A new blood group system, RHAG: three antigens resulting from amino acid substitutions in the Rh-associated glycoprotein

BACKGROUND AND OBJECTIVES

Rh-associated glycoprotein (RhAG) is closely associated with the Rh proteins in the red cell membrane. Two high frequency antigens (Duclos and DSLK) and one low frequency antigen (Ol(a)) have serological characteristics suggestive of expression on RhAG.

MATERIALS AND METHODS

RHAG was sequenced from the DNA of one Duclos-negative, one DSLK-negative, and two Ol(a+) individuals. Recombinant protein was expressed in HEK 293 cells. Protein models with RhAG subunits were constructed.

RESULTS

The original Duclos-negative patient was homozygous for RHAG 316C>G, encoding Gln106Glu. HEK 293 cells expressing Gln106Glu mutant RhAG did not react with anti-Duclos. An individual with DSLK-negative red cells was homozygous for 490A>C, encoding Lys164Gln. Two Ol(a+) members of the original Norwegian family were heterozygous for 680C>T, encoding Ser227Leu. A Japanese donor with Rh(mod) phenotype had Ol(a+) red cells and was homozygous for 680C>T.

CONCLUSION

The three red cell antigens encoded by RHAG form the RHAG blood group system: Duclos is RHAG1 (030001); Ol(a) is RHAG2 (030002); and DSLK is provisionally RHAG3 (030003).

Phase II clinical trial with a second generation, GM-CSF encoding, oncolytic herpesvirus in unresectable metastatic melanoma

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Background: OncoVEXGM-CSF is a an oncolytic HSV, encoding GM-CSF . We recently completed a phase II trial involving 50 advanced melanoma patients (stage IIIc and IV) with at least one injection accessible lesion, including by ultrasound. Methods: Patients received a single IT injection of 106 pfu/ml apportioned between 10 or less injectable tumors, followed 3 wks later by 24 or less sequential injections of 108 pfu/ml every 2 wks until clinically significant disease progression, or overall or injectable lesion complete response. Response (RECIST modified to allow progression before response and biopsy of residual masses) and survival were monitored. Results: All 50 pts have been enrolled and are evaluable (Stage IIIc, n=10; IV M1a, n=16; IV M1b, n=4; IV M1c, n=20). A median of 6 injections were administered. Adverse effects were limited and generally involved transient flu-like symptoms. Both injected and uninjected regional and distant disease demonstrated response including clearly documented responses at uninjected visceral sites. The overall response rate was 26% (8 CR, 5 PR); 10 responses have been maintained for >6 months and 2 are ongoing at <6months, the longest currently being at 35 months from first dose. 93% of patients (14 of 15) with PR, CR or surgical CR remain alive. Ten additional patients had SD for >3 months. Kaplan Meier one year survival is 61% overall, 58% stage IV only, 48% for Stage IV M1c. The median OS is 16+ months. Conclusions: The 1-year survival and durable objective response rate are encouraging. Responses of distant and visceral disease provide further compelling evidence of systemic effectiveness. This, combined with a limited toxicity profile, suggests OncoVEXGM-CSF is a promising treatment for metastatic melanoma. A phase III clinical trial is planned.

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Lutheran

The Lutheran blood group system consists of 19 antigens: four pairs of antithetical antigens--Lu(a)/Lu(b), Lu6/Lu9, Lu8/Lu14, and Au(a)/Au(b)--and 11 antigens of very high frequency. These antigens are located on four of the five immunoglobulin-like domains of both isoforms of the Lutheran glycoprotein. The LU gene is on chromosome 19 and comprises 15 exons. The two glycoprotein isoforms differ in the length of their cytoplasmic tails as a result of alternative splicing of intron 13. Lu(null) phenotype arises from homozygosity for inactivating mutations in the LU gene.The dominantly inherited Lu(mod) phenotype, In(Lu), results from heterozygosity for inactivating mutations in KLF1, the gene for the erythroid transcription binding factor EKLF. Clinically, antibodies of the Lutheran system are relatively benign. When hemolytic, they generally cause only mild, delayed hemolytic transfusion reactions or hemolytic disease of the fetus and newborn that can be treated by phototherapy. The Lutheran glycoproteins, which are members of the immunoglobulin superfamily of adhesion molecules and receptors, bind isoforms of laminin with alpha5 chains,components of the extracellular matrix abundant in vascular endothelia. The primary function of the Lutheran glycoproteins on RBCs could involve the transfer of maturing RBCs from the bone marrow to the peripheral circulation. They could also be involved in vascular occlusion and thrombotic events as complications of sickle cell disease and polycythemia vera, respectively.

Controlled propagation of replication-competent Sindbis viral vector using suicide gene strategy

A major concern of using viral gene therapy is the potential for uncontrolled vector propagation and infection that might result in serious deleterious effects. To enhance the safety, several viral vectors, including vectors based on Sindbis virus, were engineered to lose their capability to replicate and spread after transduction of target cells. Such designs, however, could dramatically reduce the therapeutic potency of the viral vectors, resulting in the need for multiple dosages to achieve treatment goals. Earlier, we showed that a replication-defective (RD) Sindbis vector achieved specific tumor targeting without any adverse effects in vivo. Here, we present a replication-competent Sindbis viral vector that has an hsvtk suicide gene incorporated into ns3, an indispensable non-structural gene for viral survival. The capability of viral propagation significantly increases tumor-specific infection and enhances growth suppression of tumor compared with the conventional RD vectors. Furthermore, in the presence of the prodrug ganciclovir, the hsvtk suicide gene serves as a safety mechanism to prevent uncontrolled vector propagation. In addition to suppressing vector propagation, toxic metabolites, generated by prodrug activation, could spread to neighboring uninfected tumor cells to further enhance tumor killing.

Functions of red cell surface proteins

The external membrane of the red cell contains numerous proteins that either cross the lipid bilayer one or more times or are anchored to it through a lipid tail. Many of these proteins express blood group activity. The functions of some of these proteins are known; in others their function can only be surmised from the protein structure or from limited experimental evidence. They are loosely divided into four categories based on their functions: membrane transporters; adhesion molecules and receptors; enzymes; and structural proteins that link the membrane with the membrane skeleton. Some of the proteins carry out more than one of these functions. Some proteins may complete their major functions during erythropoiesis or may only be important under adverse physiological conditions. Furthermore, some might be evolutionary relics and may no longer have significant functions. Polymorphisms or rare changes in red cell surface proteins are often responsible for blood groups. The biological significance of these polymorphisms or the selective pressures responsible for their stability within populations are mostly not known, although exploitation of the proteins by pathogenic micro-organisms has probably played a major role.

Report of the Second International Workshop on molecular blood group genotyping

The second International Society of Blood Transfusion and International Council for Standardization in Haematology workshop on molecular blood group genotyping was held in 2006. Forty-one laboratories participated. Six samples were distributed: two representing DNA from transfusion-dependent patients for testing for all clinically important polymorphisms; two representing DNA from amniotic fluid for RhD, Rhc, and K testing; and two plasma samples from RhD-negative pregnant women for fetal RhD testing (only tested by 20 laboratories). Overall, a high level of accuracy was achieved by most of the laboratories, although the error rate caused by RHDPsi was not acceptable and needs to be addressed. With greater care and attention to detail, very high standards could be set for molecular blood group genotyping.

Sequence variation in the 5' untranslated region of the human A4GALT gene is associated with, but does not define, the P1 blood-group polymorphism

BACKGROUND AND OBJECTIVE

The gene responsible for the P1 polymorphism of the P blood-group system remains unidentified, although the A4GALT gene, whose product is responsible for the production of P(k), has been implicated. No coding differences in A4GALT account for the P1 polymorphism, but homozygosity for two polymorphisms (-551_-550insC and -160A>G) in the 5' untranslated region of the gene has been reported to be unique to Japanese P1- individuals. This study aimed to confirm this correlation in a larger number of British individuals.

MATERIALS AND METHODS

Serologically confirmed P1+ (n = 35) and P1- (n = 15) individuals were genotyped for polymorphisms in the 5' untranslated region of A4GALT.

RESULTS

In addition to those previously reported, a further polymorphism, -164C>T, was identified. All P1- individuals were homozygous for -551_-550insC and -160G as compared with 10 of 35 (29%) P1+ individuals (P = 0.000003, two-tailed Fisher's exact test). Allele frequencies for all polymorphisms and estimated haplotype frequencies across the region differed significantly between P1+ and P1- groups.

CONCLUSIONS

Homozygosity for the A4GALT-551_-550insC and -160G allele is significantly associated with, but not restricted to, the P1- phenotype. No single A4GALT genotype or haplotype was unique to P1- individuals. Thus, A4GALT cannot be unequivocally confirmed as the gene responsible for the P1 phenotype.