Protection of macaques against simian AIDS by immunization with a recombinant vaccinia virus expressing the envelope glycoproteins of simian type D retrovirus

Simian AIDS (SAIDS) is an endemic disease of macaques that shares many characteristics with AIDS in humans. SAIDS is etiologically linked to infection by a type D retrovirus, SAIDS retrovirus (SRV). Immunization with an inactivated whole-virus vaccine was shown to protect macaques against infection by SRV serotype 1. To identify the antigen(s) responsible for eliciting protective immunity, we have constructed a recombinant vaccinia virus (v-senv5) that expresses the envelope glycoproteins of SRV serotype 2 (SRV-2/W). Pig-tailed macaques (Macaca nemestrina) immunized with v-senv5 showed lymphoproliferative responses to purified SRV-2/W. They also generated antibodies that neutralized SRV-2/W infectivity in vitro and mediated antibody-dependent cellular cytotoxicity against SRV-2-infected cells. Four v-senv5-immunized animals, together with four control animals, were challenged intravenously with 5 x 10(3) tissue culture infectious doses of SRV-2/W. As early as 2 weeks after challenge, three of four control animals became viremic, and two of these three animals also seroconverted. The animal that was viremic but remained antibody negative died of symptoms of SRV infection 6 1/2 weeks after challenge. In contrast, all four v-senv5-immunized animals remained healthy, virus-free, and seropositive against only the immunizing envelope antigens. These results indicate that immunization with a recombinant vaccinia virus expressing the envelope antigens of SRV-2/W protects primates from infection by a retrovirus that causes immunodeficiency diseases.

Inward current in single smooth muscle cells of the guinea pig taenia coli

Using the tight-seal voltage-clamp method, the ionic currents in the enzymatically dispersed single smooth muscle cells of the guinea pig taenia coli have been studied. In a physiological medium containing 3 mM Ca2+, the cells are gently tapering spindles, averaging 201 (length) x 8 microns (largest diameter in center of cell), with a volume of 5 pl. The average cell capacitance is 50 pF, and the specific membrane capacitance 1.15 microF/cm2. The input impedance of the resting cell is 1-2 G omega. Spatially uniform voltage-control prevails after the first 400 microseconds. There is much overlap of the inward and outward currents, but the inward current can be isolated by applying Cs+ internally to block all potassium currents. The inward current is carried by Ca2+. Activation begins at approximately -30 mV, maximum ICa occurs at +10-+20 mV, and the reversal potential is approximately +75 mV. The Ca2+ channel is permeable to Sr2+ and Ba2+, and to Cs+ moving outwards, but not to Na+ moving inwards. Activation and deactivation are very rapid at approximately 33 degrees C, with time-constants of less than 1 ms. Inactivation has a complex time course, resolvable into three exponential components, with average time constants (at 0 mV) of 7, 45, and 400 ms, which are affected differently by voltage. Steady-state inactivation is half-maximal at -30 mV for all components combined, but -36 mV for the fast component and -26 and -23 mV for the other two components. The presence of multiple forms of Ca2+ channel is inferred from the inactivation characteristics, not from activation properties. Recovery of the fast channel occurs with a time-constant of 72 ms (at +10 mV). Ca2+ influx during an action potential can transfer approximately 9 pC of charge, which could elevate intracellular Ca2+ concentration adequately for various physiological functions.

Outward current in single smooth muscle cells of the guinea pig taenia coli

In single myocytes of the guinea pig taenia coli, dispersed by enzymatic digestion, the late outward current is carried by K+. It has both a Ca2+-activated component and a voltage-dependent component which is resistant to external Co2+. The reversal potential is -84 mV, and the channel(s) for it are highly selective to K+. At 33 degrees C, the activation follows n2 kinetics, with a voltage-dependent time constant of 10.6 ms at 0 mV, which shortens to 1.7 ms at +70 mV. Deactivation follows a single-exponential time course, with a voltage-dependent time constant of 11 ms at -50 mV, which lengthens to 33 ms at -20 mV. During a 4.5-s maintained depolarization, IK inactivates, most of it into two exponential components, but there is a small noninactivating residue. It is surmised that during an action potential under physiological conditions, there is sufficient IK to cause repolarization.

Diamphidia toxin, the bushmen's arrow poison: possible mechanism of prey-killing

The effects of a 60,000 mol. wt protein from the pupae of the beetle, Diamphidia nigro-ornata have been studied. In concentrations as high as 50 micrograms/ml, the toxin has little effect on the propagated compound action potential of isolated nerve trunks, or on the voltage-gated sodium and potassium channels of voltage-clamped single skeletal muscle fibers. In the anesthetized cat, the toxin has no specific effect on the neuro-muscular or the cardiovascular systems. It has a markedly hemolytic effect, and could reduce hemoglobin levels by as much as 75%. Plasma hemoglobin is increased, with resultant extensive hemoglobinuria and associated histopathological changes in the kidneys. Blood pressure, heart rate, PO2, PCO2, and oxygen-saturation remain essentially normal until the terminal stages of intoxication. Contrary to previous conclusions, we find no support for any particular neurotoxicity of the poison. The complex systemic effects, and possibly the prey-killing, can probably be attributed to the extensive hemolysis, reduced oxygen-carrying capacity, and generalized tissue hypoxia.

Factors associated with the decline of the Cooperative Medical System and barefoot doctors in rural China

The Cooperative Medical System (CMS) and its barefoot doctors have been in decline in rural China for nearly a decade. In order to explore the reasons for this, in 1987 we carried out a survey of villagers, barefoot doctors, and local administrators in Fengxian, Shanggoa, and Loaan counties, where incomes are good, fair, and low, respectively. The state of the CMS in these counties was contrasted and the situations which prevailed in 1978, 1982, and 1985, when the system was, respectively, at its peak, had begun to decline, and had declined markedly, were compared. A random sample of villages was selected and all the barefoot doctors and administrators as well as a random sample of households were surveyed. The results indicate that health status (as measured by infant mortality, immunization coverage, and rate of infectious diseases) has decreased in areas where the CMS has declined, while per capita incomes increased. Concomitantly, villager's expenditures on health care have increased. Barefoot doctors and their patients were, however, reasonably happy with the system, and in its absence the doctors are no longer able to obtain ongoing training. The CMS was fiscally sound, and did not decline to the same extent in all areas--it continues to thrive in Fengxian, which is relatively affluent. It is concluded that the system probably declined because many local administrators perceived that it no longer enjoyed the backing of the central government.

Effects of anti-gp120 monoclonal antibodies on CD4 receptor binding by the env protein of human immunodeficiency virus type 1

Monoclonal antibodies (MAbs) to defined peptide epitopes on gp120 from human immunodeficiency virus type 1 were used to investigate the involvement of their epitopes in gp120 binding to the CD4 receptor. Recombinant vaccinia viruses were constructed that expressed either full-length gp120 (v-ED6), or a truncated gp120 lacking 44 amino acids at the carboxyl terminus (v-ED4). Binding of these glycoproteins to the CD4 receptor was detected directly with metabolically labeled gp120 or indirectly with the gp120 MAbs. Truncated gp120 from v-ED4 bound to CD4-positive cells less than 1/12 as well as gp120 from v-ED6, indicating that the C-terminal region of gp120, which is conserved in numerous isolates of human immunodeficiency virus type 1, is critical for CD4 binding. However, MAb 110-1, which recognizes a peptide contained in the region deleted from v-ED4 (amino acids 489 through 511), did not inhibit binding of gp120 to CD4. MAb 110-1 also reacted with gp120 bound to the CD4 receptor, indicating that the epitope for this antibody does not directly interact with CD4. A second MAb, 110-4, which recognizes a peptide epitope located between amino acids 303 and 323 and has potent viral neutralizing activity, also bound to gp120 on the CD4 receptor. Furthermore, pretreatment of gp120 with MAb 110-4 at concentrations approximately 1,000-fold higher than those required for complete virus neutralization inhibited subsequent CD4 binding by only about 65%. Taken together, these data suggest that neutralization mediated by antibody 110-4 does not result from binding of this MAb to the CD4-binding site of gp120.

Recombinant vaccinia virus vaccine against the human melanoma antigen p97 for use in immunotherapy

We have constructed a recombinant vaccinia virus, v-p97NY, which expresses the human melanoma-associated glycoprotein p97. Immunization with v-p97NY could induce humoral and cell-mediated immunity to p97, including delayed-type hypersensitivity, in mice and in two of two monkeys (Macaca fascicularis). The fact that an immune response was induced also in monkeys is important because normal cells from monkeys, but not from mice, express a low level of cross-reactive p97. Mice immunized with v-p97NY rejected transplants of syngeneic mouse melanoma expressing p97. A rejection response could be detected also when immunization was started 2 days after tumor transplantation, irrespective of whether the transplanted cells grew subcutaneously or as lung metastases. Evidence was obtained that melanoma cells lacking p97 may be killed as "bystanders" at the site of an immune response to melanoma cells expressing p97.

Optimal selection of a battery of tests: a multiobjective optimization methodology

The general problem of selecting a battery of tests for diagnostic purposes is discussed and multiobjective optimization methodology is applied to solve it, with battery selection being based on performance indices such as sensitivity, specificity, and the cost of testing. For a battery of tests, the extended majority rule is developed and used to interpret the compound test results. The major advantage of the model developed in this paper is that it can generate a set of noninferior batteries without requiring the calculation of all possible combinations of tests. An example in which the method is applied to a real problem--the selection of short-term tests to detect the carcinogenicity of chemicals--is discussed.

Characterization of a recombinant vaccinia virus expressing human melanoma-associated antigen p97

p97 is a cell surface glycoprotein expressed at high levels in most human melanomas but present only in trace amounts in normal adult tissues. We are interested in exploring the possibility of using recombinant vaccinia virus to express a specific tumor-associated antigen as a vaccine against human cancer. To this end, we constructed a recombinant virus, v-p97NY, which contains the entire coding sequence for p97 under the control of the vaccinia virus 7.5K promoter. Upon infection of tissue culture cells, v-p97NY expressed high levels of a membrane-bound glycoprotein immunoreactive with a p97-specific monoclonal antibody. Immunization of mice with this recombinant elicited high-titered antibodies against p97. Spleen cells isolated from these mice proliferated in vitro when stimulated either with purified p97 protein or with syngeneic cells expressing p97 antigen. Delayed-type hypersensitivity was also observed in immunized mice after challenge with p97-expressing cells. These findings indicate the potential usefulness of v-p97NY and similar recombinants in tumor immunotherapy.

Effect of immunization with a vaccinia-HIV env recombinant on HIV infection of chimpanzees

Acquired immunodeficiency syndrome (AIDS) is caused by human immunodeficiency virus (HIV) and is now recognized as a worldwide epidemic for which there is no cure or vaccine. Chimpanzees are the only other animals that can be infected by HIV, and therefore the chimpanzee-HIV model system is useful for testing potential HIV vaccines. However, with one exception, there have been no reports of clinical manifestations of AIDS in chimpanzees. We report here results of an HIV vaccine trial in which nine chimpanzees were first immunized with either a recombinant vaccinia virus expressing the envelope glycoproteins of HIV strain LAV-1 (v-env5) or a control recombinant vaccinia virus and were then challenged with a high or low dose of LAV-1. Although HIV-specific antibody and T-cell responses were elicited by immunization, virus was isolated from lymphocytes of all challenged chimpanzees, indicating that immunization did not prevent infection by HIV. Among the animals that received a higher dose of LAV-1, one of two control chimpanzees, but none of the four v-env5-immunized chimpanzees developed substantial and persistent lymphadenopathy.

Proliferative and cytotoxic T cells to AIDS virus glycoproteins in chimpanzees immunized with a recombinant vaccinia virus expressing AIDS virus envelope glycoproteins

PBL from chimpanzees immunized with a recombinant vaccinia virus that expresses HIV envelope glycoproteins ("env"), were found to proliferate after stimulation with HIV or with "env". Furthermore, CTL clones lytic for autologous target cells expressing HIV envelope glycoproteins were generated after stimulation of the chimpanzees' PBL with "env", indicating that immunization of these primates with a recombinant vaccinia virus primes HIV-specific CTL and also that HIV envelope glycoproteins serve as target antigens for CTL.

Proliferative and cytotoxic T cells to AIDS virus glycoproteins in chimpanzees immunized with a recombinant vaccinia virus expressing AIDS virus envelope glycoproteins

PBL from chimpanzees immunized with a recombinant vaccinia virus that expresses HIV envelope glycoproteins ("env"), were found to proliferate after stimulation with HIV or with "env". Furthermore, CTL clones lytic for autologous target cells expressing HIV envelope glycoproteins were generated after stimulation of the chimpanzees' PBL with "env", indicating that immunization of these primates with a recombinant vaccinia virus primes HIV-specific CTL and also that HIV envelope glycoproteins serve as target antigens for CTL.

Expression of the human immunodeficiency virus gag gene in insect cells

Regions of the gag-pol gene of human immunodeficiency virus (HIV), the causative agent of AIDS, have been cloned into the polyhedrin gene of the baculovirus Autographa californica nuclear polyhedrosis virus. When these recombinant viruses were used to infect insect cells, the cells produced gag-related proteins which could be immunoprecipitated with serum from AIDS patients. The major proteins produced by Acgag1, which contained the entire gag gene and a small portion of the pol gene, had molecular weights of 55,000 and 40,000 Da. Acgag2, which contained a larger portion of the pol gene in addition to the gag coding sequences, produced a major protein of 24,000 Da and only minor amounts of the 55,000- and 40,000-Da proteins. The implications of these results with respect to proteolytic processing of HIV gag proteins as well as the potential diagnostic use of this system are discussed.

Synthesis of an active hybrid growth factor (GF) in bacteria: transforming GF-alpha/vaccinia GF fusion protein

A hybrid gene encoding for a polypeptide consisting of the first 33 N-terminal amino acid (aa) residues of transforming growth factor-alpha (TGF-alpha) and a C terminus consisting of 20 aa residues of vaccinia growth factor (VGF) was chemically synthesized and expressed as a fusion protein in Escherichia coli. The primary structure of the hybrid gene product maintained the same positioning of the three disulfide bonds found in each parent molecule thus conserving the first two loop regions of TGF-alpha and the third loop region of VGF. After cleavage with CNBr its renatured biological activity was found to be comparable to TGF-alpha and VGF with respect to binding to the epidermal growth factor receptor, stimulation of DNA synthesis and induction of anchorage-independent growth of NRK cells in the presence of TGF-beta. Thus, we suggest that similar domains can be interchanged within the same family of molecules and equivalent functionality maintained.

The genome of Shope fibroma virus, a tumorigenic poxvirus, contains a growth factor gene with sequence similarity to those encoding epidermal growth factor and transforming growth factor alpha

Degenerate oligonucleotide probes corresponding to a highly conserved region common to epidermal growth factor, transforming growth factor alpha, and vaccinia growth factor were used to identify a novel growth factor gene in the Shope fibroma virus genome. Sequence analysis indicates that the Shope fibroma growth factor is a distinct new member of this family of growth factors.

Inaction of saxitoxin-oximes on the sodium channel of frog skeletal muscle fibers

Three oximes of saxitoxin, saxitoxin oxime, saxitoxin methyloxime, and saxitoxin carboxymethyloxime, were synthesized in which the oxime functions replaced the ketone function on C-12 of saxitoxin. On the voltage-clamped single frog muscle fibers these oximes were very weak or inactive in blocking the sodium channel. The results indicate that the hydrated ketone function in saxitoxin is essential for blockade of the sodium channel, probably through a hydrogen bonding mechanism with some receptor groups.

T-cell responses to human AIDS virus in macaques immunized with recombinant vaccinia viruses

There is much interest in developing vaccines against acquired immune deficiency syndrome (AIDS), which is caused by a retrovirus termed human immunodeficiency virus (HIV). Isolates of this virus include human T-lymphotropic virus type III (HTLV-III), lymphadenopathy-associated virus (LAV), and AIDS-associated retrovirus (ARV). Several approaches towards the development of an AIDS vaccine result in the production of antibodies in subprimates. These methods involve the use of: antigens isolated from the AIDS virus; viral antigens expressed by transfected cells or by recombinant vaccinia viruses; and particular synthetic peptides of viral antigens. Because T-cell-mediated immunity (in addition to antibodies) is involved in resistance to diseases and death caused by various enveloped viruses, we sought to determine whether potential AIDS vaccines can induce T-cell responses against the AIDS virus. Here we report that immunization of non-human primates, Macaca fascicularis (macaques), with recombinant vaccinia viruses that express LAV envelope glycoproteins gp41 and gp110 results not only in the production of antibodies against the LAV envelope antigens but also in the generation of T-cells that proliferate and produce the lymphokine interleukin-2 (IL-2), in response to stimulation with purified LAV. We believe this is the first report demonstrating T-cell-mediated immunity to the virus that causes AIDS.

Expression of AIDS virus envelope gene in recombinant vaccinia viruses

Acquired immune deficiency syndrome (AIDS) is an infectious disease characterized by severe impairment of the patient's cell-mediated immune system. Several lines of evidence have indicated that the aetiological agent of AIDS is a group of T-lymphotropic retroviruses, variously known as lymphadenopathy-associated virus (LAV), human T-lymphotropic virus type III (HTLV-III) and AIDS-associated retrovirus (ARV). Serological surveys have indicated that as many as one million people in the United States may have been infected by LAV/HTLV-III, and the spread of AIDS has become a global concern. The need for a better understanding of the viral immunology and for a vaccine against AIDS is self-evident. To this end, we have constructed recombinant vaccinia viruses containing the envelope (env) gene of LAV, and demonstrate here that cells infected with these viruses express immunoreactive proteins similar to those present on LAV virions. Experimental animals infected with these recombinant viruses elicited antibodies that specifically recognized LAV envelope proteins.

Chemical and enzymatic biotin-labeling of oligodeoxyribonucleotides

Biotin has been converted to 2-(biotinylamido)ethanol and condensed to phosphorylated oligonucleotides in a solid phase synthesis. The 5'-biotinylated oligonucleotides were enzymatically coupled to other DNA fragments by T4 DNA ligase or T4 RNA ligase. The hybridization properties of such biotin-labeled oligonucleotide probes were studied.

Hemagglutination-inhibiting antibody in hemorrhagic fever with renal syndrome

Hemagglutination activity was demonstrated in a Hantaan virus antigen prepared from infected suckling mouse brain by sucrose-acetone extraction. Hemagglutination of goose erythrocytes was pH dependent and was optimal at pH 6.0-6.2. Immunofluorescent and hemagglutination-inhibiting antibodies were significantly correlated in 80 human and 13 animal sera. Hemagglutination-inhibiting antibody was present in some patients 20 years after the onset of hemorrhagic fever with renal syndrome. The hemagglutination inhibition test was useful for confirming that an insectivore, Suncus murinus, may be an animal reservoir host of a Hantaan-like virus.

Restriction analysis and homology studies of the bovine adenovirus 7 genome

We located the cleavage sites for restriction endonucleases EcoRI, HindIII, and BamHI on the genome of bovine adenovirus 7. Cross-hybridization at reduced stringency revealed two regions of homology shared by the DNA of human adenovirus 2 and bovine adenoviruses 7 and 3. These regions correspond to the hexon and the IVa2 protein genes of the human adenovirus. Another region of homology shared only by the human adenovirus and bovine adenovirus 7 corresponded to the penton or the polypeptide IIIa genes. These results allowed us to align the restriction map of bovine adenovirus 7 with respect to the other adenoviruses.

Effects of chemical modification of amino and sulfhydryl groups on the voltage-clamped frog node of Ranvier

Several reagents that react with sulfhydryl and amino groups were applied to voltage-clamped single nerve fibres of the frog. The fibres were exposed to comparable amounts of the chemical reagents for relatively short times. 3-(p-Hydroxyphenyl)propionic acid N-hydroxysuccinimide ester (HPPS), a substance which preferentially modifies amino groups, irreversibly reduced the size of the sodium and potassium current. The effect of HPPS on the Na current could be removed only partially by hyperpolarizing prepulses. N-ethylmaleimide (NEM), a reagent that preferentially reacts with sulfhydryl groups produced a small decrease of the sodium current which was removed almost completely by hyperpolarizing prepulses. NEM and HPPS shifted the voltage dependence of sodium inactivation, h infinity (E), to more negative values of membrane potential, but had little effect on the time course of sodium activation and inactivation. Pretreatment of a fibre with NEM did not prevent the action of HPPS; however, pretreatment of a fibre with HPPS decreased considerably the shift of the h infinity (E) curve caused by NEM. Our results suggest that modification of membrane bound amino groups affects the size of the ionic currents and the inactivation process. Although reagents that react with sulfhydryl groups were found to affect channel function, no definite evidence for the presence or absence of a functionally important sulfhydryl group on sodium channels has been obtained.

Sequence homology between bovine and human adenoviruses

Cross-hybridization has been detected between corresponding regions of the genomes of bovine adenovirus type 3 and human adenovirus type 2. The most conserved region on the viral genomes encodes the hexon polypeptide. The nucleotide sequence of this region in bovine adenovirus type 3 has been determined. Comparison of the predicted amino acid sequences of the bovine adenovirus type 3 and human adenovirus type 2 hexon polypeptides reveals three regions of nonhomology.

Translational control of SV40 T antigen expressed from the adenovirus late promoter

We have constructed four novel adenovirus-SV40 hybrid viruses that contain the SV40 A gene at different positions downstream from the adenoviral major late promoter, within the region that encodes the second and third segments of the late tripartite RNA leader. The SV40 insert was precisely positioned in preselected regions of the adenoviral genome by using a combination of in vitro and in vivo recombination. As expected, all four recombinants produce equally high levels of SV40-encoded RNA that initiates at the adenovirus late promoter and contains two or three leader segments at the 5' end. Yet, in spite of this efficient transcription, only one virus, Ad-SVR284, directs the synthesis of high levels of SV40 large T antigen in infected cells; the other recombinants all produce approximately 20-fold less T antigen. This differential expression is, however, not seen in vitro, where equal amounts of hybrid T mRNA direct the synthesis of equal amounts of SV40 T antigen. Thus, some form of translational regulation is present in adenovirus-infected cells that is missing from the in vitro translation reaction.

DNA sequence required for initiation of transcription in vitro from the major late promoter of adenovirus 2

We have identified a region of the viral genome required for the initiation of transcription in vitro from the major late promoter of adenovirus 2. A fragment of the adenovirus genome containing the cap site of the major late transcripts was inserted into plasmid pBR322 and cloned. Deletions were then generated in vitro in and around the T-A-T-A-A-A-A sequence located 25-31 nucleotides (positions -25 to -31) upstream from the cap site. DNAs with these deletions were tested for their ability to initiate transcription in vitro by the method of Manley et al. [Manley, J. L., Fire, A., Cano, A., Sharp, P. A. & Gefter, M. L. (1980) Proc. Natl. Acad. Sci. USA 77, 3855-3859]. Whereas removal of sequences upstream from position -47 or downstream from position -12 did not abolish transcription, deletions extending into, or beyond, the T-A-T-A-A-A-A sequence reduced transcription to less than 1/10th. Removal of the normal cap site slightly reduced, but did not abolish, transcription. These results indicate that the region of the genome upstream of the cap site, with boundaries within 15-17 nucleotides to either side of the T-A-T-A-A-A-A sequence, is required for the initiation of transcription in vitro from the major late promoter of adenovirus 2.

Integration of viral DNA sequences in cells transformed by adenovirus 2 or SV40

We have cloned and propagated in prokaryotic vectors the viral DNA sequences that are integrated in a variety of cells transformed by adenovirus 2 or SV40. Analysis of the clones reveals that the viral DNA sequences sometimes are arranged in a simple fashion, collinear with the viral genome; in other cell lines there are complex arrangements of viral sequences in which tracts of the viral genome are inverted with respect to each other. In several cases the nucleotide sequences at the joints between cell and viral sequences have been determined: usually there is a sharp transition between cellular and viral DNAs. The viral sequences are integrated at different locations within the genomes of different cell lines; likewise there is no specific site on the viral genomes at which integration occurs. Sometimes the viral sequences are integrated within repetitive cellular DNA, and sometimes within unique sequences. In some cases there is evidence that the viral sequences along with the flanking cell DNA have been amplified after integration. The sequences that flank the viral insertion in the line of SV40-transformed rat cells known as 14B have been used as probes to isolate, from untransformed rat cells, clones that carry the region of the chromosome in which integration occurred. Analysis of the structure of these clones by restriction endonculease digestion and heteroduplex formation shows that a rearrangement of cellular sequences has occurred, presumably as a consequence of integration.

4S oop RNA is a leader sequence for the immunity-establishment transcription in coliphage lambda

oop RNA, which is initiated at the po promoter and is 81 nucleotides long, can function as a leader sequence for the lambda immunity establishment transcription, previously believed to originate at a special promoter pre located in the y region. Thus, oop RNA seems to have a dual role, either favouring the lytic cycle as a primer for the initiation of lambda DNA replication, or leading to the establishment of lysogeny when elongated into the imm transcript, which directs synthesis of the repressor.