The decoy Fcγ receptor encoded by the cytomegalovirus UL119-UL118 gene has differential affinity to IgG proteins expressing different GM allotypes

Polyfunctional antibodies: a path towards precision vaccines for vulnerable populations

Vaccine efficacy determined within the controlled environment of a clinical trial is usually substantially greater than real-world vaccine effectiveness. Typically, this results from reduced protection of immunologically vulnerable populations, such as children, elderly individuals and people with chronic comorbidities. Consequently, these high-risk groups are frequently recommended tailored immunisation schedules to boost responses. In addition, diverse groups of healthy adults may also be variably protected by the same vaccine regimen. Current population-based vaccination strategies that consider basic clinical parameters offer a glimpse into what may be achievable if more nuanced aspects of the immune response are considered in vaccine design. To date, vaccine development has been largely empirical. However, next-generation approaches require more rational strategies. We foresee a generation of precision vaccines that consider the mechanistic basis of vaccine response variations associated with both immunogenetic and baseline health differences. Recent efforts have highlighted the importance of balanced and diverse extra-neutralising antibody functions for vaccine-induced protection. However, in immunologically vulnerable populations, significant modulation of polyfunctional antibody responses that mediate both neutralisation and effector functions has been observed. Here, we review the current understanding of key genetic and inflammatory modulators of antibody polyfunctionality that affect vaccination outcomes and consider how this knowledge may be harnessed to tailor vaccine design for improved public health.

Functional consequences of allotypic polymorphisms in human immunoglobulin G subclasses

Heritable polymorphisms within the human IgG locus, collectively termed allotypes, have often been linked by statistical associations, but rarely mechanistically, to a wide range of disease states. One potential explanation for these associations is that IgG allotype alters host cell receptors' affinity for IgG, dampening or enhancing an immune response depending on the nature of the change and the receptors. In this work, a panel of allotypic antibody variants were evaluated using multiplexed, label-free biophysical methods and cell-based functional assays to determine what effect, if any, human IgG polymorphisms have on antibody function. While we observed several differences in FcγR affinity among allotypes, there was little evidence of dramatically altered FcγR-based effector function or antigen recognition activity associated with this aspect of genetic variability.

Deciphering the Potential Coding of Human Cytomegalovirus: New Predicted Transmembrane Proteome

CMV is a major cause of morbidity and mortality in immunocompromised individuals that will benefit from the availability of a vaccine. Despite the efforts made during the last decade, no CMV vaccine is available. An ideal CMV vaccine should elicit a broad immune response against multiple viral antigens including proteins involved in virus-cell interaction and entry. However, the therapeutic use of neutralizing antibodies targeting glycoproteins involved in viral entry achieved only partial protection against infection. In this scenario, a better understanding of the CMV proteome potentially involved in viral entry may provide novel candidates to include in new potential vaccine design. In this study, we aimed to explore the CMV genome to identify proteins with putative transmembrane domains to identify new potential viral envelope proteins. We have performed in silico analysis using the genome sequences of nine different CMV strains to predict the transmembrane domains of the encoded proteins. We have identified 77 proteins with transmembrane domains, 39 of which were present in all the strains and were highly conserved. Among the core proteins, 17 of them such as UL10, UL139 or US33A have no ascribed function and may be good candidates for further mechanistic studies.

Population-specific diversity of the immunoglobulin constant heavy G chain (IGHG) genes

Human immunoglobulin G (IgG) molecules, IgG1, IgG2 and IgG3, exhibit substantial inter-individual variation in their constant heavy chain regions, as discovered by serological methods. This polymorphism is encoded by the IGHG1, IGHG2, and IGHG3 genes and may influence antibody function. We sequenced the coding fragments of these genes in 95 European Americans, 94 African Americans, and 94 Black South Africans. Striking differences were observed between the population groups, including extremely low amino acid sequence variation in IGHG1 among South Africans, and higher IGHG2 and IGHG3 diversity in individuals of African descent compared to individuals of European descent. Molecular definition of the loci illustrates a greater level of allelic polymorphism than previously described, including the presence of common IGHG2 and IGHG3 variants that were indistinguishable serologically. Comparison of our data with the 1000 Genome Project sequences indicates overall agreement between the datasets, although some inaccuracies in the 1000 Genomes Project are likely. These data represent the most comprehensive analysis of IGHG polymorphisms across major populations, which can now be applied to deciphering their functional impact.

Role of Immunogenetics in the Outcome of HCMV Infection: Implications for Ageing

The outcome of host-virus interactions is determined by a number of factors, some related to the virus, others to the host, such as environmental factors and genetic factors. Therefore, different individuals vary in their relative susceptibility to infections. Human cytomegalovirus (HCMV) is an important pathogen from a clinical point of view, as it causes significant morbidity and mortality in immunosuppressed or immunosenescent individuals, such as the transplanted patients and the elderly, respectively. It is, therefore, important to understand the mechanisms of virus infection control. In this review, we discuss recent advances in the immunobiology of HCMV-host interactions, with particular emphasis on the immunogenetic aspects (human leukocyte antigens, HLA; killer cell immunoglobulin-like receptors, KIRs; immunoglobulin genetic markers, GM allotypes) to elucidate the mechanisms underlying the complex host-virus interaction that determine various outcomes of HCMV infection. The results, which show the role of humoral and cellular immunity in the control of infection by HCMV, would be valuable in directing efforts to reduce HCMV spurred health complications in the transplanted patients and in the elderly, including immunosenescence. In addition, concerning GM allotypes, it is intriguing that, in a Southern Italian population, alleles associated with the risk of developing HCMV symptomatic infection are negatively associated with longevity.

G1m1 predominance of intrathecal virus-specific antibodies in multiple sclerosis

We have previously shown that plasmablasts of the G1m1 allotype of IgG1 are selectively enriched in the cerebrospinal fluid of G1m1/G1m3 heterozygous patients with multiple sclerosis, whereas both allotypes are equally used in neuroborreliosis. Here, we demonstrate a strong preference for the G1m1 allotype in the intrathecal humoral immune responses against measles, rubella, and varicella zoster virus in G1m1/G1m3 heterozygous multiple sclerosis patients. Conversely, intrathecally synthesized varicella zoster virus‐specific IgG1 in varicella zoster virus meningoencephalitis comprised both allotypes. This implies that G1m1 B cells are selected to the central nervous system of multiple sclerosis patients regardless of specificity and suggests that an antigen‐independent mechanism could drive the intrathecal humoral immune response.

IGHG, IGKC, and FCGR genes and endogenous antibody responses to GARP in patients with breast cancer and matched controls

Glycoprotein-A repetitions predominant (GARP) is a transmembrane protein that is highly expressed in breast cancer. Its overexpression correlates with worse survival, and antibodies to GARP appear to play a protective role in a mouse model. No large-scale studies of immunity to GARP in humans have yet been undertaken. In this investigation, using a large multiethnic cohort (1738 subjects), we aimed to determine whether the magnitude of anti-GARP antibody responsiveness was significantly different in patients with breast cancer from that in matched healthy controls. We also investigated whether the allelic variation at the immunoglobulin GM (γ marker), KM (κ marker), and Fcγ receptor (FcγR) loci contributed to the interindividual variability in anti-GARP IgG antibody levels. A combined analysis of all subjects showed that levels of anti-GARP antibodies were significantly higher in patients with breast cancer than in healthy controls (mean ± SD: 7.4 ± 3.5 vs. 6.9 ± 3.5 absorbance units per mL (AU/μL), p < 0.0001). In the two populations with the largest sample size, the probability of breast cancer generally increases as anti-GARP antibody levels increase. Several significant individual and epistatic effects of GM, KM, and FcγR genotypes on anti-GARP antibody responsiveness were noted in both patients and controls. These results, if confirmed by independent investigations, will aid in devising personalized GARP-based immunotherapeutic strategies against breast cancer and other GARP-overexpressing malignancies.

Association between γ marker, human leucocyte antigens and killer immunoglobulin-like receptors and the natural course of human cytomegalovirus infection: a pilot study performed in a Sicilian population

Natural killer (NK) cells provide a major defence against human cytomegalovirus (HCMV) infection through the interaction of their surface receptors, including the activating and inhibitory killer immunoglobulin-like receptors (KIRs), and human leucocyte antigen (HLA) class I molecules. Also γ marker (GM) allotypes, able to influence the NK antibody-dependent cell-mediated cytotoxicity, appear to be involved in the immunological control of virus infections, including HCMV. In some cases, their contribution requires epistatic interaction with other genes of the immune system, such as HLA. In the present report, with the aim of gaining insight into the immune mechanisms controlling HCMV, we have studied the possible associations among humoral and NK responses, and HCMV infections. In a previous study we assessed whether the KIR and HLA repertoire might influence the risk of developing symptomatic (n = 60) or asymptomatic (n = 60) disease after primary HCMV infection in the immunocompetent host. In the present study, the immunocompetent patients with primary symptomatic HCMV infection were genotyped for GM3/17 and GM23 allotypes, along with the 60 participants with a previous asymptomatic infection as controls. Notwithstanding the presence of missing data record, advanced missing data recovery techniques were able to show that individuals carrying the GM23 allotypes, both homozygous and heterozygous, GM17/17, HLA-C2 and Bw4^T KIR-ligand groups are associated with the risk of developing symptomatic infection. Our findings on the role of both cellular and humoral immunity in the control of HCMV infection should be of value in guiding efforts to reduce HCMV-associated health complications in the elderly, including immunosenescence, and in transplantation.

Immunoglobulin genotypes and cognitive functions in schizophrenia

Exposure to neurotropic viruses, such as herpes simplex virus type 1 and human cytomegalovirus, has been reported to be associated with cognitive impairment in schizophrenia. These viruses have evolved highly sophisticated strategies for decreasing the efficacy of the host immune response and interfering with viral clearance. Particular immunoglobulin GM (γ marker) genotypes modulate these viral immunoevasion strategies, influence antibody responsiveness to viral proteins, and are also associated with susceptibility to schizophrenia, providing an excellent rationale for determining their possible involvement in the cognitive functions in this highly heritable neurodevelopmental disorder. In this investigation, we assessed the cognitive functions (verbal memory, working memory, motor speed, verbal fluency, attention and processing speed, and executive function) in 145 patients with schizophrenia and characterized their DNA for several GM and KM (κ marker) alleles. Particular KM and GM genotypes were significantly associated with verbal memory and attention and processing speed scores, respectively (P = 0.01 and 0.001). Epistatic effects of GM and KM genotypes on attention and processing speed, verbal fluency, and motor speed were also noted (P = 0.031, 0.047, 0.003). These results, for the first time, show that hitherto understudied immunoglobulin GM and KM genotypes-individually and epistatically-contribute to the magnitude of interindividual variability in the cognitive functions in patients with schizophrenia. Additional studies involving these highly polymorphic genes of the immune system are needed.

Genetic markers of immunoglobulin G and immunity to cytomegalovirus in patients with breast cancer

Human cytomegalovirus (CMV), a ubiquitous herpesvirus, has been implicated in the etiology of breast cancer. It is clear that not all people exposed to CMV are equally likely to develop this malignancy, implying the presence of host genetic factors that might modulate the cancer-spurring properties of the virus. CMV has evolved sophisticated strategies for evading host immunosurveillance. One strategy involves encoding decoy Fcγ receptors (FcγR) that thwart the Fcγ-mediated effector functions, such as antibody-dependent cellular cytotoxicity. In this investigation, using an enzyme-linked immunosorbent assay (ELISA), we aimed to determine whether the decoy FcγR encoded by the CMV gene RL13 binds differentially to anti-CMV antibodies expressing different immunoglobulin GM (γ marker) allotypes, genetic markers of immunoglobulin G (IgG). Results of our ELISA binding studies showed that the absorbance values for the binding of the viral FcγR to the GM 17-expressing IgG antibodies were significantly higher than for the GM 3-expressing antibodies (0.60 vs. 0.36; p=0.0019). These findings provide mechanistic insights into the modulating role played by the genetic variants of IgG in the generation of immunity to CMV in patients with breast cancer.

Immunoglobulin G genotypes and the risk of schizophrenia

Genes of the immune system are relevant to the etiology of schizophrenia. However, to our knowledge, no large-scale studies, using molecular methods, have been undertaken to investigate the role of highly polymorphic immunoglobulin GM (γ marker) genes in this disorder. In this investigation, we aimed to determine whether particular GM genotypes were associated with susceptibility to schizophrenia. Using a matched case-control study design, we analyzed DNA samples from 798 subjects-398 patients with schizophrenia and 400 controls-obtained from the U.S. National Institute of Mental Health Repository. GM alleles were determined by the TaqMan(®) genotyping assay. The GM 3/3; 23-/23- genotype was highly significantly associated with susceptibility to schizophrenia (p = 0.0002). Subjects with this genotype were over three times (OR 3.4; 95 % CI 1.7-6.7) as likely to develop schizophrenia as those without this genotype. Our results show that immunoglobulin GM genes are risk factors for the development of schizophrenia. Since GM alleles have been implicated in gluten sensitivity and in immunity to neurotropic viruses associated with cognitive impairment, the results presented here may help unify these two disparate areas of pathology affected in this disorder.

Association of Human Immunoglobulin G1 Heavy Chain Variants With Neutralization Capacity and Antibody-Dependent Cellular Cytotoxicity Against Human Cytomegalovirus

Human cytomegalovirus (HCMV) infection is limited by HCMV-specific antibody functions. Here the association between the genetic marker (GM) 3/17 variants in the immunoglobulin G1 (IgG1) heavy chain constant region, virus neutralization, and natural killer (NK)-cell activation was investigated. In 100 HCMV-seropositive individuals, the GM3/17 polymorphism, serum 50% HCMV antibody neutralization titer (NT50), and in vitro HCMV-specific antibody NK-cell activation were assessed. The HCMV NT50 was higher in heterozygous GM3/17 persons than in GM3/3 persons (P = .0276). Furthermore, individuals expressing GM3/17 exhibited significantly higher NK-cell activation than persons carrying GM3/3 (P < .0001) or GM17/17 (P = .0095). Thus, persons expressing GM3/17 have potentially a selective advantage in HCMV defense.