Elucidating Key Elements in the Multiplication of Influenza and Paramyxoviruses


Choppin, Purnell

In the spring of 1957 Asian Influenza, H2N2, appeared in China and eventually spread around the world. Cases peaked in the United States in October and November. Purnell Choppin (1929- ) arrived at the Rockefeller Institute in July of 1957 as a postdoctoral fellow. He came to Rockefeller because of its decades-long eminence in virology, including the work of Peyton Rous, Thomas Rivers, Richard Shope, Joseph Smadel, Max Theiler, and Frank Horsfall and Igor Tamm, whose laboratory he joined. When the 1957 flu pandemic spread to New York, Choppin isolated six strains of the H2N2 virus from patients he admitted to the Rockefeller Hospital, including one designated RI/5, that he isolated from himself. He used these and other strains of virus in research designed to explore the chemical composition and structure of the virus particle, how the virus attaches to and enters the cell, and the process of virus multiplication and assembly in infected cells. Such research is essential for developing effective prevention strategies, vaccines, and antiviral therapy.

Choppin later went on to identify the correct number of proteins in the virus particle in studies conducted with his students, postdoctoral fellows, and colleagues (Lawrence Caliguiri, Richard Compans, Hans-Dieter Klenk, Robert Lamb, Sondra Lazarowitz). These included four proteins associated with the viral membrane—the previously known hemagglutinin and neuraminidase on the outer surface, and two associated with the inner surface (M1 and M2)—and four internal proteins, one the nucleocapsid protein associated with the viral RNA and three involved with the replication of the RNA. The influenza virus particle is assembled by budding from the infected cell membrane and Choppin’s group found that the proteins of the viral membrane were virus-specific but the lipids of the viral membrane were those of the host cell.

Choppin also developed the first efficient system for studying the multiplication of influenza virus in tissue culture cells. Previously the virus had been grown in the laboratory in chick embryos, mice, or ferrets, which did not permit biochemical or microscopic studies at the cellular level. In addition to the proteins of the virus particle already mentioned, studies by Sondra Lazarowitz revealed the presence of two non-structural proteins in the nucleus of the cells. Another significant finding in this work was the fact that the hemagglutinin protein, which had long been known to be involved in the attachment of the virus particles to cells, was cleaved into smaller polypeptides, HA1 and HA2. The lack of this cleavage did not affect the ability of the virus to attach to cells, but was shown later independently in the Choppin laboratory and by Hans-Dieter Klenk, who had moved to the University of Giessen in Germany, that the cleavage was necessary for penetration of the virus into the cells.

Another fundamental contribution by members of the Choppin laboratory (Richard Compans, William Hall, Ming-chu Hsu, Hans-Dieter Klenk, Walter Mountcastle, Andreas Scheid) was to identify the complete set of viral proteins of members of the paramyxovirus group, a large group of viruses structurally related to influenza viruses which include, for example, parainfluenza, mumps, and measles viruses. Knowledge of these proteins permitted important studies on the viral structure and multiplication, including virus penetration and mechanisms involved in damaging cells.


The RI/5 strain of "Asian" Influenza A, H2N2, 1957. From Virology, 1964, 22(4): 482-492

The Choppin laboratory also had a long time interest in persistent virus infection. In studies of persistent measles virus infection William Hall found that subacute sclerosing panencephalitis (SSPE), a chronic neurological disease previously associated with measles, was the result of a persistent, but abortive, infection with measles virus. That is, the virus persisted in brain cells for years after the initial infection, but complete measles virus particles were not produced due to the lack of synthesis of one viral protein, the M protein, which is essential for viral budding from the cell membrane. This was the first explanation of the mechanism of an abortive persistent viral infection in a chronic disease.

Purnell Choppin received an MD degree from Louisiana State University School of Medicine (1953) and served as an intern and resident at Barnes Hospital, Washington University School of Medicine in St. Louis. After coming to the Rockefeller Institute in 1957, Choppin remained until 1985, advancing from postdoctoral fellow to Professor and Senior Physician to the Hospital. He also served as Vice President for Academic Programs and Dean of Graduate Studies. After leaving Rockefeller he joined the Howard Hughes Medical Institute where he served as President until retiring in 2000. He is a member of the U.S. National Academy of Sciences (1977) and its Institute of Medicine, the American Philosophical Society, and the American Academy of Arts and Sciences. His honors include the Howard Taylor Ricketts Award from the University of Chicago, the Selman A. Waksman Award for Excellence in Microbiology from the National Academy of Sciences, the Dean’s Medal from Harvard Medical School, the University of California at San Francisco Medal, the Johns Hopkins University Heritage Award, and several honorary degrees from universities in the United States and abroad.

Selected Publications

Choppin PW. Multiplication of two kinds of influenza A2 virus particles in monkey kidney cells. Virology, 1963, 21:342–352

Klenk H-D and Choppin PW. Chemical composition of the parainfluenza virus SV5. Virology, 1969, 37:155–157

Klenk H-D and Choppin PW. Lipids of plasma membranes of monkey and hamster kidney cells and of parainfluenza virions grown in these cells. Virology, 1969, 38:255–268

Caliguiri LA, Klenk H-D, and Choppin PW. The proteins of the parainfluenza virus SV5. I. Separation of virion polypeptides by polyacrylamide gel electrophoresis. Virology, 1969, 39: 460–466

Compans RW, Klenk H-D, Caliguiri LA, and Choppin PW. Influenza virus proteins. I. Analysis of polypeptides of the virion and identification of spike glycoproteins. Virology, 1970, 42:880–889

Lazarowitz SG, Compans RW, and Choppin PW. Influenza virus structural and non-structural proteins in infected cells and their plasma membranes. Virology, 1971, 46: 830–843

Lazarowitz SG and Choppin PW. Enhancement of the infectivity of influenza A and B viruses by proteolytic cleavage of the hemagglutinin polypeptide. Virology, 1975, 68: 440–454

Mountcastle WE and Choppin PW. A comparison of the polypeptides of four measles virus strains. Virology, 1977, 78: 463–474

Lamb RA and Choppin PW. Segment 8 of the influenza virus genome is unique in coding for two polypeptides. Proc Natl Acad Sci USA, 1979, 76: 4908–4911

Hall WW and Choppin PW. Measles virus proteins in the brain tissue of patients with subacute sclerosing panencephalitis: absence of the M protein. N Engl J Med, 1981, 304:1152–1155

Further Reading

Compans RW and Choppin PW. The structure and assembly of influenza and parainfluenza viruses. In Comparative Virology, Maramorosch K and Kurstak F, eds. New York: Academic Press, 1971, pp. 407–432

Choppin PW, Scheid A, Lazarowitz SG, McSharry JJ, and Compans RW. Proteins of viral membranes. In Workshop on Virus-Cell Interactions, Raspe G, ed., Adv In Biosciences 11, Pergamon Press, 1973, pp. 83–108

Choppin PW and Compans RW. Reproduction of paramyxoviruses. In Comprehensive Virology, vol. 4, Fraenkel-Conrat H and Wagner RR, eds. New York: Plenum Press, 1975, pp. 95–178

Compans RW and Choppin PW. Reproduction of myxoviruses. In Comprehensive Virology, vol. 4, Fraenkel-Conrat H and Wagner RR, eds. New York: Plenum Press, 1975, pp. 179–252