Human cytomegalovirus (HCMV) is ubiquitously prevalent. HCMV infection is typically asymptomatic and controlled by the immune system in healthy individuals, yet HCMV can be severely pathogenic for the fetus during pregnancy and in immunocompromised persons, such as transplant recipients or HIV infected patients. HCMV has co-evolved with the hosts, developed strategies to hide from immune effector cells and to successfully survive in the human organism. One strategy for evading or delaying the immune response is maintenance of the viral genome to establish the phase of latency. Furthermore, HCMV immune evasion involves the downregulation of human leukocyte antigens (HLA)-Ia molecules to hide infected cells from T-cell recognition. HCMV expresses several proteins that are described for downregulation of the HLA class I pathway via various mechanisms. Here, we review the wide range of immune evasion mechanisms of HCMV. Understanding the mechanisms of HCMV immune evasion will contribute to the development of new customized therapeutic strategies against the virus.

Defining permissive and non-permissive mismatches for transplantation is a demanding challenge. Single mismatches at amino acid (AA) position 156 of human leucocyte antigen (HLA) class I have been described to alter the peptide motif, repertoire, or mode of peptide loading through differential interaction with the peptide-loading complex. Hence, a single mismatch can tip the balance and trigger an immunological reaction. HLA-B*35 subtypes have been described to evade the loading complex, 156 mismatch distinguishing B*35:01 and B*35:08 changes the binding groove sufficiently to alter the sequence features of the selected peptide repertoire. To understand the functional influences of residue 156 in B*35 variants, we analyzed the peptide binding profiles of HLA-B*35:01156Leu, B*35:08156Arg and B*35:62156Trp. The glycoprotein tapasin represents a target for immune evasions and functions within the multimeric peptide-loading complex to stabilize empty class I molecules and promote acquisition of high-affinity peptides. All three B*35 subtypes showed a tapasin-independent mode of peptide acquisition. HLA-B*35-restricted peptides of low- and high-binding affinities were recovered in the presence and absence of tapasin and subsequently sequenced utilizing mass spectrometry. The peptides derived from B*35 variants differ substantially in their features dependent on their mode of recruitment; all peptides were preferentially anchored by Pro at p2 and Tyr, Phe, Leu, or Lys at pΩ. However, the Trp at residue 156 altered the p2 motif to an Ala and restricted the pΩ to a Trp. Our results highlight the importance of understanding the impact of key micropolymorphism and how a single AA mismatch orchestrates the neighboring AAs.Electronic supplementary materialThe online version of this article (doi:10.1007/s00251-015-0896-4) contains supplementary material, which is available to authorized users.

Objectives: The study was carried out to optimize the phenotypic method to characterize the sickle cell trait (SCT), sickle cell anaemia (SCA) and β-thalassemia (β-TT) suspected sample from tharu community of South Western province-5, Nepal. SCT and SCA were further evaluated by genotypic method employing amplification refractory mutation system (ARMS PCR). Moreover, Glucose 6 Phosphate Dehydrogenase (G6PD) was estimated in those hemoglobinopathy to observe its prevalence. The accurate and reliable method can play an important role in reduction of morbidity and mortality rate. Results: The 100 suspected cases were subjected to phenotypic method adopting cellulose acetate electrophoresis and genotypic metod using ARMS PCR which portraits (5%) SCA positive test showing HBS/HBS, (38%) SCT positive trait HBA/HBS and (36%) cases normal HBA/HBA. β-TT (21%) cases were confirmed by electropherogram. G6PD deficiency was observed in (40%) of SCA, (18.4%) of SCT, (4.8%) of β-TT and (2.8%) in normal cases. Increased G6PD were developed only in SCT (5.3 %) and β-TT (4.8%). The study highlighted sickle cell disorder (SCD) and β-TT as the most common hemoglobinopathy coexisting with G6PD deficiency. Though hemoglobinopathy sometime could be protective in malaria but G6PD deficiency can cause massive hemolysis which may exacerbate the condition.

ObjectivesThe study was carried out to optimize the phenotypic method to characterize the sickle cell trait (SCT), sickle cell anemia (SCA), and β-thalassemia (β-TT) suspected sample from tharu community of South Western province-5, Nepal. SCT and SCA were further evaluated by genotypic method employing amplification refractory mutation system (ARMS PCR). Moreover, Glucose 6 phosphate dehydrogenase (G6PD) was estimated in those hemoglobinopathy to observe its prevalence. The accurate and reliable method can play an important role in reduction of morbidity and mortality rate.ResultsThe 100 suspected cases were subjected to phenotypic method adopting cellulose acetate electrophoresis and genotypic method using ARMS PCR which portraits (5%) SCA positive test showing HBS/HBS, (38%) SCT positive trait HBA/HBS and (36%) cases normal HBA/HBA. β-TT (21%) cases were confirmed by electropherogram. G6PD deficiency was observed in (40%) of SCA, (18.4%) of SCT, (4.8%) of β-TT and (2.8%) in normal cases. Increased G6PD were developed only in SCT (5.3%) and β-TT (4.8%). The study highlighted sickle cell disorder (SCD) and β-TT as the most common hemoglobinopathy coexisting with G6PD deficiency. Though hemoglobinopathy sometime could be protective in malaria but G6PD deficiency can cause massive hemolysis which may exacerbate the condition.

Peptide selection in infected cells is not fully understood yet, but several indications point to the fact that there are differences to uninfected cells, especially in productive HCMV infection, since HCMV evolved various strategies to disable the hosts immune system, including presentation of peptide-HLA complexes to immune effector cells. Therefore, peptide predictions for specific HLA alleles are limited in these cases and the naturally presented peptide repertoire of HCMV-infected cells is of major interest to optimize adoptive T cell therapies. The allotypes HLA-B*35:01 and B*35:08 differ at a single amino acid at position 156 and have been described to differ in their peptide features and in their association with the peptide loading complex. Virus specific T cells recognizing the allelic pHLA-B*35 complexes could be detected, indicating a significant role of this HLA subtypes in viral immunity. However, naturally selected and presented viral peptides have not been described so far. In this study, we analyzed the peptide binding repertoire for HLA-B*35:01 and HLA-B*35:08 in HCMV-infected cells. The isolated peptides from both allelic subtypes were of extraordinary length, however differed in their features, origin, and sequence. For these HCMV-originated peptides, no overlap in the peptide repertoire could be observed between the two allelic subtypes. These findings reveal the discrepancies between predicted and naturally presented immunogenic epitopes and support the need of comprehensive peptide recruitment data for personalized and effective cellular therapies.