A plain language summary of how well the single-dose Janssen vaccine works and how safe it is.

This is a summary of a publication about the ENSEMBLE trial of the Janssen Ad26.COV2.S vaccine against COVID-19, which was published in the New England Journal of Medicine in April 2021. The ENSEMBLE study started in September 2020 and is still ongoing. The study compared the effectiveness of the vaccine to a placebo in 43,783 adults from Latin America, South Africa, and the United States. Of those, 19,630 got a single dose of the vaccine. Compared to the placebo, the vaccine prevented: 66.9% of moderate to severe-critical COVID-19 cases after 14 days66.1% of moderate to severe-critical COVID-19 cases after 28 days85.4% of severe COVID-19 cases after 28 days100% of people with severe COVID-19 from needing to go to hospital for treatment None of the vaccinated participants died from COVID-19. There were 5 people who got the placebo who died from COVID-19. The vaccine was similarly effective in people from all age groups and different countries, including South Africa, where most cases were caused by the beta variant of the virus that originated there. The people in the study who got the vaccine who went on to get COVID-19 generally had milder and fewer symptoms than those who got the placebo. In most people, the vaccine started working after about 2 weeks. After receiving the vaccine, some people experienced pain at the injection site, headache, tiredness, muscle pain, and nausea. In most cases, these were mild and went away within a few days. Serious side effects were very rare. Blood clots, seizures, and tinnitus were very rare but were more common in the people who got the vaccine than in those who got the placebo. At the time of the study, it was not clear if these were caused by the vaccine or not. ClinicalTrials.gov NCT number: NCT04505722.

Immunity to malaria elicited by hybrid hepatitis B virus core particles carrying circumsporozoite protein epitopes.

The hepatitis B virus (HBV) nucleocapsid antigen (HBcAg) was investigated as a carrier moiety for the immunodominant circumsporozoite (CS) protein repeat epitopes of Plasmodium falciparum and the rodent malaria agent P. berghei. For this purpose hybrid genes coding for [NANP]4 (C75CS2) or [DP4NPN]2 (C75CS1) as internal inserts in HBcAg (between amino acids 75 and 81) were constructed and expressed in recombinant Salmonella typhimurium. The resulting hybrid HBcAg-CS polypeptides purified from S. typhimurium were particulate and displayed CS and HBc antigenicity, however, the HBc antigenicity was reduced compared to native recombinant HBcAg. Immunization of several mouse strains with HBcAg-CS1 and HBcAg-CS2 particles resulted in high titer, P.berghei- or P.falciparum-specific anti-CS antibodies representing all murine immunoglobulin G isotypes. The possible influence of carrier-specific immunosuppression was examined, and preexisting immunity to HBcAg did not significantly affect the immunogenicity of the CS epitopes within HBcAg-CS1 particles. Similarly, the choice of adjuvant did not significantly alter the immunogenicity of HBcAg-CS hybrid particles. Immunization in complete or incomplete Freund's adjuvant or alum resulted in equivalent anti-HBc and anti-CS humoral responses. Examination of T cell recognition of HBcAg-CS particles revealed that HBcAg-specific T cells were universally primed and CS-specific T cells were primed if the insert contained a CS-specific T cell recognition site. This indicates that the internal site in HBcAg is permissive for the inclusion of heterologous pathogen-specific T as well as B cell epitopes. Most importantly, 90 and 100% of BALB/c mice immunized with HBcAg-CS1 particles were protected against a P. berghei challenge infection in two independent experiments. Therefore, hybrid HBcAg-CS particles may represent a useful approach for future malaria vaccine development.

Oral Salmonella: malaria circumsporozoite recombinants induce specific CD8+ cytotoxic T cells.

Oral immunization with an attenuated Salmonella typhimurium recombinant containing the full-length Plasmodium berghei circumsporozoite (CS) gene induces protective immunity against P. berghei sporozoite challenge in the absence of antibody. We found that this immunity was mediated through the induction of specific CD8+ T cells since in vivo elimination of CD8+ cells abrogated protection. In vitro studies revealed that this Salmonella-P. berghei CS recombinant induced class I-restricted CD8+ cytotoxic T cells that are directed against the P. berghei CS peptide epitope spanning amino acids 242-253. This is the same peptide that previously was identified as the target of cytotoxic T lymphocytes (CTL) induced by sporozoite immunization. Salmonella-P. falciparum CS recombinants were constructed that contained either the full-length CS gene or a repeatless gene consisting of CS flanking sequences. Both of these vaccines were able to induce CD8+ CTL directed against P. falciparum CS peptide 371-390, which is identical to the target of CTL induced by sporozoites and vaccinia CS recombinants. These results directly demonstrate the ability of an intracellular bacteria such as Salmonella to induce class I-restricted CD8+ CTL and illustrate the importance of CD8+ CTL in immunity to malaria.

Pretreatment with recombinant murine tumor necrosis factor alpha/cachectin and murine interleukin 1 alpha protects mice from lethal bacterial infection.

Tumor necrosis factor/cachectin (TNF/C) is the principal mediator of bacterial endotoxin-induced shock and death. We found that the C3H/HeJ mouse, which is less able to produce TNF/C in response to endotoxin, has a 1,000-fold greater susceptibility to lethal infection with Escherichia coli than the TNF-responsive congenic mouse, C3H/HeN. This surprising finding suggested that this lethal peptide may also be involved in host protection. To test this hypothesis we pretreated the C3H/HeJ mouse with a combination of recombinant murine TNF/C-alpha and IL-1 alpha. This combination protected these mice against an intraperitoneal bacterial challenge of greater than 20 LD50S (nearly 2 x 10(2) CFU) that grew to a level of greater than 10(7) CFU/ml of blood and per gram of liver in untreated mice. This suggests a significant role for these cytokines in host defenses against invasive infections that require bacterial replication within the host. These protective mechanisms may not be important for less virulent organisms. These findings may have important implications for the proposed use of anti-TNF/C agents in the treatment of septic shock.

Attenuated Shigella as a DNA delivery vehicle for DNA-mediated immunization.

Direct inoculation of DNA, in the form of purified bacterial plasmids that are unable to replicate in mammalian cells but are able to direct cell synthesis of foreign proteins, is being explored as an approach to vaccine development. Here, a highly attenuated Shigella vector invaded mammalian cells and delivered such plasmids into the cytoplasm of cells, and subsequent production of functional foreign protein was measured. Because this Shigella vector was designed to deliver DNA to colonic mucosa, the method is a potential basis for oral and other mucosal DNA immunization and gene therapy strategies.

Oral Salmonella typhimurium vaccine expressing circumsporozoite protein protects against malaria.

Immunization with radiation-attenuated malaria sporozoites induces potent cellular immune responses, but the target antigens are unknown and have not previously been elicited by subunit vaccines prepared from the circumsporozoite (CS) protein. A method is described here for inducing protective cell-mediated immunity to sporozoites by immunization with attenuated Salmonella typhimurium transformed with the Plasmodium berghei CS gene. These transformants constitutively express CS antigens and, when used to immunize mice orally, colonize the liver, induce antigen-specific cell-mediated immunity, and protect mice against sporozoite challenge in the absence of antisporozoite antibodies. These data indicate that the CS protein contains T cell epitopes capable of inducing protective cell-mediated immunity, and emphasize the importance of proper antigen presentation in generating this response. Analogous, orally administered vaccines against human malaria might be feasible.

Increased guanylate cyclase activity is associated with an increase in cyclic guanosine 3',5'-monophosphate in left ventricular hypertrophy.

Left ventricular hypertrophy (LVH) produced by aortic valve plication leads to increased myocardial cyclic GMP. We tested whether this was a result of increased soluble guanylate cyclase activity or nitric oxide (NO) synthase and its functional consequences. We used the nitric oxide donor 3-morpholino-sydnonimine (SIN-1) or the NO synthase inhibitor NG-nitro-l-arginine methyl ester (L-NAME) in 12 control and 12 LVH anesthetized open-chest mongrel dogs. L-NAME (6 mg/kg) or SIN-1 (1 microgram/kg per min) was infused into the left anterior descending coronary artery and regional segment work and cyclic GMP levels were determined. In vitro myocardial guanylate cyclase sensitivity (0.43 +/- 0.04 to 0.28 +/- 0.04 mM [EC50]) and maximal activity (10.1 +/- 2.9 to 25.5 +/- 6.5 pmol/mg protein per min) were significantly increased in LVH as compared with control animals in response to nitroprusside stimulation, but cyclic GMP-phosphodiesterase activity was similar. In LVH dogs, basal cyclic GMP was significantly elevated in vivo when compared with controls. Treatment of dogs with SIN-1 resulted in a significant increase in cyclic GMP in control (1.09 +/- 0.12 to 1.48 +/- 0.19 pmol/gram) and a greater increase in the LVH group (1.78 +/- 0.16 to 3.58 +/- 0.71 pmol/g). L-NAME had no effect on myocardial cyclic GMP levels in control or LVH dogs. Segment work decreased in the control group after SIN-1 (1,573 +/- 290 to 855 +/- 211 grams x mm/min). LVH dogs showed no decrement in work as a result of treatment with SIN-1. L-NAME did not cause significant changes in myocardial cyclic GMP, O2 consumption, or work in either control or LVH dogs, but vascular effects were evident. SIN-1 increased cyclic GMP, and with greater effect on LVH; however, this resulted in a decrement in function only in the control group. The greater increased cyclic GMP in LVH dogs is not related to increased NO production, but is related to significantly higher sensitivity and maximal activity of soluble myocardial guanylate cyclase.

The importance of a lipopolysaccharide-initiated, cytokine-mediated host defense mechanism in mice against extraintestinally invasive Escherichia coli.

Extraintestinally invasive Escherichia coli (EC) that possess both a complete LPS and K1 capsule evade both complement-mediated bacteriolysis and neutrophil-mediated killing. Since C3H/HeJ mice that are hyporesponsive to LPS were uniquely susceptible to lethal infection with EC of this phenotype, we speculated there was an LPS-initiated host defense mechanism against this pathogenic phenotype. The LPS-normoresponsive C3H/HeN as well as the C3H/HeJ mice cleared these EC from the circulation within 4 h of intravenous administration. Whereas electron micrographs of the liver demonstrated these EC undergoing degeneration within the phagolysosomes of of both macrophages and Kupffer cells of C3H/HeN mice, these EC replicated within these cells of the C3H/HeJ mice. Restoration of anti-EC activity of C3H/HeJ mice occurred with activation of Kupffer cells and peritoneal macrophages in vivo with BCG and in vitro with IFN-gamma, but not with LPS. Pretreatment of C3H/HeJ mice with a combination of recombinant murine IL-1 and TNF-alpha also restored the killing of K1(+)-EC but did not enhance the killing of a K1(-)-EC mutant. These data are consistent with the hypothesis that (a) there is no intrinsic inability of C3H/HeJ phagocytes to kill EC, but (b) an LPS-initiated, cytokine-mediated host defense mechanism is required for such killing. These studies emphasize the importance of bacterial surface characteristics in the interaction with specific host defenses.

The K1 capsule is the critical determinant in the development of Escherichia coli meningitis in the rat.

Although Escherichia coli strains possessing the K1 capsule are predominant among isolates from neonatal E. coli meningitis and most of these K1 isolates are associated with a limited number of 0 lipopolysaccharide (LPS) types, the basis of this association of K1 and certain 0 antigens with neonatal E. coli meningitis is not clear. The present study examined in experimental E. coli bacteremia and meningitis in newborn and adult rats whether or not the K1 capsule and/or O-LPS antigen are critical determinants in the development of meningitis. Rats received subcutaneously at K1 E. coli strain (018+K1+) or mutants lacking either the K1 capsule (018+K1-) or 0 side-chain (018-K1+). 12-24 h later, blood and cerebrospinal fluid (CSF) specimens were obtained for quantitative cultures. The isolation of E. coli from CSF was observed in both newborn and adult rats infected with K1+ strains regardless of LPS phenotype (018+ or 18-) who also developed a high degree of bacteremia (e.g., greater than 10(4) CFU/ml of blood). In contrast, none of the newborn and adult rats infected with 018+K1- and developing bacteremia of greater than 10(4) were found to have positive CSF cultures. These findings indicate that the presence of the K1 capsule and a high degree of bacteremia are key determinants in the development of E. coli meningitis, suggesting that there may be specific binding sites present in the brain which have an affinity for the K1 capsule and thus may be responsible for the entry of K1-encapsulated E. coli into the meninges.

Safety and immunogenicity of a Pseudomonas aeruginosa O-polysaccharide toxin A conjugate vaccine in humans.

Lipid A-free polysaccharide (PS) isolated from Pseudomonas aeruginosa immunotype 5 lipopolysaccharide (LPS) was covalently coupled to toxin A via reductive amination. The PS-toxin A conjugate was comprised of 29.8% PS and 70.2% toxin A, possessed a molecular weight of greater than 1 X 10(6), was nontoxic for animals and was nonpyrogenic for rabbits at a dose of 50 micrograms/kg body wt when administered intravenously. The conjugate evoked only mild, transient reactions upon subcutaneous administration to human volunteers. Vaccination engendered immunoglobulin G (IgG) antibody, which neutralized the cytotoxic effect of toxin A and promoted the uptake and killing of P. aeruginosa in the presence of human polymorphonuclear leukocytes. Passively transferred IgG isolated from the serum of immunized donors was far more effective at preventing fatal P. aeruginosa burn wound sepsis than paired preimmunization serum. These studies establish the potential usefulness of such a PS-toxin A conjugate as a vaccine against P. aeruginosa.

Efficacy of antilipopolysaccharide and anti-tumor necrosis factor monoclonal antibodies in a neutropenic rat model of Pseudomonas sepsis.

Monoclonal antibodies (MAb) directed against bacterial lipopolysaccharide (LPS) and tumor necrosis factor-alpha (TNF) provide partial protection in experimental models of septic shock. To determine if additional benefit accrues from a combination of anti-TNF and anti-LPS MAb in the treatment of septic shock, a neutropenic rat model was developed to study active infection with Pseudomonas aeruginosa 12.4.4. Animals were treated intravenously with an irrelevant MAb (group 1); anti-TNF MAb (group 2); MAb directed against P. aeruginosa 12.4.4 LPS (group 3); or a combination of anti-TNF and anti-LPS MAb (group 4). None of the control animals in group 1 survived the 7-d period of neutropenia (0/16). In contrast, the survival rate was 44% in group 2 (P less than 0.02); 37% in group 3 (P less than 0.05); and 75% in group 4 (P less than 0.0002). The combination of monoclonal antibodies provided greater protection than either MAb given alone (P less than 0.05). Serum TNF levels during infection were significantly greater in groups 1 and 3 (20.1 +/- 3.3 U, mean +/- SE) than in groups 2 and 4 (0.9 +/- 0.8 U, P less than 0.0001). These results indicate that a combination of monoclonal antibodies to LPS and TNF have additive benefit in experimental Pseudomonas aeruginosa sepsis. This immunotherapeutic approach may be of potential utility in the management of serious, gram-negative bacterial infection in neutropenic patients.

Gonococcal pilus vaccine. Studies of antigenicity and inhibition of attachment.

A gonococcal pilus vaccine or placebo was injected subcutaneously or intramuscularly into 71 human volunteers. The vaccine was found to be safe. The principal adverse reaction was a complaint of a sore arm, which was caused, at least in part, to the volume of material injected. 6 of 64 (9%) volunteers receiving the larger doses also complained of malaise. The vaccine was found to be antigenic. All of the volunteers developed an immunoglobulin class-specific antibody response as measured by a solid phase radioimmunoassay. The antibody was capable of blocking the attachment of gonococci to epithelial cells. A slight antibody response was also demonstrated to gonococcal lipopolysaccharide but the antibody responsible for blocking attachment of gonococci was directed entirely at the pilus protein. The stimulated antibodies were shown to crossreact with isolated pili of heterologous gonococcal strains and to block the attachment of heterologous gonococci. Absorption of immune sera by a heterologous pilus reduced the inhibition of attachment antibodies to pre-immune level, suggesting that the immune response was directed at a common pilus determinant.

DNA vaccines.

Preclinical DNA vaccine development has continued apace during the past year, with the investigation of several new infectious and non-infectious disease targets as well as advances in our understanding of some of the basic immunologic mechanisms, such as effector cells, responsible for conferring protection. The coming year promises to be at least as exciting, as initial human clinical studies have begun.

Immunotoxins to a human melanoma-associated antigen: comparison of gelonin with ricin and other A chain conjugates.

Gelonin, a ribosome-inactivating protein from the seeds of Gelonium multiflorum, has been conjugated to antibodies. Previous reports have indicated variable potency of such immunotoxins. The lack of toxicity of gelonin, however, makes it attractive for immunoconjugate production. The ribosome-inactivating protein was covalently linked (using N-succinimidyl-3-(2-pyridyldithio)propionate) to monoclonal antibody, 9.2.27, directed to a human melanoma-associated glycoprotein/proteoglycan. The immunoconjugate showed high selectivity with dose-dependent cytotoxic activity to cultured human melanoma cells (50% inhibitory dose; 1-3 X 10(-11) M versus antigen-positive cells; 1-3 X 10(-7) M versus antigen-negative cells). Specificity and immunoreactivity of the conjugate were similar to those of unconjugated antibody. Biodistribution studies with iodine trace-labeled conjugate in nude mice indicated that tumor localization of the gelonin conjugate was decreased compared to unconjugated antibody. However, a significant therapeutic effect of the conjugate was found with multiple but not single dose i.v. treatment in nude mice bearing established palpable melanoma. These in vivo experiments showed that gelonin conjugates are not toxic up to 2 mg total dose/mouse and significantly retarded the growth of established s.c. tumor. Comparison of gelonin conjugates in vitro and in vivo with other A-chain conjugates of 9.2.27 (abrin and ricin) indicated that gelonin had similar potency, better selectivity, better tumor localization, and more significant therapeutic effects.

Immunotherapy of tularemia: characterization of a monoclonal antibody reactive with Francisella tularensis.

An IgM monoclonal antibody (mAb) recognized surface antigens specific to Francisella tularensis wild-type (Schu4) and live vaccine strain (LVS), and reacted with both in ELISA and slide agglutination tests. This mAb also reacted with LVS microorganisms in tissues of infected mice as assessed by an indirect fluorescence technique. Western blot analysis showed the mAb to react with antigens associated with F. tularensis LPS.

Reduced myocardial cyclic GMP increases myocardial O2 consumption in control but not renal hypertension-induced cardiac hypertrophy.

OBJECTIVES: We tested the hypothesis that a reduction in myocardial cyclic GMP would increase myocardial O2 consumption and that renal hypertension (One Kidney-One Clip, 1K1C)-induced cardiac hypertrophy would change this relationship. METHODS: Either vehicle or LY83583 (10(-3) M, a guanylate cyclase inhibitor) was topically applied to the left ventricular surface of control of 1K1C anesthetized open-chest New Zealand white rabbits (N = 38). Coronary blood flow (radioactive microspheres) and O2 extraction (microspectrophotometry) were used to determine subepicardial (EPI) and subendocardial (ENDO) O2 consumption and myocardial cyclic GMP was determined by radioimmunoassay. RESULTS: The heart weight/body weight ratio was greater in the 1K1C rabbits (3.16 +/- 0.20) than controls (2.58 +/- 0.08 g/kg). Systolic blood pressure was higher in 1K1C rabbits (116 +/- 8 mm Hg) than controls (80 +/- 6), but topical LY83583 had no significant hemodynamic effects. LY83583 significantly and similarly decreased EPI cyclic GMP in both control (7.9 +/- 1.2 to 6.0 +/- 1.0 pmol/g) and 1K1C (7.7 +/- 1.2 to 5.3 +/- 0.9) hearts and control ENDO (8.7 +/- 1.7 to 7.2 +/- 1.2) but not 1K1C ENDO (6.7 +/- 0.5 to 5.7 +/- 1.1). Myocardial O2 consumption was significantly increased in control with LY83583 (EPI 6.6 +/- 1.1 to 15.6 +/- 1.4 and ENDO 7.2 +/- 0.9 to 14.2 +/- 0.7 ml O2/min/100 g), but not in 1K1C hearts (EPI 12.1 +/- 1.0 to 12.9 +/- 1.2 or ENDO 11.4 +/- 0.7 to 12.9 +/- 0.9). CONCLUSIONS: Thus myocardial O2 consumption was only increased by LY83583 in control hearts, but LY83583 decreased cyclic GMP similarly in both the control and 1K1C EPI. This indicated, at least in the EPI, a dissociation of the inverse relationship between the myocardial level of cyclic GMP and O2 consumption in the 1K1C rabbit heart.

A double-blind, randomised, placebo-controlled, dose-finding trial of the novel tuberculosis vaccine AERAS-402, an adenovirus-vectored fusion protein, in healthy, BCG-vaccinated infants.

BACKGROUND: Several novel tuberculosis vaccines are currently in clinical trials, including AERAS-402, an adenovector encoding a fusion protein of Mycobacterium tuberculosis antigens 85A, 85B, and TB10.4. A multicentred trial of AERAS-402 safety and immunogenicity in healthy infants was conducted in three countries in sub-Saharan Africa, using an adaptive design. METHODS: In a double-blind, randomised, placebo-controlled, dose-finding trial, we enrolled BCG-vaccinated, HIV-uninfected infants aged 16-26 weeks. Infants in the safety/dose-finding phase received two doses of AERAS-402 across three dose levels, or placebo, intramuscularly on days 0 and 28. Infants in the expanded safety phase received three doses of the highest dose level, with the 3rd dose at day 280. Follow up for safety and immunogenicity was for up to two years. RESULTS: We enrolled 206 infants (52 placebo and 154 AERAS-402 recipients) into the dose-finding phase and 281 (141 placebo and 140 AERAS-402 recipients) into the expanded safety phase. Safety data were acceptable across all dose levels. No vaccine-related deaths were recorded. A single serious adverse event of tachypnoea was deemed related to study vaccine. Antibodies directed largely against Ag85A and Ag85B were detected. Low magnitude CD4+ and CD8+ polyfunctional T cell responses were observed at all dose levels. The addition of a third dose of AERAS-402 at the highest dose level did not increase frequency or magnitude of antibody or CD8+ T cell responses. CONCLUSIONS: AERAS-402 has an acceptable safety profile in infants and was well tolerated at all dose levels. Response rate was lower than previously seen in BCG vaccinated adults, and frequency and magnitude of antigen-specific T cells were not increased by a third dose of vaccine.

Immunoenzymatic analysis by monoclonal antibodies of bacterial lipopolysaccharides after transfer to nitrocellulose.

A rapid, sensitive immunoenzymatic technique for the analysis of lipopolysaccharide (LPS) from gram-negative bacteria using monoclonal antibodies is described. After separation by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, the LPS was either stained with silver or electrophoretically transferred to nitrocellulose. After reaction with anti-LPS monoclonal antibodies, the transferred antigens were visualized by reaction with alkaline-phosphatase-labelled anti-mouse antibodies and a substrate containing naphthol phosphoric acid and Fast Red.

Preparation of proteosome-based vaccines. Correlation of immunogenicity with physical characteristics.

In order to facilitate the use of proteosome-based vaccines, we have identified and analyzed the parameters that affect their immunogenicity. As a model system we used synthetic peptides (LCF6) containing sequences from the immunodominant (NANP)n tandem repeat region of the P. falciparum circumsporozoite protein, hydrophobically complexed to multimeric protein preparations (proteosomes) of meningococcal outer membrane proteins (OMP), since we have previously shown that high levels of anti-(NANP)n IgG can be elicited in mice by use of this novel adjuvant system (Lowell et al., 1988a). We have now examined these preparations by velocity sedimentation and measured their ability to elicit an IgG response in mice. Velocity sedimentation of freshly mixed OMP and LCF6, without dialysis, produced a limited number of small complexes, whereas dialysis of the mixture for 4 d yielded heterogeneously sized complexes that became more homogeneous when the dialysis was carried out for 7 or 10 days. The most homogeneous of these peptide-proteosome complexes (those dialyzed for 10 days) induced substantial levels of anti-(NANP)n IgG in mice, and shorter periods of dialysis resulted in vaccines that induced proportionately lower titers. Analysis of a series of preparations with varying LCF6: OMP ratios (w/w) showed that the degree of peptide substitution of the proteosomes was inversely proportional to the rate of sedimentation of the complexes and that there exists an optimal degree of lipopeptide complexing to the proteosomes. Our results suggest that the parameters affecting the immunogenicity of the peptide-proteosome complexes are: (i) hapten density, and (ii) size of the complex. Furthermore, sedimentation analysis of peptide-proteosome immunogens may serve as a rapidly performed assay of immunogenic potency.

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.