Immunoglobulin GM and KM genotypes in hepatitis C virus infection

Immunoglobulin genes and severity of COVID-19

There is tremendous interindividual and interracial variability in the outcome of SARS-CoV-2 infection, suggesting the involvement of host genetic factors. Here, we investigated whether IgG allotypes GM (γ marker) 3 and GM 17, genetic markers of IgG1, contributed to the severity of COVID-19. IgG1 plays a pivotal role in response against SARS-CoV-2 infection. We also investigated whether these GM alleles synergistically/epistatically with IGHG3 and FCGR2A alleles-which have been previously implicated in COVID-19-modulated the extent of COVID-19 severity. The study population consisted of 316 COVID-19 patients who needed treatment in the intensive care unit of Hospital Universitario Central de Asturias. All individuals were genotyped for GM 3/17, IGHG3 hinge length, and FCGR2A rs1801274 A/G polymorphisms. Among the 316 critical patients, there were 86 deaths. The risk of death among critical patients was significantly higher in subjects with GM 17 (IgG1) and short hinge length (IgG3). GM 17-carriers were at almost three-fold higher risk of death than non-carriers (p < 0.001; OR = 2.86, CI 1.58-5.16). Subjects with short hinge length of IgG3 had a two-fold higher risk of death than those with medium hinge length (p = 0.01; OR = 2.16, CI 1.19-3.90). GM 3/3 and IGHG3 (MM) genotypes were less frequent among death vs. survivors (9% vs 36%, p < 0.001) and associated with protective effect (OR = 0.18, 95% CI = 0.08-0.39). This is the first report implicating IgG1 allotypes in COVID-19-spurred death. It needs to be replicated in an independent study population.

Immunoglobulin GM Genes, Cytomegalovirus Immunoevasion, and the Risk of Glioma, Neuroblastoma, and Breast Cancer

Human cytomegalovirus (HCMV), a common herpes virus, has been reported to be a risk factor for many diseases, including malignant diseases such as glioma, neuroblastoma, and breast cancer. Some of the HCMV-associated diseases (e.g., glioma) are rare. The question arises: how could a common virus be associated with uncommon diseases? Interactions between a major gene complex of the human immune system and a viral immunoevasion strategy – a probable mechanism of their co-evolutionary adaptation – may shed light on this paradox. To ensure its survival, HCMV has evolved sophisticated immunoevasion strategies. One strategy involves encoding decoy Fcγ receptors (FcγR), which may enable the virus to evade host immunosurveillance by avoiding the Fcγ-mediated effector consequences of anti-HCMV IgG antibody binding. Immunoglobulin G1 proteins expressing GM (γ marker) alleles 3 and 17 have differential affinity to the HCMV TRL11/IRL11-encoded FcγR, and thus act as effect modifiers of HCMV-associated malignancies. The high affinity GM 3 allele has been shown to be a risk factor for neuroblastoma, glioma, and breast cancer. Additional studies involving other viral FcγRs as well as GM alleles expressed on other IgG subclasses are warranted.

Genetic variation at immunoglobulin kappa locus is associated with hepatitis C-treatment-induced viral clearance in African Americans

Host genetic factors, especially genes of the immune system, are thought to contribute to the racial differences in response rates to therapy for hepatitis C virus (HCV) infection. The aim of the present investigation was to determine whether immunoglobulin gamma heavy chain marker (GM) and kappa light chain marker (KM) -were associated with sustained viral response (SVR) in patients treated with peginterferon-α-2a and ribavirin. DNA samples from 319 subjects with genotype-1 HCV infections were allotyped for alleles at four GM loci: GM3/GM17, GM23+/GM23-, GM5/GM21, GM6+/GM6- and the KM locus: KM1/KM3, using molecular methods. Noncarriage of KM1 allele, i.e., KM3 homozygosity, was associated with higher SVR in African Americans (odds ratio = 2.50, 95% confidence interval = 1.12-5.60). Consistent with this finding, the HCV RNA level in KM1 noncarriers was significantly (p = 0.013) lower than in carriers of this allele. Thus, the KM3 allele may be a marker for higher SVR in African Americans.

Immunoglobulin allotypes influence IgG antibody responses to hepatitis C virus envelope proteins E1 and E2

Immunoglobulin (Ig) GM and KM allotypes-genetic markers of gamma and kappa chains, respectively-are associated with the outcome of hepatitis C virus (HCV) infection, but the underlying mechanisms are not well understood. We hypothesized that GM and KM allotypes could contribute to the outcome of HCV infection by influencing the levels of IgG antibodies to the HCV glycoproteins E1E2. We serologically allotyped 100 African American individuals with persistent HCV infection for GM and KM markers and measured anti-E1E2 antibodies. Subjects with the GM 1,17 5,13 phenotype had significantly higher levels of anti-E1E2 antibodies than subjects who lacked this phenotype (p = 0.008). Likewise, subjects with the KM 1-carrying phenotypes had higher levels of anti-E1E2 antibodies than subjects who lacked these phenotypes (p = 0.041). Median titers were fourfold higher in persons expressing both GM 1,17 5,13 and KM 1-carrying phenotypes compared with those who lacked these phenotypes (p = 0.011). Interactive effects of these GM-KM phenotypes were previously found to be highly significantly associated with spontaneous HCV clearance. Results presented here show that Ig allotypes contribute to the interindividual differences in humoral immunity to the HCV epitopes, a finding that may provide a mechanistic explanation for their involvement in the outcome of HCV infection.

Interactive effects of immunoglobulin gamma and human leucocyte antigen genotypes on clearance and persistence of infection with hepatitis C virus

Particular alleles of human leucocyte antigen (HLA) and immunoglobulin gamma (GM) and immunoglobulin kappa (KM) allotypes (polymorphic determinants of IgG heavy chains and kappa-type light chains, respectively) are associated with the outcome of several infections. To examine their role in the outcome of hepatitis C virus (HCV) infection, we genotyped 50 individuals with resolved and 117 with persistent HCV infection. None of the GM, KM or HLA-C genotypes by themselves were associated with the resolution or persistence of HCV infection. However, particular combinations of HLA and GM genotypes were associated significantly with the outcome of HCV infection. Subjects with the HLA C1C1 genotype, in the absence of GM ff, were more than seven times [odds ratio (OR) 7.15] as likely to have persistent infection as the subjects who lacked both these genotypes. The presence of GM ff, in the absence of HLA C1C2, was associated with the resolution of infection (OR 0.27). The absence of GM fz, in the presence of HLA C2C2, was also associated with the resolution of infection (OR 0.27). Compared to the subjects who lacked both these genotypes, subjects with GM fz, in the absence of HLA C1C2, were almost four times as likely to have persistent infection (OR 3.91); similarly, subjects with HLA C1C2, in the absence of GM fz, were almost three times as likely to have persistent infection (OR 2.80). These results show, for the first time, interactive effects of GM and HLA genotypes in the outcome of HCV infection.

Interaction of KIR Genes and G1M Immunoglobulin Allotypes Confer Susceptibility to Type 2 Diabetes in Puerto Rican Americans

The susceptibility to type 2 diabetes (T2D) involves genetic factors. We studied the distribution of KIR and MHC class I ligands phenotype and genotype frequencies, as well as immunoglobulin KM and GM allotype frequencies in a group of patients (N = 95) with T2D and ethnically matched healthy controls (N = 74) with Puerto Rican ethnic background. We found a slight increase of the 2DL3/2DL3 homozygous genotype in T2D. Moreover, the association between 2DL3/2DL3 genotype was significant in the presence of 2DS4 (pC = 0.01). Also, we observed an epistatic effect of the interaction of 2DL3/2DL3, 2DS4 with allele z of G1M in T2D (pC = 0.004, OR = 3.60, 95% CI, 1.62-8.10). This genetic interaction between KIR and G1M allotypes, associated with T2D, was also significant by multiple logistic regression analysis (p < 0.0001, OR = 4.90, 95% CI, 2.12-11.3). We did not detect population stratification using unlinked short tandem repeat (STR) markers, demonstrating that the patients and controls were ethnically matched. Hence, we have demonstrated in this study an epistatic interaction between KIR genes and the G1M allotype that influences the susceptibility to T2D in Puerto Rican Americans. Our findings are important for understanding the autoimmune or innate immune inflammatory-mediated mechanisms involved in the pathogenesis of T2D.