limit its therapeutic potential. Herein, we have structured IL-15 into a chimeric protein to improve its half-life enabling greater bioavailability for longer periods. We have covalently linked IL-15 with IgG2 base to make the IL-15 a stable chimeric protein, which also increased its serum half-life by 40 fold. The dimeric structure of this kind of IgG based biologics has greater stability, resistance to proteolytic cleavage, and less frequent dosing schedule with minimum dosage for achieving the desired response compared to that of their monomeric forms. The structured chimeric IL-15 naturally forms a dimer, and retains its affinity for binding to its receptor, IL-15Rß. Moreover, with the focused action of the structured chimeric IL-15, antigen-presenting cells (APC) would transpresent chimeric IL-15 along with antigen to the T cell, that will help the generation of quantitatively and qualitatively better antigen-specific memory T cells. In vitro and in vivo studies demonstrate the biological activity of chimeric IL-15 with respect to its ability to induce IL-15 signaling and modulating CD8+ T cell response in favor of memory generation. Thus, a longer half-life, dimeric nature, and anticipated focused transpresentation by APCs to the T cells will make chimeric IL-15 a super-agonist for memory CD8+ T cell responses.

HAART Induced Gynaecomastia.

Benign glandular enlargement of male breast is called gynaecomastia.Various drugs have been implicated as the cause. Most widely used HAART regimen TLE is enlisted in least common cause of gynaecomastia. A 42 yr old male diagnosed HIV seropositive since last 10 yrs was put on TLE regimen and he presented with gynaecomastia since 11 months. We hereby report this finding on HAART.

Influence of Length and Amino Acid Composition on Dimer Formation of Immunoglobulin based Chimera.

BACKGROUND: The dimeric immunoglobulin (Ig) chimeras used for drug targeting and delivery are preferred biologics over their monomeric forms. Designing these Ig chimeras involves critical selection of a suitable Ig base that ensures dimer formation. In the present study, we systematically analyzed several factors that influence the formation of dimeric chimera. We designed and predicted 608 cytokine-Ig chimeras where we tested the contributions of (1) different domains of Ig constant heavy chain, (2) length of partner proteins, (3) amino acid (AA) composition and (4) position of cysteine in the formation of homodimer. METHOD: The sequences of various Ig and cytokines were procured from Uniprot database, fused and submitted to COTH (CO-THreader) server for the prediction of dimer formation. Contributions of different domains of Ig constant heavy chain, length of chimeric proteins, AA composition and position of cysteine to the homodimer formation of 608 cytokine-Ig chimeras were tested. Various in silico approaches were adopted for validating the in silico findings. Experimentally we also validated our approach by expressing the chimeric design of shorter cytokine with Ig domain in CHO cells and analyzing the protein by SDS-PAGE. RESULTS: Our results advocate that while the CH1 region and the Hinge region of Ig heavy chain are critical, the length of partner proteins also crucially influences homodimer formation of the Ig-based chimera. We also report that the CH1 domain of Ig is not required for dimer formation of Ig based chimera in the presence of larger partner proteins. For shorter partner proteins fused to CH2-CH3, careful selection of partner sequence is critical, particularly the hydrophobic AA composition, cysteine content & their positions, disulphide bond formation property, and the linker sequences. We validated our in silico observation by various bioinformatics tools and checked the ability of chimeras to bind with the receptors of native protein by docking studies. As a proof of concept, we have expressed the chimeric proteins in CHO cells and found that our design favors the synthesis of dimeric proteins. CONCLUSION: Our structural prediction study suggests that extra amino acids in the range of 15-20 added to the CH2 domain of Ig is a critical requirement to make homodimer. This information from our study will have implication in designing efficacious homodimeric chimera.

Interleukin 15: A key cytokine for immunotherapy.

Interleukin (IL)-15, a member of the immunoregulatory cytokines family, is a pluripotent molecule with therapeutic potential. It is predominantly expressed by the myeloid cells, as well as other cell types. IL-15 serves multiple functions including dictating T cell response, regulating tissue repair and B cell homing, modulating inflammation, and activating NK cells. Among cytokines, IL-15 is unique because of its wide expression, tightly regulated secretion, trans-presentation, and therapeutic potential. IL-15 has been investigated for its therapeutic potential for the induction and maintenance of T cell responses. In addition, IL-15 can be targeted by antibody- or mutant IL-15 therapy to reduce inflammation. Its multifaceted biological applications are crucial in immunotherapy. In this article, we review the functions, expression, and regulation of IL-15 for designing an improved IL-15-based therapy targeting the IL-15 signaling pathway.

Route of administration of attenuated sporozoites is instrumental in rendering immunity against Plasmodia infection.

Whole sporozoite vaccine (WSV) approach has been shown to induce efficient CD8(+) T cell response, critical for developing of long-lasting sterile protection against Plasmodium. Although WSV was initiated over four decades ago, we still do not fully understand about the absolute requirements for the generation of liver-stage specific CD8(+) T memory cells. For more than a decade intravenous (IV) route of immunization has been shown to be protective in pre-clinical studies. However, the intradermal (ID) route is preferred over IV route by many researchers as it is perceived to mimic the natural route of parasite delivery through mosquito bite. Various clinical studies have shown that ID route provokes poor protective responses compared to those seen with IV route of administration. The present study highlights the importance of circumsporozoite (CS) protein in preventing sporozoite entry to the hepatocytes, which however, it is not necessarily sufficient to ensure sterile protection. Instead, this article favors the idea that liver-stage development is a prime requirement for generation of antigen specific CD8(+) T cells and suggests the conditions favored by IV inoculation of sporozoite.

Corrigendum: Liver-Stage Specific Response among Endemic Populations: Diet and Immunity.

[This corrects the article on p. 125 in vol. 6, PMID: 25852693.].

Liver-Stage Specific Response among Endemic Populations: Diet and Immunity.

Developing effective anti-malarial vaccine has been a challenge for long. Various factors including complex life cycle of parasite and lack of knowledge of stage specific critical antigens are some of the reasons. Moreover, inadequate understanding of the immune responses vis-à-vis sterile protection induced naturally by Plasmodia infection has further compounded the problem. It has been shown that people living in endemic areas take years to develop protective immunity to blood stage infection. But hardly anyone believes that immunity to liver-stage infection could be developed. Various experimental model studies using attenuated parasite suggest that liver-stage immunity might exist among endemic populations. This could be induced because of the attenuation of parasite in liver by various compounds present in the diet of endemic populations.