Frequency of FCGR3B alleles in Thai blood donors

Are Fc Gamma Receptor Polymorphisms Important in HIV-1 Infection Outcomes and Latent Reservoir Size?

Fc gamma receptors (FcγR) are cell surface glycoproteins which trigger specific effector-cell responses when cross-linked with the Fc portions of immunoglobulin (IgG) antibodies. During HIV-1 infection, the course of disease progression, ART response, and viral reservoir size vary in different individuals. Several factors may account for these differences; however, Fc gamma receptor gene polymorphisms, which influence receptor binding to IgG antibodies, are likely to play a key role. FcγRIIa (CD32) was recently reported as a potential marker for latent HIV reservoir, however, this assertion is still inconclusive. Whether FcγR polymorphisms influence the size of the viral reservoir, remains an important question in HIV cure studies. In addition, potential cure or viral suppression methods such as broadly neutralizing antibody (bNAbs) may depend on FcγRs to control the virus. Here, we discuss the current evidence on the potential role played by FcγR polymorphisms in HIV-1 infection, treatment and vaccine trial outcomes. Importantly, we highlight contrasting findings that may be due to multiple factors and the relatively limited data from African populations. We recommend further studies especially in sub-Saharan Africa to confirm the role of FcγRIIa in the establishment of latent reservoir and to determine their influence in therapies involving bNAbs.

HNA-1, -3, -4, and -5 genotyping using multiplex PCR among southern Thais: Developing continual HNA-1 null detection

BACKGROUND

Antibodies against human neutrophil antigens (HNAs) are involved in various clinical conditions including transfusion-related acute lung injury and auto/alloimmune neutropenia. We aimed to determine HNA-1, -3, -4, and -5 frequencies among southern Thais using multiplex PCR and to develop HNA-1 null detection.

METHODS

Samples obtained from 427 southern Thai blood donors were genotyped HNA-1, -3, -4, and -5 using multiplex PCR and compared their allele frequencies with those previously reported in Thai populations. HNA-1 null samples were tested by newly developed PCR-SSP and PCR-RFLP and confirmed by DNA sequencing.

RESULTS

The frequencies of FCGR3B*01, FCGR3B*02, FCGR3B*03, SLC44A2*01, SLC44A2*02, ITGAL*01, and ITGAL*02 among southern Thais differed from other Thai populations, except ITGAM*01 and ITGAM*02 frequencies. Two samples without specific fragments of FCGR3B*01, FCGR3B*02, and FCGR3B*03 tested by multiplex PCR were confirmed by PCR-RFLP to identify FCGR3B deficiency (HNA-1 null). Moreover, to reduce test steps, the newly developed PCR-SSP for FCGR3B deficiency was validated and tested in all samples and the results were in agreement with DNA sequencing.

CONCLUSIONS

This was the first study to report HNA-1, -3, -4, and -5 frequencies among southern Thais. The indeterminate results of multiplex PCR for HNA-1 genotyping led to establish HNA-1 null detection using PCR-SSP, which is simple, convenient and cost-effective and can be used to identify FCGR3B deficiency.

A study of human neutrophil antigen genotype frequencies in Hong Kong

BACKGROUND

Alloantibodies against human neutrophil antigens (HNA) are associated with a variety of clinical conditions. Over the past decade, the allelic and genotypic frequencies of the five HNA systems have been evaluated. Although the HNA system is less polymorphic than human leukocyte antigens (HLA), significant differences in the genotypic and allele frequencies still exist in different populations, even those living in close proximity.

OBJECTIVES

To delineate HNA genotypic and allele frequencies to provide vital information on estimating the risk of HNA-associated diseases for our local population.

METHODS

Using a validated, in-house-developed assay, genotyping for HNA-1, HNA-3, HLA-4 and HNA-5 was performed on 300 samples from Chinese blood donors from Hong Kong. In addition, the frequency of the HNA-2 c.843A > T allele was also determined.

RESULTS

The allele frequencies of HNA-1a, -1b and -1c alleles were 67·8, 31·5 and 0%, respectively, whereas the frequencies of HNA-3a and HNA-3b were 71·0 and 29·0%, respectively. The frequencies of HNA-4a and -4b alleles were 99·5 and 0·5%, respectively, and for HNA-5a and -5b, alleles were 85·2 and 14·8%, respectively. Homozygotes for the HNA-2 c.843 TT variant were absent in our population, whereas only <4% of the population were c.843AT heterozygote carriers.

CONCLUSIONS

This is the first study to define HNA genotype and allele frequencies using a validated modified in-house PCR-SSP method in the Hong Kong Chinese blood donor population. Our approach provides a cost-effective assay for conducting routine HNA typing and facilitates the incorporation of these assays into routine clinical service. Our results are comparable with those reported in the Guangzhou Chinese population, but the allele frequencies in our Hong Kong Chinese population are significantly different from the reported European frequencies, confirming that a geographical difference exists for HNA allele frequencies.

Nonclassical FCGR2C haplotype is associated with protection from red blood cell alloimmunization in sickle cell disease

Red blood cell (RBC) transfusions are of vital importance in patients with sickle cell disease (SCD). However, a major complication of transfusion therapy is alloimmunization. The low-affinity Fcγ receptors, expressed on immune cells, are important regulators of antibody responses. Genetic variation in FCGR genes has been associated with various auto- and alloimmune diseases. The aim of this study was to evaluate the association between genetic variation of FCGR and RBC alloimmunization in SCD. In this case-control study, DNA samples from 2 cohorts of transfused SCD patients were combined (France and The Netherlands). Cases had a positive history of alloimmunization, having received ≥1 RBC unit. Controls had a negative history of alloimmunization, having received ≥20 RBC units. Single nucleotide polymorphisms and copy number variation of the FCGR2/3 gene cluster were studied in a FCGR-specific multiplex ligation-dependent probe amplification assay. Frequencies were compared using logistic regression. Two hundred seventy-two patients were included (130 controls, 142 cases). The nonclassical open reading frame in the FCGR2C gene (FCGR2C.nc-ORF) was strongly associated with a decreased alloimmunization risk (odds ratio [OR] 0.26, 95% confidence [CI] 0.11-0.64). This association persisted when only including controls with exposure to ≥100 units (OR 0.30, CI 0.11-0.85) and appeared even stronger when excluding cases with Rh or K antibodies only (OR 0.19, CI 0.06-0.59). In conclusion, SCD patients with the FCGR2Cnc-ORF polymorphism have over a 3-fold lower risk for RBC alloimmunization in comparison with patients without this mutation. This protective effect was strongest for exposure to antigens other than the immunogenic Rh or K antigens.

Assessment of HNA alloimmunisation risk in Northeastern Thais, Burmese and Karen

OBJECTIVES

This study aimed to determine human neutrophil antigen (HNA) frequency, estimate possible HNA incompatibilities and predict the risk of HNA alloimmunisation in the Northeastern Thai, Burmese and Karen populations.

BACKGROUND

Alloantibodies against HNA are implicated in a number of clinical conditions, including immune-mediated neutropenia and transfusion reactions.

METHODS

A total of 400 unrelated healthy Thais, 261 Burmese and 249 Karen was included in this study. DNA samples were typed for HNA-1, -3, -4 and -5 systems using polymerase chain reactions with sequence-specific primers (PCR-SSP).

RESULTS

In this cohort, HNA-1a was more prevalent than HNA-1b. Accordingly, the possible risk of HNA-1a alloimmunisation against HNA-1a is lower than HNA-1b (0·0802-0·1351 vs 0·2293-0·2497). This is in contrast to the situation reported in Caucasian and African populations. The predicted risk of HNA-3 incompatibility in Thais, Burmese and Karen were 28·09%, 30·66% and 22·77%, respectively. The possible risks of HNA-3a alloimmunisation were 0·0493 in Thais, 0·0608 in Burmese and 0·0196 in Karen, respectively. No individuals were found to be homozygous for HNA-4bb. The probability of developing alloantibodies against HNA-4a was low in these populations and every population in Asia. In contrast, the overall frequency of HNA-5bb homozygous individuals was high in this study, peaking at 0·192.

CONCLUSIONS

This is the first study that reported the allele frequencies of HNA-1, -3, -4, and -5 in a large sample of healthy unrelated individuals from ethnic Thais, Burmese and Karen. Our results indicated the high possible risk of HNA-1, -3 and -5 alloimmunisation in these populations.

Variability at the FCGR locus: characterization in Black South Africans and evidence for ethnic variation in and out of Africa

This study set out to comprehensively investigate all known functional FcγR variants in South African Black and Caucasian individuals. Population diversity was further assessed using data from the 1000 Genomes Project. In our cohort, Black South Africans neither possessed the haplotypes previously associated with increased surface densities of FcγRIIb and FcγRIIIa nor the FCGR2C haplotype recently associated with increased vaccine efficacy in the RV144 HIV-1 vaccine trial (despite 48.7% bearing the c.134-96T tag allele). Moreover, Africans (South Africans, Luhya Kenyans and Yoruba Nigerians) lack the FCGR2C c.798+1G splice-site allele required for the expression of functional FcγRIIc. Although the presence or absence of surface FcγRIIc did not affect natural killer cell-mediated antibody-dependent cellular cytotoxicity capability, this may be significant for other FcγRIIc-mediated functions. Overall, allele distribution and linkage disequilibrium in Africans and Caucasians differed in a manner that would suggest a differentially maintained balance of FcγR-mediated cell activation in these populations. Finally, significant variation observed among different African populations precludes the use of any one African population as a proxy for FcγR diversity in Africans. In conclusion, the findings of this study highlight further ethnic variation at the FCGR gene locus, in particular for FCGR2C, a gene with increasingly recognized clinical significance.

FCGR3B gene frequencies among ethnic Thai blood donors from a regional hospital in Eastern Thailand

The FCGR3B gene encodes three human neutrophil antigens which consist of HNA-1a, HNA-1b, and HNA-1c. These antigens are encoded by three alleles in the FCGR3B locus: FCGR3B*01, FCGR3B*02, and FCGR3B*03 alleles, respectively. The frequencies of FCGR3B alleles have been reported in different ethnic populations. This study compared the FCGR3B gene frequencies among 230 unrelated healthy Eastern Thai blood donors in Rayong hospital with the previously published studies. The polymerase chain reaction-sequence-specific primers method was performed to determine FCGR3B genotypes. The results showed that the allele frequencies of FCGR3B*01, FCGR3B*02, and FCGR3B*03 were 0.722, 0.274, and 0.009, respectively. The FCGR3B*01 and FCGR3B*02 frequencies found in the Eastern Thais were similar to the previous reports investigating in Northern Thais, Chinese Han, Taiwanese, and Japanese populations. Interestingly, our data showed statistically significant difference (P < 0.05) to Central Thais, Korean, Indian, Turkish, Australian, Tunisian, American, German, and Italian populations. In addition, one FCGR3Bnull , which represents a gene deletion, was also found in this study. This information is important not only for the assessment of neutrophil antibody-mediated clinical conditions and for disease association studies but also for anthropological studies.