Animal models for emerging coronavirus: progress and new insights

The emergences of coronaviruses have caused a serious global public health problem because their infection in humans caused the severe acute respiratory disease and deaths. The outbreaks of lethal coronaviruses have taken place for three times within recent two decades (SARS-CoV in 2002, MERS-CoV in 2012 and SARS-CoV-2 in 2019). Much more serious than SARS-CoV in 2002, the current SARS-CoV-2 infection has been spreading to more than 213 countries, areas or territories and causing more than two million cases up to date (17 April 2020). Unfortunately, no vaccine and specific anti-coronavirus drugs are available at present time. Current clinical treatment at hand is inadequate to suppress viral replication and inflammation, and reverse organ failure. Intensive research efforts have focused on increasing our understanding of viral biology of SARS-CoV-2, improving antiviral therapy and vaccination strategies. The animal models are important for both the fundamental research and drug discovery of coronavirus. This review aims to summarize the animal models currently available for SARS-CoV and MERS-CoV, and their potential use for the study of SARS-CoV-2. We will discuss the benefits and caveats of these animal models and present critical findings that might guide the fundamental studies and urgent treatment of SARS-CoV-2-caused diseases.

Cross-reactive memory T cells and herd immunity to SARS-CoV-2

Immunity is a multifaceted phenomenon. For T cell-mediated memory responses to SARS-CoV-2, it is relevant to consider their impact both on COVID-19 disease severity and on viral spread in a population. Here, we reflect on the immunological and epidemiological aspects and implications of pre-existing cross-reactive immune memory to SARS-CoV-2, which largely originates from previous exposure to circulating common cold coronaviruses. We propose four immunological scenarios for the impact of cross-reactive CD4+ memory T cells on COVID-19 severity and viral transmission. For each scenario, we discuss its implications for the dynamics of herd immunity and on projections of the global impact of SARS-CoV-2 on the human population, and assess its plausibility. In sum, we argue that key potential impacts of cross-reactive T cell memory are already incorporated into epidemiological models based on data of transmission dynamics, particularly with regard to their implications for herd immunity. The implications of immunological processes on other aspects of SARS-CoV-2 epidemiology are worthy of future study.

Interferon lambda 4 signals via the IFNλ receptor to regulate antiviral activity against HCV and coronaviruses

The IFNL4 gene is a recently discovered type III interferon, which in a significant fraction of the human population harbours a frameshift mutation abolishing the IFNλ4 ORF. The expression of IFNλ4 is correlated with both poor spontaneous clearance of hepatitis C virus (HCV) and poor response to treatment with type I interferon. Here, we show that the IFNL4 gene encodes an active type III interferon, named IFNλ4, which signals through the IFNλR1 and IL-10R2 receptor chains. Recombinant IFNλ4 is antiviral against both HCV and coronaviruses at levels comparable to IFNλ3. However, the secretion of IFNλ4 is impaired compared to that of IFNλ3, and this impairment is not due to a weak signal peptide, which was previously believed. We found that IFNλ4 gets N-linked glycosylated and that this glycosylation is required for secretion. Nevertheless, this glycosylation is not required for activity. Together, these findings result in the paradox that IFNλ4 is strongly antiviral but a disadvantage during HCV infection.

Update: Severe respiratory illness associated with Middle East Respiratory Syndrome Coronavirus (MERS-CoV)--worldwide, 2012-2013

CDC continues to work in consultation with the World Health Organization (WHO) and other partners to better understand the public health risk posed by the Middle East Respiratory Syndrome Coronavirus (MERS-CoV), formerly known as novel coronavirus, which was first reported to cause human infection in September 2012. The continued reporting of new cases indicates that there is an ongoing risk for transmission to humans in the area of the Arabian Peninsula. New reports of cases outside the region raise concerns about importation to other geographic areas. Nosocomial outbreaks with transmission to health-care personnel highlight the importance of infection control procedures. Recent data suggest that mild respiratory illness might be part of the clinical spectrum of MERS-CoV infection, and presentations might not initially include respiratory symptoms. In addition, patients with comorbidities or immunosuppression might be at increased risk for infection, severe disease, or both. Importantly, the incubation period might be longer than previously estimated. Finally, lower respiratory tract specimens (e.g., sputum, bronchoalveolar lavage, bronchial wash, or tracheal aspirate) should be collected in addition to nasopharyngeal sampling for evaluation of patients under investigation. An Emergency Use Authorization (EUA) was recently issued by the Food and Drug Administration (FDA) to allow for expanded availability of diagnostic testing in the United States.

Public health investigations required for protecting the population against novel coronaviruses

ABSTRACT There have been many laboratory-based investigations since the emergence of the novel coronaviruses in the autumn of 2012, but most of the parameters required for establishing scientifically the control measures that will protect against them have yet to be determined. Equally, the global distribution of the viruses in their animal reservoir has yet to be established. The experience of investigating and controlling another novel coronavirus, SARS, in 2003 shows how national and local investigations can come together as an international coalition and successfully avert epidemics. A menu of studies that need to be undertaken, especially in the countries experiencing transmission, is presented here.

Retrospective evidence that the MHC (B haplotype) of chickens influences genetic resistance to attenuated infectious bronchitis vaccine strains in chickens

Infectious bronchitis is a respiratory disease of chickens that is caused by the coronavirus infectious bronchitis virus (IBV). Virtually all broiler and layer breeder flocks are routinely vaccinated against IBV. Two hatches of 1-day-old chicks from four lines were mistakenly vaccinated for infectious bronchitis using a moderately attenuated vaccine designed for chicks of an older age. The vaccination resulted in high mortality, and chicks from three of four lines died with signs typical of infectious bronchitis. The mortality that occurred using this less-attenuated vaccine was significantly influenced by the genetic line, and the MHC (B) haplotype in chickens of three B congenic lines. B congenic chickens possessing the B*15 haplotype were resistant in contrast to chickens possessing the B*13 or B*21 haplotypes. Chicks from two further hatches of the four lines were vaccinated appropriately with a more attenuated IBV vaccine, and only limited chick mortality was seen. These retrospective data from two repeated hatches confirm earlier data indicating chicken genes influence resistance to IBV, and indicate for the first time that genes tightly linked to the B haplotype are relevant in resistance to IBV. Due to extenuating circumstances it was not possible to verify results with chicks from F2 matings. Factors that may enhance definition of the role of the B haplotype in immune response to IBV, and the desirability for further analysis of a B haplotype-linked influence on immunity to IBV are discussed.

Expression of the synthetic neutralizing epitope gene of porcine epidemic diarrhea virus in tobacco plants without nicotine

Porcine epidemic diarrhea virus (PEDV) causes acute diarrhea and dehydration in pigs, leading to death with a high mortality. In this study, the synthetic neutralizing epitope gene of PEDV, which was optimized based on the coding sequence of tobacco plant genes being modified, was expressed in the no-nicotine tobacco plants. The synthetic gene was cloned into the plant expression vector under the control of CaMV 35S promoter and transformed by an Agrobacterium-mediated transformation. The amount of synthetic epitope protein of PEDV detected in the transgenic tobacco plants was approximately 2.1% of the total soluble plant protein, which was approximately five-fold higher than that expressed with the native gene.

The propagation of a porcine epidemic diarrhea virus in swine cell lines

A strain of porcine epidemic diarrhea virus (PEDV), P-5V, utilized as a live virus vaccine in Japan was infected to a swine cell lines, KSEK6 and IB-RS-2 cells. Clear CPE, characterized by cellular destruction, started to appear in the infected cells on 2-3 days post infection (DPI) and affected cells was completely degenerated on 4 DPI. The virus was serially passaged in the cells even without addition of trypsin. Small but clear plaques were formed under an agar overlay medium on the cells. The infective titer in the order of 10(7.00-7.50) TCID50 per ml was obtained at usual incubation temperature.

Infectious bronchitis serology in broilers and broiler breeders: correlations between antibody titers and performance in vaccinated flocks

In this study, a follow-up was made between 1993 and 1997 from broiler breeders at birth down to offspring broilers at processing, through vertically integrated registration of infectious bronchitis virus (IBV) antibody titers and performance data. All measurements were used two by two in a simple correlation study to calculate the degree to which they were linearly correlated. The antibody patterns in the broiler breeders indicated frequent field infections breaking through vaccinal immunity. Significant correlations measured between antibody titers and production parameters within and between the generations strongly suggested negative effects of IBV infections on laying percentage in the breeders and on mortality and daily weight gain in the broilers. Economic losses associated with IBV infections in the broilers occurred predominantly in flocks hatched with low and erratic maternal antibody titers. We concluded that IBV vaccination strategies should aim at high and uniform antibody titers in the broiler breeders.

Study of protection by recombinant fowl poxvirus expressing C-terminal nucleocapsid protein of infectious bronchitis virus against challenge

A stable recombinant fowl poxvirus (rFPV) expressing the C-terminal region (119 amino acids) of the nucleocapsid (N) protein of an infectious bronchitis virus (IBV) strain Ch3 was constructed by inserting the coding sequence within the thymidine kinase gene of fowl poxvirus (FPV) by homologous recombination. The N protein was expressed under control of the vaccinia virus promoter P7.5 in chicken embryo fibroblast cell cultures as seen in immunofluorescence assay and in rFPV-inoculated specific-pathogen-free (SPF) chickens by detecting antibodies with enzyme-linked immunosorbent assay (ELISA). A homologous IBV strain (Ch3) and two heterologous IBV strains (Ch5 and H4) were used to inoculate SPF chickens in a challenge to examine the protective efficacy of the rFPV. When the chickens were challenged with IBV Ch3 or Ch5, the control birds had respiratory signs of infections bronchitis, whereas all the vaccinated birds were clinically normal although low levels of the IBV infection were detected by a differential ELISA. In contrast, in the chickens challenged with IBV H4, all control birds and vaccinated birds suffered from the highly lethal IBV H4 infection. Our results suggest that the C-terminal 119 amino acid of the nucleocapsid expressed by FPV is a host-protective antigen and may induce cross-protective immunity against illness among some IBV strains.

An immunodominant CD4+ T cell site on the nucleocapsid protein of murine coronavirus contributes to protection against encephalomyelitis

The murine coronavirus neurotropic strain JHM (MHV-JHM) nucleocapsid (N) protein induces a strong T-helper cell response in Lewis rats. It has been shown previously that N-specific CD4+ T cells can confer protection against acute disease upon transfer to otherwise lethally infected rats. To define the major antigenic regions that elicit this T cell response, truncated fragments of N protein were expressed from a bacterial expression vector and employed as T cell antigens. Lymphocytes from either MHV-JHM-infected or immunized rats were stimulated in culture with virus antigen, grown and tested for their specificity to the N protein fragments. The carboxy-terminally located C4-N fragment (95 amino acids) induced the most pronounced proliferative response irrespective of whether the lymphocyte culture was derived from immunized or MHV-JHM-infected rats. We established T cell lines specific for the truncated N protein fragments and tested their potential to mediate protection by transfer experiments. Only the T cell line C4-N and the T cell line specific for the full-length N protein were protective. By contrast, all truncated N protein fragments elicited a humoral immune response and contained antigenic sites recognized by antibodies from diseased rats.

Characterisation of an infectious bronchitis virus isolated from vaccinated broiler breeder flocks

Four apparently serologically closely related isolates of infectious bronchitis virus were obtained from two flocks of vaccinated broiler breeders, one mile apart, which were experiencing increased mortality and decreases in egg production. The isolates were serologically distinct from isolates previously described and capable of causing characteristic infectious bronchitis-like respiratory infection in young chicks. In one experiment, the H120 vaccine strain of the virus did not protect the trachea against challenge with the new isolates 21 days later.

IgM responses in chicken serum to live and inactivated infectious bronchitis virus vaccines

Intramuscular (i.m.) administration of infectious bronchitis virus (IBV) oil-emulsion vaccine (OEV) to IBV-primed or unprimed chickens resulted in the production of zero or minimal concentrations of IBV-specific IgM in the serum, as measured by enzyme-linked immunosorbent assay of gel chromatography fractions. Live-attenuated infectious bronchitis (IB) vaccine given i.m. or by eyedrop stimulated the production of IBV-specific IgM in similar amounts following inoculation by both routes. These levels were comparable to those found in earlier studies following intranasal inoculation with a virulent strain of IBV and confirm that the detection of IBV-specific IgM is a valuable aid to the diagnosis of recent infection. As expected, administration of live-attenuated IB vaccines i.m. or by eyedrop protected the respiratory tract against challenge with virulent virus 24 days later; however, OEV given i.m. did not.

Light intensity-associated eye lesions of Fischer 344 rats in long-term studies

Albino rats and mice are sensitive to light and the recommended illumination of animal rooms (75-125 ft-candles) is known to cause retinal damage. When a room is illuminated by ceiling lights, animals in the cages of the top row and, to some extent, in the side columns of cage racks will be exposed to higher light intensity than those in the other cages of the rack. In 2-yr chemical carcinogenicity studies of the National Toxicology Program (previously the Carcinogenicity Bioassay Program of the National Cancer Institute), Fischer 344 rats were group-housed in hanging drawer-type clear polycarbonate cages. During the course of the chronic studies, a number of rats developed opacity of the eye. Ocular examination indicated chronic uveitis, deep interstitial keratitis, cataract formation leading to panophthalmitis, and in severe cases, phthisis bulbi. Histologic examination showed cataract and retinal degeneration. Incidences of these lesions were highest (greater than 55%) in the rats of the top rows and lowest in those of the bottom rows (less than 10%) of cages with no relation to chemical treatment, indicating an association with light intensity. The incidence of these eye lesions was markedly decreased (less than 15%) by decreasing the light intensity of the animal room to less than 50 ft-candles at 5 ft from the floor and rotating the cages in each column of a rack from top to bottom when cages or racks were changed.

Coronavirus infection in the laboratory rat: immunization trials using attenuated virus replicated in L-2 cells

Sixty-nine specific pathogen-free male Wistar rats approximately eight weeks of age were used to evaluate the efficacy of an attentuated strain of sialodacryoadenitis (SDA) virus in providing protection against infection on subsequent challenge with virulent SDA virus. Fifty-four animals were inoculated intranasally with approximately 10(3.5) median cell culture infectious doses of the 25th passage of SDA virus in L-2 cells. Randomly-selected vaccinated animals were killed in order to evaluate the safety and efficacy of attenuated virus by histopathological examination of the salivary glands, lacrimal glands, and lower respiratory tract, and titration of sera for antibody to SDA virus. At three months and six months postvaccination (pv), animals were selected at random and challenged with virulent SDA virus. Seronegative, age-matched animals were also challenged, and served as controls. In animals examined at six to ten days pv, lesions were absent in submandibular and parotid salivary glands and lacrimal glands, but transient lesions were present in major airways of the lower respiratory tract. In a comparison of the incidence and extent of lesions, and antibody titers in challenged vaccinates and seronegative controls, lesions were minimal or absent in vaccinates compared to challenged naive rats, particularly in animals inoculated at three months pv. In addition, antibody titers in challenged vaccinates were much higher than were postinoculation titers in inoculated controls. In a comparison of lesions in salivary and lacrimal glands in vaccinated and control animals challenged at six months pv, there was a significant reduction in the number of animals without lesions in the vaccinated group (p = less than 0.0001).(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of interferon or Propionibacterium acnes on the course of experimentally induced feline infectious peritonitis in specific-pathogen-free and random-source cats

Seventy-four cats (52 treated and 22 untreated) were evaluated in efficacy studies of interferon (IFN), Propionibacterium acnes, or a combination of these drugs against experimentally induced feline infectious peritonitis (FIP). Cats were given doses of recombinant human leukocyte (alpha) IFN (rHuIFN-alpha), feline fibroblastic (beta) IFN (FIFN-beta) or P acnes at regular intervals before and after inoculation of virulent FIP virus (FIPV). Prophylactic and therapeutic administration of high doses (10(6) U/kg of body weight) or moderate doses (10(4) U/kg) of rHuIFN-alpha, FIFN-beta (10(3) u/kg), or P acnes (0.4 or 4 mg) did not significantly reduce mortality in treated vs untreated cats. However, the mean survival time in cats treated with 10(6) U of rHuIFN-alpha-/kg alone or combined with doses of P acnes was significantly (P = 0.03) increased after inoculation of highly lethal amounts (200 LD100) of FIPV vs survival time in untreated cats. Although P acnes alone was ineffective, there was some indication that a combination of P acnes and high doses of rHuIFN-alpha was more effective than rHuIFN-alpha alone. Seemingly, the efficacy of rHuIFn-alpha treatment was improved in cats challenge-exposed with less FIPV; in 1 trial, 4 of 5 cats (80%) treated with high doses of rHuIFN-alpha survived after inoculation of minimal lethal amounts (0.6 LD100) of FIPV, whereas only 2 of 5 untreated cats (40%) survived. Pretreatment of cats with 10(6) U of rHuIFN-alpha/kg resulted in detectable serum IFN activity 24 hours later; serum IFN activity was not detected in cats pretreated with P acnes, FIFN-beta, or 10(4) U of rHuIFn-alpha/kg.(ABSTRACT TRUNCATED AT 250 WORDS)

Characterization of an attenuated temperature sensitive feline infectious peritonitis vaccine virus

Intranasal administration of a ts-FIPV vaccine protected cats against two rigorous challenges of immunity. Investigations showed that ts-FIP viral RNA synthesis was normal at 39 degrees C and structural proteins were synthesized, but not expressed at the cell surface. Lack of surface expression combined with decreased virus titer indicate that, although structural viral proteins were initially synthesized, they were not packaged into intact virions at the nonpermissive temperature. The ts-FIP vaccine virus was shown to replicate exclusively in the upper respiratory tract, where lower temperatures allow maturation of the virus. Viral proteins expressed on cells in the upper respiratory tract probably stimulate the development of local IgA and CMI responses and a systemic CMI response which in turn may stop the dissemination of virulent FIPV if it crosses the mucosal barrier. Investigations are ongoing to study the protective mechanism of ts-FIPV induced immunity.

Immunogenicity of recombinant feline infectious peritonitis virus spike protein in mice and kittens

The gene encoding the fusogenic spike protein of the coronavirus causing feline infectious peritonitis (FIPV) was recombined into the genome of vaccinia virus, strain WR. The recombinant induced spike protein specific, in vitro neutralizing antibodies in mice. When kittens were immunized with the recombinant, low titers of neutralizing antibodies were obtained. After challenge with FIPV, these animals succumbed earlier than the vWR-immunized control group ("early death syndrome").

Protection from lethal coronavirus infection by affinity-purified spike glycoprotein of murine hepatitis virus, strain A59

Murine hepatitis viruses provide excellent animal models for the study of virus-induced diseases of the central nervous system and gastrointestinal tract. Several studies have indirectly provided evidence that the spike glycoprotein (S) of these coronaviruses bears determinants for pathogenesis and the induction of protective immunity. In order to directly evaluate the immunogenicity of this protein, it was purified by affinity chromatography with an in vitro neutralizing and in vivo protective monoclonal antibody which immunoprecipitated the 180-kDa spike glycoprotein of the neurotropic A59 strain of murine hepatitis virus (MHV-A59). Mice immunized twice with approximately 1 micrograms of purified S in Freund's adjuvant developed high titers of neutralizing and fusion inhibiting antibodies, even though the protein was at least partially denaturated after elution from the affinity column. Moreover, these mice were protected from lethal encephalitis when challenged intracerebrally with 10 LD50 of MHV-A59. This study provides a direct demonstration of the importance of the coronavirus spike glycoprotein in the induction of a protective immune response.

Avian infectious bronchitis: cross-protection studies using different Australian subtypes

The cross-immunity of vaccinated chickens after challenge with some Australian infectious bronchitis viruses was assessed by humoral antibody responses and by ciliary activity in tracheal rings of vaccinated chickens following challenge. Four viruses were used for vaccination: Vac 3, Vac 4, both current infectious bronchitis vaccine viruses, and Q1/76 and N2/62. IBV N1/62 (synonym T0 and infectious bronchitis virus N9/74 (synonym Appin) were used to challenge the vaccinated chickens. Results showed a lack of correlation between humoral antibody levels and protection. Cross-immunity was found after vaccination with each subtype, but was lower for Vac 3 and Vac 4 than for Q1/76 and N2/62.

Attempted immunisation of cats against feline infectious peritonitis using canine coronavirus

Specific pathogen free kittens were vaccinated with an unattenuated field isolate of canine coronavirus (CCV) either by aerosol or subcutaneously, and received boosting vaccinations four weeks later. Aerosolisation elicited a homologous virus-neutralising (VN) antibody response that increased steadily over a four-week period and levelled off one to two weeks after revaccination. The initial aerosolised dose produced an asymptomatic infection with excretion of CCV from the oropharynx up to eight days after vaccination; virus shedding was not detected, however, after the second inoculation. Cats vaccinated subcutaneously developed low VN antibody titres after the first CCV dose and experienced a strong anamnestic response after the second dose. Neutralising antibody titres then levelled off one to two weeks after revaccination at mean values somewhat lower than in cats vaccinated by aerosol. CCV was not isolated from the oropharynx after either subcutaneous dose. Four weeks after CCV boosting inoculations, vaccinated cats and sham-vaccinated control cats were divided into three subgroups and challenged by aerosol with the virulent UCD1 strain of feline infectious peritonitis virus (FIPV UCD1) at three different dosage levels. Five of six cats (including sham-vaccinated controls) given the lowest challenge dose showed no signs of disease, while all other cats developed lesions typical of feline infectious peritonitis (FIP). The five surviving cats developed FIP after subsequent challenge with a fivefold higher dose of FIPV. Thus heterotypic vaccination of cats with CCV did not provide effective protection against FIPV challenge.

[Objective evaluation of the immunogenic effectiveness of polyvalent vaccines against enteral infections of newborn calves under enzootic conditions]

For evaluating the protective effect of polyvalent vaccine against diarrhoea in new born calves caused by rotaviruses, coronaviruses and enterotoxigenic E. coli the method was selected of mathematical and statistical analysis of the set of data characterizing the most important clinical symptoms of the disease during the first three weeks after birth. In two large-scale breeds with a mass occurrence of diarrhoea of the known etiology the state of health of calves before the vaccine application was compared with the state of health of calves born in the period after the vaccination. The following traits were selected for evaluating the severity of the disease: the age of calf at the beginning of the disease, character and intensity of diarrhoea, length of disease and results of treatment. In all the selected indicators, statistically significant differences were determined pointing to the fact that the vaccine used for increasing the immunity against enteropathogenic viruses and bacteria, applied in high pregnant cows and heifers before parturition, protected the sucking calves and calves fed the milk of their mothers against the disease in the first week after birth. The diarrhoea, occurring in the calves of the vaccinated cows and heifers mostly during the second week of age was easy to treat therapeutically and ended in most cases after a short period of a tea diet. After the vaccination, the death loss in both localities decreased more than eight times.

Monoclonal antibodies to the matrix (E1) glycoprotein of mouse hepatitis virus protect mice from encephalitis

Monoclonal antibodies to the matrix or E1 glycoprotein of mouse hepatitis virus (MHV) were tested for their ability to protect mice from a normally lethal challenge of MHV-4. Four antibodies were tested, and two of these, J.1.3 and J.3.9, were protective. Protection did not correlate with virus neutralization in vitro, antibody isotype, recognition of a unique E1 antigenic site, or dependence on complement in vivo. Survival from acute encephalitis was followed by subacute demyelination, as has been shown with protection mediated by neutralizing monoclonal antibodies against the major glycoprotein, E2. These results demonstrate that antibodies which are specific for a viral matrix protein are able to alter the course of disease.

Efficacy of infectious bronchitis virus vaccines against heterologous challenge

Twenty-four-week-old white Leghorn layers were inoculated subcutaneously with a killed Newcastle disease-infectious bronchitis (Massachusetts type) virus (MIBV) vaccine. Twenty-eight weeks after vaccination, the birds were challenged intraocularly with the Arkansas strain of infectious bronchitis virus (AIBV) to determine the effects of heterologous virus exposure on egg production, egg quality and serum antibody response of the birds. The challenged hens laid significantly (P less than 0.005) fewer eggs than the unchallenged layers. Eggs laid by the unchallenged groups weighed significantly more (P less than 0.005) than those laid by the challenged groups. Further, the internal quality (Haugh units) and shell quality of eggs laid by the AIBV-challenged hens was significantly (P less than 0.005) inferior to those from the unchallenged hens. In addition, the AIBV-challenged hens laid more soft-shell, misshapen and small eggs than the unchallenged hens. The Arkansas serum haemagglutination inhibition (AIBV-HI) titres of AIBV challenged birds increased up to four weeks after challenge. The corresponding MIBV haemagglutination-inhibition (MIBV-HI) titres decreased during the same period. The study indicates that killed MIBV vaccine offered no protection to birds exposed to heterologous AIBV.

Humoral immune response of the bovine fetus to in utero vaccination with attenuated bovine coronavirus

A fetal response to in utero vaccination with attenuated bovine coronavirus (9 to 49 days before parturition) was determined in 8 calves, 5 vaccinated and 3 controls. Calves were derived by hysterotomy before parturition and were maintained in a closed gnotobiotic environment. The IgA, IgM, and IgG values and coronavirus-neutralizing antibody titers were higher in the sera and intestinal loop fluid from vaccinated calves than in those from control calves. Sections of ileum and ileal lymph nodes from 1-day-old vaccinated calves, when stained with monospecific anti-bovine IgG, IgM, and IgA had numerous positively stained plasma cells. Positive fluorescence was not detected in comparable tissues from controls. When the 8 calves were given virulent coronavirus orally at 6 days of age, vaccinated calves did not become ill, whereas control calves had diarrhea in 19 to 22 hours. All calves were killed at 10 days of age. Control calves had lesions characteristic of coronavirus infection, and intestinal epithelial cells were positive by fluorescent antibody tests. In vaccinated calves, lesions of coronavirus infection were absent, and results of fluorescent antibody tests were negative. Although in utero vaccination with a coronavirus vaccine stimulated immunity in the newborn calf, the frequency of abortions (2 of 14 cows inoculated intra-amniotically) and premature births (4 of 14) precluded practical application.

A study of breeder vaccination programs and problems in the broiler progeny in Saskatchewan utilizing enzyme-linked immunosorbent assay

A survey of antibodies against infectious bursal disease virus (IBDV), infectious bronchitis virus (IBV), Newcastle disease virus (NDV), and reovirus (RV) was conducted in broiler-breeder flocks and selected progeny broiler flocks utilizing the enzyme-linked immunosorbent assay. Marked differences in antibody titers between different breeder flocks were related to differences in vaccination programs. Poor performance in some progeny broiler flocks was related to low antibody titers against IBDV in the source breeder flocks. Progeny broiler flocks in which there was a high incidence of condemnations for airsacculitis had elevated antibody titers against IBV. A few progeny broiler flocks that experienced high mortality due to gangrenous dermatitis had no antibody titers against IBDV at processing. Antibody titers against RV were very variable and could not be related to any production problems.

Effects of avian infectious bronchitis virus (Arkansas strain) on vaccinated laying chickens

Twenty-four-week-old white leghorn layers were inoculated subcutaneously with a killed Newcastle-infectious bronchitis (Massachusetts type) virus (MIBV) vaccine. The birds were challenged 194 days later intraocularly with Arkansas strain of infectious bronchitis virus (AIBV). The challenged hens laid significantly (P less than 0.005) fewer eggs than the unchallenged layers, and the eggs laid by the challenged groups weighed significantly less (P less than 0.001) than those laid by the unchallenged groups. Further, the internal quality (Haugh units) and shell quality of eggs laid by the challenged hens were significantly (P less than 0.005) inferior to the quality of eggs from unchallenged hens, and the challenged hens laid more soft-shelled, misshapen, and small-sized eggs than the unchallenged hens. The Arkansas serum hemagglutination-inhibition (AIBV-HI) titers of challenged birds increased continuously through 29 days post-challenge. The MIBV hemagglutination-inhibition (MIBV-HI) titers of killed-MIBV-vaccinated birds decreased during the same period. The study indicates that killed MIBV vaccine offered no protection to birds exposed to AIBV. The same vaccine was quite effective against a homologous (MIBV) virus challenge.

[A new polyvalent vaccine against enteral infections in newborn calves]

The most frequent microbial causative agents of massive diarrheas in new-born calves kept on large cattle farms in the CSSR are rotaviruses, coronaviruses and enterotoxigenic strains of E. coli, manifesting themselves as complicated virus-bacterial infections. An inactivated polyvalent adjuvant vaccine has been developed for the prevention and specific prophylaxis of these enteral infections; the vaccine contains bovine rotavirus, bovine coronavirus and three enterotoxigenic serotypes of E. coli with protective antigen K 99. The rotavirus and coronavirus are propagated on the stable cellular line MDBK and inactivated with 0.2% formalin, the Escherichia strains are submersed in the MINCA culture medium during their cultivation and inactivated with 0.5% formalin. The vaccine was prepared as a blend of the same amounts of rotavirus and coronavirus and of such an amount of bacterin so that 1 ml of the vaccine will contain 10(9) bacteria. One part of oil adjuvant was added to five parts of the virus-bacterial blend and the blend was homogenized in the Ultraturax apparatus. The vaccine is to be used for immunization of pregnant cows and heifers; in these animals it induces the production of specific antibodies to all antigens contained in the vaccine. Its immunogenic effects were checked in 32 calves and 38 cows in the herds with the occurrence of diarrheas caused by both enteropathogenic viruses and enterotoxigenic escherichia. It was demonstrated that the inactivation did not influence in either of the viruses the process of inducing the production of specific antibodies, and the antibody response of the calves and heifers after application of 2 ml of complete inactivated vaccine was equally strong as after application of live vaccine containing only rotavirus and coronavirus. The level of the rotavirus antibodies increased on the average 30 times and 200 times, coronavirus antibodies twice and four times. The antibody response to coronavirus was negatively influenced by the relatively high levels of antibodies before vaccination. The antibody response to antigen K 99 was expressive in all cases.

Immunization against feline coronaviruses

Feline infectious peritonitis (FIP) is caused by one of several strains of feline coronaviruses which are grouped into 2 general types of viruses. Infection of cats with FIP virus results in production of serum antibodies which may be protective in conjunction with cell mediated immunity, may provided no protection at all, or may produce an immune enhancement to subsequent exposure to another FIP virus or a recrudescence of the original infecting virus. Attempts at immunization of cats against FIP with inactivated or live FIP viruses have been generally unsuccessful, and often sensitizing the cat through immune enhancement rather than providing protection. Heterologous live virus vaccines using viruses of the same antigenic cluster (transmissible gastroenteritis of swine, canine coronavirus, and human coronavirus 229E) have failed to provide protection against FIP virus. Further research into the exact mechanism of protection and immune enhancement is needed in order to understand ways of producing an effective and safe vaccine.

Maternal antibody-modulated MHV-JHM infection in C57BL/6 and BALB/c mice

1. Maternal antibody protected C57BL/6 and BALB/c suckling mice from the acute, fatal encephalomyelitis caused by MHV-JHM. 2. 40% of the C57BL/6 mice and 25% of the BALB/c mice which were protected by maternal antibody developed neurological disease days to weeks later. Although the clinical syndromes developed by the two different strains were different, in both cases the mice developed a demyelinating encephalomyelitis with fewer inflammatory changes present in the grey matter. 3. Presence or absence of neutralizing antibody in the sera of maternal antibody-protected C57BL/6 mice did not correlate with the development of clinically evident neurological disease. 4. Infectious virus could only be isolated from C57BL/6 mice with neurological disease, although viral antigen could be detected in most mice whether symptomatic or not. 5. This model should be useful for the study of the viral and immune factors important in MHV-induced viral demyelination.

Relatedness of rabbit coronavirus to other coronaviruses

Rabbit coronavirus (RbCV) was apparently first encountered in 1961 when Scandinavian investigators observed occasional mortality in rabbits used to propagate the Nichols strain of Treponema pallidum. Mortality rates reached 50 percent by 1968 and 75 percent by 1970. Contaminated samples of T. pallidum were brought to the Johns Hopkins University School of Medicine, a World Health Organization center for the study of treponematoses. There it was established that the causative agent was filterable, the heart was the target organ, and the agent was determined by electron microscopy to be a coronavirus. Also, complement fixing antibodies to the human coronaviruses 229E (two way cross) and 0C43 (one way cross) were demonstrated in surviving rabbits. Immunofluorescent staining with anti-229E serum localized fluorescence in the interstitial tissue of the myocardium. Antiserum to RbCV cross reacted with coronaviruses of three other diseases, feline infectious peritonitis (FIPV), canine coronavirus diarrhea (CCV), and transmissible gastroenteritis (TGEV) by radioimmunoassay. In plaque neutralization tests, a slight reduction was observed against TGE and CCV but not against FIP. Antiserum to 229EV, CCV, FIPV and to a lesser degree TGEV partially blocked the clinical course of the disease and reduced mortality. Slight protection was afforded rabbits by vaccination with, in descending order of survivors, CCV, FIPV, and TGEV. Vaccination with calf diarrhea coronavirus (CDCV) provided no protection.

Comparison of the nephropathogenicity of four strains of infectious bronchitis virus

Experiments were conducted to characterize renal lesions in chickens induced by four strains of infectious bronchitis virus (IBV); each has been described as nephropathogenic. Those strains were also compared in vaccinated and unvaccinated older chickens for nephropathogenicity. The younger birds were much more susceptible to the nephritogenic effects of the strains. All four strains produced acute renal changes consisting of tubular damage and interstitial inflammatory cell infiltration and edema. Although both cortex and medulla were involved, the latter was generally affected more severely. The Holte strain proved to be the least pathogenic, followed by the more pathogenic Gray and Italian strains and finally by the Australian strain. All four strains produced similar chronic renal changes in unvaccinated birds, with no correlation to the severity of lesions seen at the acute phase. Chronic active and inactive types of interstitial nephritis were seen at the chronic phase. Vaccinated birds challenged with the Australian strain had the highest prevalence of the chronic active type of interstitial nephritis. The implication of renal viral persistence in the development of chronic active interstitial nephritis is discussed.

Serological profiles of commercial broiler breeders and their progeny. 1. Infectious bronchitis virus

Serum samples were collected from broiler breeders and their 1-day-old, 2-week-old, and 5-week-old progeny from different regions of the United States. Individual samples were tested by hemagglutination-inhibition (HI) against six infectious bronchitis virus (IBV) strains: Massachusetts 41 (Mass), H52, Connecticut 46 (Conn), Arkansas 99, SE17, and JMK. The use of multiple strains to test broiler flocks resulted in the detection of seroconversions to Conn and JMK vaccination that were not detected with the IBV Mass HI test. Further, HI titers were detected to IBV strains not used for flock vaccination. In some cases, those titers could be due to cross reactions to antigens common to each of the virus strains. In two breeder flocks, the highest HI titers were to heterologous strains.

Prevention of experimental coronavirus colds with intranasal alpha-2b interferon

Fifty-five volunteers treated with either intranasal recombinant interferon (rIFN; 2 X 10(6) IU/day) or placebo for 15 days were exposed to coronavirus by direct intranasal inoculation on the eighth day of treatment. Symptom scores were recorded, and cultures of virus were taken daily for all volunteers for seven days after inoculation. Nineteen (73%) of the 26 placebo recipients met symptom-score criteria for a cold, compared with 12 (41%) of the IFN recipients (P = .02). The mean nasal symptom scores in the placebo and IFN groups were 9.2 and 5.4, respectively (P = .03), and the mean total symptom scores in the two groups were 23.2 and 9.4, respectively (P = .003). The mean number of days with a total symptom score greater than 4 was 1.6 in the placebo recipients and 0.5 in the rIFN recipients (P = .02). Prophylactic intranasal rIFN effectively shortened the duration and reduced the severity of coronavirus cold symptoms.

Infectious bronchitis immunity: its study in chickens experimentally infected with mixtures of infectious bronchitis virus and Escherichia coli

The live infectious bronchitis (IB) vaccine, H120, protected chickens against intranasal challenge with a mixture of Escherichia coli strains (E. coli Pool) and IB virus (IBV) strains of the same (Massachusetts) serotype as H120; it usually also protected against challenge with the E. coli Pool and IBV strains of other serological types. When these challenge strains were themselves used as vaccines they usually protected against challenge with a mixture of the E. coli Pool and an IBV strain of the Massachusetts serotype (VF69-149) or an IBV strain not of the Massachusetts serotype (HVI-116). Poor protection, when observed, was most common in those experiments involving a minority of the IBV strains that had been incriminated in recent outbreaks of disease in vaccinated flocks of chickens. Much lower concentrations of IBV strain VF69-149 and E. coli O18 were found in the nose, trachea and spleen of H120-vaccinated chickens killed at different times after they were given a mixture of these organisms than were found in these sites in similarly challenged unvaccinated chickens. Some protection against challenge with IBV and the E. coli Pool was also observed in chickens vaccinated with an inactivated IBV strain; it was much less effective than that obtained following vaccination with the corresponding live IBV strain.

Coronavirus IBV: virus retaining spike glycopolypeptide S2 but not S1 is unable to induce virus-neutralizing or haemagglutination-inhibiting antibody, or induce chicken tracheal protection

Avian infectious bronchitis coronavirus (IBV) inactivated by beta-propiolactone induced partial protection of the trachea in up to 40% of chickens following one intramuscular inoculation 4 to 6 weeks prior to challenge. Retention of an intact tracheal ciliated epithelium 4 days after challenge was the criterion of protection. There was no correlation between protection and serum titres of virus-neutralizing (VN) and haemagglutination-inhibiting (HI) antibody, which were maximal at about 4 weeks after inoculation. Virus from which the S1 but not the S2 (spike-anchoring) spike glycopolypeptide had been removed by urea did not induce protection or VN or HI antibody. Four intramuscular inoculations of monomeric S1 induced VN and HI antibody in two and four chickens respectively. These results indicate that VN and HI antibodies are induced primarily by S1, that intact spikes are a major requirement for the induction of protective immunity and that this property is probably associated with S1.