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Background Death in patients with chikungunya is rare and has been associated with encephalitis, hemorrhage, and septic shock. We describe clinical, histologic, and immunohistochemical findings in individuals who died following chikungunya virus (CHIKV) infection. Methods We identified individuals who died in Puerto Rico during 2014 following an acute illness and had CHIKV RNA detected by reverse transcriptase–polymerase chain reaction in a pre- or postmortem blood or tissue specimen. We performed histopathology and immunohistochemistry (IHC) for CHIKV antigen on tissue specimens and collected medical data via record review and family interviews. Results Thirty CHIKV-infected fatal cases were identified (0.8/100 000 population). The median age was 61 years (range: 6 days–86 years), and 19 (63%) were male. Death occurred a median of 4 days (range: 1–29) after illness onset. Nearly all (93%) had at least 1 comorbidity, most frequently hypertension, diabetes, or obesity. Nine had severe comorbidities (eg, chronic heart or kidney disease, sickle cell anemia) or coinfection (eg, leptospirosis). Among 24 fatal cases with tissue specimens, 11 (46%) were positive by IHC. CHIKV antigen was most frequently detected in mesenchymal tissues and mononuclear cells including tissue macrophages, blood mononuclear cells, splenic follicular dendritic cells, and Kupffer cells. Common histopathologic findings were intra-alveolar hemorrhage and edema in the lung, chronic or acute tenosynovitis, and increased immunoblasts in the spleen. CHIKV infection likely caused fatal septic shock in 2 patients. Conclusions Evaluation of tissue specimens provided insights into the pathogenesis of CHIKV, which may rarely result in septic shock and other severe manifestations.

Postmortem examination results of a patient with Guillain-Barré syndrome and confirmed Zika virus infection revealed demyelination of the sciatic and cranial IV nerves, providing evidence of the acute demyelinating inflammatory polyneuropathy Guillain-Barré syndrome variant. Lack of evidence of Zika virus in nervous tissue suggests that pathophysiology was antibody mediated without neurotropism.

Our long-term goal is to discover the combination of host parameters that help some HIV-infected individuals to resist progression to AIDS. In this study, we examined antibody responses using multiple samples obtained from a cohort of Long-Term Non-Progressors (LTNPs). Our hypothesis is that antibody responses to variable regions of the HIV-1 envelope glycoprotein are involved in reducing the viral load associated with LTNPs and that these specific immune responses influence susceptibility to disease progression. Multiple plasma samples were obtained from patients identified as LTNPs with the objective of characterizing humoral immune response directed to the five hypervariable regions of the envelope glycoprotein. Antibody binding was tested against peptides representing the five hypervariable regions of gp120, as well as against analog peptides representing different isolates of HIV-1 and against recombinant envelope glycoprotein. LTNPs have specific antibodies to the hypervariable regions of the envelope glycoprotein and develop different patterns of antibody recognition to variable epitopes of envelope glycoprotein. These antibodies can be detected using HIV peptides as capture antigens.

Successful development of an effective HIV vaccine hasn’t occurred yet partly as a consequence of the antigenic variation deployed by HIV-1 to escape the immune system. Our laboratory is dedicated to develop a single peptide synthesis approach to crea te multivalent peptides representing hypervariable epitopes of the gp120 envelope glycoprotein of HIV- 1. Our previous study showed that our HIV HECs are potent immunogens that activate both humoral and cellular arms of the acquired immune response and that these responses are broadly reactive, reco gnizing epitopes from divergent strains of HIV-1. T o detect the long term duration of memory response in duced by HIV HECs, two rhesus macaques were immunized at weeks 0 and 8 and euthanized two weeks after a third immunization at week 393 (more than 8 years later). Antibody response to individua l components of HIV HEC immunogens and HIV HEC-induced cross-reactive antibody response were determined by an Enzyme-Linked Immunosorbent Assay (ELISA). The antibody titer to individual HIV HEC components and a mixture of the five peptides was greater than 1:5000 dilution. Antibodies from H IV HEC-immunized macaques recognized HIV HEC analogs representing the monovalent epitopes of fiv e variable regions of gp120 from subtype B HIV-1 MN, HIV-1 RF and HIV-1 SF2 isolates with an antibody titer greater than 1: 500 dilution. Moreover, lymphocytes from lymph nodes of HIV HEC-immunized macaques showed T cell proliferative responses specific to HIV HEC individual components and to the five HIV HEC peptides combined. Our results clearly show that in these two macaques, HIV HECs induced strong, long-lasting anamnestic immune responses 8 years after immunization.

Despite the extensive efforts towards development of an effective HIV vaccine, major challenges surrounding vaccine design still exist. We have previously developed a unique multivalent HIV-1 candidate vaccine representing hypervariable Gp120 and Gag regions. This candidate vaccine was able to induce a broad cell-mediated immune response in HLA-A2.1 mice and non-human primates against HIV-1 subtypes A–F. Herein, the reactivity of each hypervariable peptide mixture within our candidate peptide vaccine was further characterized to optimize the final vaccine formulation for the future clinical studies. The binding of each hypervariable region to sera from HIV-infected individuals demonstrated a strong reactivity between the antibodies and hypervariable regions. In addition, 15 groups of mice were immunized with adjuvant alone or each individual peptide mixture (lipidated or non-lipidated) to evaluate the ability of each variable region to induce humoral and cellular immune responses against HIV-1. A reactive HIV-1 specific immune response was detected among the immunized groups; however, mice receiving the Gag hypervariable regions demonstrated the highest frequency of cell-mediated immune responses.

Introduction: In Mozambique clinical staging may be the primary determinant of HIV / AIDS treatment decisions and the task of staging commonly falls to nonphysician clinicians (tecnicos de medicina). Two years after the first Mozambican tecnicos were trained in HIV / AIDS care the quality of their performance in clinical staging was unknown. Methods: Expert clinicians observed 127 clinical encounters conducted by a randomly selected national sample of 44 tecnicos and compared observed clinical staging decisions to World Health Organization and Mozambican national norms. They also reviewed relevant Mozambican in-service training curricula in HIV / AIDS care. Results: Observers agreed with fewer than half (44.1%) of the tecnicos’ stage-defining diagnoses. Misclassification or misdiagnosis of 3 complaints (weight loss fever and diarrhea) accounted for the majority of the observed errors. Review of health worker curricula determined that observed staging errors reflected content errors and omissions in the tecnicos’ in-service HIV / AIDS training and constraints in local laboratory and imaging capacity. Discussion: In response to these findings the Mozambican Ministry of Health has revised the tecnicos’ scope of work and has developed new guidelines curriculum materials and training strategies to improve the quality of clinical staging and opportunistic infection diagnosis in Mozambique.

Human immunodeficiency virus type 2 (HIV-2) evolved from the zoonotic transmission of simian immunodeficiency virus (SIV) that naturally infects sooty mangabeys found in West Africa. Using sera from HIV-2–infected humans, we discovered that an hypervariable region (the V4 loop) of HIV- 2 induces antibody responses only weakly reactive against itself but strongly reactive against analogous sequences from the V4 loop of strains of SIV. Available sequence data indicates that all strains of HIV-2 have large deletions in the V4 region that truncate an immunodominant neutralizing B cell epitope among strains of SIV. Infection of a macaque with a sequenced clone of HIV-2 similarly elicited antibodies that poorly recognized the V4 loop of HIV-2 but readily bound to analogous SIV sequences. Our data are consistent with a scenario whereby a disparate antibody response directed against the V4 loop may have influenced the selective expansion and survival of HIV-2 in humans.

An ideal prophylactic vaccine against human papillomaviruses (HPV) would be one that can induce broadly reactive antibody titres to at least the major oncogenic strains of HPV. It has been previously shown that HPV structural proteins are highly immunogenic but fail to elicit cross-reactive immune responses against heterologous strains of HPV. Recent studies have demonstrated that the immunity induced by virus-like particles is mostly type specific. In the present study, we determined the breadth of reactivity of antibodies induced in mice immunized with hypervariable epitope constructs (HECs), which represent sequence variants of immunodominant B-cell epitopes of the major capsid protein L1 of HPV. In order to test the breadth of reactivity, sera from immunized mice were tested against peptides representing analogous sequences of HPV types 16, 18, 31 and 45. Mice immunized with HECs based on two epitopes mounted antibody responses that cross-reacted with two different analogues, 16 and 18. Significantly, antibodies from mice immunized with HECs also inhibited haemagglutination mediated by HPV-16 L1 VLPs, suggesting that immunization resulted in the development of antibodies that could bind to viral capsid proteins in their native conformation. Our observations suggest that HECs may overcome the restriction of type specific immunity against HPV.

Previous studies have demonstrated the fibrinolitic and antibacterial activities of proteins from the earthworm Eisenia foetida (Ef) but their use as a food supplement for animals and humans is still being considered. We studied proteins from this worm in order to determine chemical composition (protein, fat and heavy metal levels), electrophoretic profile in SDS-PAGE and 2D gels, induction of humoral immune response in mice and toxicity in a human cell line. Chemical analysis revealed 61.8, 11.3 and 8.7 g% of proteins, fat and ash, respectively. Levels of heavy metals were low and similar to tunny fish. Sixteen bands were obtained by SDS-PAGE with a molecular weigh range of 6.9–205 kDa while twenty-three spots were observed following 2D gel electrophoresis. After three immunizations with Eisenia foetida lysate, high titer antibodies were produced without causing immediate hypersensitivity reactions. Good cell viability was observed when Ef proteins were added to a human cell line. These results suggest t...

Methadone, a regimen for the treatment of opioid dependency, was found to induce the expression of CCR5, a co-receptor for human immunodeficiency virus (HIV)/simian form of HIV (SIV) entry, on human CEM x174 lymphocytes. Both CCR5 mRNA and protein were elevated in methadone-treated cells. A concomitant increase of mu opioid receptors was also observed. Upon methadone exposure, SIVmac239-infected CEM x174 cells released greater amounts of virus particles as revealed by both the number of syncytia formation and reverse transcriptase activities. Similar methadone effect was not observed on CEM x174 cells infected with other simian retroviruses that do not depend on CCR5 for cellular entry. These studies raise concerns considering methadone as an innocuous morphine substitute.

The identification of several simian immunodeficiency virus mac251 (SIVmac251) cytotoxic T-lymphocyte epitopes recognized by CD8+T cells of infected rhesus macaques carrying the Mamu-A*01 molecule and the use of peptide-major histocompatibility complex tetrameric complexes enable the study of the frequency, breadth, functionality, and distribution of virus-specific CD8+T cells in the body. To begin to address these issues, we have performed a pilot study to measure the virus-specific CD8+and CD4+T-cell response in the blood, lymph nodes, spleen, and gastrointestinal lymphoid tissues of eight Mamu-A*01-positive macaques, six of those infected with SIVmac251and two infected with the pathogenic simian-human immunodeficiency virus KU2. We focused on the analysis of the response to peptide p11C, C-M (Gag 181), since it was predominant in most tissues of all macaques. Five macaques restricted viral replication effectively, whereas the remaining three failed to control viremia and experienced a progressive loss of CD4+T cells. The frequency of the Gag 181 (p11C, C→M) immunodominant response varied among different tissues of the same animal and in the same tissues from different animals. We found that the functionality of this virus-specific CD8+T-cell population could not be assumed based on the ability to specifically bind to the Gag 181 tetramer, particularly in the mucosal tissues of some of the macaques infected by SIVmac251that were progressing to disease. Overall, the functionality of CD8+tetramer-binding T cells in tissues assessed by either measurement of cytolytic activity or the ability of these cells to produce gamma interferon or tumor necrosis factor alpha was low and was even lower in the mucosal tissue than in blood or spleen of some SIVmac251-infected animals that failed to control viremia. The data obtained in this pilot study lead to the hypothesis that disease progression may be associated with loss of virus-specific CD8+T-cell function.

Original antigenic sin describes a phenomenon in which the antibody response elicited in an individual after a secondary viral infection reacts more strongly to the viral variant that originally infected the individual. As T helper cells play critical roles in promoting antibody responses, a similar phenomenon may hold true for T helper cell responses. This concept is particularly relevant to the development of vaccines against viruses such as human immunodeficiency virus and hepatitis C virus, in which myriad viral variants are present throughout the human population. We have compared the effects of priming the immune system with a single peptide epitope or with a cocktail of related peptides based on the epitope. Our data demonstrate that immunization with multiple peptide variants expands a more broadly reactive and durable T helper cell response than does immunization with a single peptide. This vaccine strategy may circumvent original antigenic sin.

Staphylococcus aureus are gram-positive bacteria that can cause serious diseases in humans and animals. S. aureus infections can be prevented by the heptapeptide RNAIII inhibiting peptide (RIP). RIP was originally isolated from culture supernatants of coagulase negative staphylococci presumed to be S. xylosus. The sequence of RIP was identified as YSPXTNF. Native RIP and its synthetic analogue YSPWTNF have been shown to be effective inhibitors of diseases caused by various strains of S. aureus, including, cellulitis, keratitis, septic arthritis, osteomylitis and mastitis. RIP is therefore considered to be a global inhibitor of S. aureus. We show here that: 1) the amide form of RIP (YSPWTNF-NH2) is highly stable and is therefore the one recommended for use. 2) RIP inhibits S. aureus pathogenesis by inhibiting the synthesis of both agr transcripts RNAII and RNAIII. 3) Although RIP inhibits agr, it also reduces bacterial adherence to mammalian cells and to plastic (tested on HEp2 cells and on polystyrene by fluorescence and atomic force microscopy), suggesting that RIP can be used safely as a therapeutic molecule. 4) RIP derivatives were designed and tested for their ability to inhibit RNAIII in vitro and cellulitis in vivo. Not all peptides that inhibited RNAIII also inhibited an infection in vivo, indicating that studies must be carried out in vivo before considering a peptide to be of therapeutic potential. 5) The RIP derivative containing Lysine and Isoleucine at positions 2 and 4, respectively, inhibited S. aureus infections in vivo (tested on cellulitis), suggesting that both RIP YSPWTNF and its derivative YKPITNF are effective inhibitors of infections caused by S. aureus.

In an effort to evaluate the feasibility of developing a safe DNA vaccine for acquired immunodeficiency syndrome (AIDS), we have prepared a plasmid-based immunogen modeled after a naturally occurring noninfectious mutant of the simian immunodeficiency virus (SIV). The mutant SIV genome produces defective virus particles that are noninfectious in vitro and nonpathogenic in vivo in rhesus macaques. Analysis of the mutant genome revealed a 1.6 kb deletion that is in frame and spans integrase, vif, vpx, and most of vpr and results in a pol/vpr gene fusion. This deletion was introduced into the parental pathogenic molecular clone and the U3 region of the 5' LTR was replaced with a cytomegalovirus promoter to produce a candidate DNA vaccine, pIV. After transfection with this plasmid, SIV gag and envelope proteins are expressed and properly processed in vitro. When injected into rabbits, pIV elicited an antibody response to SIV gp130 envelope glycoprotein with titers reaching 1:2048, and a strong lymphoproliferative response to SIV gp130 and whole SIV. The potential to produce defective virus particles in vivo without integrating into the host genome should result in both a strong humoral and cellular immune response in rhesus macaques. In addition, this approach offers a safe alternative to live attenuated vaccines and DNA vaccines that are capable of integration.

Development of an effective preventive or therapeutic vaccine against HIV-1 is an important goal in the fight against AIDS. Effective virus clearance and inhibition of spread to target organs depends principally on the cellular immune response. Therefore, a vaccine against HIV-1 should elicit virus-specific cytotoxic lymphocyte (CTL) responses to eliminate the virus during the cell-associated stages of its life cycle. The vaccine should also be capable of inducing immunity at the mucosal surfaces, the primary route of transmission. Recombinant Bacille Calmette–Guerin (BCG) expressing viral proteins offers an excellent candidate vaccine in view of its safety and ability to persist intracellularly, resulting in the induction of long-lasting immunity and stimulation of the cellular immune response. BCG can be administered orally to induce HIV-specific immunity at the mucosal surfaces. The immunogenicity of four recombinant BCG constructs expressing simian immunodeficiency virus (SIV) Gag, Pol, Env, and Nef proteins was tested in rhesus macaques. A single simultaneous inoculation of all four recombinants elicited SIV-specific IgA and IgG antibody, and cellular immune responses, including CTL and helper T cell proliferation. Our results demonstrate that BCG recombinant vectors can induce concomitant humoral and cellular immune responses to the major proteins of SIV.

Variability of the major antigenic sites of the envelope glycoprotein of HIV-1 constitutes a major problem in the formulation of effective vaccines. We have prepared a synthetic peptide vaccine that represents the major hypervariable epitopes (V1 through V5) of the clade B HIV-1 envelope glycoprotein (gp120). We refer to this preparation as variable epitope immunogen or VEI vaccine. This construct takes into consideration the type and frequency of amino acid substitutions found at each epitope during the evolution of the virus in individual patients and in the target population. Immunization of mice, rabbits, and rhesus macaques with the VEI vaccine resulted in the induction of long-lasting, high-titered HIV-1 antibodies, including antibodies that neutralize primary isolates. We also documented lymphocyte proliferative responses to the VEI vaccine, its individual components, analogs, and subtype-specific peptides representing the major hypervariable regions of HIV-1 gp120. Delayed-type hypersensitivity responses to these antigens were also demonstrated in mice. Our results show that this vaccine is highly immunogenic and safe in animals. Our data suggest that this formulation could become an important component of combination vaccine approaches against HIV-1 and other antigenically variable pathogens.

Effect of Human Immunodeficiency Virus Type 1 on Intracellular Activation and Superoxide Production by Neutrophils (Muñoz, José F.; Salmen, Siham; Berrueta, Lisbeth R.; Cova, José A.; Donis, José H.; Hernández, Manuel R. and Torres, José V.) Abstract The immunopathogenesis of AIDS is associated with the development of opportunistic infections by intracellular pathogens that can invade and reproduce freely because of impaired cellular functions. Neutrophils from asymptomatic human immunodeficiency virus (HIV) type 1-infected persons and from symptomatic patients with AIDS were found to retain normal phagocytosis activity while producing significantly less superoxide than neutrophils fromHIV-1-negative subjects, when stimulated through Fc receptors or protein kinase C. After priming with a synthetic HIV-1 envelope peptide and stimulation via the Fc receptor, the neutrophils from HIV-1-negative controls had suppressed superoxide production, reduced phosphorylation of two unidentified cellular proteins, and increased expression of a third phosphoprotein. These results suggest that HIV-1 can produce direct functional damage of neutrophils through binding of envelope components to the cell membrane. Artículo publicado en: The Journal of Infectious Diseases 1999; 180:206-10. munozjose@hotmail.com donis@ula.ve sihamsa@ula.ve lberruet@ula.ve jvtorres@ucdavis.edu Nivel monográfico

Vaccines are not universal in their ability to induce favorable immune responses in all individuals because the major histocompatibility complex (MHC) molecules needed for presentation of vaccine components to T cells are limited in the peptides they recognize and bind. A heterogeneous cocktail of related peptides synthesized simultaneously and representing amino acids 414-434 of the SIV envelope protein was used to induce immune responses stronger than those induced by a single T cell peptide synthesized conventionally and representing the same region of the viral envelope. The heterogeneous peptide mixture called a hypervariable epitope construct (HEC) was capable of overcoming MHC restriction in peptide presentation in four different inbred mouse strains, including a strain that was a poor responder to the AA 414-434 single sequence peptide (SSP). HEC induced proliferation responses 15 times better than those induced by SSP. Antibodies elicited by HEC but not SSP immunization effectively bind viral antigen. The 414-434 HEC and the 414-434 SSP were also tested for their ability to upregulate the expression of MHC class I molecules on the surface of the mutant RMA-S murine cell line. Surface display of MHC molecules was measured by confocal microscopy followed by calculation of fluorescence intensity of images. HECs upregulated expression of MHC molecules 30% more than SSP peptides. Our findings suggest that HEC cocktails could be effective components of subunit vaccines to help overcome the unresponsiveness observed in outbred animals and in humans as a result of MHC-restricted antigen presentation.

Type D simian retroviruses (SRV) cause an acquired immunodeficiency syndrome (AIDS) in monkeys. Results of infection with SRV range from complete recovery with absence of viremia to a viremic state, which produces AIDS-like symptoms and culminates in death. These varied outcomes render the interaction of the host and SRV an attractive model for the study of immunosuppressive retrovirus resulting in different pathologic consequences. We describe here the isolation and determination of the molecular weight of the receptor for SRV. We demonstrate that a cell receptor with the same molecular weight is bound by the envelope protein of all five serotypes of SRV. We also show that the receptor recognizes a region containing amino acids 142-167 of the envelope protein of SRV serotype 1 (SRV-1). In addition, we show that a different region of SRV serotype 2 (SRV-2) envelope protein containing amino acids 93-106, interacts with a cell receptor of identical molecular weight. Furthermore, polyclonal and monoclonal antibodies that are directed to envelope epitopes 142-167 of SRV-1 or to 93-106 of SRV-2, specifically neutralize only the respective viral serotype. Our results indicate that the neutralization of SRV infectivity by antibodies is achieved through blocking the interaction between the virus and its cell receptor.

CD4 ligation of HIV envelope gp120 results in conformational changes in gp120 that lead to exposure of the gp41 fusogenic domain and fusion with the host cell membrane. One determinant at or near the CD4-binding site exposed on gp120 subsequent to CD4 binding is defined by two human MAbs termed 17b and 48d. These MAbs do not block CD4 binding to gp120; rather, their binding to gp120 is upregulated following CD4 binding. To determine if synthetic peptide mimetopes could be found that reflect conformational determinants on the surface of gp120, synthetic gp120 peptides from 10 divergent HIV isolates were screened for their ability to bind to 17b and 48d in ELISAs. Although MAb 48d binds to HIV IIIB recombinant gp120 protein, in our studies 48d selectively bound only to the HIV Can0A V3 peptide and not to HIV IIIB V3 peptide, whereas MAb 17b bound none of the peptides tested. Monoclonal antibody 48d bound to the HIV Can0A V3 peptide both in solid-phase ELISA and in solution in a competitive ELISA, but could not bind to HIV Can0A V3 peptide bound to human T cells. The HIV Can0A V3 peptide induced anti-HIV antibodies in rhesus monkeys that neutralized the laboratory-adapted HIV MN strain but did not induce antibodies that neutralized HIV IIIB/LAI, HIV SF-2, or HIV RF isolates, or that neutralized HIV primary isolates. These data suggested that the primary sequence of the HIV Can0A V3 loop exists in a conformer that mimicks a non-V3 determinant of native gp120 exposed subsequent to CD4 binding on the surface of gp120 of laboratory-adapted HIV strains. Structural studies of the Can0A V3 peptide and/or the 48d MAb may provide important information regarding the nature of gp120 conformational changes that occur following gp120 ligation by CD4.

Our understanding of the immune responses to pancreatic tumors is very limited. Analysis of the preexisting immune responses against a panel of tumor-associated antigens could help generate new immune-based therapies and diagnostic tools. Furthermore, the majority of the few studied tumor-associated antigens found in pancreatic cancer are not clinically relevant or important for cancer cell survival. Animal and clinical immunotherapeutic studies have demonstrated that there is immune selection and immune escape against most of these antigens. Overactivation of the epidermal growth factor pathway, apoptosis-related proteins and death resistance of cancer stem cells and tumor stroma have been observed in human pancreatic cancer and often are associated to overexpression or deregulation of several proteins including EGFR, Her-2, Bcl-2, survivin, Wnt-1, and Sox2. EGFR, Her-2, Bcl-2, survivin, Wnt-1, and Sox2 are implicated in tumor aggressiveness, progression, resistance, and metastasis. Overexpression of these proteins in the tumor cells and tumor stroma of advanced pancreatic cancer, and the lack of relevant mutations make them reliable targets for clinical immunotherapy trials. We designed long peptides representing immunogenic T helper and CTL epitopes for all these six proteins. The immune response was studied in pancreatic cancer (n=15), pancreatitis (n=17) and matched controls. PBMCs were analyzed to determine Th1 and Th2 immune response by production of IFN-γ and IL-10 respectively using an ELISPOT assay. Sera and ascites fluid were used for the study of the humoral immune response by ELISA using human anti-IgG and human anti-IgA. We detected significant preexisting humoral and cellular immune responses against these peptides in patients suffering from advanced pancreatic cancer. In this study, we demonstrated that this panel of proteins could be targets for humoral and cellular immune recognition in pancreatic cancer patients whereas no detectable responses were found in healthy patients. Our results suggest that a Th2 immune response is present more often in this cohort and that it could be associated with a poor prognosis measured by overall survival. In conclusion, Th2 and ascites IgA immune responses against proteins important for tumor survival that are overexpressed in cancer cells and tumor stroma were common in our cohort of pancreatic cancer patients. Some of these proteins could serve as broad-spectrum tumor antigens to target in peptide vaccine immunotherapy trials to achieve better clinically relevant responses in pancreatic cancer patients. Citation Format: Jose V. Torres, Gardner B. Murray, Ramon Cabello, Eduardo Flores, Alejandro Camacho, Pedro A. Lucero, Anton Ostashko, Roger Dela Cruz, Jr., Fernando Durazo, Xia Li, Lizette Rodriguez, Erik Ramos, Juan Pablo Marquez-Manriquez. Preexisting immune responses against EGFR, Her-2, Bcl-2, survivin, Wnt-1, and Sox2 in pancreatic cancer patients. [abstract]. In: Proceedings of the AACR Special Conference on Pancreatic Cancer: Progress and Challenges; Jun 18-21, 2012; Lake Tahoe, NV. Philadelphia (PA): AACR; Cancer Res 2012;72(12 Suppl):Abstract nr A54.

Human papillomavirus (HPV) is associated with premalignant lesions such as high-grade cervical intraepithelial neoplasia (CIN-III) with potential progression to cervical carcinoma. There are now preventive vaccines against HPV. However, no effective therapeutic vaccine or immunological treatment exists for individuals already infected or for the 470,000 women that develop high-grade dysplasia, carcinoma in situ, and cervical cancer each year. More than half of these women die from cervical cancer. Relative non-immunogenicity of HPV infection is one of the main reasons for the difficulty in designing a comprehensive therapeutic vaccine against HPV-induced premalignant lesions and cervical carcinoma. HPV E6 and E7 proteins, the major HPV oncogenes, are highly immunogenic but fail to induce cross-reactive and protective immune responses against heterologous strains. We designed and synthesized a therapeutic peptide vaccine comprised of multivalent peptide mixtures called hypervariable epitope constructs (HECs) that represent the major epitope variants of the oncogenic E7 structural protein, and assessed their immunogenicity and in vivo efficacy in mice. Our results show that this peptide vaccine can induce strong, HPV-specific, T-helper cell and CTL responses. More significantly, we have demonstrated that the vaccine is efficacious as a therapeutic agent in a mouse HPV tumor model. Therefore, the HPV HEC vaccine approach described herein can potentially prevent progression of HPV-associated premalignant lesions, and may also be therapeutic against tumors associated with HPV.

Epitope variability is one of the greatest obstacles to development of synthetic peptide vaccines. Based on a recently described hypervariable epitope (aa 414–434) on the envelope glycoprotein (gp130) to simian immunodeficiency virus (SIV mac 142), we have developed a novel approach to account for epitope variability. We have prepared, in a single synthesis, a cocktail of peptides, designated a hypervariable epitope construct (HEC), which collectively represent all the in vivo variability seen in an epitope. The HEC represents permutations of amino acid substitutions found in the epitope and has been able to induce antibodies with enhanced binding to native SIV and broad immunoreactivity to related epitope analogues.

These studies defined SRV-2 envelope peptides 96-102, 127-152, and 233-249 as T cell epitopes that induce significant T cell proliferation. Peripheral blood lymphocytes of Celebes macaques (Macaca nigra) exposed to SRV-2 and currently virus- antibody+, cultured with SRV-2 virus show strongly suppressed T cell responses and have two immunoregulatory T cell populations.

We analyzed SIV-specific monkey sera to localize B-cell epitopes of the envelope glycoprotein of SIV (gp130), using overlapping synthetic peptides representing the entire SIV gp130 protein and sera from experimentally infected monkeys and monkeys immunized with whole, inactivated SIV. A B-cell epitope which induces neutralizing antibody production and T-cell responses was characterized as well as a new B-cell epitope and a previously described neutralizing epitopes. Vaccinated monkey sera recognize the three epitopes differentially relative to unimmunized controls, and a correlation appears to exist between degree of cross-neutralization by infected monkey sera and degree of binding to these three regions.

Address: 1Variation Biotechnologies Inc., 1740 Woodroffe Ave, Building 400, Ottawa, ON, K2G 3R8, Canada, 2Department of Biochemistry, Microbiology and Immunology, University of Ottawa, and Infectious Disease and Vaccine Research Center, Children's Hospital of Eastern Ontario Research Institute, 401 Smyth, Ottawa, ON, K1H 8L1, Canada, 3Department of Pathology and Laboratory Medicine, University of Ottawa, 451 Smyth, Ottawa, ON, K1H 8M5, Canada and 4Department of Medical Microbiology and Immunology, Davis School of Medicine, University of California, Davis, CA 95616, USA * Corresponding author

Synthetic envelope peptides of a simian retrovirus (SRV-2) were used to define both T- and B-cell epitopes of the envelope protein. The SRV-2 peptide 100-106 specifically blocks rhesus anti-SRV-2 neutralizing antibody activity, and a peptide 100-106 keyhole limpet hemocyanin conjugate induces a strong antipeptide antibody response. SRV-2 peptide 100-106 and 233-249 induces good T-cell proliferation of murine spleen cells immunized with the SRV-2 virus. Thus, SRV-2 envelope peptide 100-106 represents both a T- and B-cell epitope, and peptide 233-249 a T-cell epitope.

We previously demonstrated that the area encompassing residues 147-162 of the envelope protein of simian retrovirus serotype-1 (SRV-1) is the target for rhesus anti-SRV-1 neutralizing antibodies. A peptide representing amino acids 142-167 of envelope protein (gp70) is capable of inducing virus-neutralizing antibodies in mice. The virus receptor was immunoprecipitated from Raji cells using gp70 as the ligand. Antibodies to peptide 142-167 inhibit the immunoprecipitation, indicating that the receptor recognizes residues 142-167 of the viral envelope protein.

Post-mortem medical examiner samples may be useful for sentinel surveillance of disorders usually detected by antibody determinations on specimens from ill patients or from surveys. We found anti-dengue IgM positivity in 3% (23/780) and anti-dengue IgG positivity in 77% (597/777) of sera obtained at the Puerto Rico medical examiner (Institute of Forensic Sciences) in December 2000, April 2001, and October 2001. This approach may be a useful alternative for estimating the population prevalence of serologic markers for dengue and other infectious diseases.

Using simian immunodeficiency virus (SIV) infection of rhesus macaques to model human immunodeficiency virus (HIV) infection of humans, we assessed whether broadly reactive vaccine-induced humoral immunity would remain broadly reactive after viral challenge, and whether there would be significant differences in anamnestic antibody responses if animals were challenged when predominately effector or memory lymphocyte populations were present. Animals immunized over a prolonged period and challenged 11 months after vaccination mounted more broadly reactive and stronger humoral immunity than those rapidly vaccinated and challenged 2 weeks after their final vaccinations. These data suggest that vaccination schedule and the timing of virus challenge should be considered when evaluating future candidate HIV vaccines.

Sexually transmitted diseases (STDs) caused by bacteria and protozoa play an important role in the epidemiology of human immunodeficiency virus (HIV-1) infection. Human trichomoniasis, produced by the protozoan parasite Trichomonas vaginalis, is one of the most common STDs, and is a cause of mucosal lesions in the urogenital tract, which may increase the risk for HIV infection. However, there are no reports concerning the outcome of in vitro interactions between HIV particles and trichomonads. Therefore, we incubated T. vaginalis with three subtypes of HIV-1 (A, B, and D), as well as with HIV-1-infected lymphocytes, and analyzed the interactions with immunofluorescence microscopy and transmission electron microscopy. Our results demonstrated that HIV-1 particles attach and are incorporated into T. vaginalis through endocytic vesicles and are degraded within cytoplasmic vacuoles in approximately 48 h. There was no ultrastructural evidence of HIV-1 replication in trichomonads. These results demonstrated that trichomonads may internalize and harbor HIV-1 particles for short periods of time. In addition, under in vitro conditions, T. vaginalis ingests and digests HIV-1-infected lymphocytes.

Cellular immunity against multiple Hepatitis C virus (HCV) proteins is observed in patients acutely infected with HCV most of whom later resolve infection. We wished to assess humoral immunity in patients infected with HCV 1a or 1b genotypes in relation to viral load using plasma samples from HCV-infected individuals and a panel of peptides representing immunodominant epitopes of HCV structural and nonstructural proteins. Plasma from HCV 1a- and 1b-infected patients, respectively, were divided into two groups: patients with low viral load (≤100,000 RNA copies/ml) and patients with high viral load (≥10,000,000 RNA copies/ml). The antigens were peptides representing epitopes from immunodominant regions of HCV core, E2, NS3, and NS4 proteins, as well as the hypervariable (HVR) epitopes in E2 from genotypes 1a and 1b. Individuals infected with HCV 1a evoked a stronger immune response to many immunodominant epitopes of HCV relative to individuals infected with HCV 1b. Moreover, among individuals infected with HCV 1a, those with low viral loads mounted significantly greater responses against these epitopes than did individuals with high viral loads. Our observations demonstrate that quantitatively different antibody responses are elicited against HCV depending on the genotype of infecting virus, and suggest that humoral immunity directed against multiple immunodominant epitopes in HCV 1a-infected individuals may help lower viral load in vivo.

A versatile DNA vaccine (pdIV3) was constructed by replacing the integrase, vif, vpx, and vpr genes of a pathogenic simian immunodeficiency virus (SIV) molecular clone with a linker containing unique cloning sites. The 5' long terminal repeat (LTR) is truncated and transcription is controlled by a cytomegalovirus (CMV) promoter. The construct expresses Gag and Env in vitro and noninfectious virus particles are produced from transfected cells. The ability of pdIV3 to promote cellular and humoral immune responses, along with the flexibility of the linker design to allow insertion of immunostimulatory genes in future constructs, makes this a useful base vector for immunization against primate lentiviruses. We present the construction of a retroviral plasmid designed to serve as a template for the development of safe and effective vaccines against primate immunodeficiency retroviruses. This vaccine component should facilitate the simultaneous induction of cellular and humoral immune responses that protect primates against infection with SIV and human immunodeficiency virus (HIV) and the development of acquired immune deficiency syndrome (AIDS). This plasmid could induce the appropriate immune response required to attack both cell-free and cell-associated viruses. The lack of infectivity, the inability to integrate, and the SIV origin make this construct a safe alternative to attenuated vaccines based on HIV. In addition, we intend to develop this construct as an immunotherapeutic approach to lower the viremia in AIDS patients.

Staphylococcus aureus causes many diseases including cellulitis, keratitis, osteomyelitis, septic arthritis and mastitis. The heptapeptide RIP has been shown to prevent cellulitis in mice, which was induced by S. aureus strain Smith diffuse. Here we show that RIP can also significantly reduce the overall pathology and delay the onset of disease symptoms in several other models of S. aureus infections, including: keratitis (tested in rabbits against S. aureus 8325-4), osteomyelitis (tested in rabbits against S. aureus MS), mastitis (tested in cows against S. aureus Newbould 305, AE-1, and environmental infections) and septic arthritis (tested in mice against S. aureus LS-1). These findings substantiate that RIP is not strain specific in its inhibitory activity and that RIP is an effective inhibitor of bacterial pathology at multiple body sites following diverse routes and doses of administration. These findings strongly evidence the potential value of RIP as a chemotherapeutic agent.

All HIV-1 strains studied to date use CCR5, CXCR4, or both receptors to enter cells. Simian immunodeficiency virus (SIV) infection of non-human primates has served as a useful model for understanding AIDS pathogenesis in humans. Research on several genetically divergent SIV isolates has revealed that SIV uses CCR5, and not CXCR4, for entry. CEM x174, a human lymphoid cell line, has been routinely used to cultivate and maintain various SIV strains. However, questions have arisen about how CEM x174, which reportedly was unable to express detectable amounts of CCR5 transcripts, efficiently supports the growth of SIV. In searching for an answer, we resorted to a sensitive competitive reverse transcriptase-polymerase chain reaction procedure in an attempt to detect as well as quantify the amount of CCR5 expression. Here we present our findings, which indicate that CEM x174 indeed expresses CCR5 and that the amount of CCR5 is increased in cells pretreated with morphine. These results correlate well with our previous observations that morphine treatment causes CEM x174 cells to be more susceptible to SIV infection. Similar morphine effect was not observed on CEM x174 cells infected with simian retroviruses, which do not depend on CCR5 for entry. These findings suggest a plausible mechanism whereby opiate drug users render themselves more susceptible to HIV infection, thereby explaining the vast prevalence of HIV infection among endemic drug use populations.

Immunogenic peptides containing epitopes of the gp120 C4 and V3 regions from human immunodeficiency virus strains MN and EV91 have been studied by nuclear magnetic resonance and molecular modeling and used as immunogens in rhesus monkeys. The results, combined with those for other peptides, suggest a correlation between solution conformation and immunologic cross-reactivity.

Using synthetic peptides, we developed an approach to account for protein epitope variability. We have prepared, in a single synthesis, a cocktail of peptides we have designated a hypervariable epitope construct (HEC), which collectively represents much of the in vivo variability seen in an epitope. Eight HECs representing the in vivo variability seen throughout the envelope glycoprotein of the simian immunodeficiency virus (SIV) were designed and synthesized. The constructs were collectively conjugated to KLH (HEC-KLH) or recombinant gp130 (HEC-rgp130) and used to immunize rabbits and rhesus macaques, respectively. Using sera collected from rabbits immunized with HEC-KLH, we demonstrated that individual components of the immunogen were recognized as antigen in ELISAs, and that the induced antibodies cross-reacted with several strains of SIV as well as with a strain of HIV-2. Following immunization of macaques with HEC-rgp130 antiviral antibodies were induced. These antibodies were still present 9.5 months after the last boost and were also capable of recognizing several different strains of SIV, including SIVmac239, SIVmac251, and SIVsmH3, as well as a strain of HIV-2 (HIV-2ROD). In addition, the antibodies were also capable of neutralizing SIV viral infectivity in vitro. Peripheral blood lymphocytes (PBLs) from immunized macaques proliferated in response to whole proteins and virus. Finally, sera from monkeys immunized with SIV, rgp130, and HIV-2 as well as sera from HIV-2-positive humans recognized HECs in ELISAs, demonstrating the relevance of these epitopes in vivo. This approach can be used as an effective method for generating a strong, broadly cross-reactive humoral response against HIV and can serve as an important component of combination vaccines against HIV and AIDS.

Objective: To demonstrate that antibodies against amino acids (aa) 603-622 of the SIV gp41 transmembrane glycoprotein enhance infection of SIV in vivo. Design: A synthetic peptide derived from aa 603-622 of SIVmac251 gp41 was synthesized and tested for immunogenicity in rabbits and SIV-infected rhesus macaques. Next, SIV-naive animals were immunized with either a recombinant vaccinia virus expressing the SIV gp160 envelope glycoprotein (VVrgp160) and boosted three times with aa 603-622 (group 1,four animals), wild-type vaccinia virus and boosted with aa 603-622 (group 2, two animals), or VVrgp160 followed by three doses of an irrelevant peptide (group 3, two animals). Animals were challenged with SIVmac251. Results: Peptide aa 603-622 was immunogenic in rabbits. SIV-infected rhesus monkeys immunized with the peptide developed two-three log increases in antibodies to this peptide and antibodies that could enhance SIV infection in vitro. SIV-naive rhesus macaques in group 1 had higher levels of antibody to the peptide by enzyme-linked immunosorbent assay and higher levels of enhancing antibodies at the time of SIV challenge than the animals in groups 2 or 3. Following challenge with SIVmac251 the group 1 animals had detectable p27 antigen longer than animals in group 2 and 3 and died of simian AIDS before the respective animals in the two control groups (P Conclusions: aa 603-622 of SIV gp41, like aa 579-613 of HIV gp41, can stimulate production of antibodies that enhance SIV and HIV infection in vitro. Furthermore, immunization with this peptide suppressed beneficial effects of a gp160 vaccine and appeared to enhance SIV infection in vivo.

Ovine progressive pneumonia virus (OPPV) is a lentivirus which causes a progressive disease in sheep. Immunodominant epitopes have been identified in the envelope gp40 glycoprotein. Synthetic peptides representing these regions are able to detect the presence of OPPV antibodies in 96% of infected sheep.

One hundred consecutive patients who died of the acquired immunodeficiency syndrome (AIDS) were studied with an emphasis on the heart. Thirty-two patients showed pathologic changes. The pathologic findings included infection by Histoplasma capsulatum, Toxoplasma gondii, Mycobacterium tuberculosis, cytomegalovirus, Cryptococcus neoformans, and atypical mycobacteria. Noninfectious pathologic findings included nonspecific myocarditis, focal necrosis, focal fibrosis, and acute subendocardial infarction.

SIVmac infection of macaques is an important animal model for HIV infection and AIDS; this model is being utilized for development of antiviral therapies and vaccines. In the present article, we sought to identify neutralization epitopes of SIVmac envelope surface glycoprotein (gp130). Algorithms were used to predict antigenicity of specific regions. Four regions from the primary amino acid sequence of the viral surface glycoprotein were selected. A synthetic peptide representing one of these regions (414-434) induced virus-neutralizing antibodies in mice; in addition, this peptide induced T cell-proliferative responses in macaques. To address the in vivo relevance of these observations, we demonstrated that experimentally infected macaques produce antibodies to the neutralization epitope. In addition, rhesus macaques protected against infection by an inactivated SIV vaccine develop antibodies that bind to peptide 414-434. These observations demonstrate that the region that includes the sequence 414-434 in the fourth variable domain (V4) of SIVmac gp130 contains both a linear neutralization epitope and a T cell epitope.

A simian type D retrovirus designated SRV induces a fatal immunosuppressive disease in rhesus macaques. This syndrome shows many clinical similarities to acquired immunodeficiency syndrome (AIDS) in human immunodeficiency virus-infected individuals. To investigate the mechanisms of immune dysfunction in SRV infection, we have focused on the interactions of SRV serotype 1 (SRV-1) with macaque B-lymphoblastoid cell lines (B-LCL). Procedures were optimized for establishing B-LCL by immortalization of macaque B lymphocytes with rhesus Epstein-Barr virus (EBV). These cell lines express B-cell surface markers, secrete immunoglobulins of the IgG or IgM isotypes, and release EBV which transforms monkey B cells. In vitro cultures of B-LCL supported replication of SRV-1. Several B-LCL infected with SRV-1 showed downregulation of major histocompatibility complex (MHC) class II antigen expression whereas levels of MHC class I antigen remained unchanged. Infection of B-LCL with SRV-1 did not alter the level of secreted immunoglobulin. Rhesus EBV was also used to obtain B-LCL from macaques infected with SRV-1; these cell lines were found to release infectious SRV-1. Investigations on the interactions of SRV-1 with B cells will be useful for elucidating mechanisms involved in the immunopathogenesis of primate retroviruses.

It has been recently demonstrated that two serotypes of type D simian retroviruses, namely SRV-1 and SRV-2, exhibit extensive immunological cross-reactivity but do not exhibit cross-reactivity at the level of neutralizing antibodies. We have also shown recently that an area which includes residues 147–162 of the envelope protein of SRV-1 constitutes an epitope to which neutralizing antibodies against SRV-1 but not against SRV-2 are directed. However, in spite of the capacity of various immunogenic preparations to induce antibodies which react with SRV-1 these antibodies were incapable of neutralizing in vitro viral infectivity. Work reported herein demonstrates that various immunogens consisting of a larger peptide, namely 142–167 of the envelope protein of SRV-1, induce antibodies capable of binding with the envelope protein of SRV-1 and with the whole virus. Moreover, these antibodies exhibit the capacity to neutralize in vitro the infectivity of SRV-1 but not of SRV-2.

An area encompassing residues 142-167 of the envelope protein of type D simian retrovirus (SRV-1) has been shown to contain the epitope to which neutralizing antibodies are directed. This area has been synthesized and shown to bind to monkey and mouse antiviral antibodies and to a virus neutralizing mouse monoclonal antibody. Protein conjugates of this peptide as well as the cross-linked or the free peptide induce antibodies capable of neutralizing, in vitro, viral infectivity. The cell receptor to the virus was isolated following extraction of Raji cells with non-ionic detergents. The receptor was isolated and characterized following radioimmuno-precipitation of 125I labeled cell extract bound to viral envelope protein. This immunoprecipitation could be inhibited by antiserum to peptide 142-167. Analysis in gels indicate that the receptor is of molecular weight of approximately 60 KDa. These results indicate that the neutralizing antibodies and the receptor recognize the same area on the viral envelope protein and that neutralization is the result of blocking the virus-receptor interaction by antibodies.

There are at least three distinct serotypes of simian type D retrovirus (SRV) which exhibit extensive serological cross-reactivity, but no cross-reactivity exists at the level of serum neutralizing antibodies. Amino acid sequence analysis and hydrophobicity plots of SRV-1 and SRV-2 envelope proteins were compared in order to identify unique potential antigenic determinants to which respective neutralizing antibodies may be directed. Peptides representing residues 147-162 of SRV-1 and 96-102 of SRV-2 were synthesized and assessed for their immunoreactivity. Free peptide inhibition of strain-specific serum (rhesus) neutralizing antibodies to SRV-1 and SRV-2 was demonstrated using the SRV-1 147-162 peptide and the SRV-2 peptide, 96-102, respectively. Inhibition of serum neutralizing activity by these peptides was also strain-specific, showing no cross-inhibition. SRV-1 147-162 conjugated to a protein carrier and cross-linked to Sepharose beads specifically adsorbed neutralizing antibodies from SRV-1 immune rhesus sera. The antibodies eluted from the immunoadsorbent possessed SRV-1 neutralizing activity, but showed no effect on the infectivity of SRV-2. Peptide SRV-1 147-162 also exhibited the capacity to bind specifically with a mouse monoclonal antibody which neutralizes the infectivity of SRV-1. Mice immunized with a recombinant SRV-1 envelope protein or with whole, inactivated SRV-1 produced antibodies which bound the SRV-1 147-162 conjugate, but not the protein carrier itself. Mouse antibodies to the SRV-1 147-162 conjugate exhibited specific binding with both native SRV-1 and with recombinant SRV-1 envelope protein. These findings provide strong evidence that SRV-1 147-162 and SRV-2 96-102 constitute at least two unique antigenic determinants, or parts thereof, which participate in the strain-specific neutralizing antibody response. Moreover, the findings indicate that the SRV-1 neutralizing antibodies produced by monkeys and at least a certain population of neutralizing antibodies produced by mice recognize the same epitope of SRV-1.

A major problem impeding development of an effective HIV vaccine is the rapid antigenic variability that is characteristic of several envelope glycoprotein epitopes. Frequent mutations alter the composition of the most immunogenic regions of the envelope glycoprotein. We have prepared a synthetic immunogen representing the evolution of the major hypervariable epitopes on the envelope glycoprotein (gp120) of HIV-1. Five synthetic constructs, representing each of the HIV-1 gp120 hypervariable epitopes were tested for recognition by antibodies from patients infected with HIV-1 from different geographic regions worldwide. An HIV-1 human plasma panel provided a representation of the antibodies recognizing subtype-specific epitope sequences prevalent at different parts of the world. The vaccine construct was recognized by antibodies from HIV-1-positive individuals infected with subtypes A, B, C, D, E, and F. Antibodies in pooled HIV-1 patient sera from San Francisco also recognized all five constructs. This complex immunogen was recognized by antibodies in sera from individual HIV-1-positive and AIDS patients from Puerto Rico and Canada, with a strong binding to the complete vaccine and the V3 component. Altogether, our results demonstrate that antibodies from seropositive patients infected with different HIV-1 clades recognize and bind to the HIV hypervariable epitope construct vaccine preparation and its individual components.

When influenza virus infection occurs, part of the cytotoxic T lymphocyte responses induced are directed to the major surface molecule of the virus, the hemagglutinin. However, despite their potential use as a peptide vaccine, little information is available concerning the submolecular areas in the hemagglutinin that are responsible for its immunologic recognition by cytotoxic T lymphocytes. The primary goal of this study is to determine whether submolecular areas recognized by antibodies and helper T cells are also important in the virus-specific, T lymphocyte-mediated cytotoxic responses generated towards virus-infected cells. A panel of synthetic peptides representing areas of the hemagglutinin, homologous to those in influenza AX-31 virus which have previously been shown to bind anti-influenza virus antibodies and provoke proliferation of virus-primed T-helper lymphocytes, was tested in two different cytotoxicity assays. In the experiments presented here, it was found that when selected peptides were incubated with appropriate L929 target cells, lysis by virus-specific cytotoxic T cells was observed. In addition, AX-31-primed lymphocytes preincubated with these synthetic peptides (both individually and as an equimolar mixture) exhibited enhanced lysis of virus-infected syngeneic targets. The cytotoxic responses showed dose-response characteristics in all cases, and in each of the two assays used the same patterns of cytotoxic induction were observed. The recognition of peptides was MHC-restricted since virus-specific cytotoxic T cells from C3H/He mice (H-2k) lysed L929 (H-2k) target cells after incubation with peptides or viruses, but did not lyse P815 (H-2d) targets under the same conditions.

Five peptides corresponding to four regions of the beta chain of human chorionic gonadotropin (hCG), were synthesized, purified and characterized. The four regions studied were selected on the basis of sequence differences between the beta chain of hCG (beta hCG) and the beta chains of related hormones. The peptides were found to bind rabbit and mouse anti-hCG antibodies as well as rabbit anti-beta chain antibodies, but did not bind antibodies against the alpha chain or against other hormones. All the peptides, even in their free form, were able to elicit high titer antisera in both rabbits and mice. In all cases, anti-peptide antisera bound to the immunizing peptide as well as to the native hCG and the isolated beta chain. These anti-peptide antisera did not bind to unrelated peptides, the alpha chain of hCG or to other hormones with very similar beta chains such as human luteotropic hormone (hLH), ovine luteotropic hormone (oLH) and equine chorionic gonadotropin (eCG). Since the areas represented by these peptides elicit antibodies that are specific for human beta hCG, they can formulate the basis for the development of discriminatory reagents for the beta chain of hCG.