Persistent antigenic variation of influenza A viruses after incomplete neutralization in ovo with heterologous immune serum

Nephropathogenic infectious bronchitis in Pennsylvania chickens 1997-2000

Nephropathogenic infectious bronchitis (NIB) was diagnosed in 28 infectious bronchitis virus (IBV)-vaccinated commercial chicken flocks in Pennsylvania from December 1997 to July 2000. Early dinical signs were increased flock mortality and urinary water loss (polyuria and pollakiuria) leading to wet litter. Daily mortality ranged from 0.01% in layers to 2.45% in broilers, with total broiler mortality as high as 23%. Severe renal swelling and accumulation of urates in the tubules were commonly seen. Visceral gout and urolithiasis were less frequently observed. Histopathologic changes included characteristic tubular epithelial degeneration and sloughing with lymphoplasmacytic interstitial nephritis. Minimal respiratory disease signs were noted in broilers. Egg production and shell quality declined in layers. Confirmatory diagnosis of NIB was made by IBV antigen-specific immunohistochemical staining of the renal tubular epithelium and virus isolation. Sequencing of the S1 subunit gene of 21 IBV isolates showed the NIB outbreak to be associated with two unique genotypes, PA/Wolgemuth/98 and PA/171/99. The cases from which the genotypes were isolated were clinically indistinguishable. The NIB viruses were unrelated to previously recognized endemic strains in Pennsylvania and were also dissimilar to each other. Genotype PA/Wolgemuth/98 was isolated almost exclusively during the first 14 mo of the outbreak, whereas PA/171/99 was recovered during the final 18 mo. The reason for the apparent replacement of PA/Wolgemuth/98 by PA/171/99 is not known.

The total influenza vaccine failure of 1947 revisited: major intrasubtypic antigenic change can explain failure of vaccine in a post-World War II epidemic

Although vaccine-induced immunity to influenza A virus is continually challenged by progressively selected mutations in the virus's major antigens (antigenic drift), virus strains within a subtype (e.g., H1N1) are antigenically cross-reactive. Although cross-immunity diminishes as further mutations accumulate, necessitating frequent changes in vaccine strains, older vaccines are usually partially protective. The post-World War II epidemic of 1947 is notable for the total failure of a vaccine previously effective in the 1943-44 and 1944-45 seasons. We have combined extensive antigenic characterization of the hemagglutinin and neuraminidase antigens of the 1943 and 1947 viruses with analysis of their nucleotide and amino acid sequences and have found marked antigenic and amino acid differences in viruses of the two years. Furthermore, in a mouse model, vaccination with the 1943 vaccine had no effect on infection with the 1947 strain. These findings are important, because complete lack of cross-immunogenicity has been found previously only with antigenic shift, in which antigenically novel antigens have been captured by reassortment of human and animal strains, sometimes leading to pandemics. Although the 1947 epidemic lacked the usual hallmarks of pandemic disease, including an extensive increase in mortality, it warns of the possibility that extreme intrasubtypic antigenic variation (if coupled with an increase in disease severity) could produce pandemic disease without the introduction of animal virus antigens.

Origin and evolution of Georgia 98 (GA98), a new serotype of avian infectious bronchitis virus

We previously identified GA98, a new serotype of infectious bronchitis virus (IBV), which is closely related to the DE072 serotype of IBV genetically, but not antigenically. Herein, we analyzed the 421bp sequence of a hypervariable region (HVR) (position 114-534, counting from the ATG start site) of the S1 subunit of GA98 IBVs to further examine the evolution of these viruses. These viruses were isolated between the years 1997 and 2000. Phylogenetic analysis of the deduced amino acid sequence on that region indicated that GA98 isolates from different regions of Georgia were the result of a single introduction of the S1 gene of the DE072 serotype progenitor. Most of the mutations were nonsynonymous and had become fixed in a progressive manner. The evolutionary and mutation rates in the HVR was calculated as 2.5 and 1.5% per year, respectively. This new serotype of IBV appears to be evolving very fast compared with other serotypes of IBV. We further determined the complete coding sequence of the S1 gene of seven isolates obtained from one selected region in North Georgia. Together with virus neutralization data, it appears that GA98 arose from immune selection caused by DE072 vaccine use. Reasons for this conclusion are discussed.

Antigenic properties and experimental transmission to several fish species of a marine birnavirus isolated from sole (Solea senegalensis)

A cross-neutralization test was used to study the antigenic relationship of an aquabirnavirus isolated from sole (Solea senegalensis), named solevirus, and several infectious pancreatic necrosis virus (IPNV) strains. Solevirus was antigenically similar to IPNV strain Sp. Transmission of the solevirus to other fish species has been determined by inoculation to freshwater and marine fish species (two salmonids and gilt-head seabream). A higher pathogenicity was obtained for the marine fish species, although solevirus caused an asymptomatic infection in all species tested, as demonstrated by the detection of viral RNA and of viral antigens in fish leucocytes, respectively, using polymerase chain reaction (PCR) and flow cytometry (FC).

Evidence for the presence of two novel pestivirus species

The genus Pestivirus of the family Flaviviridae comprises four species, namely Bovine viral diarrhea virus-1 (BVDV-1), BVDV-2, Border disease virus (BDV), and Classical swine fever virus (CSFV). Comparative analyses of partial sequences have suggested that pestivirus isolates from giraffe (Giraffe-1) and reindeer (Reindeer-1) are distinct from the established species (Becher et al., Virology 262, 64--71, 1999). In this study, we report the complete genomic sequences of pestivirus strains Giraffe-1 and Reindeer-1. Comparative sequence analyses revealed considerable differences among Giraffe-1, Reindeer-1, and the currently recognized pestivirus species. Phylogenetic analysis of the complete coding sequences of these two strains, along with 13 other sequences representing the four established species, indicated that CSFV, BDV, and Reindeer-1 have bifurcated from one common branch and BVDV-1 and BVDV-2 from another. In the former branch BDV and the pestivirus from reindeer are more similar to each other than to CSFV. The giraffe pestivirus is equally distinct from both major branches. In addition, the antigenic relatedness of pestivirus isolates covering the observed major genetic groups was studied by cross-neutralization assays. A clustering procedure on the basis of antigenic differences indicated the presence of six major groups corresponding to the genetically defined groups. Taken together, the results of our analyses addressing both nucleotide sequence relatedness and serological relatedness argue for the inclusion of Giraffe-1 and Reindeer-1 as the first members of two separate novel species within the genus Pestivirus.

Antigenic variants of influenza A virus (PR8 strain) III. Serological relationships of a line of variants derived in sequence in mice given homologous vaccine

Seven variant strains of influenza A PR8-S virus, each derived from the previous one by serial passage in the lungs of mice immunized with the homologous agent have been produced. With the H.I. and neutralization procedures these variants showed a progressive serological deviation from the parent PR8-S virus. The seven variants provoked antibodies in varying titers to the preceding variants and the parent virus but not in relation to their position in the series. Thus, the seventh variant provoked significantly more antibody to the PR8-S virus than did the fifth variant. A possible explanation for this is presented. The first four variant viruses showed progressively less ability to react with antisera of the preceding variants and the PR8-S virus, and the three most recently derived variants showed essentially no ability to react with PR8-S and first variant antisera. The variant viruses remained antigenically stable through numerous lung passages in normal mice. Cross absorption tests revealed common antigenic components among the variant viruses and also individual characteristics which classify them as being different from one another. The implications of these findings in relation to studies by others have been discussed.

Recovery and altered neutralization specificities of chimeric viruses containing capsid protein domain exchanges from antigenically distinct strains of feline calicivirus

Feline calicivirus (FCV) strains can show significant antigenic variation when tested for cross-reactivity with antisera produced against other FCV strains. Previous work has demonstrated the presence of hypervariable amino acid sequences in the capsid protein of FCV (designated regions C and E) that were postulated to constitute the major antigenic determinants of the virus. To examine the involvement of hypervariable sequences in determining the antigenic phenotype, the nucleotide sequences encoding the E regions from three antigenically distinct parental FCV strains (CFI, KCD, and NADC) were exchanged for the equivalent sequences in an FCV Urbana strain infectious cDNA clone. Two of the three constructs were recovered as viable, chimeric viruses. In six additional constructs, of which three were recovered as viable virus, the E region from the parental viruses was divided into left (N-terminal) and right (C-terminal) halves and engineered into the infectious clone. A final viable construct contained the C, D, and E regions of the NADC parental strain. Recovered chimeric viruses showed considerable antigenic variation from the parental viruses when tested against parental hyperimmune serum. No domain exchange was able to confer complete recognition by parental antiserum with the exception of the KCD E region exchange, which was neutralized at a near-homologous titer with KCD antiserum. These data demonstrate that it is possible to recover engineered chimeric FCV strains that possess altered antigenic characteristics. Furthermore, the E hypervariable region of the capsid protein appears to play a major role in the formation of the antigenic structure of the virion where conformational epitopes may be more important than linear in viral neutralization.

Characteristics of a new birnavirus associated with a warm-water fish cell line

A warm-water fish cell line developed from blotched snakehead caudal peduncle (BSN) was found to have persistent birnavirus infection. Purified virus particles were of icosahedral shape and had 57+/-1.6 nm diameter. The BSN virus was resistant to 5-iodo-2'-deoxyuridine and induced yellowish-green cytoplasmic inclusions when stained with acridine orange. The virus was resistant to chloroform, acid and alkaline pH and heat treatment at 56 degrees C for 2 h. Purified virions had a buoyant density of 1.33 g/ml in CsCl and contained two genomic segments with molecular masses of 2.56 x 10(6) and 2.00 x 10(6) Da and four structural polypeptides of 112 (polyprotein, PP), 91 (VP1), 44 (VP2) and 37 (VP3) kDa. Reciprocal beta cross-neutralization tests incorporating four classical strains of infectious pancreatic necrosis virus (IPNV) (WB, Sp, Ab and TV-1) and the BSN virus established the complete serological distinctness of the virus from IPNV. Considering the uniqueness of the virus, the name blotched snakehead virus is proposed for this agent.

Antigenic characterization of Brazilian bovine viral diarrhea virus isolates by monoclonal antibodies and cross-neutralization

Nineteen Brazilian isolates of bovine viral diarrhea virus (BVDV) were characterized antigenically with a panel of 19 monoclonal antibodies (mAbs) (Corapi WV, Donis RO and Dubovi EJ (1990) American Journal of Veterinary Research, 55: 1388-1394). Eight isolates were further characterized by cross-neutralization using sheep monospecific antisera. Analysis of mAb binding to viral antigens by indirect immunofluorescence revealed distinct patterns of reactivity among the native viruses. Local isolates differed from the prototype Singer strain in recognition by up to 14 mAbs. Only two mAbs--one to the non-structural protein NS23/p125 and another to the envelope glycoprotein E0/gp48--recognized 100% of the isolates. No isolate was recognized by more than 14 mAbs and twelve viruses reacted with 10 or less mAbs. mAbs to the major envelope glycoprotein E2/gp53 revealed a particularly high degree of antigenic variability in this glycoprotein. Nine isolates (47.3%) reacted with three or less of 10 E2/gp53 mAbs, and one isolate was not recognized by any of these mAbs. Virus-specific antisera to eight isolates plus three standard BVDV strains raised in lambs had virus-neutralizing titers ranging from 400 to 3200 against the homologous virus. Nonetheless, many antisera showed significantly reduced neutralizing activity when tested against heterologous viruses. Up to 128-fold differences in cross-neutralization titers were observed for some pairs of viruses. When the coefficient of antigenic similarity (R) was calculated, 49 of 66 comparisons (74.24%) between viruses resulted in R values that antigenically distinguish strains. Moreover, one isolate had R value suggesting that it belongs to a distinct serologic group. The marked antigenic diversity observed among Brazilian BVDV isolates should be considered when planning diagnostic and immunization strategies.

Antigenic relatedness of selected flaviviruses: study with homologous and heterologous immune mouse ascitic fluids

The antigenic relationship of 9 flaviviruses, Yellow fever (YF), Wesselsbron (WSL), Uganda S (UGS), Potiskum (POT), West Nile (WN), Banzi (BAN), Zika (ZK), Dengue type 1 (DEN-1) and Dengue type 2 (DEN-2), was assessed by cross-haemagglutination-inhibition (Cross-HI) and cross-complement fixation (Cross-CF) reactions between each of the viruses and their homologous immune mouse ascitic fluids. Titre ratios were calculated using the heterologous and homologous titres. Cross-CF reactions revealed wider antigenic variations among viruses than Cross-HI reactions. There was no significant antigenic variation between WSL, POT and YF viruses using either of those methods. However, definite differences in antigenicity were observed between them and UGS, BAN and ZK viruses. There were no significant differences between UGS, BAN and ZK or between DEN-1 and DEN-2. The serological relationship among flaviviruses is important in establishing diagnosis and epidemiology of these infections in Africa.

Serological relationship among porcine cytomegalovirus Japanese isolates and a UK isolate

We isolated porcine cytomegaloviruses (PCMVs) from lung samples of fattening pigs collected in the slaughter houses of 4 prefectures of Japan. Seven isolates were obtained and used for a comparison of serological characteristics by ELISA. J1, the first field isolate in Japan, and B6 which was isolated in the UK were also used in the study. The serological relationships between the isolates were analysed by the method of Archetti and Horsfall. OF1 showed serological differences with Chiba2 and Hiroshima. Differences were also observed between Chiba2 and ChibaC, ChibaC and Kagawa. B6 showed differences with OF2, Chiba3, ChibaC and Hiroshima.

Antigenic differentiation of turkey rhinotracheitis virus strains using monoclonal antibodies and polyclonal antisera

Monoclonal antibodies (mAbs) were prepared against the 8597/CV94 strain of turkey rhinotracheitis virus (TRTV). These mAbs were used to investigate antigenic relationships among three strains (8597/CV94, 1162/92 and CVL14/1 strain) of TRTV, together with polyclonal chicken and rabbit antisera to 8597/CV94 strain, and guinea pig antisera to each of the three strains. Thirty mAbs to the glycoprotein (G:3 clones), fusion (F1:6 clones), phosphorylated (P:6 clones), nucleocapsid (N:12 clones), and matrix (M:3 clones) proteins of viral antigen were obtained by cell fusion. Among these, two mAbs to F1 protein showed virus neutralizing activity. The results of ELISA test indicated that some mAbs only reacted to the 8597/CV94 strain, some reacted to 8597/CV94 and 1162/92 strains, and others reacted to all three viral strains. In neutralization tests with the three virus strains, polyclonal chicken and rabbit antisera against the 8597/ CV94 strain showed the same antibody titers. Results with four neutralizing mAbs including two previously reported mAbs [Ref. 21] indicated the titers of two mAbs (Pn2-2E and Pn3-2F) to 8597/CV94 were much higher than those to the other two viral strains. No differences were observed in the titers of the other two mAbs (Pn01-8E and Pn06-4D) against any viral strains. In cross-neutralization tests with polyclonal guinea pig antisera, there was some variations among viral strains. This work demonstrated that the Japanese isolate 8597/CV94 of TRTV is somewhat different in antigenicity from two British isolates from chickens and turkeys.

The characterization of infectious bursal disease virus strains/isolates from field outbreaks in India

Three infectious bursal disease virus (IBDV) isolates were adapted to culture in chick embryo fibroblast cells in which they produced a cytopathic effect. The isolates were identified as IBDV by virus neutralization tests using a standard hyperimmune serum against infectious bursal disease, physicochemical properties and their pathogenicity in chick embryos and chicks. The IBDV S394 strain was antigenically different from IBDV S194/IBDV S494 as well as from the IBDV Intermediate Georgia strain, one of the vaccine strains in use in India.

INTERFERON PRODUCTION AND SENSITIVITY OF SEMLIKI FOREST VIRUS VARIANTS

Semliki Forest virus was passaged 10 times in series in calf kindly cells, starting with virus passaged in the mouse brain (MB virus). A variant was obtained (termed CK virus). The two viruses were antigenically indistinguishable. When grown on L cells, CK virus formed smaller plaques than MB virus. In parallel growth curve studies in calf kidney cells, a small inoculum of CK virus grew more rapidly and to a higher final titre than a comparable inoculum of MB virus, and usually stimulated production of less interferon. Pre-treatment of cells with calf interferon reduced the growth of both viruses, but especially that of MB virus. The results are considered in relation to the phenomenon of virus adaptation. It is suggested that such differences between the two variants in their relative sensitivity to and production of interferon could have played a part in the emergence of CK virus as the predominant type during serial passages in calf cells.

I wish to thank Mr H. Moores and Mr R. Sims for skilful technical assistance.

Protectotypic differentiation of avian infectious bronchitis viruses using an in vitro challenge model

Two vaccine and three virulent strains of infectious bronchitis virus (IBV) were used to infect day-old specific-pathogen-free chickens. Precocious development of oviducts was induced in young female chicks by oestrogen injections. Tracheal and oviduct organ cultures prepared from immunised chickens were challenged in vitro with homologous and heterologous viruses to assess tracheal and oviduct cross-protection. Tracheal cross-protection was seen between serologically related and unrelated viruses. Protection at at the level of the oviducts was lower compared to that seen at the tracheal level. However, the yields of the homologous challenge viruses from immunised oviducts were significantly reduced as compared to yields from normal oviducts. After challenge, tracheal and oviduct ciliary scores were used to group the five strains of IBV into protectotypes. The five viruses could be grouped into three protectotypes and four serotypes. The virulent IBV strains were found to have caused complete stasis of oviduct cilia when examined at three weeks post-infection. Oestrogen treatment of chicks did not significantly alter the lymphocyte proliferation responses to concanavalin A or pokeweed mitogen. The applicability of this model for the study of protection afforded to the oviducts, in terms of protection against virus-induced damage, rather than drop in egg production, is discussed.

Antigenic and biological comparisons of bovine coronaviruses derived from neonatal calf diarrhea and winter dysentery of adult cattle

The antigenic and biological properties of 6 strains of bovine coronavirus (BCV) derived from neonatal calf diarrhea (CD) and 8 strains of BCV from winter dysentery (WD) of adult cattle, propagated in HRT-18 cells, were compared to determine if CD and WD strains belong to distinct serotypes or subtypes of BCV. All strains hemagglutinated both mouse and chicken erythrocytes at 4 degrees C, but the ratios of hemagglutination titers with mouse erythrocytes compared to chicken erythrocytes showed diversity for both CD and WD strains. Some CD and WD strains did not hemagglutinate chicken erythrocytes at 37 degrees C and showed receptor-destroying enzyme activity against chicken erythrocytes. Hyperimmune antisera were produced in guinea pigs against 3 and 7 strains of BCV from CD and WD, respectively. No significant differences in antibody titers against these strains were observed by indirect immunofluorescence tests. However, in virus neutralization tests, antisera to 1 CD and 2 WD strains had 16-fold or lower antibody titers against 3 WD and 1 CD strains than against the homologous strains, and this variation reflected low antigenic relatedness values (R = 13-25%), suggesting the presence of different subtypes among BCV. In hemagglutination inhibition tests, some one-way antigenic variations among strains were also observed. These results suggest that some antigenic and biological diversity exists among BCV strains, but these variations were unrelated to the clinical source of the strains; i.e. CD or WD.

Isolation of an influenza A virus of unusual subtype (H1N7) from pigs in England, and the subsequent experimental transmission from pig to pig

A novel H1N7 influenza virus (A/swine/Eng/191973/92) was isolated from nasal swabs collected from two pigs on a farm where there had been recent clinical disease due to infection with an H1N1 virus (A/swine/Eng/195852/92). Antigenically, the haemagglutinin (HA) of the H1N7 virus was related most closely to the HA of A/USSR/90/77, whilst the neuraminidase (NA) appeared to be related most closely to the NA of A/equine/Prague/1/56 (H7N7). Pigs infected experimentally with A/swine/Eng/191973/92 developed mild clinical signs, excreted virus into the nasal passages for up to nine days after infection, appeared normal at necropsy, transmitted the virus to sentinel pigs, but seven out of eight pigs failed to seroconvert. These findings suggest that the H1N7 virus has a low pathogenicity for pigs, resulting in limited virus multiplication which is insufficient to stimulate a detectable primary humoral immune response.

Bovine respiratory syncytial virus protects cotton rats against human respiratory syncytial virus infection

Human respiratory syncytial virus (HRSV) is the most frequent cause of severe respiratory infections in infancy. No vaccine against this virus has yet been protective, and antiviral drugs have been of limited utility. Using the cotton rat model of HRSV infection, we examined bovine respiratory syncytial virus (BRSV), a cause of acute respiratory disease in young cattle, as a possible vaccine candidate to protect children against HRSV infection. Cotton rats were primed intranasally with graded doses of BRSV/375 or HRSV/Long or were left unprimed. Three weeks later, they were challenged intranasally with either BRSV/375, HRSV/Long (subgroup A), or HRSV/18537 (subgroup B). At intervals postchallenge, animals were sacrificed for virus titration and histologic evaluation. Serum neutralizing antibody titers were determined at the time of viral challenge. BRSV/375 replicated to low titers in nasal tissues and lungs. Priming with 10(5) PFU of BRSV/375 effected a 500- to 1,000-fold reduction in peak nasal HRSV titer and a greater than 1,000-fold reduction in peak pulmonary HRSV titer upon challenge with HRSV/Long or HRSV/18537. In contrast to priming with HRSV, priming with BRSV did not induce substantial levels of neutralizing antibody against HRSV and was associated with a delayed onset of clearance of HRSV upon challenge. Priming with BRSV/375 caused mild nasal and pulmonary pathology and did not cause exacerbation of disease upon challenge with HRSV/Long. Our findings suggest that BRSV may be a potential vaccine against HRSV and a useful tool for studying the mechanisms of immunity to HRSV.

Antigenic change in feline calicivirus during persistent infection

To determine if antigenic variation occurred during persistent infection of cats with feline caliciviruses (FCV), nine persistent (progeny) isolates from nine different carrier cats were compared antigenically to the original infecting parent strain, FCV 255, by two-way cross-neutralization tests with rabbit antisera. Five of the nine progeny viruses isolated 35 to 169 days after initial infection were antigenically different from the parent strain. These five isolates represented four distinct antigenic phenotypes. The emergence of four distinctly different antigenic variants from a single parent strain indicates that FCV, like many other RNA viruses, exhibits considerable antigenic heterogeneity during replication in its natural host, and supports the hypothesis that antigenic variation contributes to chronic FCV infection.

A comparison of serological relationships among five ruminant alphaherpesviruses by ELISA

Using enzyme-linked immunosorbent assays the cross reactivity of bovine herpesvirus-1.1, bovine herpesvirus-1.2, caprine herpesvirus-2, cervine (red deer) herpesvirus-1 and rangiferine (reindeer) herpesvirus-1 has been examined using rabbit hyperimmune antisera and convalescent cattle and red deer field sera. Significant cross-reactivity among all the five viruses was demonstrated. A detailed analysis showed that: (1) the two bovine herpesviruses are most closely related, (2) the cervine, caprine and rangiferine viruses are more closely related to the bovine viruses than they are to each other, (3) the cervine herpesvirus is more related to the bovine herpesvirus than to the rangiferine or caprine herpesviruses and (4) the rangiferine virus is more related to the cervine virus than to the bovine and caprine viruses. Cattle and red deer sera reacted most strongly with the bovine and cervine viruses respectively.

Evidence for two serotype G3 subtypes among equine rotaviruses

Ten cultivable equine rotavirus isolates, two of North American, six of British, and two of Irish origin, were compared with standard rotavirus strains and with each other by cross neutralization, neutralization with a panel of monoclonal antibodies (MAbs), hybridization to a simian rotavirus (SA-11) VP7 gene probe, and reaction with rotavirus subgrouping and serotyping MAbs in enzyme-linked immunosorbent assays. Six isolates, two of which had previously been serotyped as G3 by other workers, were found to be serotype G3; one was confirmed to be G5, and three were not related to serotypes G1 to G10. The serotype G3 strains were divisible into two subtypes, G3A and G3B, on the basis of cross neutralization. This division was also apparent in reactions with neutralizing VP7-specific MAbs and in the liquid hybridization assay. Two of the isolates were not bound by either subgroup MAb, six were bound by both subgroup I and II MAbs, and two were bound by only the subgroup I MAb. The assays used in this characterization provide a range of epidemiological information for use in future field investigations.

A novel group A rotavirus G serotype: serological and genomic characterization of equine isolate FI23

Equine rotavirus FI23 was shown to be prototypic of a novel G serotype, provisionally G14, by cross-neutralization and VP7 sequence determination. Although distinct, there are as few as six differing amino acid residues (92, 94, 96, 146, 147, and 221) in the VP7 antigenic regions of FI23 and G3 rotaviruses.

Evaluation of relationships between avian paramyxoviruses isolated from birds of the family Columbidae

The prototype virus for the PMV-7 serotype of avian paramyxoviruses, PMV-7 dove Tennessee/4/75 (Tn 4) and five other isolates obtained from birds of the Columbidae family, which had been shown to be distinct from PMV-1 serotype, were tested for antigenic relationships between themselves and to other avian paramyxoviruses. By serological tests and analysis of structural polypeptides the viruses appeared to be distinct from other avian paramyxoviruses. One isolate appeared to be very closely related to Tn/4. Three other isolates showed only minor relationships to these two but were very closely related to each other. However, the sixth virus, pigeon Japan/Otaru/76, showed high levels of homology in haemagglutination inhibition tests and at least one line of identity in immunodoublediffusion tests with all five of the other isolates.

Independent and disparate evolution in nature of influenza A virus hemagglutinin and neuraminidase glycoproteins

The hemagglutinin (HA) and neuraminidase (NA) external glycoprotein antigens of H1N1 and H3N2 subtypes of epidemiologically important influenza A viruses prevalent during recent decades were subjected to intensive antigenic analysis by four different methods. Prior to serological analysis with polyclonal rabbit antisera, HA and NA antigens of four viruses of each subtype were segregated by genetic reassortment to forestall nonspecific steric hindrance during antigen-antibody combination. This analysis has demonstrated that with respect to antigenic phenotype, HA and NA proteins have evolved at different rates. With H1N1 viruses, an arrest of significant evolution of the NA discordant with the continuing antigenic drift of HA was found in the 1980-1983 period. It is probable that the different and independent rates of evolution of HA and NA reflect the greater selective pressure of HA antibodies, which forces the more rapid emergence of HA escape mutants. The slower antigenic change found for NA further supports the potential for NA-specific infection-permissive immunization as a useful stratagem against influenza.

Characterization of paramyxoviruses isolated from penguins in Antarctica and sub-Antarctica during 1976-1979

Nine paramyxovirus isolates obtained from penguins were tested for antigenic relationships amongst themselves and to other avian paramyxoviruses. One of the isolates was shown to be a lentogenic Newcastle disease virus (NDV), i.e., of PMV-1 serotype. By serological tests and analysis of structural polypeptides the other penguin isolates could be placed into three groups. No relationship with other avian paramyxoviruses could be determined except that six of the penguin viruses, representing two of the groups, showed reaction with a monoclonal antibody raised against NDV Ulster 2C and three of the isolates, representing one of the penguin groups, also reacted with another PMV-1 directed monoclonal antibody.

Antigenic relationships between attenuated and pathogenic strains of Junin virus

Antigenic relationships between attenuated and pathogenic strains of Junin virus (JV) were investigated. Five strains of either human or rodent origin were tested by cross-neutralization assay with hyperimmune antisera, raised in rabbits, against each strain. Polyclonal antisera could be used to distinguish among these JV strains, as the titer values differed significantly with ratios of homologous to heterologous titers, which ranged from 1.3 to 22.3. This demonstrates, independent of their virulence, a heterogeneity among the JV strains tested. The relatedness among JV strains was expressed quantitatively through a dendrogram based on taxonomic distance coefficients. The field strains of JV were grouped into two clusters, according to their geographic origin.

A serological comparison of bovine coronavirus strains

Two bovine coronavirus (BCV) strains from diarrheic calf faeces were adapted to grow in HRT 18 cells and compared in immunofluorescence (IF), haemagglutination inhibition (HAI) and neutralisation (NT) tests with three other strains of BCV and a human coronavirus (HCV) strain obtained from other laboratories. Polyclonal antisera against these 6 viruses were raised in rabbits. No significant differences between viruses were detected by IF. In the HAI test the HCV strain was distinguishable from the 5 BCV strains and serological variation between the BCV strains was shown. HCV could be distinguished by NT test, but all BCV isolates were similar. Two monoclonal antibodies prepared against one of the BCV strains distinguished HCV in all three assays, and detected varying relationships between BCV strains.

Current approaches to the development of vaccines effective against parainfluenza viruses

Infection of infants and children with parainfluenza viruses can lead to serious lower respiratory tract disease. In order to review new information on the genetic organization, epidemiology, and immunobiology of these viruses and of respiratory syncytial virus, WHO, in conjunction with the National Institute of Allergy and Infectious Diseases, held a workshop in Bethesda, MD, USA, 4-5 May 1987. New data on the immunobiology and epidemiology of human parainfluenza 3 virus were presented that should facilitate the development of a vaccine against this pathogen.

Antigenic relatedness between glycoproteins of human respiratory syncytial virus subgroups A and B: evaluation of the contributions of F and G glycoproteins to immunity

The degree of antigenic relatedness between human respiratory syncytial virus (RSV) subgroups A and B was estimated from antibody responses induced in cotton rats by respiratory tract infection with RSV. Glycoprotein-specific enzyme-linked immunosorbent assays of antibody responses induced by RSV infection demonstrated that the F glycoproteins of subgroups A and B were antigenically closely related (relatedness, R approximately 50%), whereas the G glycoproteins were only distantly related (R approximately 5%). Intermediate levels of antigenic relatedness (R approximately 25%) were seen in neutralizing antibodies from cotton rats infected with RSV of the two subgroups. Immunity against the F glycoprotein of subgroup A, induced by vaccinia-A2-F, conferred a high level of protection which was of comparable magnitude against challenge by RSV of either subgroup. In comparison, immunity against the G glycoprotein of subgroup A, induced by vaccinia-A2-G, conferred less complete, but significant, protection. Importantly, in vaccinia-A2-G-immunized animals, suppression of homologous challenge virus replication was significantly greater (13-fold) than that observed for the heterologous virus.

Antigenic relationships between avian paramyxoviruses. II. A combinatorial mathematical model of antigenic kinship

A combinatorial mathematical model describing the antigenic relationships found between different avian paramyxovirus (PMV) serotypes (Lipkind and Shihmanter, 1986) is presented. According to the model, the network of the antigenic interconnections is determined by the specific combinatorial sets of antigenic determinants, some of them being serotype-specific and the others being common to certain other avian PMV serotypes. The suggested model is based on certain postulates concerning PMV virion structure; the bifunctional organization of PMV haemagglutinin-neuraminidase (HN) glycoprotein, its amount per virion and a mechanism of antibody-caused inhibition of its functional activities; the definition of an antigenic determinant as an elementary unit inducing and reacting only with a homologous type of antibodies. The model interprets in specific terms some serological results, in particular the old but mysterious phenomenon of asymmetric cross reactivity.

A new concept of the epidemic process of influenza A virus

Influenza A virus was discovered in 1933, and since then four major variants have caused all the epidemics of human influenza A. Each had an era of solo world prevalence until 1977 as follows: H0N1 (old style) strains until 1946, H1N1 (old style) strains until 1957, H2N2 strains until 1968, then H3N2 strains, which were joined in 1977 by a renewed prevalence of H1N1 (old style) strains. Serological studies show that H2N2 strains probably had had a previous era of world prevalence during the last quarter of the nineteenth century, and had then been replaced by H3N2 strains from about 1900 to 1918. From about 1907 the H3N2 strains had been joined, as now, by H1N1 (old style) strains until both had been replaced in 1918 by a fifth major variant closely related to swine influenza virus A/Hswine1N1 (old style), which had then had an era of solo world prevalence in mankind until about 1929, when it had been replaced by the H0N1 strains that were first isolated in 1933. Eras of prevalence of a major variant have usually been initiated by a severe pandemic followed at intervals of a year or two by successive epidemics in each of which the nature of the virus is usually a little changed (antigenic drift), but not enough to permit frequent recurrent infections during the same era. Changes of major variant (antigenic shift) are large enough to permit reinfection. At both major and minor changes the strains of the previous variant tend to disappear and to be replaced within a single season, worldwide in the case of a major variant, or in the area of prevalence of a previous minor variant. Pandemics, epidemics and antigenic variations all occur seasonally, and influenza and its viruses virtually disappear from the population of any locality between epidemics, an interval of many consecutive months. A global view, however, shows influenza continually present in the world population, progressing each year south and then north, thus crossing the equator twice yearly around the equinoxes, the tropical monsoon periods. Influenza arrives in the temperate latitudes in the colder months, about 6 months separating its arrival in the two hemispheres. None of this behaviour is explained by the current concept that the virus is surviving like measles virus by direct spread from the sick providing endless chains of human influenza A.(ABSTRACT TRUNCATED AT 400 WORDS)

Comparison by the neutralisation assay of pairs of non-cytopathogenic and cytopathogenic strains of bovine virus diarrhoea virus isolated from cases of mucosal disease

Neutralising antibody to non-cytopathogenic and cytopathogenic strains of bovine virus diarrhoea virus (BVDV) was assayed in a microtitre test in which cultures of calf testis cells were stained by the immunoperoxidase method to detect viral replication. Fourteen BVDV strains were compared in cross neutralisation tests with antisera prepared in gnotobiotic calves. Ten of the strains comprised five pairs of non-cytopathogenic and cytopathogenic BVDV. Each pair was isolated from an animal with mucosal disease. All five animals were from five separate outbreaks of the disease. Each pair of strains from the same outbreak was found to be antigenically indistinguishable. In contrast, when the coefficient of antigenic similarity was calculated 11 of 45 comparisons between the pairs and 46 of 91 comparisons between all 14 viruses gave R values that distinguished strains. The observations suggest that an antigenic spectrum within a single related group exists for BVDV strains, rather than distinct serotypes. The findings are also consistent with the suggestion that cytopathogenic strains from natural outbreaks of mucosal disease arise by mutation from non-cytopathogenic virus.

Use of indirect and competitive ELISAs to compare isolates of equine influenza A virus

Antigenic differences within equine-1 and equine-2 isolates of influenza were studied by haemagglutination inhibition tests, indirect ELISA and competition ELISA, using the same antisera. Better differentiation was obtained with the competition ELISA than with the other two tests. All three methods produced similar relationships within the equine-1 isolates but differed in their ability to differentiate the equine-2 isolates where the competition ELISA was superior and produced epidemiologically sensible results. In all three tests, post-infection ferret and horse sera were more useful in discriminating isolates than post-vaccination sera.

Antigenic relationships between avian paramyxoviruses. I. Quantitative characteristics based on hemagglutination and neuraminidase inhibition tests

Comprehensive hemagglutination inhibition (HI) and neuraminidase inhibition (NI) cross reaction tests were performed using 8 of 9 serotypes of avian paramyxoviruses (PMV). The studies were designed as full scale repeating experiments which permitted an adequate statistical treatment and elaboration of quantitative criteria of antigenic kinship. The results have shown diverse antigenic relationships between different avian paramyxovirus (PMV) serotypes which were asymmetric in some cases. The antigenic relationships found by HI test did not always parallel those found by NI tests. The antigenic inter-relationships have been displayed quantitatively in a diagram. This has given a basis for some suggestions concerning: the independent antigenic drift of the HA and Nase antigenic sites of hemagglutinin-neuraminidase (HN) glycoprotein of avian PMVs; a tentative subdivision of the whole group of avian PMVs into two subgroups: the first including PMV-2 and PMV-6 serotypes and the second including PMV-1, PMV-3, PMV-4, PMV-7, PMV-8 and PMV-9 serotypes; the conception that genomic material coding for the HN glycoprotein consists of a "common-to-all-the-PMVs" portion and a "serotype-specific" portion, on one hand, and of a "conserved" portion and a "variable" portion, on the other; the ratios between the portions have been shown to be different for, at least, certain PMV serotypes; the evolutionary pathways of the avain PMV HN antigenic drift.

Detection and prevalence of serotypes of feline syncytial spumaviruses

Three serotypes of feline syncytial virus (FSV) were detected by neutralisation tests: 906, a serotype of low prevalence and 702 and 951 which were serotypes of higher prevalence, between which a minor one-way antigenic difference was detected. Serum antibody in naturally-infected cats in some cases neutralised 951 but not 702 or 906 which suggested that 951 could be considered as a major distinct serotype. An increase in prevalence of antibody to FSV in cats over a 5 year period from 1977-1981 was detected by neutralisation, agar gel immunodiffusion, and fluorescent antibody techniques. Over the 5 year period the prevalence of antibody to the 951 serotype increased and the overall increase in prevalence of antibody to FSV during this period appeared to relate to dissemination of the 951 serotype.

Occurrence and significance of infectious bronchitis virus variant strains in egg and broiler production in the Netherlands

Despite vaccination against Infectious bronchitis virus (IBV) with the Massachusetts type vaccine viruses H120 and H52 in the Netherlands, an increasing number of properly vaccinated flocks have suffered from the disease since 1978. In the years 1978-1982, the virus was isolated from 162 IBV suspected flocks. Cross-virus-neutralization tests showed that the majority (67 per cent) of these isolates belonged to serotypes other than the Massachusetts type, the Connecticut-, Florida-, Iowa 97-, Iowa 609- and JMK serotype. The majority of these Dutch isolates could be divided into 4 serogroups, called D207, D212, D3128 and D3896. Only a few isolates were not related to these serotypes. A survey of 328 flocks for antibody against these serotypes demonstrated that antibody against one or more of these novel serotypes were present in most of the flocks. Experiments demonstrated that vaccination with the H120 vaccine virus was not able to protect chickens against the adverse effects of a challenge with the novel serotypes.

Antigenic relationships between the serotypes of Pasteurella haemolytica demonstrable by enzyme-linked immunosorbent assay (ELISA)

Mice and rabbits were immunised with sodium salicylate extracts (SSE) prepared from each of 12 serotypes of Pasteurella haemolytica, and the antisera to each were used in cross-indirect haemagglutination (IHA) tests and cross-enzyme-linked immunosorbent assays (ELISA) to study antigenic relationships between the serotypes. An indirect micro-ELISA demonstrated common antigenic relationships which were not apparent by IHA. Antisera from both species revealed considerable shared antigenicity between all the serotypes. Rabbit antisera presented clearer differences between the A biotypes on one hand and the T biotypes on the other, the T biotypes exhibiting much less cross-relatedness than that shown between the A serotypes.