Safe and prolonged survival with long-term exposure to pomalidomide in relapsed/refractory myeloma.

BACKGROUND: The IFM2009-02 trial studied pomalidomide (4 mg daily, 21/28 versus 28/28) and dexamethasone in very advanced relapsed or refractory multiple myeloma (RRMM). We observed that 40% of patients had a prolonged progression-free survival (PFS) and subsequently overall survival (OS). We sought to analyze the characteristics of these patients and study the effect of long exposure to pomalidomide. DESIGN: We separated the studied population into two groups: 3 months to 1 year (<1 year) and more than 1 year (≥1 year) of treatment with pomalidomide and dexamethasone based on clinical judgment and historical control studies. We then analyzed the characteristics of patients according to duration of treatment. RESULTS: The overall response rate (ORR) for the <1-year group was 43%, the median PFS 4.6 months [95% confidence interval (95% CI) 3.8-6.4] with only 6% at 12 months, and the median OS was 15 months (11.7-20.3) and 40% at 18 months. For the ≥1-year group, the response rate and survival were strikingly different, ORR at 83%, median PFS 20.7 months (14.7-35.4), median OS not reached, and 91% at 18 months. CONCLUSION: Pomalidomide and dexamethasone favored prolonged and safe exposure to treatment in 40% of heavily treated and end-stage RRMM, a paradigm shift in the natural history of RRMM characterized with a succession of shorter disease-free intervals and ultimately shorter survival. Although an optimization of pomalidomide-dexamethasone regimen is warranted in advanced RRMM, we claim that pomalidomide has proven once more to change the natural history of myeloma in this series, which should be confirmed in a larger study.

Circulating tumor cells in locally advanced pancreatic adenocarcinoma: the ancillary CirCe 07 study to the LAP 07 trial.

BACKGROUND: Pancreatic carcinoma is one of the leading causes of cancer-related mortality. At the time of diagnosis, 30% of patients present with a locally advanced pancreatic carcinoma (LAPC). As circulating tumor cells (CTCs) count may be a surrogate of the cancer metastatic abilities, CTC detection rates and prognostic value were studied in a prospective cohort of LAPC patients. PATIENTS AND METHODS: An LAP07 international multicenter randomized study assesses in patients whose LAPC is controlled after 4 months of chemotherapy whether chemoradiotherapy could increase survival versus continuation of chemotherapy. A subgroup of patients included in the LAP07 trial was screened for CTCs (CellSearch®) before the start of the chemotherapy and after 2 months of treatment. Patient characteristics and survival were obtained prospectively and were correlated with CTC detection. RESULTS: Seventy-nine patients were included. One or more CTCs/7.5 ml were detected in 5% of patients before treatment and in 9% of patients after 2 months of treatment (overall detection rate: 11% of patients). CTC positivity was associated with poor tumor differentiation (P = 0.04), and with shorter overall survival (OS) in multivariable analysis (RR = 2.5, P = 0.01), together with anemia. CONCLUSIONS: The evaluation of micrometastatic disease using CTC detection appears as a promising prognostic tool in LAPC patients.

High independent prognostic and predictive value of circulating tumor cells compared with serum tumor markers in a large prospective trial in first-line chemotherapy for metastatic breast cancer patients.

BACKGROUND: Circulating tumor cells (CTCs) are a prognostic marker in metastatic breast cancer, but comparisons with serum tumor markers (CA 15-3, carcinoembryonic antigen and lactate dehydrogenase) variations are needed. PATIENTS AND METHODS: CTCs were counted with CellSearch® at baseline, before cycle 2 (C2) and cycle 3 or 4 (C3/4) in 267 metastatic breast cancer patients on first-line chemotherapy with/without targeted therapy. RESULTS: Baseline CTC detection rate was 65% with ≥1 CTC/7.5 ml threshold and 44% with ≥5 CTC/7.5 ml and was independent of subtypes (luminal, triple negative, human epithelial growth factor receptor 2 (HER2)+). CTCs were associated with tumor markers, bone/liver involvement, tumor burden and performance status. CTC detection ≥1 CTC/7.5 ml was a strong prognostic factor for progression-free survival (PFS), P < 0.0001. Threshold of CTC ≥5 was statistically significant for PFS and overall survival (OS), P = 0.03 on multivariate analysis. Among patients with ≥5 CTC/7.5 ml at baseline, 50% had <5 CTC/7.5 ml at C2. Changes were correlated with both PFS and OS (P < 0.0001). All patients receiving anti-HER2 therapy had <5 CTC/7.5 ml after three cycles of treatment. CONCLUSION: This is the largest prospective series validating the prognostic value of CTC independently from serum tumor marker. Elevated CTCs before C2 are an early predictive marker of poor PFS and OS, which could be used to monitor treatment benefit. CTC decrease under treatment seems stronger with targeted therapy.

Single circulating tumor cell detection and overall survival in nonmetastatic breast cancer.

BACKGROUND: Circulation of cancer cells in the blood is a mandatory step for metastasis, but circulating tumor cells (CTC) have a low metastatic efficiency in preclinical animal models. In this prospective study, we reported the clinical outcome of nonmetastatic breast cancer patients according to CTC detection. PATIENTS AND METHODS: In 115 nonmetastatic patients diagnosed with large operable or locally advanced breast cancer, we prospectively detected CTC using the CellSearch system before and after neoadjuvant chemotherapy in a phase II trial (REMAGUS02). RESULTS: At baseline, 23% of patients were CTC positive, but only 10% had >1 CTC/7.5 ml of blood. After a median follow-up of 36 months, CTC detection before chemotherapy was an independent prognostic factor for both distant metastasis-free survival [DMFS; P = 0.01, relative risk (RR) = 5.0, 95% confidence interval (CI) 1.4-17] and overall survival (OS; P = 0.007, RR = 9, 95% CI 1.8-45). CTC detection after chemotherapy was of less significance (P = 0.07 and 0.09, respectively). Moreover, CTC detection showed interesting characteristics as an individual predictive test for metastatic relapses (sensibility 55%, specificity 81%, and global accuracy 77%). CONCLUSIONS: Detection of > or =1 CTC/7.5 ml before neoadjuvant chemotherapy can accurately predict OS. Our findings may change the clinical management of nonmetastatic breast cancer and indicate that the metastatic efficiency of CTC could be higher than previously reported.

Clinical value of circulating endothelial cells and circulating tumor cells in metastatic breast cancer patients treated first line with bevacizumab and chemotherapy.

BACKGROUND: We investigated whether circulating tumor cells (CTCs) and circulating endothelial cells (CECs) predict clinical outcome of first-line chemotherapy combined with bevacizumab in metastatic breast cancer patients. PATIENTS AND METHODS: In a French substudy of the MO19391 trial, CTC and CEC counts (CellSearch system) at baseline and changes after two cycles of treatment were correlated with time to progression (TtP). RESULTS: CTC and CEC levels were not correlated in the 67 patients included. At baseline, CTC positivity was a significant prognostic marker for TtP at a threshold of 3 CTC/7.5 ml (P < 0.05) but not at 5 CTC/7.5 ml (P = 0.09). Baseline CEC levels (median 17 CEC/4 ml, range 1-769) were associated with age > or =45 years (P = 0.01), elevated lactate dehydrogenase (P < 0.01) and not with TtP at any threshold. Changes of CTC count during treatment were not a surrogate of TtP, with any of the model tested (threshold based or relative decrease in percent). However, increase in CEC count was associated with improved TtP, at the threshold of 20 CEC/4 ml (P < 0.01). CONCLUSION: Bevacizumab combined with first-line chemotherapy may modify the predictive value of CTC during treatment possibly due to impaired tumor cells intravasation through vessels endothelium. Variations in CEC levels appear to be a promising early surrogate marker of TtP under antiangiogenic treatment.

Prognosis of women with stage IV breast cancer depends on detection of circulating tumor cells rather than disseminated tumor cells.

BACKGROUND: At metastatic relapse, detection of circulating tumor cells (CTC) in peripheral blood is predictive of poor survival of breast cancer patients. Detection of disseminated tumor cells (DTC) in bone marrow (BM) is an independent prognostic factor in early breast cancer. We evaluated the prognostic value of DTC detection in the BM of metastatic breast cancer patients. MATERIALS AND METHODS: BM aspirates from 138 patients were screened for DTC with the pancytokeratin mAb A45-B/B3, according to the ISHAGE classification. One hundred and ten patients (80%) were enrolled before first-line treatment. Thirty-seven patients were simultaneously screened for CTC in the blood. RESULTS: DTC detection rate in the BM was 59%. DTC were associated with bone metastasis (P = 0.0001), but not with a poorer overall survival. Adverse significant prognostic factors were hormone receptor negativity (P = 0.0004) and more than one line of chemotherapy (P = 0.002). CTC detection in the subgroup of 37 metastatic patients was associated with shorter survival (P = 0.01). CONCLUSIONS: Detection of CTC but not BM DTC had a prognostic significance in stage IV breast cancer patients. CTC in blood are a more reliable and a less invasive tool to evaluate prognostic and monitor tumor response in this metastatic setting.

Heterogeneity of t(4;14) in multiple myeloma. Long-term follow-up of 100 cases treated with tandem transplantation in IFM99 trials.

One hundred de novo multiple myeloma patients with t(4;14) treated with double intensive therapy according to IFM99 protocols were retrospectively analyzed. The median overall survival (OS) and event-free survival (EFS) were 41.4 and 21 months, respectively, as compared to 65 and 37 for patients included in the IFM99 trials without t(4;14) (P<10(-7)). We identified a subgroup of patients presenting at diagnosis with both low beta(2)-microglobulin <4 mg/l and high hemoglobin (Hb) >/=10 g/l (46% of the cases) with a median OS of 54.6 months and a median EFS of 26 months, respectively, which benefits from high-dose therapy (HDT); conversely patients with one or both adverse prognostic factor (high beta(2)-microglobulin and/or low Hb) had a poor outcome. The achievement of either complete response or very good partial response after HDT was also a powerful independent prognostic factor for both OS and EFS.

Predictors of clinical response to interleukin-2--based immunotherapy in melanoma patients: a French multiinstitutional study.

PURPOSE: Various parameters have been reported to be correlated with response to interleukin-2 (IL-2) therapy. A multiinstitutional study was performed to assess by multivariate analysis the predictive value of known clinical and biologic melanoma prognostic markers recorded before the onset of IL-2 therapy on the likelihood of objective clinical response. PATIENTS AND METHODS: Serum C-reactive protein (CRP), IL-6, and lactate dehydrogenase (LDH) levels were measured in 81 metastatic melanoma patients included in different IL-2-based regimens before the starting of IL-2-therapy. Clinically defined prognostic groups, i.e., patients with superficial or visceral metastases, were also analyzed for response correlates. Patients were evaluated for response to treatment 4 to 6 weeks after completion of one course of therapy. RESULTS: On univariate analysis, the pretreatment values of CRP (P = .001), IL-6 (P = .007), and LDH (P = .02) and site of metastases (P = .0004) were correlated with clinical response. However, only CRP (P < .007) and clinically defined group (P < .004) were independent predictors on multifactorial analysis. Indeed, when adjusted to CRP, IL-6 tended to improve patient selection, but did not reach statistical significance (P = .07). Furthermore, using multivariate survival analysis based on the Cox proportional hazards model, only CRP was found to be an independent prognostic factor for survival (P < .0001). CONCLUSION: In this study, patients with high serum levels of CRP and/or visceral organ involvement before therapy were unlikely to respond to IL-2 therapy. Therefore, clinical classification based on the site of metastases and serum CRP determination before the start of IL-2 therapy may help to improve selection of melanoma patients who may benefit from IL-2 and could prevent unnecessary morbidity.

Production of matrix metalloproteinase-9 in early stage B-CLL: suppression by interferons.

Besides vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF), matrix metalloproteinases (MMPs) play critical roles in angiogenesis, tumor invasion and metastasis. Increased angiogenesis is observed in chronic B lymphocytic leukemia (B-CLL) and published data reported VEGF and bFGF production in this disease. The purpose of this study was to investigate MMP expression in early stage B-CLL. Elevated MMP-9 concentrations were detected by ELISA in the sera of B-CLL patients (median level 250 ng/ml) compared with healthy donors (67 ng/ml) (P < 0.0001), and immunostaining with antibodies against MMP-9 and B cell antigens (CD19, CD23) substantiated the presence of MMP-9 in tumoral B lymphocytes. By using RT-PCR, ELISA and zymography experiments, we confirmed that B-CLL cells expressed and released the pro-form of MMP-9 with Mr 92 kDa (158-1300 pg/ml/10(6) cells/48 h), p-aminophenylmercuric acetate generating a 82 kDa active form. In contrast, the production of MMP-9 by normal counterpart B cells was significantly low (28-169 pg/ml/10(6)cells/48 h). Moreover, B-CLL culture supernatants contained bFGF (median levels 17 pg/ml/10(6) cells/48 h), VEGF (1.4 pg/ml/10(6) cells/48 h) and TNF-alpha (0.2 pg/ml/10(6) cells/48 h). TNF-alpha and VEGF antibodies blocked MMP-9 at the mRNA and protein levels. Interferons (IFNs) type I or type II repressed MMP-9 gelatinolytic activity in a dose and time dependency, and this was reflected by a parallel inhibition of MMP-9 mRNA and protein. IFNs however did not affect the production of bFGF, VEGF and TNF-alpha. Together, our data show that B-CLL lymphocytes synthesize MMP-9 and emphasize the specific inhibitory actions of IFNs on its expression.

Proliferative response of hairy cells to B cell growth factor (BCGF): in vivo inhibition by interferon-alpha and in vitro effects of interferon-alpha, -beta, and -gamma.

Hairy cell leukemia (HCL) is a pre-plasma B cell tumor which responds to interferon (IFN)-alpha therapy. In vitro, B cell growth factor (BCGF) can induce proliferation of hairy cells. We have investigated the effect of in vitro and in vivo treatments with different recombinant IFN on the capacity of hairy cells to proliferate in response to human BCGF. In vitro treatment of leukemic cells from HCL patients with recombinant IFN-alpha-2 (5/5 cases) or IFN-beta (4/5 cases) resulted in a marked inhibition of the BCGF-dependent response. This suppressive effect was obtained with IFN concentrations of 1000, 100 IU/ml, and even occasionally 10 IU/ml. In contrast, no such inhibition was observed with IFN-gamma, despite the presence of specific IFN-gamma receptors on hairy cells at densities similar to receptors for IFN-alpha/beta. The IFN-alpha-induced suppression of the proliferative response of hairy cells to BCGF was also observed in vivo in two patients within 6-12 hr after administration of single doses of IFN-alpha. When hairy cells were maintained in culture for 1 week, they recovered their capacity to be stimulated by BCGF. This reversion was also shown in vivo in hairy cells isolated 1 week after IFN administration. Since in vivo growth of hairy cells could possibly result from the autocrine secretion of BCGF, we propose that the therapeutic effect of IFN-alpha on HCL may be due in part to an inhibition of such autocrine loop.

Soluble Fc gamma receptors.

Soluble Fc gamma receptors have been identified in biological fluids of mice and humans. They are produced either by alternative splicing of the exon encoding the transmembrane region of the receptor (Fc gamma RII) or by proteolytic cleavage at the cell membrane (Fc gamma RII and Fc gamma RIII). They inhibit B cell proliferation and immunoglobulin production. Their concentrations in plasma seem to be modified during the development of certain diseases, as for instance in multiple myeloma, where plasma concentrations of soluble Fc gamma RIII are correlated with the stage of the disease.

Regulatory effects of IgG-BF on hybridoma B cells. molecular characterization of variant cell lines.

Immunoglobulin G-binding factors (IgG-BF) produced by mouse T cells or hybridoma T cells (T2D4) were used to manipulate in vitro mouse hybridoma B cells. Both IgG production by, and proliferation of, these cells was inhibited by IgG-BF, or during co-cultures with IgG-BF-producing T2D4 cells. Thus, treatment of tumor B cells, besides its potential therapeutic use, represents an invaluable model for studying the regulation of Ig production by IgG-BF at a molecular level. To further analyze the molecular events induced by IgG-BF in B cell hybridomas, a set of variant clones of a hybridoma cell line (UN2) was isolated and variants were characterized for their Ig production and their Fc gamma R expression.

In vitro inhibition of tumor B cell growth by IgG-BF-producing Fc gamma RII+ T cell hybridoma and by immunoglobulin G-binding factors.

The growth-modulating effect on mouse hybridoma B cells of IgG-BF-producing Fc gamma RII+ mouse T cell hybridomas and of the IgG-BF isolated from the culture supernatants of these cells has been examined. Cocultures of IgG-secreting hybridoma B cells with IgG-BF-producing T hybridomas or with partially purified IgG-BF demonstrated a reproducible inhibition of the tumor B cell growth. The inhibition was due to a cytostatic and not to a cytotoxic effect. Hybridoma B cells cultured in liquid medium in the presence of soluble IgG-BF, or cocultured in semisolid agarose assays with IgG-BF-producing hybridoma T cells did not undergo immediate cytolysis but were prevented from proliferating. Thus, our data indicate that IgG-BF-producing Fc gamma RII+ T cells interfere with the proliferation of transformed B cells, possibly through soluble IgG-BF.

Phenotypic and functional analysis of tumour-infiltrating lymphocytes from patients with melanoma and other metastatic cancers.

Thirty tumour specimens, among which were 17 melanomas, were cultured with recombinant interleukin-2 (IL-2) in order to produce tumour-infiltrating lymphocytes (TIL). In the melanomas, three categories of TIL were characterised. The first, containing mostly CD3+ and CD8+ cells, lysed only autologous tumour cells; the second, containing mostly CD3+ and CD4+ cells, lysed both autologous tumour cells and allogeneic cells lines; the third, with mixed phenotype although cytotoxic for K562 targets, did not kill melanoma cells. The optimal conditions for a good development of TIL were established: we found that the lymph node or cutaneous origin of the tumour was unimportant, a 2 h enzymatic treatment was optimum and that TIL grew well in AIM V serum free medium. Therefore the easiness and the reproducibility of the TIL cultures from melanoma tumour samples allows the rapid development of therapeutic trials in metastatic melanoma.

Multicolor flow cytometry analysis of blood cell subsets in patients given total body irradiation before bone marrow transplantation.

PURPOSE: Bone marrow transplantation has often been closely linked with accidental or intentional therapeutical irradiation. In both situations, study of the radiosensitivity of human blood cell subsets is of interest. Using one-color flow cytometry analysis of B lymphocytes, T cell subsets, and natural killer cells, we previously reported that lymphocyte subsets exhibit equal radiosensitivity. Taking advantage of recent developments in the knowledge of leukocyte differentiation antigens and flow cytometry technology we undertook a study of blood cell subsets to search for rare populations exhibiting different radiosensitivity. METHODS AND MATERIALS: Thirty patients, who were delivered a 12 Gy fractionated total body irradiation as part of their conditioning regimen before transplantation for malignant disorders, were studied using multicolor flow cytometry. RESULTS: T and B lymphocytes showed a sharp, radiation-induced decrease, with the B lymphocytes (cluster of differentiation (CD) 19+) being the most sensitive. When analyzed by multicolor flow cytometry, all major lymphocyte subsets appeared equally sensitive to the in vivo irradiation; that is, CD3+4+45RO+, CD3+4+45RA+, CD3+4+8-, CD3+4-8+. Therefore, all major lymphocyte subsets sharing the helper phenotype (naive or memory) and the cytotoxic phenotype appeared equally sensitive to in vivo whole body irradiation. In parallel, the CD34+ cell subset remained basically unchanged after whole body irradiation. Finally, the CD3-, 56+, 16+ natural killer cell subset was relatively radioresistant (91 and 74% of its initial value, after 2 and 4 Gy, respectively) as compared to other lymphocyte subsets. CONCLUSION: Our study provides evidence that T and B cell subsets seem to be highly radiosensitive in vivo. The CD34+ progenitor/stem cells and NK cells seem to be more radioresistant. This latter result might provide clues to the understanding of the pathophysiogeny of radiation-induced aplasia and of the engrafment/rejection process following bone marrow transplantation.

Prognostic value of cytokine and soluble Fc gamma receptor assays in oncology.

The clinical course of a cancer is influenced by the interaction of tumour cells with the patient's immune system. It is thus conceivable that immunological parameters may be used as markers of prognostic or predictive value. We report here that increased serum levels of IL-6 is a signal of poor prognosis and predicts unresponsiveness to immunotherapy in patients with metastatic melanoma. In cervical cancer, IL-6 produced by infiltrating macrophages is a marker of invasive cancer. In patients with multiple myeloma, the plasmatic levels of soluble Fc gamma receptors are markers of the disease, sCD16 being drastically decreased and sCD32 being slightly increased.

Regulation of production of soluble Fc gamma receptors type III in normal and pathological conditions.

CD16 (Fc gamma R type III), a low affinity IgG Fc receptor, is found in two forms, a transmembrane Fc gamma RIIIa expressed by NK cells and monocytes and a phosphatidylinositol-linked Fc gamma RIIIb present on neutrophils. Exposure of neutrophils to inflammatory signals induces a rapid loss of CD16 expression and release of a soluble form of CD16 (sCD16). Soluble CD16 circulates in plasma, levels being reduced in sera from patients with multiple myeloma. In the present manuscript the authors summarize work that aimed to better understand: (i) the role of proteinases in sCD16 production and CD16 membrane shedding; and (ii) the regulation of sCD16 levels in multiple myeloma patients and the possible biological consequences of its decrease in this disease. Soluble CD16 was purified from human serum. Its N-terminal sequencing demonstrated that it originates from neutrophil CD16 and its C-terminal sequencing showed that the cleavage site was between Val 196 and Ser 197, close to the membrane anchor. Analysis of the effect of protease inhibitors revealed that the cleavage leading to sCD16 production by PMA-activated neutrophils was metalloproteinase-dependent. In addition, membrane and sCD16 were sensitive to serine proteinases released by azurophil granules or added under purified form. The reduction of sCD16 levels that occurs in patients with multiple myeloma was associated with a slight decrease in circulating neutrophils, but not with a significant defect in sCD16 production by neutrophils, as detected in vitro. Moreover, addition of a recombinant sCD16 to plasmocytoma lines did not significantly modify their proliferation and Ig secretion.

Diversity of V3 region sequences of human immunodeficiency viruses type 1 from the central African Republic.

Nucleotide sequences of the central portion of gp120, including the third hypervariable (V3) loop, were obtained from lymphocytes cocultivated with SupT1 cells from 29 AIDS patients in Bangui, Central African Republic. These sequences displayed significantly greater diversity (average distance, 23%) than has been previously observed in isolates from comparably restricted geographical areas. Isolates belonging to four major subtypes of HIV-1 were found; the only subtype not represented was the North American/European subtype B. Unlike the situation in Zaire and Uganda, where subtypes A and D account equally for virtually all isolates of HIV-1, the predominant subtypes in the Central African Republic, accounting for two-thirds of the isolates, were subtypes A (10 isolates) and E (9 isolates). Subtype E represents a group of variants that have previously been found only in Thailand. Only one isolate belonging to subtype D was found. Also recovered were two isolates of subtype C, a subtype associated with southern African and Indian isolates but not previously detected in central Africa. These isolates, although clearly clustering with subtype C, formed a distinct subset, differing from one another by 8.8% and from the Indian and South African subtype C isolates by an average of 22.5%. High interpatient, intrasubtype variation was also seen among the CAR subtype A (average pairwise difference, 19.3%) and subtype E (10.9%) isolates. The diversity of V3 sequences in this set has implications for immunization protocols that rely on the recognition of V3. This study underscores the necessity of basing intervention strategies on knowledge of the particular sequences present in the target population or geographical area.

Diversity of antibody binding to V3 peptides representing consensus sequences of HIV type 1 genotypes A to E: an approach for HIV type 1 serological subtyping.

We investigated whether V3-binding assays might be useful to analyze human immunodeficiency virus type 1 (HIV-1) variants in different geographic regions. We showed that strong cross-reactivity between subtype-specific V3 peptides is almost inevitable in standard indirect enzyme-linked immunosorbent assays (EIA), impairing precise serological subtyping. We therefore developed a subtype-specific EIA (HIV-1 SSEIA) that uses the principle of blocking by an excess of peptide in the liquid phase. Using 231 serum samples collected from HIV-1-infected individuals in 10 different geographical areas from 4 continents, we showed that this approach detected the dominant subtype reactivity in more than 97% of the cases. Internal controls (0 and 100% blocking) were used for every sample such that comparative analysis was possible, independent of both the individual humoral response and the time of collection during the course of infection. This was validated by the excellent concordance of the serological profiles of couples and the temporal stability of the serological profile in individuals. The geographical distribution of the various subtypes in the SSEIA was in agreement with the present knowledge of the distribution of the various genotypes. Although the goal of this study was not an extensive seroepidemiological survey, our results showed that the various profiles in most of the regions were relatively homogeneous, but in central Africa there was a large diversity of serological profiles. Cluster analysis identified a limited number of V3 serogroups of serotypes within the HIV-1 group M. Five serogroups, some of them divided into subgroups, were identified and characterized by a mean serological profile. Our data confirmed that subtypes A and C, although being dissimilar genetic subtypes, present conserved antigenic properties in the V3 region, and that the D subtype is probably the most divergent within the group M (B Korber et al., J Virol 1994;68:6730). Cluster analysis showed a clear correlation between position within the dendrogram and geographical origin of the samples. This is further support for the reliability and thereof the usefulness of the SSEIA. This simple methodology may help facilitate the analysis of the distribution of various HIV-1 subtypes circulating in different populations and regions.