High prevalence of human polyomavirus JC VP1 gene sequences in pediatric malignancies.

The oncogenic potential of human polyomavirus JC (JCV), a ubiquitous virus that establishes infection during early childhood in approximately 70% of the human population, is unclear. As a neurotropic virus, JCV has been implicated in pediatric central nervous system tumors and has been suggested to be a pathogenic agent in pediatric acute lymphoblastic leukemia. Recent studies have demonstrated JCV gene sequences in pediatric medulloblastomas and among patients with colorectal cancer. JCV early protein T-antigen (TAg) can form complexes with cellular regulatory proteins and thus may play a role in tumorigenesis. Since JCV is detected in B-lymphocytes, a retrospective analysis of pediatric B-cell and non-B-cell malignancies as well as other HIV-associated pediatric malignancies was conducted for the presence of JCV gene sequences. DNA was extracted from 49 pediatric malignancies, including Hodgkin disease, non-Hodgkin lymphoma, large cell lymphoma and sarcoma. Polymerase chain reaction (PCR) was conducted using JCV specific nested primer sets for the transcriptional control region (TCR), TAg, and viral capsid protein 1 (VP1) genes. Southern blot analysis and DNA sequencing were used to confirm specificity of the amplicons. A 215-bp region of the JCV VP1 gene was amplified from 26 (53%) pediatric tumor tissues. The JCV TCR and two JCV gene regions were amplified from a leiomyosarcoma specimen from an HIV-infected patient. The leiomyosarcoma specimen from the cecum harbored the archetype strain of JCV. Including the leiomyosarcoma specimen, three of five specimens sequenced were typed as JCV genotype 2. The failure to amplify JCV TCR, and TAg gene sequences in the presence of JCV VP1 gene sequence is surprising. Even though JCV TAg gene, which is similar to the SV40 TAg gene, is oncogenic in animal models, the presence of JCV gene sequences in pediatric malignancies does not prove causality. In light of the available data on the presence of JCV in normal and cancerous colon epithelial tissue and our data on amplification of JCV from the cecum of an HIV-infected pediatric patient, further studies are warranted on the role of colon epithelium in the pathogenesis of JCV infection.

Modulation of adhesion molecules and monocyte chemoattractant protein by tumor necrosis factor-alpha and salicylic acid in primary human coronary artery endothelial cells.

Kawasaki disease (KD) is an illness characterized by vascular inflammation of coronary arteries leading to coronary aneurysms and thromboses. Infiltration of immune cells into the intima and adventitia are observed in autopsy tissues of patients with KD. Using semi-quantitative RT-PCR and cell-based ELISA, we demonstrated that tumor necrosis factor-a induced the expression of intercellular adhesion molecules-1 and E-selectin, as well as monocyte chemoattractant protein-1, in a time- and dose-dependent manner in primary human coronary artery endothelial cell cultures. This increase was inhibited by salicylic acid (NaSal), and involved the transcription factor NF-kappaB. Based on these data, we suggest a pathogenetic mechanism for KD, whereby immune cells are attracted to sites of inflammation, undergo extravasation, release enzymes that assist in vascular remodeling, thereby weakening the endothelium and hastening the process of aneurysm formation. NaSal, in addition to preventing thrombosis and lowering fever in KD, may also function in down-regulating adhesion molecules during the inflammatory stage of KD.

RT-PCR detection of the expression of the polymerase gene of a novel reptilian herpesvirus in tumor tissues of green turtles with fibropapilloma.

An alpha-herpesvirus has recently been associated with green turtle fibropapilloma (FP). To further understand the etiological role of this newfound green turtle herpesvirus (GTHV) in the pathogenesis of FP, expression of GTHV polymerase ( pol) gene was determined in tumors and normal-appearing nontumor tissues and organs from five green turtles suffering multiple fibropapillomas, using reverse transcription-polymerase chain reaction (RT-PCR). Amplification of RNA prepared from tumor tissues evidenced the substantial expression of GTHV DNA pol gene in all specimens tested (15/15). However, GTHV pol gene expression in normal-appearing tissues and organs of affected animals was limited (4/45), and GTHV mRNA was detected only in periorbital tissue (1/2), gall bladder (2/5) and lung (1/5) by nested RT-PCR. By contrast, RT-PCR evaluation of RNA isolated from non-tumored turtles revealed undetectable expression of this herpesvirus gene. cDNA sequence analysis revealed that GTHV gene sequences were identical in different tumors. Our data represent the first evidence of the replication of this putative turtle herpesvirus in affected green turtles and fibropapilloma tissues are always active sites of GTHV mRNA synthesis. These findings extend and substantiate the pathogenic association of GTHV with FP.

Highly active antiretroviral therapy (HAART)-associated lactic acidosis: in vitro effects of combination of nucleoside analogues and protease inhibitors on mitochondrial function and lactic acid production.

Lactic acidosis is a rare but potentially life-threatening and poorly understood sequelae among HIV-infected patients on highly active antiretroviral therapy (HAART). Mitochondrial DNA depletion and inhibition of respiratory complexes have been hypothesized to be involved in HAART-associated lactic acidosis. Although mitochondrial toxicity and increased plasma lactates are associated with long-term exposure to nucleoside analogue reverse transcriptase inhibitors (NRTI), reports of lactic acidosis are now emerging among HIV-infected patients exposed to combination therapy that includes not only NRTI but also protease inhibitors (PI). We therefore investigated the effects of clinically relevant NRTI and PI combinations on mitochondrial membrane potential, uncoupling of mitochondrial respiration from oxidative phosphorylation and lactic acid production. Our study demonstrated that treatment of HepG2 cells with a combination of nucleoside analogues and PI, decreased mitochondrial membrane potential (delta psi m) within 24 hr, followed by increased lactic acid production after 9 days of treatment. However, loss of delta psi m and increased lactates were not associated with mitochondrial uncoupling or ATP production. Our findings suggested that not only NRTI but also PI are capable of increasing lactic acid production in vitro, and probably involve early biochemical changes in mitochondrial function such as loss of mitochondrial membrane potential.

Sterol regulatory element-binding proteins and reactive oxygen species: potential role in highly-active antiretroviral therapy (HAART)-associated lipodystrophy.

OBJECTIVES: To summarize the existing pathophysiological concepts and to hypothesize new mechanisms involving sterol regulatory element-binding proteins (SREBP) and reactive oxygen species (ROS), in highly-active antiretroviral therapy (HAART)-associated lipodystrophy. CONCLUSIONS: The widespread use of HAART has dramatically reduced AIDS-related deaths in the developed world. Unfortunately, long-term HAART has been associated with a unique and unexpected syndrome of lipodystrophy manifested by fat wasting in the subcutaneous adipose tissue of the face and extremities, and accumulation of fat in the viscera and neck, often accompanied by hyperlipidemia and insulin resistance. Despite intensive study of this syndrome over the past three years, the pathophysiologic mechanism(s) underlying HAART-associated lipodystrophy syndrome remains elusive. A continued attempt to elucidate pathophysiological mechanisms involved in HAART-associated lipodystrophy remains critically important to improving the treatment strategies for this epidemic condition. In this review, we suggest two new hypotheses that may explain the pathogenesis and pathophysiology of HAART-associated lipodystrophy that warrant further investigations. First, we hypothesize that upregulation and/or increase in the mature form of SREBP-1 caused by HAART may lead to perturbations in synergistic regulation of genes involved in maintenance of cholesterol homeostasis and synthesis of fatty acids, that may explain the accumulation of fat which is a hallmark of this syndrome. Second, we hypothesize that the generation of reactive oxygen species in adipocytes may be an early and critical event in HAART-associated toxicity leading to cell death, partially explaining the mechanism underlying lipoatrophy.

Predicted amino acid sequences for 100 JCV strains.

DNA sequence variation between JCV genotypes is confined largely to noncoding intergenic regions and introns. Nevertheless, evidence suggests that the amino acid sequence variations among the 8 genotypes of JCV can influence the potential for neurovirulence of the virus. In the current study, the amino acid sequences for 100 JCV genomes were translated and grouped into genotype families. Subtype consensus sequences were determined and the type-specific amino acid sequence variants were identified.

Reconstructing population history using JC virus: Amerinds, Spanish, and Africans in the ancestry of modern Puerto Ricans.

The roots of the Hispanic populations of the Caribbean Islands and Central and South America go back to three continents of the Old World. In Puerto Rico major genetic contributions have come from (1) Asians in the form of the aboriginal Taino population, an Arawak tribe, present when Columbus arrived on the Island, (2) Europeans, largely Spanish explorers, settlers, government administrators, and soldiers, and (3) Africans who came as part of the slave trade. Since JC virus (JCV) genotypes characteristic of Asia, Europe, and Africa have been identified, and excretion of JCV in urine has been proposed as a marker for human migrations, we sought to characterize the JCV strains present in a Caribbean Hispanic population. We found that the strains of JCV present today in Puerto Rico are those derived from the Old World populations represented there: Types 1B and 4 from Spain, Types 3A, 3B, and 6 from Africa, and Type 2A from Asia. The Type 2A genotype represents the indigenous Taino people. This JCV genotype was represented much more frequently (61%) than would be predicted by the trihybrid model of genetic admixture. This might be attributable to characteristics of JCV Type 2A itself, as well as to the nature of the early relationships between Spanish men and native women. These findings indicate that the JCV strains carried by the Taino Indians can be found in today's Puerto Rican population despite the apparent demise of these people more than two centuries ago. Therefore, molecular characterization of JCV provides a tool to supplement genetic techniques for reconstructing population histories including admixed populations.

Rapid acquisition of entire DNA polymerase gene of a novel herpesvirus from green turtle fibropapilloma by a genomic walking technique.

A 4837-bp sequence of a newfound green turtle herpesvirus (GTHV), implicated in the etiology of green turtle fibropapilloma, was obtained from tumor tissues of a green turtle with fibropapilloma using a genomic walking method based on restriction enzyme digestion, self-ligation and inverse polymerase chain reaction (IPCR). The 4837-bp sequence was 56.23% G/C rich and contained three nonoverlapping open reading frames (ORF). The largest ORF (3507-bp) encoded the DNA polymerase gene (pol gene), which exhibited a high degree of homology at both amino acid and nucleotide levels with the DNA pol genes of human and animal herpesviruses, with a predicted protein of 1169 amino acids and molecular weight of 132.6 kilodaltons. The ATG at 518 to 520 was the first initiation codon in the ORF and was presumed to be the first methionine codon of the pol gene. Phylogenetic analysis, based on the amino acid sequence of the GTHV DNA pol gene and the corresponding regions of other known human and animal herpesviruses, indicated that GTHV belonged to the Alphaherpesvirinae subfamily. The upstream ORF of the pol gene encoded the N-terminal region of the GTHV homologue of the DNA-binding protein gene, whereas the downstream ORF was the C-terminal region of a gene which was homologous to ORFs conserved in human and animal herpesviruses, i.e., herpes simplex virus 1 (HSV1) gene UL31, Epstein-Barr virus (EBV) gene BFLF2, equine herpesvirus 1 (EHV1) gene 29, and alcelaphine herpesvirus 1 (AHV1) hypothetical protein 69 gene. The arrangement of these three genes in GTHV genome was identical to that seen in other alphaherpesviruses. The sequence and location of the DNA pol gene in the GTHV genome should greatly facilitate future studies of the viral life cycle.

Fecal excretion of a novel human circovirus, TT virus, in healthy children.

The role of TT virus (TTV) as a human pathogen is unclear, as is the mode of TTV transmission. To determine the prevalence of TTV infection and the possible fecal-oral route of transmission, we analyzed fecal specimens from 67 healthy, nontransfused children for TTV DNA sequences by heminested PCR, using the NG and T primer sets. The overall prevalence of TTV fecal excretion was 22.4% (15 of 67), with the T primer set (19.4%) being more sensitive than the NG primer set (10.4%). TTV prevalence based on gender or ethnicity showed no significant differences. None of seven children in the 0- to 6-month age group had detectable TTV in feces. Of three sets of siblings, two unrelated sets of twins, ages 33 and 37 months, were negative for fecal TTV DNA, while the third set of siblings, ages 99 and 35 months, was positive. The absence of TTV in the feces of children younger than 6 months and the high prevalence (40%) in children 7 to 12 months of age is consistent with age-specific acquisition of TTV infection by the nonparenteral route. TTV genotypes 1, 3, 4, and 5 were represented in our study population. TTV-positive siblings had TTV genotypes 1 and 4, suggesting unrelated environmental sources of TTV infection. This observation suggests a possible time frame for TTV acquisition in children which coincides with increased interaction with their environment and increased susceptibility to infectious agents.

Detection of herpesviral sequences in tissues of green turtles with fibropapilloma by polymerase chain reaction.

An alpha-herpesvirus has been associated recently with green turtle fibropapilloma (FP). To further clarify the role of this newfound green turtle herpesvirus (GTHV) in the pathogenesis of FP, various normal-appearing tissues and organs (including skin, eye, brain, heart, liver, spleen, intestine, lung, kidney, nerve, gonad, tongue, gall bladder, urinary bladder, thyroid and peripheral blood mononuclear cells (PBMC) from blood) and tumor tissues from 19 green turtles (Chelonia mydas) with FP, and tissues from three green turtles without FP, collected during 1997 to 1999 in the Hawaiian Islands, were tested for GTHV sequences by nested polymerase chain reaction (PCR), using GTHV-specific oligonuclotide primers. GTHV sequences were detected in all tumors (51/51) and most tissues (133/167) of tumored turtles. By contrast, such sequences were undetectable in tissues (0/28) of three non-tumored turtles. Analysis of GTHV sequences detected in different tissues and tumors revealed a low degree of genetic diversity (<1%). The wide distribution of this newfound herpesvirus in tumors and tissues of tumored green turtles and its absence in tissues of non-tumored turtles, argues for an etiologic role in FP.

Identification of a small, naked virus in tumor-like aggregates in cell lines derived from a green turtle, Chelonia mydas, with fibropapillomas.

Serial cultivation of cell lines derived from lung, testis, periorbital and tumor tissues of a green turtle (Chelonia mydas) with fibropapillomas resulted in the in vitro formation of tumor-like cell aggregates, ranging in size from 0.5 to 2.0 mm in diameter. Successful induction of tumor-like aggregates was achieved in a cell line derived from lung tissue of healthy green turtles, following inoculation with cell-free media from these tumor-bearing cell lines, suggesting the presence of a transmissible agent. Thin-section electron microscopy of the cell aggregates revealed massive collagen deposits and intranuclear naked viral particles, measuring 50+/-5 nm in diameter. These findings, together with the morphological similarity between these tumor-like cell aggregates and the naturally occurring tumor, suggest a possible association between this novel virus and the disease. Further characterization of this small naked virus will clarify its role in etiology of green turtle fibropapilloma, a life-threatening disease of this endangered marine species.

Amplification and analysis of DNA flanking known sequences of a novel herpesvirus from green turtles with fibropapilloma Brief report.

A 1,632-bp fragment, flanking the original 483-bp region of the DNA polymerase gene of a novel herpesvirus found in tissues of green turtles (Chelonia mydas) with fibropapilloma, was amplified from the circularized EcoRI-cut DNA extracted from tumor tissues by inverse PCR. The resultant 2,019-bp partial sequence of the DNA polymerase gene of the newfound herpesvirus, including the original 483-bp region, showed a high degree of homology at both the nucleotide and amino acid levels with that of other human and animal herpesviruses. Phylogenetic analysis confirmed that this novel herpesvirus belonged to the Alphaherpesvirinae subfamily.

Lack of association between acquisition of TT virus and risk behavior for HIV and HCV infection in Vietnam.

BACKGROUND: The search for the cause of chronic hepatitis among individuals with non-A to G hepatitis has led to the discovery of a post-transfusion hepatitis-related DNA virus, designated TT virus (TTV), which, based on viral sequences, belongs to a new virus family. The principal modes of infection with TTV are poorly understood, and its role in human immunodeficiency virus type 1 (HIV-1) infection is unclear. OBJECTIVE: To determine if injection drug use (IDU) and high-risk heterosexual activity (HRHA), principal modes of acquiring HIV-1 infection, place individuals at greater risk of acquiring TTV. METHODS: The authors analyzed DNA, extracted from sera or filter paper-blotted whole blood, obtained during August 1997 and June 1998 from 324 Vietnamese (148 male; 176 female), for TTV sequences by hot-start, heminested polymerase chain reaction. RESULTS: Prevalence of TTV viremia was similar among individuals engaging in IDU or HRHA (23.4% vs. 20.2%; P > 0.5), with no age- or gender-specific differences. No association was found between TTV viremia and co-infection with HIV-1 or hepatitis C virus (HCV). Phylogenetic analysis of 30 TTV sequences revealed two distinct genotypes and four subtypes that did not segregate according to gender, HIV-1 and HCV risk behaviors, or geographic residence. CONCLUSIONS: Among HIV-1- or HCV-infected Vietnamese, who presumably acquired their infection by either the parenteral or nonparenteral route, the data indicate no clear association between acquisition of TTV infection and risk behavior for HIV-1 or HCV infection, suggesting that the usual route of TTV transmission in Vietnam is other than parenteral or sexual.

Genotype and allele frequency of a 32-base pair deletion mutation in the CCR5 gene in various ethnic groups: absence of mutation among Asians and Pacific Islanders.

BACKGROUND: A 32-base pair (bp) deletion mutation in the beta-chemokine receptor CCR5 gene has been associated with resistance against human immunodeficiency virus type 1 (HIV-1) infection and disease. Large-scale studies conducted among Caucasians indicate that individuals who are homozygous for this deletion mutation (D32/D32) are protected against HIV-1 infection despite multiple high-risk exposures, whereas CCR5/ D32 heterozygotes have a slower progression to acquired immunodeficiency syndrome (AIDS). OBJECTIVE: To determine the genotype and allele frequencies of the CCR5 gene 32-bp deletion mutation among ethnically diverse non-Caucasian populations. METHODS: DNA, extracted from blood collected between 1980 and 1997 from 1912 individuals belonging to various ethnic groups, including 363 Caucasians, 303 Puerto Rican Hispanics, 150 Africans, 606 Asians, and 490 Pacific Islanders, were analyzed for the CCR5 gene 32-bp deletion mutation by a polymerase chain reaction (PCR)-based assay, using an oligonucleotide primer pair designed to discriminate CCR5 alleles without restriction endonuclease analysis. RESULTS: The comparative frequency of CCR5/D32 heterozygosity was 61 of 363 (16. 8%) in Caucasians, 17 of 303 (5.6%) in Puerto Rican Hispanics, 9 of 490 (1.8%) in Pacific Islanders, 0 of 606 (0%) in Asians, and 0 of 150 (0%) in Africans. CONCLUSIONS: The data confirm the high frequency of CCR5/D32 heterozygosity among Caucasians. Intermediate and low-level D32 allele frequencies among Puerto Rican Hispanics and Hawaiians could be attributed to recent European Caucasian gene flow. By contrast, the inability to detect the D32 allele among Asians and other Pacific Islander groups suggests that other mechanisms are responsible for resistance to HIV-1 infection in these populations.

Establishment and characterization of 13 cell lines from a green turtle (Chelonia mydas) with fibropapillomas.

Thirteen cell lines were established and characterized from brain, kidney, lung, spleen, heart, liver, gall bladder, urinary bladder, pancreas, testis, skin, and periorbital and tumor tissues of an immature male green turtle (Chelonia mydas) with fibropapillomas. Cell lines were optimally maintained at 30 degrees C in RPMI 1640 medium supplemented with 10% fetal bovine serum. Propagation of the turtle cell lines was serum dependent, and plating efficiencies ranged from 13 to 37%. The cell lines, which have been subcultivated more than 20 times, had a doubling time of approximately 30 to 36 h. When tested for their sensitivity to several fish viruses, most of the cell lines were susceptible to a rhabdovirus, spring viremia carp virus, but refractory to channel catfish virus (a herpesvirus), infectious pancreatic necrosis virus (a birnavirus), and two other fish rhabdoviruses, infectious hematopoietic necrosis virus and viral hemorrhagic septicemia virus. During in vitro subcultivation, tumor-like cell aggregates appeared in cell lines derived from lungs, testis, and periorbital and tumor tissues, and small, naked intranuclear virus particles were detected by thin-section electron microscopy. These cell lines are currently being used in attempts to isolate the putative etiologic virus of green turtle fibropapilloma.

High prevalence of GB virus C/hepatitis G virus infection among homosexual men infected with human immunodeficiency virus type 1: evidence for sexual transmission.

GB virus C/hepatitis G virus (GBV-C/HGV), a recently discovered orphan flavivirus, is distantly related to hepatitis C virus (HCV). Although both GBV-C/HGV and HCV can be transmitted by the parenteral route, their principal modes of transmission and associated risk behaviors may differ. Using reverse transcription-polymerase chain reaction, the 5'-noncoding regions of GBV-C/HGV and HCV were amplified from plasma or sera of 209 individuals infected with human immunodeficiency virus type 1 (HIV-1). As verified by Southern blot analysis, GBV-C/HGV and HCV infection were detected in 37 (17.7%) and 22 (10.5%) of 209 HIV-1-infected individuals, respectively. GBV-C/HGV infection was significantly associated with homosexual sex (P = 0.044) and was more common than HCV infection among HIV-1-infected homosexual men (P = 0.006). The prevalence of GBV-C/HGV infection was nearly equal in women infected with HIV-1 via high-risk heterosexual sex (14.0%) or injection drug use (IDU) (17.5%). By contrast, HCV infection was associated significantly with women reporting IDU when compared to women reporting high-risk heterosexual sex (P < 0.0001). Alanine aminotransferase levels were elevated in HIV-1-infected individuals who were co-infected with HCV (P = 0.009), but not with GBV-C/HGV (P = 0.9). The high prevalence of GBV-C/HGV infection in HIV-1-infected nondrug-injecting homosexual men and among women engaging in high-risk heterosexual sex is consistent with transmission by the mucosal route and with acquisition of infection by the receptive rather than insertive partner.

CCR5 chemokine receptor genotype frequencies among Puerto Rican HIV-1-seropositive individuals.

Some individuals remain uninfected by human immunodeficiency virus type 1 (HIV-1), despite multiple sexual contacts with subjects with confirmed HIV-1 infection. Several studies have confirmed that individuals who are homozygous for a 32 base pair (bp) deletion mutation in the chemokine receptor gene CCR5, designated as delta 32/ delta 32, are protected against HIV-1 infection. Heterozygotes of the same chemokine receptor deletion mutation are, however, not protected from acquiring HIV-1 infection but seemingly have slower progression to acquired immunodeficiency syndromes (AIDS). Genotype frequencies of the delta 32 CCR5 mutation vary markedly among different ethnic groups; heterozygosity is found in approximately 15% of Caucasians, about 5-7% of Hispanics and African Americans and 1% or less of Asians. The ethnic background of Puerto Ricans is highly complex and usually includes admixture of Caucasian, Caribbean Indian and African traits to a varying extent. This study was conducted to examine the frequencies of the delta 32 CCR5 mutation among Puerto Ricans who are infected with HIV-1. Samples were received from different geographical regions of the island. Of 377 samples tested, 94.2% were wild type (non-deletion mutant) homozygotes, 5.8% were delta 32 CCR5 heterozygotes, and none were delta 32 CCR5 homozygotes. The incidence of CCR5 delta 32/w heterozygous mutation among Puerto Ricans seems to be somewhat lower than what was reported with US Hispanics. Some age and gender associated bias of the mutation frequency were observed with the study population, the reason for which is unclear at present.

Complete nef gene sequence of HIV type 1 subtype B' from professional plasma donors in the People's Republic of China.

PIP: Probably more than 150,000 people are infected with HIV in China. Although HIV-1 infection was initially limited to the southern province of Yunnan, it is increasingly spreading in the interior of the country, and multiple HIV-1 subtypes have been identified, including B, C, and E. Envelope (env) gene sequences of HIV-1 strains from Yunnan resemble HIV subtype B' strains from Thailand. The authors analyzed the nef gene from HIV-1-infected professional plasma donors to determine if deletions and/or insertions are present in the nef gene of HIV-1 strains from China. Blood was collected from 3 men of mean age 42 years and 4 women of mean age 40 between December 1996 and April 1997 in eastern China, blotted onto neonatal 903 filter paper and allowed to dry, then analyzed. Sequence alignment and comparison of the gene found that the HIV-1 strains from China diverged from well-characterized subtype B strains from North America, Thailand, and Papua New Guinea by 9.6-16.7% and 8-20% at the nucleotide and deduced amino acid levels, respectively. On the basis of sequence and phylogenetic analyses of a 550-nucleotide region spanning the main neutralizing domain, the V3 loop, of the gp120-encoding env gene, all of the 7 strains from China were more similar to the subtype B' HIV of Thailand than to the subtype B of North America.^ieng

CCR5 chemokine receptor genotype frequencies among Puerto Rican HIV-1-seropositive individuals

Some individuals remain uninfected by human immunodeficiency virus type 1 (HIV-1), despite multiple sexual contacts with subjects with confirmed HIV-1 infection. Several studies have confirmed that individuals who are homozygous for a 32 base pair (bp) deletion mutation in the chemokine receptor gene CCR5, designated as delta 32/ delta 32, are protected against HIV-1 infection. Heterozygotes of the same chemokine receptor deletion mutation are, however, not protected from acquiring HIV-1 infection but seemingly have slower progression to acquired immunodeficiency syndromes (AIDS). Genotype frequencies of the delta 32 CCR5 mutation vary markedly among different ethnic groups; heterozygosity is found in approximately 15% of Caucasians, about 5-7% of Hispanics and African Americans and 1% or less of Asians. The ethnic background of Puerto Ricans is highly complex and usually includes admixture of Caucasian, Caribbean Indian and African traits to a varying extent. This study was conducted to examine the frequencies of the delta 32 CCR5 mutation among Puerto Ricans who are infected with HIV-1. Samples were received from different geographical regions of the island. Of 377 samples tested, 94.2% were wild type (non-deletion mutant) homozygotes, 5.8% were delta 32 CCR5 heterozygotes, and none were delta 32 CCR5 homozygotes. The incidence of CCR5 delta 32/w heterozygous mutation among Puerto Ricans seems to be somewhat lower than what was reported with US Hispanics. Some age and gender associated bias of the mutation frequency were observed with the study population, the reason for which is unclear at present