Marcela Salazar

Major histocompatibility complex class II alleles and haplotypes and blood groups of four Amerindian tribes of Northern Colombia

MHC class II alleles and haplotypes were determined from unrelated individuals and families of the Arhuaco (n = 107), Kogi (n = 42), Arsario (n = 18), and Wayú (n = 88) tribes located in the northern part of Colombia. Class II DRB, DQA1, and DQB1 alleles were determined by PCR-SSO and PCR-RFLP based methods. Four haplotypes, [DRB1*0407, DRB4*0101, DQA1*03, DQB1*0302]; [DRB1*0403, DRB4*0101, DQA1*03, DQB1*0302]; [DRB1*1402/1406, DRB3*0101, DQA1*0501, DQB1*0301]; and [DRB1*0802, DQA1*0401, DQB1*0402], were observed among these four tribes. In addition to these haplotypes, the Wayú Indians showed a frequency of 21.3% for the [DRB1*1602, DRB5*02, DQA1*0501, DQB1*0301] haplotype, 13.1% for the [DRB1*0411, DRB4*0101, DQA1*03, DQB1*0302] haplotype, and 8.1% for the [DRB1*0411, DRB4*0101, DQA1*03, DQB1*0402] haplotype. Red cell antigen typing was used to calculate genetic admixture. The Kogi and Arsario showed no genetic admixture while the Arhuaco tribe showed admixture with genes of African origin and the Wayú showed admixture with Caucasians as well as genes of African origin. These findings were confirmed by the MHC class II allele and haplotype data obtained, as alleles and haplotypes of Caucasian and African origin were detected in the Wayú and Arhuaco and not in the Kogi or Arsario. These studies will be important in disease association and transplantation studies for Amerindian and colombian populations and for correlating genetic traits with the anthropologic and linguistic data available in order to better understand the Amerindian populations.

Normal HBsAg presentation and T-cell defect in the immune response of nonresponders

Lymphocytes from nonresponders to HBsAg fail to proliferate in vitro in the presence of HBsAg-pulsed antigen presenting cells. We studied four pairs of major histocompatibility complex (MHC)-matched, mixed lymphocyte reaction-negative individuals discordant for HBsAg response. For each pair, responder lymphocytes proliferated in the presence of nonresponder antigen-pulsed antigen presenting cells. Respondera nd nonresponder antigen presenting cells were equally effective. There was no evidence for inhibition of responder T-cell proliferation by nonresponder lymphocytes or antigen presenting cells. The defect is thus in the helper T cells of nonresponders and not in the antigen processing or binding of processed peptides to MHC molecules on antigen presenting cells.

The extent of HLA class II allele level disparity in unrelated bone marrow transplantation: analysis of 1259 National Marrow Donor Program donor-recipient pairs.

A comprehensive analysis of the HLA-D region loci, DRB1, DRB3, DRB5, DQA1, DQB1, DPA1 and DPB1, was performed to determine allelic diversity and underlying HLA disparity in 1259 bone marrow recipients and their unrelated donors transplanted through the National Marrow Donor Program. Although 43.0% of DRB1 alleles known to exist at the beginning of the study were found in this predominantly Caucasian transplant population, a few alleles predominated at each locus. In recipients, 67.1% of DRB1 alleles identified were one or two of six common DRB1 alleles. Only 118 (9.4%) donor–recipient pairs were matched for all alleles of DRB1, DQA1, DQB1, DPA1 and DPB1. While 79.4% of the pairs were matched for DRB1, only 13.2% were matched for DPB1 alleles. Almost 66% of pairs differed by more than one allele mismatch and 59.0% differed at more than one HLA-D locus. DQB1 was matched in 85.9% of DRB1-matched pairs. In contrast, only 13.9% of the pairs matched for DRB1, DQA1 and DQB1 were also matched for DPA1 and DPB1. This database, highlighting the underlying HLA disparity within the pairs, forms the foundation of an ongoing study to establish the relationship between HLA matching and successful outcome in unrelated allogeneic stem cell transplant. Bone Marrow Transplantation (2000) 25, 385–393.

Defect in Th1-Like Cells of Nonresponders to Hepatitis B Vaccine

Peripheral blood lymphocytes from nonresponders to hepatitis B vaccine (HBsAg) failed to undergo a proliferative response to recombinant HBsAg in vitro, whereas cells from responders proliferated vigorously. The lack of proliferative response was not due to defective antigen presentation in that MHC-identical responder and nonresponder antigen presenting cells were equally effective in stimulating responder T cells. Nonresponder T cells did not proliferate in response to antigen-pulsed MHC identical responder antigen presenting cells. The present study demonstrated that: 1) there were no detectable (1 in < 20 x 10(4) HBsAg-precursor T cells in any of the nonresponders, while in responders the frequency of HBsAg-precursor T cells ranged from 1 in 3.2 x 10(3) to 1 in 40 x 10(3); 2) nonresponder cell cultures did not secrete IL-2 in response to HBsAg stimulation; 3) exogenous recombinant IL-2 did not restore the proliferative response of the T cells in HBsAg-pulsed cultures of nonresponders. These results suggest that the cellular basis for the lack of response to HBsAg is a defect in HBsAg-specific Th1-like cells; either there is an absence of the Th1 cells or cells with TCR specificity for HBsAg are present but are unresponsive to the HBsAg peptide-MHC complex (i.e., anergy or tolerance).

Association of HLA-DRB1*1602 and DRB1*1001 with Takayasu arteritis in Colombian mestizos as markers of Amerindian ancestry

We performed HLA Class I and Class II typing in 16 patients (15 women, one man) with a confirmed diagnosis of Takayasu arteritis. We did not find any of the previously described associations with HLA-B52, and/or HLA-DRB1*1301 alleles. However, in our patients, HLA-DRB1*1602 and HLA-DRB1*1001 were significantly increased. The association of Takayasu arteritis with Amerindian and Asian HLA-DRB1 alleles (DRB1*1602 and DRB1*1001) in the Colombian mestizo patients reported here, and with HLA-B*3906 previously reported in Mexicans, suggest the possibility that some HLA and disease associations are markers for ethnicity of a population carrying a disease gene which is present in an admixed population with the disease.

A novel agent (Endozoicomonas elysicola) responsible for epitheliocystis in cobia Rachycentrum canadum larvae.

Aquaculture of cobia has gained popularity in the last decade, and this species is now farmed in several countries in Latin America and Asia. Despite recent improvement in production techniques that allowed the expansion of the industry, little is known about the diseases that affect cobia during the larviculture stage. In this article we investigated the cause of mass mortalities occurring 13-20 d post-hatching in 3 cycles of cobia larviculture. Wet mounts from diseased larvae gills revealed the presence of cyst-like basophilic inclusions. DNA from the cysts was extracted and PCR amplified using the 16S rRNA gene universal primers for prokaryotes. The amplified products were sequenced and analyzed using BLAST, finding a similarity of 99% with Endozoicomonas elysicola, a Gram-negative bacterium. Confirmation of E. elysicola was conducted by designing a specific probe for in situ hybridization. Specific primers were also designed for diagnostic purposes. This is the first report of epitheliocystis in cobia larvae and also the first report of E. elysicola as an epitheliocystis-causing agent.

Genetics of life span in mice

Thymic involution that occurs earlier in some individuals than others may be the result of complex interactions between genetic factors and the environment. Such interactions may produce defects of thymus-dependent immune regulation associated with susceptibility to developing autoimmune diseases, malignancy, and an increased number of infections associated with aging.The major histocompatibility complex may be important in determining profiles of cause of death and length of life in mice. Genetic influences on life span involve interactions between loci and allelic interactions during life which may change following viral infections or exposure to other environmental factors. We have used different experimental protocols to study the influence of H-2 on life span and found that interactions between genetic regions, are inconsistent, particularly when comparing mice infected or not infected with Sendai virus.Genes important for life span need to be studied against many genetic backgrounds and under differing environmental conditions because of the complexity of the genetics of life span. Several genetic models were used to demonstrate that the MHC is a marker of life span in backcross and intercross male mice of the H-2d and H-2b genotypes in B10 congenic mice. Females lived longer than males in backcross and intercross mice, while males lived longer than females in B10 congenics. H-2d was at a disadvantage for life span in backcross mice of the dilute brown and brown males exposed to Sendai infection, but intercross mice not exposed to Sendai virus of the same genotype were not at a disadvantage. H-2d mice were not disadvantaged when compared to H-2b in B10 congenics that had not been exposed to Sendai virus infection but the reverse was true when they were exposed. Overall, all our studies suggest that genetic influences in life span may involve interactions between loci and many allelic interactions in growing animals or humans. These genetic influences on life span may vary after they are exposed to infections or other environmental conditions. This paper emphasizes the need to use several genetic models, especially animals that have been monitored for infections, to study the genetics of life span.

Advances in HLA genetics.

The major histocompatibility complex (MHC) is a genetic system of over 70 known genes that occupies the midportion of the short arm of the sixth chromosome (C6p) and spans about 4 million base pairs of DNA. The high-resolution typing of class I and class II MHC genes and the identification of genes between and near them has increased the definition of the genetic basis of immune responses and diseases of unknown etiology such as autoimmune diseases in man. Although there are many more genetic systems that participate in the rejection of tissues and in the immune response, the MHC plays a central role in tissue compatibility and immune response against cancer and infectious diseases. In this paper, the authors review evidence about the role of HLA polymorphism in the pathogenesis and development of cancer, infectious diseases, autoimmune diseases and transplantation.

Characterization of a new strain of Taura syndrome virus (TSV) from Colombian shrimp farms and the implication in the selection of TSV resistant lines

Prior to 2004, Colombian shrimp farming benefited from a selection program in which Penaeus vannamei stocks were developed with resistance to Taura syndrome disease (TS). However since 2004, TS reappeared as a significant disease. In 2010, an apparently new strain of TSV (designated as CO 10) was collected in Colombia. Its genome was sequenced and compared with six other fully sequenced isolates. This analysis revealed that the TSV CO 10 is closely related to the isolates from Hawaii and Venezuela. Phylogenetic analysis based on capsid protein 2 (CP2) region from 59 TSV isolates shows that the recent Colombian isolates (2006-2010) form a new cluster and differ from the previous Colombia isolates (1994-1998) by 4% in nucleotide sequence. The virulence of this CO 10 isolate was similar to a Belize TSV determined through experimental infection in P. vannamei showing 100% mortalities and similar survival curves. By RT-qPCR for TSV, the viral loads were also close in the infected shrimp from both CO 10 and Belize at the order of 1×10(10) copies per μl RNA. To develop TSV-resistant lines, the candidate shrimp should be challenged with virus strains that have been isolated most recently from the regions where they will be cultured. This study suggests that the TSV present in Colombian shrimp farms during the last 5 years is a new TSV strain with high virulence.

Functional deficiency of antigen-presenting cells in the synovial fluid of rheumatoid arthritis

In our study of rheumatoid arthritis (RA) patients, we observed a decrease of tetanus toxoid antigen-presenting capacity of synovial fluid (SF) adherent cells to autologous T cells of either SF or peripheral blood. Additionally, we found a higher capacity of adherent synovial cells to stimulate autologous T-lymphocytes. Our results suggest that antigen-presenting cells of the SF of RA patients have defects that may play a role in defective presentation of antigens in joints and may account for other abnormal functions important in the pathogenesis of RA.