Frequency of HLA-A*02:01 in the Brazilian population and its impact on uveal melanoma systemic treatment.

Uveal melanoma is a rare malignancy originating from extracutaneous melanocytes on the uveal layer of the eyes. The incidence varies depending on the ethnic and racial global distribution, as uveal melanoma is more frequently diagnosed in non-Hispanic White subjects when compared with Hispanic, Asian, or Black individuals. Despite all the local effective management of uveal melanoma, roughly 50% of the cases will develop distant metastases. For these cases, the historical median overall survival is around 12 months. Recently, tebentafusp became the first therapy to receive Food and Drug Administration approval following a phase 3 trial demonstrating a continued long-term benefit for overall survival among adult HLA-A*02:01-positive patients with previously untreated metastatic uveal melanoma. Since 2021, high-resolution sequence-based HLA typing has been considered the gold standard for determining HLA alleles and haplotypes for the Brazilian Bone Marrow Donor Registry (REDOME) donors. To depict the HLA-A*02:01-positivity in Brazilian individuals, the REDOME database was queried out for the donors included from 2021 to 2023 and tested for HLA in high-resolution platforms. A total of 203,  44 donors were included and the frequency of the HLA-A*02:01 was 21.01%, much lower compared to the frequency in North Americans and Europeans (around 45%). Despite tebentafusp has demonstrated promising results in the treatment of uveal melanoma, the number of patients to benefit from this new approach can strongly vary by ethnic and racial issues. New strategies for the systemic treatment of advanced uveal melanoma have to be developed and tested as this disease still represents an unmet medical need.

HLA-B27 positivity in a large miscegenated population of 5,389,143 healthy blood marrow donors in Brazil.

BACKGROUND: The prevalence of HLA-B27 gene positivity in healthy Caucasian communities varies between 8 and 14%. However, there is a lack of information in countries with a high rate of miscegenation, such as Brazil. AIM: To estimate the frequency of HLA-B27 in the Brazilian general population using a large national registry database. METHODS: This is a cross-sectional ecological study using the Brazilian Registry of Volunteer Bone Marrow Donors (REDOME) database on HLA-B27 allelic frequency and proportion of positives of healthy donors (18-60 years old). Data were analyzed according to sex, age, race (by self-reported skin color recommended by the Brazilian Institute of Geography and Statistics - IBGE), and geographic region of residence. RESULTS: From 1994 to 2022, a total of 5,389,143 healthy bone marrow donors were included. The overall positivity for HLA-B27 was 4.35% (CI 95% 4.32-4.37%), regardless of sex and age (57.2% were women, mean age was 41.7yo). However, there was a difference between races: 4.85% in Whites; 2.92% in Blacks; 3.76% in Pardos (Browns i.e. mixed races); 3.95% in Amarelos (Yellows i.e. Asian Brazilians); and 3.18% in Indigenous. There was also a difference regarding geographic region of residence (North: 3.62%; Northeast: 3.63%; Southeast: 4.29%; Midwest: 4.5% and 5.25% in South). The homozygosity rate for the HLA-B27 was 1.32% of all the positives and only 0.06% in the general population. CONCLUSIONS: Our findings provide the first Brazilian national prevalence for HLA-B27 in 4.35%. There is a gradient gene positivity from North to South, suggesting that the genetic background related to the miscegenation due to colonization, slavery, and some later waves of immigration together with internal migratory flows, could explain our findings.

HLA-B27 positivity in a large miscegenated population of 5,389,143 healthy blood marrow donors in Brazil

Abstract Background The prevalence of HLA-B27 gene positivity in healthy Caucasian communities varies between 8 and 14%. However, there is a lack of information in countries with a high rate of miscegenation, such as Brazil. Aim To estimate the frequency of HLA-B27 in the Brazilian general population using a large national registry database. Methods This is a cross-sectional ecological study using the Brazilian Registry of Volunteer Bone Marrow Donors (REDOME) database on HLA-B27 allelic frequency and proportion of positives of healthy donors (18-60 years old). Data were analyzed according to sex, age, race (by self-reported skin color recommended by the Brazilian Institute of Geography and Statistics - IBGE), and geographic region of residence. Results From 1994 to 2022, a total of 5,389,143 healthy bone marrow donors were included. The overall positivity for HLA-B27 was 4.35% (CI 95% 4.32-4.37%), regardless of sex and age (57.2% were women, mean age was 41.7yo). However, there was a difference between races: 4.85% in Whites; 2.92% in Blacks; 3.76% in Pardos (Browns i.e. mixed races); 3.95% in Amarelos (Yellows i.e. Asian Brazilians); and 3.18% in Indigenous. There was also a difference regarding geographic region of residence (North: 3.62%; Northeast: 3.63%; Southeast: 4.29%; Midwest: 4.5% and 5.25% in South). The homozygosity rate for the HLA-B27 was 1.32% of all the positives and only 0.06% in the general population. Conclusions Our findings provide the first Brazilian national prevalence for HLA-B27 in 4.35%. There is a gradient gene positivity from North to South, suggesting that the genetic background related to the miscegenation due to colonization, slavery, and some later waves of immigration together with internal migratory flows, could explain our findings.

How Ancestry Influences the Chances of Finding Unrelated Donors: An Investigation in Admixed Brazilians.

A match of HLA loci between patients and donors is critical for successful hematopoietic stem cell transplantation. However, the extreme polymorphism of HLA loci - an outcome of millions of years of natural selection - reduces the chances that two individuals will carry identical combinations of multilocus HLA genotypes. Further, HLA variability is not homogeneously distributed throughout the world: African populations on average have greater variability than non-Africans, reducing the chances that two unrelated African individuals are HLA identical. Here, we explore how self-identification (often equated with "ethnicity" or "race") and genetic ancestry are related to the chances of finding HLA compatible donors in a large sample from Brazil, a highly admixed country. We query REDOME, Brazil's Bone Marrow Registry, and investigate how different criteria for identifying ancestry influence the chances of finding a match. We find that individuals who self-identify as "Black" and "Mixed" on average have lower chances of finding matches than those who self-identify as "White" (up to 57% reduction). We next show that an individual's African genetic ancestry, estimated using molecular markers and quantified as the proportion of an individual's genome that traces its ancestry to Africa, is strongly associated with reduced chances of finding a match (up to 60% reduction). Finally, we document that the strongest reduction in chances of finding a match is associated with having an MHC region of exclusively African ancestry (up to 75% reduction). We apply our findings to a specific condition, for which there is a clinical indication for transplantation: sickle-cell disease. We show that the increased African ancestry in patients with this disease leads to reduced chances of finding a match, when compared to the remainder of the sample, without the condition. Our results underscore the influence of ancestry on chances of finding compatible HLA matches, and indicate that efforts guided to increasing the African component of registries are necessary.

HLA-Matched Unrelated Donors for Patients with Sickle Cell Disease: Results of International Donor Searches.

Sickle cell disease (SCD) is the most common inherited hemoglobinopathy. Hematopoietic stem cell transplantation (HCT) is the sole curative therapy for SCD, but few patients will have a matched sibling donor. Patients with SCD are mostly of African origin and thus are less likely to find a matched unrelated donor in international registries. Using HaploStats, we estimated HLA haplotypes for 185 patients with SCD (116 from a Brazilian center and 69 from European Society for Blood and Marrow Transplantation [EBMT] centers) and classified the ethnic origin of haplotypes. Then we assessed the probability of finding an HLA-matched unrelated adult donor (MUD), considering loci A, B, and DRB1 (6/6), in international registries. Most haplotypes were African, but Brazilians showed a greater ethnic admixture than EBMT patients. Nevertheless, the chance of finding at least one 6/6 potential allelic donor was 47% for both groups. Most potential allelic donors were from the US National Marrow Donor Program registry and from the Brazilian REDOME donor registry. Although the probability of finding a donor is higher than previously reported, strategies are needed to improve ethnic diversity in registries. Moreover, predicting the likelihood of having an MUD might influence SCD management.

The distribution of HLA haplotypes in the ethnic groups that make up the Brazilian Bone Marrow Volunteer Donor Registry (REDOME).

The Registries of Bone Marrow Donors around the world include more than 30 million volunteer donors from 57 different countries, and were responsible for over 17,000 hematopoietic stem cell transplants in 2016. The Brazilian Bone Marrow Volunteer Donor Registry (REDOME) was established in 1993 and is the third largest registry in the world with more than 4.3 million donors. We characterized HLA allele and haplotypes frequencies from REDOME comparing them with the donor self-reported race group classification. Five-locus haplotype frequencies (A~C~B~DRB1~DQB1) were estimated for each of the six race groups, resolving phase and allelic ambiguity using the expectation-maximization (EM) algorithm. The top 100 haplotypes in the race groups were separated into eight clusters of haplotypes, based on haplotype similarity, using CLUTO. We present HLA allele and haplotype frequency data from six race groups from 2,938,259 individuals from REDOME. The most frequent haplotype was the same for all groups: A*01:01g~C*07:01g~B*08:01g~DRB1*03:01g~DQB1*02:01g. Some frequent haplotypes such as A*02:01g~C*16:01g~B*44:03~DRB1*07:01g~DQB1*02:01g was not found in people with Preta (Sub-Saharan African descent). A cluster including Branca (European) and Parda or non-informed (admixed) could be distinguished from both Preta (SubSaharan) and Indígena (Amerindian) groups, and from the Amarela (Asian) ones, which clustered with their original population. These results have implications on cross-population matching and can help in donor searches and population-based recruitment strategies.

Less graft-versus-host disease after rabbit antithymocyte globulin conditioning in unrelated bone marrow transplantation for leukemia and myelodysplasia: comparison with matched related bone marrow transplantation.

One of the major drawbacks for unrelated donor (UD) bone marrow transplantation (BMT) is graft-versus-host disease (GVHD). Despite results from randomized trials, antithymocyte globulin (ATG) is not routinely included for GVHD prophylaxis in UD BMT by many centers. One of ways to demonstrate the usefulness of rabbit ATG in UD BMT is to evaluate how its results approximate to those observed in matched related (MRD) BMT. Therefore, we compared the outcomes between UD BMT with rabbit ATG (Thymoglobulin) for GVHD prophylaxis (n = 25) and MRD BMT (n = 91) for leukemia and myelodysplasia. All but one patient received a myeloablative conditioning regimen. Grades II-IV acute GVHD were similar (39.5% vs. 36%, p = 0.83); however, MRD BMT recipients developed more moderate-severe chronic GVHD (36.5% vs. 8.6%, p = 0.01) and GVHD-related deaths (32.5% vs. 5.6%, p = 0.04). UD BMT independently protected against chronic GVHD (hazard ratio 0.23, p = 0.04). The 6-month transplant-related mortality, 1-year relapse incidence, and 5-year survival rates were similar between patients with non-advanced disease in the MRD and UD BMT groups, 13.8% vs. 16.6% (p = 0.50), 20.8% vs. 16.6% (p = 0.37), and 57% vs. 50% (p = 0.67), respectively. Stable full donor chimerism was equally achieved (71.3% vs. 71.4%, p = 1). Incorporation of rabbit ATG in UD BMT promotes less GVHD, without jeopardizing chimerism evolution, and may attain similar survival outcomes as MRD BMT for leukemia and myelodysplasia especially in patients without advanced disease.

Transplante de sangue de cordão umbilical - SCU / Umbilical cord blood transplantation

A frequente utilização de sangue de cordão umbilical - SCU como fonte de células- tronco hematopoéticas - CTH, tanto em crianças, como em adultos, que não dispõem de doador na família, tem levado ao estabelecimento da padronização de critérios em sua seleção, objetivando a obtenção de melhores resultados. A escolha da unidade de SCU deve basear-se no número total de células nucleadas e no número de diferenças de antígenos leucocitários humanos (HLA). Diante de uma unidade com celularidade mínima, deve-se considerar a possibilidade da utilização de duplo cordão. Frente a mais de uma unidade com características semelhantes, a realização da contagem de células CD34 e da compatibilidade ABO, assim como a qualidade e a rapidez para obtenção da unidade, podem definir a escolha.

The frequent use of umbilical cord blood as the source of hematopoietic stem cells, both in children and adults who do not have related donors, has led to the establishment of a better standardization of selection criteria aiming at improving the results. The choice of the umbilical cord blood unit should be based on the total number of nucleated cells and the number of differences in the human leukocyte antigen (HLA) system. When a unit has minimal cellularity, the use of a double cord blood transplant should be considered. When two or more units have similar characteristics, the choice may be determined by the CD34 count, ABO compatibility and the quality and speed to obtain the unit.

Seleção de doador de medula óssea ou sangue periférico / Bone marrow or peripheral blood donor selection

A compatibilidade HLA é o fator mais valorizado na escolha do doador de medula óssea voluntário, preconizando-se a realização de HLA de alta resolução nos locos HLA-A,B,C, DRB1 e DQB1. Tem sido dado preferência para o doador com consanguinidade alélica 8x8 (A,B,C, DRB1). Na presença de incompatibilidade na classe-I sugere-se a busca de doador com compatibilidade DQB1 (9x10). Já as incompatibilidades dos locos DPB1 não constituem critério de exclusão de doador, exceto quando existir presença de anticorpo contra o loco HLA-DP do doador.

The HLA system is considered the most important factor in choosing a volunteer bone marrow donor with the recommendation of performing high resolution HLA tests for the HLA-A, B, C, DRB1 and DQB1 loci. A preference has been given for donor 8x8 (A, B, C, DRB1) allele matching. In the presence of class-I incompatibility a search for DQB1 (9x10) donor compatibility is suggested. The incompatibility of the DPB1 locus does not constitute exclusion of the donor, except when there is the presence of antibodies against the HLA-DP locus of the donor.

Seleção de doador não aparentado / HLA antibodies and donor selection

Apesar da presença de anticorpos anti-HLA em transplantes de órgãos sólidos estar associada à rejeição, essa correlação não havia sido pesquisada em transplante alogênico de células progenitoras hematopoéticas (TCPH). Estudos mais recentes na literatura têm demonstrado que a falência da enxertia no TCPH pode ser mediada por aloanticorpos anti-HLA doador especifico (DSA). A especificidade desses anticorpos pode ser evidenciada pelas técnicas de fase sólida, onde os antígenos HLA únicos são aderidos a pérolas de poliestireno, que permite a realização da prova cruzada virtual. Na presença de DSA, é recomendável selecionar outro doador ou realizar as estratégias de remoção dos anticorpos.

In spite of Anti-HLA antibodies being associated to rejection in solid organs transplantation, this correlation has not been well established yet in allogenic bone marrow transplantation.Recent studies in the literature have demonstrated that engraftment failure in hematopoietic cell transplantation (HCT) can be mediated by donor specific anti-HLA antibodies (DSA). These antibodies specificity can be detected by solid-phase techniques, where single HLA antigens are adhered to microbeads, which allows the interpretation of host reactivity by "virtual crossmatch". In the presence of DSA, it is advisable to either search for another donor or remove the antibodies prior to transplantation.

In vivo study of the anti-inflammatory and antitumor activities of leaves from Plectranthus amboinicus (Lour.) Spreng (Lamiaceae).

ETHNOPHARMACOLOGICAL RELEVANCE: Plectranthus amboinicus (Lour.) Spreng is a medicinal specie often used in Brazil, especially in Northeast Region, for the treatment of several diseases including inflammations and cancer. AIM OF THE STUDY: To evaluate the anti-inflammatory and antitumor activities of the hydroalcoholic extract from leaves of P. amboinicus in an attempt to determine whether the medicinal uses are supported by pharmacological effects. MATERIALS AND METHODS: Anti-inflammatory activity was determined by carrageenan-induced paw edema method. The antitumor effect was evaluated in an in vivo experimental study, using the following tumors: Sarcoma-180 and Erlich ascite carcinoma. RESULTS: There were statistically significant decreases (p<.05) of edema paw in at the doses of 150, 250 and 350 mg/kg (i.p.) of the hydroalcoholic extract of P. amboinicus. Similarly, the administration of P. amboinicus at the doses of 100, 150, 250 and 350 mg/kg (i.p.) inhibited the growth of sarcoma-180 and Ehrlich ascite carcinoma tumors in mice. CONCLUSION: The results suggest that the hydroalcoholic extract of P. amboinicus possesses anti-inflammatory and antitumor activities, supporting the folk use of this medicinal specie.