A method for HLA-DQA typing by the PCR-SSP technique

Age-associated decrease in de novo donor-specific antibodies in renal transplant recipients reflects changing humoral immunity

Background

Older age at organ transplantation is associated with increased risk of infection and malignancy but reduced risk of cellular rejection. De novo donor-specific anti-HLA antibodies (dnDSA), are key biomarkers associated with reduced long-term allograft survival, yet there is a lack of data focusing on age-associated changes.

Methods

Development of dnDSA was restrospectively analyzed in all subjects who received a kidney transplant at the University Hospital Zurich between 01/2006 and 02/2015. Follow up continued until 03/2016. The incidence of dnDSA in different age categories was compared with special focus on the extremes of age: children < 10 years (n = 19) and adults ≥60 years of age (n = 110).

Results

Incidence of dnDSA gradually decreased with age, with older recipients having a significantly lower risk (HR 0.21, p = 0.0224) compared to pediatric recipients. Cumulative incidence of dnDSA at 2, 5 and 10 years was 6.2, 9.1 and 36% in the older recipients versus 5.3, 29.5 and 47.1% in pediatric recipients. Median time to development of dnDSA was similar (older 720 days, min 356, max 3646 days; children 1086 days, min 42, max 2474 days). Annual incidence was highest within the first two years after transplantation in the older recipients and peaked in years two to four in pediatric recipients. DnDSA were predominantly class II. More dnDSA were observed with cyclosporine as compared to tacrolimus.

Conclusion

Older kidney transplant recipients have a lower risk of developing dnDSA than pediatric recipients, pointing towards reduced humoral immune reactivity with increasing age. This observation raises the question of adjustment in immunosuppression.

Characterization of a new HLA-B allele, HLA-B*5312, and re-evaluation of the published sequences of the untranslated regions of HLA-B*35 and HLA-B*53

We report a novel human leukocyte antigen (HLA)-B allele, HLA-B*5312. Compared with HLA-B*530101, there is one silent substitution at nucleotide 438 and two non-synonymous substitutions at nucleotides 431 and 440, causing a change of the amino acid sequence (Asn-->Ser at codon 77 and Ile-->Thr at codon 80, respectively) within the Bw4 epitope. In contrast to the published sequences (IMGT/HLA Database, version 2.16.0, January 2007), we found that HLA-B*530101 had a C instead of a T at nucleotide -221, whereas HLA-B*350101 had a C instead of an A at nucleotide 2992. According to our sequencing results, HLA-B*5312 resembles HLA-B*350101 regarding its sequence of the untranslated regions. HLA-B*5312 may have been the result of a double crossing over event during which HLA-B*350101 adopted a Bw4 motif.

No Association of Factor V Leiden, Prothrombin G20210A, and MTHFR C677T Gene Polymorphisms With Kidney Allograft Survival: A Multicenter Study

BACKGROUND

It has been proposed that inherited risk factors of venous thromboembolism, such as factor V G1691A (FV-Leiden), prothrombin G20210A, and methylenetetrahydrofolate reductase (MTHFR) C677T, might be associated with poorer survival rates of transplanted kidneys. On the basis of this hypothesis, we performed a multicenter study, involving recipients of primary and repeat kidney transplants, to investigate the potential effect of these three single nucleotide polymorphisms (SNP) on graft survival.

METHODS

The study consisted of 676 first and 651 retransplant patients. Using the polymerase chain reaction-sequence specific primers method, we typed all patients for the three SNP and analyzed graft survival.

RESULTS

We could not find a statistically significant association between graft survival and factor V Leiden or MTHFR C677T genotypes. A better 3-yr graft survival was found for first transplant recipients with the genotype prothrombin 20210 G/G as compared to those with the G/A genotype (P=0.031). However, Bonferroni correction for the three SNPs investigated in this series rendered the P value insignificant (P(corrected)=0.093).

CONCLUSION

We did not find a statistically significant association of SNP factor V Leiden G1691A and MTHFR C677T with renal graft survival. Prothrombin G20210A resulted in a significant association that was not sustained after Bonferroni correction. This SNP might be an interesting candidate for future studies.

A new PCR-SSP typing method for six single-nucleotide polymorphisms impairing the blood-clotting cascade as well as T-cell stimulation

Single-nucleotide polymorphisms (SNPs) within the genes of factor V (FV) (G1691A; exon 10), prothrombin (FII) (G20210A; 3'untranslated - region) and methylenetetrahydrofolate reductase (MTHFR) (C677T; exon 4) are associated with hypercoagulability, and systematic screening of individuals being at higher risk of thrombosis has been suggested. SNPs in the 2q33 region within the genes of CD28 (+17T/C; intron 3) and CTLA4 (-318C/T; promoter and +49A/G; exon 1) are likely to affect T-cell proliferation and antigen presentation signaling, which may lead to altered sensitivity of allograft or self-tissue recognition and affect the incidence of autoimmune diseases. We developed primers that allow specific amplification of these six SNPs at test conditions identical with those used for HLA typing with the CTS PCR-SSP reagents. One hundred ninety-six healthy German Caucasian individuals were tested for the six SNPs. The genotype frequencies for all SNPs were in Hardy-Weinberg equilibrium. There was no significant difference in the distribution of genotypes when compared to other published studies in which these SNPs were tested. The described PCR-SSP method can be used to screen large numbers of patients for these SNPs.

Description and characterization of two new HLA alleles, B*4051 and DRB1*1364, identified by sequence-based typing*

Human leukocyte antigen (HLA)-B and HLA-DRB1 typing in two female individuals revealed reaction patterns that did not correspond to any known HLA-B specificity and appeared to identify a very rare HLA-DRB1 allele, respectively. Sequence-based analysis of these samples revealed two new HLA alleles, one similar to B*4023 and the other to DRB1*1308. The new HLA-B allele, which was assigned the name HLA-B*4051, could have been generated by a double crossing over recombination between B*4001 and B*1401 or 1402, whereas DRB1*1364, the new DRB1 allele, could have been generated either by a double crossing over recombination between DRB1*1308 and DRB1*1201, 1202, or 1203 or by two independent crossing over events between DRB1*1401, DRB1*1201, 1202, or 1203 and DRB1*1301.

Identification of two new HLA alleles: B*3546* and B*5611*. How reliable are the published HLA-B intron 2 sequences?

Polymerase chain reaction-sequence-specific primer (PCR-SSP) typing for human leukocyte antigen (HLA)-B in a male 25-year-old Caucasian individual of Iranian origin and in a 42-year-old German Caucasian bone marrow donor revealed reaction patterns that did not agree with any known HLA specificity, thus suggesting in both cases the existence of a novel allele. Sequence-based typing (SBT) after allelic separation revealed the sequences of the new alleles HLA-B*5611 and B*3546. The sequence patterns of both new alleles might have been generated as the results of double crossing over, possibly over several generations. During the analysis of the HLA-B*3546 intron 2 sequence for possible crossing over points, a base insert, an additional G after position 700, was found. This insert was analyzed using SBT and PCR-SSP and was found to be present not only in all samples carrying B*35, but also in all HLA-B specificities tested. It appears that all known HLA-B alleles may contain a G insert at position 700 of intron 2, and that the published intron 2 sequence alignments of the HLA-B locus may contain errors at this position.

Detection of reverse transcriptase activity in human melanoma cell lines and identification of a murine leukemia virus contaminant

BACKGROUND

Stimulated by earlier reports on the presence of retroviruses in mouse and hamster melanoma cell lines, we addressed the question as to whether human melanoma cell lines might also harbour a retrovirus.

METHODS AND RESULTS

The melanoma cell lines SK-MEL-25, SK-MEL-28, MEL-JUSO, MML-I, MeWo, A-375, Colo-38, BS-780 were confirmed to be human by human leucocyte antigen (HLA) typing, and supernatants were tested by the product-enhanced reverse transcriptase (PERT) assay for reverse transcriptase (RT) activity. Cell lines SK-MEL-25, SK-MEL-28, MEL-JUSO and MML-I were positive, whereas cell lines MeWo, A-375, Colo-38 and BS-780 were negative. The RT activity peaked at a buoyant density in sucrose typical for retroviruses. From this peak fraction an R-U5 sequence indistinguishable from murine leukemia virus (MLV) was identified by particle-associated retrovirus RNA amplification (PARRA). Semiquantitative MLV-specific RNA-PCR demonstrated colocalization of the MLV-like RNA and RT activity on the sucrose gradient of SK-Mel-25. MLV RNA and DNA were also detectable in culture supernatants of SK-MEL-28, MEL-JUSO and MML-I, but not of MeWo, A-375, Colo-38 and BS-780 by semiquantitative polymerase chain reaction (PCR). Sequence comparison revealed highest homology with the RET sequence previously identified in mouse myeloma SP2/0-AG14 cells. Taken together, our data strongly suggest that certain human melanoma cell lines are productively infected by a MLV which was probably introduced during tumour passage in mice or by laboratory contamination many years ago and subsequently spread to other lines.

CONCLUSION

We recommend mandatory testing of melanoma and other human cell lines for contamination with infectious MLV or other animal retroviruses, similar to mycoplasma screening, in order to avoid artificial experimental data.

Relevance of IL10, TGFbeta1, TNFalpha, and IL4Ralpha gene polymorphisms in kidney transplantation: a collaborative transplant study report

Single nucleotide polymorphisms (SNPs) of cytokine genes have been shown to influence cytokine plasma levels. Cytokines are important mediators during organ graft rejection. It was reported that certain cytokine genotypes are associated with improved kidney graft survival. In the present study, SNPs within the IL10 promoter gene, the first exon of the TGFbeta1 gene, the TNFalpha promoter gene, and the IL4Ralpha gene were analyzed in 2298 first and 1901 repeat cadaver kidney recipients. We found no significant effect on the survival rate of first grafts. Among retransplants, we observed that recipients who were homozygous for the high TNFalpha producer genotype -308 A had a significantly lower graft survival rate than patients who were carriers of the low producer genotype -308 G (at 3 years: 63.0% vs. 79.5%; pcorrected = 0.0116). The results of this large-scale study suggest that IL10, TGFbeta1, TNFalpha, and IL4Ralpha cytokine genotypes do not affect the survival of primary kidney grafts. The outcome of retransplants appears to be affected by TNFalpha genotypes only.

Mycophenolate mofetil-based immunosuppression and cytokine genotypes: effects on monokine secretion and antigen presentation in long-term renal transplant recipients

BACKGROUND

It has been suggested that increased monocyte responses might play a role in chronic allograft rejection.

METHODS

We investigated in vitro monokine responses in 112 patients with long-term stable kidney graft function (ST patients; n=80, non-mycophenolate mofetil [MMF]; n=32, MMF) and 25 patients with chronic renal transplant rejection (CR patients; non-MMF). Interleukin 10 and tumor necrosis factor (TNF)-alpha promoter gene polymorphisms were tested by polymerase chain reaction and sequence-specific primers; antigen-presenting capacity (AC) of monocytes was tested by incubation with staphylococcal superantigens (SEA, SEE, SED).

RESULTS

Although non-MMF-based immunosuppression in ST patients did not result in compromised AC or lipopolysaccharide (LPS)-stimulated monokine responses compared with healthy controls, we found MMF therapy to be associated with significantly reduced TNF-R1 expression on monocytes (P<0.001), suppressed AC (P<0.02, SED), and suppressed LPS-stimulated IL-1 beta, IL-10, and TNF-alpha secretion (P<0.01). Coinciding with a significantly higher steroid dosage in CR patients, IL-6 receptor and TNF-R1 expression on monocytes were down-regulated (P< or =0.02) and AC was suppressed in CR compared with ST (non-MMF) patients (P<0.01, SED; P<0.05, SEE). However, LPS-stimulated monokine secretion was not decreased or even enhanced (IL-6, granulocyte-macrophage colony-stimulating factor [GM-CSF]; P<0.05). Enhanced in vitro IL-10 responses (>500 pg/mL) were found predominantly in non-MMF-treated patients with the IL-10 genotype GCC (GCC: 23/62 [37%], non-GCC: 2/27 [7%], P<0.005; GCC and non-MMF: 22/47 [47%], GCC and MMF: 1/15 [7%], P<0.005].

CONCLUSION

Steroids and azathioprine did not sufficiently suppress monokine responses, whereas MMF treatment might inhibit chronic graft rejection because of suppression of TNF-R1 expression and vigorous inhibition of monokine secretion. MMF treatment may especially be indicated in patients with the IL-10 "high-producer" genotype GCC.

A new epitope-based HLA-DPB matching approach for cadaver kidney retransplants

BACKGROUND

Several years ago a significant impact of matching for HLA-DPB1 alleles on the survival of cadaver kidney retransplants was shown. Here we report the results of a new approach, based on matching for HLA-DPB1 epitopes.

METHODS

The analysis is based on 1,478 patients who received a cadaver kidney retransplant between 1988 and 1998. DNA methodology (polymerase chain reaction, sequence-specific oligonucleotides) was used to perform HLA-DPB1 typing. Epitope matching was facilitated with the aid of sequence databases and computer calculations.

RESULTS

Matching for the HLA-DP epitopes A, B, E, and F, corresponding to the homonymous hypervariable regions of the second exon of the DPB1 gene, seems to have a greater influence on graft survival than matching for the epitopes C and D. Within a group of 529 retransplants with exactly one allelic HLA-DPB1 mismatch, a significantly better graft outcome was observed when less than two epitope mismatches were found, compared with the group with more than three epitope mismatches (at 2 years: 77.8% vs. 65.8%, P=0.0112). Importantly, patients with two DPB1 allele mismatches who had less than or equal to two epitope mismatches exhibited a significantly better graft outcome than recipients who had one HLA-DPB1 allelic mismatch but more than three epitope mismatches (at 2 years: 77.1% vs. 65.8%, P=0.0488).

CONCLUSIONS

The findings indicate that the impact of HLA-DPB1 matching on the outcome of kidney retransplants is a result of the predominant immunogenicity of certain epitopes of the HLA-DP molecule. Matching for immunogenic HLA-DPB1 epitopes seems to be functionally more relevant than classical matching at the allelic level.

Association between human papillomavirus 16 E6 variants and human leukocyte antigen class I polymorphism in cervical cancer of Swedish women

Persistent infection with human papillomavirus (HPV), particularly HPV16, represents the prime risk factor in cervical carcinogenesis. HPV variants (e.g., within the E6 gene) together with immunogenetic factors of the host may be responsible either for effective viral clearance, or alternatively, for viral persistence. Peripheral blood from 27 HPV16 positive Swedish women with cervical carcinoma, who had previously been tested for HPV16 E6 variants, was used for human leukocyte antigen (HLA) class I typing. Women with HLA-B*44, HLA-B*51, or HLA-B*57 who were infected with the HPV16 E6 variant L83V had an approximately four- to fivefold increased risk for cancer compared with controls (odds ratio [OR] = 3.5, 95% CI = 1.1-11.1, OR = 4.2, 95% CI = 1.19-14.69, or OR = 4.67, 95% CI = 1.2-18.6, respectively). Epitope predictive algorithm with SYFPEITHI revealed that the variant at amino acid 83 affects the binding affinity in association with HLA-B*44. Interestingly, the HLA-B*15 allele seems protective because it was absent in HPV16 positive cancer. It is concluded that specific HLA class I alleles, combined with certain HPV16 E6 variants, may be crucial for immune surveillance in cervical carcinogenesis. The evaluation of associations of HLA alleles with HPV variants may be helpful in defining prognostic markers and in designing vaccines capable of mediating immune protection against HPV infection.

A new HLA-DRB allele (DRB1*15014) identified in a Caucasian individual

Polymerase chain reaction with sequence specific primers subtyping of a DRB1*15 allele in a male 11-year-old German Caucasian and his father revealed a reaction pattern that did not agree with any known specificity, thus suggesting the existence of a novel allele. Sequence-based typing after allelic separation revealed the new allele human leukocyte antigen (HLA)-DRB1*15014. The sequence pattern of HLA-DRB1*15014 might have been generated as a result of two independent recombinations, most likely over several generations.

Characterization of a new HLA-A allele, A*0256, identified in a Caucasian individual

HLA-A typing by the PCR-SSP method in a male 21-year-old Caucasian individual revealed a very rare allele combination corresponding to a unique reaction pattern. Therefore, the result was examined using sequence-based typing. Sequencing of exons 2 and 3 of the HLA-A locus after allelic separation with specific primers revealed the sequence of a new allele, similar to A*0245. Sequencing of exons 1 and 4 resulted in no additional inconclusive positions. The sequence pattern of the new allele HLA-A*0256 might have been generated as a result of a double crossing over recombination of an A*0201 and either an A*03 or an A*11.

Prominent T cell response to a selectively in vivo expressed Borrelia burgdorferi outer surface protein (pG) in patients with Lyme disease

Diagnosis of Lyme disease by analysis of T cell immune responses in vitro is curtailed by poor correlation between test results and status of infection. This is probably due to the inherent nonspecific activation potential of the causative agent, the spirochete Borrelia burgdorferi, for bystander lymphocytes, in particular via their outer surface lipoproteins. We have now applied a novel protocol to determine specific T cell responses in Lyme disease patients and exclude unrelated cellular responses in vitro. Non-lipidated spirochetal antigens (OspA, OspC and P39) including those selectively expressed in the mammalian host (pG and BapA) were used for antigenic stimulation and autologous dendritic cells served as antigen-presenting cells. The majority of patients with well-defined early and late manifestations of Lyme disease exhibited specific T cell proliferative responses to one or more of the indicated antigens, however at distinct levels. Most notably, among the five antigens tested, pG was specifically recognized by the majority of T cell populations (>70%) - mainly Th1 cells - from patients but not control individuals. These data indicate a causal relationship between B. burgdorferi infection and T cell reactivity to pG, thus making this protein a promising additional diagnostic marker for Lyme disease.

Passenger lymphocyte syndrome with severe hemolytic anemia due to an anti-Jk(a) after allogeneic PBPC transplantation

BACKGROUND

After allogeneic peripheral blood progenitor cell (PBPC) transplantation, a patient developed a severe hemolytic transfusion reaction due to passenger lymphocyte syndrome.

CASE REPORT

A 50-year-old woman with secondary acute myeloid leukemia transforming from a myelodysplastic syndrome received an ABO-compatible PBPC graft from her HLA-identical sister. For prophylaxis of GVHD, the patient was treated with cyclosporine and methotrexate. Eighteen days after the transplant, the patient experienced a severe hemolytic transfusion reaction due to an alloantibody (anti-Jk(a)) produced by donor lymphocytes.

RESULTS

The patient was typed as group A, Jk(a+) before transplantation; the donor was typed as group A, Jk(a-). On Day 18 after transplantation, the immunohematologic screening revealed a positive DAT (C3d 3+) and an alloanti-Jk(a). Hemolysis in the patient at that time was indicated by a drop in the Hb and an increase in the LDH level (maximum, 592 IU/L on Day 23).

CONCLUSION

The course of hemolysis and the time of appearance of an alloantibody in this patient meet the criteria for passenger lymphocyte syndrome. In most cases, this syndrome is triggered by ABO system antibodies. This is the first reported case of passenger lymphocyte syndrome after PBPC transplantation that was due to an alloantibody that did not belong to the ABO system.

High-resolution typing for HLA-DRB1*15 amd -DRB1*16 by fluorescence-marked sequence-specific priming (TaqMan assay)

Sequence-specific primed polymerase chain reaction (PCR-SSP) is widely used in HLA laboratories. The TaqMan method, which is described here for high-resolution typing of HLA-DRB1*15 and -DRB1*16, does not require elaborate and time-consuming post-PCR detection steps. In this one-tube assay, conventional PCR-SSP and fluorescence detection of the amplicon with a doubly labeled fluorescent probe are combined: a fluorogenic hybridization probe (FHP) labeled with a spectral resolvable fluorescent reporter dye (FAM or TET) at its 5' terminus and a common quencher dye (TAMRA) at its 3' terminus is cleaved by the 5' nuclease activity of Taq DNA polymerase only if the target sequence is amplified. An increase of fluorescence intensity indicates a successful amplification. For high-resolution typing of HLA-DRB1*15 and -DRB1*16 alleles we designed two FHPs and 14 specific primer mixes (7 for DR15 and 7 for DR16). Amplification of the specific sequence was detected by a FAM-labeled FHP, whereas amplification of the internal control was detected by a TET-labeled FHP. We were able to type all heterozygous DRB1*15/DRB1*16 subtype combinations. For evaluation, 60 HLA-DRB1*15-positive and 40 HLA-DRB1*16-positive individuals were typed and the results were compared with conventional PCR-SSP DR15/16 subtyping. There were no discrepancies between the two methods. The TaqMan method is an alternative to conventional PCR-SSP typing which is suitable for routine use in HLA laboratories.

Comparison of serological and DNA PCR-SSP typing results for HLA-A and HLA-B in 421 Black individuals: a Collaborative Transplant Study report

In a recent study, we observed a discrepancy rate of 8.5% between the results of molecular and serological HLA class I typing in Caucasian kidney donors and recipients. In the present study we addressed the question how often black individuals are mistyped using the serological technique. 421 Blacks whose HLA typing results were reported to the Collaborative Transplant Study (CTS) were typed retrospectively for HLA-A and -B using a PCR-SSP method. 78 of the 421 individuals (18.5%) showed a discrepancy for HLA-A and 107 individuals (25.4%) for HLA-B. 36.3% of all individuals tested showed either an HLA-A or an HLA-B discrepancy. 13.1% of the discrepancies at the HLA-A locus were due to antigen misassignments and 4.8% were due to missed antigens. HLA-B discrepancies were caused in 15.7% by antigen misassignments and in 10.5% by missed antigens. These results demonstrate an impressive advantage of the PCR-SSP method for HLA-A and HLA-B locus typing over serological typing in black individuals. The high typing discrepancy rate observed in Blacks provides a strong argument for replacing serological typing by the DNA method. It is likely that this will improve the HLA matching correlation in clinical transplantation in Blacks.

Comparison of typing results by serology and polymerase chain reaction with sequence-specific primers for HLA-Cw in 650 individuals

HLA-Cw typing by standard serological techniques is associated with a high frequency of blanks, and reliable typing reagents for several of the Cw specificities are scarce. We evaluated the PCR-SSP technique for Cw typing in 370 kidney transplant patients and 280 healthy blood donors. Serological typing of all individuals was performed in our laboratory from 1995 to 1997 using commercially available tissue-typing trays. Comparison between serological and PCR-SSP typing revealed a discrepancy rate of 33.6% (n= 94) in blood donors and 32.4%) (n=120) in kidney recipients. Incorrect antigen assignments occurred only rarely (3.6% of the blood donors and 3.2% of the kidney recipients). The vast majority of discrepancies were due to antigens that were not detected serologically. In 26 individuals no Cw antigen was detected by serological typing, whereas PCR-SSP showed 1 allele in 13 and 2 alleles in the other 13 cases. Another 269 individuals were typed serologically with one blank (presumably homozygous). Of these, only 108 were confirmed to be homozygous, whereas an additional Cw allele was found in the remaining 161 cases using the SSP technique. Most of the "missed" specificities (86.5%) were those for which serological reagents were not available (HLA-Cw*12-*17). The most commonly "missed" specificity was HLA-Cw*1203, which occurred in 13.9% of the healthy blood donors. These results indicate that serological HLA-Cw typing is insufficient for examining the clinical importance of HLA-Cw matching in transplantation. Future studies based on molecular typing should allow the proper investigation of HLA-Cw matching in kidney and bone marrow transplantation.