CNS disease following dissemination of SSPE measles virus from intraperitoneal inoculation of suckling hamsters

Expression of five viral antigens in cells infected with wild-type and SSPE strains of measles virus: correlation with cytopathic effects and productivity of infections

Cells infected with four strains (LEC, Biken, IP-3 and DR) of subacute sclerosing panencephalitis (SSPE) virus were compared with wild type measles virus (Edmonston) with respect to titers of extracellular virus, morphology of the cytopathic effect (CPE) and occurrence of different measles virus antigens within infected cells as determined by immune fluorescence. Murine monoclonal antibodies with specifities for the nucleocapsid (NP), polymerase (P), matrix (M), hemagglutinin (H), and fusion (F) proteins as well as specific hyperimmune sera prepared in rabbits against the NP, H and M proteins were used in immune fluorescence analyses of the various strains. All of the strains produced large amounts of NP and P. Only the NP antigen occurred in nuclei of cells. The Edmonston and LEC strains also showed bright fluorescence with the antibodies against the H, F, and M antigens. Immune fluorescent intensity was variably reduced in cells infected with the Biken, IP-3, and DR strains labelled with anti M, H, and F antibodies. The Biken strain produced moderate titers of extracellular virus and moderate amounts of M, H, and F antigens whereas the DR strain produced no extracellular virus and contained no detectable M or F and only trace amounts of H antigen. The IP-3 strain was intermediate both in antigen expression and in production of extracellular virus.

Reversible repression and activation of measles virus infection in neural cells

Conversion of acute measles virus infection to an indolent state has been achieved by treatment of infected cells of neural origin with agents that affect cyclic nucleotide metabolism. Striking results were obtained with papaverine, an inhibitor of cAMP phosphodiesterase that is capable of enhancing neural differentiation. In papaverine-treated cultures, decreased production of infectious virus was accompanied by selective disappearance of intracellular matrix proton, as detected by immunofluorescence. Viral nucleocapsid protein was enhanced in the cytoplasm while three other structural proteins--polymerase, hemagglutinin, and fusion protein--showed little change in distribution or intensity of staining. These results were specific for cells of neural origin and not observed in CV-1 or Vero cultures. cAMP, dibutyryl cAMP, 8-bromo-cAMP, and isobutylmethylxanthine all inhibited replication of virus but less so than did papaverine. Inhibition of virus replication by any of these agents was rapidly reversible, either by removal of the agent or by addition of cGMP to the culture medium and was accompanied by reappearance of the matrix protein. These results suggest that measles virus replication in neural cells depends on host factors, particularly those affecting endogenous cAMP and cGMP. Viral persistence may thus be related to the state of neural differentiation. This model system may yield information on mechanisms of recrudescence observed in some chronic diseases of the nervous system.

Lymphoid cell infection by measles virus in newborn hamsters. Role for monocytes in virus spread to distant sites

Following intraperitoneal inoculation of measles (HBS) virus into newborn hamsters widespread but variable productive lymphoid tissue infection was detected by a sensitive viral isolation technique. Peritoneal wash cells and spleen were the most common sites of infection. Virus was frequently isolated from the bone marrow and was commonly found in multiple lymph nodes. Thymic infection was only rarely demonstrated. A mononuclear cell associated viremia was demonstrated by Ficollhypaque fractionation of peripheral blood from animals receiving both high- and low-dose virus. Infection was present in both plastic adherent and non-adherent fractions of the blood mononuclear cells. The infected cell population in the spleen had both nylon wool and plastic adherent characteristics and infection was therefore thought to be macrophage-associated. The possible relevance of such macrophage associated infection is discussed with regard to the pathogenesis of natural measles infection and the immunosuppression observed in measles-infected hosts.

Encephalitis after inhalation of measles virus: a pathogenetic study in hamsters

A neuroadapted strain of measles virus (HNT) was administered by inhalation to newborn hamsters. Primary replication of virus in the lung was followed by the transient appearance of virus in spleen within 7 to 9 days of inoculation. A terminal encephalitis occurred between 6 and 60 days in 31% of infected hamsters, and virus was recovered by explant culture of these brains. Virus could not be cultured directly from brain or tissue homogenates. At least 7% of hamsters that had survived the infection for two months had antibody to measles virus. The histopathological change in morbid animals was limited to the central nervous system (CNS) and consisted of small foci of necrosis, perivascular mononuclear cell infiltrates, intracytoplasmic and intranuclear inclusions, and vacuolated pyknotic neurons. Immunofluorescent studies disclosed measles antigen in the lungs and brain. This hamster model of measles encephalitis following a "natural" route of inoculation appears to represent a faithful reproduction of certain CNS complications of natural measles infection in humans, i.e., measles encephalitis and subacute sclerosing panencephalitis.