Characterization of measles polypeptides by monoclonal antibodies

High affinity binding between Hsp70 and the C-terminal domain of the measles virus nucleoprotein requires an Hsp40 co-chaperone

The major inducible 70 kDa heat shock protein (hsp70) binds the measles virus (MeV) nucleocapsid with high affinity in an ATP-dependent manner, stimulating viral transcription and genome replication, and profoundly influencing virulence in mouse models of brain infection. Binding is mediated by two hydrophobic motifs (Box-2 and Box-3) located within the C-terminal domain (N(TAIL)) of the nucleocapsid protein, with N(TAIL) being an intrinsically disordered domain. The current work showed that high affinity hsp70 binding to N(TAIL) requires an hsp40 co-chaperone that interacts primarily with the hsp70 nucleotide binding domain (NBD) and displays no significant affinity for N(TAIL). Hsp40 directly enhanced hsp70 ATPase activity in an N(TAIL)-dependent manner, and formation of hsp40-hsp70-N(TAIL) intracellular complexes required the presence of N(TAIL) Box-2 and 3. Results are consistent with the functional interplay between hsp70 nucleotide and substrate binding domains (SBD), where ATP hydrolysis is rate limiting to high affinity binding to client proteins and is enhanced by hsp40. As such, hsp40 is an essential variable in understanding the outcome of MeV-hsp70 interactions.

Chapter 8 Paramyxoviruses

The paramyxoviruses are a heterogeneous group of viruses causing a variety of clinical diseases in humans, animals, and birds. This chapter examines in more detail the structure and properties of the important human viruses in this group, namely measles, respiratory syncytial virus (RSV), mumps and parainfluenza viruses I-V. They are all enveloped, negative-stranded, riboviruses of helical symmetry. It is suggested that susceptible children, adolescents, and adults should be vaccinated against mumps, unless vaccination is contraindicated. Mumps vaccine can be of particular value to children approaching puberty and for adolescents and adults, especially males who have not had mumps in childhood. Ribavirin therapy may be particularly beneficial for children at risk for severe and often fatal RSV infection, such as infants with congenital heart disease. Attenuated measles vaccines have been developed empirically by selection of host range mutants, and are widely and successfully used throughout the world. Using the vaccine, some countries may soon eliminate measles as an endogenous virus but continued problems are anticipated, particularly in adults with viruses re-introduced by visitors from abroad. Basic studies on new antivirals are continuing (particularly with oligopeptides) but antiviral compounds are unlikely to have extended use in the clinic, except perhaps in tropical areas where the disease may be life threatening. However, a vaccination programme in these areas is preferable, and is an urgent need.

Immunomodulatory properties of morbillivirus nucleoproteins

Morbillivirus infections have been known for a long time to be associated with an acute immunosuppression in their natural hosts. Here, we show that recombinant Morbillivirus nucleoproteins from canine distemper virus, peste-des-petits-ruminants virus, and Rinderpest virus bind B-lymphocytes from dogs, goats, and cattle, respectively, similarly to measles virus nucleoprotein in humans. The use of surface plasmon resonance imaging allowed the real time detection of differential interactions between Morbillivirus nucleoproteins and FcgammaRIIb (CD32). Moreover, those nucleoproteins which bind murine Fcgamma receptor inhibited the inflammatory immune responses in mice in a Fc receptor- dependent manner. In contrast, nucleoprotein from closely related Henipavirus genus, belonging to the Paramyxoviridae family as Morbillivirus, was devoid of capacity either to bind FcgammaRIIb or to inhibit inflammatory response. Altogether, these results suggest that nucleoprotein-FcR interaction is a common mechanism used by different Morbilliviruses to modulate the immune response.

Role of V protein RNA binding in inhibition of measles virus minigenome replication

Measles virus V protein represses genome replication through a poorly understood mechanism, which led us to investigate whether V protein might be an RNA-binding modulatory factor. Recombinant V protein, expressed from transfected HEp-2 cells or E. coli, formed protein-RNA complexes with poly-guanosine (poly-G) or poly-U linked to agarose beads. RNA binding was not exclusive to ribonucleotide homopolymers as complex formation between V protein and an RNA molecule equivalent to the 3' terminal 107 bases of the measles virus genome was observed with an electrophoretic mobility shift assay (EMSA). The interaction with poly-G was used to further examine the RNA binding properties of V demonstrating that protein-RNA complex formation was dependent upon the unique Cys-rich carboxy terminus, a region also required to induce maximal repression of minireplicon-encoded reporter gene expression in transient assays. Surprisingly, two mutant proteins that contained Cys-to-Ala substitutions in the C-terminus were found to retain their ability to bind poly-G binding and repress minireplicon reporter gene expression indicating that neither activity was dependent on the integrity of all 7 C-terminal Cys residues. Additional genetic analysis revealed that amino acids 238-266 were necessary for efficient RNA binding and overlapped with residues (238-278) required for maximal repression induced by the C-terminal domain. In addition, a 10 amino acid deletion was identified (residues 238-247) that blocked RNA binding and repression indicating that these two activities were related.

Inhibition of measles virus minireplicon-encoded reporter gene expression by V protein

Measles virus V protein is a Cys-rich polypeptide that is dispensable for virus propagation in continuous cell lines, but necessary for efficient viral replication in animals. Those functions modulating virus propagation in vivo are not understood completely, although V protein is known to interfere with the host interferon response and control of viral gene expression. The ability to modulate gene expression was investigated further with a minireplicon transient expression system in which V protein was found to repress reporter activity. Two regions of the polypeptide contributed to this repressive effect including the carboxy-terminus and a region conserved in morbillivirus V proteins located between amino acids 110-131, whereas domains known to mediate the interaction between V and the nucleocapsid (N) protein were not essential. Accumulation of encapsidated minigenome in transfected cells was inhibited by V protein suggesting that it acted as a repressor of genome replication thereby limiting availability of template for reporter gene mRNA transcription.

Hsp72 recognizes a P binding motif in the measles virus N protein C-terminus

The major inducible 70-kDa heat shock protein (hsp72) binds measles virus (MV) nucleocapsids and increases MV gene expression. The cytoplasmic tail of the MV N protein (N(TAIL)) contains three hydrophobic domains (Box-1-3) that are potential targets of hsp72 interaction. Low affinity binding to Box-3 is correlated to hsp72-dependent stimulation of MV minireplicon reporter gene expression whereas interactions between hsp72 and Box-1 and/or -2 have not been documented. The present work showed that virus deficient in Box-3/hsp72 interaction retains the ability to form nucleocapsid/hsp72 complexes, identifying Box-2 but not Box-1 as a mediator of high affinity hsp72 binding. Box-2 is the binding site for the viral P protein X domain (XD), where P tethers the viral polymerase to nucleocapsid in support of transcription and genome replication, and competitive inhibition of XD binding to N(TAIL) by hsp72 was shown. Recognition of a common binding site by P and hsp72 represents a potential mechanism for host cell modulation of viral gene expression.

Measles virus: evidence of an association with Hodgkin's disease

The quest for an infectious agent that may account for cases of Hodgkin's disease (HD) especially in young adults has proven vain until lately. We have recently reported findings that suggested the presence of measles virus (MV) antigens and MV RNA in the tissues of patients with HD. Support for an association between MV and HD has been provided by recent epidemiological findings relating the occurrence of HD to exposure to measles in pregnancy and the perinatal period. We now present further evidence of this putative association based on immunohistochemical, reverse transcriptase-polymerase chain reaction (RT-PCR) and in situ hybridisation studies (ISH) on HD tissues. Biopsies from 82 (54.3%) of our cohort of 154 patients showed a positive immunostain with at least two of the anti-measles antibodies used. Latent membrane protein-1 immunostaining for Epstein-Barr virus was positive in 46 (31.1%) of the patients examined. Reverse transcriptase-PCR and ISH for measles RNA were positive in seven and 10 of 28 patients, respectively. Preliminary clinicopathological associations between MV and HD are noted in this study, but no causal relationship can be claimed at this stage.

New candidate virus in association with Hodgkin's disease

Epidemiologic and molecular investigations of Hodgkin's disease (HD) suggest a strong infectious association. The Epstein-Barr virus (EBV), together with its viral proteins, is expressed in Hodgkin-Reed-Sternberg (HRS) cells in the lymph nodes involved by HD. EBV is more likely to be related to childhood and older adult cases of HD and is much less frequently expressed in young adult HD patients, the group most expected to be associated with an infectious agent. In addition, the "hit and run" theory of EBV infection remains speculative and no other lymphotropic viruses studied to date seem to satisfy the quest for a new candidate virus in young adults with HD. We have recently found preliminary evidence suggesting a possible association between the measles virus (MV) and HD. This evidence is the subject of the present review.

Identification and characterization of a regulatory domain on the carboxyl terminus of the measles virus nucleocapsid protein

The paramyxovirus template for transcription and genome replication consists of the RNA genome encapsidated by the nucleocapsid protein (N protein). The activity of the complex, consisting of viral polymerase plus template, can be measured with minireplicons in which the genomic coding sequence is replaced by chloramphenical acetyltransferase (CAT) antisense RNA. Using this approach, we showed that the C-terminal 24 amino acids of the measles virus N protein are dispensable for transcription and replication, based upon the truncation of N proteins used to support minireplicon reporter gene expression. Truncation at the C-terminal or penultimate amino acid 524 resulted in no change in CAT expression, whereas larger truncations spanning residues 523 to 502 were accompanied by an approximately twofold increase in basal activity. Reporter gene expression was enhanced by supplementation with the major inducible 70-kDa heat shock protein (Hsp72) for minireplicons with the N protein or the N protein truncated at position 525 or 524 but not in systems with a truncation at position 523 or 522. Naturally occurring sequence variants of the N protein with variations at positions 522 and 523 were also shown to lack Hsp72 responsiveness independent of changes in basal activity. Since these residues lie within a linear sequence predicting a direct Hsp72 interaction, N protein-Hsp72 binding reactions were analyzed by using surface plasmon resonance technology. Truncation of the C-terminal portion of the N protein by protease digestion resulted in a reduced binding affinity between Hsp72 and the N protein. Furthermore, with synthetic peptides, we established a correlation between the functional responsiveness and the binding affinity for Hsp72 of C-terminal N protein sequences. Collectively, these results show that the C-terminal 24 amino acids of the N protein represent a regulatory domain containing a functional motif that mediates a direct interaction with Hsp72.

Mucosal DNA Vaccine Immunization Against Measles with a Highly Attenuated Shigella flexneri Vector

An intranasal vaccine vector would elicit protective immunity at the respiratory mucosa, the portal of entry and the primary site for replication for measles virus (MV) and other respiratory viruses. In a murine model of pulmonary Shigella, we demonstrate here that a candidate-attenuated Shigella vaccine vector is safely tolerated in IFN-γ deficient mice at an inoculum that is 1 million-fold higher than the inoculum of the wild-type parent strain that would be lethal for greater than 90% of these mice. Also, following intranasal inoculation, the Δasd Shigella harboring a DNA MV vaccine plasmid induces a vigorous MV-specific Th1-type (both CD8+ CTL and IFN-γ) and, to a lesser degree, Th2-type responses among splenocytes in addition to low levels of IgG and IgA in the serum. Priming for MV-specific CTL responses was possible in mice that had prior infection with a wild-type Shigella of the same serotype. Remarkably, mice immunized by the intranasal route with attenuated Shigella harboring the DNA MV vaccine plasmid had a level of MV-specific CTL activity among splenocytes that was comparable with levels observed in mice immunized by the i.p. route with attenuated Salmonella typhi harboring the same DNA vaccine plasmid, despite the fact that Shigella remained localized to the lungs, yet Salmonella disseminated to the spleen following inoculation. Thus, Δasd Shigella represents a very useful vector for delivery of DNA vaccines to mucosal lymphoid tissues.

Persistent measles virus infection of murine neuroblastoma cells differentially affects the expression of PKC individual isoenzymes

Measles virus (MV) is among the infectious agents displaying a propensity for establishing persistent infections of the CNS. It is assumed that continuous presence of MV defective particles or viral genome in persistently infected cells may influence host cellular processes and perturb biochemical signal transduction pathways operating in linkage to various cell surface receptors. PKC expression in a MV persistently infected neuroblastoma cell line (NS20Y/MS) was investigated. The relative levels of PKC isoenzymes were determined by Western blot analysis. We found that protein levels of PKCalpha, epsilon and zeta, but not PKCdelta, were increased in NS20Y/MS cells. PKCbeta, gamma and eta were undetectable. Treatment of NS20Y/MS cells with anti-MV Abs, which downregulated MV protein synthesis, also reduced PKCalpha expression to the basal level observed in the uninfected NS20Y cells. Our results suggest that a persistent MV infection has specific effects on the expression of certain PKC isoenzymes. We postulate that the MV-associated neurologic changes may reflect virus induced changes in biochemical signaling pathways and that these effects are likely to be regulated by the host's anti-viral humoral immune response.

Measles virus nucleocapsid protein binds to FcgammaRII and inhibits human B cell antibody production

Despite the development of an efficient specific immune response during measles virus (MV) infection, an immunosuppression occurs contributing to secondary infections. To study the role of nucleocapsid protein (NP) in MV-induced immunosuppression, we produced recombinant MV NP. Purified recombinant NP exhibited biochemical, antigenic, and tridimensional structure similar to viral NP. By flow cytometry, we showed that viral or recombinant NP bound to human and murine B lymphocytes, but not to T lymphocytes. This binding was specific, independent of MHC class II expression, and dependent of the B lymphocyte activation state. The murine IIA1. 6 B cell line, deficient in the Fc receptor for IgG (FcgammaRII) expression, did not bind NP efficiently. Transfected IIA1.6 cells expressing either murine FcgammaRIIb1 or b2, or human FcgammaRIIa, b1*, or b2 isoforms efficiently bound NP. Furthermore, this binding was inhibited up to 90% by monoclonal antibodies 2.4G2 or KB61 specific for murine and human FcgammaRII, respectively. Finally, the in vitro Ig synthesis of CD40- or Ig-activated human B lymphocytes in the presence of interleukin (IL)-2 and IL-10 was reduced by 50% in the presence of recombinant NP. These data demonstrate that MV NP binds to human and murine FcgammaRII and inhibits in vitro antibody production, and therefore suggests a role for NP in MV-induced immunosuppression.

The effects of measles virus persistent infection on AP-1 transcription factor binding in neuroblastoma cells

Measles virus (MV) persistence in brain cells has broad effects on different cellular functions. We have previously shown that NS20Y clone, originally derived from C1300 neuroblastoma cells, persistently infected with MV (NS20Y/MS), displays constitutively elevated levels of c-fos and PKC mRNAs, implying MV-mediated effects on transcriptional regulation. Nonetheless, the mode by which virus affects the transcriptional machinery still remains obscure. In order to define this phenomenon, we studied the binding properties of major transcription factors (AP-1 and NFkappaB) in NS20Y/MS cells. Using electrophoretic mobility shift approach (EMSA) with the appropriate oligonucleotide probes, we have found that the persistent MV infection does not affect NFkappaB binding, while the AP-1 binding was significantly decreased. Similar inhibition was not observed in NS20Y cells acutely infected with MV. Anti-measles antibody-mediated restriction of viral gene expression restored AP-1 binding, thus suggesting that measles virus proteins may affect the components of the host transcriptional machinery.

Tyrosine phosphorylation of measles virus nucleocapsid protein in persistently infected neuroblastoma cells

Subacute sclerosing panencephalitis is a slowly progressing fatal human disease of the central nervous system which is a delayed sequel of measles virus (MV) infection. A typical pathological feature of this disease is the presence of viral ribonucleocapsid structures in the form of inclusion bodies and the absence of infectious virus or budding viral particles. The mechanisms governing the establishment and maintenance of a persistent MV infection in brain cells are still largely unknown. To understand the mechanisms underlying MV persistence in neuronal cells, a tissue culture model was studied. Clone NS20Y/MS of the murine neuroblastoma C1300 persistently infected with the wild-type Edmonston strain of MV secretes relatively high levels of alpha/beta interferon (IFN). As shown previously, treatment of the persistently infected cultures with anti-IFN serum converted the persistent state into a productive infection indicated by the appearance of multinucleated giant cells. In this study, we have investigated whether alpha/beta IFN produced by NS20Y/MS cells activates cellular protein tyrosine kinases which will induce tyrosine phosphorylating activity specific to virus-infected cells. We present data to show augmented protein tyrosine kinase activity in the persistently infected cells. We demonstrate that the MV N protein is phosphorylated on tyrosine in addition to serine and threonine in the persistent state but not in NS20Y cells acutely infected with MV.

Detection of immunoreactive antigen, with a monoclonal antibody to measles virus, in tissue from a patient with Crohn's disease

Using immunofluorescence (IF), we investigated reactive antigens present in Crohn's disease patients with monoclonal antibodies derived from cells infected with measles virus, but not with the subacute sclerosing panencephalitis virus. During immunoblotting, one monoclonal antibody (mAb 86) reacted with a polypeptide with a molecular weight of 36,000 dalton (M; matrix protein) in measles virus-infected cells. This monoclonal antibody displayed a positive reaction only with tissues from patients with Crohn's disease by the IF test. It did not react with samples from patients with other chronic inflammatory bowel diseases, such as ulcerative colitis. Other monoclonal antibodies to the measles virus protein, and monoclonal antibodies to Herpes simplex virus type 1 did not react with the same tissue samples. The role of measles virus infection and/or a viral antigen (possibly the M protein) as a causative agent in Crohn's disease poses a challenging avenue for further research.

Analysis of the antigenic profile of measles virus haemagglutinin in mice and humans using overlapping synthetic peptides

In this study, a panel of 55 synthetic peptides representing 92.2% of the haemagglutinin (H) glycoprotein of measles virus (MV) were used to study the antigenic profile of the H molecule of anti-MV antibodies raised in mice and late convalescent human sera. In addition the immunogenicity of these peptides was tested in two mouse strains. Mouse anti-MV antibodies had different fine specificity of binding to the peptides depending on the mouse strain. Thus in BALB/c (H-2d) mice, anti-MV antibodies recognised six peptides representing residues 103-117; 123-137; 242-255; 293-307 and 463-477. In TO (H-2s) mice, anti-MV antibodies recognised peptides representing residues 49-72 and 463-477. When the immunogenicity of the peptides was tested, 29 were immunogenic in BALB/c mice and 34 were immunogenic in TO mice. Several of the anti-peptide antisera were found to cross-react with MV, depending on the solid phase assay system used but none were able to inhibit virus infectivity in vitro. The reactivity of a panel of late convalescent human sera with the peptides was heterogeneous and the extent of the binding to the peptides was related to the titre of anti-MV. However, human sera recognized certain peptides more frequently than others, in particular peptides at the carboxyl-terminus.

Antibody-dependent transcriptional regulation of measles virus in persistently infected neural cells

Application of neutralizing anti-hemagglutinin antibodies to mouse neuroblastoma cells (NS20Y/MS) persistently infected with measles virus (MV) leads to a significant reduction of viral structural proteins within 6 days. While the transcriptional gradient for MV-specific mRNAs remained unaffected upon antibody treatment, the total amount of MV-specific transcripts dropped by 80% after 24 h. The expression of genomic RNA was affected similarly, with slightly slower time kinetics. Both transcription and expression of the viral structural proteins could be completely reactivated when viral antibodies were removed from the tissue culture. The same findings could be obtained in rat glioma cells persistently infected with subacute sclerosing panencephalitis virus (C6/SSPE) but not in cells of nonneural origin. The data indicate that antibody-induced antigenic modulation affects the early stages of viral transcription within a few hours after the addition of antibodies and leads to an almost complete repression of viral gene expression in cells of neural origin.

Differences in susceptibility to NK cell killing of two cloned sublines derived from a single clone

The ability of natural killer (NK) cells to discriminate between virus infected or tumor cells and their normal counterparts indicates a highly selective recognition, but the exact target structure remains unknown. We have examined two clones of measles virus persistently infected HeLa cells derived from the same parental clone, one of which, HeLa-mss, is highly susceptible to NK killing, (35% specific lysis at 80:1 lymphocyte to target ratio), whilst the other, HeLa-msr, is totally resistant (0.4-2.4% specific lysis). The HeLa-msr cells also failed to inhibit lysis of the HeLa-mss target cells, indicating that HeLa-msr cells did not share the receptor of HeLa-mss for NK cells. The expression of the two measles virus-encoded surface antigens, the hemagglutinin (HA) and fusion (F) proteins on the plasma membrane was examined by immunofluorescent staining and FACS analysis using monoclonal antibodies to the respective proteins. Approximately equivalent amounts of HA and F antigens were found on the cells of the HeLa-msr and HeLa-mss clones. Immunoprecipitation and PAGE analysis also failed to reveal any qualitative differences in the migration patterns or relative proportion of the measles virus proteins between these cell lines. Nevertheless, the in vitro differences in susceptibility of the two cell lines to NK lysis were found to be important in vivo, since HeLa-mss cells failed to grow as tumors in nude mice while HeLa-msr were highly tumorigenic. Thus, NK cells may either recognize very subtle differences in viral encoded polypeptides, possibly point mutations, or alternatively, they may recognize changes in the host cell membrane induced by insertion of certain viral encoded polypeptides.

Rapid degradation restricts measles virus matrix protein expression in a subacute sclerosing panencephalitis cell line

Measles virus matrix protein expression is restricted in the persistently infected brain cells of patients with the chronic neurological disease subacute sclerosing panencephalitis (SSPE). Prior studies of the nature of this restriction have identified polyadenylylated matrix gene-encoded RNA transcripts unable to direct effective translation. The defective nature of these mRNAs readily accounted for the inability to detect matrix protein in these persistently infected cells and suggested that in SSPE the restriction of matrix protein expression is achieved by preventing its synthesis. Recently, however, we reported evidence that matrix protein is synthesized in at least one example of this persistent infection, the SSPE cell line IP-3-Ca. In this case, failure of matrix protein to accumulate normally accounted for its restricted expression [Sheppard, R. D., Raine, C. S., Bornstein, M. B. & Udem, S. A. (1985) Science 228, 1219-1221]. To clarify the nature of the restriction displayed by IP-3-Ca cells, the synthesis and fate of the matrix protein of this SSPE cell line were examined in detail. No evidence of constraints on the efficiency of matrix protein mRNA transcription or translation was found. Instead, the restricted expression proved to be the result of rapid posttranslational degradation of matrix protein. We suggest that matrix protein gene mutations incurred in the course of genome replication are likely to be responsible for the diversity of observed mechanisms restricting matrix protein expression. In that event, the nature and position of the nucleotide substitution(s) would be the determinants of the level at which restricted expression is achieved.

Cloning and gene assignment of mRNAs of human parainfluenza virus 3

Cytoplasmic poly(A)-containing RNA from parainfluenza virus 3-infected cells was used as template to construct a cDNA library that was cloned into the EcoRV site of the plasmid pMG5. The resulting clones were screened with [32P]-labeled cDNA probes made from infected and mock-infected cell mRNAs. The virus specificity of the clones was confirmed by Northern blot hybridization. The viral clones were grouped into five different families by hybridization with individual size-selected reverse transcripts representing the major classes of poly(A)+-RNA from virus-infected cells. The five groups were shown to be unrelated on the basis of cross-colony hybridization and corresponded to five unique classes of intracellular viral poly(A)+-RNAs. Clones representing the NP and P genes of PIV-3 were identified by both hybrid-selected and hybrid-arrested translation. Clones specific for the P gene selected mRNA that directed the synthesis of P protein and another polypeptide of 21 kDa. This additional polypeptide comigrated with protein VP8 previously identified in virions and in infected cell lysates.

Proteins associated with human parainfluenza virus type 3

The polypeptides associated with human parainfluenza virus type 3 were identified. Five proteins were present in detergent- and salt-resistant viral cores. Of these, three proteins designated NP0, NP1, and NP2 of 68,000, 58,000, and 52,000 daltons, respectively, were stably associated with 50S RNA in CsCl gradient-purified nucleocapsids. The amounts of NP1 and NP2 were variable, and these proteins were shown to be structurally related to the major nucleocapsid protein (NP0) by partial Staphylococcus aureus V8 protease mapping. The other core proteins included a 240K protein designated L (candidate for the viral polymerase) and an 84K protein designated as the phosphoprotein (P) on the basis of a predominant incorporation of Pi. The viral envelope had four prominent proteins (72, 53, 40, and 12K) under reducing conditions of electrophoresis. The 72 and 53K proteins were specifically labeled with [3H]glucosamine and [3H]mannose. When sulfhydryl reagents were removed, a new 62K protein was visualized in place of the 72, 53, and 12K proteins. The 53 and 12K proteins were interpreted to be the two subunits (F1 and F2) of the fusion protein, and the 72K protein was designated as the HN (hemagglutinin-neuraminidase) glycoprotein. The unglycosylated 40K protein represented the viral matrix protein (M). Immunoprecipitation of infected cell lysates with rabbit hyperimmune antiserum against purified virus confirmed the viral origin of these polypeptides.

Regulation of the growth and functions of cloned murine large granular lymphocyte lines by resident macrophages

Using cloned lines with the morphology of large granular lymphocytes (LGL) from BALB/c mice, we studied the exact requirements for proliferation and their functional characteristics, as well as their regulation. Although these cloned LGL lines were interleukin 2 (IL-2) dependent for growth, experiments using human recombinant IL-2 (rIL-2), known to be active on murine cells, indicated that IL-2 was a necessary but not sufficient factor. Coexistance of normal macrophages in addition to rIL-2 was found to support continuous proliferation of cloned LGL in vitro. This role of macrophages could be replaced by partially purified IL-1 derived from macrophage-conditioned medium. An IL-2 binding assay using 125I-rIL-2 suggested that the role of normal macrophages was to selectively induce and/or maintain high affinity IL-2 receptors (IL-2R) (Kd, 0.2-0.5 nM) without affecting low affinity ones (Kd, 10-30 nM). Functional studies indicated that most of the LGL clones killed various combinations of representative groups of natural killer (NK)-susceptible target cells, including leukemic cells (YAC-1, RL male 1), virus-infected cells (HeLa-measles, HeLa-herpes simplex virus), and normal bone marrow cells (BMC), whereas none of them affected any of NK-resistant target cells, including uninfected HeLa cells. Some of these clones also suppressed in vitro hematopoiesis. Such characteristic cytotoxic spectra, as well as serological phenotypes (Thy-1+, Lyt-1-2-, asialo GM1-positive, T200+, TdT-, Fc receptor-positive) indicated that these LGL clones exactly represent endogenous NK cells, rather than a variety of anomalous killer cells generated in various culture conditions. Although there was significant heterogeneity of cytotoxic spectrum among LGL clones, no clonotypic distribution of specificities was observed. Normal macrophages were found to modulate the functional expression of LGL clones. They augmented the cytotoxic potential of the clones against leukemic and virus-infected targets, but suppressed intrinsic reactivity against normal BMC. Similarly, LGL clones maintained with macrophages showed much less suppressive effect on in vitro hematopoiesis. The present observations on the interaction of cloned LGL and normal macrophages provide a basic explanation for the mechanisms by which the immediate responsiveness to IL-2 of the NK effector system, without exogenous stimulation, and the functional selectivity toward abnormal rather than normal cells, are actively maintained in vivo.

Correlation between epitopes on hemagglutinin of measles virus and biological activities: passive protection by monoclonal antibodies is related to their hemagglutination inhibiting activity

Measles virus monoclonal antibodies (MoAbs) were used to investigate the structure of the hemagglutinin (H) antigen, in order to study the regions of the molecule implicated in protection. Using a competition binding assay, three overlapping domains were defined, and these have been correlated with the biological activities of their corresponding MoAb. All of the anti-H MoAbs, with a single exception, neutralized virus infectivity in vitro. We investigated their capacity in passive protection using a measles virus-mouse model, in which inoculated newborn mice died of an acute encephalitis. The course of the disease was monitored after passive administration of the MoAbs, and from their activity, these MoAbs could be divided in three groups: I--protective, II--inducer of a retarded disease, III--nonprotective. The isotype of the antibody did not play a direct role in determining the course of the disease. Moreover, we were able to correlate protection with biological activity of the MoAbs. Only the MoAbs which inhibit hemagglutination activity (HI) protected against the acute disease. Measles MoAbs which neutralize canine distemper virus (CDV) in vitro failed to passively protect CDV-infected mice against disease. These results suggest an immune mechanism for in vivo protection different from that implicated in in vitro neutralization. Administration of one MoAb (55) led to a retarded neurological disease. Mice receiving lower quantities of other protective MoAbs did not display such disease. These results are discussed in relationship to immunization and protection.

Measles virus matrix protein synthesized in a subacute sclerosing panencephalitis cell line

Measles virus generally produces acute illness. Rarely, however, persistent infection of brain cells occurs, resulting in a chronic and fatal neurological disease, subacute sclerosing panencephalitis (SSPE). Evidence indicates that expression of the measles virus matrix protein is selectively restricted in this persistent infection, but the mechanism underlying this restriction has not been identified. Defective translation of matrix messenger RNA has been described in one SSPE cell line. This report presents evidence that in a different SSPE tissue culture cell line IP-3-Ca, the matrix protein is synthesized but fails to accumulate. A general scheme is proposed to reconcile the different levels at which restriction of matrix protein has been observed.

Monoclonal antibodies against microorganisms

The recent spread of hybridoma technology among laboratories has promoted the development of monoclonal antibodies against a wide variety of infectious disease agents. While monoclonal antibodies theoretically represent an excellent (perhaps superior) alternative to conventional antisera as diagnostic, therapeutic or laboratory reagents, traditional antisera may be preferable to monoclonal antibody in some circumstances because of the fixed affinity and specificity as well as the limited functional capacities of some antibodies. The acceptance of monoclonal antibodies by the clinical microbiologist and physician must await proof of their reliability, safety and efficacy.

Isolation of cold-sensitive mutants of measles virus from persistently infected murine neuroblastoma cells

Clone NS20Y of the mouse neuroblastoma C1300 was infected with wild-type Edmonston measles virus, and, after a transition to a carrier culture, became persistently infected. Persistently infected clones were derived and characterized morphologically by the appearance of multinucleate giant cells and nucleocapsid matrices in cytoplasm and nucleus, but very few budding virus particles. Antimeasles antibodies markedly suppressed the expression of viral antigens and giant cells, and the effect was totally reversible. When the cells were cultured at 33 degrees C, the number of giant cells began to diminish and ultimately disappeared; in contrast, when cultured at 39 degrees C, the cultures invariably lysed. Yields at 33 degrees C were ca. 2 logs lower than those at 39 degrees C. Cells cultured at 33 degrees C produced relatively high levels of interferon, whereas those at 39 degrees C produced little or no interferon. When the persistently infected cultures were exposed to anti-interferon alpha/beta serum at a nonpermissive temperature, there was a marked increase in multinucleate cells, suggesting that maintenance of the persistence state and its regulation by temperature may be related to the production of interferon. Viral isolates from cells cultured at 39 degrees C were obtained, and 90% of viral clones were found to be cold sensitive. Complementation studies with different viral clones indicated that the cold-sensitive defect was probably associated with the same genetic function. Western blot analysis of the persistently infected cells indicated a significant diminution and expression of all measles-specific proteins at a nonpermissive temperature. Infection of NS20Y neuroblastoma cells with the cold-sensitive virus isolates resulted in the development of an immediate persistent infection, whereas infection of Vero or HeLa cells resulted in a characteristic lytic infection, suggesting that the cold-sensitive mutants may be selected or adapted for persistent infection in cells of neural origin.

Measles virus: conditions for the propagation and purification of infectious virus in high yield

Tissue culture conditions for the efficient propagation of cell-free measles virus, and a novel method for the purification of infectious virus in milligram quantities are described in this report. Infected suspension cultures of HeLa cells incubated at 32.5 degrees C yielded virus titers approaching 10(8) PFU/ml, 30-50% of which was cell-free. After concentration by ultrafiltration and sedimentation, infectious virus was separated from host cell membranes and proteins by density equilibrium centrifugation in gradients of colloidal silica. Residual contaminants and silica particles were removed by chromatographic elution through agarose gel. This protocol achieved a approximately equal to 1400 fold purification of virus which retained approximately equal to 75% infectivity while yielding approximately equal to 1.5 mg of viral protein from each liter of infected cell culture medium. Electron microscopy of the purified virus revealed only intact particles having the morphological characteristics of the paramyxoviruses. Serological studies confirmed the purified material to be antigenically reactive measles virus. SDS-PAGE analysis of the virus preparation identified eight polypeptide species as described by others. Seven of these are virus-specified structural proteins corresponding to the L, H, P, NP, F1, M, and F2 polypeptides. The eighth major structural protein was defined as host cell derived actin.

Isolation and characterization of measles virus intracellular nucleocapsid RNA

Protocols have been established for the preparation of large amounts of pure measles virus intracellular nucleocapsids. As a result, it has been possible to routinely achieve nucleocapsid RNA yields of approximately 200 micrograms (from approximately 5 X 10(8) infected cells). Electrophoretic analysis of this RNA under denaturing conditions revealed a single species whose mass was estimated at approximately 4.8 X 10(6) daltons. Electron microscopic assessment of nucleocapsid RNA contour lengths corroborated the electrophoretic size determination. Total nucleocapsid RNA was shown to contain both negative- and positive-stranded species distributed in a ratio of 2 to 3 genome polarity molecules for each antigenome RNA. Hybridization studies established that all of the virus-specified polyadenylated RNAs were encoded by the negative-stranded nucleocapsid RNA and, therefore, that this nucleocapsid RNA was the measles genome. Examination of the measles virus-specified, polyadenylated transcription products by HCHO-agarose gel electrophoresis revealed at least nine distinct RNA species (rather than the six predicted measles mRNAs). The significance of these observations is discussed.

Synthesis and processing of glycoproteins of Varicella-Zoster virus (VZV) as studied with monoclonal antibodies to VZV antigens

Varicella-Zoster virus (VZV) contains four major glycoproteins designated as gp 1(115K), gp 2(100-80K), gp 3(64K), and gp 5(55K) (K. Shiraki, T. Okuno, K. Yamanishi, and M. Takahashi, J. Gen. Virol. 61, 255-269, 1982). The present studies focused on the synthesis and processing of these glycoproteins using monoclonal antibodies. Twenty-seven hybridomas secreting monoclonal antibodies against VZV proteins have been established. The antibodies were characterized further by radioimmunoprecipitation with [35S]-methionine, [3H]glucosamine, [125I]labeled viral antigens followed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Twelve clones of these hybridomas produced antibodies to glycosylated polypeptides of VZV, which could be classified into three groups on the basis of the electrophoretic patterns. The first group reacted specifically with polypeptides with apparent molecular weights of 94K and 83K (both presumed to correspond to gp 2) in infected cells, on the surface membrane of infected cells, and on the virions. The second group precipiated polypeptides with molecular weights of 94K, 83K, 55K (corresponding to gp 5) in infected cells, and 94K, 83K, 55K, 45K on the surface membrane of infected cells, and 94K, 83K, and 55K on the virions. Finally, the third group reacted with polypeptides with molecular weights of 116K, 106K, and 64K corresponding to gp 3) in infected cells, 64K on the surface membrane of infected cells, and on the virions. By pulse-chase experiments, antibodies from the former two groups precipitated new polypeptides with molecular weights of 75K and 49K, respectively, which were presumed to be precursor proteins. These data suggest that the precursor proteins of gp 2, gp 3, and gp 5 are synthesized in infected cells, glycosylated, and the product proteins are expressed on the surface membrane of infected cells as well as on the virions. It was also found that a glycoprotein of 45K detected in culture fluid of infected cells (K. Shiraki and M. Takahashi, J. Gen. Virol. 61, 271-275, 1982) was derived from the polypeptide with molecular weight of 55K (gp 5).

Monoclonal antibodies against five structural components of measles virus. I. Characterization of antigenic determinants on nine strains of measles virus

Monoclonal antibodies against five structural proteins of measles virus were used to determine the degree of antigenic variation within these proteins amongst nine strains of measles virus (four fresh wild-type isolates, two vaccine and two laboratory strains, and a strain derived from a case of subacute sclerosing panencephalitis) giving lytic infections in cell culture. The major surface proteins showed limited variations in their epitopes between the nine strains. No variations in the fusion (F) protein and only three variations in the hemagglutinin (H) protein epitopes were detected by radioimmune precipitation assay and other serological tests using a panel of 11 monoclonal antibodies against each protein. These antibody panels consisted of at least nine and six different binding groups for the H and F proteins, respectively. The two innermost proteins, the nucleocapsid and polymerase proteins, also appeared to be antigenically stable as no variation was detected between strains using in each case a panel of six hybridomas. In sharp contrast, the epitopes on the matrix (M) protein of different strains showed extensive variation in their reactivity with the nine anti-M monoclonal antibodies. The possible use of M protein epitopic markers in classification of measles virus strains is discussed.

Monoclonal antibodies to baculovirus structural proteins: determination of specificities by Western blot analysis

Conventional mouse hybridoma technology was utilized to produce a panel of monoclonal antibodies which reacted with baculovirus proteins. Using an enzyme-linked immunosorbent assay (ELISA), the hybridomas which were raised against polyhedrin from Autographa californica nuclear polyhedrosis virus (AcNPV) and Choristoeura fumiferana nuclear polyhedrosis virus (CfNPV) were found to cross-react differentially with polyhedrins and granulins from several species of baculoviruses. Hybridoma antibodies which reacted against the nonoccluded form (NOV) of AcNPV in an ELISA test expressed different specificities for the occluded form of the virus (OV), a mutant strain of AcNPV, and CfNPV. Four hybridoma clones produced antibody which neutralized the infectivity of AcNPV NOV. One hybridoma antibody reacted strongly with the uninfected Spodoptera frugiperda host cell line. Using Western blot analysis, it was shown that hybridoma antibodies against polyhedrin reacted differentially with the complete polypeptide and protease-generated fragments of polyhedrin. The polypeptide specificity of 19 of 28 hybridoma antibodies which reacted with OV and NOV of AcNPV was assigned using Western blot analysis.

Five measles virus antigens demonstrated by use of mouse hybridoma antibodies in productively infected tissue culture cells

Mouse hybridoma antibodies against 5 different structural components of measles virus were used in immune fluorescence tests to characterize the appearance of viral antigens in productively infected cell cultures. The antibodies employed in the tests reacted specifically with the hemagglutinin (H, 79K), polymerase (P, 72K), nucleocapsid (NP, 60K) hemolysin-fusion factor (F, 41+20K) and matrix (M, 36K) proteins. Syncytia formed in lytically infected cultures and single isolated cells in persistenly infected cell cultures were both examined. Antibodies against NP and P proteins stained cytoplasmic inclusions varying in size from small dots to more confluent masses, frequently in a perinuclear position. Nuclei of infected cells contained exclusively NP antigen. Antibodies to envelope components--H, F and M--stained cytoplasmic membrane structures and also gave a granular cytoplasmic staining, especially in syncytia. Although all persistently infected cells produced NP antigen and the associated P component, they had a restricted capacity to produce demonstrable amount of envelope antigens. The occurrence of cells containing envelope antigens varied between about 50 and 5 per cent with H and F antigens giving the highest and lowest frequence values, respectively. It is proposed that a restricted capacity of cells to produce biologically active fusion protein is a prerequisite for maintaining a persistent infection in actively dividing cells in vitro.

Present status and future prospects for the hybridoma technology

A somatic cell genetic technique has recently been developed that makes it possible to obtain very large amounts of homogeneous antibodies and to replenish the supply of the exact same antibodies whenever they are needed. This hybridoma technology has already contributed to major scientific advances and will surely improve the diagnosis and treatment of many diseases. Because the technology itself is relatively simple and inexpensive, it has captured the attention of basic scientists, clinicians, and industrial managers and investors.