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Biomedical subjects

J M Katz

Publications and source records attributed to J M Katz.

At least 19 recordsLinked to original sources
PubMed2004

Influenza vaccines generated by reverse genetics.

Influenza viruses cause annual epidemics and occasional pandemics of acute respiratory disease. Vaccination is the primary means to prevent and control the disease. However, influenza viruses undergo continual antigenic variation, which requires the annual reformulation of trivalent influenza vaccines, making influenza unique among pathogens for which vaccines have been developed. The segmented nature of the influenza virus genome allows for the traditional reassortment between two viruses in a coinfected cell. This technique has long been used to generate strains for the preparation of either inactivated or live attenuated influenza vaccines. Recent advancements in reverse genetics techniques now make it possible to generate influenza viruses entirely from cloned plasmid DNA by cotransfection of appropriate cells with 8 or 12 plasmids encoding the influenza virion sense RNA and/or mRNA. Once regulatory issues have been addressed, this technology will enable the routine and rapid generation of strains for either inactivated or live attenuated influenza vaccine. In addition, the technology offers the potential for new vaccine strategies based on the generation of genetically engineered donors attenuated through directed mutation of one or more internal genes. Reverse genetics techniques are also proving to be important for the development of pandemic influenza vaccines, because the technology provides a means to modify genes to remove virulence determinants found in highly pathogenic avian strains. The future of influenza prevention and control lies in the application of this powerful technology for the generation of safe and more effective influenza vaccines.

Animals↗
PubMed2003

Neurological manifestations of avian influenza viruses in mammals.

The H5N1 viruses isolated from humans in Hong Kong directly infected both mice and ferrets without prior adaptation to either host. Two representative viruses, A/Hong Kong/483/97 (HK/483) and A/Hong Kong/486/97 (HK/486) were equally virulent in outbred ferrets but differed in their virulence in inbred mice. Both HK/483 and HK/486 replicated systemically in ferrets and showed neurologic manifestations. In contrast, intranasal infection of mice with HK/483, but not HK/486, resulted in viral spread to the brain, neurologic signs, and death. However, HK/486 was able to replicate in the brain and induce lethal disease following direct intracerebral inoculation.

Animals↗
PubMed2003

Mechanisms of pathogenicity of influenza A (H5N1) viruses in mice.

Avian-like H5N1 influenza viruses isolated from humans in 1997 were shown to have two distinct pathogenic phenotypes in BALB/c mice, after intranasal inoculation and without prior adaptation to this host. To further understand the mechanisms of H5N1 pathogenicity, we investigated the consequences of the mute of viral inoculation on morbidity and mortality, viral replication in pulmonary and systemic organs, and lymphocyte depletion. This study demonstrates the importance of extrapulmonary spread and replication, particularly in the brain, for the lethality of H5N1 viruses.

Animals↗
PubMed2003

Pathogenesis of and immunity to a new influenza A (H5N1) virus isolated from duck meat.

The outbreak of avian influenza H5N1 in Hong Kong in 1997 raised concerns about the potential for the H5 subtype to cause a human pandemic. In 2001 a new H5N1 virus, A/Duck Meat/Anyang/AVL-1/2001 (A/Dkmt), was isolated from imported duck meat in Korea. The pathogenesis of this virus was investigated in mice. A/Dkmt virus had low infectivity but was lethal for mice at high doses, and at lethal doses, the virus replicated in the brains of infected mice. A/Dkmt virus cross-reacted poorly with ferret antisera raised against human H5N1 viruses, but prior infection with A/Dkmt virus protected mice from death after secondary infection with human H5N1 virus.

Animals↗
PubMed2003

The impact of avian influenza viruses on public health.

In the late 1990s, H5N1 and H9N2 avian influenza viruses caused respiratory infections in humans in Hong Kong. Exposure to domestic poultry in live-bird markets was significantly associated with human H5N1 disease. Seroepidemiologic studies conducted among contacts of H5N1-infected persons determined that human-to-human transmission of the avian H5N1 viruses occurred but was rare. The relatively high rates of H5 and H9 antibody seroprevalence among Hong Kong poultry workers in 1997 highlight the potential for avian viruses to transmit to humans, particularly those with occupational exposure. Such transmission increases the likelihood of reassortment between a currently circulating human virus and an avian virus and thus the creation of a strain with pandemic potential.

Animals↗
PubMed2003

Current methods for assessing T cell responses to influenza.

Traditional methods for the detection of T cell responses to influenza include the lymphoproliferation assay for CD4+ T cells and 51Cr-release assay for the detection of cytotoxic CD8+ T lymphocyte activity. These assays are labour-intensive, require extended periods of cell culture and provide only qualitative data on a bulk population of lymphocytes. Thus, they have been of limited use in dissecting the cellular immune response to influenza infection and vaccination in humans. In recent years, newer methods that detect single cell production of cytokines and binding of tetrameric MHC-peptide complexes by antigen-specific T cells have become available. These assays provide a means of measuring absolute frequencies of functional antigen-specific T cell responses without the need for extended periods of culture. Although still technically demanding, these modern assays represent important new tools for the quantitative analysis of T cell responses to influenza infection and vaccination.

Cell Division↗
PubMed2001

Influenza virus-stimulated generation of anti-human immunodeficiency virus (HIV) activity after influenza vaccination in HIV-infected individuals and healthy control subjects.

Influenza virus stimulation of leukocytes induces factors that suppress human immunodeficiency virus (HIV). The effect of influenza vaccination on influenza-induced anti-HIV activity was investigated. Influenza vaccine was administered to 25 control subjects and 20 HIV-infected patients. Antiviral activity, cytokine production, and influenza antibodies were assessed before and 2 and 6 weeks after vaccination. Immunization induced a statistically significant increase in antiviral activity in control subjects but not in HIV patients, although the number of patients who generated this activity increased. Pre- and postvaccination levels of anti-HIV activity were significantly lower in HIV patients. Vaccination of control subjects and HIV patients induced increases in production of interleukin-2 and interferon (IFN)-gamma, but not of IFN-alpha. Virus load and CD4 cell counts were not significantly altered. This study demonstrates impairment of antiviral activity in HIV patients, in addition to deficiencies in antibody responses and cytokine production. In summary, influenza vaccination can induce an increase in multiple immunologic components that remained impaired in HIV patients.

Antibodies, Viral↗
PubMed2001

Safety and immunogenicity of a recombinant hemagglutinin vaccine for H5 influenza in humans.

Recent outbreaks of avian influenza in humans have demonstrated the need for vaccines for influenza viruses with pandemic potential. Recombinant hemagglutinins are an attractive option for such vaccines because they do not require handling potentially highly pathogenic influenza viruses for vaccine production. In order to evaluate the immunogenicity, optimum dosing and timing of administration of a recombinant baculovirus-expressed H5 HA (rH5) in humans, 147 healthy adults were assigned randomly to receive intramuscular rH5 as two doses of 25, 45 or 90 microg each, one dose of 90 microg followed by a dose of 10 microg, or two doses of placebo, at intervals between doses of 21, 28 or 42 days. All doses of rH5 were well tolerated. The rH5 vaccine was modestly immunogenic at high dose. Neutralizing antibody responses to a titer of 1:80 or greater were seen in 23% (14/60) of individuals after a single dose of 90 microg, and in 52% (15/29) after two doses of 90 microg. Varying intervals between doses from 21 to 42 days had no significant effect on antibody responses to vaccination. These results suggest that baculovirus-expressed H5 HA can induce functional antibody in individuals who have not had prior exposure to H5 viruses, but that further studies to improve the immunogenicity of the vaccine are needed.

Adult↗
PubMed2001

The ubiquitin-proteasome pathway plays an essential role in proteolysis during Trypanosoma cruzi remodeling.

Here, we document for the first time the presence of the 26S proteasome and the ubiquitin pathway in a protozoan parasite that is in an early branch in the eukaryotic lineage. The 26S proteasome of Trypanosoma cruzi epimastigotes was identified as a high molecular weight complex (1400 kDa) with an ATP-dependent chymotrypsin-like activity against the substrate Suc-LLVY-Amc. This activity was inhibited by proteasome inhibitors and showed same electrophorectic migration pattern as yeast 26S proteasome in nondenaturating gels. About 30 proteins in a range of 25-110 kDa were detected in the purified T. cruzi 26S proteasome. Antibodies raised against the AAA family of ATPases from eukaryotic 26S proteasome and the T. cruzi 20S core specifically recognized components of T. cruzi 26S. To confirm the biological role of 26S in this primitive eukaryotic parasite, we analyzed the participation of the ubiquitin (Ub)-proteasome system in protein degradation during the time of parasite remodeling. Protein turnover in trypomastigotes was proteasome and ATP-dependent and was enhanced during the transformation of the parasites into amastigotes. If 20S proteasome activity is inhibited, ubiquitinated proteins accumulate in the parasites. As expected from the profound morphological changes that occur during transformation, cytoskeletal proteins associated with the flagellum are targets of the ubiquitin-proteasome pathway.

Acetylcysteine↗
PubMed2001

Immunity to influenza A H9N2 viruses induced by infection and vaccination.

Avian influenza A H9N2 viruses are widespread among domestic poultry and were recently isolated from humans with respiratory illness in China. Two antigenically and genetically distinct groups of H9N2 viruses (G1 and G9) are prevalent in China. To evaluate a strategy for vaccination, we compared G1 and G9 viruses for their relative immunogenicity and cross-protective efficacy. Infection of BALB/c mice with representative viruses of either group protected against subsequent challenge with the homologous or heterologous H9N2 virus in the absence of detectable cross-reactive serum hemagglutination inhibition antibody. Mice injected intramuscularly with inactivated G1 whole virus vaccine were completely protected from challenge with either H9N2 virus. In contrast, mice administered inactivated G9 vaccine were only partially protected against heterologous challenge with the G1 virus. These results have implications for the development of human vaccines against H9N2 viruses, a priority for pandemic preparedness.

Animals↗
PubMed2001

Mucosal delivery of inactivated influenza vaccine induces B-cell-dependent heterosubtypic cross-protection against lethal influenza A H5N1 virus infection.

Influenza vaccines that induce greater cross-reactive or heterosubtypic immunity (Het-I) may overcome limitations in vaccine efficacy imposed by the antigenic variability of influenza A viruses. We have compared mucosal versus traditional parenteral administration of inactivated influenza vaccine for the ability to induce Het-I in BALB/c mice and evaluated a modified Escherichia coli heat-labile enterotoxin adjuvant, LT(R192G), for augmentation of Het-I. Mice that received three intranasal (i.n.) immunizations of H3N2 vaccine in the presence of LT(R192G) were completely protected against lethal challenge with a highly pathogenic human H5N1 virus and had nasal and lung viral titers that were at least 2,500-fold lower than those of control mice receiving LT(R192G) alone. In contrast, mice that received three vaccinations of H3N2 vaccine subcutaneously in the presence or absence of LT(R192G) or incomplete Freund's adjuvant were not protected against lethal challenge and had no significant reductions in tissue virus titers observed on day 5 post-H5N1 virus challenge. Mice that were i.n. administered H3N2 vaccine alone, without LT(R192G), displayed partial protection against heterosubtypic challenge. The immune mediators of Het-I were investigated. The functional role of B and CD8+ T cells in Het-I were evaluated by using gene-targeted B-cell (IgH-6(-/-))- or beta2-microglobulin (beta2m(-/-))-deficient mice, respectively. beta2m(-/-) but not IgH-6(-/-) vaccinated mice were protected by Het-I and survived a lethal infection with H5N1, suggesting that B cells, but not CD8+ T cells, were vital for protection of mice against heterosubtypic challenge. Nevertheless, CD8+ T cells contributed to viral clearance in the lungs and brain tissues of heterotypically immune mice. Mucosal but not parenteral vaccination induced subtype cross-reactive lung immunoglobulin G (IgG), IgA, and serum IgG anti-hemagglutinin antibodies, suggesting the presence of a common cross-reactive epitope in the hemagglutinins of H3 and H5. These results suggest a strategy of mucosal vaccination that stimulates cross-protection against multiple influenza virus subtypes, including viruses with pandemic potential.

Adjuvants, Immunologic↗
PubMed2000

Immunogenicity and efficacy of Russian live attenuated and US inactivated influenza vaccines used alone and in combination in nursing home residents.

The immunogenicity and efficacy of Russian live attenuated and US inactivated trivalent influenza vaccines administered alone or in three different combinations were evaluated in a randomized, placebo-controlled, double-blinded study of 614 elderly or chronically ill nursing home residents in St. Petersburg, Russia during the 1996-97 influenza season. Postvaccination serum antibody responses were more frequent among individuals administered the combination vaccines than among those vaccinated with live or inactivated vaccine alone. Only individuals who received live vaccine, alone or in combination with inactivated vaccine, achieved significant postvaccination increases in virus-specific nasal IgA. Efficacy in preventing laboratory-confirmed influenza in vaccinated versus nonvaccinated individuals was 67% (95%CI, 36-81%) for recipients of a combination of the vaccines compared with 51% (95%CI, -17-79%) for recipients of live vaccine alone and 50% (95%CI, -26-80%) for recipients of inactivated vaccine alone. These results suggest that administration of a combination of influenza vaccines may provide a strategy for improved influenza vaccination of elderly people.

Adult↗
PubMed2000

A nonionic block co-polymer adjuvant (CRL1005) enhances the immunogenicity and protective efficacy of inactivated influenza vaccine in young and aged mice.

The use of adjuvants is one approach to improve influenza vaccine immunogenicity and efficacy, particularly in aged populations. The response of BALB/c mice to subcutaneously administered formalin-inactivated whole influenza virus vaccine in the presence or absence of a nonionic block copolymer adjuvant CRL1005 was evaluated. In young adult naïve mice, the copolymer adjuvant significantly enhanced virus-specific IgG and hemagglutination-inhibition (HI) antibody responses and augmented the production of IL-2 following vaccination. Influenza vaccine formulated with 2.5 mg CRL1005 significantly enhanced the protective efficacy of the inactivated vaccine in the upper and lower respiratory tract. In mice previously infected with influenza virus or naïve aged mice, inactivated vaccine administered with the copolymer adjuvant substantially enhanced the serum HI antibody response to inactivated influenza vaccine and significantly reduced lung virus titers following subsequent challenge with live virus compared with mice administered vaccine alone. These results suggest that the copolymer adjuvant warrants further investigation as a potential adjuvant for use in human vaccination against influenza.

Adjuvants, Immunologic↗
PubMed2000

Pathogenesis of and immunity to avian influenza A H5 viruses.

In 1997 in Hong Kong, 18 human cases of respiratory illness were caused by an avian influenza A H5N1 virus. Although avian influenza viruses had not previously been known to cause respiratory illness in humans, the H5N1 viruses caused severe illness and death, primarily in individuals aged > 12 years. The introduction of H5N1 viruses into humans raised concerns about the potential of these viruses to cause a pandemic. We have used the BALB/c mouse to better understand the pathogenesis of and immunity to the H5N1 viruses in a mammalian model. Previously, we demonstrated that H5N1 viruses isolated from humans replicated efficiently in the lungs of mice without prior adaptation to this host. Two general phenotypes of pathogenicity of H5N1 viruses, based on high and low lethality for mice, were observed. We now demonstrate that in addition to a lethal outcome, H5N1 viruses with a high pathogenicity phenotype exhibit additional features that include rapid and uncontrolled replication in the lungs of infected mice, dissemination and replication of the virus in other organs, and depletion of peripheral blood leukocytes. The BALB/c mouse model was also used to better understand the parameters of protective immunity to the H5N1 viruses. Prior infection with H5N1 viruses of low pathogenicity or an antigenically related non-pathogenic H5N3 virus protected mice from death by infection with a highly pathogenic HK/483 virus. Serum hemagglutination-inhibition antibody titers of 40 or greater were associated with protection of mice from death. Immunization of mice with baculovirus-expressed recombinant H5 hemagglutinin protein or a previously defined HS-specific synthetic peptide induced MHC class II restricted CTL activity. Mice that had CTL activity but no serum hemagglutination-inhibition antibody were not protected from a lethal challenge with H5N1 virus. These results suggest that antibody is required for protection of mice against lethal challenge with H5N1 viruses of the high pathogenicity phenotype.

Animals↗
PubMed2000

Risk of influenza A (H5N1) infection among health care workers exposed to patients with influenza A (H5N1), Hong Kong.

The first outbreak of avian influenza A (H5N1) occurred among humans in Hong Kong in 1997. To estimate the risk of person-to-person transmission, a retrospective cohort study was conducted to compare the prevalence of H5N1 antibody among health care workers (HCWs) exposed to H5N1 case-patients with the prevalence among nonexposed HCWs. Information on H5N1 case-patient and poultry exposures and blood samples for H5N1-specific antibody testing were collected. Eight (3.7%) of 217 exposed and 2 (0.7%) of 309 nonexposed HCWs were H5N1 seropositive (P=.01). The difference remained significant after controlling for poultry exposure (P=.01). This study presents the first epidemiologic evidence that H5N1 viruses were transmitted from patients to HCWs. Human-to-human transmission of avian influenza may increase the chances for the emergence of a novel influenza virus with pandemic potential.

Adult↗
PubMed2000

Depletion of lymphocytes and diminished cytokine production in mice infected with a highly virulent influenza A (H5N1) virus isolated from humans.

Previously, we observed that several virulent influenza A (H5N1) viruses which caused severe or fatal disease in humans were also lethal in BALB/c mice following dissemination of the virus to solid organs, including the brain. In contrast, one particular human H5N1 virus was nonlethal in mice and showed no evidence of systemic spread. To compare H5N1 viruses of varying pathogenicity for their ability to alter the mammalian immune system, mice were infected with either influenza A/Hong Kong/483/97 (HK/483) (lethal) or A/Hong Kong/486/97 (HK/486) (nonlethal) virus and monitored for lymphocyte depletion in the blood, lungs, and lymphoid tissue. Intranasal infection with HK/483 resulted in a significant decrease in the total number of circulating leukocytes evident as early as day 2 postinfection. Differential blood counts demonstrated up to an 80% drop in lymphocytes by day 4 postinfection. In contrast, nonlethal HK/486-infected mice displayed only a transient drop of lymphocytes during the infectious period. Analysis of lung and lymphoid tissue from HK/483-infected mice demonstrated a reduction in the number of CD4(+) and CD8(+) T cells and reduced synthesis of the cytokines interleukin-1beta and gamma interferon and the chemokine macrophage inflammatory protein compared with HK/486-infected mice. In contrast, the cytokine and chemokine levels were increased in the brains of mice infected with HK/483 but not HK/486. Evidence of apoptosis in the spleen and lung of HK/483-infected mice was detected in situ, suggesting a mechanism for lymphocyte destruction. These results suggest that destructive effects on the immune system may be one factor that contributes to the pathogenesis of H5N1 viruses in mammalian hosts.

Animals↗
PubMed2000

Molecular correlates of influenza A H5N1 virus pathogenesis in mice.

Highly pathogenic avian influenza A H5N1 viruses caused an outbreak of human respiratory illness in Hong Kong. Of 15 human H5N1 isolates characterized, nine displayed a high-, five a low-, and one an intermediate-pathogenicity phenotype in the BALB/c mouse model. Sequence analysis determined that five specific amino acids in four proteins correlated with pathogenicity in mice. Alone or in combination, these specific residues are the likely determinants of virulence of human H5N1 influenza viruses in this model.

Adolescent↗