Frequency distribution of XbaIG > T and HaeIIIT > C GLUT1 polymorphisms among different Brazilian ethnic groups.

GLUT is the major glucose transporter in mammalian cells. Single nucleotide polymorphisms (SNP) at GLUT1 promoter and regulatory regions have been associated to the risk of developing nephropathy in different type 1 and type 2 diabetic populations. It has been demonstrated that differences in allelic and genotypic frequencies of GLUT1 gene (SLC2A1) polymorphisms occur among different populations. Therefore, ethnic differences in distribution of GLUT1 gene polymorphisms may be an important factor in determining gene-disease association. In this study, we investigated the XbaIG > T and HaeIIIT > C polymorphisms in six different Brazilian populations: 102 individuals from Salvador population (Northern Brazil), 56 European descendants from Joinville (South Brazil), 85 Indians from Tiryió tribe (North Brazil) and 127 samples from Southern Brazil: 44 from European descendants, 42 from African descendants and 41 from Japanese descendants. Genotype frequencies from both sites did not differ significantly from those expected under the Hardy-Weinberg equilibrium. We verified that the allele frequencies of both polymorphisms were heterogeneous in these six Brazilian ethnic groups.

Fas 670 promoter polymorphism is associated to susceptibility, clinical presentation, and survival in adult T cell leukemia.

Fas (TNFRSF6/Apo-1/CD95) is a type I transmembrane receptor, which mediates apoptosis. Fas gene mutations, aberrant transcripts, and abundant expression of Fas have been reported in adult T cell leukemia (ATL). To further elucidate the role of Fas in ATL pathogenesis, we investigated whether the -670 FAS promoter A/G polymorphism (STAT1-binding site) might contribute to susceptibility and clinical outcome in ATL. Thirty-one patients with ATL, 33 healthy, human T lymphotropic virus type 1-infected individuals, and 70 healthy, uninfected controls were genotyped for the FAS -670 polymorphism by PCR-restriction fragment-length polymorphism. The AA genotype was significantly over-represented in ATL patients in comparison with healthy controls (P=0.006), as well as asymptomatics (P=0.037), corresponding to an odds ratio (OR) of 3.79 [95% confidence intervals (CI; 1.28-11.41)] and 4.58 [95% CI (1.13-20.03)], respectively. The AA group also comprised significantly more aggressive (acute and lymphoma) clinical subtypes [P=0.012; OR=8.40; 95% CI (1.60-44.12)]. In addition, we observed a statistically significant association between GG genotype and survival (log rank test, P=0.032). Finally, IFN-gamma-induced but not basal FAS mRNA levels were increased significantly (P=0.049) in PBMCs from AA versus GG individuals, demonstrating the IFN-dependent functionality of the -670 polymorphism. In conclusion, our results demonstrate that a functional Fas promoter polymorphism is significantly associated to susceptibility, clinical manifestation, and survival in ATL.

Correlation between susceptibility of primary HIV-1 isolates to autologous and heterologous neutralizing antibodies. Hospital Evandro Chagas AIDS Clinical Research Group.

OBJECTIVE: To study the susceptibility of primary HIV-1 isolates towards autologous and heterologous neutralizing antibodies (NAb). DESIGN: Blood was collected and primary HIV-1 isolated from individuals residing in Rio de Janeiro, Brazil, in all phases of disease. METHODS: Primary HIV-1 isolates were incubated with autologous or heterologous plasma and neutralization of infection of freshly pre-stimulated normal human peripheral blood mononuclear cells was assayed in parallel to median infectious dose determinations in the absence of antibodies. Levels of HIV-1 p24 antigen were used for evaluation of viral neutralization. RESULTS: Autologous neutralization (75%) was observed for 13 (52%) out of 25 of the primary HIV-1 isolates, and 15 (71%) out of 21 isolates were susceptible to 75% heterologous neutralization by at least one-half of the heterologous plasma tested. Primary HIV-1 isolates susceptible to autologous NAb showed a higher susceptibility towards neutralization by heterologous NAb than isolates that could not be neutralized by the autologous plasma (P = 0.049). The susceptibility of the primary HIV-1 isolates towards neutralization by heterologous NAb was significantly higher for isolates derived from men (P = 0.001), and for isolates obtained from individuals infected through homo-/bisexual risk behaviour in comparison with those infected through heterosexual HIV-1 transmission (P = 0.03). CONCLUSIONS: Susceptibility of primary HIV-1 isolates to autologous and heterologous neutralization was significantly correlated, indicating that escape mutants may become resistant not only to autologous but also to heterologous NAb.

HIV infection of human choroid plexus: a possible mechanism of viral entry into the CNS.

The present study examines the hypothesis that HIV infection of the choroid plexus (CPx) may be an important site of viral entry into the brain. Formalin-fixed, paraffin-embedded CPx was obtained from 25 patients with AIDS and 13 nonAIDS patients and was processed for light microscopy and for immunohistochemical detection of HIV gp41, T and B lymphocytes, monocytes/macrophages and endothelial cells. Eleven of the 13 nonAIDS CPx were normal and 2 contained inflammatory foci of undetermined etiology. The stroma contained T lymphocytes in all and monocytes in 22%; B lymphocytes and HIV antigen were absent. Choroid plexus of the AIDS cases contained opportunistic infections or lymphoma in 12 and inflammatory foci alone in 6; 7 were normal. T lymphocytes were present in 70% and monocytes in 50%. In addition to the stromal localization, monocytes also were present in supra-epithelial regions and within or adjacent to the capillary endothelium. HIV-positive cells in the CPx were found in 11 cases (44%) and in the supra-epithelial area in another 2. Their presence correlated with neither infection nor lymphoma of the CPx or brain. They were situated in the stroma, supra-epithelial region and (rarely) capillary endothelium. Immunohistochemistry on serial sections identified the HIV-infected cells as monocytes, including those by capillary endothelium and in supra-epithelial areas. The study demonstrates that the CPx contains HIV-infected monocytes in almost half of the cases. Their apposition to endothelium suggests hematogenous origin. These results support the hypothesis that HIV encephalitis may develop from CPx infection.

HIV infection in 567 active pulmonary tuberculosis patients in Brazil.

We studied 567 patients with active pulmonary tuberculosis (APT) in Rio de Janeiro, Brazil, by using a standardized questionnaire and by testing blood for HIV antibodies. The rate of HIV infection was 3.9% in 1987, 4.8% in 1988, and 5.2% in 1989, and did not differ by sex. It was highest (7.4%) in the 15- to 39-year age group. There was no difference between patients infected and not infected by HIV with regard to education, income, housing, or employment. Among all patients with definite HIV risk behavior, the HIV infection rate was 23.3%, rising to 31.2% among homo/bisexual men and 36.4% among intravenous drug users, and the rate was 6.5% for blood-transfusion recipients. Among patients who denied risk behavior, the rate was 1.2%. Generalized lymphadenopathy and oral candidiasis occurred with greater frequency among HIV-infected patients (p < 0.0001). Applying the World Health Organization 1985 clinical criteria and revised case definition for AIDS, we found, respectively, sensitivities of 34% and 76.9% and specificities of 31% and 26.3%; in the Rio de Janeiro environment, these clinical criteria without HIV serology should not be adopted for tuberculosis patients. For chest radiographs, a significant association was found between HIV infection and the occurrence of atypical images (p = 0.0001), and hilar and/or mediastinal adenopathy (p = 0.0002) and absence of cavities (p = 0.0003). A PPD (purified protein derivative) skin test induration of < 5 mm was identified in 53% of the HIV-positive cases and in 31.3% of the HIV-negative cases. Only 11.5% of HIV-infected APT patients met the Centers for Disease Control 1987 AIDS criteria.

A protein A-binding, polyethylene glycol precipitation-based immunoradiometric assay. Application to the detection of immune complexes and C3 in human sera and of private antigens in cross-reacting parasite extracts.

An immunoradiometric assay, based on the precipitation of antigen-antibody complexes by polyethylene glycol (PEG) and on the subsequent binding of PEG-soluble radiolabelled staphylococcal protein A to the PEG-insoluble complexes, is described. The assay can be applied to the detection of naturally occurring, circulating immune complexes, and of complexes artificially created by mixing antigen and antibody solutions, which makes it of potential use for the detection of either antigen or antibody in several situations. Pre-treatment of the antibody-containing sera with 3% PEG greatly reduced the background values and increased the sensitivity of the assay. The assay was also applied to the detection and isolation of Leishmania donovani antigens that did not cross-react with antigens of the related parasite Trypanosoma cruzi (private antigens) and private antigens of insect-derived metacyclic trypomastigotes of T. cruzi in relation to culture-derived metacyclic trypomastigotes of T. cruzi. A simple and extremely effective procedure for washing precipitates with just one centrifugation is also described.

Dot enzyme immunoassay. A simple, cheap and stable test for antibody to human immunodeficiency virus (HIV).

A dot enzyme immunoassay for antibody to HIV has been developed and tested with a panel of positive and negative sera. It has proved to be of equal or greater sensitivity compared with a commercial ELISA kit, is simple and quick to perform, requires neither sophisticated equipment nor highly trained technical staff. The reagents are stable enough for postal distribution in tropical countries and, other than for the antigen, the costs are low, making it an appropriate test for use in the developing world when funds for expensive commercial kits are not available.

Syncytium-inducing and non-syncytium-inducing capacity of human immunodeficiency virus type 1 subtypes other than B: phenotypic and genotypic characteristics. WHO Network for HIV Isolation and Characterization.

Positively charged amino acid substitutions at positions 11 and 25 within the loop of the third variable region (V3) of HIV-1 subtype B envelope have been shown to be associated with the syncytium-inducing (SI) phenotype of the virus. The present study was designed to examine SI and NSI-associated V3 mutations in HIV-1 subtypes other than B. HIV-1 RNA was isolated from 53 virus stocks and 26 homologous plasma samples from 53 recently infected individuals from Brazil, Rwanda, Thailand, and Uganda. The C2-V3 region of the viral envelope was converted to cDNA, amplified, and sequenced. Of 53 primary virus stock samples 49 were biologically phenotyped through measurement of the syncytium-inducing capacity in MT-2 cells (to differentiate between SI and NSI phenotypes). In addition, after passage of primary isolates through PHA stimulated donor PBMC, the replication capacity was determined in U937-2, CEM, MT-2, and Jurkat-tat cell lines (to differentiate rapid/high and slow/low phenotypes). According to the sequence analysis 9 (17.0%) of the viruses belonged to subtype A, 15 (28.3%) to subtype B, 1 (1.9%) to subtype C, 13 (24.5%) to subtype D, and 15 (28.3%) to subtype E. Sequence analysis of virus RNA, obtained from 26 homologous plasma samples, confirmed the homogeneity of sequence populations in plasma compared to primary virus isolates. Of the 49 viruses tested 12 had the SI phenotype, 5 were confirmed to be rapid/high, and 4 appeared to be slow/low pattern 3 replicating. Of 49, 29 had the NSI phenotype, 24 were confirmed to be slow/low pattern 1 or 2, and 3 appeared to be slow/low pattern 3 replicating. Analysis of mutations at V3 loop amino acid positions 11 and 25 revealed that 10/12 (83.3%) of the SI viruses had SI-associated V3 mutations and that 28/29 (96.6%) of the NSI viruses lacked these mutations. V3 loop heterogeneity, length polymorphism, and a high number of positively charged amino acid substitutions were most frequently found among subtype D variants. These results indicate that both the phenotypic distinction between SI and NSI viruses and the association of biological phenotype with V3 mutations is present among HIV-1 subtypes other than B.

Standard conditions of virus isolation reveal biological variability of HIV type 1 in different regions of the world. WHO Network for HIV Isolation and Characterization.

HIV-1 isolates were obtained from four countries within the framework of the WHO Network for HIV Isolation and Characterization. The use of standard HIV isolation procedures allowed us to compare the biological properties of 126 HIV-1 isolates spanning five genetic subtypes. In primary isolation cultures, viruses from Uganda and Brazil appeared early and replicated without delay, whereas the replication of Thai viruses was delayed by several weeks. Regardless of genetic subtype or country of origin, blood samples collected more than 2 years after seroconversion yielded virus that replicated efficiently in the primary isolation cultures. None of the isolates obtained from Thailand or Rwanda replicated in cell lines, whereas 5 of the 13 Brazilian isolates and 7 of the 11 Ugandan isolates replicated and induced syncytia in MT-2 cells. As expected for virus isolates obtained early in HIV-1 infection (within 2 years of seroconversion), all viruses from Brazil, Rwanda, and Thailand showed a slow/low replicative pattern. For the Ugandan samples, the time from seroconversion was known precisely for a few of the samples and only in one case was less than 2 years. This may explain why the five viruses that were able to replicate in all cell lines, and thus classified as rapid/high, were of Ugandan origin. Viruses able to induce syncytia in MT-2 cells, also induced syncytia in PBMC. However, 8 slow/low viruses (out of 27) gave discordant results, inducing syncytia in PBMC but not in MT-2 cells. Furthermore, using syncytium induction as a marker, changes in virus populations during early in vitro passage in PBMC could be observed.(ABSTRACT TRUNCATED AT 250 WORDS)

Genetic and antigenic variability of HIV type 1 in Brazil.

Six Brazilian strains of human immunodeficiency virus type 1 (HIV-1) were isolated from infected individuals residing in different regions of Brazil between 1987 and 1989. Phylogenetic analysis based on an 860-base pair env fragment, including V3, V4, V5, and the beginning of gp41, classified the Brazilian strains significantly in genotype B, with interhost distances between 5.9 and 13.1% (mean value, 10%). Amino acid sequence analysis of the V3 loop revealed that three strains contained the North American/European GPGR motif as the tip of the loop whereas in the other three strains proline (P) was substituted by tryptophan (W), methionine (M), or phenylalanine (F). A consensus peptide, Bra-cons, was designed containing GWGR as the tip of the loop. Serological reactivity to the Bra-cons peptide and other V3 peptides (MN, SF2, HBX2, RF, MAL, ELI, Z6, and a Côte d'Ivoire peptide, CI-cons) was compared for 114 HIV-1-positive sera from Rio de Janeiro. Sixty-nine sera (60.5%) reacted with peptides belonging to genotype B, of which 10 sera also reacted with peptides belonging to genotype A (n = 7) and D (n = 3). Eighteen sera (15.8%) had binding antibodies to the Bra-cons peptide. A high number of sera (n = 43; 37.7%) had no antibodies to any of the V3 peptides tested. This result suggests that HIV-1 variants with aberrant V3 loops may circulate in Rio de Janeiro.

Biological characterization and chemokine receptor usage of HIV type 1 isolates prevalent in Brazil.

The human immunodeficiency virus type 1 (HIV-1), the etiological agent of the acquired immunodeficiency syndrome (AIDS), shows a variety of biological properties, which may constitute an obstacle to development of effective vaccines or antiretroviral therapy. To characterize Brazilian strains of HIV-1, we studied 24 viruses isolated from blood samples of HIV-1-positive patients from different regions of the country. To examine the cell tropism and the virus ability to form syncytia, primary macrophages and the CD4+ T cell line MT-2 were infected with these viruses. We found that 22 isolates replicated well in macrophages (macrophage-tropic isolates), 2 infected only MT-2 cells (T cell line tropic variants), while 6 of them grew in both cells. We found 8 syncytium-inducing (SI) and 16 non-SI (NSI) isolates. Continuous cultures of 18 isolates were established in the CCR5+/CXCR4+ cell line PM-1, and SI/NSI features of these viruses were confirmed by cell fusion assay with uninfected CD4+ T cell lines (PM-1, MT-2, H9, and SUP-T1). The coreceptor usage of 18 isolates was investigated by infecting U87 cells transfected with CD4 and chemokine receptors, and we found that 11 isolates infected only CCR5+ cells, 3 only CXCR4+ cells, whereas 4 used both coreceptors. We also observed that X4 isolates were more sensitive to neutralization by dextran sulfate than R5 or R5X4 viruses. Our findings show that the Brazilian isolates are phenotypically similar to those prevalent in other regions, which could mean that therapeutic strategies based on HIV-1 phenotypic properties would be efficient in Brazil, as in other countries.

V3 region polymorphisms in HIV-1 from Brazil: prevalence of subtype B strains divergent from North American/European prototype and detection of subtype F.

Viral DNA sequences were determined over the V3 region of env from 28 infected individuals living in the high HIV-1 prevalence Brazilian cities of Rio de Janeiro and São Paulo. Twenty-six belonged to envelope sequence subtype B, prevalent in North America and Europe, and one was classified as subtype F, found recently in Brazil and in Romania (one appeared to be a B/F recombinant). Octameric sequences at the tip of the subtype B V3 loops were variable and distinct from those prevalent in North America and Europe. The GPGR motif, prevalent in North American/European strains, was found in only 8 (28.5%) sequences, whereas GWGR was found in 12 (43%) and novel sequences in 8 (28.5%). Brazilian subtype B sequences also diverged from the consensus North American/European strains over the remainder of the V3 loop. These results suggest that Brazilian HIV-1 B strains may have important antigenic differences from prototype subtype B strains currently being evaluated for use in HIV vaccines. These results should be taken into account for future vaccine programs in Brazil.

Retrovirus infections in a sample of injecting drug users in Rio de Janeiro City, Brazil: prevalence of HIV-1 subtypes, and co-infection with HTLV-I/II.

BACKGROUND: Retrovirus infections among injecting drug users (IDUs), a core at-risk population for both HIV-1 and HTLV-I/II infections in Brazil, were assessed within an ongoing cooperative research. OBJECTIVE: The study assessed the seroprevalences of HIV-1 and HTLV-I/II infections, as well as the prevalence of HIV-1 subtypes in a sample of IDUs from Rio de Janeiro, Brazil. An attempt to evaluate HIV incidence was carried out using a dual 'sensitive/less sensitive' testing strategy. STUDY DESIGN: Cross-sectional evaluation of 175 IDUs. Serostatus for HIV-1 and HTLV-I/II were established by enzyme-linked immunosorbent assays, and confirmed by western blot. The dual testing strategy aimed to estimate HIV-1 incidence rates. Differentiation between HTLV-I and -II was performed by western blot. DNA samples were polymerase chain reaction amplified by a nested protocol, and HIV-1 subtyping was determined by heteroduplex mobility assay. RESULTS: Forty-six and 29 samples were found to be, respectively, positive for HIV-1 and HTLV-I/II, 15 of them co-infected by both viruses. Among HTLV-I/II-infected patients, 75.9% were infected by HTLV-I. Thirty-one HIV samples were identified as B subtype, with seven of them showing the typical "Brazilian B" pattern in the gp120 V3 loop, and ten were identified as F subtype. The use of less sensitive assays for HIV infection wrongly identified a deeply immunocompromised patient as an incident case. CONCLUSION: Moderately high seroprevalences were found for both HIV-1 and HTLV-I/II infections, HIV-1/HTLV-I co-infections being of special concern. A non-statistically significant higher prevalence of F subtype was observed, when compared with the distribution of F/B subtypes among Brazilian patients from other exposure categories. No recent HIV-1 infections were detected, but a limitation of the "sensitive/less-sensitive" testing strategy was made evident.

Human visceral leishmaniasis: analysis of the specificity of humoral immune response to polypeptides of Leishmania donovani chagasi.

Soluble antigens from Leishmania donovani chagasi were studied in terms of their ability to react with sera from human visceral leishmaniasis. Thirty-six polypeptides, with molecular weights ranging from 14,400 to 123,000 were demonstrated by Western blot analysis. An extensive cross-reactivity with sera from patients with cutaneous leishmaniasis and Chagas' disease also was observed. Two polypeptides (Mr 119,000 and 123,000) reacted with all the sera from visceral leishmaniasis patients. When they were electroeluted from gels and evaluated with respect to specificity to the L. donovani chagasi subspecies, these components were expressed in all strains of Leishmania tested, but not in those of Trypanosoma cruzi. These results indicated that these components are shared by Trypanosomatidae of genus Leishmania. The eluted polypeptides did not react with sera from patients with Chagas' disease, indicating the feasibility of using purified antigens to discriminate between the humoral immune responses in T. cruzi and Leishmania infections.

Correlation of circulating immune complexes and complement breakdown products with the severity of the disease in human schistosomiasis mansoni.

Circulating immune complexes and complements compounds were measured in serum and plasma from 66 patients with three different clinical forms of chronic schistosomiasis mansoni: intestinal, hepato-intestinal and hepatosplenic. Three different methods were used: the 125I-C1q-binding assay, conglutinin-binding assay (KgB) and Raji cell-binding assay. Approximately 25% of the patients were positive for circulating immune complexes as measured by the C1q and Raji assays. The levels of complexes increased significantly with the severity of the disease. 60% of the patients were positive for immune complexes as measured by the KgB-assay but the incidence of positive results was not clearly influenced by the stage of the disease. There was no significant correlation between immunoglobulin levels and immune complexes. The complement profile of these patients does not suggest a dramatic activation of the complement system. However, there was a progressive decrease in the plasma levels of C4 and an increase of C3d levels which correlated significantly with the severity of the disease.

Antigenic differences between insect- and culture-derived Trypanosoma cruzi metacyclic trypomastigote extracts.

Antigenic differences between extracts prepared from insect- and axenic cultured-derived T. cruzi were demonstrated by a protein A-binding immunoradiometric assay.

Human T lymphotropic virus type I (HTLV-I) infection in neurological patients in Salvador, Bahia, Brazil.

HTLV-I infection represents a major health concern in endemic areas throughout the world, such as Salvador, the main city of Bahia State, with socio-demographic characteristics similar to sub-Saharan African cities, located in the Northeast of Brazil. In order to provide an estimate of the frequency distribution, and range of neurological manifestations potentially related to HTLV-I infection in this city, we conducted a cross-sectional clinical-epidemiological study to determine the prevalence of this infection in patients with neurological diseases. Patients exhibiting vascular diseases, tumoral diseases or trauma were excluded. Over a period of 16 months, we studied 322 consecutive patients with chronic neurological diseases, who attended the neurological clinics of two major hospitals in Salvador. Overall, the prevalence of HTLV-I infection among the patients was 20.9% (67/320). However, the prevalence among the 104 patients with chronic myelopathy was 50.0% (52/104). It was observed that the major prevalence of HTLV-I was between the ages of 40 and 60 years with a female predominance. Our data indicate that, in Salvador city, HTLV-I is associated with chronic myelopathies or myeloneuropathies, which seem to be the only neurological diseases associated with HTLV-I.

Can malaria-associated polyclonal B-lymphocyte activation interfere with the development of anti-sporozoite specific immunity?

To study the relevance of polyclonal B cell activation (PBA) associated with malaria in the development of specific anti-sporozoite immunity, we used a reverse haemolytic plaque assay and an immunoradiometric assay employing the synthetic peptide (NANP)3, the main epitope of the circumsporozoite (CS) protein of Plasmodium falciparum, to assess respectively the degree of activation of IgG and IgM secreting cells and the level of anti-sporozoite antibodies in 95 subjects with malaria and 21 non-infected individuals. A positive correlation was observed between the anti-(NANP)3 antibody levels and the number of past attacks of malaria but not between the former and the age of individuals or the number of months of residence in the endemic region. Individuals with high numbers of IgG or IgM secreting cells (SC) had lower levels of anti-(NANP)3 antibodies; those with levels of antibodies above the mean for malaria-infected individuals had lower numbers of IgGSC and higher haematocrit and haemoglobin values. These data show the existence of a negative relationship between malaria-induced PBA and anti-sporozoite immunity, and it is suggested that either PBA blocks the development of anti-sporozoite immunity or, alternatively, the latter protects individuals against malaria and malaria-associated PBA.

Trypanosoma cruzi strain-specific monoclonal antibodies: identification of Colombian strain flagellates in the insect vector.

Spleen cells from mice immunized with insect-derived Trypanosoma cruzi metacyclic trypomastigotes were used to obtain Colombian strain-specific monoclonal antibodies. At least 4 different strain-specific antigens were recognized by the monoclonal antibodies on epimastigotes or metacyclic trypomastigotes. There was no reactivity with other stages of Colombian strain T. cruzi, nor with any stage of 15 other T. cruzi strains or isolates, nor with 22 other Trypanosomatidae. One of the monoclonal antibodies was used to identify, by indirect immunofluorescence, Colombian strain flagellates in cryostat sections or glass-slide smears of the insect vector's intestine.

Analysis of antibody specificity against the third variable region of the envelope glycoprotein gp120 of HIV-1 in plasma from HIV-1-positive individuals residing in Brazil.

1. Antibody specificity for the principal neutralization domain (PND) of the human immunodeficiency virus type 1 (HIV-1) was studied in plasma from 122 HIV-1-infected individuals residing in Brazil. 2. Using 8 overlapping sequential pentadecapeptides corresponding to the third variable region (V3) of 5 different HIV-1 isolates in an enzyme-linked immunosorbent assay (ELISA), a preferential recognition of the peptides with amino acid sequences corresponding to the HIV-1 isolates IIIB and MN (maximal reactivities of 60-70%) compared to the isolates SC, WMJ-2 or RF (maximal reactivities below 60%) was observed. 3. A difference was observed in the overall reactivity pattern to HIV-1 SC peptides of plasma collected from individuals residing in the Brazilian states of Rio de Janeiro and Bahia. However, a statistically significant increased recognition by Bahian plasma was only observed for the HIV-1 SC C55 peptide. 4. The mean CD4/CD8 ratio of the group of plasma with an isolate-restricted recognition of peptides (0.522 +/- 0.074) was significantly lower than that of the total group of plasma (1.00 +/- 0.18).