Direct Measurement of the Astrophysical

We have performed the first direct measurement of the ^{38}K(p,γ)^{39}Ca reaction using a beam of radioactive ^{38}K. A proposed ℓ=0 resonance in the ^{38}K+p system has been identified at 679(2) keV with an associated strength of 120_{-30}^{+50} meV. Upper limits of 1.16 (3.5) and 8.6 (26) meV at the 68% (95%) confidence level were also established for two further expected ℓ=0 resonances at 386 and 515 keV, respectively. The present results have reduced uncertainties in the ^{38}K(p,γ)^{39}Ca reaction rate at temperatures of 0.4 GK by more than 2 orders of magnitude and indicate that Ar and Ca may be ejected in observable quantities by oxygen-neon novae. However, based on the newly evaluated rate, the ^{38}K(p,γ)^{39}Ca path is unlikely to be responsible for the production of Ar and Ca in significantly enhanced quantities relative to solar abundances.

Efficient isolation and propagation of human immunodeficiency virus on recombinant colony-stimulating factor 1-treated monocytes.

Monocytes were maintained in tissue culture for greater than 3 mo in media supplemented with rCSF-1. These cultures provided susceptible target cells for isolation and propagation of virus from PBMC of HIV-infected patients. HIV isolated into monocytes readily infected other rCSF-1-treated monocytes but only inefficiently infected PHA-stimulated lymphoblasts. Similarly, laboratory HIV strains passaged in T cell lines or virus isolated from patients' leukocytes into PHA-stimulated lymphoblasts inefficiently infected rCSF-1-treated monocytes. Persistent, low-level virion production was detected in macrophage culture fluids by reverse transcriptase activity or HIV antigen capture through 6-7 wk. Marked changes in cell morphology with cell death, syncytia, and giant cell formation were observed in monocyte cultures 2 wk after infection, but at 4-6 wk, all cells appeared morphologically normal. However, the frequency of infected cells in these cultures at 6 wk was 60-90% as quantified by in situ hybridization with HIV RNA probes or by immunofluorescence with AIDS patients' sera. Ultrastructural analysis by EM also showed a high frequency of infected cells; virtually all HIV budded into and accumulated within cytoplasmic vacuoles and virus particles were only infrequently associated with the plasma membrane. Retention of virus within macrophages and the macrophage tropism of HIV variants may explain mechanisms of both virus persistence and dissemination during disease.

Type-restricted neutralization of molecular clones of human immunodeficiency virus.

In a study of the immunologic significance of the genetic diversity present within single isolates of human immunodeficiency virus type 1 (HIV-1), the neutralization of viruses derived from molecular clones of the HIV-1 strain HTLV-IIIB by an extensive panel of sera was compared. Sera from HIV-1-infected patients and from goats immunized with polyacrylamide gel-purified HIV-1 envelope glycoprotein (gp120), native gp120, or gp120-derived recombinant peptides, showed marked heterogeneity in neutralizing activity against these closely related viruses. The change of a single amino acid residue in gp120 may account for such "clonal restriction" of neutralizing activity.

Antiviral effect and ex vivo CD4+ T cell proliferation in HIV-positive patients as a result of CD28 costimulation.

Because stimulation of CD4+ lymphocytes leads to activation of human immunodeficiency virus-type 1 (HIV-1) replication, viral spread, and cell death, adoptive CD4+ T cell therapy has not been possible. When antigen and CD28 receptors on cultured T cells were stimulated by monoclonal antibodies (mAbs) to CD3 and CD28 that had been immobilized, there was an increase in the number of polyclonal CD4+ T cells from HIV-infected donors. Activated cells predominantly secreted cytokines associated with T helper cell type 1 function. The HIV-1 viral load declined in the absence of antiretroviral agents. Moreover, CD28 stimulation of CD4+ T cells from uninfected donors rendered these cells highly resistant to HIV-1 infection. Immobilization of CD28 mAb was crucial to the development of HIV resistance, as cells stimulated with soluble CD28 mAb were highly susceptible to HIV infection. The CD28-mediated antiviral effect occurred early in the viral life cycle, before HIV-1 DNA integration. These data may facilitate immune reconstitution and gene therapy approaches in persons with HIV infection.

HIV-1 genetic diversity.

BACKGROUND: HIV-1 evolves by rapid mutation and by recombination, both processes actively contributing to its genetic diversity. Most of the multiple genetic subtypes and intersubtype recombinations of HIV-1 that comprise the global pandemic have not been characterized by full genome sequencing. METHODS: DNA from primary virus cultures on donor peripheral blood mononuclear cells was used as template for long polymerase chain reaction amplification, molecular cloning, and automated sequencing of virtually full-length HIV-1 genomes from subtypes A, C, E, G and A/D recombinant forms. Standard phylogenetic analysis methods were employed, and some were modified for the detection and mapping of recombinant breakpoints. RESULTS: Subtypes A, B, C and D are largely, if not entirely, distinguishable throughout the genome and show no clear evidence of intersubtype recombination. In contrast, all available sequences of subtypes E and G are recombinant with subtype A. Full-length sequences of subtypes F, H, I and J are still unavailable. Subtype E and G, and some A/D recombinant HIV, have retained the cytoplasmic domain of gp41 from subtype A. Some recombinants possess the matrix and core of one subtype and the outer envelope of another, resembling pseudotypes. Certain pairs of subtypes may have recombined more often than others. CONCLUSION: Recombinant HIV-1 have already established a global reservoir and are largely responsible for the rapidly expanding subtype E epidemic in Southeast Asia. Recombination may have played a key role in the evolution of HIV-1 and the geographic intermixing of subtypes, which is increasing, may foster the emergence of a even greater variety of recombinant strains.

V3 seroreactivity and sequence variation: tracking the emergence of V3 genotypic variation in HIV-1-infected patients.

OBJECTIVE: To investigate the relationship between V3-specific immune responses and viral quasispecies evolution in 10 HIV-1-seropositive patients enrolled in a phase I trial of recombinant gp160. METHODS: Serologic responses to the HIVLAI V3 loop and autologous V3 loop DNA sequences were sequentially determined over a 3-4-year interval. RESULTS: Six patients either seroconverted or had a > or = 42-fold boost in titer to the V3 reagent associated with an average of 3.2 amino-acid changes in their autologous V3 loops. Four patients with < or = 11-fold change in titer to the V3 loop showed an average of 0.75 amino-acid changes. Attempts to measure autologous V3 loop responses in four patients using a peptide enzyme-linked immunosorbent assay technique did not show a distinct binding preference for autologous versus heterologous V3 loop peptides. Thus, we interpret seroreactivity to the heterologous HIVLAI V3 loop to reflect the broadness of the V3 immune response rather than a direct measure of epitope-specific immune pressure. CONCLUSIONS: These data suggest that the broadness of serologic responses to viral epitopes are reflected in the rate of evolution of their cognate coding sequences and support the view that the immune response to HIV-1 results in the continuous selection of new viral variants during the course of disease.

Rates of p24 antigenemia and viral isolation in comparable white and black HIV-infected subjects. Military Medical Consortium for Applied Retroviral Research.

OBJECTIVE: To determine the relative frequencies of HIV-1 p24 antigen and culture positivity in white and black patients. DESIGN: Volunteers in the US military's HIV natural history study were 46% white, 44% black, 7% Hispanic and 3% other. Focusing on the comparable groups of whites and blacks, a retrospective analysis was performed of the results of virologic assays collected over a 2-year period. METHODS: p24 antigen was quantitated in sera with and without immune complex dissociation (ICD); viral isolation was performed by coculture of peripheral blood mononuclear cells. RESULTS: Results of the two virologic assays were very similar in the two racial groups, both overall and after stratification by CD4 cell count. As reported previously, the concentration of serum immunoglobulin G was found to be greater in black than white subjects. In contrast to results with ICD, sera tested without ICD resulted in differing (higher) rates of antigenemia in whites than blacks (P = 0.002). CONCLUSIONS: The frequencies of p24 antigen and culture positivity were found to be independent of race. Previously observed racial differences in antigen positivity were likely to be due to more extensive antibody binding in blacks than in whites.

Cardiac risk factors and complications in non-cardiac surgery.

In an attempt to assess cardiac risk in non-cardiac surgery, 1001 patients over 40 years of age who underwent major operative procedures were examined preoperatively, observed through surgery, studied with at least one postoperative electrocardiogram, and followed until hospital discharge or death. Documented postoperative myocardial infarction occurred in only 18 patients; though most of these patients had some pre-existing heart disease, there were few preoperative factors which were statistically correlated with postoperative infarction. Postoperative pulmonary edema was strongly correlated with preoperative heart failure, but 21 of the 36 patients who developed pulmonary edema did not have any prior history of heart failure. Nearly all of these 21 patients were elderly, had abnormal preoperative electrocardiograms, and had intraabdominal or intrathoracic surgery. In the absence of an acute infarction, bifascicular conduction defects, with or without PR interval prolongation, never progressed to complete heart block. Spinal anesthesia protected against postoperative heart failure but not against other cardiac complication. By multivariate regression analysis, postoperative cardiac death was significantly correlated with (a) myocardial infarction in the previous 6 months; (b) third heart sound or jugular venous distention immediately preoperatively; (c) more than five premature ventricular contractions per minute documented at any time preoperatively; (d) rhythm other than sinus, or premature atrial contractions on preoperative electrocardiogram; (e) age over 70 years; (f) significant valvular aortic stenosis; (g) emergency operation; (h) a 33% or greater fall in systolic blood pressure for more than 10 minutes intraoperatively. Notably unimportant factors included smoking, glucose intolerance, hyperlipidemia, hypertension, peripheral atherosclerotic vascular disease, angina, and distant myocardial infarction.

Immunologic parameters in early-stage HIV-seropositive subjects associated with vaccine responsiveness.

Twenty-one asymptomatic HIV-seropositive subjects and 20 HIV-seronegative controls were assessed for their serologic response to multiple live attenuated viral, protein (toxoid), and polysaccharide vaccine antigens. Extensive in vivo and in vitro immunologic evaluations were performed. Factors predictive of immunogen responsiveness by HIV-seropositive patients were found by correlating vaccine responses with results of T- and B-cell functional assays. Eleven HIV-seropositive patients (HIV nonresponsive-NR) responded to only one of three vaccines used for analysis (meningococcus, group C; adenovirus 4, 7; and diphtheria-tetanus) compared with the normals, of whom 100% responded to two or more of the same immunogens. Ten HIV-seropositive patients (HIV responsive-R) responded equivalently to normals. The HIV NR group had distinctive immunologic abnormalities predictive of their poor immunogen responsiveness. These included defects in the T-cell helper function despite normalization of T cell number and defective T-cell suppression of Epstein-Barr virus (EBV) in vitro (HIV NR, 30% suppression; HIV R, 73% suppression; and normals, 95% suppression of EBV-driven immunoglobulin production in vitro). The B cells of the HIV NR groups were also abnormal in vivo. The HIV NR patients' B cells were larger and had increased native response to B-cell growth factor evidenced by increased thymidine incorporation. (HIV-NR, 10,232 +/- 3,003 cpm; HIV R, 5,432 +/- 1,125; normal, 402 +/- 11. HIV NR/HIV R, p less than 0.05; HIV NR/N, p less than 0.001.)(ABSTRACT TRUNCATED AT 250 WORDS)

Isolation of HIV-1 from the blood of seropositive adults: patient stage of illness and sample inoculum size are major determinants of a positive culture. The Walter Reed Retroviral Research Group.

Results of HIV-1 blood cultures from 609 seropositive adults across all stages of illness at the Walter Reed Army Medical Center were reviewed. HIV-1 was isolated by coculturing of patient peripheral blood mononuclear leukocytes (PBMCs) with normal blood donor target PBMCs that had been stimulated with phytohemagglutinin and interleukin-2. The HIV-1 isolation success rate at Walter Reed increased progressively each year from 1986 to 1989. In 1989, HIV-1 was isolated from a single blood specimen from patients in Walter Reed stages 1-2, 3-4, and 5-6 in 75% (49/65), 90% (37/41), and 97% (30/31) of cases, respectively. None of 22 blinded negative control specimens was positive. PBMC cultures from late stage patients regularly became positive within 7 days (92%), compared to only 46% of positive cultures from early stage patients. For most patients, the lowest number of serially diluted PBMCs that resulted in a positive culture was 30,000 patient PBMCs, but the range was 300 to 3 million cells. HIV-1 was isolated less frequently from plasma (5/18, 28%). Plasma viremia was detected only in patients with relatively high titers of infected PBMCs. Forty-six blood specimens from "at-risk" seronegative adults were also cocultured; none was positive.

Preferential antibody recognition of structurally distinct HIV-1 gp120 molecules.

We have developed an assay, using a biosensor matrix and surface plasmon resonance, that rapidly and reproducibly measures antibody reactivity to human immunodeficiency virus type 1 (HIV-1) gp120 in various structural conformations. In particular, antibodies displaying preferential reactivity to a CD4-binding competent ("native," rgp120) or CD4-binding incompetent ("reduced," rcmgp120) monomeric gp120 molecule were distinguished. This technique has advantages over conventional enzyme-linked immunosorbent assay (ELISA) methodology in which it is difficult to control the concentration of protein adsorbed to the ELISA wells and a significant disruption of protein structure occurs on adsorption. A population of gp120 molecules that lacked CD4 receptor binding capacity and bound antibodies specific for reduced gp120 was found in several native gp120 preparations. The relative amount of this CD4-binding incompetent population varied among the various preparations studied. This presence of CD4-binding incompetent molecules within various native recombinant gp120 preparations may have implications for HIV-1 envelope vaccine development. By measuring antibody-binding ratios, several monoclonal antibodies were identified, which, although elicited by immunization with various native gp120 preparations, bound specifically to reduced gp120. The ability to screen antibody specificity against HIV-1 envelope proteins with different conformations will assist in determining the quality of antibodies induced by various HIV-1 envelope vaccine candidates.

Evidence for spread of the human immunodeficiency virus epidemic into low prevalence areas of the United States.

Reports of an increased proportion of AIDS cases occurring in small and medium-sized cities suggest that the HIV epidemic may be spreading into locations that were previously characterized by their low HIV antibody prevalences. Studying the question of the geographic spread of the HIV infection epidemic (rather than the AIDS epidemic) has been difficult largely because most serial seroprevalence data have been gathered from cohorts of high risk individuals (e.g., homosexual/bisexual cohorts) in New York City, San Francisco, and other geographically circumscribed areas. The U.S. military applicant HIV screening data were used in the current report to examine rates and 24 month temporal trends in geographic areas characterized by their HIV endemicities. The data examined concern the seven most populous states and four hyperendemic metropolitan areas located within those states (New York City, Miami, Houston, and San Francisco). In the nonepidemic regions, seroprevalence rates increased among black and white applicants. In the four epidemic urban areas, only young black applicants had higher HIV seroprevalence rates during the second 12 month period. Six of the seven nonepidemic regions had positive HIV seroprevalence trends, and these trends were significant in Florida, California, Texas, Illinois, and Ohio. The increases in these regions were greater for young blacks (30% excess for year 2 vs. year 1) compared to young whites (12% excess for year 2 vs. year 1). These data provide evidence of birth year specific increases in seroprevalence over time occurring in presumed low HIV prevalence areas. These increases cannot be due to, but are observed in spite of, biases associated with increasing self-selection over time.

Genetic comparison of human immunodeficiency virus (HIV-1) isolates by polymerase chain reaction.

Amplification of DNA by polymerase chain reaction (PCR) is influenced by the homology of oligonucleotide primers with the DNA template. We have developed a procedure, termed anchored PCR, whereby nucleotide sequence alterations in the template can be directly related to the quantity of amplified product. Genetic variation in the human immunodeficiency virus HIV-1 has been studied using anchored PCR. In four field isolates of the virus, the 3'LTR was compared both by PCR analysis of DNA from virus cultures and DNA sequencing. DNA templates that matched the primers varied less than threefold in PCR product yield, whereas significant 3' end primer-template mispairing decreased PCR product 10- to 100-fold. Using these guidelines for genetic variability manifested through PCR, 40 PCR primers encompassing the GAG, ENV, and 3' LTR segments of the genome were used to compare sequential HIV-1 isolates form six patients. Some primers were apparently located in genomic regions without significant interisolate variability, as they yielded equivalent amounts of amplified DNA from all the isolates. The quantity of amplified DNA obtained with other primers varied 10- to 100-fold among patients, but was consistent for sequential isolates from an individual patient. Two African HIV-1 isolates were readily distinguished from a panel of North American isolates by the same method. Systematic classification of HIV-1 genetic variants may be possible by anchored PCR.

Immunization of HIV-infected patients with rgp160: modulation of anti-rgp120 antibody spectrotype.

HIV-1 infection results in progressive failure of the immune system with decline in the number and/or function of B-cell clones originally recruited in specific humoral responses. Spectrotypic analysis, done by isoelectric focusing and reverse blotting (IEF-RB), is one technique for evaluating the activity and the number of specific B-cell clones and is adaptable to the direct measurement of antibodies to conformationally intact epitopes. The anti-HIV-1 (IIIB) rgp120 spectrotype was measured in 30 early-stage HIV-infected volunteers undergoing vaccine therapy with recombinant gp160 (rgp160). Twenty-five of the patients displayed a clear oligoclonal banding pattern; seven (28%) showed the same pattern in all samples, while 18 (72%) showed changes. Ten of the latter had an increase in band intensity over the course of immunization, and eight had an increase in both band intensity and number of bands. In contrast, serum samples from eight patients receiving placebo (alum) showed no changes over a comparable period. These findings suggest that vaccine therapy with rgp160 may be able to expand the anti-HIV-1 (LAI) gp120 B-cell clone pool in some HIV-infected patients as well as increase antibody synthesis by established B-cell clones recruited during natural infection. These data provide further evidence that postinfection vaccination may provide an alternative strategy in the treatment of chronic viral diseases.

Tracking the spread of the HIV infection epidemic among young adults in the United States: results of the first four years of screening among civilian applicants for U.S. military service.

Because the period from infection to clinically apparent disease is long, variable, and changing as new therapies are developed and applied, AIDS data are inadequate for tracking current values of critical parameters of HIV infection epidemics: prevalence of infection, rate of acquisition of new infections (incidence rate), and direction and rate of change of infection incidence over time (acceleration). These "vital signs" of infection epidemics can be tracked using serial cross-sectional seroprevalence data, however. From October 1985 through September 1989, more than 2.3 million applicants for U.S. military service were screened for antibody to HIV. The overall seroprevalence was 1.31 per 1,000 (3,014/2,300,675). Seroprevalences were highest near urban centers of the AIDS epidemic and were independently associated with age, race/ethnicity, and gender. Based on age seroprevalence trends, it was crudely estimated that at least one of 2,000 young men and one of 7,000 young women are infected with HIV annually in the U.S. Infection incidence rates, estimated from age and temporal trends, were estimated to be highest among black males (1.40/1,000/year) and lowest among white females (0.03/1,000/year). Poisson regression analysis of seroprevalence trends suggested that infection incidence rates accelerated among black females during the first 3 years of screening. Since selection factors undoubtedly changed over the period, estimates based on these data probably underestimate actual values in the general population, particularly near urban AIDS epicenters. Nonetheless, even crude estimates of these critical values, particularly among adolescents and young adults, are useful to guide policy development, to allocate resources, and to monitor program effects.

Sources of variability in repeated T-helper lymphocyte counts from human immunodeficiency virus type 1-infected patients: total lymphocyte count fluctuations and diurnal cycle are important.

The study objective was to determine the causes and magnitude of absolute CD4 (T4) count variation in human immunodeficiency virus type 1 (HIV-1)-infected (+) adult males. We conducted a prospective, blinded, and controlled study of 22 adult military male outpatients, including 16 HIV(+) [12 in Walter Reed stage (WR-) 1 through 5, 4 in WR-6 (AIDS)], and 6 HIV seronegative (-) healthy controls. Ten CD4+ cell counts were drawn within a 3-day interval from each patient at the following times: 0800, 1200, 1600, and 2200 h on day 1; and 0800, 1200, and 1600 h on days 2 and 3. A significant CD4+ cell count diurnal increase of 59 cells/mm3 was detected between 0800 h and 2200 h from the WR-1-5 patients (p = 0.018), although this diurnal change was significantly blunted (p = 0.028) as compared with the 506 cells/mm3 CD4+ cell count diurnal increase observed from the HIV(-) healthy controls. The coefficients of variation [CV = (standard deviation/average) x 100] of the three daily 0800 h CD4 cell counts from each patient were 15 (median) and 19 (average) for the WR-1-5 patient group. Blood leukocyte counts, differential fractions of lymphocytes, and total lymphocyte counts contributed more to the observed CD4+ cell count variability than did the CD4% measurements [CV = 7.5 (median), 11 (average)] obtained from flow cytometry. We conclude that the large fluctuations that we observed in repeated CD4+ cell counts in HIV(+) patients can be explained in part by CD4+ cell count diurnal cycle and in part by high variability in total lymphocyte counts.(ABSTRACT TRUNCATED AT 250 WORDS)

Safety and immunogenicity of multiple conventional immunizations administered during early HIV infection.

Twenty-one asymptomatic adults who had recently received multiple polysaccharide, live viral, and protein-derived vaccines were identified as being infected with human immunodeficiency virus (HIV). The mean subject age was 24 years (range 18-33); 20 of 21 (95%) were male. The mean T4 count was 523/mm3 with a mean T4/T8 ratio of 0.6. Serologic responses to immunization with meningococcus group C, adenovirus types 4 and 7, tetanus, and diphtheria were evaluated for the HIV seropositive subjects and were compared with the responses of similarly vaccinated age-, sex-, and race-matched HIV-seronegative controls. Significantly fewer (p less than 0.03) HIV subjects responded to meningococcus C (bactericidal antibody) and adenovirus 4 (neutralizing antibody) vaccines than did normals; the HIV-infected subjects who did respond produced functional antibody comparable to that of normals. Booster responses of HIV subjects to tetanus and diphtheria were comparable to those of normals. HIV-infected vaccine nonresponders did not differ from HIV-infected responders in total white blood cell, T4, T4/T8, total serum IgG, or delayed-type hypersensitivity skin test reactivity. All HIV subjects had negative cultures for live vaccine viruses (rubella, measles, adenovirus, and poliovirus). Postimmunization, no clinically apparent adverse reactions to vaccination were detected.

Genetic analysis of HIV-1 isolates from Zambia and an expanded phylogenetic tree for HIV-1.

Geographic variation in the HIV-1 virus is extensive but incompletely documented. We herein report the first genetic characterization of HIV-1 isolates from Zambia. The genomic region encoding the GAG polyprotein has been compared among 22 Zambian isolates and 14 North American isolates using a combination of polymerase chain reaction (PCR) and DNA sequencing methods. The Zambian isolates were similar to one another but distinct from other HIV-1 isolates. They exhibited a characteristic PCR "fingerprint" wherein certain primer combinations were unable to amplify because of mispairing. The sequence of the complete gag gene of three isolates from Zambia has been determined, and phylogenetic tree analysis placed them in a branch distinct from other African isolates and North American isolates. The PCR procedure used here may be widely applicable for genetic characterization of HIV-1.

Genetic analysis of HIV-1 isolates from Brazil reveals presence of two distinct genetic subtypes.

The spread of the human immunodeficiency virus type 1 (HIV-1) is by now virtually worldwide. An understanding of the genetic, biological, and immunological differences among isolates collected in different geographic locales is crucial for the development of globally effective vaccines. Here we report the genetic characteristics of 21 HIV-1 isolates from Brazil. The isolates were initially characterized using a heteroduplex mobility assay. The majority (17 of 21) were related to North American/European reference isolates of genetic subtype B. Four isolates belonged to a more recently identified genotype, termed subtype F. The subtype F sequences from Brazil are distinguishable in both gag and env from five other genetic subtypes of HIV-1 currently recognized. Like many locales, Brazil harbors more than one HIV-1 subtype.

PIP: The spread of the human immunodeficiency virus type 1 (HIV-1) is by now virtually worldwide. An understanding of the genetic, biological, and immunological differences among isolates collected in different geographic locales is crucial for the development of globally effective vaccines. The genetic characteristics of HIV-1 isolates from whole blood samples of 21 HIV-1-seropositive Brazilian patients collected during 1989 and 1990 are reported. Virus was isolated by cocultivation of patient peripheral blood mononuclear cells (PBMCs) with phytohemagglutinin (PHA)-stimulated donor PBMCs. The isolates were initially characterized using a heteroduplex mobility assay, which estimates the DNA sequence homology of a selected genomic region from different HIV-1 isolated from the migration of heteroduplexes in polyacrylamide gels. Five distinct HIV-1 envelope subtypes were identified, and a sixth subtype, termed F, was identified using isolates from Brazil and Romania. One Brazilian isolate was identified as subtype B by the more rapid relative migration of heteroduplexes. The majority (17 of 21) were related to North American/European reference isolates of genetic subtype B, whereas 4 isolates belonged to subtype F, a more recently identified genotype. The gag and env genes of several Brazilian isolates belonging to subtypes B and F were cloned and sequenced to allow a detailed analysis of their phylogenic relationships. This further established the existence of two distinct and well-separated genetic subtypes among Brazilian HIV-1 isolates. The subtype F sequences from Brazil are distinguishable in both gag and env from 5 other genetic subtypes of HIV-1 currently recognized. Like many locales, Brazil harbors more than one HIV-1 subtype.

Antibody recognition of SIVmac envelope peptides in plasma from macaques experimentally infected with SIV/Mne.

Four stretches of amino acid sequences encoded in conserved HIV-1 env domains and four parallel regions of the SIVmac env (two from gp120 and two from gp41/p32E) were fused to the NH2 terminus of beta-galactosidase by recombinant DNA techniques and used to analyze sera from three macaque species experimentally infected with SIV/Mne. All SIVmac env sequences were recognized by sera from the SIV/Mne-inoculated macaques. Western blot analysis performed with whole SIV/Mne, SIVmac, SIVagm, and HIV-1 antigens and sera from SIV/Mne-infected macaques also demonstrates that SIV/Mne is immunologically more closely related to SIVmac than to SIVagm or to HIV-1. Antibody levels to the gp120 NH2-terminal SIV-88 epitope appear to decrease in the infected Macaca nemestrina with progression of disease, as was also reported for the parallel HIV-1 epitope in HIV-1-infected individuals. Sera from all infected macaques reacted with the p32E-SIV-582 epitope (EKYLEDQAQLNAWGCAFRQVC). High titers to this immunodominant epitope could be detected at least 9 weeks postinfection and at a time when primarily the p28 and p32E antibodies were detectable in Western blots performed with whole disrupted SIV/Mne virus. In the majority of animals, antibody titers of 1:100,000 to SIV-582 develop during the infection and persist until death. Antibody responses to the SIV env epitopes in SIV/Mne-infected macaques thus resemble in many aspects (prevalence and immunogenicity) those observed previously for the corresponding HIV-1 env epitopes in HIV-1-infected humans.