Postchallenge Day Research Articles

Contribution of antibody-secreting cells induced in mucosal lymphoid tissues of pigs inoculated with respiratory or enteric strains of coronavirus to immunity against enteric coronavirus challenge.

Two antigenically related porcine coronaviruses, transmissible gastroenteritis virus (TGEV) which infects primarily the intestinal tract and causes severe diarrhea, and porcine respiratory coronavirus (PRCV) which infects the respiratory tract and causes subclinical or mild respiratory infections, presented a unique opportunity to study the interrelationship of gut-(GALT) and bronchus-associated lymphoid tissues (BALT) and their contribution to protective immunity against TGEV infection. Pigs were inoculated oral-nasally with TGEV or with PRCV at eleven days of age and challenged 24 days later with TGEV. All pigs initially given TGEV developed diarrhea and were completely protected against disease upon challenge. In contrast, pigs given PRCV had no clinical disease and shed virus in nasal secretions only; after challenge, 5 of 12 pigs developed diarrhea. Virus-specific IgG and IgA Ab-secreting cells (ASC) were enumerated by ELISPOT in the mesenteric and bronchial lymph nodes, spleens, and gut lamina propria at challenge and various post challenge days. Before challenge, in pigs exposed to TGEV, IgA-ASC in the duodenum and jejunum constituted the major ASC response. Conversely, PRCV-exposed pigs had mainly IgG-ASC in bronchial lymph nodes, with low ASC responses in the gut. After challenge, numbers of IgG-ASC increased rapidly in the gut lamina propria and mesenteric lymph nodes of only PRCV-primed pigs. Our results suggest that virus-specific IgG-ASC precursors derived in BALT of PRCV-primed pigs may migrate to the gut in response to TGEV challenge and contribute to the partial protection observed. The presence of IgA-ASC in the gut lamina propria of TGEV-primed pigs at the time of challenge correlated with complete protection against TGEV challenge. Thus a dichotomy exists in the BALT and GALT ASC responses; immunization via BALT induced a systemic type of response (IgG-ASC) and provided imperfect protection against an enteric pathogen, whereas immunization via GALT induced IgA-ASC and provided complete protection.

Vaccination of newborn pigs in the presence of low levels of pseudorabies colostral antibodies.

To test the hypothesis that newborn pigs with pseudorabies virus (PRV) colostral antibodies might be actively immunized with a PRV glycoprotein gIII-deleted vaccine (Omnimark-PRV), 23 piglets were obtained from four sows that had been immunized 4 weeks and 2 weeks before farrowing with this vaccine. Thirteen piglets were immunized with Omnimark-PRV when they were less than 3 days old and ten piglets served as non-vaccinated controls. Piglets were weaned at 28 days of age and challenged with virulent PRV (Shope) when they were 49 days old, at which time the vaccinated and control pigs were seronegative for PRV virus neutralizing (VN) and gIII antibodies, and all control pigs and ten vaccinees were seronegative for PRV antibodies by the latex agglutination test (LAT). Two vaccinees were LAT(+) and one was LAT(+/-). Central nervous system signs and/or respiratory disease signs were observed in six of ten control pigs with the death of one control, while two of 13 vaccinees showed only very mild and transient clinical disease signs and there were no fatalities. Non-vaccinees lost weight until postchallenge day (PCD) 6 and did not regain prechallenge weight until PCD 8. All vaccinees gained weight after challenge and at PCD 11 had mean weight gains nearly twice that of the controls. On PCD 11, the geometric mean titre for VN antibodies of non-vaccinees was 9.3, while that of vaccinees was 49.0, indicating that the vaccinated group had been immunologically primed.

Circumvention of maternal antibody interference by immunization of newborn pigs with glycoprotein gIII-deleted marker vaccine.

Maternal antibodies interfere with the immunization of swine by modified live-virus pseudorabies virus (PRV) vaccines. To test the hypothesis that a PRV vaccine attenuated by deletions in the thymidine kinase (TK) and gIII genes might reduce interference by maternal antibodies, pigs with moderate to low levels of colostral PRV antibodies were immunized with the TK- gIII-OMNIMARK-PRV vaccine. Vaccinates and non-vaccinates were challenged intranasally with virulent PRV at 7 weeks of age. In support of the hypothesis, it was found that central nervous system (CNS) and/or respiratory disease developed in six out of 10 controls with a fatal outcome in one, while two out of 13 vaccinates showed only very mild and transient CNS or respiratory disease signs with no fatalities. All vaccinates gained weight while non-vaccinates initally lost weight. At post-challenge day (PCD) 11, vaccinates showed 4.5 lb/pig greater weight gain than non-vaccinates. Virus neutralization (VN) analyses before and after challenge showed that vaccinates had been primed immunologically. In another experiment, newborn pigs from a pseudorabies disease-quarantined herd with high VN antibody titres were vaccinated, respectively, with the gIII-TK-OMNIMARK-PRV vaccine, a TK-gI-gX-vaccine, or no vaccine and challenged with virulent PRV at 14 weeks of age when VN titres were < 1:2. By PCD 9, the TK-gIII-group had outgained the TK-gI-gX- and the control groups, respectively, by 6.0 and 3.2 lb per pig.

Relationship between onset of puberty and establishment of persistent infection with equine arteritis virus in the experimentally infected colt

The relationship between stage of reproductive tract maturity and susceptibility to the experimental establishment of persistent infection with equine arteritis virus, (EAV) was investigated in 21 prepubertal and 15 peripubertal colts. Five of six prepubertal colts inoculated intranasally remained infected in the reproductive tract from post-challenge day 28 to 93 and two of six from post-challenge day 120 to 180. No virus was detected in five of these animals killed on post-challenge day 210. Each of two peripubertal colts remained infected in the reproductive tract at post-challenge day 60 and one of nine was found to be persistently infected with EAV 15 months after challenge. These findings confirm that the virus can replicate in the reproductive tract of a significant proportion of colts for a variable period of time after clinical recovery in the absence of circulating concentrations of testosterone equivalent to those found in sexually mature stallions. Long-term persistent infection with EAV does not appear to occur in colts exposed to the virus before the onset of peripubertal development. We suggest that colts should be vaccinated at approximately 6 months of age, before peripubertal development but after the disappearance of maternally acquired antibodies.

Allergic Contact Dermatitis Releases Soluble Factors That Stimulate Melanogenesis Through Activation of Protein Kinase C-Related Signal Transduction Pathway

Phenylazo-naphthol (PAN) allergy induces visibly well-defined and late-appearing hyperpigmentation of brownish yellow guinea pig skin in clear contrast to dinitrochlorobenzene (DNCB) allergy, which has very low incidence of hyperpigmentation. Skin extract from PAN allergy at 20-29 d post-challenge exhibited marked melanogenic stimulatory effects (3H2O release and 14C-thiouracil incorporation) when added to cultured guinea pig melanocytes. The time course in the appearance of melanogenic factor was definitely consistent with the induction pattern of visible pigmentation. By contrast, the addition of DNCB-challenged skin extract demonstrated no significant stimulating effect on melanogenesis in either assay system on any of the post-challenge days tested. Assay of intracellular inositol 1,4,5-trisphosphate formed through incubation with the melanocytes demonstrated that the PAN-allergy skin extract at day 28, which contains definite melanogenic factors, stimulated the formation of inositol 1,4,5-trisphosphate that occurs around 50 seconds in contrast to no or little increase with extracts obtained at days 0 and 1 post-challenge. Gel chromatographic analysis revealed that the PAN-allergy skin extract at day 28 contained a newly generated melanogenic fraction with a molecular weight of approximately 9000 Da which was also capable of stimulating DNA synthesis and activating the signal-transduction process (inositol trisphosphate formation) when added to guinea pig melanocytes. Both stimulations of melanogenesis and DNA synthesis by the 9000 Da fraction were completely abolished by the prior and simultaneous addition of protein kinase C (PKC) inhibitor (H-7) or its down-regulatory agent, phorbol 12,13-dibutyrate (PdBu). Taken together, these results suggest that PAN allergy provides a new mechanism of hypermelanization in which endogenous factors synthesized within skin induce the activation of signal-transduction pathways such as phosphoinositide turnover through ligands-receptor binding, resulting in the stimulation of melanocytes possibly through the activation of PKC.

Comparison of Therapeutic Versus Subtherapeutic Levels of Chlortetracycline in the Diet for Selection of Resistant Salmonella in Experimentally Challenged Chickens

Sixteen broiler chicks per group were fed chlortetracycline1 (CTC) at 0 (control) and 55, 110, and 220 ppm (subtherapeutic levels) continuously for 44 days or 550 ppm (therapeutic level) for three 5-day periods from 1 to 19 days of age. All birds were challenged at 4 days of age with a 10:1 mixture of CTC-sensitive and resistant (CTCr) Salmonella typhimurium. Chicks were sampled periodically through postchallenge day (PCD) 41, half in each pen by cloacal swabbing and the remainder by collection of droppings. Escherichia coli was monitored at PCD 6 and 34.Salmonella recovery from cloacal swabs indicated increased (P< .05) prevalence of CTCr salmonella-positive birds in the 550 ppm treatment at PCD 6 and 13 compared to all other treatments, and at PCD 27 compared to 0, 55, and 110 ppm CTC. Mean recovery scores followed a similar pattern. Area under the curve analysis of CTCr salmonella scores from cloacal swabs for PCD 3 to 41 confirmed increased (P<.05) selection for CTCr salmonella by 550 ppm CTC. Isolations from droppings showed increased (P<.05) CTCr salmonella prevalence at PCD 20 for the 100 ppm treatment group compared to control, and at PCD 34 for the 110 ppm groups compared to all other groups and for 220 and 550 ppm groups compared to 0 and 55 ppm CTC birds. The CTCr salmonella counts in droppings were higher (P<.05) at PCD 34 for the 110, 220, and 550 ppm groups compared to the control. The CTCrE. coli counts were higher (P<.05) in all medicated groups compared to control at PCD 6, but were not different among groups at PCD 34. Overall, short-term feeding of a high level of CTC to chickens selected as much or more CTC salmonella than did continuous feeding with subtherapeutic levels.

Synergistic cytolytic activity by combined populations of peritoneal T lymphocytes and macrophages during the L5178Y cell tumor-dormant state in DBA/2 mice

It was previously reported that the establishment of the L5178Y cell tumor-dormant state in DBA/2 mice is mediated principally by a peritoneal cytolytic T-cell response that reaches peak levels 4 days after L5178Y cell challenge, lyses more than 99% but less than 100% of peritoneal L5178Y cells, and gradually wanes to background levels by 40–70 days postchallenge (DPC). At this time the majority of mice are clinically normal, and contain a relatively small number of L5178Y cells in the peritoneal cavity. During the tumor-dormant state, mice that harbor more than 10 4 L5178Y cells contain peritoneal macrophage-mediated cytolytic activity. We report here that tumor-dormant mice that contain fewer than 10 4 peritoneal L5178Y cells also produce cytolytic activity in vitro, but that it is synergistic, in that the cytolytic activity of adherent (AD) peritoneal cells (PEC) and nonadherent (NAD) PEC cultured together is greater than the additive lysis produced by these cell populations when cultured separately. This synergistic cytolytic activity is: (1) effector cell density dependent, (2) dependent on the tumor-dormant status of the NAD and AD PEC donor mice, (3) protracted in its kinetics during a 48-hr in vitro assay, and (4) dependent on an interaction between NAD T cells and AD phagocytic macrophages. The consistent detection of this in vitro-assayed cytolytic activity in PEC of tumor-dormant mice which harbor small endogenous tumor burdens suggests that it reflects an in vivo cytotoxic effector mechanism involved in the long-term maintenance of the tumor-dormant state.

Therapy of experimental herpes simplex encephalitis with aciclovir in mice.

This report is concerned with the capacities of aciclovir to protect mice challenged intracerebrally with multiple lethal doses of type 1 herpes simplex virus and to control multiplication of this virus in the brain. With treatment initiated 12 h after inoculation and continued for 4 consecutive days, aciclovir administered subcutaneously in daily doses ranging from 40 to 100 mg/kg led to 21-day survival rates of from 33 to 73% and reduced virus titers by 1 to (1/2) x 4 logs on postchallenge day 8. The therapeutic accomplishments of the 100-mg/kg doses of aciclovir were comparable to those of 1,000-mg/kg doses of vidarabine (9-beta-d-arabinofuranosyladenine); however, as measured by impact on body weight, aciclovir was better tolerated than vidarabine at these similarly effective doses.

Clinical evaluation of prophylactic intranasal 1-phenyl-3-(4-phenyl-2-thiazolyl) guanidine (CL 88,277) medication against rhinovirus 44 challenge

The prophylactic intranasal medication with a new antiviral compound, 1-phenyl-3-(4 phenyl-2-thiazolyl) guanidine (CL 88,277) was evaluated in humans against rhinovirus 44 challenge. One ml containing 250 mg of CL 88,277 was administered to 10 seronegative volunteers three times a day plus one dose prior to the rhinovirus challenge (32 TCID 50) and for six consecutive post-challenge days. Ten other subjects received 56% polyethylene glycol (PEG-400), the solvent of CL 88,277 at the same time. Five subjects in each of the CL 88,277-treated and placebo-treated groups developed illness. There were no differences between the two groups in the occurrence of the severe illness and of the moderate and severe illnesses. Each sign and symptom occurred almost equally in the two groups and there was no difference in their scores between the two groups. The challenge virus was isolated from both groups but the total number of the virus isolates was less and the time span of virus excretion was shorter for the drug-treated group. The post-challenge serum antibody titers were markedly lower in the drug-treated group. Prophylactic intranasal CL 88,277 medication did not affect the course of illness induced by rhinovirus 44 challenge. It appears, however, that the virus replication in the nose was reduced and as a result the serum antibody response was diminished. PEG-400 caused a transient irritation of the nasal mucosa in all recipients.

Efficacy of Formalin-killed &lt;i&gt;Aeromonas hydrophila&lt;/i&gt; and &lt;i&gt;Streptococcus&lt;/i&gt; sp. Vaccine in Red Tilapia

Humoral response in red tilapia against formalin-killed Aeromonas hydrophila and Streptococ cus sp. vaccine administered by intraperitoneal injection was evaluated.The result indicated that A. hydrophila vaccine induced significantly differed (P&lt;0.05) high mean peak antibody titers of 925.87±467.92 and 4983.47±1832.74 in both primary and secondary immune response, respectively. However specific antibody produced by red tilapia in response to administration of Streptococcus sp. vaccine revealed only weak secondary response of 101.33±45.38. In separate experiment, relative protection in red tilapia immunized with A. hydrophila and Streptococcus sp. vaccine was conducted. Immunization were done by direct immersion for 1 hr in vaccine suspension and then challenged 2 weeks after by immersing fingerlings for 6 hr with virulent A. hydrophila and Streptococcus sp. Percent cumulative mortality in vaccinated and unvaccinated groups was compared after 14 days of post challenge. Red tilapia immunized by A. hydrophila vaccine demonstrated a particularly high level of immunity (76.67%) compared with unvaccinated (43.33%). Streptococcus sp. vaccine greatly reduced the mortality in vaccinated (31.67%) compared with unvaccinated fish (55%) but these differences in mortality were insignificant (P&gt;0.05). Results from this study indicated the importance of vaccine for increasing disease resistance against A. hydrophila and Streptococcus sp infection by stimulation of specific humoral immunity. However the most important factor must be the method of vaccine administration which should be effective and applicable to farm scale.DOI: 10.3126/on.v8i1.4333

Immunoelectrophoresis of Nasal Secretions Collected during a Common Cold: Observations Which Suggest a Mechanism of Seroimmunity in Viral Respiratory Infections

Summary Human nasal secretions collected prior to and during various stages of naturally-acquired or experimentally-induced common colds were analyzed for the presence of serum proteins by the method of immunoelectrophoresis. These analyses showed that serum albumin was present in all nasal secretion. Experimental challenge of volunteers by intranasal instillation of an infectious common cold secretion resulted in the appearance of serum gamma globulin in the nasal secretion within 48 hr in all subjects tested regardless of whether the individual developed a cold. Nasal washings from those volunteers who developed a symptomatic illness contained serum α- and β-globulins in addition to albumin and γ-globulin on the 4th and 6th postchallenge days. In contrast, nasal washings from asymptomatic volunteers showed only serum albumin and gamma globulin on the 4th and 6th postchallenge day. It is suggested that the latter group, those subjects clinically resistant to experimental challenge with the common cold virus, may exude specific antibody onto the mucous membrane within the first 48 hr after contact with the virus and by this mechanism abort further progression of the infection and the appearance of clinical illness. The action of viral neuraminidase on serum proteins in whole human serum and nasal secretion was demonstrated.