Intranasally administered antigen 85B gene vaccine in non-replicating human Parainfluenza type 2 virus vector ameliorates mouse atopic dermatitis

Atopic dermatitis (AD) is a refractory and recurrent inflammatory skin disease. Various factors including heredity, environmental agent, innate and acquired immunity, and skin barrier function participate in the pathogenesis of AD. T -helper (Th) 2-dominant immunological milieu has been suggested in the acute phase of AD. Antigen 85B (Ag85B) is a 30-kDa secretory protein well conserved in Mycobacterium species. Ag85B has strong Th1-type cytokine inducing activity, and is expected to ameliorate Th2 condition in allergic disease. To perform Ag85B function in vivo, effective and less invasive vaccination method is required. Recently, we have established a novel functional virus vector; recombinant human parainfluenza type 2 virus vector (rhPIV2): highly expressive, replication-deficient, and very low-pathogenic vector. In this study, we investigated the efficacy of rhPIV2 engineered to express Ag85B (rhPIV2/Ag85B) in a mouse AD model induced by repeated oxazolone (OX) challenge. Ear swelling, dermal cell infiltrations and serum IgE level were significantly suppressed in the rhPIV2/Ag85B treated mouse group accompanied with elevated IFN-γ and IL-10 mRNA expressions, and suppressed IL-4, TNF-α and MIP-2 mRNA expressions. The treated mice showed no clinical symptom of croup or systemic adverse reactions. The respiratory tract epithelium captured rhPIV2 effectively without remarkable cytotoxic effects. These results suggested that rhPIV2/Ag85B might be a potent therapeutic tool to control allergic disorders.

Recombinant human parainfluenza virus type 2 with mutations in V that permit cellular interferon signaling are not attenuated in non-human primates

The HPIV2 V protein inhibits type I interferon (IFN) induction and signaling. To manipulate the V protein, whose coding sequence overlaps that of the polymerase-associated phosphoprotein (P), without altering the P protein, we generated an HPIV2 virus in which P and V are expressed from separate genes (rHPIV2-P+V). rHPIV2-P+V replicated like HPIV2-WT in vitro and in non-human primates. HPIV2-P+V was modified by introducing two separate mutations into the V protein to create rHPIV2-L101E/L102E and rHPIV2-Delta122-127. In contrast to HPIV2-WT, both mutant viruses were unable to degrade STAT2, leaving virus-infected cells susceptible to IFN. Neither mutant, nor HPIV2-WT, induced significant amounts of IFN-beta in infected cells. Surprisingly, neither rHPIV2-L101E/L102E nor rHPIV2-Delta122-127 was attenuated in two species of non-human primates. This indicates that loss of HPIV2's ability to inhibit IFN signaling is insufficient to attenuate virus replication in vivo as long as IFN induction is still inhibited.

Differential mechanisms of complement-mediated neutralization of the closely related paramyxoviruses simian virus 5 and mumps virus

The complement system is an important component of the innate immune response to virus infection. The role of human complement pathways in the in vitro neutralization of three closely related paramyxoviruses, Simian Virus 5 (SV5), Mumps virus (MuV) and Human Parainfluenza virus type 2 (HPIV2) was investigated. Sera from ten donors showed high levels of neutralization against HPIV2 that was largely complement-independent, whereas nine of ten donor sera were found to neutralize SV5 and MuV only in the presence of active complement pathways. SV5 and MuV neutralization proceeded through the alternative pathway of the complement cascade. Electron microscopy studies and biochemical analyses showed that treatment of purified SV5 with human serum resulted in C3 deposition on virions and the formation of massive aggregates, but there was relatively little evidence of virion lysis. Treatment of MuV with human serum also resulted in C3 deposition on virions, however in contrast to SV5, MuV particles were lysed by serum complement and there was relatively little aggregation. Assays using serum depleted of complement factors showed that SV5 and MuV neutralization in vitro was absolutely dependent on complement factor C3, but was not dependent on downstream complement factors C5 or C8. Our results indicate that even though antibodies exist that recognize both SV5 and MuV, they are mostly non-neutralizing and viral inactivation in vitro occurs through the alternative pathway of complement. The implications of our work for development of paramyxovirus vectors and vaccines are discussed.

Demonstration of 1-year duration of immunity for attenuated Bordetella bronchiseptica vaccines in dogs

Three groups of healthy dogs with low antibody titers to Bordetella bronchiseptica (Bb), canine parainfluenza virus (CPI), and canine adenovirus type 2 (CAV-2) were used in this study. One group was vaccinated with a single dose of monovalent attenuated Bb vaccine and one group with a trivalent vaccine containing attenuated Bb, CPI, and CAV-2; dogs were vaccinated intranasally with a single dose of the respective vaccines. The third group served as unvaccinated controls. All vaccinated dogs subsequently developed serum antibody titers to Bb that persisted for at least 1 year. Following Bb challenge 1 year after vaccination, all vaccinated dogs, regardless of group, showed significantly fewer clinical signs and shed significantly fewer challenge organisms than unvaccinated controls. These results demonstrate that intranasal administration of a single dose of monovalent attenuated Bb vaccine or trivalent vaccine containing attenuated Bb, CPI, and CAV-2 provides 1 year of protection against Bb.

Drug-induced hypersensitivity syndrome associated with a marked increase in anti-paramyxovirus antibody titers in a scleroderma patient

BACKGROUND

Drug-induced hypersensitivity syndrome (DIHS) is characterized by a severe multiorgan hypersensitivity reaction that usually appears after prolonged exposure to certain drugs and may be related to reactivation of herpes viruses. There have been few reports regarding the clinical association of DIHS with pathogens other than herpes viruses.

CASE SUMMARY

We report a case of scleroderma with DIHS associated with paramyxovirus infection. A 61-year-old man with early diffuse cutaneous scleroderma with myositis and progressive interstitial pneumonia developed generalized erythema with high fever 3 weeks after taking sulfamethoxazole/trimethoprim. The diagnosis of DIHS was made based on the patient's history of using an offending drug, clinical manifestations and laboratory data showing peripheral eosinophilia with the presence of atypical lymphocytes. Virological tests showed significant increases of antibody titers against mumps virus and parainfluenza virus type 2, which strongly suggested that paramyxovirus infection occurred during the clinical course of DIHS.

DISCUSSION

These findings suggest that paramyxovirus infection had contributed to the development of DIHS in this patient and that there is a need to seek evidence of other viral infections in some cases of DIHS, especially those without herpes virus reactivation/infection.

Recombinant human parainfluenza virus type 2 vaccine candidates containing a 3' genomic promoter mutation and L polymerase mutations are attenuated and protective in non-human primates

Previously, we identified several attenuating mutations in the L polymerase protein of human parainfluenza virus type 2 (HPIV2) and genetically stabilized those mutations using reverse genetics [Nolan SM, Surman S, Amaro-Carambot E, Collins PL, Murphy BR, Skiadopoulos MH. Live-attenuated intranasal parainfluenza virus type 2 vaccine candidates developed by reverse genetics containing L polymerase protein mutations imported from heterologous paramyxoviruses. Vaccine 2005;39(23):4765-74]. Here we describe the discovery of an attenuating mutation at nucleotide 15 (15(T-->C)) in the 3' genomic promoter that was also present in the previously characterized mutants. We evaluated the properties of this promoter mutation alone and in various combinations with the L polymerase mutations. Amino acid substitutions at L protein positions 460 (460A or 460P) or 948 (948L), or deletion of amino acids 1724 and 1725 (Delta1724), each conferred a temperature sensitivity (ts) phenotype whereas the 15(T-->C) mutation did not. The 460A and 948L mutations each contributed to restricted replication in the lower respiratory tract of African green monkeys, but the Delta1724 mutation increased attenuation only in certain combinations with other mutations. We constructed two highly attenuated viruses, rV94(15C)/460A/948L and rV94(15C)/948L/Delta1724, that were immunogenic and protective against challenge with wild-type HPIV2 in African green monkeys and, therefore, appear to be suitable for evaluation in humans.

An improved method for the recovery of recombinant paramyxovirus vaccine candidates suitable for use in human clinical trials

We describe a method for the generation of clinical grade, live-attenuated vaccines in Vero cells entirely from cDNA plasmids. The entire electroporation procedure can be completed in less than 15 minutes and this is a significant improvement over previous lipid or electroporation based transfection techniques that also involve a heat-shock step. Importantly, the virus preparations can be generated with a minimal use of animal product derived materials, an important consideration for a vaccine candidate that is to be tested in humans. Since it is likely that all live-attenuated parainfluenza virus and pneumovirus vaccines in the future will be generated using reverse genetics, this simplified method provides guidance on how this can be achieved.

Comparison of real-time PCR assays with fluorescent-antibody assays for diagnosis of respiratory virus infections in children

Conventional fluorescent-antibody (FA) methods were compared to real-time PCR assays for detection of respiratory syncytial virus (RSV), influenza virus type A (FluA), parainfluenza virus types 1, 2, and 3 (PIV1, PIV2, and PIV3), human metapneumovirus (MPV), and adenovirus (AdV) in 1,138 specimens from children with respiratory illnesses collected over a 1-year period. At least one virus was detected in 436 (38.3%) specimens by FA and in 608 (53.4%) specimens by PCR (P<0.001). Specimen quality was inadequate for FA in 52 (4.6%) specimens; 13 of these (25%) were positive by PCR. In contrast, 18 (1.6%) specimens could not be analyzed by PCR; 1 of these was positive by FA. The number of specimens positive only by PCR among specimens positive by PCR and/or FA was 18 (7.0%) of 257 for RSV, 18 (13.4%) of 134 for FluA, 25 (64.1%) of 39 for PIV1, 8 (88.9%) of 9 for PIV2, 17 (30.1%) of 55 for PIV3, and 101 (76.5%) of 132 for AdV. MPV was detected in 6.6% of all specimens and in 9.5% of the 702 specimens negative by FA. The mean number of virus copies per milliliter in specimens positive by both PCR and FA was significantly higher, at 6.7x10(7), than that in specimens positive only by PCR, at 4.1x10(4) (P<0.001). The PCR assays were significantly more sensitive than FA assays for detecting respiratory viruses, especially parainfluenza virus and adenovirus. Use of real-time PCR to identify viral respiratory pathogens in children will lead to improved diagnosis of respiratory illness.

Exposure to human respiratory viruses among urban performing monkeys in Indonesia

Performing monkeys, a common phenomena in Asia, occupy a unique urban niche that comprises a number of factors influencing the likelihood of cross-species transmission of pathogens. Here we present the first documented evidence of exposure to measles, rubella, and parainfluenza in a population of performing monkeys. Evidence of exposure to these endemic human respiratory viruses in the performing monkeys confirms human-to-primate transmission and suggests the possibility of primate-to-human transmission. Urban animal markets, the likely source of these performing monkeys, may represent an environment conducive to the mixing of animals and pathogens, making these monkeys a potential conduit for infectious agents passing from a variety of animals found in animal markets to humans. The potential significance of these results to human public health and the unique contexts of disease transmission associated with the urban ecology of the performance monkeys are discussed. Given the level of overseas travel, this potential threat is not confined solely to Asia.

Live-attenuated intranasal parainfluenza virus type 2 vaccine candidates developed by reverse genetics containing L polymerase protein mutations imported from heterologous paramyxoviruses

Live-attenuated recombinant human parainfluenza virus type 2 (rHPIV2) vaccine candidates were created using reverse genetics by importing known attenuating mutations in the L polymerase protein from heterologous paramyxoviruses into the homologous sites of the HPIV2 L protein. Four recombinants (rF460L, rY948H, rL1566I, and rS1724I) were recovered and three were attenuated for replication in hamsters. The genetic stability of the imported mutations at three of the four sites was enhanced by use of alternative codons or by deletion of a pair of amino acids. rHPIV2s bearing these modified mutations exhibited enhanced attenuation. The genetically stabilized mutations conferring a high level of attenuation will be useful in generating a live-attenuated virus vaccine for HPIV2.

[Seroepidemiological surveillance of human parainfluenza viruses (HPIVs) types 2 and 3 in an infantile population selected in Havana City]

The presence of antibodies against human parainfluenza viruses type 2 and 3 was studied in 1 793 sera from an infantile population under 14 years old. The hemagglutination inhibition technique was used for screening the clinical samples. Of the total of analyzed sera, 1 382 (77.1%) were positive. The presence of antibodies against type 2 was confirmed in 320 of them (17.8%), and against type 3 in 334 (18.6%). The simultaneous seropositivity predominated in 805 (44.9%). The circulation of human parainfluenza viruses was corroborated during all the months of the year and in all the analyzed age groups. It was observed an increase in the positivity percentages with age.

The value of virus serology in epidemiological studies of acute otitis media in children

BACKGROUND

Acute otitis media (AOM) is a major health problem in young children. There is a general conception that AOM is a bacterial disease but with the availability of sensitive diagnostic methods, it has gradually become evident that viruses play an important role in the pathogenesis of AOM. Paired blood samples are seldom taken from infants although valuable information could be obtained by serological methods. During the recent Finnish Otitis Media (FinOM) Cohort Study, in addition to nasopharyngeal aspirates (NPA) and middle ear fluids (MEF), paired acute and convalescent serum samples were collected from children with AOM.

OBJECTIVES

To establish the diagnostic value of serological methods in etiological and epidemiological studies of AOM.

STUDY DESIGN

A complete set of NPA, MEF, and paired sera was collected during 447 events of AOM experienced by 179 children between 2 months and 2 years of age. Antigens of respiratory syncytial virus (RSV), adenoviruses, influenza A and B, and parainfluenza types 1-3 in NPAs and MEFs were detected by time-resolved fluoroimmunoassay (TR-FIA), and antibody titers were determined by complement fixation test (CFT) or by enzyme immunoassay.

RESULTS

A total of 163 virus-positive events were identified. Of those, only 34 were positive by TR-FIA and by serology. From 48 events a positive result was obtained only by TR-FIA and from 81 only by serology.

CONCLUSION

Although serological methods are usually of little use in clinical practice, epidemiological studies clearly gain value if serology is included. The number of virus-positive findings dramatically increased by including serological tests in the diagnostic work-up of these AOM events.

Parainfluenza viruses

Human parainfluenza viruses (HPIV) were first discovered in the late 1950s. Over the last decade, considerable knowledge about their molecular structure and function has been accumulated. This has led to significant changes in both the nomenclature and taxonomic relationships of these viruses. HPIV is genetically and antigenically divided into types 1 to 4. Further major subtypes of HPIV-4 (A and B) and subgroups/genotypes of HPIV-1 and HPIV-3 have been described. HPIV-1 to HPIV-3 are major causes of lower respiratory infections in infants, young children, the immunocompromised, the chronically ill, and the elderly. Each subtype can cause somewhat unique clinical diseases in different hosts. HPIV are enveloped and of medium size (150 to 250 nm), and their RNA genome is in the negative sense. These viruses belong to the Paramyxoviridae family, one of the largest and most rapidly growing groups of viruses causing significant human and veterinary disease. HPIV are closely related to recently discovered megamyxoviruses (Hendra and Nipah viruses) and metapneumovirus.

Development of internal controls for the Luminex instrument as part of a multiplex seven-analyte viral respiratory antibody profile

The ability of the Luminex system to simultaneously quantitate multiple analytes from a single sample source has proven to be a feasible and cost-effective technology for assay development. In previous studies, my colleagues and I introduced two multiplex profiles consisting of 20 individual assays into the clinical laboratory. With the Luminex instrument's ability to classify up to 100 distinct microspheres, however, we have only begun to realize the enormous potential of this technology. By utilizing additional microspheres, it is now possible to add true internal controls to each individual sample. During the development of a seven-analyte serologic viral respiratory antibody profile, internal controls for detecting sample addition and interfering rheumatoid factor (RF) were investigated. To determine if the correct sample was added, distinct microspheres were developed for measuring the presence of sufficient quantities of immunoglobulin G (IgG) or IgM in the diluted patient sample. In a multiplex assay of 82 samples, the IgM verification control correctly identified 23 out of 23 samples with low levels (<20 mg/dl) of this antibody isotype. An internal control microsphere for RF detected 30 out of 30 samples with significant levels (>10 IU/ml) of IgM RF. Additionally, RF-positive samples causing false-positive adenovirus and influenza A virus IgM results were correctly identified. By exploiting the Luminex instrument's multiplexing capabilities, I have developed true internal controls to ensure correct sample addition and identify interfering RF as part of a respiratory viral serologic profile that includes influenza A and B viruses, adenovirus, parainfluenza viruses 1, 2, and 3, and respiratory syncytial virus. Since these controls are not assay specific, they can be incorporated into any serologic multiplex assay.

Development of hypertrophic osteodystrophy and antibody response in a litter of vaccinated Weimaraner puppies

Two different vaccination protocols were compared with regard to the development of hypertrophic osteodystrophy (HOD) (also termed metaphyseal osteopathy) and effectiveness of immunisation in a litter of 10 Weimaraner puppies. Five puppies (group 1) were vaccinated with a modified live canine parvovirus vaccine (CPV) and then two weeks later with a trivalent vaccine containing modified live canine distemper virus and adenovirus type 2 combined with a Leptospira bacterin (DHL). The CPV and DHL vaccine protocols were administered a further two times, at two-week intervals. Group 2 was vaccinated with three consecutive multivalent vaccines containing modified live canine distemper virus, canine parvovirus, parainfluenza and adenovirus type 2 combined with a Leptospira bacterin, at four-week intervals. All puppies were first vaccinated at the age of eight weeks. Three dogs in group 1 developed HOD, while all five dogs in group 2 developed HOD during the study period. Dogs in group 2 had more episodes of HOD than those in group 1. Dogs in group 1 developed higher antibody titres to canine distemper virus and parvovirus compared with those in group 2. Only two out of the 10 dogs developed protective antibody titres to parvovirus. The results of this study suggest that the two different vaccination protocols affected the pattern of appearance of HOD and immunisation in this litter of Weimaraner puppies. The results obtained and the previously reported data suggest that a larger controlled study is needed to further elucidate the effect of different vaccination protocols on HOD and immunisation in Weimaraner puppies.

Construction of a live-attenuated bivalent vaccine virus against human parainfluenza virus (PIV) types 1 and 2 using a recombinant PIV3 backbone

PIV1 and PIV2 are important agents of pediatric respiratory tract disease. We are developing live-attenuated vaccines against these viruses. We earlier constructed a PIV3/PIV1 antigenic chimeric virus, designated rPIV3-1, in which the hemagglutinin-neuraminidase (HN) and fusion (F) proteins of wild type rPIV3 were replaced by their PIV1 counterparts. In the present study, rPIV3-1 was used as a vector to express the HN protein of PIV2 to generate a single virus capable of inducing immunity to both PIV1 and PIV2. The PIV2 HN open reading frame was expressed from an extra gene cassette, under the control of PIV3 cis-acting transcription signals, inserted between the F and HN genes of rPIV3-1. The recombinant derivative, designated rPIV3-1.2HN, was readily recovered and exhibited a level of temperature sensitivity and in vitro growth similar to that of its parental virus. The rPIV3-1.2HN virus was restricted in replication in both the upper and lower respiratory tracts of hamsters compared with rPIV3-1, identifying an attenuating effect of the PIV2 HN insert in hamsters. rPIV3-1.2HN elicited serum antibodies to both PIV1 and PIV2 and induced resistance against challenge with wild type PIV1 or PIV2. Thus, rPIV3-1.2HN, a virus attenuated solely by the insertion of the PIV2 HN gene, functioned as a live attenuated bivalent vaccine candidate against both PIV1 and PIV2.

African green monkeys provide a useful nonhuman primate model for the study of human parainfluenza virus types-1, -2, and -3 infection

Human parainfluenza virus (HPIV) types-1, -2, and -3 are significant causes of both upper and lower respiratory tract disease in infants and children. Although there are two live attenuated vaccines for the prevention of HPIV-3 disease in phase 1 clinical trials, vaccines are not currently available for prevention of HPIV-1 or -2 disease. Our laboratory is developing candidate vaccines for the prevention of HPIV-1, -2, and -3 disease, and a suitable nonhuman primate model is needed for evaluation of these vaccine candidates prior to administration to humans. We evaluated the replication of HPIV-1 and -2 in six different species of nonhuman primates and found both viruses to replicate most efficiently in African green monkeys and chimpanzees. We then compared the replication of HPIV-3 in African green monkeys to that in rhesus macaques, which we have used previously, and found that HPIV-3 replicated to higher titer in African green monkeys. In summary, African green monkeys provide a very useful nonhuman primate for the evaluation of HPIV-1, -2, and -3 vaccine candidates, especially for the evaluation of various combinations of these PIV vaccines and for vaccine strategies that employ sequential immunization.

A live attenuated recombinant chimeric parainfluenza virus (PIV) candidate vaccine containing the hemagglutinin-neuraminidase and fusion glycoproteins of PIV1 and the remaining proteins from PIV3 induces resistance to PIV1 even in animals immune to PIV3

Using a reverse genetics system for PIV3, we previously recovered recombinant chimeric PIV3-PIV1 virus bearing the major protective antigens of PIV1, the hemaglutinin-neuraminidase and fusion proteins, on a background of PIV3 genes bearing temperature sensitive (ts) and attenuating mutations in the L gene. Immunization of hamsters with this virus, designated rPIV3-1.cp45L, induced a high level of resistance to replication of wild type (wt) PIV1 and, surprisingly, also induced a moderate amount of restriction of the replication of PIV3 challenge virus. This suggested that some immunity is conferred by the internal PIV3 proteins shared by the two viruses. In the present study, we found that the immunity to PIV3 conferred by infection with rPIV3-1.cp45L is short-lived and completely disappeared four months after immunization, whereas resistance to replication of PIV3 induced by prior infection with PIV3 remains high even after an interval of four months. Since a live attenuated PIV1 vaccine such as the chimeric rPIV3-1.cp45L virus will likely be given to infants after a live attenuated PIV3 vaccine in a sequential immunization schedule, we examined the immunogenicity and efficacy of rPIV3-1.cp45L against PIV1 challenge in animals with and without prior immunity to PIV3. rPIV3-1.cp45L efficiently infected hamsters previously infected with wt or attenuated PIV3, but there was approximately a five-fold reduction in replication of rPIV3-1. cp45L virus in the PIV3-immune animals. This reduction in replication of rPIV3-1.cp45L in PIV3-immune animals was accompanied by a significant decrease in efficacy against PIV1 challenge. However, rPIV3-1.cp45L immunization of PIV3-immune animals induced a vigorous serum antibody response to PIV1 and reduced replication of PIV1 challenge virus 1000-fold in the lower respiratory tract and 25 to 200-fold in the upper respiratory tract. This study demonstrated that the recombinant chimeric rPIV3-1.cp45L candidate vaccine can induce immunity to PIV1 even in animals immune to PIV3. This establishes the feasibility of employing a sequential immunization schedule in which a recombinant chimeric rPIV3-1.cp45L vaccine is given following a live attenuated PIV3 vaccine.

Isolation of monoclonal antibodies directed against the V protein of human parainfluenza virus type 2 and localization of the V protein in virus-infected cells

Two monoclonal antibodies (mAbs) specific for the human parainfluenza virus type 2 (hPIV-2) V protein were obtained by immunizing mice with the V protein recombinantly expressed in Escherichia coli. Both mAbs were found to react with the V protein in ELISA and in Western blot analysis. Using these mAbs and previously obtained mAbs specific for hPIV-2 nucleoprotein (NP) or hPIV-2 phospho-(P) protein, we examined the intracellular distributions of the V, P and NP proteins in hPIV-2-infected cells by indirect immunofluorescence analyses. The P and NP proteins were organized in numerous granules in the cytoplasm of hPIV-2 infected cells. In contrast, the V protein showed diffuse nuclear and cytoplasm distributions.

Mapping of domains on the human parainfluenza virus type 2 nucleocapsid protein (NP) required for NP-phosphoprotein or NP-NP interaction

The epitopes recognized by 41 monoclonal antibodies directed against the nucleocapsid protein (NP) of human parainfluenza virus type 2 (hPIV-2) were mapped on the primary structure of the hPIV-2 NP protein by testing their reactivities with deletion mutants. By Western immunoblotting using these monoclonal antibodies, the analysis of deletion mutants of the hPIV-2 NP protein was performed to identify the region essential for NP-NP interaction and phosphoprotein (P)-binding sites on the NP protein. The results indicate that the N-terminal 294 aa of the NP protein are all required for NP-NP self-assembly, and that two C-terminal parts of the NP protein are essential for NP-P binding: one region, aa 295-402, is required for binding to the C-terminal part of the P protein and another region, aa 403-494, to the N-terminal part of the P protein.

Parainfluenza virus infection among adults hospitalized for lower respiratory tract infection

To better define the contribution of human parainfluenza viruses (HPIVs) to lower respiratory tract infection in adults, we tested acute- and convalescent-phase serum specimens from hospitalized adults participating in a population-based prospective study of lower respiratory tract infection during 1991-1992. We tested all available specimens from the epidemic seasons for each virus and approximately 300 randomly selected specimens from the corresponding off-seasons for antibodies to HPIV-1, HPIV-2, or HPIV-3. During the respective epidemic season, HPIV-1 infection was detected in 18 (2.5%) of 721 and HPIV-3 infection in 22 (3.1%) of 705 patients with lower respiratory tract infection. Only 2 (0.2%) of 1,057 patients tested positive for HPIV-2 infection. No HPIV-1 infections and only 2 (0.7% of 281 patients tested) HPIV-3 infections were detected during the off-seasons. HPIV-1 and HPIV-3 were among the four most frequently identified infections associated with lower respiratory tract infection during their respective outbreak seasons.

Direct detection of respiratory syncytial virus, parainfluenza virus, and adenovirus in clinical respiratory specimens by a multiplex reverse transcription-PCR assay

Diagnosis of respiratory virus infections currently involves detection by isolation or antigen detection, which usually identifies only a single suspected agent. To permit identification of more than one respiratory virus in clinical specimens, a rapid detection method involving a single-step, multiplex reverse transcription-PCR (RT-PCR) assay was developed. The assay included five primer sets that amplified the RNA of respiratory syncytial virus subtypes A and B, parainfluenza virus types 1, 2, and 3, and adenovirus types 1 to 7. Initially the assay was tested on tissue culture-grown virus and was found to be specific for all 12 prototype viruses tested, with no interassay cross amplification or amplification of other respiratory viruses. Assay sensitivity allowed a detection range of 0.2 50% tissue culture infectious dose (TCID50) for adenovirus to 250 TCID50 for parainfluenza virus type 1. The multiplex RT-PCR assay was also able to directly detect viruses in respiratory specimens, with virus being detected in 41 of 112 samples as compared to 34 of 112 samples detected by direct immunofluorescence or antigen detection following specimen culture. This suggests that the multiplex RT-PCR assay can be used as a rapid and sensitive diagnostic method for major respiratory viruses.

Respiratory virus antibodies in adults of a Norwegian community: prevalences and risk factors

BACKGROUND

The aims were to examine prevalences as well as demographic and environmental predictors of respiratory virus antibodies in serum.

METHODS

In a cross-sectional study of 18-73 year old Norwegian adults a random stratified sample (n = 1512) was invited to attend an examination at an outpatient clinic. Seven respiratory virus antibodies were assessed by the complement fixation test.

RESULTS

The attendance rate was 84%. The most frequent virus antibodies with titre of > or = 1:8 were influenza virus type A with a population standardized prevalence of 44%, adenovirus 25% and influenza virus type B 22%. The prevalences of antibodies against parainfluenza virus type 1, 2 and 3 increased with age. Smokers compared to non-smokers had an adjusted odds ratio (OR) of 1.7 (95% confidence interval [CI]: 1.3-2.4) for having one or more of the seven examined virus antibodies. The presence of one or more of the virus antibodies increased from summer to winter months (adjusted OR = 1.3 per month; 95% CI: 1.2-1.4) and it was higher in occupational dust or gas exposed smokers (adjusted OR = 2.0; 95% CI: 1.1-3.7) compared with unexposed smokers.

CONCLUSIONS

Ageing, smoking, occupational dust or gas exposure as well as season of the year may thus be predictors for levels of respiratory virus antibodies in adults. These observations should be taken into account when comparing prevalences of virus antibodies in various communities as well as when examining the relationship between presence of virus antibodies and airway disease.

Distinct hemagglutinin and neuraminidase epitopes involved in antigenic variation of recent human parainfluenza virus type 2 isolates

A panel of fourteen neutralizing anti-HN monoclonal antibodies (mAbs) to the prototype Greer strain of human parainfluenza virus type 2 (PI2) was used to determine the extent of antigenic variation in recent virus isolates. Competitive binding analysis with the mAbs indicated the presence of at least five distinct antigenic sites (I to V) on the HN glycoprotein molecule. MAbs recognizing different antigenic sites were found to be associated with the hemagglutinin (sites I, IV and V), hemagglutinin and neuraminidase (site II), or neuraminidase (site III) activities. The location of two distinct epitopes identifying the neuraminidase sites (II and III) was further verified from the generation of escape mutants. Antibodies directed to sites I and III failed to show any detectable binding or neutralizing activity against a number of natural PI2 virus isolates collected in Texas between 1986 and 1987. Interestingly, these natural variants, unlike the prototype virus, did not show any detectable neuraminidase activity with fetuin as a substrate and the enzyme activity was only detected with N-acetylneuramin-lactose as an alternative substrate. Despite the observed variation in the antigenic sites, primary infection with the prototype virus or the natural variants generated a protective immune response against challenge infection with the other virus strains.

Antigenic and structural properties of a paramyxovirus simian virus 41 (SV41) reveal a close relationship with human parainfluenza type 2 virus

Seven structural component proteins of a paramyxovirus simian virus 41 (SV41) were identified with the aid of monoclonal antibodies prepared against SV41 and human parainfluenza type 2 virus (PIV2). The nucleoprotein is antigenically very close to that of PIV2, while it is comparatively far from that of simian virus 5 (SV5). The hemagglutinin-neuraminidase (HN) protein showed no immunological relationship to either of the HN proteins of PIV2 or SV5. The amino acid sequence of the SV41 HN protein was deduced from the nucleotide sequence of its HN gene and revealed that the SV41 HN is unexpectedly close to the PIV2 HN (61.2% identity in amino acid sequence), while the SV5 HN showed only 48.3% identity with the PIV2 HN. The SV41 HN is also related to the SV5 HN (51.3% identity); thus, the SV41 HN is phylogenetically situated between the PIV2 and SV5 HNs. These results indicate that SV41 is the virus closest to PIV2 at present.

Extensive antigenic diversity among human parainfluenza type 2 virus isolates and immunological relationships among paramyxoviruses revealed by monoclonal antibodies

A panel of 128 monoclonal antibodies (MAbs) directed against hemagglutinin-neuraminidase (HN), fusion (F), matrix (M), and polymerase (P) proteins, and nucleoprotein (NP) of the Toshiba strain of human parainfluenza type 2 virus (PIV2) was prepared to examine the antigenic relationships among clinical isolates of PIV2 and among paramyxoviruses by indirect enzyme-linked immunosorbent assays. The HN proteins of 18 clinical isolates of PIV2 showed extensive antigenic diversity: 23 of 33 anti-HN MAbs showed no or limited reactivity to many isolates, while other structural proteins were antigenically well conserved. Some anti-HN MAbs recognizing conserved epitopes of the isolates exhibited two types of neutralizing activity, that is, these antibodies inhibited viral infectivity through attachment inhibition or fusion inhibition. This result also showed the presence of a potential third function of the HN protein which might affect the fusing activity of the F protein besides the hemagglutinating and neuraminidase activities. Many of the anti-NP and anti-P MAbs reacted with simian virus 41 (SV41) and simian virus 5 (SV5), whereas a few reacted with mumps virus or PIV4. Two of 6 anti-F MAbs reacted with SV41. None of the 128 MAbs showed reactivity with PIV1, PIV3, Newcastle disease virus (NDV), and measles virus. This result confirmed antigenic proximity of SV5 and SV41 to PIV2 and revealed comparatively restricted immunological relatedness among PIV2, PIV4, and mumps virus.

Chlamydia trachomatis and parainfluenza 2 virus: a shared antigenic determinant?

A tracheal aspirate from which parainfluenza 2 (PI-2) virus but not chlamydiae was isolated demonstrated positive immunofluorescence of elementary body- and reticulate body-like particles on direct examination with anti-chlamydia monoclonal antibodies (Syva Co.). In subsequent studies, we found this reagent to show specific staining of this strain of PI-2 as well as of 3 of 18 additional PI-2 strains that were evaluated.

Immunization against multiple viruses by using solid-matrix-antibody-antigen complexes

We have previously shown that mice immunized with solid-matrix-antibody-antigen (SMAA) complexes in the absence of adjuvants show vigorous humoral and cell-mediated immune responses to the immunizing antigen. Here we report that various proteins involved in inducing protective immune responses to different viruses can easily and simply be incorporated into SMAA complexes and that such complexes act as powerful multivalent immunogens. Construction of such SMAA complexes may be one of the most practical and effective ways of producing multivalent subunit vaccines for use in humans and animals.

Enzyme immunoassays for detection of IgG and IgM antibodies to parainfluenza types 1, 2 and 3

Quantitative enzyme immunoassays for parainfluenza type 1, 2 and 3 IgG antibodies were developed. Serum specimens were tested at a single dilution of 1:1000 and results expressed in units by the use of a standard curve. The unit values correlated well with titres obtained by testing the same specimens in serial dilutions. All serum pairs with significant titre rises also showed significant rises in unit values. Parainfluenza IgG and IgM serology was evaluated in 66 patients with a proven parainfluenza infection. Diagnostic IgG antibody increases were detected in 70, 69 and 87% of parainfluenza type 1, 2 and 3 infections, respectively. Heterologous titre rises between parainfluenza types 1 and 3 were common. IgM antibodies were detected in 42% of the patients, most commonly in those below two years of age and rarely in adults.

Comparison between parainfluenza virus type 2 and simian virus 5: monoclonal antibodies reveal major antigenic differences

Marked differences in the apparent Mrs of the HN, NP and F proteins of simian virus 5 (SV5) and parainfluenza virus type 2 (PF-2) were revealed by SDS-PAGE. To examine the antigenic relationships between SV5, PF-2 and other paramyxoviruses, monoclonal antibodies (MAbs) specific to PF-2 were isolated. These antibodies had specificities for the HN, NP and P proteins and together with 54 MAbs to SV5 were tested for their ability to react with SV5, PF-2, PF-3, mumps and measles virus proteins. Most of these MAbs (55 out of 60) reacted with homologous virus only. However, five reacted with both SV5 and PF-2. These antibodies had reactivities to the NP, M and P proteins. Furthermore, one of the antibodies with reactivity to the P protein also reacted with mumps virus. Although none of the 21 MAbs with specificities for the HN protein of either SV5 or PF-2 cross-reacted with heterologous virus, some antigenic similarities between the HN protein of SV5 and PF-2 could be detected. This was demonstrated by raising a series of polyclonal antisera to purified preparations of SV5 or PF-2 HN proteins in BALB/c mice, and testing for their ability to neutralize both SV5 and PF-2 and also to immunoprecipitate the HN proteins of these viruses. Surprisingly, while low levels of cross-neutralizing antibody could be detected in some sera (e.g. neutralization of SV5 1:1600 and of PF-2 1:80), other sera with similar neutralization titres against homologous virus failed to neutralize heterologous virus. Furthermore, only a minority of the anti-HN antisera showed any immune-precipitating activity against the heterologous HN protein.

The role of parainfluenza viruses in inspiratory difficulties in children

Viral findings were prospectively studied in middle and lower respiratory tract infections in 449 hospitalized children during a 12-month follow-up period. A viral aetiology was found in 30 of the 65 children (46%) with inspiratory difficulties. Parainfluenza viruses were the infective agents in 24 of the 30 cases with viral diagnoses (80%), type 2 being the most prominent. There were 38 cases of parainfluenza infections, type 2 being the infective agent in 58% of the 24 cases of parainfluenza infections with inspiratory difficulties but in only 21% of the 14 cases of parainfluenza infections without inspiratory difficulties. Type 2 parainfluenza virus produced inspiratory difficulties in 82% of the cases as opposed to 56 and 50% of the cases for type 1 and 3, respectively. It is concluded that the type 2 parainfluenza virus has a particular association with inspiratory difficulties in children. Viral diagnosis was reached using direct antigen detection in nasopharyngeal specimens by radioimmunoassay in 59% and using complement fixation serology in 76% of parainfluenza infections. Direct antigen detection was especially useful in infants. We suggest that direct antigen detection should be used as a primary virological diagnostic method in small children with middle and lower respiratory tract infections.

[Detection of antibodies against infectious viral laryngotracheitis and parainfluenza 2 in dogs bred in Czechoslovakia]

A total of 398 blood serums of dogs of various breeds and age categories, coming from 72 places in Bohemia and Slovakia, were examined for the content of haemagglutination-inhibiting (HI) antibodies to the infectious laryngotracheitis virus (CADV-2) and parainfluenza 2 virus (CPIV-2). Out of this total number, 203 serums (51.1%) reacted against CADV-2 in titres from 1:16 to 1:2048 and 115 serums (28.9%) against CPIV-2 in titres from 1:2 to 1:256. The results indicate that the dog population is considerably infected with viruses affecting the respiratory organs.

Immunological relationships between mumps virus and parainfluenza viruses studied with monoclonal antibodies

The immunological relationships between mumps virus and parainfluenza viruses were investigated with 74, 78 and 80 previously developed monoclonal antibodies directed against five major structural proteins of mumps virus, Sendai virus (a murine parainfluenza type 1 virus) and parainfluenza type 3 virus. These monoclonal antibodies were reacted with the three viruses, with parainfluenza type 2 virus and with Newcastle disease virus (NDV) in ELISA and immunofluorescence (IF) tests. In addition, immunoprecipitation tests with [35S]methionine-labelled extracellular virions were carried out with cross-reacting monoclonal antibodies. None of all 232 monoclonal antibodies against the three viruses cross-reacted with either parainfluenza type 2 virus or NDV in ELISA and IF tests. In the collection of 74 mumps virus monoclonal antibodies, three directed against the nucleocapsid (NP) protein, polymerase protein, and fusion protein cross-reacted with Sendai virus. Two Sendai virus monoclonal antibodies directed against two different epitopes of the haemagglutinin-neuraminidase (HN) protein cross-reacted with parainfluenza type 3 virus. Six other Sendai virus monoclonal antibodies directed against four different epitopes of the HN protein and one directed against the NP protein cross-reacted with mumps virus. Eight out of 80 monoclonal antibodies directed against parainfluenza type 3 virus cross-reacted with Sendai virus. One was directed against the HN protein, four were directed against a minimum of two epitopes of the matrix protein and three were directed against three different epitopes of the NP protein. The different cross-reactions found show that Sendai virus is antigenically related to both mumps virus and parainfluenza type 3 virus. In contrast, no antigenic relationship could be demonstrated between mumps virus and parainfluenza type 3 virus.

Avidity of IgG antibodies against mumps, parainfluenza 2 and Newcastle disease viruses after mumps infection

Paired serum samples from 39 patients with recent mumps infection were assayed for IgG antibodies against mumps, parainfluenza 2 and Newcastle disease virus (NDV). A modified enzyme immunoassay was used, giving separate estimates of high avidity antibodies (EHAA) and total specific antibodies (ETSA). A marked cross-reaction was seen between mumps and parainfluenza 2 virus, with changes of ETSA between paired samples of about the same magnitude against both these viruses. The mean change of EHAA against mumps was, however, significantly greater than that against parainfluenza 2. There were 16 patients who had a change of ETSA greater against parainfluenza 2 than against mumps. When the EHAA responses were compared, there were only 8 such patients. The responses against NDV were negligible. Estimation of antibody avidity, even by the arbitrary method used, can distinguish between homotypic and cross-reactive heterotypic antibodies after mumps infection. The implications for expressing the results of enzyme immunoassay are discussed.

Rapid diagnosis of respiratory virus infections in patients with acute respiratory disease

Viral respiratory infections represent a significant segment of the total respiratory disease spectrum; however, until recently the laboratory diagnosis of viral respiratory infections was relatively inefficient. Development of new and improved immunologic assay systems has paved the way for accurate and reliable rapid diagnostic tests that detect viral antigens in clinical specimens. We conducted a careful and elaborate study in which radioimmunoassay for antigen detection was compared with a battery of tissue culture systems for viral isolation and identification. Using a fine plastic catheter, a specimen of mucus was aspirated from the nasopharynx of patients with clinical signs and symptoms of acute viral upper respiratory tract infections. Each specimen was divided into two portions; one was used to inoculate a variety of tissue culture cell lines and the other was used for radioimmunoassay tests for influenza A and B, adenovirus, parainfluenza 1, 2, and 3, and respiratory syncytial virus. Radioimmunoassay results compared very favorably with the tissue culture data with only one exception--adenovirus. Essentially this degree of accuracy and reproducibility was obtained with an enzyme-linked immunosorbent assay test, which has replaced radioimmunoassay. Tissue cultures are still used for backup, but with a rapid antigen detection system in place, coupled with a modern computer program to facilitate the laboratory data to the clinician, considerable strides have been made, and will continue to be made, in the diagnosis and therapy of viral respiratory tract infections.

Serological diagnosis of parainfluenza virus infections by enzyme immunoassay with special emphasis on purity of viral antigens

Enzyme immunoassay (EIA) for parainfluenza virus type 1, 2, and 3 antibodies was compared with the complement fixation test (CF) as a diagnostic method in 180 patients with respiratory symptoms. The CF test detected rises in parainfluenza virus antibodies in 30 cases, whereas EIA detected 47 rises. Patients with antibody rises in parainfluenza or mumps virus antibodies were studied for cross-reactions by CF, hemagglutination inhibition (HAI), and EIA using purified viral envelope glycoprotein and nucleocapsid preparations. All methods showed marked cross-reactivity between parainfluenza virus type 1 and 3 antibodies. Mumps virus infection often raised heterologous antibodies even against purified viral antigens. Rabbit antisera produced against viral envelope glycoproteins showed heterologous antibody responses between parainfluenza 1 and 3 antibodies and between parainfluenza 1 and mumps antibodies by HAI, EIA, and immunoprecipitation. The cross-reactive antibodies were usually directed against both of the envelope glycoproteins, HN and F proteins, of the viruses.

Viral antibody screening system that uses a standardized single dilution immunoglobulin G enzyme immunoassay with multiple antigens

We present an enzyme-linked immunosorbent assay (ELISA) system for the simultaneous determination of immunoglobulin G antibodies directed against several viruses. Antibodies to up to eight different viruses could be determined for three different sera on one microtitration plate. After subtraction of the absorbance values obtained with the control antigens, the viral antigen absorbancies were expressed as percentages of the absorbance obtained with a pooled immunoglobulin standard. This value, the relative antibody activity, was rapidly calculated by means of a computer directly connected to the ELISA photometer and was stored on magnetic disks, thereby facilitating seroepidemiological studies. The reproducibility of the relative antibody activity was calculated to at best +/- 3.6% (standard deviation) in an intraassay test and to at worst +/- 20.4% (standard deviation) in an interassay test. Each serum was analyzed only at a dilution of 1/75. The sensitivity of this single-dilution ELISA (SD-ELISA) method for the detection of titer rises was compared with those of conventional methods, mostly complement fixation but also hemagglutination inhibition. A total of 142 of 155 (92%) paired sera showing fourfold complement fixation or hemagglutination inhibition rises also showed significant results in SD-ELISA. A total of 22 of 57 (39%) significant relative antibody activity rises were significant in complement fixation or hemagglutination inhibition. Overall, up to twice as many significant titer rises could be detected with SD-ELISA. Most of these seemed to have a sound correlation with clinical data. The specificity of SD-ELISA was found to be similar to that of complement fixation, with some cross-reactions occurring between herpes simplex and varicella-zoster virus antigens and between parainfluenza viruses. We have found SD-ELISA to be a valuable clinical virological tool that supplements conventional serology.

Role of parainfluenza virus-specific IgE in pathogenesis of croup and wheezing subsequent to infection

In order to determine the role of parainfluenza virus-specific IgE antibody production and release of histamine in the pathogenesis of lower respiratory disease caused by parainfluenza virus infection, we studied 84 infants and children at the time of parainfluenza virus infection. Parainfluenza virus-IgE antibody was detected in samples of nasopharyngeal secretions by means of an enzyme-linked immunosorbent assay, and histamine content of nasopharyngeal secretions was determined by a fluorometric technique. Virus-specific IgE responses appeared earlier and were of greater magnitude in patients with croup, wheezing, and croup with wheezing caused by parainfluenza virus infection than in patients with parainfluenza virus-induced upper respiratory illness. Histamine was detectable in nasopharyngeal secretions of patients with parainfluenza virus-related croup significantly more often than in patients with upper respiratory illness caused by parainfluenza virus. These observations suggest a role for immunologic mechanisms in the pathogenesis of severe forms of respiratory illness caused by parainfluenza virus infection.

Natural history of parainfluenza virus infection in childhood

In order to determine the natural history of parainfluenza virus infection in early life, we followed prospectively 130 infants and children from birth or a few months of age for evidence of infection with PV. Using rapid diagnostic techniques, standard tissue culture infectivity, and serologic techniques we were able to document primary PV infection in 92% of these infants, and repeated infection with heterotypic or homotypic PV strains in 49% by 30 months of age. Increasing patient age had no significant effect in reducing the incidence of lower respiratory tract illness as a result of PV infection. Infection with one PV serotype provided no protection against LRTI at the time of subsequent infection with a heterotypic PV strain. In contrast, primary PV infection provided a brief period of immunity to LRTI upon homotypic reinfection. Secretory IgA responses to PV were determined by immunofluorescent techniques. Antibody response to PV strains causing primary infection and heterotypic repeated infection were transient and of low magnitude. Homotypic reinfection resulted in significantly enhanced production of secretory antibody to PV. At least in early life, repeated exposures to PV appear to be essential for maintaining immunity to severe forms of illness caused by PV infection.

A comparison of paramyxoviruses by immunoprecipitation

Using the technique of immune precipitation of [35S]methionine-labelled infected cell polypeptides followed by SDS-polyacrylamide gel electrophoresis and autoradiography it has been shown that SV5 and a closely related isolate are both antigenically related to human parainfluenza virus type 2. Limited cross-reactions were also demonstrated between parainfluenza virus types 1 and 3 by this method and the apparent molecular weights of the major structural components of human parainfluenza virus types 2 and 3 have been deduced.

Detection of respiratory syncytial, parainfluenza type 2, and adenovirus antigens by radioimmunoassay and enzyme immunoassay on nasopharyngeal specimens from children with acute respiratory disease

Four-layer antispecies radioimmunoassay (RIA) and enzyme immunoassay (EIA) procedures were developed for the detection of respiratory syncytial virus (RSV), parainfluenza type 2 virus, and adenovirus antigens in nasopharyngeal specimens from children hospitalized for acute respiratory disease. Polystyrene beads (RIA) or flat-bottomed polystyrene microtiter plates (EIA) were used as the solid phases, guinea pig anti-virus immunoglobulins were used as the captive antibodies, rabbit anti-virus immunoglobulins were used as the secondary antibodies, and 125I-labeled sheep anti-rabbit (RIA) or horseradish peroxidase-labeled swine anti-rabbit (EIA) immunoglobulins were used as the indicator antibodies. A comparison of the EIAs and RIAs with routinely used immunofluorescence (IF) techniques was made with 164 nasopharyngeal specimens collected from children with acute respiratory disease. Only 3 of 66 RSV IF-positive specimens were negative in RSV RIA, and of 83 RSV, parainfluenza type 2 virus, and adenovirus IF-negative specimens, 1 was positive in RSV RIA. Of 4 parainfluenza type 2 virus IF-positive and 11 adenovirus IF-positive specimens, each was positive in corresponding RIAs, and all 83 IF-negative specimens were negative in parainfluenza type 2 virus and adenovirus RIAs. The results of the RSV, parainfluenza type 2, and adenovirus EIAs confirmed the results of corresponding RIAs in each selected case tested. The RIAs and EIAs were found to be as specific and sensitive as IF techniques, and more practical in the rapid detection of respiratory viruses in nasopharyngeal secretions.

Secretory immunological response in infants and children to parainfluenza virus types 1 and 2

The secretory immunological responses to natural infection with parainfluenza viruses ae not well defined. Nasopharyngeal secretion specimens from 20 infants and children naturally infected with parainfluenza virus type 1 or type 2 were examined for class-specific antibody and virus-neutralizing activity. There was a marked discordance in individual secretions between immunoglobulin A (IgA) antibody (as measured by indirect immunofluorescence) and neutralizing activity (as determined by either hemadsorption plaque or 50% tissue culture infective dose reduction) to the infecting parainfluenza virus type. Many secretions contained neutralizing activity in the absence of detectable IgA antibody; conversely, secretions with measureable IgA antibody frequently lacked neutralizing activity. Moreover, there was no relationship between neutralizing activity and the course of illness. All 11 patients with serial secretion specimens showed a fourfold or greater titer rise in IgA antibody to the homologous parainfluenza virus type. Antibody usually appeared 7 to 10 days after the onset of symptoms and peaked at about 2 weeks. This response did not appear to be related to age or to severity of illness. in general, the secretory responses resembled those seen in infants infected with respiratory syncytial virus.

Microneutralization test for influenza A and B and parainfluenza 1 and 2 viruses that uses continuous cell lines and fresh serum enhancement

A modified microneutralization test for influenza A and B and parainfluenza 1 and 2 viruses was developed. Use of continuous cell lines (Madin-Darby canine kidney and LLC-MK2), hemagglutination for virus detection, and transfer plates and other microtiter equipment resulted in a highly mechanized technique suitable for titrating large numbers of sera easily and relatively inexpensively. Titers of heat-inactivated human sera were enhanced 0.5 to 3.5 log2 by addition of fresh hamster or human serum to the test. Seroconversion rates and identification of seronegative persons were not changed by fresh serum enhancement, but the magnitude of seroconversion was often increased and the distribution of positive titers was broadened. For influenza A and B, seroconversion rates in the microneutralization test were equivalent to those obtained in rhesus monkey kidney tube neutralization tests. For influenza B, seroconversion rates by micro-neutralization were almost double those obtained with the hemagglutination inhibition test, but the rates were similar for influenza A/USSR (H1N1). Preexisting microneutralization titers correlated well with resistance of infection with influenza B. Limited experience with parainfluenza 1 and 2 was similar to previously reported findings with the tube neutralization test.

Studies on the pathogenicity of human-origin parainfluenza virus in the brain of mice

The pathogenicity of parainfluenza type 2 (croup-associated) virus known to cause infections of the respiratory tract in the early life of man was studied in the brain of mice. One- to 4-day-old sucklings and 4-week-old mice were inoculated intracerebrally with the virus. The virus multiplied in sucklings, but not in adults. Most mice inoculated intracerebrally with the virus appeared healthy. Histological examination showed minimum inflammatory changes, although moderate hydrocephalus developed in three of twenty-one sucklings by 6 weeks post-infection. Immunofluorescent study in sucklings showed viral antigens in ependymal lining cells and choroid plexus epithelium during the first two weeks, and parenchymal cells for more than two months. Virus specific antibody response was observed in adults, but not in sucklings. One interesting finding was that viral antigens persisted in six out of 11 suckling brains for one to two months.

Repertoire of antiviral antibodies expressed by somatic cell hybrids

Fusion between P3 x 63 Ag8 mouse myeloma cells and spleen cells from BALB/c mice immunized with influenza type A or B or parainfluenza type 1 virus generated reproducibly antiviral antibody-producing somatic cell hybrids (hybridomas). Eleven hybridomas derived from spleen cells of mice immunized with influenza type A virus were directed against the viral hemagglutinin, one reacted with a host component derived from chickens, and one expressed a specificity not further characterized. The hybridoma antibodies tended to be highly specific for the hemagglutinin of the immunizing virus and seemed to express the same repertoire of strain-specific antibody reactivities as splenic precursor B cells, they did not express any of the frequently occurring crossreactive anti-hemagglutinin specificities. Hybridomas producing crossreactive antibodies against hemagglutinin could be obtained if priming and boosting virus were heterologous.

Contamination of primary embryonic bovine kidney cell cultures with parainfluenza type 2 simian virus 5 and infectious bovine rhinotracheitis virus

Two different viruses were isolated from bovine embryonic cell cultures after two subcultures from the primary cells. One virus was identified as parainfluenza type 2 simian virus 5 (SV-5), and the other was identified as infectious bovine rhinotracheitis virus. Six months later, stock cultures of pig kidney (PK-15) cells were found to be contaminated with SV-5 virus. We believe that the source of the SV-5 virus in the bovine cells was a cross-contamination from monkey kidneys during preparation of the cell cultures. The infectious bovine rhinotracheitis contamination was probably of endogenous origin. The bovine embryonic cell cultures were the probable source of contamination of the PK-15 cells with SV-5 virus.