STUDIES ON HERPETIC INFECTION IN MICE : IV. THE EFFECT OF SPECIFIC ANTIBODIES ON THE PROGRESSION OF THE VIRUS WITHIN THE NERVOUS SYSTEM OF YOUNG MICE

Varicella zoster virus latency

Primary infection by varicella zoster virus (VZV) typically results in childhood chickenpox, at which time latency is established in the neurons of the cranial nerve, dorsal root and autonomic ganglia along the entire neuraxis. During latency, the histone-associated virus genome assumes a circular episomal configuration from which transcription is epigenetically regulated. The lack of an animal model in which VZV latency and reactivation can be studied, along with the difficulty in obtaining high-titer cell-free virus, has limited much of our understanding of VZV latency to descriptive studies of ganglia removed at autopsy and analogy to HSV-1, the prototype alphaherpesvirus. However, the lack of miRNA, detectable latency-associated transcript and T-cell surveillance during VZV latency highlight basic differences between the two neurotropic herpesviruses. This article focuses on VZV latency: establishment, maintenance and reactivation. Comparisons are made with HSV-1, with specific attention to differences that make these viruses unique human pathogens.

Studies on herpetic infection in mice. V. Influence of route of inoculation on susceptibility to herpetic infection; effect of age, and of methylcholanthrene

1. The severity of herpetic infection, of mice varied according to the site of inoculation, decreasing in the following order: cornea, skin of abdomen, pad of hind foot, tail. 2. The preliminary treatment of the foot pad or tail with methylcholanthrene increased the susceptibility to herpetic infection to a limited extent. 3. Two-week-old mice showed a much greater susceptibility to herpes virus inoculated on the tail or on the pad of the hind foot than did adult mice. 4. The HF strain of herpes virus, after more than 125 serial brain-to-brain passages in mice, possessed high virulence for cutaneous tissues of mice and showed no important differences in this respect from a recently isolated strain (Klee) of herpes virus.

Passive transfer of anti-HSV-1 IgG protects against stromal keratitis in mice

Cellular immune mechanisms are felt to play a primary role in modulating responses to herpes simplex virus (HSV) infections, but the role of anti-HSV antibody is less clear. We first investigated the effects of passive transfer of murine serum containing anti-HSV antibody and then fractionated IgG subclasses on the development of HSV stromal keratitis in mice. Both immune sera and fractionated IgG's from these sera were effective in preventing stromal keratitis in susceptible mice. Non-IgG immunoglobulins and other serum proteins are unnecessary and inadequate in transferring protection; transfer of sera depleted of IgG had no influence on the development of keratitis. These results suggest an important role for anti-HSV antibody in modulating destructive corneal responses to HSV.

Protective effect of passive immunization on herpetic retinitis of newborn rabbits

We studied the protective effects of passive immunization with virus specific antibody in newborn rabbits inoculated subcutaneously with type 2 herpes simplex virus (HSV-2). Newborn rabbits given anti-HSV-2 antibody intraperitoneally (IP) on days 0, 2 and 4 post infection had smaller herpetic skin lesions and reduced mortality when compared to controls. In addition, the IP treatment using this schedule reduced virus growth in the skin lesions and virus dissemination, so that it decreased the frequency of herpetic retinitis. When the IP antibody administration was started at 24 hours post virus inoculation, according to the schedule days 1, 3 and 5, there was less protection; larger skin lesions, higher mortality, and greater evidence of virus dissemination. Also HSV-infected mononuclear cells (MNCs) treated with anti-HSV serum resulted in a significant reduction in the number of infected MNCs. The results of these studies suggest that anti-HSV-2 antibody contributes to protection against HSV-2 infection of skin as well as eyes, probably by inactivation of the virus locally at the skin inoculation site, and by combating the hematogenous spread of HSV-infected MNCs as well as free virus to various organs including the eye.

Role of neutralizing antibodies and T-cells in pathogenesis of herpes simplex virus infection in congenitally athymic mice

Congenitally athymic nude mice were infected with 10(4) p.f.u. herpes simplex type 1 (strain SC16). Following the passive transfer of neutralizing monoclonal antibodies (AP7, AP8 and AP12) it was observed that AP7 alone reduced the virus infectivity in the nervous system; AP8 and AP12 failed to protect mice probably due to poor in vivo binding to the neutralization site on the virus. Latent ganglionic infection could be established in nude mice following adoptive transfer of optimum number (2 x 10(7) cells/mouse) of immune lymph node cells from day 7 herpes virus-infected hairy immunocompetent donor mice. Moreover, in some of the immune lymph node cell protected nudes, latency could be maintained even in complete absence of neutralizing antibodies. Results of ear-ablation experiments revealed that removal of primary source of infection after day 5 of infection reduced the amount of virus in the ganglia and spinal cord. Acute neurological infection was not detected following transfer of protective anti-gp-D neutralizing antibody (LP2) in combination with removal of infected pinna. These data suggest that continuous seeding of virus occurs in related ganglia via the axonal route from infected ear pinna. It appears that local T-cell-mediated immune mechanisms are involved in maintenance of latency.