Short communication: neutralizing antibodies in HIV-1-infected Brazilian individuals.

Tests for the detection of the humoral immune response to HIV-1 have to be standardized and established, demanding regional efforts. For this purpose the neutralizing antibody (NAb) assay for HIV-1 in TZM-bl cells was introduced in Brazil. Twenty plasma samples from HIV-1-infected individuals were assayed: 10 progressors and 10 long-term nonprogressors. These were tested against eight env-pseudotyped viruses (psVs) in the TZM-bl NAb assay and against HIV-1 strain HTLV/IIIB (HIV-1 IIIB) in primary lymphocytes. Forty-four percent of the samples showed neutralizing titers for psVs and 55% for HIV-1 IIIB. Plasma from progressors showed a broader neutralization and a higher potency. The introduction of these reference reagents encourages the participation of Brazil in future comparative assessments of anti-HIV-1 antibodies.

International network for comparison of HIV neutralization assays: the NeutNet report II.

BACKGROUND: Neutralizing antibodies provide markers for vaccine-induced protective immunity in many viral infections. By analogy, HIV-1 neutralizing antibodies induced by immunization may well predict vaccine effectiveness. Assessment of neutralizing antibodies is therefore of primary importance, but is hampered by the fact that we do not know which assay(s) can provide measures of protective immunity. An international collaboration (NeutNet) involving 18 different laboratories previously compared different assays using monoclonal antibodies (mAbs) and soluble CD4 (Phase I study). METHODS: In the present study (Phase II), polyclonal reagents were evaluated by 13 laboratories. Each laboratory evaluated nine plasmas against an 8 virus panel representing different genetic subtypes and phenotypes. TriMab, a mixture of three mAbs, was used as a positive control allowing comparison of the results with Phase I in a total of nine different assays. The assays used either uncloned virus produced in peripheral blood mononuclear cells (PBMCs) (Virus Infectivity Assays, VIA), or Env (gp160)-pseudotyped viruses (pseudoviruses, PSV) produced in HEK293T cells from molecular clones or from uncloned virus. Target cells included PBMC and genetically engineered cell lines in either single- or multiple-cycle infection format. Infection was quantified by using a range of assay read-outs including extra- or intra-cellular p24 antigen detection, luciferase, beta-galactosidase or green fluorescent protein (GFP) reporter gene expression. FINDINGS: Using TriMab, results of Phase I and Phase II were generally in agreement for six of the eight viruses tested and confirmed that the PSV assay is more sensitive than PBMC (p = 0.014). Comparisons with the polyclonal reagents showed that sensitivities were dependent on both virus and plasma. CONCLUSIONS: Here we further demonstrate clear differences in assay sensitivities that were dependent on both the neutralizing reagent and the virus. Consistent with the Phase I study, we recommend parallel use of PSV and VIA for vaccine evaluation.

Immune activation and antibody responses in non-progressing elite controller individuals infected with HIV-1.

An extremely rare subset of patients infected with HIV-1 designated as "non-progressing elite controllers" appears to be able to maintain stable CD4(+) T-cell counts and a median plasma viremia below the detection limit of current ultrasensitive assays (<50-80 copies/ml of plasma) for >10 years in the absence of antiretroviral therapy. Lymphocyte subsets (CD4(+), CD8(+)), immune activation markers (HLA-DR(+), CD38(+), Beta-2-microglobulin), and HIV-specific antibody responses were longitudinally examined in four non-progressing elite controllers over more than 5 years. Two control groups of seronegative healthy individuals and untreated patients infected with HIV-1 presenting detectable viremia were also included. None of the non-progressing elite controllers displayed the high T-cell activation levels generally seen in the seropositive individuals, keeping them within the normal range. Three non-progressing elite controllers showed no significant immune system abnormalities when compared to seronegative individuals, displaying a low proportion of HIV-1-specific binding antibodies and low avidity index, similar to those observed for individuals infected recently with HIV-1. One non-progressing elite controller exhibited CD8(+) T-cell counts and beta2-M levels above normal ranges and developed a low but "mature" (high-avidity) HIV-1-specific antibody response. Thus, the non-progressing elite controllers are able to maintain normal T-cell activation levels, which may contribute to prevent, or greatly reduce, the damage of the immune system typically induced by the HIV-1 over time. They are, however, immunologically heterogeneous and very low levels of antigen exposure seem to occur in these patients, sufficient for sustaining a low, but detectable, HIV-1-specific immunity.

International network for comparison of HIV neutralization assays: the NeutNet report.

BACKGROUND: Neutralizing antibody assessments play a central role in human immunodeficiency virus type-1 (HIV-1) vaccine development but it is unclear which assay, or combination of assays, will provide reliable measures of correlates of protection. To address this, an international collaboration (NeutNet) involving 18 independent participants was organized to compare different assays. METHODS: Each laboratory evaluated four neutralizing reagents (TriMab, 447-52D, 4E10, sCD4) at a given range of concentrations against a panel of 11 viruses representing a wide range of genetic subtypes and phenotypes. A total of 16 different assays were compared. The assays utilized either uncloned virus produced in peripheral blood mononuclear cells (PBMCs) (virus infectivity assays, VI assays), or their Env-pseudotyped (gp160) derivatives produced in 293T cells (PSV assays) from molecular clones or uncloned virus. Target cells included PBMC and genetically-engineered cell lines in either a single- or multiple-cycle infection format. Infection was quantified by using a range of assay read-outs that included extracellular or intracellular p24 antigen detection, RNA quantification and luciferase and beta-galactosidase reporter gene expression. FINDINGS: PSV assays were generally more sensitive than VI assays, but there were important differences according to the virus and inhibitor used. For example, for TriMab, the mean IC50 was always lower in PSV than in VI assays. However, with 4E10 or sCD4 some viruses were neutralized with a lower IC50 in VI assays than in the PSV assays. Inter-laboratory concordance was slightly better for PSV than for VI assays with some viruses, but for other viruses agreement between laboratories was limited and depended on both the virus and the neutralizing reagent. CONCLUSIONS: The NeutNet project demonstrated clear differences in assay sensitivity that were dependent on both the neutralizing reagent and the virus. No single assay was capable of detecting the entire spectrum of neutralizing activities. Since it is not known which in vitro assay correlates with in vivo protection, a range of neutralization assays is recommended for vaccine evaluation.

Anti-human immunodeficiency virus type 1 humoral immune response and highly active antiretroviral treatment.

Highly active antiretroviral treatment (HAART) of human immunodeficiency type 1 (HIV-1) infection is very effective in controlling infection, but elimination of viral infection has not been achieved as yet, and upon treatment interruption an immediate rebound of viremia is observed. A combination of HAART with an immune stimulation might allow treatment interruption without this rebounding viremia, as the very low viremias observed with successful HAART may be insufficient to permit maintenance of a specific anti-HIV-1 immune response. The objective of this study was to compare the humoral immune response of individuals undergoing successful HAART (NF=no failure) with that of individuals with evidence of failure of therapy (FT) and to verify if the viremia peaks observed in individuals with therapy failure would act as a specific stimulus for the humoral anti-HIV-1 immune response. Antibodies binding to gp120 V3 genotype consensus peptides were more frequently observed for FT, mainly against peptides corresponding to sequences of genotypes prevalent in the Rio de Janeiro city area, B and F. HIV-1 neutralization of HIV-1 IIIB and of four primary isolates from Rio de Janeiro was less frequently observed for plasma from the NF than the FT group, but this difference was more expressive when plasma from individuals with detectable viremia were compared to that of individuals with undetectable viral loads in the year before sample collection. Although statistically significant differences were observed only in some specific comparisons, the study indicates that presence of detectable viremia may contribute to the maintenance of a specific anti-HIV-1 humoral immune response.

Design, synthesis and pharmacological evaluation of HIV-1 reverse transcriptase inhibition of new indolin-2-ones.

The design, synthesis and anti HIV-1 replication inhibition of 3-(cyclopropylethynyl)-3-hydroxy-indolin-2-ones, analogues of efavirenz (Sustivatrade mark), are described. Different substituted isatins were used to generate final products that contain pharmacophoric features for RT inhibition, such as the oxoindole and cyclopropylethynyl groups. The suitability of the indolin-2-one ring in the planned compounds in replacement to the benzoxazinone ring of efavirenz was proven, since compound 15 presented a greater activity than efavirenz against HIV-1 replication and was not significantly cytotoxic.

Anti-human immunodeficiency virus type 1 humoral immune response and highly active antiretroviral treatment

Highly active antiretroviral treatment (HAART) of human immunodeficiency type 1 (HIV-1) infection is very effective in controlling infection, but elimination of viral infection has not been achieved as yet, and upon treatment interruption an immediate rebound of viremia is observed. A combination of HAART with an immune stimulation might allow treatment interruption without this rebounding viremia, as the very low viremias observed with successful HAART may be insufficient to permit maintenance of a specific anti-HIV-1 immune response. The objective of this study was to compare the humoral immune response of individuals undergoing successful HAART (NF=no failure) with that of individuals with evidence of failure of therapy (FT) and to verify if the viremia peaks observed in individuals with therapy failure would act as a specific stimulus for the humoral anti-HIV-1 immune response. Antibodies binding to gp120 V3 genotype consensus peptides were more frequently observed for FT, mainly against peptides corresponding to sequences of genotypes prevalent in the Rio de Janeiro city area, B and F. HIV-1 neutralization of HIV-1 IIIB and of four primary isolates from Rio de Janeiro was less frequently observed for plasma from the NF than the FT group, but this difference was more expressive when plasma from individuals with detectable viremia were compared to that of individuals with undetectable viral loads in the year before sample collection. Although statistically significant differences were observed only in some specific comparisons, the study indicates that presence of detectable viremia may contribute to the maintenance of a specific anti-HIV-1 humoral immune response.

Is human immunodeficiency virus/acquired immunodeficiency syndrome decreasing among Brazilian injection drug users? Recent findings and how to interpret them.

We briefly review findings from Brazilian settings where the human immunodeficiency virus/acquired immunodeficiency syndrome (HIV/AIDS) epidemic among injection drug users (IDUs) seems to be decreasing, highlighting recent findings from Rio de Janeiro and discussing methodological alternatives. Former analyses using serologic testing algorithm for recent HIV seroconversion have shown that HIV incidence has been low in IDUs recruited by two different surveys carried out in Rio, where low injection frequencies and infection rates have been found among new injectors. The proportion of AIDS cases among IDUs in Rio has been fairly modest, compared to São Paulo and especially to the southernmost states. Notwithstanding, the interpretation of findings from serial surveys constitutes a challenge, magnified in the assessment of HIV spread among IDUs due to the dynamic nature of the drug scenes and limitations of sampling strategies targeting hard-to-reach populations. Assessment of epidemic trends may profit from the triangulation of data, but cannot avert biases associated with sampling errors. Efforts should be made to triangulate data from different sources, besides exploring specific studies from different perspectives. In an attempt to further assess the observed trends, we carried out original analyses using data from Brazilian AIDS databank.

The role of "long-term" and "new" injectors in a declining HIV/AIDS epidemic in Rio de Janeiro, Brazil.

BACKGROUND: A substantial decline of HIV prevalence has been observed in injection drug users (IDUs) from Rio de Janeiro, in recent years. Differential characteristics and behaviors of new (injecting for <6 years) and long-term (>=6y) injectors may help to understand recent changes and to implement appropriate prevention strategies. METHODS: Between October 1999 and December 2001, 609 active/ex-IDUs were recruited from different communities, interviewed, and tested for HIV. Contingency table analysis and t-tests were used to assess differences between new and long-term injectors. Multiple logistic regression was used to identify independent predictors of HIV serostatus for long-term and new injectors. RESULTS: HIV prevalence was 11.7% for 309 long-term injectors (95% CI 8.1-15.3) and 4.3% for 300 new injectors (95% CI 2.0-6.6). New injectors reported having engaged in treatment and having received syringes from needle exchange programs (NEPs) more frequently than long-term injectors in the last 6 months, but sharing behaviors remained frequent and even increased vis-à-vis long-term injectors. For male new injectors, "sexual intercourse with another man" was found to be the sole significant risk factor for HIV infection (Adj OR = 8.03; 95% CI 1.52-42.48). Among male long-term injectors, "to have ever injected with anyone infected with HIV" (Adj OR = 3.91; 95% CI 1.09-14.06) and to have "ever been in prison" (Adj OR = 2.56; 95% CI 1.05-6.24) were found to be significantly associated with HIV infection. DISCUSSION: New injectors are seeking help in drug treatment centers or needle exchange programs. They differ from long-term injectors in terms of their risk factors for HIV infection and have lower prevalence levels for HIV. Such differences may help to understand the recent dynamics of HIV/AIDS in this population and highlight the need to reinforce new injectors' help-seeking behavior and to reduce current unacceptably high levels of unprotected sex and syringe sharing in new injectors despite attendance of prevention/treatment programs.

Is human immunodeficiency virus/acquired immunodeficiency syndrome decreasing among Brazilian injection drug users? Recent findings and how to interpret them

We briefly review findings from Brazilian settings where the human immunodeficiency virus/acquired immunodeficiency syndrome (HIV/AIDS) epidemic among injection drug users (IDUs) seems to be decreasing, highlighting recent findings from Rio de Janeiro and discussing methodological alternatives. Former analyses using serologic testing algorithm for recent HIV seroconversion have shown that HIV incidence has been low in IDUs recruited by two different surveys carried out in Rio, where low injection frequencies and infection rates have been found among new injectors. The proportion of AIDS cases among IDUs in Rio has been fairly modest, compared to São Paulo and especially to the southernmost states. Notwithstanding, the interpretation of findings from serial surveys constitutes a challenge, magnified in the assessment of HIV spread among IDUs due to the dynamic nature of the drug scenes and limitations of sampling strategies targeting hard-to-reach populations. Assessment of epidemic trends may profit from the triangulation of data, but cannot avert biases associated with sampling errors. Efforts should be made to triangulate data from different sources, besides exploring specific studies from different perspectives. In an attempt to further assess the observed trends, we carried out original analyses using data from Brazilian AIDS databank.

HIV-1 infection among injection and ex-injection drug users from Rio de Janeiro, Brazil: prevalence, estimated incidence and genetic diversity.

BACKGROUND AND OBJECTIVES: Due to their behavioral conditions and vulnerability, injection drug users (IDUs) are prone to multiple simultaneous or sequential infections with distinct HIV-1 subtypes and variants, making them a key population for molecular epidemiology surveillance. In the present study, we evaluated HIV-1 infection seroprevalence, genetic diversity and estimated incidence among IDUs and ex-injection drug users (ex-IDUs) from Rio de Janeiro, Brazil. STUDY DESIGN: Six hundred and eight IDUs and ex-IDUs, recruited between 1999 and 2001, were interviewed and agreed to donate 30 ml of blood. The serologic status for HIV infection was determined by two ELISAs and confirmed by IFA. CD4+ T-cell percentages were assessed by flow cytometry. HIV-1 positive samples were submitted to viral load quantification. DNA samples were PCR amplified and HIV-1 subtypes were determined using env and gag HMA. RESULTS AND CONCLUSIONS: Forty-eight (7.89%) individuals were seropositive for HIV-1 infection. The seroincidence of HIV-1 infection was estimated as 0.76%. HIV-1 env and gag subtyping identified 29 (69%) samples as belonging to subtype B, 7 (16.7%) to subtype F, and 6 (14.3%) discordant env/gag genomes infections, indicating the circulation of recombinant viruses in this population.

Anti-human immunodeficiency virus-1 antibody titers in injection drug users compared to sexually infected individuals.

Sera from infected injection drug users (IDU) have shown to have antibodies against synthetic human immunodeficiency virus-1 (HIV-1) envelope peptides more frequently. In this study, reactivity of 48 IDU plasma were compared to 60 plasmas obtained from sexually infected individuals (S). The overall reactivity of plasma from IDU compared to S was higher, and the reactivity titers were much higher for IDU plasma than S. IDU plasma also showed a broader antibody response. The higher reactivity titers were observed mainly for the gp41 immunodominant epitope and V3 peptides corresponding to the consensus sequences of HIV-1 subtypes/variants prevalent in Brazil (B, F, C) indicating the specificity in the higher immune response of IDU.

Anti-human immunodeficiency virus-1 antibody titers in injection drug users compared to sexually infected individuals

Sera from infected injection drug users (IDU) have shown to have antibodies against synthetic human immunodeficiency virus-1 (HIV-1) envelope peptides more frequently. In this study, reactivity of 48 IDU plasma were compared to 60 plasmas obtained from sexually infected individuals (S). The overall reactivity of plasma from IDU compared to S was higher, and the reactivity titers were much higher for IDU plasma than S. IDU plasma also showed a broader antibody response. The higher reactivity titers were observed mainly for the gp41 immunodominant epitope and V3 peptides corresponding to the consensus sequences of HIV-1 subtypes/variants prevalent in Brazil (B, F, C) indicating the specificity in the higher immune response of IDU

Vertical human immunodeficiency virus type 1 - HIV-1 -transmission - a review

Several factors appear to affect vertical HIV-1 transmission, dependent mainly on characteristics of the mother (extent of immunodeficiency, co-infections, risk behaviour, nutritional status, immune response, genetical make-up), but also of the virus (phenotype, tropism) and, possibly, of the child (genetical make-up). This complex situation is compounded by the fact that the virus may have the whole gestation period, apart from variable periods between membrane rupture and birth and the breast-feeding period, to pass from the mother to the infant. It seems probable that an extensive interplay of all factors occurs, and that some factors may be more important during specific periods and other factors in other periods. Factors predominant in protection against in utero transmission may be less important for peri-natal transmission, and probably quite different from those that predominantly affect transmission by mothers milk. For instance, cytotoxic T lymphocytes will probably be unable to exert any effect during breast-feeding, while neutralizing antibodies will be unable to protect transmission by HIV transmitted through infected cells. Furthermore, some responses may be capable of controlling transmission of determined virus types, while being inadequate for controlling others. As occurence of mixed infections and recombination of HIV-1 types is a known fact, it does not appear possible to prevent vertical HIV-1 transmission by reinforcing just one of the factors, and probably a general strategy including all known factors must be used. Recent reports have brought information on vertical HIV-1 transmission in a variety of research fields, which will have to be considered in conjunction as background for specific studies

HIV specific humoral immune response in Rio de Janeiro, Brazil

Efforts to characterize HIV-1 polymorphism and anti-HIV immune response are being made in areas where anti-HIV/AIDS vaccines are to be employed. Anti-HIV-1 humoral immune response is being studied in infected individuals resident in Rio de Janeiro, in distinct cohorts involving recent seroconvertors, pregnant women or intravenous drug users (IDU). Comparative analysis of specificity of antibody response towards epitopes important for anti-HIV-1 immune response indicate quantitative differences between cohorts, with an exceptionally strong response in IDUs and weakest response in pregnant women. However, a comparative analysis between pregnant women cohorts from Rio de Janeiro and Rio Grande do Sul indicated an even lower response (with exception of the anti-V3-C clade peptide recognition) for the southern cohort. Studied analysing the immune function of the humoral response indicate a quite elevated occurrence of antibodies capable of neutralizing heterologous primary HIV-1 isolates from Rio de Janeiro. Attempts to correlate seroreactivity with HIV-1 neutralization with respect to HIV-1 polymorphism were not very successfull: while the Brazilian B clade B" variant could be recognized by binding assays, no significant distinction of HIV-1 clades/variants was observed in viral neutralization assays.