Reactions of influenza viruses with guinea pig polymorphonuclear leucocytes. I. Virus-cell interactions

Infectious Progeny of 2009 A (H1N1) Influenza Virus Replicated in and Released from Human Neutrophils

Various reports have indicated that a number of viruses could infect neutrophils, but the multiplication of viruses in neutrophils was abortive. Based on our previous finding that avian influenza viral RNA and proteins were present in the nucleus of infected human neutrophils in vivo, we investigated the possibility of 2009 A (H1N1) influenza viral synthesis in infected neutrophils and possible release of infectious progeny from host cells. In this study we found that human neutrophils in vitro without detectable level of sialic acid expression could be infected by this virus strain. We also show that the infected neutrophils can not only synthesize 2009 A (H1N1) viral mRNA and proteins, but also produce infectious progeny. These findings suggest that infectious progeny of 2009 A (H1N1) influenza virus could be replicated in and released from human neutrophils with possible clinical implications.

Interferon production by mouse leukocytes in vitro and in vivo

Vaccinia virus penetrates, or is phagocytosed by, mouse leukocytes in vitro. A cytotoxic effect is observed, but no new infectious virus is produced. Vaccinia virus, as infectious particles, is eliminated from a culture of leukocytes at a more rapid rate than can be accounted for by thermal inactivation. Leukocytes infected with vaccinia virus produce a substance with the properties of interferon. The evidence presented suggests that leukocytes also produce interferon in vivo and that this interferon is related to the observed protective effect on the outcome of intracerebral vesicular stomatitis virus challenge in mice. It is postulated that leukocytes, in this manner, may make a positive contribution to the host's defense mechanism and to the process of recovery from viral infections.

ELECTRON MICROSCOPY OF IN VITRO ENDOCYTOSIS OF T2 PHAGE BY CELLS FROM RABBIT PERITONEAL EXUDATE

Macrophages from rabbit peritoneal exudate cells incubated in vitro with T₂ bacteriophage from 10 up to 120 minutes show phage particles adsorbed to cell membranes, in the process of being engulfed by means of rhopheocytosis, micropinocytosis, and phagocytosis, and localized within dense vacuoles, semi-dense vacuoles, and clear vacuoles of the cytoplasm. The electronmicrographs suggest that newly formed endocytic vacuoles containing phage particles fuse with one another and also fuse with dense bodies of the cytoplasm as they migrate towards the cell interior, thus yielding larger vacuoles of varying densities containing higher concentrations of phage. The polymorphonuclear cells present in a small proportion in the peritoneal exudate cells also endocytosed phage particles. The T₂ particles are found in large cytoplasmic vacuoles surrounded by an electron-opaque material presumably derived from cytoplasmic granules. No disintegration of T₂ phage within the macrophage following incubations up to 120 minutes could be demonstrated; however, disrupted phage particles were noted within cytoplasmic vacuoles of polymorphonuclear leucocytes after 15 minutes' incubation.

Synthesis of viral proteins in polymorphonuclear leukocytes infected with influenza A virus

Various reports have indicated that infection of polymorphonuclear leukocytes (PMNL) with influenza virus causes depression of their metabolic and chemotactic responses, but the effect the PMNL has on the life cycle of influenza virus has not been well defined. The studies reported here were undertaken to determine whether influenza virus could replicate within PMNL. Virus-infected and uninfected PMNL were labeled with [35S]methionine and analyzed by gel electrophoresis and fluorography for detection of newly synthesized proteins. Both host- and virus-specific proteins were produced within PMNL. By using indirect immunofluorescence techniques combined with flow cytometry, the expression of newly synthesized viral antigens was detected in virus-infected PMNL. Plaque assays on supernatant fluid from infected PMNL showed that infectious progeny were not produced, indicating that influenza virus infection of PMNL is abortive.

The NBT (Nitroblue Tetrazolium) activity of neutrophil granulocytes in patients with influenza A infection

The NBT activity of granulocytes from 11 influenza patients was determined during the acute stage of the disease and 6-8 weeks after recovery. The NBT activity was generally higher during influenza than after recovery. In the presence as well as in the absence of the patient's serum the differences were significant both without and with Escherichia coli stimulation.

Specific role of each human leukocyte type in viral infections. I. Monocyte as host cell for vesicular stomatitis virus replication in vitro

Each major leukocyte type of the peripheral blood of healthy donors was studied in vitro for its ability to support vesicular stomatitis virus (VSV) replication. Purified cultures of each white blood cell type were prepared by the selective adsorption and elution of cells from silicone-treated glass beads. It was found that monocytes and macrophages (derived from the rapid transformation of monocytes in vitro) were the principal host cells for VSV replication. Interferon added to mixed leukocyte cultures, prior to virus inoculation, reduced virus yields and prevented destruction of macrophages. Cultures of small lymphocytes, containing no detectable monocytes or macrophages, produced amounts of virus equivalent to 1% of that produced in leukocyte cultures which contained 7% monocytes. Small lymphocytes did not undergo demonstrable cytopathic alterations in virus-infected cultures. VSV neither replicated nor produced cytopathic effects in polymorphonuclear leukocytes.

Leeuwenhoek Lecture: Virus-host cell interactions

To-day’s lecture is the eighth of the series founded to honour the memory of Anthony van Leeuwenhoek who is rightly regarded as the ‘father of microbiology'. More than a century and a half had to elapse after Leeuwenhoek’s death in 1723 before a virus was isolated. Many more years passed before virology became established as a legitimate branch of microbiology. Yet, for a third time, the Leeuwenhoek lecture is to be devoted to a consideration of the viruses. To some this may seem inappropriate but there are three reasons which seem to me to justify the choice of subject. First, virology is, today, probably the most rapidly expanding field of microbiological research; secondly, Leeuwenhoek’s insatiable curiosity about creatures infinitely small would undoubtedly lead him into virus research were he still alive; thirdly, my own chief research interests lie in certain aspects of virology. The question ‘What is a virus?’ has often been asked without so far being satisfactorily answered. I shall make no attempt at a definition. For the purposes of present discussion the term ‘virus’ will be used in the widest possible sense to embrace all those agents of transmissible diseases which, for valid reasons, cannot be included in the various categories of unicellular disease incitants, irrespective of whether they are highly organized like vaccinia virus or consist of crystallizable protein like tobacco mosaic virus. Whether any stricter limitation of the term is either desirable or possible may perhaps emerge in the course of the lecture. The most fundamental characteristic of the viruses is their obligate cell parasitism. Those of the three main types, animal, plant and bacterial, differ in several very important respects but they share, in common, this necessity of entering into intimate association with the cells of higher organisms in order to multiply and survive. Clearly, therefore, elucidation of the host-parasite interactions at the cellular level must be achieved before we can understand fully the diverse phenomena resulting from virus activities.

STUDIES ON THE PATHOGENESIS OF FEVER WITH INFLUENZAL VIRUSES

A substance with pyrogenic properties appears in the blood streams of rabbits made febrile by the intravenous inoculation of the PR8 strain of influenza A and Newcastle disease viruses (NDV). By means of a technique involving passive transfer of sera from animals given virus to recipient rabbits, the titer of circulating pyrogen was found to be closely correlated with the course of fever produced by virus. Certain properties of the pyrogen are described which differentiate it from the originally injected virus and suggest that the induced pyrogen is of endogenous origin. These properties resemble those of endogenous pyrogens occurring in other forms of experimental fever. The source of virus-induced pyrogen is unknown. In vitro incubation of virus with various constituents of the circulation did not result in the appearance of endogenous pyrogen. Granulocytopenia induced by HN(2) failed to influence either fever or the production of endogenous pyrogen in rabbits injected with NDV. Similarly, the intraperitoneal inoculation of NDV into prepared exudates did not modify the febrile response. These findings do not lend support to the possibility that the polymorphonuclear leukocyte is a significant source of endogenous pyrogen in virus-induced fever. It is concluded that the liberation of an endogenous pyrogen from some as yet undefined source is an essential step in the pathogenesis of fever caused by the influenza group of viruses.