SIMULTANEOUS IDENTIFICATION OF 2 POPULATIONS OF SYMPATHETIC PREGANGLIONIC NEURONS USING RECOMBINANT HERPES-SIMPLEX VIRUS TYPE-1 EXPRESSING DIFFERENT REPORTER GENES

We generated neurotropic herpes simplex type 1 viruses expressing huma n placental alkaline phosphatase and studied the utility of this enzym e as a marker of infected neurons. The neurotropism of these viruses w as assessed by their ability to infect sympathetic preganglionic neuro ns after adrenal injection in hamsters. The transneuronal transfer of these viruses was examined by their ability to cross the peripheral sy napse from the kidney to renal preganglionic neurons or to cross the c entral synapse from the adrenal gland to the medulla oblongata. Finall y, we injected an alkaline phosphatase-expressing herpes simplex virus into the adrenal gland and a beta-galactosidase-expressing herpes sim plex virus (US5gal) into the muscular wail of the small intestine to l abel two neural circuits in one animal and to assess the feasibility o f a dual-virus labelling system. The alkaline phosphatase gene was ins erted into the glycoprotein J locus or the virus-induced host shut-off locus in the herpes simplex genome to create viruses which replicate (gJHAP HSV or vhsHAP HSV) or into the thymidine kinase locus to genera te a virus that does not replicate in neurons in vivo (TK(-)HAP HSV). Each of the three viruses was retrogradely transported from the adrena l gland of hamsters to sympathetic preganglionic neurons, suggesting t hat the neurotropism of these viruses was maintained. gJHAP HSV travel led transneuronally from the kidney to sympathorenal preganglionic neu rons and from the adrenal gland to neurons in the rostral ventrolatera l medulla. Neuronal infection with alkaline phosphatase-expressing vir us could be identified using histochemistry but detailed morphology of these neurons was not revealed. However, staining by anti-herpes simp lex virus immunoperoxidase demonstrated that they had normal morpholog y. Identification of two distinct neural circuits in one animal was ac hieved with our dual-virus labelling system. The nonreplicating TK-HAP HSV was used in combination with US5gal to identify intestinal and ad renal sympathetic preganglionic neurons. The beta-galactosidase-expres sing intestinal neurons were labelled bilaterally in the nucleus inter mediolateralis, pars principalis, and alkaline phosphatase-expressing adrenal neurons were found ipsilaterally. Some clusters of sympathetic preganglionic neurons in the nucleus intermediolateralis. pars princi palis contained mostly intestinal sympathetic preganglionic neurons an d a few adrenal sympathetic preganglionic neurons. In other areas, the opposite pattern occurred. About 3-7% of the labelled sympathetic pre ganglionic neurons were double-labelled by both markers. The distinct and crisp morphology and dendritic processes of neurons stained by bet a-galactosidase histochemistry contrasted with the partial staining of neurons by alkaline phosphatase. revealing beta-galactosidase as a be tter marker of infected neurons. In conclusion, alkaline phosphatase-e xpressing herpes simplex viruses are yet neurotropic after insertion o f this marker enzyme into any of three different loci of the herpes si mplex genome. One replicating alkaline phosphatase-expressing virus tr avelled transneuronally. These alkaline phosphatase-expressing herpes simplex virus can be used together with beta-galactosidase-expressing herpes simplex viruses to determine the target specificity of sympathe tic preganglionic neurons controlling visceral organs or can be used t o express two different recombinant genes in two targeted neuronal pop ulations. This study suggests that sympathetic preganglionic neurons c ontrolling the intestine and adrenal gland are almost completely disti nct. (C) 1997 IBRO. Published by Elsevier Science Ltd.